BALTIC FORESTRY

2016, Vol. 22, No. 1 (42) ISSN 2029-9230 1 BALTIC FORESTRY EDITORIAL BOARD

Lithuanian Academy of Sciences

Institute of Forestry, Lithuanian Research Centre fot Agriculture and Forestry

Aleksandras Stulginskis University

Latvian State Forest Research Institute “Silava”

Latvian University of Agriculture

Estonian University of Life Sciences

EDITORS

Editor-in-Chief: Alfas Pliūra, Prof. Dr. Hab. Proc. (Lithuania; [email protected])

Associated Editors: Agnis Šmits, Dr. (Latvia; [email protected]) Kaljo Voolma, Dr. (Estonia; [email protected])

EDITORIAL ADVISORY BOARD

Marius Aleinikovas, Dr. (Wood Science, Biomass Production), Institute of Forestry, Lithuanian Research Centre for Agriculture and Forestry, Girionys, Lithuania Olgirda Belova, Dr. (Wildlife Conservation and Management, Forest Protection), Institute of Forestry, Lithuanian Research Centre for Agriculture and Forestry, Girionys, Lithuania Gediminas Brazaitis, Prof. Dr. (Silviculture, Biodiversity Conservation, Wildlife Management), Aleksandras Stulginskis University, Akademija, Lithuania Vilis Brukas, Assoc. Prof., Dr. (Forest Policy, Socio-Economics), Swedish University of Agricultural Sciences (SLU), Alnarp, Swe- den Maris Daugavietis, Prof. Dr. (Forest Products, Silviculture), Latvian State Forest Research Institute “Silava”, Salaspils, Latvia Dorota Dobrowolska, Assoc. Prof. Dr. Hab.(Forest Regeneration, Forest Ecology), Forest Research Institute (IBL), Sękocin Stary, Poland Dagnis Dubrovskis, Dr. silv. (Forestry Production, Forest Utilization), Latvian University of Agriculture, Jelgava, Latvia Talis Gaitnieks, Dr. (Forest Soils, Silviculture, Phytopathology and Mycology), Latvian State Forest Research Institute “Silava”, Salaspils, Latvia Aris Jansons, Dr. (Forest Tree Breeding, Forest Genetics, Forest Plantations), Latvian State Forest Research Institute “Silava”, Salaspils, Latvia Paavo Kaimre, Assoc. Prof. Dr. (Forest Economics; Forest Policy Analysis), Estonian University of Life Sciences, Tartu, Estonia Leonardas Kairiūkštis, Prof. Dr. Hab. (Forest Ecology, Dendrochronology, Forestry, Silviculture), Institute of Forestry, Lithuanian Research Centre for Agriculture and Forestry; Lithuanian Academy of Sciences, Lithuania Mait Lang, Dr. (Remote Sensing Technology, GIS), Estonian University of Life Sciences, Tartu, Estonia Zane Lībiete, Dr. (Silviculture, Forest Ecology, Forest Resources ), Latvian State Forest Research Institute “Silava”, Salaspils, Latvia Lars Lönnstedt, Professor (Forest Economics, Forest Products, Forest Policy), Swedish University of Agricultural Sciences (SLU), Uppsala, Sweden Vitas Marozas, Prof. Dr. (Forest Botany, Forest Ecology, Biodiversity Conservation), Aleksandras Stulginskis University, Akade- mija, Lithuania Marek Metslaid, Dr. (Forest Ecology), Estonian University of Life Sciences, Tartu, Estonia Gintautas Mozgeris, Prof., Dr. (Forest Inventory and Management Planning), Aleksandras Stulginskis University, Akademija, Kau- nas reg., Lithuania Peeter Muiste, Prof. Dr. Tech. Sc. (Forest Operations, Forest Products), Estonian University of Life Sciences, Tartu, Estonia Edmundas Petrauskas, Assoc. Prof. Dr. (Forest Management, Forest Economy, Assessment of Forest Resources, Forest Growth and Yield, Forest Products, Forest Logistics), Aleksandras Stulginskis University, Akademija, Lithuania Alfas Pliūra, Prof. Dr. Hab. Proc. (Forest Genetics, Silviculture), Institute of Forestry, Lithuanian Research Centre for Agriculture and Forestry, Girionys, Lithuania Inga Straupe, Prof. Dr. (Forest Botany), Latvian University of Agriculture, Jelgava, Latvia Agnis Šmits, Dr. (Forest Entomology), Latvian State Forest Research Institute “Silava”, Salaspils, Latvia Hardi Tullus, Prof. Dr. Biol.Sc. (Silviculture, Biomass Production), Estonian University of Life Sciences, Tartu, Estonia Henn Tuherm, Prof. Dr. Hab. (Forest Policy; Forest Products), Latvian University of Agriculture, Jelgava, Latvia Rimvydas Vasaitis, Assoc. Prof. Dr. Hab. (Forest Mycology and Pathology), Swedish University of Agricultural Sciences (SLU), Uppsala, Sweden Kaljo Voolma, Assoc. Prof. Dr. Biol. Sc. (Forest Entomology, Forest Health Protection), Estonian University of Life Sciences, Tartu, Estonia

2016, Vol. 22, No. 1 (42) ISSN 2029-9230 2 BALTIC FORESTRY CONTENTS

CONTENTS

Burneviča, N., Jansons, Ā., Zaļuma, A., Kļaviņa, D., Jansons, J. and Gaitnieks, T. The Journal is abstracted/index in FUNGI INHABITING BARK STRIPPING WOUNDS MADE BY LARGE GAME ON STEMS OF PICEA ABIES (L.) KARST. IN LATVIA 2 CAB Abstracts Popowska-Nowak, E., Skrzecz, I., Tumialis, D., Pezowicz, E., Samborska, I. and Góral, K. Forest Sciense Database ENTOMOPATHOGENIC FUNGI IN THE SOILS OF FOREST PLANTATIONS: TOWARDS THE CONTROL OF LARGE PINE WEEVIL, HYLOBIUS ABIETIS 8 Environmental Sciense Database Kļaviņa, D., Menkis, A., Gaitnieks, T., Pennanen, T., Lazdiņš, A., Velmala, S. and Vasaitis, R. Soil Sciense Database LOW IMPACT OF STUMP REMOVAL ON MYCORRHIZATION AND GROWTH OF REPLANTED PICEA ABIES: Agroforestry Abstracts DATA FROM THREE TYPES OF HEMIBOREAL FOREST 16 Forestry Abstracts Kļaviņa, D., Muižnieks, I., Gaitnieks, T., Nikolajeva, V., Lazdiņa, D., Lazdiņš, A., Bārdule, A. and Menkis, A. Plant Protection Database FUNGAL COMMUNITIES IN ROOTS OF SCOTS PINE AND NORWAY SPRUCE SAPLINGS GROWN FOR 10 YEARS Review of Agricultural Entomology ON PEAT SOILS FERTILIZED WITH WOOD ASH 25 Review of Plant Pathology Leito, A., Leivits, M., Leivits, A., Raet, J., Ward, R., Ott, I., Tullus, H., Rosenvald, R., Kimmel, K. and Sepp, K. NISC SA Database BLACK-HEADED GULL (LARUS RIDIBUNDUS L.) AS A KEYSTONE SPECIES IN THE LAKE BIRD COMMUNITY IN PRIMARY FOREST-MIRE-LAKE ECOSYSTEM 34 SCOPUS Wróbel, M., Boczoń, A., Gawryś, R., Kowalska, A. and Krysztofiak-Kaniewska, A. Zoological Record, THE EFFECT OF BEAVER ACTIVITY ON ARTIFICIAL IMPOUNDMENT ON THE BRASZCZA RIVER Thomson Reuters Journal Citation IN THE BIAŁOWIEŻA PRIMEVAL FOREST 46 Reports/Science Edition (since 2007) Fescenko, A. , Lukins, M. and Fescenko, I. Science Citation Index Expanded VALIDATION OF MEDIUM-SCALE HISTORICAL MAPS OF SOUTHERN LATVIA FOR EVALUATION OF IMPACT (SciSearch®) OF CONTINUOUS FOREST COVER ON THE PRESENT-DAY MEAN STAND AREA AND TREE SPECIES RICHNESS 51 Ciupa, T., Suligowski, R. and Wałek, G. USE OF GIS-SUPPORTED COMPARATIVE CARTOGRAPHY AND HISTORICAL MAPS IN LONG-TERM FOREST COVER CHANGES ANALYSIS IN THE HOLY CROSS MOUNTAINS (POLAND) 63 Established in 1995 Jiang, L., Jiang, B., Shen, Z., Chen Sh., Qi, Zh., Chang, J., Mantri, N. and Lu, H. CHLOROPHYLL FLUORESCENCE: A NON-DESTRUCTIVE AND RAPID TOOL TO SELECT CHINESE FIR CLONES Semi-annual journal BEST ADAPTED TO A PARTICULAR REGION 74 BALT FOR Lasota, J., Błońska, E. and Zwydak, M. RELATIONS BETWEEN SITE CHARACTERISTICS AND SPRUCE STAND PRODUCTIVITY 81 Issued by the Institute of Forestry Järvis, J., Ivask, M., Nei, L., Kuu, A. and Luud, A. LAMMC, Liepu str. 1 EFFECT OF GREEN WASTE COMPOST APPLICATION ON AFFORESTATION SUCCESS 90 LT-53101 Girionys, Kaunas district, Hytönen, J. Lithuania WOOD ASH FERTILISATION INCREASES BIOMASS PRODUCTION AND IMPROVES NUTRIENT CONCENTRATIONS IN BIRCHES AND WILLOWS ON TWO CUTAWAY PEATS 98 Tel.: (+370 37) 547221 Magagnotti, N., Spinelli, R., Francesco, F. De and Lombardini, C. Fax: (+370 37) 547446 A VERSATILE TERRAIN AND ROADSIDE CHIPPER FOR ENERGY WOOD PRODUCTION IN PLANTATION FORESTRY 107 e-mail: [email protected] Laitila, J., Niemistö, P and Väätäinen, K. Internet: PRODUCTIVITY OF MULTI-TREE CUTTING IN THINNINGS AND CLEAR CUTTINGS OF YOUNG DOWNY BIRCH http://www.balticforestry.mi.lt/bf/ (BETULA PUBESCENS) DOMINATED STANDS IN THE INTEGRATED HARVESTING OF PULPWOOD AND ENERGY WOOD 116 Esen, R., Kurt, Ş. and Özcan, C. Designed by Publishing Company COMPRESSION STRENGTH PERPENDICULAR TO GRAIN CHARACTERISTICS OF IMPREGNATED LAMINATED VENEER LUMBERS EXPOSED TO SEA WATER 132 “LUTUTĖ” Eroğlu, H., Sariyildiz, T., Küçük, M. and Sancal, E. 9-ojo Forto str. 32, LT-48196 THE EFFECTS OF DIFFERENT LOGGING TECHNIQUES ON THE PHYSICAL AND CHEMICAL CHARACTERISTICS Kaunas, Lithuania OF FOREST SOIL 139 Tel.: (+370 37) 223072 Stöd, R., Verkasalo, E. and Heinonen, J. E-mail: [email protected] QUALITY AND BENDING PROPERTIES OF SAWN TIMBER FROM COMMERCIAL THINNINGS OF SCOTS PINE Internet: (PINUS SYLVESTRIS L.) 148 www.lutute.lt Irdla, M., Padari, A. and Muiste, P. THE ALTERNATIVES OF TRANSPORT OF WOOD CHIPS IN ESTONIAN CONDITIONS: A CASE STUDY 163 Layout Kaliniewicz, Z., Tylek, P., Anders, A., Markowski, P., Rawa, T., Ołdakowski, M. and Wąsowski, L. AN ANALYSIS OF THE PHYSICAL PROPERTIES OF SEEDS OF SELECTED DECIDUOUS TREE SPECIES 169 Mindaugas Kirstukas Lukason, O., Lukason, T. and Varblane, U. FIRM FAILURE CAUSES IN THE FOREST SECTOR: AN ANALYSIS OF BANKRUPTED ESTONIAN FIRMS 175 Printed sheets 24 Makrickienė, E., Drössler, L. and Brazaitis, G. Circulation 200 DEVELOPMENT AND TRAITS OF WOLF TREES IN SCOTS PINE (PINUS SYLVESTRIS L.): A LITERATURE REVIEW 181

2016, Vol. 22, No. 1 (42) ISSN 2029-9230 31 BALTIC FORESTRY FUNGI INHABITING BARK STRIPPING WOUNDS MADE BY LARGE GAME /.../ N. BURNEVIČA ET AL. ARTICLES Fungi Inhabiting Bark Stripping Wounds Made by Large Game on Stems of Picea abies (L.) Karst. in Latvia

NATĀLIJA BURNEVIČA, ĀRIS JANSONS, ASTRA ZAĻUMA, DĀRTA KĻAVIŅA, JURĢIS JANSONS AND TĀLIS GAITNIEKS Latvian State Forest Research Institute “Silava”, Rigas 111, Salaspils, LV-2169, Latvia *Corresponding author: e-mail: [email protected]; Fax: +37167901359

Burneviča, N., Jansons, Ā., Zaļuma, A., Kļaviņa, D., Jansons, J. and Gaitnieks, T. 2016. Fungi Inhabiting Bark Stripping Wounds Made by Large Game on Stems of Picea abies (L.) Karst. in Latvia. Baltic Forestry 22(1): 2-7.

Abstract

In the last decade the populations of large game as moose and red deer have increased in Latvia, and the risk of damage to for- est stands has increased simultaneously. The aim of this study was to evaluate the extent of bark stripping wounds, decay incidence and associated fungi in 30-year-old Picea abies stems damaged by big game. In total, 90 trees were evaluated and 157 bark stripping wounds of different age (1-10 years) were measured. From each wound margin one wood sample was collected for evaluation of presence of decay and subsequent fungal isolation. Decay was found in 13-50% of investigated wounded P. abies trees depending on study site (mean 26.7%). All injuries were open wounds. Area of exposed sapwood was 7 – 6142 cm2. The most commonly iso- lated fungi were ascomycetes Neonectria fuckeliana, Sarea difformis and Phialocephala sp., and basidiomycetes Cylindrobasidium evolvens and Amylostereum areolatum.

Key words: Picea abies, bark stripping, decay fungi.

Introduction by timber harvesting machines are mostly on tree roots and butt (Isomäki and Kallio 1974, Vasiliauskas 2001). Norway spruce (Picea abies (L.) Karst.) is one of the The area of bark stripping wounds is very variable, from most economically important conifer species in Latvia. 2 to 4,815 cm2 (Vasiliauskas et al. 1996, Čermák and However, root and stem rot caused by various species of Strejček 2007). Vasaitis et al. (2012) showed that wounds fungi can lead to considerable losses in timber production on P. abies stems greater then 5 cm width are unlikely to (Arhipova et al. 2011). The most important fungal species be completely occluded and are more prone to infection causing stem decay in P. abies stands are Heterobasidion by fungi causing stem decay. The most common decay- annosum s.l. and Stereum sanguinolentum (Korhonen and causing fungus is Stereum sanguinolentum, which can Piri 2003, Arhipova et al. 2011). Several studies have cause extensive stem rot resulting not only in reduced tim- shown that stem wounds are an important route for tree ber quality, but increased vulnerability to wind or snow infection with decay-causing fungi (Vasiliauskas et al. damage (Randveer and Heikkilä 1996, Vasiliauskas et al. 1996, 2001, Vasiliauskas 2001). 1996, Čermák and Strejček 2007, Vasaitis 2013). Only In the last decades, the populations of large game as one study on fungi colonizing bark stripping wounds has moose (Alces alces L.) and red deer (Cervus elaphus L.) been conducted in Latvia (McLaughlin and Šica 1996). have increased in Latvia (Baumanis 2013). The risk of The aim of this study was to evaluate the wounding pat- damage to forest stands has increased simultaneously. tern caused by bark stripping on stems of P. abies and to One type of damages is bark stripping that can reduce val- identify the associated fungi. ue of final wood harvest (Gill 1992, Vospernik 2006, An- dersone-Lilley et al. 2010). The most severe damage usu- Materials and methods ally occurs in trees with DBH (diameter at breast height) 5-20 cm and age 4 to 50 years (Gill 1992, Vasiliauskas Field work et al. 1996, Vospernik 2006, Čermák and Strejček 2007, The study was conducted in Latvia in three 32-34-year- Månsson and Jarnemo 2013). Bark stripping wounds are old P. abies monocultures (Figure 1), all growing on min- usually situated at a height of 1-2 m, while injuries caused eral podzolic soil: two (Šķēde 1 and 2) in an Oxalidosa and

2016, Vol. 22, No. 1 (42) ISSN 2029-9230 24 BALTIC FORESTRY FUNGI INHABITING BARK STRIPPING WOUNDS MADE BY LARGE GAME /.../ N. BURNEVIČA ET AL. one (Kalsnava) in a Hylocomiosa forest type, according to all pure cultures were examined under a microscope and the Latvian classification system (Zālītis and Jansons 2013). grouped into mycelial morphotypes according to micro- Experimental design was similar to that of related work scopic features of mycelium. on Pinus contorta (Arhipova et al. 2015). In each study site, One to two representatives of each distinct mycelial 30 living P. abies trees with bark stripping injuries were se- morphotype were subjected to molecular identification fol- lected by choosing the most adjacent wounded tree to the lowing procedures from Arhipova et al. (2011). In brief, previous measured one. Each tree was numbered and its di- DNA extraction and PCR amplification were made accord- ameter at breast height (DBH) measured. The number of in- ing to established protocols (Kåren et al. 1997). The ready dividual injuries per stem (wounds separated by sound bark) PCR products were purified using FastAP Thermosensitive was recorded for each selected tree. For each of 157 recorded Alcaline Phosphatase and Escherichia coli exonuclease I injuries, maximum length and width, as well as heights of (Thermo Scientific) and sent to Macrogen Europe (Amster- the lowest and highest wound margins were measured. To dam, the Netherlands) for further Sanger sequencing. Se- estimate wound area, configuration of small wounds (length quencing was done in one direction using universal primer < 60 cm) was drawn by a waterproof marker on a transpar- Its4 for every specimen. All sequences were manually ed- ent paper and in the laboratory area was measured using a ited using the Bioedit software (version 7.0.9.0). BLAST Tamaya Digital Planimeter “Planix 10-S”. For wounds with searches were performed using the GenBank sequence data- length more than 0.6 m, the area was calculated as an ellipse base (http://blast.ncbi.nlm.nih.gov/Blast.cgi). For delimiting using measured maximum length and width. fungal taxon (presumed species), the Internal Transcribed From each of 157 wounds a single wood sample (10- Spacer (ITS) sequence homology was set at 98-100 %. For 16 cm long bore core) was taken using an increment borer. delimiting at genus level, the ITS sequence homology was Depending on wound height and accessibility, the sample set at 94-97 %. All obtained ITS sequences were deposited was taken either 1 cm above or below the injury. Wood in GenBank (accession numbers KR072493-KR072507). samples were assessed for the presence/absence of decay or discolouration, individually placed in sterile plastic tubes, Results and transported to the laboratory for further fungal isolation. Standard statistics (means, standard deviation) of Mean parameters of surveyed trees and bark stripping measurements of wounds and discolourations were calcu- wounds are presented in Table 1. Stem DBH of examined lated (Fowler et al. 1998). trees varied from 9 to 29.5 cm. The maximum number of wounds per stem was four. All 157 injuries represented open Isolation and identification of fungi wounds. Area of exposed sapwood was in the range from In the laboratory, the bore core was split into two 7 to 6.142 cm2 of sapwood (589 ± 1.173 cm2 on average). pieces, each piece flame-sterilized and individually placed Wound age varied from 1 to 10 years, and on individual in 9-cm diameter plastic Petri dishes on malt agar media stems wound age varied between 1 and 6 years. The lowest

(15 g malt extract, 12 g agar, 1l H2O) (300 Petri dishes in wound height was (0 - 0.4 m) at root collar and the highest total). Petri dishes were incubated at room temperature one was 199 cm. However, typically the lowest wound mar- and inspected twice a week for fungal growth; all emerg- gin was recorded at stem height 80 – 1.4 m (102 wounds or ing mycelia were subcultured on individual Petri dishes 65 %). Decay was found in 13-50 % of the selected P. abies and grown as pure cultures. After 3-4 weeks of growth, trees depending on study site (26.7 % on average).

Table 1. Average parameters (mean ± SD) of analyzed Picea abies trees (n=90) and bark stripping wounds (n = 157)

Parameters / site Kalsnava Šķēde1 Šķēde 2 All Stem diameter at breast height (cm) 17 ± 4 17 ± 5 19 ± 5 18 ± 5

Wounds per stem (no.) 2.4 ± 0.9 1.4 ± 0.6 1.5 ± 0.6 1.7 ± 0.8

Wood discolouration (% of stems) 50.0 13.3 20.0 26.7

Wound width (cm) 9 ± 5 10 ± 5 11 ± 5 10 ± 5

Wound length (cm) 28± 20 38 ± 21 37 ± 19 33 ± 20

Height of lower wound margin (cm) 97 ± 32 100 ± 30 62 ± 23 88 ± 33

Height of upper wound margin (cm) 125 ± 27 139 ± 23 98 ± 24 121 ± 30

Exposed sapwood per wound (cm2) 591 ± 1206 541 ± 1095 631± 1211 589 ± 1173

Time since damage (years) 5 ± 2 5 ± 1 6 ± 2 5 ± 2

2016, Vol. 22, No. 1 (42) ISSN 2029-9230 53 BALTIC FORESTRY FUNGI INHABITING BARK STRIPPING WOUNDS MADE BY LARGE GAME /.../ N. BURNEVIČA ET AL.

Of 157 wood samples, 92 (59 %) resulted in fungal of all wounds) and Phialocephala sp. (13.4 % of all growth and yielded 160 fungal isolates representing 25 wounds). Eight species of basidiomycetes were occasion- fungal taxa (Table 2). The most common fungi isolated ally isolated. The most common species of basidiomycetes from bark stripping wounds were ascomycetes Neonectria were Cylindrobasidium evolvens (10.8 % of all wounds) fuckeliana (24.8 % of all wounds), Sarea difformis (13.4 % and Amylostereum areolatum (3.8 % of all wounds). Table 2. Fungi isolated from bark stripping wounds of Picea abies in Latvia

Frequency of occurrence, % GenBank in trees with in trees without Fungal taxa accession in wounds in trees, discolouration discolouration no.* (N=157) (N=90) (N=24) (N=67) Basidiomycetes

Amylostereum areolatum (Chaillet ex Fr.) Boidin KR072496 3.8 25.0 - 6.7

Climacocystis borealis (Fr.) Kotl. & Pouzar KR072506 0.6 4.2 - 1.1

Cylindrobasidium evolvens (Fr.) Jülich KR072493 10.8 25.0 13.4 16.7

Gymnopilus penetrans (Fr.) Murrill KR072502 2.5 12.5 1.5 4.4

Heterobasidion parviporum Niemelä & Korhonen - 0.6 4.2 - 1.1 KR072503 - 1.1 Peniophorella praetermissa (Karst.) Larss 0.6 4.2

Pholiota spumosa (Fr.) Singer KR072505 0.6 4.2 - 1.1

Stereum sanguinolentum (Alb. & Schwein.) Fr KR072495 0.6 4.2 - 1.1

All Basidiomycetes - 4.7 11.8 6.8 7.8

Ascomycetes and anamorphic fungi

Ascocoryne cylichnium (Tul.) Korf - 13.4 29.2 11.9 16.7

Aspergillus sp. - 0.6 - 1.5 1.1

Aureobasidium pullulans (de Bary) G. Arnaud - 1.3 4.2 - 1.1

Eutypa sp. K7 KR072494 5.1 20.8 4.5 8.9

Neobulgaria sp. K35 KR072504 0.6 4.2 - 1.1 4.2 Hypocrea pachybasioides Yoshim - 1.3 1.5 2.2

Hormonema dematioides Lagerb. & Melin - 0.6 - 1.5 1.1

Lachnum sp. K48 KR072507 0.6 - 1.5 1.1

Neonectria fuckeliana (C. Booth) Castl. & Rossman - 24.8 45.8 17.9 25.6

Ophiostoma piceae (Münch) Syd. & P. Syd - 0.6 4.2 - 1.1

Grosmannia piceaperda (Rumbold) Goid KR072497 0.6 4.2 - 1.1

Penicillium sp. - 1.9 - 4.5 3.3

Pezicula eucrita (Karst.) Karst. KR072499 1.3 - 3.0 2.2

Phaeomoniella effusa Damm & Crous KR072500 1.3 4.2 1.5 2.2

Phialocephala sp. K19 KR072498 13.4 33.3 13.4 18.9

Sarea difformis (Fr.) Fr KR072501 13.4 25.0 19.4 21.1

All Ascomycetes and anamorphic fungi - 55.6 82.4 56.2 61.1

Zygomycetes

Umbelopsis isabellina (Oudem.) W. Gams - 0.6 4.2 - 1.1

All Zygomycetes - 8.8 29.4 8.2 12.2

2016, Vol. 22, No. 1 (42) ISSN 2029-9230 46 BALTIC FORESTRY FUNGI INHABITING BARK STRIPPING WOUNDS MADE BY LARGE GAME /.../ N. BURNEVIČA ET AL.

Discussion and conclusions 1996, Vasiliauskas et al. 1996). Climacocystis borealis typically infects wounds on roots and the lower part of A large proportion (26.7 %) of young spruce (32-34 the trunk, causing root and butt rot of spruce in old grown years) examined in this study had decay and discoloura- forests (Hallaksela 1984, Solheim 2006), but we isolated tion. Several basidiomycetes commonly isolated from de- it from a wound at height 70 cm. In Scandinavia this fun- cayed trees usually use open stem wounds as infection gus is an indicator species of natural forest (Nitare 2000). courts. Amylostereum areolatum, Stereum sanguinolen- The most common fungus isolated from bark strip- tum and Heterobasidion parviporum can cause stem de- ping wounds was ascomycete Neonectria fuckeliana. cay, which can significantly decrease wood quality. For This species is a common wound invader of several tree example, in a ten-year period after injury, average ver- species (Vasiliauskas et al. 1996, Vasiliauskas and Sten- tical spread of decay due to A. areolatum was observed lid 1998b), but it is not associated with decay and can be to be 2.8 m, with decay affecting 30-40% of total stem isolated also from sound-looking wood (Roll-Hansen and cross area (Vasiliauskas 1999). This fungus is one of few Roll-Hansen 1979, Huse 1981). However, this fungus is species of basidiomycetes that uses insects for transmis- a weak pathogen and can cause bark necrosis of spruce sion, and usually is introduced to fresh bark wounds (Philips and Burdekin 1982). Neonectria fuckeliana has by siricid woodwasps during their oviposition (Vasaitis been reported as a significant pathogen causing Nectria 2013). Stereum sanguinolentum is the most important flute canker in Pinus radiata plantations in New Zealand decay-causing fungus colonizing bark stripping wounds (Dick and Crane 2009). An experiment established in of different origin (Roll-Hansen and Roll-Hansen 1980, Latvia in 2011 showed that N. fuckeliana can cause can- McLaughlin and Šica 1996, Vasiliauskas et al. 1996, kers on spruce bark three years after artificial inoculation Čermák and Strejček 2007). Rate of vertical spread of (Brūna, unpublished data). decay by S. sanguinolentum was observed to be between As spruce trees are vulnerable to bark stripping from 13.3 and 19.5 cm per year (Čermák and Strejček 2007). the age of 4 years up to 50 years (Gill 1992 and references Seven years after wounding, the decay column in spruce therein, Vasiliauskas et al. 1996, Gill et al. 2000, Čermák stems can reach 1-4 m height and can affect 3 - 84 % of and Strejček 2007), subsequent damage after bark strip- the stem cross-section (Vasiliauskas and Stenlid 1998a). ping will increase with time. Fresh bark stripping wounds Vasiliauskas et al. (1996) found a positive correlation were observed on some of the sampled trees in current between wound age and frequency of wounds infected study, which means that the number of trees containing by S. sanguino­lentum. In Norway, 16% of stem wounds stem decay can be expected to increase up to final har- were found to be infected 5-7 years after wounding and vest. The extent of stem decay and frequency of infection 39 % of trees with 15-20-years-old wounding scars were is strongly correlated with stand age (Vasiliauskas et al. infected by S. sanguinolentum (Solheim 2006). The low 1996, Čermák and Strejček 2007, Gaitnieks et al. 2008). incidence of this fungus in the current study could be as- In a study conducted in the Czech Republic (Čermák and sociated with rather young wound age (the mean is five Strejček 2007), 44% of spruce trees were damaged by years), and the infection incidence might be expected to red deer and stem decay was observed in 68 % of dam- increase with time. The method used for detection of de- aged trees. Bark stripping damage in young conifer stands cay was not very precise, and approximately 30 % of de- (including bark stripping and browsing damages) is posi- cayed trees might remain unnoticed, especially in cases of tively correlated with deer and moose population density lateral rot (Stenlid and Wästerlund 1986). Heterobasidion (Gill 1992 and references therein, Kiffner et al. 2008, parviporum, which usually infects trees through root con- Baumanis 2013). tacts, is able to infect open wounds, especially on roots In comparison with the exotic tree species Pinus or close to tree base (Redfern and Stenlid 1998). In the contorta Douglas ex Loudon, which also is susceptible to current study H. parviporum was isolated from a wound bark stripping by deer and moose (Arhipova et al. 2015), with the lowest margin at 18 cm from root collar. How- our data showed that damage on P. abies trees of the same ever, stem and root wounds are not as important infection size and age can be much more severe. The maximum area courts for this pathogen as freshly cut stumps (Redfern of exposed wood in the current study was considerably and Stenlid 1998 and references therein, Rönnberg 2000). higher than in studies made by other authors (Vasiliaus- Nevertheless, wound infection can play a significant role kas et al. 1996, Čermák and Strejček 2007), which might in unmanaged forest, where stumps are absent (Garbelotto be because spruce pure cultures are more severely dam- and Gonthier 2013). Cylindrobasidium evolvens, the most aged than mixed stands (Gill 1992 and references therein, abundant wound colonizing basidiomycete in the current Baumanis 2013). The results of this study repeatedly em- study, is usually associated with large recent wounds and phasize risks posed to forest stands in areas, where the without considerable stem decay (McLaughlin and Šica populations of the big game are disproportionally large.

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Estimating of frequency Gill, R.M.A. 1992. A review of damage by mammals in north of stem rot in Picea abies using an increment borer. Scan- temperate forests: 1. Deer. Forestry 65(2): 145-169. DOI: dinavian Journal of Forest Research 1(1-4): 303-308. 10.1093/forestry/65.2.145. DOI: 10.1080/02827588609382421. Gill, R., Webber, J. and Peace, A. 2000. The economic implica- Vasaitis, R. 2013. Heart rots, sap rots and canker rots. In Gonthier, tions of deer damage. Final Report for The Deer Commission P., Nicolotti, G. (Eds.) Infectious Forest Diseases. CAB Inter- for Scotland. Wrecclesham, Forest Research Agency. national, Wallington, UK, p. 197-229. Hallaksela, A.M. 1984. Causal agents of butt rot in Norway spruce Vasaitis, R., Lygis, V., Vasiliauskaite, I. and Vasiliauskas, A. 2012. Picea abies in southern Finland. Silva Fennica 18(3): 237- Wound occlusion and decay in Picea abies stems. European 243. DOI: 10.14214/sf.a15395. Journal of Forest Research 131: 1211-1216. DOI: 10.1007/ Huse, K.J. 1981. The distribution of fungi in sound-looking stems s10342-011-0592-3. of Picea abies in Norway. European Journal of Forest Pathol- Vasiliauskas, R. 1999. Spread of Amylostereum areolatum and A. ogy 11(1-2): 1-6. DOI: 10.1111/j.1439-0329.1981.tb00063.x. chailletii decay in living stems of Picea abies. Forestry 72(2): Isomäki, A. and Kallio, T. 1974. Consequences of injury caused by 95-102. DOI: 10.1093/forestry/72.2.95. timber harvesting machines on the growth and decay of spruce Vasiliauskas, R. 2001. Damage to trees due to forestry operations (Picea abies (L.) Karst.). Acta Forestalia Fennica 136: 1-25. and its pathological significance in temperate forests.Forestry ISBN: 951-651-011-6. 74: 319-336. DOI: 10.1093/forestry/74.4.319. Kåren, O., Hogberg, N., Dahlberg, A., Jonsson, L. and Nylund, Vasiliauskas, R., Juska, E., Stenlid, J., and Vasiliauskas, A. 2001. J.-E. 1997. Inter- and intraspecific variation in the ITS region Clonal differences and relations between diameter growth, of rDNA of ectomycorrhizal fungi in Fennoscandia as detected stem cracks and fungi in 36-year-old clonal seed orchard of

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Norway spruce (Picea abies). Silvae Genetica 50: 227-233. and management 109(1-3): 119-126. DOI:10.1016/S0378- ISSN 0037-5349. 1127(98)00226-6. Vasiliauskas R., Stenlid J. and Johansson M. 1996. Fungi in bark Vospernic, S. 2006. Probability of bark stripping damage by red peeling wounds of Picea abies in central Sweden. European deer (Cervus elaphus) in Austria. Silva Fennica 40(4): 589- Journal of Forest Pathology 26: 285-296. DOI: 10.1111/ 601. ISSN: 0037-5330. j.1439-0329.1998.tb01192.x. Zālītis, P. and Jansons, J. 2013. Latvijas meža tipoloģija un Vasiliauskas, R. and Stenlid, J. 1998a. Spread of Stereum sanguin- tās sākotne [Latvian forest typology and its early stage]. olentum vegetative compatibility groups within a stand and Daugavpils Universitātes apgāds Saule, Daugavpils, 167 pp. within stems of Picea abies. Silva Fennica 32(4): 301-309. (in Latvian). ISSN: 0037-5330. Vasiliauskas, R. and Stenlid, J. 1998b. Fungi inhabiting stems of Received 03 July 2015 Picea abies in a managed stems of Lithuania. Forest Ecology Accepted 08 October 2015

2016, Vol. 22, No. 1 (42) ISSN 2029-9230 97 BALTIC FORESTRY ENTOMOPATHOGENIC FUNGI IN THE SOILS /.../ E. POPOWSKA-NOWAK ET AL. Entomopathogenic Fungi in the Soils of Forest Plantations: Towards the Control of Large Pine Weevil, Hylobius abietis

ELŻBIETA POPOWSKA-NOWAK1, IWONA SKRZECZ2*, DOROTA TUMIALIS3, ELŻBIETA PEZOWICZ3, IZABELA SAMBORSKA1 AND KATARZYNA GÓRAL4 1 Faculty of Biology and Environmental Sciences, University of Kardynal Stefan Wyszynski, Wojcickiego str. 1/3, 01-938 Warsaw, Poland 2 Forest Protection Department, Braci Lesnej str. 3, Sekocin Stary, 05-090-Raszyn, Poland 3Department of Animal Environment Biology, Warsaw University of Life Sciences, Ciszewskiego str. 8, 02-786 Warsaw, Poland 4 Department of Genetic and Animal Breeding, Warsaw University of Life Sciences, Ciszewskiego str. 8, 02-786 Warsaw, Poland * Corresponding author: e-mail: [email protected]; phone: +48 22 7150541; fax: +48 22 7150557

Popowska-Nowak, E., Skrzecz, I.*, Tumialis, D., Pezowicz, E., Samborska, I. and Góral, K. 2016. Entomopatho- genic Fungi in the Soils of Forest Plantations: Towards the Control of Large Pine Weevil, Hylobius abietis. Baltic Forestry 22(1): 8-15.

Abstract

The study was aimed at estimating species structure and density of entomopathogenic fungi in soils of forest plantations that are a natural habitat of the large pine weevil, Hylobius abietis L. Soil samples were collected in spring and autumn 2010 and 2011 in forest districts of northern, central and southern Poland. Fungi were isolated from soils with the trap insect method and on selective growing media. As a result, 5 species of entomopathogenic fungi were isolated: Beauveria bassiana, Isaria farinosa, Isaria fumosorosea, Metarhizium anisopliae and Verticillium lecanii, of which I. fumosorosea and M. anisopliae were isolated most frequently. The number of infected trap insects and the number of fungal colonies isolated on growing medium differed depending on the term and place of soil sampling. It seems that type of forest habitat might be the factor affecting species structure and the number of entomopathogenic fungi in forest plantations established on clear cuttings, where stumps of coniferous trees provide the place for development of the large pine weevil.

Key words: entomopathogenic fungi, forest plantation, Hylobius abietis, soil

Introduction Leptographium lundberii, Ophiostoma floccosum, O. pil- iferum, Sporothrix inflate(Jankowiak and Bilanski 2013). The large pine weevil Hylobius abietis L. is a spe- Protection of forest plantations against the large pine cies, whose beetles feed on seedlings of all coniferous tree weevil is still one of more important problems in forest species causing damage to bark, phloem and, to a less ex- management. To protect young forests against this species tent, needles. They may also damage deciduous trees, es- different methods are used in practice. To directly reduce pecially in mixed plantations (Wallertz et al. 2006, Thorpe the number of pine weevils, freshly cut and debarked co- and Day 2008, Gradinariu et al. 2012). Larvae of the in- nifer billets or various kinds of traps baited with alpha- sect are not harmful since they develop in roots of stumps pinen and ethanol are used. Chemical treatments consist that remain after falling the trees mainly the Scots pine in dipping the above-ground parts of seedlings before Pinus sylvestris L. and Norway spruce Picea abies (L.) planting or spraying them with contact insecticides after H. Karst. The large pine weevil is a vector responsible for planting have been most often form of forest protection transmitting of tree pathogens, e.g. spores of the fungus until recently (Glowacka et al. 1991). However, in Swe- Heterobasidium annosum (Fr.) Bref. causing root rot - one den for many years, the studies have been conducting on of the most important economic disease of forest trees using of various kinds of physical barriers assumed to the (Kadlec et al. 1992). Hylobius abietis may also contrib- stems of seedlings (Lindström et al. 1986, Eidmann et al. ute to the distribution of other phytopathogenic fungi like 1996, Petersson et al. 2004). As a result, a new method

2016, Vol. 22, No. 1 (42) ISSN 2029-9230 810 BALTIC FORESTRY ENTOMOPATHOGENIC FUNGI IN THE SOILS /.../ E. POPOWSKA-NOWAK ET AL. was developed, in which the stems of conifer seedlings genic fungi in the soils of forest plantations at various are covered with flexible sand coating (Conniflex) (Nor- time of growing season in different sites that are natural dlander et al. 2009). The use of Conniflex leads to a sig- habitats of the large pine weevil. nificant increase (more than 85 %) of young tree survival. An alternative to mechanical and chemical methods Materials and methods would be to use pathogenic microorganisms and parasit- oids, predatory insects and vertebrates as control factors Study sites were localised on 1 to 3-year-old clear reducing the number of harmful entomofauna are carried cuttings. In spring (the first half of May) and autumn (the out in many scientific institutions. In the case of the large second half of September) 3 soil samples were taken ev- pine weevil, the studies attempt to use entomopathogenic ery year with the Egner’s sampler (2.5 cm in diameter) to nematodes and fungi. In Europe such studies focussed the depth of 20 cm. Each soil sample consisted of 5 con- mainly on nematodes of the genera Steinernema and tents of the sampler (1 kg in total), which were mixed to Heterorhabditis (Brixey et al. 2006, Dillon et al. 2007, obtain a homogenous sample from each site. Soil was then Skrzecz et al. 2011, Tumialis et al. 2013). placed in foil bags and taken to the laboratory. Studies on the use of entomopathogenic fungi in lim- Studies were carried out in forest districts in north- iting the number of the large pine weevil were carried out ern, central and southern Poland. Each site was given a by Wegensteiner and Führer (1988), who analysed mor- symbol denoting its location in the country (N – north, tality of beetles infected by Beauveria bassiana (Bals.) C – centre, S – south) followed by a number (Figure 1). Vuill. in laboratory conditions. Similar tests were made Characteristics of study sites and their symbols are shown by Ansari and Butt (2012), who infected all growth stages in Table 1. Regardless of the samples, the air temperature of H. abietis with fungi: B. bassiana and two species of was similar, but spring rainfall was more than 2-fold high- the genus Metarhizium: M. robertsii (Metschn.) Sorokin er (Table 2). The weather data came from meteorological and M. brumneum Petch. Field tests of combined effect of stations of the State Forests located up to 30 km from ex- nematodes S. carpocapsae (Weiser) and Heterorhabditis perimental plots. Acidic podzolic soils were mainly pres- downesi (Stock, Griffin and Burnell), and fungi B. bassi- ent in the study areas and their pH ranged from 5.0 to 5.5. ana with Metarhizium anisopliae (Metschn.) Sorokin on In the laboratory, entomopathogenic fungi were iso- various growth stages of H. abietis were made in Ireland lated from soils with the method of trap insects using (Wiliams et al. 2013). larvae of the greater wax moth Galleria mellonella L. The most frequent entomopathogenic fungi in field (Zimmerman 1986). The larvae of this species are com- and forest soils of Poland are: B. bassiana, M. anisopliae, monly used in microbiology to isolate the entomopatho- Isaria farinosa (syn. Paecilomyces farinosus), Isaria fu- genic microorganisms and nematodes from the soils due mosorosea (syn. Paecilomyces fumosoroseus) and Verti- to high sensitivity to infections caused by pathogens. By cillium lecanii (Bajan and Kmitowa 1997). They belong this, the larvae die as a result of infections caused by the to the fungi imperfecti of the class Hyphomycetes and are fungal spores that are present in the soil sample. Larvae potentially most effective in the control of pest insects in of G. mellonella came from continuous laboratory rear- Poland (Balazy 2000). ing on bee wax in temperature 25 °C and the darkness. So far, there is little information on a possible use To isolate entomopathogenic fungi, each soil sample was of entomopathogenic fungi in controlling H. abietis. placed in 10 plastic containers of 250 cm-3, filled with Therefore, species composition of these pathogens in for- tested soil to ¾ height. Then, 10 of G. mellonella larvae est plantations, where stumps provide a basis for growth and young trees are food for the large pine weevil has not been analysed. Such studies may help isolate a strain of entomopathogenic fungus, whose pathogenic properties would be great enough to use it in biological preparations potentially applicable in the insect control. The aim of studies performed in 2010-2011 was to estimate species structure and density of entomopatho-

Figure 1. Location (geographical coordinates) of forest plantations, from which soil was sampled: N-1 (53°53’57.3”N, 20°47’37.5”E); N-2 (53°51’18.9”N, 20°49’06.2”E); C-1 (52°03’34.3”N, 21°23’09.7”E); C-2 (52°05’19.3”N, 21°17’15.2”E); C-3 (52°10’28.3”N, 21°46’29.9”E); C-4 (52°10’21.5”N, 21°32’48.3”E); S-1 (49°39’02.1”N, 19°17’33.2”E); S-2 (49°40’08.5”N, 19°04’11.9”E); S-3 (49°39’47.4”N, 19°04’28.8”E)

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Table 1. Characteristics of forest plantations, from which the soil samples were taken

Harvested stand: Symbol Area of clear Date of clear cut Forest habitat main species/age Date of reforestation of area cut (ha) establishment (years)

N-1 Fresh coniferous forest 3.20 P. sylvestris/105 February 2010 April 2010 Fresh mixed coniferous N-2 1.80 P. sylvestris/100 February 2006 April 2008 forest C-1 Fresh coniferous forest 1.36 P. sylvestris/95 September 2007 April 2009

C-2 Fresh coniferous forest 1.01 P. sylvestris/100 February 2008 April 2010

C-3 Fresh coniferous forest 2.50 P. sylvestris/107 February 2008 April 2010

C-4 Fresh coniferous forest 2.22 P. sylvestris/102 February 2009 April 2010 Mixed mountain S-1 1.50 P. sylvestris/90 September 2007 April 2008 coniferous forest S-2 Mixed mountain forest 2.50 P. abies/85 February 2008 April 2008

S-3 Mixed mountain forest 2.15 P. abies/90 September 2007 April 2008

Table 2. The average monthly air temperature and total rainfall in the months of sampling

Localization Rainfall Year Months Air temperature (0C) of experimental plots (mm)

North 12.72 56

May Center 12.61 48

South 10.94 93 2010 North 10.11 22

September Center 11.39 18

South 9.28 44

North 11.78 58

May Center 11.28 49

South 10.62 118 2011 North 11.50 9

September Center 11.56 2

South 10.48 17 in L3 stage were placed in each container. The tested soil dia with the surface methods (from 10-2 dilution of soil was not moistening in the containers. After 21 days of solution) and developed colony forming units (cfu) of rearing (temp. 25 °C, humidity 60%), dead insects were fungi were counted (Strasser et al. 1996). Fungi were de- transferred to Petri dishes lined with wet filter paper and termined to species as above. individuals covered with mycelium were counted. Then, The results were statistically processed with the IBM mycelia from insects were placed in Petri dishes filled SPSS Statistics 21 software. Non-parametric Kruskal- with Sabouraud Dextrose Agar (medium based on pep- Wallis test was used to compare the degree of infection tone, glucose and agar). Fungi from grown colonies were of test insects by particular fungi species and the number determined to species using keys by Samson et al. (1988) of isolated colonies in study sites. In case of finding dif- and Humber (2012). ferences, Mann-Whitney U test was applied at P < 0.05. To determine the number of entomopathogenic fungi in analysed samples, soil was distributed on selective me-

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Results three species infected fewer insects. Isaria farinosa was mainly isolated from soils of central and northern Poland. Five species of entomopathogenic fungi were iso- Most pathogenic isolate of this species, which infected lated in this study: B. bassiana, Isaria farinosa (Holmsk.) up to 10 % of insects, was from northern Poland (N-1). Fr., Isaria fumosorosea Wize, M. anisopliae (Metsch.) Beauveria bassiana was isolated from only a few sites in Sorok and Verticillium lecanii (Zimm.) (Figures 2, 3). northern (N-1), central (C-1 and C-4) and southern Poland and infected no more than 5 % of test insects. Verticillium lecanii was isolated from only one soil sample from cen- tral Poland (C-2) and infected only 1% of insects. In samples collected in autumn, the presence of above mentioned species was found in all sites of cen- tral Poland and only in single sites in the north and south of the country (Figure 3). Moreover, the fungi infected much fewer (up to 12 %) trap insects. Most insects (12 %) were infected by M. anisopliae isolated from soil sample taken exclusively in one site in southern Poland (S-3). Most frequently isolated were fungi from the genus Isaria (soils from central Poland and one site in the south of the country – S-3) recorded in 11 % (I. farinosa) and 4% (I. fumosorosea) of insects. Beauveria bassiana was isolated from only one site in northern Poland (N-1) and one in Figure 2. Percentage of insects infected by entomopathogenic southern Poland (S-3) and infected up to 5 % of insects. fungi isolated from soil in spring. *Statistically significant dif- The least frequent was V. Lecanii, which infected 1 % of ferences between the number of trap insects infected by fungi insects. As in spring samples (Figure 2), it was isolated in from sites N-1 (P = 0.048), C-2 (P < 0.001) and S-3 (P = 0.006) autumn from soil of only one site in central Poland (C-1) (Figure 3). Three species of entomopathogenic fungi (I. fari- nosa, I. fumosorosea and M. anisopliae) from soils taken in spring and 4 species (all above plus B. bassiana) from soils obtained in autumn (Figures 4, 5, respectively) were isolated on selective medium. Verticillium lecanii was not isolated on selective medium. None of the fungal species from soils taken in spring in site N-2 and in two sites in central Poland was isolated on selective medium (Figure 4) despite the fact that infection of trap insects by several species of fungi had been observed in these sites earlier.

Figure 3. Percentage of insects infected by entomopathogenic fungi isolated from soil in autumn. *Statistically significant dif- ferences between the number of trap insects infected by fungi from site S-3 (P = 0.006)

In soil samples collected in spring, most trap insects were infected by I. fumosorosea and M. anisopliae (Fig- ure 2). Isaria fumosorosea was isolated from soils of all analysed forest plantations. Most insects (35 %) were infected by isolate of this species obtained from soil of a single site in southern Poland (S-1). The second most infecting species was M. anisopliae, which occurred in all Figure 4. The number of colony forming units (cfu) of entomo- sites of southern Poland (13-26 % of infected insects) and pathogenic fungi isolated from soil collected in spring. *Statisti- with less intensity (4 and 18 % infected insects) in two cally significant differences between the number of cfu of fungi sites of central Poland (C-1 and C-2, respectively). Other isolated from soil of site C-1 (P = 0.048) and S-3 (P = 0.021)

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Discussion

It was found that soils of 1-3-year-old forest planta- tions are the habitats of 5 species of entomopathogenic fungi (M. anisopliae, I. fumosorosea, B. bassiana, I. fa- rinosa and V. lecanii), which are commonly found in soil habitats (Bajan and Kmitowa 1997, Bałazy 2000). These species are classified as facultative pathogens. They can develop in the soils as saprotrophic fungi, which is very important for their survival after application in the form of biopreparations. Definitely more isolates of fungi were found in soils sampled in spring than in those taken in autumn. The dif- ferences resulted certainly from higher soil moistures in Figure 5. The number of colony forming units (cfu) of entomo- spring time, which is commonly known to facilitate the pathogenic fungi isolated from soil collected in autumn. *Statis- development of fungi in soil habitat. In spring, southern tically significant differences between the number of cfu of fungi soils (mountain sites) were most frequented by entomo- isolated from soil of site S-3 (P = 0.007) pathogenic fungi and in autumn – those in the centre of the country. Such result could be an effect of the higher Similarly, in autumn samples entomopathogenic fungi moisture of mountain sites in spring. The effect of geo- were isolated from soils in central Poland and from only graphic location and habitat type on the presence of en- one site in southern Poland (S-3) (Figure 5). tomopathogenic fungi was studied by Vanninen (1995). Isaria fumosorosea was the species most frequently Based on her analyses of soils in Finland, the author found isolated from both spring and autumn samples on selec- that geographic location was important for M. Anisopliae, tive medium (Figures 4, 5). The highest number of cfu of while B. bassiana and P. farinosus (syn. I. farinosa) were this species was isolated from samples collected in spring more affected by habitat type. According to the study by in the south of Poland (S-3: over 9 × 102 cfu/g dry wt. of Leger et al. (1992), the occurrence of fungi in the environ- soil) (Figure 4), about 4 times less from soils of central ment can also be affected by host range (wide or narrow) Poland (C-1: about 2.5× 102 cfu/g dry wt. of soil) and the and their availability. These authors concluded that the least from soils in the north of the country (N-1: about most of M. anisopliae pathotypes has potentially broad 0.5 × 102 cfu/g dry wt. of soil). In autumn, I. fumosorosea host ranges, and minority had a narrow specialisation to- was isolated on growing medium from soils of all sites in wards a particular group of hosts. The isolates genetically central Poland and from one site in the south (S-3) (Figure adapted to a narrow host range have a lower degree of 5). However, in autumn the number of isolated cfu of this physiological adaptation compared with isolates adapted species was lower, up to1.8× 102 cfu/g dry wt. of soil. to a wide host range. Metarhizium anisopliae was more often isolated on The results demonstrated that M. anisopliae and I. growing medium from soils taken in spring than in au- fumosorosea were most frequent species of entomopatho- tumn (Figures 3, 4). In spring the species was isolated genic fungi in soils of forest plantations, especially in from soils of central and southern Poland: from about 1.0 spring. However, a high number of their spores in sam- × 102 (C-1) to nearly 4.5 × 102 (S-3) cfu/g dry wt. of soil pled soil (i.e. cfu on the growing medium) not always cor- (Figure 4). In autumn, the species was isolated only from responded with the number of infected insects. This was southern sites (S-3: nearly 3 × 102cfu/g dry wt. of soil) observed in I. fumosorosea isolated from soil in south- (Figure 5). ern Poland (S-3). In spite of relatively high number of The remaining two species: I. farinosa and B. bassi- spores of this fungus, infection of trap insects was rather ana were isolated on growing medium from soils of single low, which might evidence low biological activity of the sites: I. farinosa obtained in spring only from one site in pathogen. A reverse situation was observed in M. aniso- the north (N-1: less than1 × 102cfu/g dry wt. of soil) (Fig- pliae isolated from soil of the same site, which indicated ure 4) and in autumn from soil in central Poland (C-3: a high activity of its spores in the habitat. It seems that if over 1.0× 102cfu/g dry wt. of soil) (Figure 5). Beauveria in the soil sample there is a high number of spores and bassiana was isolated only from soil sampled in autumn parasitism of insect is low, it may be related to reduced in one site of central Poland (C-4: less than 1.0 × 102cfu/g activity of this fungus in these environments. Such cor- dry wt. of soil) though the species was not found in this relation may affected by the life strategy of a fungus site with the use of trap insects. (Chandler 2009). According to the strategy “sit and wait”,

2016, Vol. 22, No. 1 (42) ISSN 2029-9230 1214 BALTIC FORESTRY ENTOMOPATHOGENIC FUNGI IN THE SOILS /.../ E. POPOWSKA-NOWAK ET AL. the fungus can produce a large number of spores, which and Cagáň (2011) found that B. bassiana and I. farinosa greatly increases the possibility of insect infection and were more frequent than M. anisopliae in forest habitats. survival of spores in the soil, even in the absence of the So variable results of presented studies, sometimes host. Miętkiewski et al. (1991) found the domination of different from those obtained by other authors, may re- Paecilomyces fumosoroseus (syn. I. fumosorosea) among sults from the fact that the presence and activity of ento- entomopathogenic fungi inhabiting 50 to 60-year-old pine mopathogenic fungi in soils are affected by many factors tree stands. However, these authors did not find the pres- like organic matter content, pH, type of soil and the way of ence of M. anisopliae, which was often found in soils of its cultivation (Walstad et al. 1970, Quesada-Moraga et al. forest plantations studied by us. Such results may suggest 2007, Bouamama et al. 2010). Also microclimatic condi- that M. anisopliae prefers soils of open areas such as clear tions (temperature, moisture) and host density strongly in- cuts with up to 5-year old seedlings, compared to soils fluence on trophic interaction between entomopathogenic covered with older trees. fungi and insect populations (Walstad et al. 1970, Karg Beauveria bassiana also found in analysed soils, in and Balazy 2009). Dispersion of fungi in soils is facilitat- spite of its presence in many sites had no high biological ed by various arthropod species of the order Collembola activity. Miętkiewski et al. (1991) noted that the species (Dromph 2001, 2003). A decrease of biomass and taxo- is infrequent in forest soils. So far, this fungus can kill the nomic differentiation of entomofauna was found to limit large pine weevil only in laboratory conditions. Such a pathogens due to a lack of appropriate host species (Karg conclusion may be supported by results obtained by An- and Bałazy 2009). It was noted, for example, that M. an- sari and Butt (2012), who observed 100 % mortality of isopliae finds favourable conditions for development as a all growth stages of H. abietis infected in the laboratory saprophyte in the rhizosphere and its occurrence depends by B. bassiana and by two fungi of the genus Metarhi- also on plant community overgrowing soil (Hu and Leger zium: M. robertsii and M. brumneum. Wegensteiner and 2002, Wang et al. 2005). Moreover, Leger (2008) is of the Führer (1988) found 86-100 % mortality of the large pine opinion that rhizosphere is a place of mutual interactions weevil beetles infected with a dose of 4 × 107 conidia between insects and their pathogens and the effectiveness of B. bassiana/insect at 20 and 33 0C in the laboratory and survival of the pathogen is affected by interactions conditions. However, no fungal infections were noted in among plant, insect and pathogen. Literature data also re- beetles feeding on bark treated with the fungus in the field veal that fungi in soil may interact with each other. Some conditions. This means that B. bassiana present in natural authors even suggest that competition between soil fungi soils probably exerts an insignificant effect on the den- may sometimes be stronger than effects of habitat factors sity of the large pine weevil in forest plantations. Field such as soil moisture (Widden and Abitbol 1980). attempts to control populations of the large pine weevil Obtained results are the first in the country contribu- with B. bassiana and M. anisopliae applied together with tion on species composition of entomopathogenic fungi entomopathogenic nematodes: Sterneinema carpocapsae in soils of forest plantations established on clear cuttings. and H. downesi made by Wiliams et al. (2013) showed Continuation of these studies will allow for selecting na- a higher effectiveness of nematodes, which were respon- tive isolates of fungi with optimum activity against bee- sible for 50 % mortality of the larvae of the lesser pine tles of the large pine weevil. Application of such isolates weevil. Fungi infected 20 % of larvae and pupae of the in practice may supplement other biological methods as pest. No synergy between the effect of applied species of an element of integrated protection of crops from the large nematodes and fungi was found. Perhaps a poor ability to pine weevil. This is evidenced by many studies aimed at reproduce within the forest environment is the reason for the selection of entomopathogenic fungi characterized by low biological activity of B. bassiana applied against H. high biological activity as the promising factors in the abietis in field conditions. protection of forest plantations against the large pine wee- The next species isolated from forest soils was V. vil (Williams et al. 2013). lecanii present exclusively in one site of central Poland. The number of trap insects infected by this species was Acknowledgements low (1 %). This allows for supposition that V. lecanii is present sporadically in studied forest habitats. Isaria fa- The study was made within the grant N309 428838 rinosa was isolated from one site in the north and one in financed in the years 2010-2013 by the National Centre the centre of the country and may be thus classified to in- of Science and by Faculty of Biology and Environmental frequent fungi in soils of forest plantations. Miętkiewski Sciences, Cardinal Stefan Wyszynski University in War- et al. (1991), however, did not find I. farinosa in forest saw, Poland. soils. On the contrary, Chandler et al. (1997) and Medo

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Understanding the evolution and function of Agricultural and Forest Entomology 11: 91–100. entomopathogenic fungi. http://www2.warwick.ac.uk/fac/sci/ Quesada-Moraga, E., Navas-Cortés, J.A., Maranhao, E.A.A., lifesci/research/entomopathogenicfungi/understanding_the_ Ortiz-Urquiza, A. and Santiago-Álvarez, C. 2007. Factors evolution_and_function_of_entomopathogenic_fungi.pdf affecting the occurrence and distribution of entomopathogenic Dillon, A.B., Ward, D., Downes, M.J. and Griffin, Ch.T. 2006. fungi in natural and cultivated soils. Mycological Research Suppression of the large pine weevil Hylobius abietis (L.) 111(8): 947-966. (Coleoptera: Curculionidae) in pine stumps by entomopatho- Petersson, M., Örlander, G. and Nilsson, U. 2004. Feeding barri- genic nematodes with different foraging strategies. Biological ers to reduce damage by pine weevil (Hylobius abietis). Scan- Control 38: 217-226. dinavian Journal of Forest Research 19: 48-59. Dromph, K.M. 2001. 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Ef- and infested Scots pine seedlings in Poland. Annals of Forest fects of environmental conditions on two species of muscar- Science 70(4): 391-402. dine fungi (Beauveria bassiana and Metarrhizium anisopliae). Kadlec, Z., Stary, P. and Zumr, V. 1992. Field evidence for the Journal of Invertebrate Pathology 2: 221-226. large pine weevil, Hylobius abietis as a vector of Heteroba- Wang, Ch., Hu, G. G. and Leger, R.J.St. 2005. Differential gene sidion annosum. European Journal of Forest Pathology 22: expression by Metarhizium anisopliae growing in root exu- 316-318. date and host (Manducasexta) cuticle or hemolymph reveals

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mechanisms of physiological adaptation. Fungal Genetics and gies. Forest Ecology and Management 305: 2012-222. Biology 42: 704-718. Zimmerman, A. 1986. The „Galleria bait method” for detection of Wegensteiner, R. and Fuhrer, E. 1998. Zurwirksamkeit von Beau- entomopathogenic fungi in soil. Journal of Applied Entomol- veria bassiana (Bals.) Vuill. gegen Hylobius abietis L. (Col. ogy 102: 213-215. Cuculionidae). Entomophaga 33 (30): 339-348. Widden, P. and Abitbol, J.J. 1980. Seasonality of Trichoderma species in a spruce forest soil. Mycologia 72: 775-784. Received 14 September 2015 Williams, C.D., Dillon, A.B., Harvey, Ch.D., Hennessy, R., Na- Accepted 25 January 2016 mara, L. Mc and Griffin, Ch.T. 2013. Control of a major pest of forestry, Hylobius abietis, with entomopathogenic nematodes and fungi using eradicant and prophylactic strate-

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LOW IMPACT OF STUMP REMOVAL ON MYCORRHIZATION AND GROWTH /.../ D. KLAVINA, , ET AL. Low Impact of Stump Removal on Mycorrhization and Growth of Replanted Picea abies: Data from Three Types of Hemiboreal Forest

DĀRTA KĻAVIŅA1,2, AUDRIUS MENKIS3,*, TĀLIS GAITNIEKS1,4, TAINA PENNANEN5, ANDIS LAZDIŅŠ1, SANNAKAJSA VELMALA5 AND RIMVYDAS VASAITIS3

1 Latvian State Forest Research Institute “Silava”, Rigas 111, LV-2169 Salaspils, Latvia 2 University of Latvia, Faculty of Biology, Kronvalda Blvd. 4, Riga LV-1586, Latvia 3 Department of Forest Mycology and Plant Pathology, Uppsala BioCenter, Swedish University of Agricultural Sciences, P.O. Box 7026, SE-75007 Uppsala, Sweden 4 Forest Sector Competence Center, SIA “MNKC”, Dzerbenes Street 27, Riga, LV-1006, Latvia 5 Natural Resources Institute Finland (Luke), Vantaa Research Centre, P.O. Box 18, FI-01301 Vantaa, Finland * corresponding author; e-mail: [email protected]; Phone: +4618672729; Fax: +4618673599

Kļaviņa, D., Menkis, A.*, Gaitnieks, T., Pennanen, T., Lazdiņš, A., Velmala, S. and Vasaitis, R. 2016. Low Impact of Stump Removal on Mycorrhization and Growth of Replanted Picea abies: Data from Three Types of Hemiboreal forest. Baltic Forestry 22(1): 16-24.

Abstract

The objective was to investigate the impact of stump removal from clear-cuts on early mycorrhizal colonisation, seedling growth, and chemical properties of soil and needles of replanted Picea abies. The study included three forest types differing in soil conditions: Hylocomiosa (H), Myrtillo-sphagnosa (MS) and Myrtillosa-mel. (MM) forest types. Soil characteristic for H forest type is well-aerated dry podzol, while MS and MM comprise poorly-aerated gleyic, and respectively, wet and drained (dry) podzols. The clear-cuts were made in winter 2010-2011, stump removal accomplished during late spring – early autumn 2011, and the plantations established in April 2012. Prior to planting, each clear-cut was divided into discrete plots, subjected either to stump removal or, alternatively, to traditional soil preparation by disc trenching. After one growing season (in autumn 2012), seedling mycorrhization, shoot and root morphological parameters (length of the shoot, root collar diameter, mass of new roots), and chemical composition of needles and rhizosphere soil were determined. Seedling mycorrhization, chemical composition of needles and soil did not differ significantly between stump removal and trenching plots in any of the forest types. Also richness of mycorrhizal morphotypes and communities of root inhabiting fungi were similar. Fungi commonly detected in forest nurseries dominated fungal communities in roots, among which Thelephora terrestris was the most abundant composing 55.3 %. In each of the forest types, shoot length, root collar diameter and mass of new roots were either higher on stump removal plots or did not differ significantly. The only exception in this respect was the higher shoot height observed on trenching plots in H forest type. In conclusion, the study demonstrated that after one growing season stump removal has low or no impact on communities of mycorrhizal (and other soil) fungi, and performance of replanted P. abies seedlings on podzols with different mechanical composition, aeration and moisture.

Keywords: clear-cut, forest management, mycorrhiza, Norway spruce, reforestation, soil fungi, stump removal.

Introduction al. 2007, Menkis et al. 2012). However, as silvicultural practices may affect communities of ECM fungi (Jones In Latvia, the growing demand for biofuel makes the et al. 2003, Heinonsalo et al. 2004), the impact of stump stump removal an attractive option to secure its supply. removal in this respect should also be evaluated. For ex- However, the potential effects of stump removal on below ample, Pennanen et al. (2005) showed that even light soil ground fungal communities, in particular ectomycorrhizal preparation such as mounding can cause changes in the (ECM) ones, are generally poorly understood. ECM fungi structure of ECM community. To date, only few studies in boreal forests enhance nutrient and water uptake to their investigated the impact of stump removal on belowground hosts (Smith and Read 1997). Due to these effects, ECM fungal communities associated with seedling roots (e.g. fungi may promote establishment and growth of tree seed- Page-Dumroese et al. 1998, Menkis et al. 2010, Kataja- lings after their outplanting (Kropp et al. 1985, Menkis et aho et al. 2012); therefore, more studies are needed.

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LOW IMPACT OF STUMP REMOVAL ON MYCORRHIZATION AND GROWTH /.../ D. KLAVINA, , ET AL.

Stump removal may also impact forest regeneration H forest type is well-aerated dry podzol, while MS and on clear-cuts. Although the majority of available studies MM comprise poorly-aerated gleyic, respectively wet and indicate improved seedling establishment and growth on drained (dry) podzols (Bušs 1997). In the area, the average stump removal sites, especially on dry and sandy soils air temperature during the survey period (growing season (Vasaitis et al. 2008 and references therein), some stud- 2012) was 6.1 ºC and precipitation amounted 832 mm ies indicate that stump harvesting may lead to increased (Latvian Environment, Geology and Meteorology Cen- biomass removal, which may result in a significant loss of tre), which in comparison were close to typical values. nutrients, leading to potentially negative effects on future In all sites, stands were clear-felled in winter site productivity (Palviainen et al. 2010, Egnell 2011). 2010/2011 but stumps were left intact. Before planting Besides, stump removal in certain cases is associated in spring 2012, in each site stumps were removed from with site disturbances, which may lead to alterations in half of the area using a New Holland tractor (v. 5215B) soil chemical, physical and biological properties (Hope equipped with a stump extractor MCR-500 (LSFRI “Si- 2007). Therefore, in this respect more studies are needed, lava” and Orvi Ltd., Salaspils, Latvia). For another half especially covering broader spectra of forest types and of each site, disc trenching was used as a soil preparation geographical regions. treatment using two-row disc trencher TTS Delta (LSFRI The objective of the present study was to evaluate “Silava”, Salaspils, Latvia). Distance between trenching impact of stump removal on mycorrhization and growth rows was ca. 2.5 m. Trenching is a common forest soil of Picea abies seedlings one growing season after their scarification method in Latvia (Lazdiņš 2012). In the MS outplanting on clear-cuts of Hylocomiosa (H), Myrtillo- and H forest types, soil preparations (stump removal and sphagnosa (MS) and Myrtillosa-mel. (MM) forest types trenching) were done in two replicates while in the MM in Latvia, comprised of podzol soils differing in mechani- type the treatments were not replicated. As a result, ten cal composition, aeration and moisture. plots were established. Within each clear-cut, different treatments and replicates were separated from each other Materials and methods by a 20 m buffer zone. Two-year-old containerized seedlings of P. abies (lo- Study sites and experimental design cal forest nursery, Norupe, Latvia) were planted in April The study sites comprised three forest clear-cuts (3.8 2012. Seedlings were planted in rows at a density between ha, 2.7 ha and 1.5 ha in size or 8 ha altogether) situated ca. 918 and 2,773 seedlings per hectare. At outplanting, in central Latvia (Table 1). Each site represented different seedlings were ca. 12 cm in height (Lazdiņš 2012). Prior forest type including Hylocomiosa (H), Myrtillo-sphag- to planting, ECM status of the roots was not examined, but nosa (MS) or Myrtillosa-mel. (MM). Characteristic for was assumed to be similar for all seedlings due to similar

Table 1. Position and characteristics of three clear-cuts reforested with Picea abies. The soil in each clear-cut was prepared using stump removal and disc trenching

No. of No. of No. of Forest type of a Soil preparation Reforested Position seedlings plants root tips Former forest stand clear cut treatment area (ha) planted sampled sampled Norway spruce, 60%, Scots Hylocomiosa (H) Stump removal 0.95 1474 20 2000 pine, 20%, silver birch, Dry podzolic N56°53', Stump removal 0.95 1950 20 2000 20%, common aspen and mineral soil of good E24°41' Trenching 0.95 1837 20 2000 black alder in admixture. aeration Trenching 0.95 1383 20 2000 Age is 80 years All H 3.8 6644 80 8000 Myrtillo-sphagnosa Stump removal 0.675 620 20 2000 Scots pine, 70%, Norway (MS) Wet podzols N56°51', Stump removal 0.675 1257 20 2000 spruce, 30%. Age is 100 or gleyic mineral E24°38' Trenching 0.675 714 20 2000 years soil of poor aeration Trenching 0.675 807 20 2000 All MS 2.7 3398 80 8000

Myrtillosa mel. (MM) Norway spruce, 70%, Scots Drained gleyic N56°53', Stump removal 0.75 1760 20 2000 pine, 20 %, silver birch, mineral soil of poor E24°39' Trenching 0.75 2080 20 2000 10%, common aspen and aeration black alder in admixture. All MM 1.5 3840 40 4000 Age is 80 years

All clear-cuts 8.0 13882 200 20000

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LOW IMPACT OF STUMP REMOVAL ON MYCORRHIZATION AND GROWTH /.../ D. KLAVINA, , ET AL. growing conditions in the nursery. Previously, ECM sta- entific, Inc., USA) was used for Direct PCR from root tips tus of seedling roots was shown to be similar in similar (Velmala et al. 2014). PCR amplification was performed nursery cultivation systems (Menkis et al. 2005, Menkis using fungal-specific primer fITS7 (Ihrmark et al. 2012) et al. 2011). and universal primer ITS4 (White et al. 1990), and Phire Hot Start II DNA polymerase (Thermo Fisher Scientific, Seedling sampling and measurements Inc., USA). Sequencing was performed in one direction In October 2012, a half-year after planting, 20 Nor- using ITS4 primer by Macrogen Europe Inc. (Amster- way spruce seedlings were collected from each of ten dam, Netherlands). Raw sequence data were analysed us- plots, resulting in 200 sampled seedlings altogether (Ta- ing the SeqMan version 5.07 software from DNASTAR ble 1). In each plot, seedlings were sampled along the di- package (DNASTAR, Madison, WI, USA). Databases at agonal in a consecutive order. Seedlings were carefully GenBank (Altschul et al. 1997) and UNITE (Kõljalg et al. excavated to preserve the fine roots, labelled, placed in 2005) were used to determine the identity of ITS rRNA plastic bags, transported to laboratory and kept at 4 °C sequences. The criteria used for identification were the for a maximum period of two weeks before further pro- following: sequence coverage > 80 %; similarity to taxon cessing. For each seedling, total length of the present-year level 97–100 %, similarity to genus level 94–96 %. The top shoot and root collar diameter was measured. Shoots sequences are available from GenBank under accession were separated from the roots, dried for 12 h at 60 ºC numbers KF954060-KF954092. and weighted. Roots of each seedling were washed in tap water and separated in two categories: roots originally Chemical analysis of needles and soil present in a forest nursery container (“old roots” present Soil samples used for chemical analyses comprised in a peat lump); and, current year roots (“new roots”) pro- forest soil attached to seedling roots produced during the duced during the growing season 2012 (growing out from growing season 2012 (new outgrown roots). Substrate the peat lump). Old roots were directly placed into the from the nursery was excluded. In total, 20 soil samples oven and dried for 12 h at 60 ºC. New roots were stored were collected from each of ten plots (see Table 1) and at 4ºC for analysis of ECMs. Following analysis of ECMs within each plot pooled together resulting in ten bulk sam- (see below), different morphological parameters of these ples. Soil was dried for a week at room temperature (ca. roots (root length, volume, biomass, surface area, number 21 ºC) and sieved (mesh size 2×2 mm) to separate larger of root tips) were determined by using Epson Perfection fractions and roots which were discarded. Electrical con- V750Pro scanner (Epson, Tokyo, Japan) and WinRHIZO ductivity (EC), pH and concentration of K, Ca, Mg, Zn, 2005 C (Regent instruments Inc., Canada) software. After Mn, N, P, C and S were determined. scanning roots were dried for 12 h at 60 ºC and weighted. Needles were separated from the oven dried shoots. From each seedling, 1 g of dry needles was taken and Analysis of ectomycorrhizas within each plot all sampled needles were pooled together To evaluate mycorrhization of roots, new outgrown resulting in ten bulk samples. Sampled needles were oven- roots were placed in glass Petri dishes (14 cm in diam- dried at 60 °C for two weeks and then finely grounded us- eter) with a grid on the bottom (mesh size 7×7 mm) and ing the A-11 analytical mill (IKA-Werke GmbH, Staufen, examined using stereomicroscope (Leica MZ-7.5, Solms, Germany), and concentration of K, Ca, Mg, Zn, Mn, P, N, Germany). Root tips in vicinity to the crossing points of C, and S was determined. Chemical analyses of soil and the grid were systematically sampled. In total, 100 single needles were done using established standard methods at root tips were sampled from each root system and their LSFRI “Silava”, the Laboratory of Forest Environment, mycorrhization and ECM morphotypes were determined. Salaspils, Latvia. ECM roots were identified by the presence of mantle, external hyphae or rhizomorphs and the absence of root Statistical analyses hairs. ECM roots were divided into different morphotypes Differences in seedlings morphological parameters, based on their colour, form and texture of the mantle and mycorrhization, richness of ECM morphotypes, chemi- pattern of rhizomorphs and/or external mycelia (Agerer cal composition of needles and soil between different 1986-2006). treatments of each study site were analysed by one-way One to six root tips of each distinct ECM morpho- analysis of variance (ANOVA) and Tukey’s test, which type were sampled from each of 17 randomly selected provides confidence intervals for all pairwise differences seedlings of each sampling plot (170 seedlings altogether) between means (Chalmers and Parker 1989, Fowler et al. and used for molecular identification of fungal taxa. Se- 1998). The statistics were computed using Minitab® v.16 lected root tips were separately placed in 1.5 ml centrifu- (Minitab Inc., Coventry, UK). Richness of fungal taxa gation tubes and stored at -20 ºC until used for molecular detected by ITS rRNA sequencing in different treatments analyses. Phire Plant Direct PCR Kit (Thermo Fisher Sci- of each site was compared by using nonparametric Chi-

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LOW IMPACT OF STUMP REMOVAL ON MYCORRHIZATION AND GROWTH /.../ D. KLAVINA, , ET AL. square test (Mead and Curnow 1983). As root tips used resembled fungi from the nursery (Table 2) (Menkis et al. for ITS rRNA sequencing were pre-selected during the 2005, Stenström et al. 2014). Such characteristic nursery morphotyping, the data from different replicates within fungi (e.g. Thelephora terrestris), which are also known each treatment and site were pooled and analysed togeth- to be better adapted to the specific conditions of the nurs- er. Shannon diversity index and quantitative Sorensen ery (frequent disturbance and high amounts of mineral similarity index were used to characterise diversity and nutrients) (Marx et al. 1984), were likely benefiting from composition of fungal communities in different treat- the alterations of soil properties as a result of site distur- ments and sites (Shannon 1948, Magurran 1988). Fungal bance (Hope 2007). However, such effect is likely to be community structure and possible treatment effects were temporal as in the later years these fungi are gradually analysed using Principal Component Analysis (PCA) in replaced by the indigenous ECM fungi present at a forest CANOCO 4.5 (ter Braak and Smilauer 1998). site (Menkis et al. 2007, Klavina et al. 2013). In the pres- ent study, T. terrestris dominated fungal communities in Results and Discussion roots, showing higher abundances in stump removal treat- ments than in corresponding trenching treatments, while Results from our previous work (Menkis et al. 2007) the remaining taxa altogether were less abundant that T. demonstrated that already early mycorrhizal status has terrestris (Table 2). a profound long-term effect on growth of P. abies seed- Among all taxa, eight of them were exclusively pres- lings outplanted on mineral soil. The results of the pres- ent in stump removal treatments, twelve of them occurred ent study highlight that stump removal, as compared with in trenching treatments and thirteen of them were com- traditional trenching, has no effect on early mycorrhiza- mon to both treatments (Table 2). The Shannon diversity tion of P. abies in forest types characterized by podzols index of fungal communities in different treatments and differing in aeration and moisture (p > 0.07). Mycorrhiza- study sites was between 1.01 and 2.39 (Table 2). The tion in the H-type was 84.0 % ± 2.1SE in stump removal quantitative Sørensen similarity index of fungal commu- treatment and 87.1 %±1.4SE in trenching treatment, in the nities between stump removal treatment and trenching MS-type amounted 81.7 % ± 1.7SE and 76.9 % ± 2.0SE, treatment was 0.41 in the H-type, 0.61 in the MS-type respectively, and in the MM-type made up 81.1 % ± 3.6SE and 0.67 in the MM-type (data not shown). The princi- and 80.4 % ± 3.4SE, respectively. Furthermore, richness pal component analysis (PCA) of fungal communities ex- of ECM morphotypes in each investigated forest type plained 76.1 % variation on Axis 1 and 10.7 % variation did not differ significantly between stump removal and on Axis 2. PCA showed that stump removal and trench- trenching treatments (p > 0.09), which in the H-type was ing treatments were in close proximity on Axis 1 (which 3.3±0.1SE in stump removal treatment and 3.2 ± 0.1SE in explained most of the variation and the treatment effect trenching treatment, in the MS-type made 3.3 ± 0.1SE and on fungal communities) for the H-type and the MS-type 3.5 ± 0.1SE, respectively, and in the MM-type reached but slightly more distant for the MM-type (Figure 1). In 2.4 ± 0.2SE and 2.9 ± 0.1SE, respectively. Amplification PCA, different forest types (the H, MS and MM types) and direct sequencing of fungal ITS rRNA from ECM were more or less well separated from each other (Fig- morphotypes showed that the number of fungal taxa in ure 1). In the present study, the majority of the dominant the H-type was 13 in stump removal treatment and 16 in fungi were often shared between different treatments of trenching treatment, in the MS-type amounted to 14 and each forest type (Table 2). As a result, PCA showed a 19, respectively, and in the MM-type figured up to 7 and 8 rather proximal aggregation on Axis 1 of both treatments (Table 2) , respectively. Consequently, richness of fungal within each MS- and H-types at the same time show- taxa in each investigated forest type did not differ signifi- ing that stump removal had little impact on fungal com- cantly between stump removal and trenching treatments (p munity structure (Figure 1). A more distal placement of > 0.29). The total fungal community was comprised of 33 different treatments within the MM-type was largely de- taxa, among which 15 (45.5 %) were Ascomycetes and 18 termined by abundance of T. terrestris while composition (54.5 %) belonged to Basidiomycetes (Table 2). Among of fungal communities was similar (Table 2). PCA also all fungi, 20 (60.6 %) were identified to taxon level, 11 showed certain specificity of fungal communities present (33.3 %) to genus level and 2 (6.1 %) remained unidenti- at each forest type as these were more or less well separat- fied. The most common taxa were Thelephora terrestris ed from each other (Figure 1) thereby indicating the rela- (55.3 %), Wilcoxina sp.1 (12.3 %), Acephala macroscle- tive importance of rare taxa (probably indigenous) present rotiorum (4.7 %), Cenococcum geophilum (4.0 %) and at each site. In PCA, Axis 1 and Axis 2 regression coef- Amphinema byssoides (3.6 %) (Table 2). Results showed ficients for the three most common fungi were the follow- that in different treatments of each forest type the richness ing: T. terrestris 25.9 and -3.2, respectively, Wilcoxina sp. of ECM morphotypes and communities of root inhabiting 1 -4.4 and -20.5, respectively, and A. macrosclerotiorum fungi (in particular dominant) were largely the same and 6.9 and -15.9, respectively. Quantitative Sørensen simi-

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Table 2. Frequency of fungal taxa shown as percentage of ECM roots colonised of Picea abies seedlings under stump removal and trenching site preparation treatments. The number of ECM root tips used is shown in the parentheses

Myrtilliosa-sphagnosa Hylocomiosa (H) Myrtilliosa mel (MM) Total (MS) Genbank Taxa Stump Stump Stump accession No. Trenching Trenching Trenching removal removal removal (134) (169) (44) (682) (101) (171) (63) Ascomycetes Acephala macrosclerotiorum KF954060 3.0 4.2 7.1 4.1 - 6.9 4.7 Cadophora sp. KF954063 0.1 - - 0.2 - - 0.1 Cenococcum geophilum KF954064 2.6 5.1 3.3 0.5 1.8 19.4 4.0 Elaphomyces sp. KF954066 0.5 - - - - - 0.1 Hydnotrya bailii KF954069 - - - 0.8 - - 0.2 Ilyonectria radicicola KF954082 - 2.0 - - - - 0.3 Meliniomyces bicolor KF954070 1.7 0.6 3.4 0.1 0.6 14.7 2.5 Meliniomyces sp. KF954071 0.8 - 3.1 0.9 - - 1.2 Meliniomyces variabilis KF954084 - - 2.4 - - - 0.7 Phialocephala fortinii KF954086 - 4.7 0.4 2.2 4.7 0.5 1.9 Tuber sp. KF954075 - - - 1.2 - - 0.3 Wilcoxina mikolae KF954078 - 5.9 - - - - 1.0 Wilcoxina sp.1 KF954079 24.7 34.8 1.6 4.1 - 20.9 12.3 Wilcoxina sp.2 KF954080 - 2.1 - 2.2 0.6 - 0.9 Unidentified sp. A KF954077 - 0.5 - - - - 0.1 All Ascomycetes 33.5 59.9 21.4 16.1 7.7 62.3 30.2 Basidiomycetes Amphinema byssoides KF954061 10.7 1.5 2.6 0.1 0.4 13.0 3.6 Amphinema sp. 1 KF954062 0.1 - 3.0 3.6 - 0.5 1.8 Amphinema sp. 2 KF954081 - - - 1.8 - - 0.4 Clavulina sp. KF954065 - 6.3 - 9.5 - - 3.2 Cryptococcus magnus KF954092 10.6 - - - - - 1.5 Hebeloma sp. KF954068 - 0.6 - 0.2 - - 0.2 Inocybe napipes KF954083 - - 0.3 - - - 0.1 Paxillus involutus KF954085 - - 2.2 0.4 - - 0.7 Russula cf. emetica KF954087 - 0.4 - - - - 0.1 Russula densifolia KF954088 0.4 - - - - - 0.1 Russula cf. firmula KF954089 - 0.2 - - - - 0.04 Russula cf. velenovskyi KF954072 - - - 2.8 - - 0.6 Sebacina sp. KF954073 8.2 - - - - - 1.1 Thelephora terrestris KF954074 36.5 30.4 69.4 62.9 91.1 24.2 55.3 Tomentella stuposa KF954076 - - 0.2 - - - 0.1 Tylospora asterophora KF954090 - 0.6 - - - - 0.1 Tylospora fibrillosa KF954091 - - - 2.6 0.8 - 0.7 Unidentified sp. B KF954067 - - 1.0 - - - 0.3 All Basidiomycetes 66.5 40.1 78.6 83.9 92.3 37.7 69.8 Total no. of taxa 13 16 14 19 7 8 33 Shannon diversity index 2.15 2.39 1.95 2.17 1.01 1.64

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Figure 1. Ordination diagram based on a principal compo- nent analysis of fungal communities in roots of Picea abies seedlings outplanted on Hylocomiosa (H), Myrtillo-sphagnosa (MS) and Myrtillosa mel. (MM) forest types in which soil was prepared using stump removal (open circles) and disc trench- ing (filled circles). Taxonomic names correspond to a position (centred) in the ordination and represent ten most common taxa of the present study larity indices were between moderate and high, repeat- tion was seedling shoot height at the H-type, which was edly suggesting that fungal communities detected in this significantly higher in trenching treatment than in stump study were similar and thus generally unaffected by the removal treatment. The latter demonstrated that stump re- stump removal treatment. The Shannon diversity indices moval in comparison to conventional trenching treatment of fungal communities were relatively low (Table 2) and on each of investigated forest types had in general low but of magnitude reported from forest nurseries (Flykt et al. sometimes slightly positive impact on growth of P. abies 2008, Stenström et al. 2014), indicating that diversity of seedlings. Such initial impact appears to be lasting since fungal taxa remained largely unchanged and thus gener- similarly better growth of the trees has also been observed ally unaffected by the stump removal treatment. 3 – 28 years after their outplanting (Kardell 2008, Kardell Observed non-significant differences in mycorrhiza- and Eriksson 2008, Menkis et al. 2010, Kataja-aho et al. tion were probably one of the reasons of low differences 2012). However, Egnell and Leijon (1999) reported that in seedling growth. Yet in a number of cases seedling mor- after 15 years the height increment of P. abies was lower phological parameters in stump removal treatments were following the whole-tree harvesting. This could probably either significantly higher or did not differ significantly be explained by natural variation imposed by specific con- from those in corresponding trenching treatments in each ditions present at different forest types. For example, in of investigated forest types (Table 3). A single excep- the present study only shoot height of the seedlings was

Table 3. Picea abies seedling morphological parameters after first growing season (2012) in Hylocomiosa, Myrtillo-sphagnosa, Myrtillosa mel. forest types in which soil was prepared using stump removal and disc trenching. Values are shown as the mean ± SE (standard error)

Hylocomiosa (H) Myrtillo-sphagnosa (MS) Myrtillosa mel. (MM) Morphological Parameter Stump removal Trenching Stump removal Trenching Stump removal Trenching (n=40) (n=40) (n=40) (n=40) (n=20) (n=20) Shoot height, cm 26.3±0.9 29.1±0.8* 28.4±0.8 29.3±0.6 28.0±1.3 31.2±1.3

Shoot biomass, g 7.3±0.5 7.1±0.3 6.9±0.3 6.4±0.3 7.4±0.5 7.0±0.5

Root collar diameter, cm 0.7±0.01** 0.6±0.02 0.6±0.02 0.6±0.01 0.7±0.03 0.6±0.02

Old root biomass, g a 3.1±0.2 2.9±0.1 3.3±0.2** 2.6±0.1 3.1±0.3 2.6±0.2

New root biomass, g b 0.9±0.1 0.8±0.1 0.7±0.1* 0.5±0.1 0.7±0.1* 0.4±0.1

Total root biomass, g a+b 4.0±0.2 3.6±0.2 4.0±0.2** 2.9±0.2 3.8±0.3* 3.0±0.2

Root length, cm b 1108.8±89 1035.9±68 1036.5±75* 835.4±51 954.0±107 723.6±91

Root surface area, cm2 b 230.0±20 214.4±16 196.3±17 162.7±11 203.8±24* 134.7±18

Root volume, cm3 b 3.9±0.4 3.6±0.3 3.0±0.3 2.6±0.2 3.5±0.5* 2.0±0.3

Number of root tips b 2877±231 3398±200 2612±156 2289±158 2349±295 1913±246

Mycorrhization, % b 84.0±2.1 87.1±1.4 81.7±1.7 76.9±2.0 81.1±3.6 80.4±3.4

Significantly greater at: * - p < 0.05; ** - p < 0.01. a Roots produced during seedling cultivation in a forest nursery. b Roots produced after seedling outplanting on a clear-cut (growing season 2012).

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LOW IMPACT OF STUMP REMOVAL ON MYCORRHIZATION AND GROWTH /.../ D. KLAVINA, , ET AL. significantly lower in stump removal treatment as com- er values of new root biomass, root length, root surface pared to trenching treatment of the H-type, but not in the area and root volume observed in stump removal plots of MS- or MM-types where it did not differ significantly be- the MS- and/or MM-types might well be influenced by the tween the treatments of these forest types (Table 3). Root fact that old root biomass on those plots was higher than collar diameter, by contrast, was significantly higher in in trenching plots (Table 3). stump removal treatment as compared to trenching treat- ment of the H-type while the remaining morphological Conclusions parameters did not differ significantly between those treatments (Table 3). The study demonstrated that stump removal on clear- Despite some slight variations, the amounts of re- felled forest sites representing forest site types compris- spective chemical elements in either needles or soil did ing podzol soils of wide range of moisture and aeration not differ significantly among the samples from stump had in general low but sometimes slightly positive impact removal vs. trenching treatments of each investigated for- on growth of replanted P. abies seedlings. At the same est type (Table 4), suggesting that the alterations in soil time, seedling mycorrhization and communities of root physical properties following stump removal can be the inhabiting fungi remained largely unchanged and there- cause of the observed root growth responses in P. abies fore generally unaffected by the stump removal treatment. seedlings (Table 3). On the other hand, significantly high-

Table 4. Amounts of different chemical elements in needles of Picea abies and soil after the first growing season (2012) in Hylo- comiosa, Myrtillo-sphagnosa, and Myrtillosa-mel. forest types in which soil was prepared using stump removal and disc trenching. Values are shown as the mean ± SE (standard error)

Hylocomiosa (H) Myrtillo-sphagnosa (MS) Myrtillosa mel.(MM) Chemical element Stump removal Trenching Stump removal Trenching Stump removal Trenching Needles N, g/kg 22.5±0.5 21.5±0.5 23.0±1.0 21.0±3.0 25.0 23.0 C, g/kg 529.5±1.5 551.0±12.0 532.0±9.0 554.0±6.0 540.0 549.0 S, g/kg 1.15±0.1 0.9±0.1 1.05±0.1 0.95±0.1 1.0 0.9 P, g/kg 1.3±0.1 1.2±0.1 1.3±0.1 1.2±0.1 1.4 1.2 Ca, g/kg 4.4±0.5 3.7±0.1 3.4±0.2 3.4±0.7 3.4 3.4 K, g/kg 6.5±0.2 6.2±0.1 7.3±0.3 6.6±0.4 7.3 5.9 Mg, g/kg 1.8±0.1 1.8±0.1 1.7±0.1 1.6±0.1 1.5 1.6 Mn, g/kg 0.5±0.1 0.25±0.1 0.3±0.1 0.25±0.1 0.4 0.4 Fe, g/kg 0.4±0.2 0.35±0.1 0.3±0.1 0.3±0.1 0.3 0.4 Soil Absolute moisture 3.1±0.1 4.1±2.4 6.2±2.2 7.3±2.4 2.0 3.3 of dry soil, % pH(KCl) 3.5±0.1 4.0±0.3 3.0±0.1 3.1±0.3 3.2 3.3 EC, μS cm-1 288.5±36.5 262.0±74.0 331.0±11.0 365.0±104.0 173 380 N, g/kg 3.2±0.3 2.8±1.3 5.1±1.8 5.8±1.4 2.3 3.7 C, g/kg 84.5±12.5 72.0±20.0 147.0±84.0 147.5±55.5 156.0 337.0 S, mg/kg 210.0±12.0 155.5±55.5 346.0±220.0 314.0±106.0 357.0 744.0 P, mg/kg 101.5±57.5 127.5±33.5 49.5±4.5 44.5±15.5 21.0 39.0 K, mg/kg 67.0±11.0 66.0±6.0 133.5±56.5 122.5±3.5 139.0 196.0 Mn, mg/kg 29.4±9.8 54.8±28.0 7.3±1.2 29.0±23.9 15.9 13.2 Mg, g/kg 0.12±0.1 0.19±0.1 0.17±0.1 0.17±0.04 0.2 0.3 Ca, g/kg 0.48±0.2 1.29±1.2 1.0±0.7 1.0±0.7 0.7 0.8 Zn, mg/kg 6.6±0.2 4.5±0.6 9.3±2.8 4.7±1.8 14.1 15.2

Note: In the MM, only one replicate was available.

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Acknowledgements Kardell, L. and Eriksson, L. 2008. Stump removal experiments in Bergslagen 1977-2007 [Stubbrytningsförsöken i Bergslagen 1977-2007]. Report 103. Institution för skoglig landskapsvård. We thank our colleagues at the Finnish Forest Re- Sveriges Lantbruksuniversitet, Uppsala, 60 pp. (in Swedish) search Institute “Metla” and LSFRI „Silava” for help Kataja-aho, S., Pennanen, T., Lensu, A. and Haimi, J. 2012. Does with genetic and chemical analyses. This work was finan- stump removal affect early growth and mycorrhizal infection cially supported by the Swedish Energy Agency, project of spruce (Picea abies) seedlings in clear-cuts? Scandinavian Journal of Forest Research 27: 746-753. 36101-1, ERDF Project No.2010/0255/2DP/2.1.1.1.0/ Klavina, D., Gaitnieks, T. and Menkis, A. 2013. 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New primers to amplify the fungal ITS2 region - evalu- seedlings produced under different cultivation systems. Silva ation by 454-sequencing of artificial and natural communities. Fennica 45: 283-289. Fems Microbiology Ecology 82: 666-677. Menkis, A., Lygis, V., Burokienė, D. and Vasaitis, R. 2012. Estab- Jones, M.D., Durall, D.M. and Cairney, J.W.G. 2003. Ectomycor- lishment of ectomycorrhiza-inoculated Pinus sylvestris seed- rhizal fungal communities in young forest stands regenerating lings on coastal dunes following a forest fire. Baltic Forestry after clearcut logging. New Phytologist 157: 399-422. 18: 33-40. Kardell, L., 2008. Stump removal and excavation. Forest energy Page-Dumroese, D.S., Harvey, A.E., Jurgensen, M.F. and Ama- experiments in Vindeln 1979-2004 [Stubbrytning och schakt- ranthus, M.P. 1998. Impacts of soil compaction and tree ning. Skogsenergiförsöken i Vindeln 1979-2004]. Report 102. stump removal on soil properties and outplanted seedlings in Institution för skoglig landskapsvård. Sveriges Lantbruksuni- northern Idaho, USA. Canadian Journal of Soil Science 78: versitet, Uppsala, 128 pp. (in Swedish) 29-34.

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Palviainen, M., Finer, L., Laiho, R., Shorohova, E., Kapitsa, Vasaitis, R., Stenlid, J., Thomsen, I.M., Barklund, P. and Dahl- E., Vanha-Majamaa, I. 2010. Carbon and nitrogen release berg, A. 2008. Stump removal to control root rot in forest from decomposing Scots pine, Norway spruce and silver birch stands. A literature review. Silva Fennica 42: 457-483. stumps. Forest Ecology and Management 259: 390-398. Velmala, S.M., Rajala, T., Heinonsalo, J., Taylor, A.F.S. and Pen- Pennanen, T., Heiskanen, J. and Korkama, U. 2005. Dynamics of nanen, T. 2014. Profiling functions of ectomycorrhizal diver- ectomycorrhizal fungi and growth of Norway spruce seedlings sity and root structuring in seedlings of Norway spruce (Picea after planting on a mounded forest clearcut. Forest Ecology abies) with fast- and slow-growing phenotypes. New Phytolo- and Management 213: 243-252. gist 201: 610-622. Shannon, C.E. 1948. A mathematical theory of communication. White, T.J., Bruns, T., Lee, S. and Taylor, J., 1990. Amplifica- The Bell System Technical Journal 27: 379-423. tion and direct sequencing of fungal ribosomal RNA genes for Smith, S.E. and Read, D.J., 1997. Mycorrhizal Symbiosis. Aca- phylogenetics. In: Innis, M.A., Gelfand, D.H., Sninsky, J.J., demic Press, London, UK, 605 pp. White, T.J. (Eds.), PCR protocols: A guide to methods and ap- Stenström, E., Ndobe, N.E., Jonsson, M., Stenlid, J. and Menkis, plications. Academic Press, Inc., San Diego, USA. A. 2014. Root associated fungi of healthy-looking Pinus syl- vestris and Picea abies seedlings in Swedish forest nurseries. Received 22 November 2014 Scandinavian Journal of Forest Research 29: 12-21. ter Braak, C.J.F. and Smilauer, P., 1998. Canoco reference manual Accepted 25 January 2016 and user’s guide to Canoco for Windows: software for canoni- cal community ordination, Version 4. Microcomputer Power, Ithaca, NY, USA, 351 pp.

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FUNGAL COMMUNITIES IN ROOTS OF SCOTS PINE AND NORWAY SPRUCE SAPLINGS GROWN /.../ D. KLAVINA, , ET AL. Fungal Communities in Roots of Scots Pine and Norway Spruce Saplings Grown for 10 Years on Peat Soils Fertilized with Wood Ash

DĀRTA KĻAVIŅA1*, INDRIĶIS MUIŽNIEKS2, TĀLIS GAITNIEKS1, VIZMA NIKOLAJEVA2, DAGNIJA LAZDIŅA1, ANDIS LAZDIŅŠ1, ARTA BĀRDULE1 AND AUDRIUS MENKIS3 1 Latvian State Forest Research Institute “Silava”, Rigas 111, Salaspils, LV-2169, Latvia 2 Department of Microbiology and Biotechnology, Faculty of Biology, University of Latvia, Kronvalda 4, Riga LV-1586, Latvia 3 Department of Forest Mycology and Plant Pathology, Uppsala BioCenter, Swedish University of Agricultural Sciences, P.O. Box 7026, SE-75007 Uppsala, Sweden *Corresponding author: e-mail: [email protected] ; Fax: +37167901359

Kļaviņa, D.*, Muižnieks, I., Gaitnieks, T., Nikolajeva, V., Lazdiņa, D., Lazdiņš, A., Bārdule, A. and Menkis, A. 2016. Fungal Communities in Roots of Scots Pine and Norway Spruce Saplings Grown for 10 Years on Peat Soils Fertilized with Wood Ash. Baltic Forestry 22(1): 25-33.

Abstract

The study was conducted in Scots pine (Pinus sylvestris L.) or Norway spruce (Picea abies (L.) H. Karst.) plots on peat soils, where fertilization trials with 0.5 to 2 kg m-2 wood ash had been conducted ten years previously. We examined the long-term effects of wood ash fertilization on fine root development (biomass and mycorrhizal colonization) and on communities of ectomycorrhizal (ECM) fungi and other soil microorganisms. Soil microorganisms were assessed by recording the number of colony forming units (CFU) from soil dilution series. ECM fungi in fine roots were evaluated by morphotyping and identified by sequencing of the fungal ITS region of rRNA genes. Soil chemical analysis indicated significant differences in soil pH between control and fertilized Scots pine plots, but soil pH did not differ among Norway spruce plots. Fine root biomass, numbers of living fine roots and numbers of dead fine roots did not differ significantly among wood ash treatments and the control for either pine or spruce. Relative abundance of living fine roots and its mycorrhizal colonization differed significantly among treatments and effects of wood ash were largely determined by tree species and amount of wood ash applied. Numbers of bacterial CFUs were higher in pine plots than in spruce plots and some differences were evident between the wood ash treatments and the control. Numbers of fungal CFUs were similar in all treatments. Of 21 fungal species identified on fine roots, the most common were Amphinema byssoides, Agaricomycetes sp., Lactarius sp. and Tuber anniae. Species composition of ECM fungi was mainly determined by the host species. However, principal component analysis and comparison of relative abundances of some species indicated differences in species composition among wood ash treatments. In conclusion, our data provided some evidence of a long-term effect of wood ash fertilization on soil pH, abundance of soil bacteria and diversity of ECM fungal community.

Key words: forest fertilization; liming; organic soils; fine root; ectomycorrhizal fungi, Pinus sylvestris, Picea abies

Introduction Viebke 2004) and only some have studied the effects on deep peat soils (e.g. Kakei and Clifford 2002). The effect Application of wood ash as a fertilizer can improve of wood ash fertilizer on fine root development largely wood production and nutrient balance in managed for- depends on the amount applied (Clemensson-Lindell and ests (Aronsson and Ekelund 2004). Long-lasting positive Persson 1995, Majdi and Viebke 2004, Augusto et al. effects of wood ash fertilization have been observed on 2008). The greatest adverse ecological effect of wood ash shallow peat soils, rich in nitrogen (Hytönen 2003, Arons- fertilization has been reported in acidophilic ecosystems, son and Ekelund 2004) and on drained peatlands (Ferm particularly regarding bryophytes, soil bacteria and ecto- et al. 1992, Moilanen et al. 2002, 2004, Haveraaen 2014, mycorrhizal (ECM) fungal communities (Pitman 2006, Rütting et al. 2014). Augusto et al. 2008). Most of the studies that have evaluated root param- Differences in ECM fungal community composition eters after wood ash treatment have been conducted on after liming have been explained by the increased forest mineral soils (e.g. Taylor and Finlay 2003, Majdi and soil capacity to neutralize soil acidity (Andersson and

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Söderström 1995, Erland and Taylor 2002, Kjøller and Clemmensen 2009). Most ECM fungal species are sensi- tive to high pH (Hung and Trappe 1983) and liming of peat soil may reduce growth of ECM fungal mycelium of some species as e.g. Piloderma spp. (Erland et al. 1990). Recent study by Klavina et al. (2015) has demonstrated long-term effect of forest fertilization with wood ash on ECM fungal community. However, how different amounts of wood ash applied affects ECM community structure and species di- versity associated with different tree species on peat soils is still poorly understood. The aim of this study was to evaluate long-term ef- fects of wood ash fertilization on fine root biomass and mycorrhizal colonization of Norway spruce and Scots pine and on communities of ECM fungi and other soil microorganisms.

Material and methods

Study area and experimental design The study was conducted in experimental plots that were established in 2004 and 2005 in the eastern part of Latvia at the Forest Research station in the Kalsnava Figure 1. Schematic arrangement showing randomised place- forest district (area is 0.1 ha, coordinates: 56º42,937’N, ment of Norway spruce and Scots pine in wood-ash fertilized 25º50,834’E). The treatments were established in a (shaded) and control (not shaded) plots fertilized with wood drained grass fen with 15-year-old Norway spruce (Picea ash in 2003 and 2004. The tree species in each plot is denoted abies (L.) H. Karst.) at low density (Gaitnieks et al. 2005). by the capital letters: P – pine and S – spruce. The numbers in The forest type was Myrtillosa mel. according to the Lat- the fertilized plots show the amount of the wood ash applied vian classification (Bušs 1997). The soil at the start of the (0.5, 0.6, 1.0, 1.2, 1.5 or 2.0 kg m-2) experiment was classified as a woody grass fen peat; the degree of decomposition was 47 % (Gaitnieks et al. 2005). Soil chemical analysis In May 2004, 2-year-old spruce and 1-year-old pine One soil sample was collected from each sample plot containerized seedlings were planted in rows in 2.7 m2 in late June 2014. A soil corer (3.5 cm in diameter) was square plots. Within each plot, seedlings were established used to take samples from 0–20 cm depth. In total, 44 soil at a 0.5×0.5 m spacing. In each plot, soil was prepared cores were collected (samples were not collected from manually (the understory plants were removed and the top plots where no trees have survived). Chemical analyses soil layer was turned over) and between 70 and 96 seed- of soil were conducted using established standard meth- lings were planted (the density of seedlings was reduced ods (International Organization for Standardization (ISO) after the first growing season by excavating between 30 standard). Samples were prepared for analysis according and 40 seedlings in each plot for analyses). Wood ash to ISO 11464:2005. Soil pH(H2O) was measured poten- was evenly dispersed over the soil surface a year prior tiometrically in deionised water suspension according to to planting of seedlings. Two wood ash treatments were LVS ISO 10390. Total N content was determined using a used, 0.6 kg m-2 and 1.2 kg m-2, with replication of three modified Kjeldahl method (ISO 11261:1995) and P was replicate plots for pine and six for spruce. In addition, tri- assayed spectrophotometrically using the ammonium als with pine seedlings and wood ash fertilization treat- molybdate method in 1 M HCl extract (LVS 398). Con- ments of 0.5, 1.0, 1.5 and 2 kg m-2 directly after planting centrations of K, Ca and Mg were determined by atomic were established at the same time in four replicate plots, absorption spectrophotometer with an acetylene-air flame which were randomly arranged in 4 blocks. This study in 1 M HNO3 extract. design resulted in 18 plots with Norway spruce and in 28 plots with Scots pine (Figure 1). Morphotyping and molecular analysis of ectomy- The plots were evaluated in June 2014. Height and corrhizas stem diameter (dbh) were measured for all surviving sap- For root analysis, five soil samples in each plot were lings. There were two plots where no trees have survived. collected in June 2014 to a depth of 20 cm using a 2.8 cm corer. Collected samples from each plot were pooled

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FUNGAL COMMUNITIES IN ROOTS OF SCOTS PINE AND NORWAY SPRUCE SAPLINGS GROWN /.../ D. KLAVINA, , ET AL. and analysed as one bulk sample. Samples were stored at shaking at room temperature at 150 rpm for 30 minutes + 4 ºC for up to two weeks prior to processing. (Alef and Nannipieri 1998). 0.1 ml aliquots from the seri- All woody roots were picked from soil samples and al dilutions of the suspensions were plated on the follow- rinsed under tap water. Coarse roots (larger than 2 mm ing media: peptone yeast extract media (5 g of peptone, in diameter) were discarded. Non-conifer roots, identi- 3 g of yeast extract, 15 g of agar, 1 l of distilled water) fied under a stereomicroscope Leica MZ-7.5 (Leica Mi- for bacteria; malt media (malt extract (d = 1.028), 18 g of crosystems, Wetzlar, Germany), were also discarded. The agar, 1 l of distilled water) for maltose degrading bacteria remaining fine roots were cut into 1 cm segments and and fungi. The assay was conducted in three replicates of evenly spread in Petri dishes with water. The number of prepared Petri dishes incubated at room temperature (20 ± living and dead root tips was determined, living root tips 2 ºC) for three days. After incubation, the numbers of col- were sorted into ECM and non-ECM, and all ECM root ony forming units (CFU) were counted (Vanderzant and tips were morphotyped. These analyses were done using Splittstoesser 1992) and their abundance was calculated a stereomicroscope. The distinction between the live and per one gram of soil (Alef and Nannipiri 1988). Dominant dead roots was made by evaluating the colour and elastic- fungal species in each Petri plate were identified to ge- ity of the central cylinder of fine roots (Vogt and Persson nus level according to their morphological characteristics, 1991). ECM fungal morphotypes were identified visu- which were examined under a microscope Leica DFC 490 ally according to colour, form and texture of ECM root (Leica Microsystems, Wetzlar, Germany). tips and the presence of rhizomorphs or external mycelia (Agerer 1986–2006). Data analysis One to five single root tips of each distinct morpho­ Stem parameters, numbers of fine roots and their bio- type per sample plot were separately placed in 1.5 ml cen- mass, soil chemical parameters and numbers of CFUs of trifugation tubes and stored at -20 ºC for molecular iden- soil microorganisms were tested for normality using the tification of fungal taxa. The Phire Plant Direct PCR Kit Shapiro and Wilk test (Royston 1982). All soil chemical (Thermo Fisher Scientific, Inc., Waltham, MA, USA) was parameters (soil pH, total C, total N, P, K, Ca, Mg) were used for direct PCR amplification from root tips (Velmala normally distributed. Other variables (fine root biomass et al. 2014). To amplify the fungal ITS region of rRNA and sapling stem parameters) met this assumption only genes, primers ITS1F (Gardes and Bruns 1993) and ITS4 when analysed separately for pine and spruce plots; for (White et al. 1990) were used. Sequencing was performed numbers of fine roots and numbers of CFUs of soil micro- by Macrogen Europe Inc. (Amsterdam, The Netherlands). organisms normality was obtained after logarithmic trans- Raw sequence data was analysed using the Seq- formation and separation of pine and spruce plot data. Man version 5.07 software from the DNASTAR package One-way analysis of variance (ANOVA) and Tukey’s (DNASTAR, Madison, WI, USA) and BioEdit v. 7.0.9.0 tests (Fowler et al. 1998) were performed to compare (Hall 1999). Databases at GenBank (Altschul et al. 1997) all those parameters among wood ash and control treat- and UNITE (http://unite.ut.ee/) (Kõljalg et al. 2013) were ments analysing pine and spruce plots together (in case used to determine the identity of sequences. The criteria of soil parameters) or separately for other parameters. A used for identification were the following: sequence cov- Tukey’s test was performed at confidence level α = 0.05. erage > 80%; similarity to species level 97–100 %, simi- The Wilcoxon test (Hollander and Wolfe 1999) was used larity to genus level 94–96 %. The sequences are avail- to compare fine root biomass, number of fine roots, stem able from GenBank under accession numbers KT182903- parameters and numbers of CFUs of soil microorganisms KT182923. between Scots pine and Norway spruce plots. Significant differences in mycorrhizal colonization Soil microbiological analysis of fine roots, relative abundance of living fine roots and Soil samples used for microbiological analysis were ECM fungal species between wood ash treatments and the collected in August 2014. A soil core 2.8 cm in diameter control were tested by chi-square (χ2) analysis calculated was used to obtain the samples down to 20 cm depth. Two from the actual number of observations (Mead and Curn- replicate cores were collected from each sample plot, ow 1983). As the total number of root tips analysed was pooled and analysed as one bulk sample. Soil samples large, the χ2 test was performed at confidence level α = were collected from the same plots as for root analysis. 0.0001. Data were statistically analysed using the R pro- In addition, two soil samples were taken from Scots pine gram (Vienna, Austria) (R Development Core Team 2011). plots where no trees had survived (resulting in 46 sam- Species richness and the Shannon diversity index ples, in total). Samples were immediately transported to (Shannon 1948) were calculated for each sample plot the laboratory and stored at + 4 ºC. in ComEcoPaC (Drozd 2010). ECM fungal community For each sample ten grams of soil were suspended structure was analysed using principal component analy- in 90 ml of sterile water in 500-ml Erlenmeyer flasks by sis (PCA) in CANOCO 4.5 (ter Braak and Smilauer 1998).

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The initial experimental design for pine included no significant differences in soil pH were observed among variants with similar amounts of wood ash applied (0.5 spruce plots. No significant differences among the treat- and 0.6; 1.0 and 1.2 kg m-2); to unify experimental design ments were observed also in total nitrogen (mean 27 g in pine and spruce we analysed data from those pine plots kg-1), carbon (434 g kg-1) and phosphorus (1.6 g kg-1), and together. plant available potassium (0.35 g kg-1), calcium (40.4 g kg-1) and magnesium (1.58 g kg-1). Results Scots pine saplings, in comparison to Norway spruce saplings were significantly taller (mean 3.7 ± 0.1 m versus Of the examined soil parameters, only pH differed 2.8 ± 0.1 m) and had larger stem diameter (dbh) (mean 3.3 significantly among treatments (Table 1). It showed high- ± 1.8 cm versus 2.0 ± 0.1 cm). No significant differences er values in pine plots fertilized with 1.0 to 2.0 kg m-2 of in height and diameter of pine saplings were observed wood ash than in control plantings of both tree species among wood ash and control treatments after ten grow- and spruce plantings fertilized with 1.2 kg m-2. However, ing seasons (Table 1). Spruce tree height was significantly

Table 1. Soil pH, fine root morphological parameters and abundance of soil microorganisms in samples from wood ash fertilized and control plots of Pinus sylvestris and Picea abies ten years after the application of wood ash (±SE)

Species Spruce Pine

0.5-0.6 k 1.0-1.2 1.5-2.0 Amount of wood ash applied Control 0.6 kg m-2 1.2 kg m-2 Control g m-2 kg m-2 kg m-2 Sapling growth No. of trees 107 105 129 31 29 19 23

Average height, m 2.6 ± 0.1 a 2.7 ± 0.1 ab 3.0 ± 0.1 b 3.7 ± 0.2 3.6 ± 0.3 3.4 ± 0.2 3.4 ± 0.2

Average DHB, cm 1.9 ± 0.1 2.0 ± 0.1 2.2 ± 0.1 3.1 ± 0.3 3.2 ± 0.4 2.9 ± 0.4 3.1 ± 0.4

Soil chemical and fine root analysis No. of samples 6 6 6 6 5 7 8 5.9 ± 0.1 Soil pH (H 0) 5.7 a 5.9 ± 0.1 ab 5.7± 0.1 a 5.7 ± 0.1 a 6.1 ± 0.2 b 6.2 ± 0.1 b 2 ab C org. / total 442 ± 5 405 ± 18 414 ± 13 450 ± 6 445 ± 18 433 ± 15 444 ± 11

P (g/kg) 1.64 ± 0.03 1.97 ± 0.18 1.92 ± 0.08 1.46 ± 0.10 1.45 ± 0.15 1.53 ± 0.15 1.52 ± 0.13

K (g/kg) 0.27 ± 0.02 0.22 ± 0.06 0.35 ± 0.01 0.43 ± 0.03 0.37 ± 0.04 0.41 ± 0.04 0.32 ± 0.06

Ca (g/kg) 41 ± 2 46 ± 2 33 ± 2 38 ± 1 41 ± 2 43 ± 3 44 ± 1

Mg (g/kg) 1.3 ± 0.1 1.9 ± 0.1 1.5 ± 0.1 1.4 ± 0.1 1.4 ± 0.1 1.6 ± 0.2 1.8 ± 0.1

Fine root biomass (kg m-2) * 10-2 5.6 ± 1.2 4.4 ± 1.3 3.9 ± 0.8 1.8 ± 0.4 2.1 ± 0.2 1.6 ± 0.4 1.9 ± 0.2

No. of dead fine roots per m2 * 104 7.3 ± 2.5 5.8 ± 2.4 6.2 ± 2.1 2.2 ± 0.6 2.1 ± 0.4 2.3 ± 0.3 2.3 ± 0.5

No. of living fine roots per m2 * 104 8.5 ± 1.7 6.0 ± 1.0 3.0 ± 0.8 4.7 ± 0.3 6.6 ± 1.5 3.7 ± 0.4 2.6 ± 0.8 Relative abundance 53.7 b 50.9 a 58.0 c 68.7 e 51.5 a 61.3 d 53.5 b of living fine roots (%) Mycorrhization (%) 89.8 ab 92.6 c 88.2 ab 90.3 ab 88.0 a 89.8 ab 91.2 bc

Soil microbial analysis No. of samples 12 12 12 12 14 14 16 Bacteria (CFU per g) * 106 3.7 ± 0.4 a 7.3 ± 0.9 b 8.7 ± 1.0 b 39.5 ± 14.3 cd 12.1 ± 3.8 c 40.8 ± 14.7 cd 42.3 ± 11.3 e Maltose degrading bacteria 3.9 ± 0.7 6.0 ± 1.3 6.6 ± 0.6 6.8 ± 1.5 7.3 ± 3.1 6.9 ± 1.3 19.8 ± 8.6 (CFU per g) * 105 Actinobacteria (CFU per g) * 105 1.7 ± 0.4 a 5.5 ± 0.7 b 8.1 ± 1.9 ab 12.3 ± 5.0 5.6 ± 1.3 4.6 ± 0.8 9.9 ± 2.5

Filamentous fungi (CFU per g) * 104 3.8 ± 1.1 4.8 ± 1.1 4.6 ± 0.9 4.5 ± 0.9 4.2 ± 0.9 4.4 ± 0.9 5.4 ± 0.8 * Within each row, different letters next to mean values indicate significant differences between treatments. If no significant differences are found among treatments, no letter is given.

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FUNGAL COMMUNITIES IN ROOTS OF SCOTS PINE AND NORWAY SPRUCE SAPLINGS GROWN /.../ D. KLAVINA, , ET AL. greater in the treatment with 1.2 kg m-2 of wood ash, com- and fertilized sample plots. None of these species was pared with that in the control (2.9 ± 0.1 m and 2.6 ± 0.1 found exclusively in control plots. However, some species, m, respectively), while stem diameter (dbh) did not differ such as Tuber sp., Tomentella coerulea and Tomentella sp. significantly. In general, spruce saplings showed higher 2, were found exclusively in fertilized plots. Total numbers survival rate than pine saplings. No trees survived in two of fungal species were similar between host species (13 on plots of Scots pine treated with 0.5 kg m-2 of wood ash. pine and 15 on spruce), but only five ECM species (Agari- Fine root biomass and numbers of fine roots were cales sp., Cenococcum sp., Inocybe sindonia, Tomentella significantly lower in pine versus spruce plots (p < 0.05). sp. 2 and Tuber anniae) were found in both host species. Fine root biomass, numbers of living fine roots and num- Shannon diversity index of root-associated fungal bers of dead fine roots did not differ significantly among species for both host species was higher in plots with a wood ash treatments and the control for either pine or medium amount (0.5 kg m-2) of wood ash fertilization. spruce (Table 1). For both tree species, relative abundance The dominant species Agaricomycetes sp. and Amphine- of living fine roots was lower in sites fertilized with wood ma byssoides were less abundant in fertilized sites, while ash in low amounts (0.5 to 0.6 kg m-2). Spruce plots of unidentified Lactarius, Amphinema and Agaricales spe- this treatment had higher levels of mycorrhizal coloniza- cies were more abundant. tion than other treatments, while pine saplings showed the The relative abundance of fungal species differed sig- opposite effect – lower mycorrhizal colonization in plots nificantly between Norway spruce and Scots pine. Ecto- fertilized with low amounts of wood ash. mycorrhizal fungi Amphinema byssoides and Lactarius cf. Numbers of bacterial CFU were higher in plots with deliciosus var. deterrimus were dominant on spruce, while Scots pine than in those with Norway spruce (p < 0.05), and Cadophora finlandica and Agaricomycetes sp. were domi- in plots, where wood ash was applied in higher amounts nant on pine. The relative abundance of some ECM species (Table 1). Abundance of maltose degrading bacteria did differed significantly between fertilized and control plots: not differ among wood ash treatments and control plots. In Cadophora finlandica and an unidentified Cenococcum spruce plots, actinobacteria were more abundant in wood species were more abundant in control samples, while an ash fertilized plots than in control plots, while in pine plots unidentifiedTuber species and Wilcoxina rehmii were more no significant differences between wood ash treatments abundant in wood ash fertilized sites. Principal component and control were observed (Table 1). Abundance of fila- analysis (PCA) clearly showed these trends (Figure 2). The mentous fungi CFU in soil samples was similar in all treat- first principal component of the PCA ordination explained ments. Taxanomical identification indicated dominance of 75.3 % of the variation in root-associated fungal commu- Penicillium, Mortierella and Verticillium fungal genera in nity composition and separated communities on pine and all soil samples. Colletotrichum and Paecilomyces tended spruce (Figure 2). The second component explained 14.0% to be more abundant in fertilized plots of both tree spe- of the variation in root-associated fungal community com- cies. Cladosporium was approximately five times more position and showed a certain difference between the ash abundant on spruce sample plots, while Trichoderma spe- and control treatments for each tree species. cies were approximately ten times more abundant in pine sample plots. Species from genera Botrytis, Fusarium, Geo­trichum and Pythium were identified in some samples. Sequencing of the ITS region of fungal rRNA genes from 80 root tips representing each of 14 observed mor- photypes resulted in 50 sequences of basidiomycetes (11 species) and 30 sequences of ascomycetes (10 species) (Table 2). Most sequenced species were ectomycorrhizal fungi, but some species, such as two unidentified ascomy- cetes and one species from the family Nectriaceae were most probably saprotrophic species. The most frequently sequenced ectomycorrhizal species were the basidiomy- cetes Amphinema byssoides and Lactarius cf. deliciosus var. deterrimus (each one constituted 12.5 % of all se- quences). The truffle species Tuber anniae was also com- mon (11 % of all sequences). Figure 2. Principal component analysis (PCA) of fungal taxa The number of ECM species did not differ signifi- in wood ash fertilised and control plots of Norway spruce and cantly between different treatments or between different Scots pine. Symbols indicate treatments and the tree species: host species. Most of the ECM species were represented circle – Norway spruce; square – Scots pine; not filled – con- by more than one sequence and occurred in both control trol; grey filled – wood ash fertilized plots

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Table 2. Fungal species and their relative abundance (%) in wood ash fertilized and control plots of Norway spruce and Scots pine in wood ash fertilized and control plots ten years following addition of wood ash

GenBank Species accession Spruce Pine Total No.** 0.6 1.2 0.5-0.6 1.0-1.2 1.5-2.0 Amount of wood ash applied Control Control kg m-2 kg m-2 kg m-2 kg m-2 kg m-2

No. of root tips analysed 5616 4124 4280 1945 2602 2867 2329 23763

Shannon diversity index 1.85 2.27 1.30 1.67 2.18 1.70 1.34 2.94

Ascomycota

Ascomycota sp. 1 (SH214904.07FU)* KT182903 - 0.8 - - - - - 0.1

Ascomycota sp. 2 (SH202705.07FU) KT182904 0.5 ------0.1 Cadophora finlandia KT182905 - - - 7.7 c*** 2.2 b 1.8 b 0.5 a 1.1 (SH214265.07FU) Cenococcum sp. (SH214459.07FU) KT182906 0.6 a 0.3 a 0.1 a 1.5 b 0.2 a 0.5 a 4.9 c 0.9

Nectriaceae sp. (SH182800.07FU) KT182907 - - 0.6 - - - - 0.1

Lachnum sp. (SH201605.07FU) KT182908 - - - - - 3.5 - 0.4

Tuber cf. anniae (SH202491.07FU) KT182909 0.2 a 0.3 a 2.1 b 0.3 a 2.5 b 9.0 c 1.0 b 2.0

Tuber sp. (SH216303.07FU) KT182910 - - - - 2.7 b - 0.2 a 0.3

Wilcoxina sp. (SH194157.07FU) KT182911 6.7 b - 1.0 a - - - - 1.8

Wilcoxina rehmii (SH211927.07FU) KT182912 - - - 1.3 a 8.1 b 3.0 a 7.6 b 2.1

Basidiomycota Agaricales sp. (cf. Hebeloma KT182913 - 13.2 b 2.0 a - - - 2.5 leucosarx ) (SH215995.07FU) Agaricomycetes sp. (SH206583.07FU) KT182914 - - - 68.0b 60.3a 70.1c 77.8d 28.2 Amphinema byssoides KT182915 64.9b 46.7a 74.5c - - - - 36.9 (SH197943.07FU) Amphinema sp. (SH197945.07FU) KT182916 0.4 a 4.0 b 0.2 a - - - - 0.8

Inocybe sindonia (SH176685.07FU) KT182917 2.5 b - 0.5 a - 4.2 c - - 1.1 Lactarius cf. deliciosus var. deterrimus KT182918 4.5 b 10.4 c 2.3 a - - - - 3.3 (SH220113.07FU) Tomentella coerulea KT182919 - - - - 7.3 b - 2.7 a 1.1 (SH177784.07FU) Tomentella sp. 1 (SH177803.07FU) KT182920 0.7 ------0.2

Tomentella sp. 2 (SH177794.07FU) KT182921 - 4.6 b - - - 1.1 a - 0.9

Tomentella sp. 3 (SH189390.07FU) KT182922 ------3.4 0.3

Tomentella sp. 4 (SH177825.07FU) KT182923 5.3 b - 1.4 a - - - - 1.5

Unidentified morphotypes 13.6 19.7 17.2 19.3 12.6 11.1 1.9 14.3

* Reference species hypothesis (Kõljalg et al. 2013) is given in parenthesis. ** The homology of our sequences to the GenBank reference sequences was 97–100 %. *** Different letters next to relative abundance of each species indicate significant differences among treatments (chi-square test p-value < 0.0001).

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Discussion and conclusions ment for promoting stem growth of pine saplings, when evaluated one year after treatment (Gaitnieks et al. 2005). The observed differences in soil pH between control Our study also indicated that effects of wood ash applica- and fertilized plots of pine plots 10 years after wood ash tion in low amounts (0.5 to 0.6 kg m-2) are positive, espe- application indicate a long-lasting neutralizing effect of cially regarding Shannon diversity of ECM communities. wood ash in the organic soil layer, as described by other This might be due to reduced abundance of dominant spe- authors (Bramryd and Fransman 1995, Saarsalmi et al. cies Amphinema byssoides (on spruce) and Agaricomy- 2001, Moilanen et al. 2002). In contrast to results pre- cetes sp. (on pine) in those plots. In addition, a higher viously reported by Arvidsson and Lundkvist (2003), no colonization of roots by mycorrhizal fungi on spruce sap- significant difference in soil pH was observed between lings was observed in plots fertilized with wood ash 0.6 treatments in spruce plots. This could be explained by a kg m-2. Since Amphinema byssoides is a frequent colo- higher survival rate and density of spruce in experimental nizer of dead wood substrates (Veerkamp et al. 1997), its plots resulting in greater litter input in comparison with high abundance on fine roots of other treatments might be pine. It could also be related to species differences associ- related saprotrophic activity and not only to formation of ated with the significant impact of Norway spruce litter on mycorrhizal symbioses. Some Agaricomycetes sp. refer- soil properties that have been described by other authors ence sequences in the GenBank database were also as- (Bonifacio et al. 2008). The lower stem growth rate and signed to the genus Amphinema and therefore the ecology higher fine root biomass and abundance in spruce plots of these species hypothetically might be similar to that of might also be due to higher tree density in spruce plots A. byssoides. compared to pine plots. In conclusion, our data provide some evidence of Increased abundance of bacteria and actinobacteria a long-term effect of wood ash fertilization on soil pH, and no effect on abundance of fungi after liming has also ECM community composition and abundance of soil bac- been described by other authors (Frostegård et al. 1993). teria in both Scots pine and Norway spruce plots, at the We observed a higher number of bacterial CFUs in pine same time suggesting that the treatment might have ef- plots than in spruce plots. This can be explained by higher fects on the functioning of forest ecosystems. soil pH in fertilized pine sites, as higher soil pH can pro- mote bacterial growth (Frostegård et al. 1993; Bååth and Acknowledgements Anderson 2003). The higher abundance of Trichoderma species in pine sites and fertilized plots could also be as- This research was funded by the European Regional sociated with increased soil pH (Jackson et al. 1991). Development Fund (ERDF) under the Global Grant mea- We observed significant differences in ECM com- sure, project no. VP1-3.1-ŠMM-07-K-02-001 and ERDF munity composition between host species, which is in ac- project No. 2013/0065/2DP/2.1.1.1.0/13/APIA/VIAA/034. cordance with previous studies (e.g. Klavina et al. 2013). We are grateful to the Natural Resources Institute Finland The observed differences in fungal species abundance be- (former Finnish Forest Research Institute) for the labora- tween fertilized and control sites are consistent with pre- tory facilities and support in the laboratory work. Our vious studies showing species-specific changes in ECM special thanks are given to colleagues from LSFRI “Si- fungal community composition after forest liming (Jons- lava”, who established this experiment and were involved son et al. 1999, Kjøller and Clemmensen 2009) and wood in monitoring and sampling (A. Brūvelis, P. Zālītis, A. In- ash application (Klavina et al. 2015). Amphinema bys- driksons and others). soides and Tuber species are favoured by soil conditions with more neutral pH, and they can thus dominate after References liming or wood ash treatment (Qian et al. 1998, Erland and Taylor 2002, Kjøller and Clemmensen 2009, Klavina Agerer, R. 1986-2006. Colour atlas of ectomycorrhizae. Einhorn- Verlag, Schwäbisch Gmünd, München, Germany. et al. 2015). However, our data indicate that abundance Alef, K. and Nannipiri, P. (eds.) 1988. Methods in applied soil mi- of those species may strongly depend on amount of wood crobiology and biochemistry. Acad. Press., p. 20–100. ash applied. Greater abundance of Tomentella coerulea Altschul, S.F., Madden, T.L., Schäffer, A.A., Zhang, J., Zhang, and Hebeloma cf. leucosarx in wood ash treated plots Z., Miller, W. and Lipman, D.J. 1997. Gapped BLAST and PSI-BLAST: a new generation of protein database search pro- than in control was observed in this and previous studies grams. Nucleic Acids Research 25: 3389–3402. (Klavina et al. 2015). In contrast, Cadophora finlandia in Andersson, S. and Söderström, B. 1995. Effects of lime (CaCO3) both studies was tend to be more abundant in control sites. on ecto-mycorrhizal colonization of Picea abies (L.) Karst. Application of wood ash amounting up to 1 kg m-2 seedlings planted in a spruce forest. Scandinavian Journal of Forest Research 10: 149–154. are mostly used in experiments and practical forestry (Au- Aronsson, K.A. and Ekelund, N.G.A. 2004. Biological effects of gusto et al. 2008). Application of wood ash in amounts wood ash application to forest and aquatic ecosystems. Jour- lower than 1 kg m-2 has been observed to be the best treat- nal of Environmental Quality 33: 1595–1605.

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2016, Vol. 22, No. 1 (42) ISSN 2029-9230 3533 BALTIC FORESTRY BLACK-HEADED GULL (LARUS RIDIBUNDUS L.) AS A KEYSTONE SPECIES IN THE LAKE /.../ A. LEITO ET AL. Black-headed Gull (Larus ridibundus L.) as a Keystone Species in the Lake Bird Community in Primary Forest-Mire-Lake Ecosystem

AIVAR LEITO 1, *, MEELIS LEIVITS 2, AGU LEIVITS 3, JANAR RAET 1, RAYMOND WARD 1, 4, INGMAR OTT 1, HARDI TULLUS 5, RAUL ROSENVALD 5 , KAI KIMMEL 6 AND KALEV SEPP 1,** 1 Institute of Agriculture and Environmental Sciences, Estonian University of Life Sciences, 5 Kreutzwaldi Str., 51014 Tartu, Estonia 2 Department of Geography, Institute of Ecology and Earth Sciences, University of Tartu, 46 Vanemuise Str., 51014 Tartu, Estonia 3 Environmental Board, 7a Narva St., 15172 Tallinn, Estonia 4 School of Environment and Technology, University of Brighton, Cockcroft Building, Lewes Road, 11 Brighton, BN2 4GJ, United Kingdom 5 Institute of Forestry and Rural Engineering, Estonian University of Life Sciences, 5 Kreutzwaldi St., 13 51014 Tartu, Estonia 6 Environmental Board, Jõgeva-Tartu Region, 2 Aia Str., 48306 Jõgeva, Estonia * Corresponding author: Tel: +3725153995; E-mail: [email protected] ** Corresponding author: Tel: +3727313777; E-mail: [email protected]

Leito, A.,* Leivits, M., Leivits, A., Raet, J., Ward, R., Ott, I., Tullus, H., Rosenvald, R., Kimmel, K. and Sepp, K.**. 2016. Black-headed Gull (Larus ridibundus L.) as a Keystone Species in the Lake Bird Community in Primary Forest- Mire-Lake Ecosystem. Baltic Forestry 22(1): 34-45.

Abstract

Within animal communities the loss of a single keystone species can lead to substantial change, or in extreme cases, commu- nity collapse. This phenomenon has been documented in different communities and habitats but has not been widely investigated in bird communities. We studied the long-term dynamics of breeding birds in a medium-sized hemiboreal lake that is situated within a large primary forest-mire-lake ecosystem in central-east of Estonia. The aim of this 25 year study was to determine whether the black-headed gull, Larus ridibundus, acts as a keystone species in the bird community and what was the effect of the loss of this species. Results revealed large changes in the bird community similar to those that would occur in a fragile system in response to keystone species loss, confirming our theory. Mallard Anas platyrhynchos, common pochard Aythya ferina, tufted duck Aythya fuligula, great crested grebe Podiceps cristatus, red-necked grebe Podiceps grisegena, Eurasian marsh harrier Circus aeruginosus, spotted crake Porzana porzana, coot Fulica atra, and common tern Sterna hirundo were most closely related to the abundance of black-headed gull. During the study period there was little change in habitat quality or extent. It is unclear as to the causes of the gull colony collapse; however, landscape-level changes in feeding areas and agricultural land could be a reason. We conclude that further study of keystone species and fragile communities in different habitats and ecosystems is important to ascertain which species and communities are most likely to be affected in the event of the loss of a keystone bird species.

Key words: Keystone species, bird community, forest-mire-lake ecosystem, fragile system, species richness.

Introduction al. 2012, Saurola et al. 2013, Skorka et al. 2014, Arzel et al. 2015). Natural fluctuations in those factors are usually Lake bird communities are affected by the proper- long-term (Belleau et al. 2011), although human influence ties of the lake and its surroundings as well as by the re- can accelerate these processes (Long et al. 2007) and can gional species pool (Sala et al. 2000, Dawson et al. 2011, directly or indirectly, positively or negatively affect lake Hilli-Lukkarinen et al. 2011, Vīksne et al. 2011, Kajzer et bird communities (Robledano et al. 2010, Hilli-Lukkarin-

2016, Vol. 22, No. 1 (42) ISSN 2029-9230 3436 BALTIC FORESTRY BLACK-HEADED GULL (LARUS RIDIBUNDUS L.) AS A KEYSTONE SPECIES IN THE LAKE /.../ A. LEITO ET AL. en et al. 2011). Several studies have predicted population and peat deposition (Valk 1988, Robroek et al. 2007, decreases and localised extinctions in a wide variety of Kimmel 2009, Smiljanić et al. 2014). The aim of the pres- habitats and animal species as a result of climate change, ent study was to analyse the response of the black-headed the overexploitation of natural resources, and habitat gull on breeding bird community species composition, fragmentation (including woodland) (Hanski 2000, My- richness, diversity, dissimilarity, turnover rate, and abun- ers and Worm 2003, Thomas et al. 2004, Seppälä et al. dance to determine whether the black-headed gull acts 2009, Dawson et al. 2011, Cahill et al. 2012). The mecha- as a keystone species and whether the crash of the gull nisms that enable the coexistence of interacting species colony would cause the collapse of the bird community can break down when a species is lost from a community, in a hemiboreal lake. For this purpose, we used the total which leads to a sequence of secondary extinctions (Eb- counts of breeding birds at natural mesotrophic Lake End- enman and Jonsson 2005). Such secondary extinctions or la in Estonia due to the availability of a long term dataset coextinctions have been previously observed in several recorded between 1987 and 2012. A limited number of natural communities, and, in the worst case, the loss of a case studies have analysed the effect of black-headed gull single species can lead to the collapse of the community colonies on the bird community based on valid long-term (Paine 1966, Estes and Palmisano 1974, Koh et al. 2004, total counts of all breeding bird species in a lake (e. g. Ebenman and Jonsson 2005). A question is thus posed ‘are Vīksne et al. 2005, 2011). there particular types of species (keystone species) whose We hypothesised that clear differences in commu- loss is likely to have serious effects on the continued exis- nity parameters would be detected during periods charac- tence of other species and hence on the long-term persis- terised by the presence and absence of the black-headed tence of the community?’ Furthermore, to what extent is gull colony. We predicted the greatest differences in total the keystone status and vulnerability of a species context- abundance and fewer changes in abundance and the rela- dependent? The answers to these questions are crucial to tive share of some bird species following the disappear- the prediction of the response of ecological communities ance of black-headed gull colony. The confirmation of to species loss (Ebenman and Jonsson 2005). It is there- these predicted changes indicates that this type of com- fore of great importance to ascertain which species and munity is in fact a fragile system that can break down communities are most likely to be threatened. or markedly change as a result of the loss of a keystone The focus of this study was on the relationships be- species, such as the black-headed gull, which triggers a tween different bird species, particularly protective nest- cascade of shifts in the community, as described before ing associations, between the black-headed gull Larus in different ecosystems (Koh et al. 2004, Ebenman and ridibundus and the waterfowl that have a crucial role in Jonsson 2005, Woodward et al. 2005, Quinn and Ueta the determination of the species composition, diversity, 2008). The total population of black-headed gull, as well and abundance of the breeding bird community in boreal as common pochard Aythya ferina, tufted duck Aythya fu- and sub-boreal eutrophic lakes (Väänänen 2000, 2011, ligula, and several surface-feeding ducks that are closely Quinn and Ueta 2008, Vīksne et al. 2010, 2011, Nummi associated with gull colonies, have declined in Estonia, et al. 2012). Most “protected” associates on this type of Finland, Latvia, Lithuania, over recent decades (Elts et lakes are found in the Anseriformes, particularly ducks, al. 2009, 2013, Vīksne et al. 2010, 2011, Väänänen 2011, and most “protective” associates originate from the Char- Pöysä et al. 2013, Estonian State Environmental Monitor- adriiformes, particularly gulls and terns (Quinn and Ueta ing Programme 2015). In addition, due to this simultane- 2008, Vīksne et al. 2011, Väänänen 2011). In addition to ous decline, it is important to understand the relationships lakes, protective nesting associations in birds have been of these species in the community and identify the most described in many other habitats, such as forest, farmland, likely associated reasons for their local decline and ex- island, and tundra, with different protected and protective tinction. species (reviewed in Quinn and Ueta 2008). Although various nesting associations in birds and other animals Material and methods have long been recognised, these associations continue to provide many novel research opportunities because it There are two main approaches that can be used to is a complicated field with a great diversity of strategies perform a community viability analysis, dynamic or static to limit predation (Popham 1897, Durango 1954, Haemig analysis, each of which has advantages and disadvantages 2001, Vīksne et al. 2011). and require different types of community data (Ebenman This study took place in the Endla forest-mire-lake and Jonsson 2005). In a dynamic analysis, selected for use ecosystem, in Estonia. Predominant environmental vari- in this study, changes in species population over time and ables affecting the wider study area are precipitation/ the indirect effects that these changes have on the abun- evaporation and their impacts on lake, wetland and forest dance of other species are taken into account. A dynamic water levels influencing plant communities, tree growth community analysis can be applied to natural commu-

2016, Vol. 22, No. 1 (42) ISSN 2029-9230 3735 BALTIC FORESTRY BLACK-HEADED GULL (LARUS RIDIBUNDUS L.) AS A KEYSTONE SPECIES IN THE LAKE /.../ A. LEITO ET AL. nities if a method can be found to estimate the intrinsic 10–150 m wide belt of emergent vegetation and quagmire growth rates of species and the strength of the interactions (Figure 1). There are six mineral islets (area 0.7–29.2 ha) among species. Two possible methods to estimate these in the lake, which exhibit a total area of 42 ha. There are parameters are to infer these from the body size of species also floating vegetation “islets” covered with reeds and using allometric scaling relationships and to estimate the other aquatic macrophytes and single willow shrubs. The parameter using numerical abundance data and the equi- main colony was situated on one of these floating islets librium assumption (Yodzis and Innes 1992, Jonsson and “Gulls islet”, with an area of 14 ha. The lake is shallow Ebenman 1998, Emmerson and Rafaelli 2004, Woodward with an average depth of 1.6 m and a maximum depth of et al. 2005). 2.4 m. Lake Endla is a mixotrophic (dyseutrophic) lake with moderate nutrient content, medium water hardness Study area and high organic content (Mäemets 1977). Lake Endla Lake Endla is located in the central-east of Estonia freezes over from December to April and is colonised (central coordinates: 58°51’N and 26°11’E) in a hemi- anew each spring by migrating birds. boreal mixed forest zone (Hämet-Ahti 1981). The lake is Altogether 84 species of vascular macrophytes have situated in the southern margin of the Endla Mire System, been recorded in Endla Lake (Viljasoo 1959, Mäemets the majority of which is composed of open and semi-open 1968, Ott 2011, I. Ott, H. Mäemets and K. Palmik pers. pool rich pine bogs, pine forest and wooded mires forming comm.). The most abundant and important aquatic mac- a large forest-mire-lake ecosystem. The total area of Lake rophytes for nesting birds were Phragmites australis, Eq- Endla is 482 ha and the catchment area is 43,300 ha, 42% uisetum fluviatile, Carex spp., Schoenoplectus lacustris, of which is covered by forests and 21% both by bogs and Menyanthes trifoliata and Nymphaea sp. The lake has a arable land (EELIS 2015). The area of open water of the high fish productivity (10 kg/ha) and contains nine spe- Lake Endla is 287 ha and the total area of quagmire and cies, providing an important food resource for the bird water-growing reed bed 153 ha. The lake is edged with a population. The most abundant fish species is Rutilus

Figure 1. Location of the study area, main habitats, and black-headed gull colonies

2016, Vol. 22, No. 1 (42) ISSN 2029-9230 3638 BALTIC FORESTRY BLACK-HEADED GULL (LARUS RIDIBUNDUS L.) AS A KEYSTONE SPECIES IN THE LAKE /.../ A. LEITO ET AL. rutilus, followed by Perca fluviatilis and Tinca tinca records of singing birds, and records of non-singing birds (Mäemets 1968). In Lake Endla fish species abundance that displayed behaviour consistent with probable or con- and diversity has undergone minimal change during the firmed nesting according to the instructions of the Esto- study period (Ott 2011). In addition to fish inhabiting nian Bird Atlas (Renno 1993) were located on a map. Spe- Lake Endla amphibian prey species are Rana arvalis (the cifically, breeding pairs of duck were defined by identify- most numerous), Rana temporaria, Bufo bufo and Rana ing a nest, small chicks or sessile pair (a female and male kl. esculenta (Rannap 2012). The Eurasian marsh harrier acting together). Based on these data, breeding pairs were Circus aeruginosus, white-tailed eagle Haliaeetus albi- defined and marked on the survey map. More specifically, cilla, and hooded crow Corvus cornix are the most com- gull colonies were counted based on single birds at the mon birds of prey in the lake. The Eurasian marsh harrier moment of take-off from nests, and the number of pairs nests in reed beds at the lake, hooded crow in trees on calculated by halving the count. Large colonies were par- the lake shore and islands. One pair of white-tailed eagles tially counted and totals estimated. Nocturnal birds were nests in the forest close to the lake. In addition, a single counted passively by song and other voices. All counts common raven Corvus corax preys on duck and gull eggs were recorded between 15:00 to 24:00 and were continued and chicks within the area. Nyctereutes procyonides and the following morning from 5:00 to 11:00. As a result, the Mustela vison are the most important predator mammals peak activity periods of both diurnal and nocturnal bird of ground-breeding bird’s nests in the lake. species were recorded. All surveys were performed by the Lake Endla is predominantly surrounded by pine same observer, Aivar Leito. The single mapping method pool-bogs, pine forests and paludified forests (Fig. 1 and was used in place of the two-time censuses that are usu- Table 1). The nearest inhabited farm is situated 3 km south- ally currently recommended in northern Europe (Koskim- east of the lake. Extensive drainage of peatland and forest ies and Väisänen 1991, Vesilintujen laskentaohjeet 2013) at the edges of the Endla mire system was carried out be- as this study commenced prior to the publication and wide tween the 1950s and 1980s influencing water levels in the application of this methodology. The census method was lake during these periods (Masing 1957, Valk 1988, Kim- not changed during this study to ensure uniform and com- mel 2009). Lake Endla is one of the core areas of the Endla patible data from all of the censuses. The census data and Nature Reserve (area 10,161 ha), which was established in the number of species are provided in the Appendix. 1985 and is a part of the Endla Ramsar Site and the Natura 2000 area (EELIS 2015, Ramsar Secretariat 2015). Data analysis Mean numbers (M), standard deviations (SD), coef- Table 1. Main biotopes in hectares within 500 m of Lake Endla ficients of variation (CV %), and trends in the numbers between 1989 and 2006 of breeding bird species were calculated using the census Biotope 1989 2006 Change data recorded between 1987 and 2012 (Appendix 1). The Mann-Kendall trend test (McLeod 2011) was used to as- Forest 254 213 -41 sess the existence and significance of monotonic trends Pine pool-bog 278 319 +41 in the time series. TRIM, as a widely used and accepted loglinear Poisson regression method was used for the Wooded mire 15 16 +1 time series analysis of count data (Pannekoek and van Stream 3 2 -1 Strien 2001). The overall trend estimates between 1987 and 2012 was calculated using the TRIM type 2 software Other 7 7 and provided in the multiplicative slope and according to Total area 557 557 0 the trend class (Table 2). All possible changepoints were used to estimate the model. The first year of the time se- Bird counts ries was chosen as the base-year for all species, except Breeding birds were counted in the last days of May those with zero-abundance during that year. For species in 20 of the years over the 25-year period between 1987 with zero counts in the first year, the first year in the time and 2012. No surveys were conducted during 1990, 1992, series with positive counts was chosen as the base-year. 1993, 1995, 2010 and 2012 due to financial constraints. Margalef’s evenness index (MG) and Shannon-Wiener’s The end of May is an optimal time for single counts as diversity index (H’) were then calculated. Margalef’s in- the lake is no longer frozen and the vegetation canopy is dex was calculated using the following function: still quite open facilitating visibility. Additionally, all of the bird species have started to nest by late May. Breeding MG = (Si-1) / ln Ni, pairs were mapped (scale = 1:10,000) by boat using a per- manent census transect covering the whole lake, with the where Si is the number of species and Ni is the num- exception of the mineral islets (Figure 1). Nest findings, ber of species i (Magurran 1988, Oksanen et al. 2011).

2016, Vol. 22, No. 1 (42) ISSN 2029-9230 3937 BALTIC FORESTRY BLACK-HEADED GULL (LARUS RIDIBUNDUS L.) AS A KEYSTONE SPECIES IN THE LAKE /.../ A. LEITO ET AL.

Table 2. Multiplicative slope estimates of TRIM type 2 mod- The species turnover rate (STO) was then estimated (Table els with changepoints 1 and 14 (years 1987 and 2000) and the 2) using the following function: Wald test for the significance of the changepoint at year 2000. Z = Wald test statistic; sl8799 = multiplicative slope for the STO = 0.5 (I + E), period 1987–1999 (gull colony was present); sl0012 = multipli- cative slope for the period 2000–2012 (gull colony was absent). where I is the number of new species and E is the The bird species are shown as 3+3 first letter acronyms of the number of extinct species (Schoener 1988, Hilli-Lukkar- full Latin name and in alphabetical order. Significance (P) inen 2011). If the dataset has missing counts, the imputed levels: *** < 0.001, ** < 0.01, * < 0.05, and ∙ < 0.1. The spe- counts given by TRIM were used to calculate the values cies without any values (empty spaces) were too occasional for of E and I. Community turnover rate was calculated as the estimation of the trend slopes the percentage of dissimilarity. The dissimilarity of the communities in different years was measured using the Species sl8799 se8799 sl0012 se0012 Z P-value P-level percentage dissimilarity index (PDI): Acraru 0.99 0.02 0.96 0.03 0.3 0.581 Acrsch 1.11 0.05 1.01 0.03 1.7 0.188 PDI = 1 – PS, Acrsci 1.26 0.09 1.02 0.04 5.5 0.019 *

Acthyp 0.71 0.07 1.27 0.17 7.3 0.007 ** where PS = ∑ min (pi1, pi2, …, pin) and p is the pro- portion of pairs of species i in the previous and the follow- Anacre 0.84 0.04 0.95 0.10 0.9 0.354 ing years (Suhonen et al. 2009, Hilli-Lukkarinen 2011) Anapen 0.92 0.05 0.95 0.09 0.1 0.761 (Table 3). The Mann-Whitney U test was used to estimate Anapla 0.90 0.02 0.78 0.06 2.3 0.127 the presence-absence effect of the black-headed gull col- Anaque 1.03 0.06 0.77 0.09 3.7 0.055 ∙ ony on the numbers of different bird species (Table 4). In Aytfer 1.10 0.05 0.45 0.13 8.5 0.004 ** addition to the comparison of species abundance related Aytful 1.10 0.06 0.49 0.15 6.5 0.011 * to the presence/ absence of the gull colony, species popu- lation trends were analysed at different periods. Trends in Botste 0.94 0.03 1.06 0.04 3.5 0.060 ∙ the numbers of breeding pairs in the periods characterised Buccla 0.98 0.04 0.92 0.06 0.3 0.569 by the presence/absence of the gull colony were calcu- Chlnig 1.10 0.06 0.80 0.07 6.2 0.013 * lated with TRIM using a two changepoint model. The first Ciraer 1.06 0.01 0.93 0.01 41.9 0.000 *** changepoint was the initial year of the data series, and the Cygcyg 1.20 0.32 1.27 0.11 0.0 0.857 second changepoint the year 2000, as this year marked the period without the gull colony (Table 2). All of basic Cygolo 1.31 0.09 1.08 0.03 5.4 0.020 * analyses (S, SD, CV, H’, MG, STO, and PDI) were made Embsch 1.14 0.03 1.03 0.02 7.7 0.006 ** using R (R Development Core Team 2010). Fulatr 0.98 0.04 0.78 0.08 3.7 0.055 ∙ Biotopes were described for Lake Endla and a 500 m Galchl 1.22 0.14 0.64 0.13 5.9 0.015 * buffer zone from the shoreline to describe the surrounding Galgal 1.01 0.04 0.90 0.06 1.5 0.222 area. Estonian Basic map and state forest database from Gavarc 1.07 0.11 0.98 0.10 0.2 0.631 2006 were used for habitat characterising (Figure 1). To identify changes in biotope during the study period anoth- Grugru 1.05 0.02 1.06 0.02 0.1 0.831 er geographic dataset was created and used based on the Lararg 0.95 0.05 0.75 0.12 1.6 0.207 Estonian Cadastral map from the 1980’s. To characterize Larcan 0.98 0.03 1.00 0.05 0.1 0.792 the changes in the agricultural land, we used FAOSTAT Larmin 1.10 0.13 0.48 0.30 1.6 0.210 (2014) database. Larrid 0.93 0.03 0.45 0.16 4.0 0.045 * Loclus 1.32 0.08 0.97 0.03 16.7 0.000 *** Results

Motalb 1.04 0.12 0.94 0.13 0.2 0.654 Changes in landscape Motfla 0.86 0.04 1.08 0.08 3.8 0.053 ∙ According to our measurements the area and relative Podcri 0.99 0.03 0.71 0.06 10.0 0.002 ** share of the pine pool-bog and wooded mire together (+41 Porpar 1.13 0.17 1.22 0.09 0.2 0.687 ha; 7.4 % of total area 557 ha) has increased and the area Porpor 1.06 0.04 0.73 0.06 13.6 0.000 *** and relative share of the forest (–41 ha; 7.4 % of total area 557 ha) has decreased in the 500 m zone around the Ralaqu 0.96 0.03 1.11 0.04 6.2 0.013 * Lake Endla from 1989 to 2006 (Table 1). The main pro- Stehir 0.94 0.04 0.86 0.07 0.8 0.363 cess leading to the decrease in forest area in the Endla Trigla 1.05 0.03 0.98 0.04 1.1 0.293 forest-mire-lake ecosystem has most likely been the natu-

2016, Vol. 22, No. 1 (42) ISSN 2029-9230 3840 BALTIC FORESTRY BLACK-HEADED GULL (LARUS RIDIBUNDUS L.) AS A KEYSTONE SPECIES IN THE LAKE /.../ A. LEITO ET AL.

Table 3. Relative change in the breeding bird community at Lake Endla between 1987 and 2012. E = number of extinct species; I = number of new species; STO = species turnover rate; PDI = percentage dissimilarity of the bird community; H’ = Shannon-Wiener’s index; MG = Margalef’s in- dex. The calculations are based on the imputed counts (TRIM)

Year E I STO PDI H' MG 1987 0.18 3.38 1988 3 2 2.5 0.01 0.23 3.32 1989 3 2 2.5 0.01 0.19 3.11 1990 0 4 2.0 0.01 0.21 3.55 Figure 2. Area of arable land and permanent crops in Estonia 1991 5 2 3.5 0.01 0.25 3.21 in 1992–2012 1992 3 6 4.5 0.01 0.28 3.56 Trends and community structure 1993 1 0 0.5 0.01 0.33 3.46 At Lake Endla, 46 bird species from eight orders 1994 3 1 2.0 0.02 0.41 3.25 bred between 1987 and 2012 (Appendix 1). In any given 1995 1 5 3.0 0.01 0.43 3.73 year, 17–32 species (mean ± SD = 26.75 ± 4.22; CV = 1996 4 2 3.0 0.01 0.48 3.53 16 %; n = 20 years) were observed to breed. There was a significant negative linear trend in the number of spe- 1997 3 4 3.5 0.01 0.44 3.61 cies during the study period (Mann-Kendall trend test, τ = 1998 5 1 3.0 0.01 0.40 3.19 –0.625, P < 0.001, n = 20). 1999 5 6 5.5 0.07 0.72 3.64 At the beginning of the census period, the turnover

2000 6 4 5.0 0.57 2.15 4.27 rate was STO1987 = 0.86 ± 0.94 (E ± SE), and, at the end of

2001 5 1 3.0 0.42 1.95 3.96 the census period, STO2009 = 5.72 ± 0.94 (E ± SE). Thus, 2002 2 6 4.0 0.65 1.53 4.06 there was a substantial increase in the turnover rate be- tween 1987 and 2009 (ΔSTO = 4.87 ± 1.87). Assuming a 2003 10 2 6.0 0.51 1.89 3.06 linear increase in the turnover rate, we calculated a yearly 2004 1 9 5.0 0.26 1.90 4.56 increase in the turnover rate of 0.21 ± 0.08 %/year (P < 2005 11 0 5.5 0.12 1.49 2.67 0.01, Wald χ2 test) during this period. The community turn- 2006 4 8 6.0 0.10 1.50 3.15 over, which was measured by the dissimilarity (PDI), varied 2007 5 11 8.0 0.14 1.51 4.17 from 0.001 to 0.65 (Table 3). The maximum dissimilarity was observed between 2000 and 2004, when the dissimilar- 2008 7 4 5.5 0.08 1.41 3.71 ity was approximately fivefold higher than that observed 2009 4 3 3.5 0.04 1.44 3.61 in other years during the study period. Shannon-Wiener’s 2010 4 2 3.0 0.04 1.42 3.36 index (H’) varied from 0.18 (in 1987) to 2.15 (in 2000), and 2011 1 0 0.5 0.03 1.41 3.26 Margalef’s index (MG) varied from 2.67 (in 2005) to 4.56 2012 1 2 1.5 0.04 1.52 3.50 (in 2004) (Table 3). In general, all of the main community characteristics (STO, PDI, H’, and MG) exhibited a posi- ral growth of bogs due to a positive water balance lead- tive trend over the study period, but their variability rate and ing to forest paludification. Despite the general change in dynamics were different. The variability, instability, and the surrounding area the extent, distribution and relative species compositional change of the community increased importance of the main biotopes (open water, quagmire, considerably in the 2000s after the disappearance of the reed, floating islets and mineral islets) and potential food black-headed gull colony, and these processes have been resources (vertebrate and invertebrate fauna and veg- coherent (Tables 2, 3 and 4; Figures 2 and 3; Appendix 1). etation) for birds were not substantially altered in Lake The first recorded breeding of mute swan Cygnus olor was Endla during the study period (Estonian State Environ- observed in 1991, whooper swan Cygnus cygnus in 1998, mental Monitoring Programme 2015). Agricultural land is and the species pintail Anas acuta, northern shoveler Anas of importance as a feeding area for gulls and considerable clypeata, common pochard Aythya ferina, and great crested alterations in agricultural land use took place during the grebe Podiceps cristatus disappeared as breeding bird spe- study period, the greatest changes occurring at the same cies during the study period (Appendix 1). Of the identified time as the gull colony crash (Figure 2). breeding bird species 5 belong to Category II protected spe- cies in Estonia, 12 to Category III of protected species and 13 are listed in Annex I of the EC Bird Directive.

2016, Vol. 22, No. 1 (42) ISSN 2029-9230 4139 BALTIC FORESTRY BLACK-HEADED GULL (LARUS RIDIBUNDUS L.) AS A KEYSTONE SPECIES IN THE LAKE /.../ A. LEITO ET AL.

Table 4. Mean numbers of single bird species in the years characterised by the presence of the black-headed gull colony and in the years characterised with the absence of the colony. The bird species are shown as 3+3 first letter acronyms of the full Latin name and in alphabetical order. N1 = mean numbers in the years without the colony; N2 = mean numbers in the years with the colony; W = statistic of the Mann-Whitney U test; P = significance value. Significance (P) levels: *** < 0.001, ** < 0.01, * < 0.05, and ∙ < 0.1

Species N1 N2 W P-value P-level Figure 4. Counts of mallard, pochard, tufted duck, and coot at Acraru 11.4 17.3 14 0.012 * Lake Endla in 1987–2012 Acrsch 216.8 88.4 87 0.001 *** Acrsci 5 1.1 86 0.001 *** The role of black-headed gull The total number of breeding pairs recorded between Acthyp 0 0.8 20 0.010 ** 1987 and 2012, including the black-headed gull colony, Anacly 0.1 2.4 17 0.009 ** varied between 305 and 8,301 pairs (mean ± SD = 3,276 ± Anacre 0.5 3.4 17.5 0.021 * 3,341; n = 20 years), and the year on year variation (CV) Anapen 0.6 1.9 14 0.008 ** was 102% (Appendix 1). The total number of breeding Anapla 1.9 17.1 1.5 0.000 *** pairs discounting black-headed gull varied between 175 Anaque 0.8 2.3 25 0.100 ∙ (in 1987) and 571 (in 2006) pairs (average ± SD = 392.2 ± 115.8; n = 20 years), and the CV was 29%. In the years Aytfer 4.2 33.2 9 0.003 ** when the black-headed gull colony was present and domi- Aytful 7.4 48.6 10.5 0.005 ** nated, the relative share of this species was 58–97 % of Buccla 0.5 1.3 20 0.028 * the total breeding pairs of all species. In the years when Cygolo 5.4 1.1 86 0.001 *** the black-headed gull colony was absent, sedge warbler Embsch 96.5 40.2 84 0.001 *** Acrocephalus schoenobaenus dominated. In the time peri- Fulatr 6.7 23.8 2 0.000 *** od in which the black-headed gull colony was present, the CV of the total breeding pairs was 11%, whereas, in the Galgal 1.1 2.1 24 0.083 ∙ time period in which this colony was absent, the CV was Grugru 6.6 3.9 75 0.014 * 25 %. The total number of breeding pairs was strongly re- Lancol 0.6 0 58.5 0.093 ∙ lated to the presence/absence and size of the black-headed Lararg 0.2 1.1 8 0.001 *** gull colony, which varied between 0 and 8,000 pairs (av- Larmin 0.1 3 13 0.004 ** erage ± SD = 2,884 ± 3,375; n = 20 years; Figure 3 and Appendix 1). In the period in which the colony was at its Loclus 20 6 84 0.002 ** peak (1987–1998), the total number of breeding pairs of Motalb 0 1.1 20 0.010 ** all species was 10–15 fold higher than that observed dur- Podcri 2.6 7.2 14.5 0.013 * ing the period in which this colony disappeared and was Podgri 0 1.2 15 0.003 ** absent (the 2000s). The long term population dynamics Stehir 2.4 10.1 4.5 0.001 *** of the black-headed gull colony can be divided into three different periods: a steady peak period between 1987 and 1998 (11 years), a rapid decrease (colony collapse) be- tween 1999 and 2000 (2 years), and a period characterised by very low numbers or absence between 2001 and 2012 (Figure 3 and Appendix 1). This latter period could be characterised as post-collapse fluctuation. The two changepoint trend model suggested that the presence of the gull colony has a positive significant effect (P < 0.05) on the trends of common pochard, tufted duck, great crested grebe, Eurasian marsh harrier, spotted crake Figure 3. Annual number of breeding bird species and numbers Porzana porzana, and black tern Chlidonias niger and a of the black-headed gull colony at Lake Endla in 1987–2012 significant negative effect (P < 0.05) on the trends of mute swan, water rail Rallus aquaticus, Savi’s warbler Locustel- la luscinoides, sedge warbler, reed warbler Acrocephalus

2016, Vol. 22, No. 1 (42) ISSN 2029-9230 4042 BALTIC FORESTRY BLACK-HEADED GULL (LARUS RIDIBUNDUS L.) AS A KEYSTONE SPECIES IN THE LAKE /.../ A. LEITO ET AL. CV% 86 175 109 144 120 350 121 218 131 131 100 167 91 150 50 31 0 65 98 175 150 171 95 44 69 56 175 0 257 117 62 100 95 107 0 200 167 0 71 53 81 400 38 300 175 54 102 16 SD 3 0.7 1.2 2.6 10.1 0.7 1.7 2.4 22.4 33.6 0.8 0.5 4.1 0.9 0.7 1.3 0.2 1.7 4.4 0.7 0.3 1.2 13.4 2.4 1.1 0.9 0.7 0.2 3.6 3375 1.3 0.6 5.5 19.8 0.2 1 1 0.2 9.3 83.3 2.5 0.4 5.6 0.3 0.7 38.1 3341 4.22 Mean 3.5 0.4 1.1 1.8 8.7 0.2 1.4 1.1 17.1 25.6 0.8 0.3 4.5 0.6 1.4 4.2 0 2.6 4.5 0.4 0.1 0.7 14.1 5.5 1.6 1.6 0.4 0 1.4 2884 2.1 0.6 5.8 18.5 0 0.8 0.6 0 13.1 156.2 3.1 0.1 14.1 0.1 0.4 70.6 3276 26.75 2012 6 2 1 1 2 2 6 1 2 9 2 1 1 1 2 7 160 2 11 1 85 305 21 2009 7 1 1 1 1 1 1 3 3 6 1 4 10 2 3 1 2 2 13 257 6 9 111 446 23 2008 7 1 2 1 1 3 1 1 1 3 6 5 9 1 2 4 1 1 20 286 4 8 2 124 494 24 2007 11 2 1 1 1 1 1 1 1 4 1 4 2 1 7 8 2 1 8 5 4 1 25 306 4 8 102 513 27 2006 5 1 1 1 2 1 3 1 4 1 5 9 3 35 1 26 308 8 16 2 138 571 21 2005 6 1 1 1 1 6 3 1 5 6 2 1 27 210 7 20 105 403 17 2004 5 1 3 2 6 5 1 3 1 3 2 8 1 1 7 6 3 3 2 1 2 5 2 14 185 6 18 76 372 28 2003 4 2 2 5 2 3 6 2 5 6 2 55 1 1 55 30 187 6 2 8 118 502 21 Category III protected species in Estonia (n=12) 3 2002 3 1 1 3 6 15 1 2 1 5 1 1 2 6 3 1 1 450 3 7 45 1 12 139 2 9 2 48 771 28 2001 4 3 1 6 12 1 8 1 5 3 7 3 11 4 2 1 1 2 2 1 19 153 5 8 72 335 25 2000 2 2 1 1 18 34 1 7 1 5 2 11 1 3 12 5 3 1 170 1 2 43 1 14 137 2 10 1 71 562 29 1999 2 1 15 3 35 55 2 2 2 1 5 1 10 3 15 6 2 3 1 2500 3 1 5 3 14 94 2 21 1 75 2883 30 1998 4 1 2 2 3 2 60 62 3 1 6 2 6 14 6 3 1 16 6000 1 1 8 25 1 14 111 2 12 53 6422 29 1997 1 1 1 5 5 4 55 94 3 9 3 1 6 1 10 1 20 4 3 2 5 6500 3 1 13 30 1 11 154 1 13 62 7023 32 1996 2 1 16 6 2 65 82 1 14 1 2 5 5 13 30 4 1 3 1 6000 1 1 3 40 2 2 10 135 2 27 58 6535 31 1994 2 4 20 3 50 100 2 1 5 2 2 3 2 4 60 4 3 1 2 7000 2 1 20 50 3 2 87 2 20 40 7497 30 Category II protected species in Estonia (n=5). Category II protected species 2 1991 1 5 10 30 3 3 5 10 1 1 10 2 3 3 2 25 3 2 1 1 1 8000 4 2 15 15 3 75 20 45 8301 29 1989 2 5 30 1 1 10 8 15 1 10 2 3 2 2 20 3 1 1 1 1 8000 4 1 7 13 2 40 13 14 8213 29 1988 2 4 11 2 15 10 1 7 1 3 2 8 2 10 3 2 1 2 1 6000 2 1 10 8 3 1 60 1 19 5 6197 30 1987 1 5 24 1 1 6 9 1 5 1 1 3 1 3 4 20 2 2 1 2 1 7000 1 1 10 5 1 2 40 11 10 7175 31

I, 3 3

I, 2 I, 3 3 I, 3 I, 3

I, 2 3 I, 3 I, 2 I, 3 3 I, 2 I, 2 . Bird counts in pairs and their basic statistics at Lake Endla, Estonia, between 1987 2012 I, 3 I, 3

Annex I species of the Bird Directive (n=13). Bird species Cygnus olor Cygnus cygnus Anas penelope Anas crecca Anas platyrhynchos Anas acuta Anas querquedula Anas clypeata ferina Aythya fuligula Aythya Bucephala clangula Gavia arctica Podiceps cristatus Podiceps grisegena Botaurus stellaris Circus aeruginosus Circus pygargus Rallus aquaticus Porzana porzana Porzana parva Crex crex Gallinula chloropus Fulica atra Grus grus Gallinago gallinago glareola Tringa Actitis hypoleuca vanellus Vanellus Larus minutus Larus ridibundus Larus canus Larus argentatus Sterna hirundo Chlidonias niger Clidonias leucopterus Motacilla flava Motacilla alba Saxicola rubetra Luscinia luscinoides Acrocephalus schoenobaenus Acrocephalus scirpaceus Acrocephalus palustris Acrocephalus arundinaceus Panurus biarmicus Lanius collurio Emberiza schoeniclus Pairs total Number of species Appendix 1 I

2016, Vol. 22, No. 1 (42) ISSN 2029-9230 4341 BALTIC FORESTRY BLACK-HEADED GULL (LARUS RIDIBUNDUS L.) AS A KEYSTONE SPECIES IN THE LAKE /.../ A. LEITO ET AL. scirpaceus, and reed bunting Emberiza scoeniclus (Table gull colony. Thus, it is possible that the temporal “peak” 2). The comparison of the mean numbers of breeding pairs period with extremely high total abundance and species through the Mann-Whitney U test suggested that the pres- richness that was detected during the first ten years of the ence of the gull colony had a significant P( < 0.05) posi- study period (1987–1999) was an “abnormal” fluctuation tive effect on the abundance of northern shoveler, wigeon in the bird community and that a less rich and less diverse Anas penelope, mallard, common pochard, tufted duck, community is the more “normal” community because the great crested grebe, red-necked grebe Podiceps grisegena, occurrence of a large black-headed gull colony on this coot Fulica atra, little gull Larus minutus, herring gull type of lake in a large wild mire system is atypical. The Larus argentatus, and common tern Sterna hirundo, and existence of bird communities with limited species rich- the absence of the gull colony had a significant positive ef- ness has been confirmed by bird surveys in other similar fect to the abundance of mute swan, Savi’s warbler, sedge lakes in Estonia, which usually found 10–15 bird species warbler, reed warbler, and reed bunting (Table 4). After with approximately 100-500 total breeding pairs annually the crash of the black-headed gull colony, northern shov- on this type of lake in the absence of the black-headed eler, common pochard, great crested grebe and red-necked gull (Onno 1958, Estonian State Environmental Monitor- grebe disappeared (Appendix 1). The long-term dynam- ing Programme 2015). ics of pochard and tufted duck, which are species that are The black-headed gull had the strongest positive ef- highly associated with the black-headed gull colony, were fect on waterfowl species, particularly pochard and tufted very similar (Figure 4 and Appendix 1). The abundance duck. The main benefit for waterfowl and other species of these species can be classified into four different pe- breeding inside or close to the gull colony was likely pre- riods: a steady growth period between 1987 and 1994 (7 dation protection (Hildén 1964, Väänänen 2000, Quinn years), a peak period between 1994 and 1999 (5 years), a and Ueta 2008, Väänänen 2011, Skorka et al. 2014). At strong decrease (population crash) between 1999 and 2001 Lake Endla, the main raptors are Eurasian marsh harrier, (3 years), and steady a decrease up to their disappearance white-tailed eagle, and hooded crow, and the protection or very low numbers between 2001 and 2012 (11 years). benefit of the gull colony for waterfowl against these rap- tors was likely considerable. It is notable that pochard and Discussion and conclusions tufted duck reached their peak abundance approximately five years after the peak of the black-headed gull colony, According to our results, system-wide changes took but their rapid and strong decrease coincided with the place in the bird community at Lake Endla during the crash of the black-headed gull colony (Figure 3 and 4 and study period. There was a large variation and an overall Appendix 1). This finding indicates a steady step-by-step decreasing trend in the number of species and the total immigration and adaptation to the gull colony at the be- abundance of birds. As expected, species richness and di- ginning of the study period and a fast and coherent disap- versity decreased during the study period, and the varia- pearance after the colony crash due to markedly increased tion in the species richness, diversity, and dissimilarity nest predation by harriers and ravens and additional pre- exhibited the greatest fluctuations during the 5 to 7 years dation pressure by eagles and harriers on adult waterfowl, following the collapse of the black-headed gull colony the numbers of which had already markedly decreased. (Figure 3, Table 3 and Appendix 1). The importance of Eurasian marsh harrier was found to have an evident posi- the black-headed gull colony on the bird community was tive relationship with the abundance of the black-headed evident: it had a strong positive effect during the peak pe- gull, presumably through the trophic link, as gulls, in ad- riod of the colony. After black-headed gull die out from dition to waterfowl, amphibians, and small mammals, are the study wetland populations of many duck species an important food for harriers (von Blotzheim et al. 1971, decreased sharply. According to Ebenman and Jonsson Tornberg and Haapala 2013). It is interesting that marsh (2005), the loss of keystone species can cause the loss harrier reached their peak numbers of 5-6 pairs approxi- of one or more additional species or trigger a cascade of mately five years after the peak of the black-headed gull secondary extinctions with potentially dramatic effects on colony, stayed at this maximum level for approximately the function and stability of the community. In our case, ten years, and then steadily declined to an absolute min- the loss of the black-headed gull colony did cause the dis- imum of 2 pairs over ten years. The comparison of the appearance of four waterfowl species, and the stability of long-term dynamics of these two species revealed certain the community was strongly affected. All of the basic pa- parallel but shifted trends among the species: the abun- rameters of the community, such as the species richness, dance of the marsh harrier follows the abundance of the diversity, and dominance, were changed. black-headed gull with a delay of approximately ten years Based on these indicators, we conclude that the ini- (Figure 3 and Appendix 1). In addition, this association tially rich bird community at Lake Endla broke down and is different from that found with common pochard and was restructured after the collapse of the black-headed tufted duck, which exhibited a similar population growth

2016, Vol. 22, No. 1 (42) ISSN 2029-9230 4244 BALTIC FORESTRY BLACK-HEADED GULL (LARUS RIDIBUNDUS L.) AS A KEYSTONE SPECIES IN THE LAKE /.../ A. LEITO ET AL. period but a different rapid decline period that coincided la as there have never been American mink or other fur directly with the crash of the black-headed gull colony farms in this area. and the following disappearance process. Potentially, the Potentially, one cause of collapse of the colony at food source particularly of fish may play leading role Lake Endla and the decrease in numbers of black-headed in duck populations in lakes (Vīksne et al. 2010, 2011, gull throughout Estonia (Elts et al. 2013) could be a de- Nummi et al. 2012) but in Lake Endla there has not found crease in feeding habitat and food resources. One of the any considerable changes in fish species composition and main feeding habitats for black-headed gull during the abundance of different species and in total during the last breeding season are arable lands and meadows where they decades (Mäemets 1968, 1977, Ott 2011). feed on invertebrates (predominantly earthworms, spiders A case study at Lake Engure in Latvia revealed similar and insects) and young shoots of different crops particular- findings regarding the relationship between black-headed ly of cabbage and turnip (von Blotzheim and Bauer 1982, gull colonies and waterfowl species to those found in our Ilichev and Zubakin 1988). The area of agricultural land study (Vīksne et al. 2005, 2011). According to Väänänen in Estonia decreased by almost fifty percent (Figure 2) (2000, 2011), the breeding of tufted duck and common po- and the crop type changed unfavourably for gulls between chard in eutrophic inland lakes in Finland is strongly relat- 1992 and 2012: the planting of summer and winter rape ed to colonial larids, particularly black-headed gull, and the has increased dramatically (FAOSTAT 2014). Generally, main benefit that has been found is the protection against agricultural intensification is harmful for farmland birds predators. As in our study, other waterfowl, ducks, and (Donald et al. 2006, Herzon et al. 2008). As elsewhere in coots exhibited a weaker association with larid colonies. In Europe, agricultural intensification has taken place in Es- addition, quite similar general results have been obtained in tonia (wheat yields per hectare have doubled and rapeseed other studies on different bird communities in Europe and tripled between 1992 and 2012) (FAOSTAT 2014), poten- America (Quinn and Ueta 2008, Vīksne et al. 2010). tially another negative impact for black-headed gull. We It has been recognised that anthropogenic stress in- don’t have enough data to prove the connection between creases the short-term variability of ecological communi- gull abundance and changes in agriculture, this is a ques- ties (Angeler and Moreno 2007, Hillebrand et al. 2010). tion for a future study. However, there has been limited human activity in Lake This study provides an important insight into the im- Endla, therefore there must be other factors that caused pacts of gull colony collapse on a lake bird community the rapid shifts in the bird community. The most consid- based on long-term observations, although further study erable shifts in the community were associated with the is required including a greater number of lakes to identify abundance of the black-headed gull. Concurrently, other if this is indicative of a wide ranging or local association. unrelated community changes took place. Both mute and The reasons behind the gull colony crash are unknown, whooper swan colonised the lake for the first time during although it is possible that an unknown factor could also our study period, and their population growth was likely have been the cause for the changes in abundance of other mainly caused by the expansion and population increase bird species. However, other studies have shown shifts in of species over a larger surrounding area connected with bird communities following loss of the gull colony (e.g. climate-dependent changes in the distribution range (von Vīksne et al. 2011, Estonian State Environmental Moni- Haartman 1973, Renno 1993, Väisänen et al. 1998, Sau- toring Programme 2015). rola et al. 2013). The same reasoning could be applied to In conclusion, our results show that the black-headed the population growth of the Eurasian crane and Savi’s gull is a keystone species and that the bird community at warbler at Lake Endla (Elts et al. 2009, 2013). Lake Endla has reacted to the loss of this species in a man- The reasons for the crash of the black-headed gull ner similar to that observed in a typical fragile system. colony at Lake Endla are unknown. No external signs, In this case, the loss of a keystone species did not result including viral infection or toxic poisoning causing high in community collapse, but the post-extinction commu- mortality, increased nest predation, or habitat loss, were nity is characterised by a significantly lower diversity and observed. Although this type of obscure disappearance of abundance of breeding birds. The main beneficial effect black-headed gull colonies is not rare and has been doc- of the gull colony on waterbirds is likely to be the protec- umented several times in different areas, and for which tion against predators, and the main reason for the strong there is still no explanation (Kumari 1978, von Blotzheim decline and secondary extinction of several waterfowl and Bauer 1982, Ilitchev and Zubakin 1988, Vīksne et al. species is likely closely related to the loss of the black- 2011). According to Vīksne et al. (2011), the reduction in headed gull. We conclude that a large black-headed gull the population size of the black-headed gull and water- colony significantly enriches the bird community and the fowls at Lake Engure was associated with the increase in whole ecosystem, even though such a colony-dependent American mink population size in the surrounding farms. assembly is potentially fragile and may be short-lived. However, this can be discounted as a factor at Lake End-

2016, Vol. 22, No. 1 (42) ISSN 2029-9230 4543 BALTIC FORESTRY BLACK-HEADED GULL (LARUS RIDIBUNDUS L.) AS A KEYSTONE SPECIES IN THE LAKE /.../ A. LEITO ET AL.

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2016, Vol. 22, No. 1 (42) ISSN 2029-9230 4745 BALTIC FORESTRY THE EFFECT OF BEAVER ACTIVITY ON ARTIFICIAL IMPOUNDMENT /.../ M. WRÓBEL ET AL. The Effect of Beaver Activity on Artificial Impoundment on the Braszcza River in the Białowieża Primeval Forest

MICHAŁ WRÓBEL1*, ANDRZEJ BOCZOŃ1, RADOSŁAW GAWRYŚ1, ANNA KOWALSKA1 AND ANNA KRYSZTOFIAK-KANIEWSKA2 1Forest Research Institute, Department of Forest Ecology, ul. Braci leśnej 3, Sękocin Stary, 05-090 Raszyn, Poland 2University of Life Sciences in Poznań, Department of Forest Engineering, ul. Mazowiecka 41, 60-623 Poznań. Poland *Corresponding author, e-mail: [email protected]

Wróbel, M*., Boczoń, A., Gawryś, R., Kowalska, A. and Krysztofiak-Kaniewska, A. 2016. The Effect of Beaver Activity on Artificial Impoundment on the Braszcza River in the Białowieża Primeval Forest. Baltic Forestry 22(1): 46-50.

Abstract

In Poland in recent years, the number of engineered and technical structures in forest areas has increased, and these have in turn affected water conditions. The purposes of these structures include protecting habitats, enabling rehabilitation of wetland areas, and protection of biodiversity. In addition to the State Forests National Forests Holding, numerous other organisations and associations have taken part in work to improve water conditions. One of these organisations is the Polish Society for the Protection of Birds, which, at the beginning of the 21st century, worked to improve the habitat conditions of birds. This effort was made by constructing dams on watercourses in the Białowieża Forest. As part of this work, several structures were built on the Braszcza River. One of these dams has been monitored since 2004 to assess the impact of the structure on water level. This dam has become an ideal location for habitation of the beaver, which was first noticed in the spring of 2006. Beaver activity has increased the height of the dam by approximately 50 cm. In this study, we analyzed changes in water level prior to the arrival of beavers, during their stay, and after they left their lodges.

Keywords: beaver, water level, the Białowieża Primaval Forest

Introduction The dams, or weirs, built by the PTOP created a per- fect location for beaver settlement. Built upon the exist- At the turn of the 21st century, water deficits were ing manmade dams, beaver dams resulted in flooding of observed in Polish forests, including water shortages in surrounding areas. This has resulted in a dilemma as to forest soil and decreases in water surface level. This re- what measures, if any, should be taken in such areas to sulted in a decrease in the humidity of forest habitats. The protect animal species, habitat, or vegetation. The aim of underlying causes of this were both man-made and cli- the study is to identify and assess the impact of beaver matic ones, caused by warm winters that had an adverse dam on shifts in hydrology within the vicinity of these impact on water resources. These changes also affected dams during the entire lifespan of the dams. the Białowieża Forest, which resulted in lower water re- sources (Czerepko et al. 2007). The best conserved low- Materials and methods land forests of Europe have suffered due to water short- ages, in particular wet deciduous and mixed forests that Study area cover approximately 14.5 % of the Białowieża Forest. The weir that was studied is located in the northern To improve water availability, attempts to change part of the Białowieża Forest, approximately 4 km east of this situation were undertaken. The North Podlasie So- Narewka village, in the 82nd compartment of the Browsk ciety for the Protection of Birds (since 2006 the Polish Forest District. The weir is situated on the Braszcza River, Society for the Protection of Birds, PTOP) began coop- which is the right bank tributary of the Narewka River. erating with the Regional Directorate of State Forests in The length of this tributary is approximately 9 km, and the Białystok to develop small scale water retention systems. catchment area is 40.3 km2. The shape of the catchment In 2001, on initiative of the North Podlasie Society for the area is irregular; the upper part of the catchment area is Protection of Birds, the construction of small scale water wide, with a maximum width of 7 km, and in the lower retention elements was started within the Białowieża For- region the river narrows to a width of 1.3 km. Braszcza, as est area. By 2005 a total of 33 structures had been built in with the majority of the forest’s rivers, originates from wet- the Łutownia River basin. lands located northward of Masiewo village and does not

2016, Vol. 22, No. 1 (42) ISSN 2029-9230 4648 BALTIC FORESTRY THE EFFECT OF BEAVER ACTIVITY ON ARTIFICIAL IMPOUNDMENT /.../ M. WRÓBEL ET AL. have a typical source. Since the middle of the 20th century, To determine the changes in water surface level de- beavers have extensively dammed the Braszcza River. The pending on the presence of beavers, the measurement pe- forest cover in the catchment area is 74.7 %. The wood- riod was divided into three phases. The first phase, in the lands, forming part of the catchment area, are characterized absence of beavers, was from 1/04/2004 to 31/07/2006. by high heterogeneity, and it is difficult to discern which The second phase covered the period of beaver settlement group of habitats is important within the catchment area. in the structure, between 1/08/2006 and 30/06/2008. The Fresh forest sites constitute 36.1 % of the area, whereas third phase was the period of time when no beaver activity moist and marshy sites comprise 38.6 % of the area. was observed, between 1/07/2008 and 30/06/2013. The dates for the third phase were determined based on field Methods observations, including the condition of the beaver lodge (no new elements and current repairs), signs of feeding We studied a stone weir, on which, in 2006, beavers (no new felled trees and shrubs) and changes in the eleva- added their lodge. As a result, they increased the origi- tion of the ground water table (Figure 3). nal damming height by approximately 45 cm, which has resulted in the formation of a reservoir. Two monitoring Results wells were placed in 2004 on the test surface. One was situ- ated in the river (well 1), and the other at a distance of 40 In the first period between 1/04/2004 and 31/07/2006, m from the first well (well 2). The wells were fitted with that is, in the absence of beaver activity, the level of the equipment to record water surface level at 6-hour intervals, water table showed greater variability in the well located and a mean daily value was determined based on these 40 m from the watercourse. There were greater water lev- measurements. Figure 1 illustrates the design of the weir el rises as well as drops in the periods without precipita- that was investigated in this study. Beavers built a dam at tion. Therefore, the presence of the weir caused discern- the highest point of the weir. Placements of the wells and ible changes in the water level. The greatest difference the weir, including topography, are shown in Figure 2. between the maximum and minimum values in the eleva-

Figure 1. The design of the weir

Figure 2. The topography of the studied sur- face in the 82nd forest compartment of the Browsk Forest District (reference level 153.8 m a.s.l.) with landmarks

2016, Vol. 22, No. 1 (42) ISSN 2029-9230 4947 BALTIC FORESTRY THE EFFECT OF BEAVER ACTIVITY ON ARTIFICIAL IMPOUNDMENT /.../ M. WRÓBEL ET AL. tion of water surface level in the watercourse was 63 cm, 4. Prior to the beaver dam being built, this was 151.85 while at a distance of 40 m from the watercourse it was m a.s.l. The minimum and maximum levels were 151.44 77 cm. In the second phase, from September 2006 until m and 152.07 m a.s.l., respectively. In the second phase, the middle of 2008, the level of the water table in wells when the beavers were present, the mean water level in- 1 and 2 was affected by the beaver dam. The impact of creased by 60 cm to reach a mean height of 152.45 m the beaver dam resulted in a “smoothing” of changes in a.s.l. The difference between the minimum and maximum the water table, resulting in limited fluctuations compared values during that period was 55 cm. However, in 2007, to the situation prior to beaver settlement. In the second when the beaver dam was fully developed, the difference phase between 1/08/2006 and 30/06/2008, the largest dif- between the maximum and the minimum levels was only ference between the maximum and the minimum values 22 cm, and the mean water level was 152.48 m a.s.l. This of water table level in well 1 was 55 cm whereas at well shows a significant reduction in fluctuations of the wa- 2 it was 59 cm. Taking into consideration the fact that ter level associated with the presence of the beaver dam. these periods were designated in a rather subjective man- When the beavers left the structure, the water level did ner, the differences may be less pronounced. This was the not return to its previous state. The existing, damaged case in 2007, midway through the second measurement dam still exerted an influence on the mean level of water, period, when the beaver dam was fully operational; dur- which was found to be 152.18 m a.s.l., or 33 cm higher ing this period the differences amounted to 22 cm for the than the mean value at phase 1. watercourse, and 31 cm at a distance of 40 m from the At a distance of 40 m from the watercourse, the mean watercourse (Figure 3). During the third period between water table levels were higher than those recorded in the 1/07/2008 and 30/06/2013, when the beavers left the area, watercourse. Additionally, at well 2, the differences be- water fluctuations appeared to be similar to that observed tween the maximum and the minimum surface water eleva- prior to the beavers’ arrival. However, comparison of tion were greater. The mean levels of the water table during measurements at phase 1 and phase 3 revealed that the 3 periods are presented in Figure 5. In the period when the water level was slightly higher after the beavers left the beavers were absent, the mean height was 152.09 m a.s.l., dam. This was most likely due to the remaining elements with a 77 cm difference between the extreme values. Dur- of the beaver dam remaining in an unrepaired state, which ing the period of beaver activity, the water level increased produced the relative increase in water surface area. After by a mean height of approximately 50 cm to reach 152.58 the beavers left the structures, the differences between the m a.s.l. The minimum and maximum levels were 152.16 highest and lowest water surface elevations were 63 cm m and 152.76 m a.s.l., respectively. As had been done with for the watercourse and 66 cm at a distance of 40 m from watercourse measurements, taking into consideration the the watercourse. fully developed dam in 2007, the difference between the The mean water table levels in the watercourse for minimum and maximum levels was only 31 cm. In the pe- well 1 during the designated periods are shown in Figure riod after the dam had been abandoned by the beavers, the

Figure 3. Time course showing the changes in the level of water table in the 82nd forest compartment of the Browsk Forest District

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Figure 4. Mean water levels in well 1 for the individual periods Figure 5. Mean water levels in well 2 for the individual periods mean water level fell to 152.32 m a.s.l., which was still 23 in the Appalachian Mountains, more than 20% of dams cm higher than the original value at phase 1. last for more than 11 years (Fryxell 2001). Researchers As a result of beavers settling in the structure a res- have conducted observations on beaver dams as old as ervoir was formed, which covered an area of over 4.5 ha. 56-year-old ones (Bonner et al. 2009). The watercourses This caused certain trees to die and the entire flooded area transformed by beavers have increased water retention ca- was left for the natural succession. pabilities. In addition, larger water surface area increases transpiration; however, it is substantially lower than the Discussion and conclusion volume of retained water (Woo and Waddington 1990). Beavers are, therefore, the source of site disturbances that The subject of this study is of local importance, and can last for up to 50 years (Wright et al. 2002, Terwilliger it fits with the general view that beavers usually settle into and Pastor 1999); however, the mean duration of the cycle watercourses that are shallow and not very wide (Czech of site changes (e.g. the process of habitat changes from 2000). In this case, beavers built a dam on the artificial scrubland to flooding to meadows and back to scrubland) damming structure, which facilitated the construction lasts between 10 and 30 years (Remillard et al. 1987). process. Commonly applied construction materials were Widening of the riparian zone (McKinstry et al. 2001) and used, such as tree trunks, branches, mud, soil, and turf. rising of groundwater level (Gałek and Woch 2011) are (Czech 2000). also observed. At our site, the rise in groundwater level The height of a beaver’s dam seldom exceeds 1.5 m reached an average of 50 cm at a distance of 40 m from (Gurnell 1998). Measurements performed in the Bory the watercourses in the stand. Tree growth decreased, and Tucholskie region indicate that the mean height of a dam is within two years of the pond formation nearly 80 % of approximately 0.8 m with a span of 0.3-2 m (Rurek 2013); trees died (Boczoń et al. 2009). Artificial damming was not similar results were obtained on a stream in the Ojców found to impact birds. However, after settlement of the site National Park (Medwecka-Kornas and Hawro 1993). The by beavers, flooding increased surface area several times studied beaver dam in the Białowieża Forest also fits into inundating the terrain that was intended for birds. During these dimensions, as its height is approximately 0.5 m. the settlement of the site by beavers, the water level sta- Typically, a reservoir of 0.5 to several dozen of hectares bilized and the amplitude of fluctuations declined signifi- is created as a result of a beaver dam construction (Czech cantly. However, this occurred at levels causing significant 2000); generally larger and shallower ponds are located in damage to vegetation. Beaver protection status in Poland the lowlands and smaller and deeper ones in the uplands forbids both the destruction of their dams and the hunting and in the mountains (Johnston and Naiman 1987). The on them. Modification of their dams can possibly mitigate studied site conforms to these generalizations, as the stud- damage caused by beavers. Pipes placed in beaver dams ied location exceeded an area of 4.5 ha. The dam in this can equalize the water level regardless of the height of the study was constructed in the middle of 2006, and after it dam (Taylor and Singleton 2014), however this technology was abandoned by beavers it continued to impact water is not very popular in Poland yet. This option is one of the levels. Researchers have estimated the mean time of oper- simpler and cheaper solutions. ation for a single dam to be approximately 10 years (Knud- In Poland, beavers are under strict protection, and sen 1962, Remillard et al. 1987, Fryxell 2001). However, as their population continues to grow additional conflicts

2016, Vol. 22, No. 1 (42) ISSN 2029-9230 5149 BALTIC FORESTRY THE EFFECT OF BEAVER ACTIVITY ON ARTIFICIAL IMPOUNDMENT /.../ M. WRÓBEL ET AL. will probably arise between beavers and human interests W. (Eds.), Wetlands: Monitoring, Modelling and Manage- in the coming years. In 1976, the estimated number of ment. Taylor & Francis Group, London, p. 37-43. Fryxell, J.M. 2001. Habitat suitability and source-sink dynamics of beavers was 500, but by 2012 this number had reached beavers. Journal of Animal Ecology 70: 310-316. 89,000 (Witkowski 2013). Undoubtedly, beavers serve an Gałek, D. and Woch, F. 2011. Analiza zmian populacji bobra eu- important role in increasing biodiversity through the erec- ropejskiego (Castor fiber) na terenie Świętokrzyskiego Parku tion of dams and the formation of impoundments. Beaver Narodowego [Analysis of changes in populations of European beaver (Castor fiber) in the Świętokrzyski National Park]. impoundments significantly contribute to the abundance Roczniki Świętokrzyskie, Ser. B - Nauki Przyrodnicze 32: 9-26 and diversity of mammal species. Animals from small (in Polish). pigmy shrews to larger species, such as roe deer, are able Gurnell, A.M. 1998. The hydrogeomorphological effects of beaver to benefit from beaver activities in ways that suit their dam-building activity. Progress in Physical Geography, 22(2): 167-189. own survival needs (Janiszewski et. al 2014). Beavers Janiszewski, P., Hanzal, V. and Misiukiewicz, W. 2014. The Eur- play an important role in water retention and maintenance asian Beaver (Castor fiber) as a keystone species – a literature of soil moisture content; nevertheless, in forest areas they review. Baltic Forestry 2(39): 277-286. may cause local extinction of tree stands in river valleys, Johnston, C.A. and Naiman, R.J. 1987. Boundary dynamics at the aquatic-terrestrial interface: the influence of beaver and geo- which may result in the formation of deforested valleys morphology. Landscape Ecology 1: 47–57. and the halting of typical forest riverside communities. Knudsen, G.J. 1962. Relationship of beaver to forests, trout and The results of the study indicate that beaver dams can wildlife in Wisconsin. Wisconsin Conservation Department significantly influence hydrological conditions in the wa- Technical Bulletin No. 25. McKinstry, M.C., Caffre,Y.P. and Anderson, S.H. 2001. The im- tercourse and its surroundings. The water surface level in portance of beaver to wetland habitats and waterfowl in Wyo- the watercourse at the studied site increased by more than ming. Journal of the American Water Resources Association 60 cm, whereas at a distance of 40 m from the watercourse 37 (6): 1571-1577. the water table increased by 50 cm. A reservoir covering Medwecka-Kornas, A., and Hawro, R. 1993. Vegetation on beaver dams in the Ojców National Park (southern Poland). Phyto- an area of over 4.5 ha was formed, which interrupted the coenologia 23: 611-618. growth stages of local flora and caused tree stand to die. Remillard, M.M., Oruendling, O.K. and Bogucki, D.J. 1987. One recommendation for the builders of artificial weirs is Disturbance by beaver and increased landscape heterogeneity. to carry out a more detailed analysis on the extent of the Landscape heterogeneity and disturbance. Ecological Studies 64: 103-122. potential reservoir. This should be conducted with regard Rurek, M. 2013. Lokalne zmiany środowiska przyrodniczego to the likely increase in water level caused by beavers, wywołane działalnością Bobra Europejskiego (Castor fiber and careful planning should be employed to try to mini- L.) w okolicy Trzebcin (powiat tucholski) [Local changes in mize the possible adverse effects of flooding. the nature environments caused by activity of the European beaver (Castor fiber L.) on the outskirts of Trzebcin (Tuchola administrative district)]. Journal of Health Sciences 3(15): References 232-246 (in Polish). Terwilliger, J. and Pastor, J. 1999. Small mammals, ectomycor- Boczoń, A., Wróbel, M. and Siniaiev, V. 2009. The impact of bea- rhizae, and conifer succession in beaver meadows. Oikos 85: ver ponds on tree stand in a river valley. Journal of Water and 83–94. Land Development 13a: 313–327. Witkowski, J. 2013. 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In: Received 08 July 2015 Okruszko T., Maltby E., Szatyłowicz J., Świątek D., Kotowski Accepted 25 January 2016

2016, Vol. 22, No. 1 (42) ISSN 2029-9230 5052 BALTIC FORESTRY VALIDATION OF MEDIUM-SCALE HISTORICAL MAPS OF SOUTHERN LATVIA /.../ A. FESCENKO ET AL. Validation of Medium-Scale Historical Maps of Southern Latvia for Evaluation of Impact of Continuous Forest Cover on the Present-Day Mean Stand Area and Tree Species Richness

ANDA FESCENKO1,2,3 *, MARTINS LUKINS1,2 AND ILJA FESCENKO1 1University of Latvia, 19 Rainis Boulevard, Riga LV-1586, Latvia 2Latvian State Forest Research Institute “Silava”, 111 Rigas str., Salaspils LV-2169, Latvia 3Swiss Federal Research Institute WSL, Zurcherstrasse 111, CH-8903 Birmensdorf, Switzerland *Corresponding author, e-mail: [email protected]

Fescenko, A. *, Lukins, M. and Fescenko, I. 2016. Validation of Medium-Scale Historical Maps of Southern Latvia for Evaluation of Impact of Continuous Forest Cover on the Present-Day Mean Stand Area and Tree Species Richness. Baltic Forestry 22(1): 51-62.

Abstract

Medium-scale historical maps are often the only cartographic source of former forest area distribution on a regional level. In conjunction with a database of the current distribution of species or functional traits, maps may be valuable tool for studying the impact of previous land use on ecosystems. In this study a heterogeneous set of historical maps was used to reconstruct the multi-temporal pattern of the forest area in a moderately forested region (5,180 km2) of southern Latvia during the last 220 years. Changes in the total forest cover were assessed in four time slices and compared with available historical statistical data. To validate the obtained multi- temporal data for ecological studies, the impact of continuous forest cover on the present-day mean stand area and tree species richness derived from the forest inventory database of 94,886 stands was quantified by bivariate and regression analyses. We found no significant impact of inaccuracy of the historical maps on the entire forest continuity pattern of the study area. In particular, the diversity metrics dependencies on the forest continuity can be described by quadratic regression models with coefficients of determination close to one. We also found that the mean stand area is for about 18% larger in woodlands with longer forest continuity irrespective of the forest type. The older woodland the less difference was found between boreal deciduous and nemoral deciduous forests in terms of tree species richness.

Keywords: forest continuity, historical maps, mean stand area, nemoral deciduous forests, tree species richness, Zemgale

Introduction Orczewska 2009a), and mitigate climate change through increasing carbon sequestration and storage (Koerner et An understanding of land-use history is critical in al. 1997, Bossuyt et al. 1999, Orczewska 2009a). There- evaluating of nature conservation strategies, for foster- fore, the identification of ancient forests and prevention ing methods to sustainably use natural resources, and for of their deforestation are two of the most urgent needs of interpreting modern landscapes (Foster et al. 1998, Eriks- forest management. son et al. 2010, Szabo and Hedl 2011). In forest ecology, The main methods used to reconstruct past land-use the main goal of historical land-use studies is to identify patterns are analyses of pollen, soil and field evidence, in- ancient woodland, i.e. areas that had continuous forest ventories of indicator species, studies of written archival cover for a certain period (Peterken 1996). The thresh- sources, as well as analyses of historical maps and aerial old date for a forest to be regarded as ancient is the date photographs (Egan and Howell 2001). Historical maps are of the oldest map that clearly depicts the forest pattern the most comprehensive source of spatial distribution of (Hermy and Verheyen 2007). Ancient woodlands are es- former land cover and land use. Relatively accurate maps sential for environmental sustainability as they provide on different scales have been available since the 18th cen- habitats for certain species of plants and animals (Wulf tury for almost the whole of Europe (Orczewska 2009b, 1997, Hermy and Verheyen 2007, Sikorska et al. 2008, Skaloš et al. 2011). Handling and analysing such maps

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FESCENKO ET AL. using Geographic Information Systems (GIS) is relatively continuity, or by performing analysis on a regional level. easy, efficient and less time-consuming than performing Numerous regional studies have already been carried out field studies (Wulf et al. 2010) and could thus be widely to evaluate and describe the forest cover from medium- applied in various kinds of forest management planning. scale historical maps (e.g. Orczewska 2009b, Skaloš et For example, mapping forests with different duration of al. 2011, Mikusinska et al. 2013, De Keersmaeker et al. continuous forest cover could be useful for setting priori- 2015), while no study, to our knowledge, has evaluated ties for afforestation plans because the proximity of an- the impact of forest continuity on present-day ecosystem cient woodlands might serve as sources for forest species parameters on a regional level. Moreover, applicability of to colonize recently created forests (Orczewska 2009a). historical maps in previous studies is usually assumed as However, heterogeneity of historical maps of differ- a postulate, and no quantitative description was applied to ent origins and scales may present some problems: 1) the prove this approach. accuracy of cartographic sources varies greatly (Stäuble In this paper we address the problem of validity of et al. 2008) since mapmaking has constantly developed heterogeneous historical data in ecological studies by us- during the studied period. Use of GIS can improve the ap- ing a set of historical maps to reconstruct the develop- plicability of old maps for regional level research (Kramer ment of the forest area over the last 220 years in Zemgale, et al. 2011). Vectorized historical maps can, however, give a region of Latvia with the same economic and political the false impression that the spatial patterns on the maps history. Firstly, the forest area at four different time points are very accurate, thus they should not be used without since the end of the 18th century was calculated and com- understanding the limitations of the original cartographic pared with available historical statistical data for the study sources; 2) the dating of some of the features depicted on region. Secondly, woodlands with different forest continu- a map may not be related to the date of its issue; a field ity were localized to find out the impact of continuous for- survey of regional forest patterns may take several years, est cover on two present-day diversity metrics: the mean and could be complemented by data from older maps, es- stand area (i.e. the inverse of stands density) and tree spe- tate surveys and questionings (Kavacs 1994) ; 3) defini- cies richness. If the maps are not valid representations of tions of forest tend to differ according to time period and the historical forest cover, noisy and hardly interpretable type of maps. The last problem especially affects maps dependencies will be obtained, since any systematic bias that were made for economic purposes, e.g. land cadas- is unlikely for the whole set of different historical maps. tral maps, as they tend to have been based more on exist- We hypothesized that 1) the total forest cover obtained ing land-use principles (Raet et al. 2008). The definition from medium-scale historical maps does not contradict to of ‘forest’ used by military cartographers might be more available historical statistical data; 2) any unknown fac- unambiguous as objects on military maps have strategic tors related to imperfection of the historical maps do not importance. Land, where tree vegetation dominates, is significantly distort dependencies of the diversity metrics treated as a forest in military cartography, because any on the forest continuity. type of forest cover may influence the movement of mili- tary units. Materials and methods Despite the difficulties, in practice, maps are often the only historical source of information about the spa- Study area tial distribution of natural objects in the past and are al- The Zemgale region (lat. 56°N, long. 23°E) located ready successfully used for former land-cover and land- in an agricultural region in the south of central Latvia use studies (Kienast 1993, Reithrnaier 2005, Grossinger (Figure 1) is about 5,178 km2 in size. Forest covers about and Striplen 2007, Gimmi et al. 2011). The overwhelming 31% of the landscape (State Forest Service 2010). The majority of studies dedicated to clarifying the impact of study area includes Bauska, Jelgava and Dobele admin- forest history on current ecological parameters such as the istrative districts. Most of Zemgale is a plain 20 to 60 m understory vegetation or the carbon stock, have been per- a.s.l., except the western part, where the elevation is 60 to formed on one single site (Molinari et al. 2005, Barbier 150 m a.s.l. The study area is located in the transition zone et al. 2008, Wäldchen et al. 2013). An advantage of such between boreal and nemoral forests, the so-called hemi- stand-level studies is that it is easier to find the contours boreal vegetation zone (Ahti et al. 1968). Areas of sandy of old and recent forests using evidence from histori- soil in the north and north-east of Zemgale are covered cal materials or field observations. However, the results with Pinus sylvestris L. dominated boreal forest tracts of such studies depend on site characteristics, which is (Figure 1). Picea abies L. H. Karst. stands are more com- why contradictory results are reported for different places mon on mesotrophic soils in the western part of Zemgale. (Wulf 2003, Verheyen et al. 2003, Barbier et al. 2008). Stands with thermophilous, nemoral deciduous tree spe- The effect of site can be minimised by accumulating re- cies Quercus robur L., Fraxinus excelsior L., Tilia cor- sults from studies of different stands with similar forest data Mill., Ulmus glabra Huds. are scattered in the central

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Figure 1. The spatial distribution and the proportion of the forests by forest types in the study area in 2010. The location of the study area in Latvia is shown in the upper-left panel and southern areas on eutrophic soils. Early successional, into the Soviet Union, and remained under that rule until boreal deciduous tree species Betula pendula Roth, Popu- the Republic of Latvia was re-established in 1991. With lus tremula L., Alnus incana L. Moench. and Alnus glu- the re-independence of Latvia in 1991, land claims of tinosa L. Gaertn. are common over the whole study area. former owners led to more agricultural lands being aban- Before agriculture became widespread (until ca. 500 doned, resulting in rapid afforestation (Penēze et al. 2009, AD), lowlands of Zemgale were covered by nemoral tree Lūkins and Nikodemus 2011). species, especially Quercus robur (Galeniece 1959). His- toric records indicate that when the German crusaders ar- Historical maps rived in the 13th century, Zemgale (Semigallia) was still In this study we used medium-scale (1:75,000 - mainly covered with forests (Zunde 1999). From 1290 to 1:300,000) historical maps from three cartographic sourc- 1562 the territory of Zemgale was a part of the ecclesi- es (Table 1) to reconstruct the historical forest distribu- astical state Terra Mariana (also known as Livonia) as tion in Zemgale every 50-100 years from 1790 onwards. a principality of the Holy Roman Empire. After the Li- The maps are digitalized copies from the authors’ private vonian War, it became a part of the Duchy of Courland collections, and cover the whole study area. The exact or and Semigallia with its capital in Jelgava (Mitau). It is estimated final year of the cartographic survey was used known that in the Duchy forest resources were intensive- to date the forest distribution on each of the map. ly explored providing timber for shipyards and smelters The Courland map (Karte von Kurland von C. Neu- (Zunde 1999). Later, in 1795, it was incorporated into mann) is the oldest source for the forest area distribution the Russian Empire, but Zemgale remained dominated in Zemgale (Table 1, Figure 2a). This semi-topographical by the local German-speaking minority until 1919. Since map was first published in 1833 in Jelgava. The exact date the 19th century, the depopulation (Skujenieks 1938) of and the circumstances of survey for this map are unknown rural land due to industrialization led to the afforestation (Kavacs 1994). We consider that the forest area distribu- of Zemgale. These processes were intensified in a series tion on the Courland map was established before 1790, of wars, of which the most destructive was World War I. since the contours of the Golf of Riga, as well as the style Shortly before World War II, the region was incorporated and contents of the map are similar to those in the Atlas of

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Table 1. Characteristics of the maps used in the study

Survey. Drawing Min. forest Geod. Map name Ed.1 Survey2 Scale accuracy accuracy patch points3 (m)4 (m)5 (ha) Courland map 1833 ca. 1790 1:296 000 506 1265 178 9 3-verst map 1865 ca. 1860 1:126 000 629 546 76 0.6 Latvian army map 1924 ca. 1910 1:75 000 - - 45 0.3 Forest inventory map - 2010 1:10 000 - - 6 0.1

1The date of the first edition of map sheets. 2The survey date indicates the year, when the forest distribution had become fixed. 3The geodesic points were used to link the oldest two maps to the Latvian army map and optimized for local accuracy through spline transformation. 4The root-mean-square error after the 1st order transformation was used to estimate the surveying accuracy before the spline transformation. 5The drawing accuracy of the real world is derived from the scale by assuming a drawing accuracy of 0.6 mm on the map.

Livland (Atlas von Liefland, a map of an adjacent region map started in 1845. The sheets of the 3-verst map used published by Ludwig August Mellin in 1791). The Cour- for our study are dated by 1865, but only administrative land map differs markedly from the later ones made by boundaries were updated and railways added that year Russian cartographers after 1790, e.g. a detailed military (www.maps4u.lt. 2013). We therefore estimated the final map along Russian-Prussian border (1799), a special map mapping of the forest area in Zemgale took place as late of Western Russia on a scale of 10 verst per inch (1821- as 1860. 1839) and a special map of Livland (1839). The survey The Latvian army map (Table 1, Figure 2c) was pub- for the Courland map may have been even earlier, because lished in 1924-1931. For Zemgale this map was repro- the Ozoldarzs, a 19 ha old oak-dominated forest patch duced from the Russian Empire 2-verst map on a scale of (marked in Figure 2 with arrows), is absent on the map. 1:84,000 (Kavacs 1994), based on a survey before 1910. It was planted in about 1776 (Ikauniece et al. 2012). The The advantage of the Latvian army map is that it is avail- delay in publishing the Courland map could be due to the able georeferenced for the whole study area. To vectorize tension between the German administration and Russian the forest area distribution, we also used some original authorities at that time. The issue of the Atlas of Livland in sheets of the 2-verst map and some sheets reproduced Germany provoked the arrest of Count Mellin and the issu- from it by the German Army and the Red Army (RKKA). ing of a special decree by the Russian Tsar Pavel I banning the publication of maps of the Russian Empire abroad. Georeferencing and estimating accuracy of histori- The 3-verst map of the Russian Empire (The military cal maps topographical map of the European Russia) is the second The digital copies of sheets of the Courland map and source for estimating the forest area distribution in the the 3-verst map were georeferenced in ArcGIS software study area (Table 1, Figure 2b). The preparation for this (ESRI 2011) to the Latvian Army map using territorial

Figure 2. Examples of maps used in this study: A) Courland map (issued 1833, surveyed in ca. 1790); B) 3-verst map of Russian Empire (issued 1865, surveyed in ca. 1860); C) Latvian army map (issued 1927, surveyed in ca. 1910). The arrows show the loca- tion of the Ozoldarzs, which was planted in 1776

2016, Vol. 22, No. 1 (42) ISSN 2029-9230 5456 BALTIC FORESTRY VALIDATION OF MEDIUM-SCALE HISTORICAL MAPS OF SOUTHERN LATVIA /.../ A. FESCENKO ET AL. features such as castles, palaces, manors, churches and sity and age (see an example in Figure 3). According to stone bridges as ground control points. More than 500 the forest management principles adopted in the 1920s, control points were identified on the Courland map for the data were obtained by surveying each stand once ev- the whole study area, and more than 600 on the 3-verst ery 10 to 20 years, followed by a limited check of data map (Table 1). We used spline transformation to improve between stand-wise inventories. The minimum area that the local accuracy of the maps (Kramer et al. 2011). To can be designated as a stand is set to 0.1 ha, although the estimate the local accuracy of the Courland map and the mean stand area in Zemgale is 2.1 ha (State Forest Service 3-verst map before the spline transformation, we used the 2010). For the study area, the database contains a total of same control points moving sheets of the maps so that 94,886 stands, from which 39,875 are boreal coniferous residual errors between all pairs of control points on the forest stands, 51,475 are boreal deciduous forest stands, maps, of which the Latvian Army maps are considered to and 3,536 are nemoral deciduous forest stands. be the most exact, would be minimal (1st order transfor- mation). The root-mean-square sum of all the residuals, Forest continuity map indicating the mean mismatching between a pair of con- Contours of forested areas traced on the historical trol points, was proportional to the local inaccuracy of a maps were vectorized in ArcGIS software (ESRI 2011) less accurate map. The maximum accuracy of the maps to a set of polygons, which were dated according to the after the spline transformation was limited by the drawing estimated final year of a corresponding survey (Table 1). accuracy. It was calculated for a particular map scale, S, By projecting historical polygons onto polygons of pres- as ∆w/S by assuming forest contours width, ∆w = 0.6 mm, ent-day forest stands, we assigned to each stand new at- on each map. The third way to estimate a map accuracy tributes, which showed whether the stand was inside of we used involves finding the smallest forest patch area any forest polygon from a historical map. In case the stand depicted on the map. The results of these estimates are was partially intersected with a historical forest polygon, shown in Table 1. it was split into previously forested and non-forested parts. Therefore, a new more granular map of current for- Present-day data ests was produced, where presence or absence of forest The present-day data (2010) on the forest area dis- cover at each of the three time points was attributed to all tribution, stand area, and tree species composition were polygons. Polygons with area less then 0.1 ha were disre- taken from the State Forest Service (SFS) forest inven- garded for further analysis. We obtained a detailed map tory database (State Forest Service 2010), which contains showing the forest continuity by dividing forests into four records of forest land with the GIS database (Forest in- classes: 1) ancient forests, woodlands with forest continu- ventory map, Table 1). The database provides information ity more than 220 years (forest cover in 1790, 1860, 1910, summarized in more than 120 attribute fields on both state and 2010); 2) woodlands with continuity 150-220 years and private forests. Unlike many European countries, (forest cover in 1860, 1910, and 2010); 3) woodlands with where total forest inventories are performed on a statisti- continuity 100-149 years (forest in 1910 and 2010); and cal inventory basis (Brack 1997), in Latvia about 97 % of 4) recent forests, woodlands forested continuously for the forests are divided into stands: management units of less than 100 years (forest cover in 2010 but not forested similar growing conditions, tree species proportion, den- in 1910). For additional analysis of the forest continuity

Figure 3. A) An example of the Forest inventory map of a forest patch near Platone village. B) NASA satellite image of the stands structure (Google Earth, 2013). C) The forest continuity map of the forest patch

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Data analysis Temporal pattern of forests Firstly, total areas of forest cover, as well as forest Changes over time in the forest area of Zemgale areas with different forest continuity, were calculated in for the four time horizons 1790, 1860, 1910, and 2010 four time slices using standard GIS functionality. To ana- are plotted in Figure 4a. The overall percentage of forest lyze deforestation during a period between two succes- cover during the study period remained within 27 % ± sive time horizons, total area of forest polygons that were 4% of the study area with peaks in 1860 and 2010. Con- depicted on the previous map and disappeared on the next tributions of the time horizons (grey colours in Figure 4a) map was calculated and divided by number of years in the to the present-day forest area were nearly similar, which period. Similarly, total area of forest polygons that were were 25 %, 23 %, 16 %, and 36 % for years 1790, 1860, depicted as open lands on the previous map was used to 1910, and 2010, respectively. Area of forest cover that calculate afforestation during the corresponding period. presented on the same place since a certain time horizon Three forest types according dominant tree species decreased along the time axis in exponential-like trajecto- were analysed separately: (1) boreal coniferous Pinus syl- ries, which means that new woodlands became deforested vestris, Picea abies; (2) nemoral deciduous Quercus ro- more quickly than older ones. Indeed, only 25% of the bur, Fraxinus excelsior, Tilia cordata, Ulmus glabra; (3) areas deforested from 1860 to 1910 were presented as a boreal deciduous Betula pendula, Populus tremula, Alnus forest in 1790; another 75 % were afforested after 1790. incana, Alnus glutinosa. One dominant tree species from From the areas deforested from 1910 to 2010, only 9 % the 20 available was defined in the SFS database for each had continuous forest cover since 1790, 28 % since 1860, stand as that making up the largest tree volume. and 63 % since 1910. Land-use turnover over the last 100 The number of tree species in each of 94 886 stands years has decreased approximately twice in comparison was extracted from the SFS database taking into ac- with the previous periods (Figure 4b). count all tree species including ones of individual trees. It should be noted that according to forest management Spatial pattern of forest continuity practice in Latvia, only one tree species is intentionally Woodlands with different continuity of forest cover planted in one stand until now, while other species have were unevenly distributed between forested, open, mosaic seeded naturally. The arithmetic mean value of tree spe- lowlands, and mosaic highland ecoregions (A, B, C and cies richness per hectare and mean stand area with stan- D in Table 2, Figure 5). Large forest tracts in ecoregion A dard errors were calculated for each forest type and for formed a dense matrix of mostly ancient coniferous Pinus each forest continuity class by applying the ‘select by lo- sylvestris dominated forests with adjacent recent forests cation’ method of ArcGIS to stands within or intersecting dominated by boreal deciduous tree species. Ecoregion a forest continuity class. The mean stand area (an inverse B on Zemgale plain in the southern and central part of of stands density) indicates a diversity of particular forest the study area is characterized by fertile soils and inten- subareas with similar light transmission, humidity, fertil- sive agricultural activity forming an open landscape pat- ity and tree species composition, and consequently, with tern with scattered old deciduous forest patches. Evenly similar forest-dwelling species pool, i.e. it is related to scattered woodlands of different forest continuity charac- diversity of habitats in forests. terized ecoregion C in the western part; such a mosaic Though the forest continuity is a continuous vari- pattern formed on the western side of the East Curonian able, its real values were hardly estimated because any upland with elevations from 60 to 150 m a.s.l. High pro- new forest area on a map had been appeared during a pe- portion of recent forests dominated by boreal deciduous riod, which is unknown for the very first map and varies tree species has been found in ecoregion D in the eastern for the later maps. Therefore, for bivariate and regression part of Zemgale. The both mosaic landscapes were char- analyses we made an approximation of the real forest con- acterized by the lower mean stand area and mean tree spe- tinuity by an equidistant successional series. To quantify cies richness (Table 2). distortion (i.e. deviation from a simple trajectory) of the metrics dependencies on the forest continuity, they were Mean stand area and tree species richness fitted with quadratic regression models, and the coef- The mean stand area is positively correlated on for- ficients of determination (multiple R-squared) were ob- est continuity for all forest types (Figure 6a), while the

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Figure 4. a) Changes over time in the forest area in Zemgale in the four time horizons: 1790, 1860, 1910 and 2010. The percentage of the total study area is shown on the left y-axis, while the right y-axis shows the percentage of the current forest. Gradation of colours indicates proportions that have had continuous forest land use since: 1790, 1860, 1910 or after 1910. The numbered circles depict proportions of forest cover from available historical data for Dobele and Bauska districts (Орановский 1862, Švābe et al. 1934). b) Afforestation and deforestation rates during the three study periods

Figure 5. Spatial distribution of woodlands, divided into four classes according to the forest continuity. The capital letters and dashed lines indicate ecoregions correlation is more pronounced for deciduous tree spe- ests). All the presented dependencies fitted with simple 2 cies (ρs.cor > 0.16, p-value < 0.0001). The mean stand area quadratic model showed determination coefficients R was for about 18% larger in woodlands with longer forest close to 1, i.e. they were not statistically distorted. continuity irrespective of the forest type. The tree species richness was also found positively dependent on the forest Discussion continuity in stands with dominant boreal deciduous tree species (ρs.cor = 0.15, p-value < 0.0001, Figure 6b). The Validation of historical maps for multi-temporal tree species richness of the nemoral deciduous forests was analysis about for 35% (for all continuity classes) higher than that When dealing with historical maps, especially pro- of the coniferous woodlands, and both these forest types duced before the 19th century, a question may arise about had weak correlation with the forest continuity (p-values: their validity for scientific applications since such maps 0.99 for coniferous and 0.04 for nemoral deciduous for- are not obviously trustworthy. First of all, they should be

2016, Vol. 22, No. 1 (42) ISSN 2029-9230 5957 BALTIC FORESTRY VALIDATION OF MEDIUM-SCALE HISTORICAL MAPS OF SOUTHERN LATVIA /.../ A. FESCENKO ET AL. supported by other historical data. The available historical 2011). Such woodlands grow on land that is not suitable statistical forest cover data of Bauska and Dobele districts or profitable for agricultural use, thus it is reasonable to (see Figure 4a, circles 1-3, Орановский 1862, Švābe et al. expect that they have much longer forest continuity than 1934) are consistent with our map-based analysis of for- the 220 years. est cover: in 1856, the forest area in Bauska and Dobele The forest continuity derived from the historical districts was 30.3% (circle 1), in 1929 - 25.3% (circle 2), maps and linked to diversity metrics provides itself a vali- and in 1931 - 26.2% (circle 3). The discrepancy can be dation test of the maps: the smooth and simple curves of explained by the incomplete overlap of the administrative the dependencies (see Figure 6) exclude any significant units in the study area during the different time periods: impact of cartographic inaccuracy on the obtained forest the Bauska and Dobele districts had different borders in cover distributions. Heterogeneity of maps is not neces- the 18th and 19th centuries but in the 20th century, the Jel- sary a drawback. Conversely, it randomizes any system- gava district became a separate unit. These changes in the atic errors due to cartographic methods excluding their forest cover during the studied period can be explained by impact on the analyzed historical land-use pattern. Local soils interacting with political, economic and social fac- inaccuracy of medium-scale historical maps is also mostly tors in Zemgale (Fescenko et al. 2014). random; consequently, its impact on analyzed properties Another evidence of the maps reliability is that the decreases inversely with size of a region. The undisturbed ecoregion with the highest percentage of the ancient for- dependencies can be due to the fact that the local inac- ests (see A in Table 2, Figure 5) is Pinus sylvestris domi- curacy/study area ratio of different cartographic sources nated, which confirms the link between forest continuity becomes compatible for the scale of 5,000 km2, making and coniferous forests (Eriksson et al. 2010, Tērauds et al. the maps useful for multi-temporal analysis.

Table 2. Diversity metrics and forest cover by forest continuity classes in ecoregions of Zemgale

Forest continuity Forest Mean tree Mean cover species stand Ecoregions >220 150..220 100..149 <100 * (% of richness area years years years years landscape) (species/ha) (ha) (%) (%) (%) (%)

Forested lowland A 67 2.82 1.65 38 20 10 32

Open lowland B 9 2.77 1.56 6 20 22 52

Mosaic highland C 36 2.71 1.33 12 22 19 47

Mosaic lowland D 39 2.47 1.18 5 12 17 66

* The ecoregions are marked in Figure 5 by capital letters. Values of the mean tree species richness and mean stand area are given with standard error less than 1 %.

Figure 6. a) Mean stand area by forest types vs. forest continuity. b) Mean tree species richness by forest types vs. continuity. The solid lines are quadratic regression models. Error bars designate the standard error. Coefficients of determination, R2, for quadratic regression models and Spearman correlation coefficients, ρ, are shown for each forest type

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Forest continuity versus mean stand area and tree Proposed forest management for best biological species richness value Our analysis reveals a positive dependence of the In Zemgale, as in many other regions of Europe, mean stand area on forest continuity, which evidences of nemoral forests have become rare due to competition a greater fragmentation of stands within post agricultural with agriculture for fertile soils (e.g. Wulf et al. 2010). forest areas (Wagner et al. 2000). This could be explained Today, the high ecological value of such forests is rec- by various human activities before and during the gradual ognized, pointing to the need to preserve or restore those process of afforestation (Lunt and Spooner 2005), while (Schweitzer et al. 2014). However, in forest management long-term forest cover tend to eliminate human traces as direct afforestation with nemoral tree species requires a the stands in the long run take on the pattern formed by fertile land favourable for agricultural use (Valtinat et al. abiotic factors, such as soil or relief (Turner 2005). 2008, Ikauniece et al. 2013). Alternative of restoration is, The study shows a monotonous increase of tree spe- therefore, to promote the natural transformation of early cies richness with forest continuity of boreal deciduous successional forest dominated by Populus tremula, Betula stands. We explain it by fertility of the soil, which sup- pendula, Alnus incana to nemoral forests with high biolog- ports tree species diversity (Rosenzweig and Abramsky ical value. The boreal deciduous tree species can be used 1993, Austin et al. 1996). The boreal deciduous tree spe- as nurse plants (Ren et al. 2007) facilitating the growth cies are early successional (pioneer) species, which easy and development of target plant species (i.e. nemoral de- colonize unforested areas due to their ruderal life-history ciduous tree species), as they prepare benign microhabi- strategy (Brzeziecki and Kienast 1994). Such areas usually tats more favourable for seed germination and/or seedling are not favourable for germination and growth of competi- recruitment than depleted agricultural lands or clearings. tive nemoral tree species (Brzeziecki and Kienast 1994), Similarly, early successional nurse shrubs in Mediterra- allowing the boreal deciduous tree species to form dense nean region had facilitative effect on the establishment homogeneous stands (Aosaar et al. 2011). In a long term, of late-successional woody species (Gómez-Aparicio et i.e. over several stand rotation periods, forest soils become al. 2004). A hundred and more years old stands, which more fertile due to the increased stock of organic matter are currently dominated by boreal deciduous tree species, (Gimmi et al. 2013), which provides new niches for com- should be given priority as primary sources of nemoral petitive tree species (Chesson 2000), and the diversity of forests, and therefore appropriately managed. We be- boreal deciduous stands increases reaching the tree spe- lieve that cautious thinning and single stem management cies richness camparable with nemoral deciduous stands (Boncina 2011) will facilitate the process of formation of (see Figure 6b, >220 years). Previous studies of plant spe- nemoral deciduous forests, while clear cutting with refor- cies richness have also shown monotonically increasing estation, which is still widespread in Latvia, impedes their dependence for a 60-year successional series (Inouye et formation by slowing down the process of soil organic al. 1987), and increasing then flattening out with no ap- matter accumulation (Callaway 1995). parent decrease dependence for a 250-year successional series (Nicholson and Monk 1974). The humpbacked spe- Conclusion cies richness-curve (according to Tilman and Pacala 1993) would have a place if a few highly competitive species We have shown that the heterogeneous medium- monopolize all of the resources, when productivity of for- scale historical maps provide consistent information on est soil becomes higher (Graham and Duda 2011). Our the historical forest area pattern at the scale of 5,000 km2, study has obtained such dependence only for coniferous and that noone unknown factor related to imperfection forest stands, where small decrease of tree species richness of such maps significantly distorts dependencies of the occurred after 220 years of continuous forest land use. The diversity metrics on the forest continuity. Such regional dominance of coniferous tree species indicates that such studies, based on medium-scale maps, diminish the ef- forest communities occur on poor and mesotrophic soils fects of the specific sites and can be particularly useful with a limited possibility to host large number of species. in areas, where other sources of information are lacking. Meanwhile the tree species richness of nemoral deciduous They could, therefore, be extremely useful to test ecologi- forests has neither increasing nor decreasing parts, which cal hypotheses (Eriksson et al. 2010) and to guide future can be due to either the insufficiently long studied period, research, restoration and conservation activities (Egan or depressed competition ability of nemoral tree species and Howell 2001, Lunt and Spooner 2005). In particular, on the northern border of the nemoral vegetation zone. our map-based study has shown for Zemgale region that: Besides, widespread nemoral forests, known from the his- 1) turnover rate between forest and agricultural land-uses torical records, developed through the interactions of for- is more rapid in recent woodlands than in ancient ones; est ecosystems with herds of wild or domestic ungulates, 2) the mean stand area is larger in woodlands with lon- (Vera 2000) which today practically no longer exist. ger forest continuity regardless to the forest type; 3) the

2016, Vol. 22, No. 1 (42) ISSN 2029-9230 6159 BALTIC FORESTRY VALIDATION OF MEDIUM-SCALE HISTORICAL MAPS OF SOUTHERN LATVIA /.../ A. FESCENKO ET AL. tree species richness of the coniferous woodlands is lower Brzeziecki, B. and Kienast, F. 1994. Classifying the life-history than that of the nemoral deciduous forests, while in the strategies of trees on the basis of the Grimian model. Forest Ecology and Management 69(1): 167-187. both forest types tree species richness is weakly depen- Brack, C. L. 1997. Forest Inventory in the 21st Century. Proceed- dent on the forest continuity; 4) the tree species richness ings of the Australian and New Zealand Institute of Foresters in stands dominated by boreal deciduous (early succes- Conference “Preparing for the 21st Century”. 21 - 24 April, sional) trees positively depends on the forest continuity, 1997. Canberra, ACT. 329, 335 pp. Callaway, R. M. 1995. Positive interactions among plants. The Bo- and they regain the properties of nemoral deciduous for- tanical Review 61(4): 306-349. ests in terms of tree species richness if forest cover lasts Chesson, P. 2000. Mechanisms of maintenance of species diversity. over two centuries. Annual Review of Ecology and Systematics 31: 343-366. Our results may promote the interests of ecologists De Keersmaeker, L., Onkelinx, T., De Vos, B., Rogiers, N., Vandekerkhove, K., Thomaes, A., De Schrijver, A., Hermy, and forest managers in using historical maps to identify M. and Verheyen, K. 2014. The analysis of spatio-temporal and protect ancient forests, to estimate carbon stocks in forest changes (1775–2000) in Flanders (Northern Belgium) forests, as well as to attract attention to a value of early indicates habitat-specific levels of fragmentation and area successional forests with long continuity. Further research loss. Landscape Ecology 30: 247–259. Egan, D. and Howell, E. 2001. The Historical Ecology Handbook: will be conducted to study the links between the forest A Restorationists Guide to Reference Ecosystemes. Island continuity and protected areas, as well as the response of Press, 458 pp. forest habitats, species and functional traits on land-use Eriksson, S., Skånes, H., Hammer, M. and Lönn, M. 2010. Cur- change. rent distribution of older and deciduous forests as legacies from historical use patterns in a Swedish boreal landscape (1725–2007). Forest Ecology and Management 260: 1095– Acknowledgements 1103. ESRI. 2011. ArcGIS Desktop: Release 10. Redlands, CA: Environ- We would like to thank Matthias Bürgi and Jānis mental Systems Research Institute. Fescenko, A., Nikodemus, O. and Brumelis, G. 2014. Past and Donis for helpful advice and discussions, and Silvia contemporary changes in forest cover and forest continuity in Dingwall for the linguistic revision of the manuscript. relation to soils (southern Latvia). Polish Journal of Ecology Comments of three anonymous reviewers helped to im- 62(4): 607-620. prove the manuscript. This work was supported by the Foster, D., Motzkin, G. and Slater, B. 1998. Land-use history as long-term broad-scale disturbance: regional forest dynamics European Social Fund as part of the project “Support in central New England. Ecosystems 1: 96–119. for Doctoral Studies at the University of Latvia” and Galeniece, M. 1959 - Karta rastitelnostji Latvijskoj SSR [Geobo- of the ERAF project 2010/0247/2DP/2.1.1.1.0/10/APIA/ tanical Map of the Latvian SSR]. In: Rastitelnostj Latvijskoj VIAA/133Silava10/31/2011. SSR. Izdatelstvo Akademii Nauk Latvijskoj SSR, p. 29-45 (in Russian). Gimmi, U., Lachat, T. and Bürgi, M. 2011. Reconstructing the References collapse of wetland networks in the Swiss lowlands 1850– 2000. Landscape Ecology 26: 1071–1083. Ahti, T., Hämet-Ahti, L. and Jalas, J. 1968. 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TADEUSZ CIUPA, ROMAN SULIGOWSKI AND GRZEGORZ WAŁEK* Institute of Geography, Jan Kochanowski University in Kielce, Świętokrzyska 15, 25-406 Kielce, Poland *Corresponding author: e-mail: [email protected]; tel.: + 48-413496409.

Ciupa, T., Suligowski, R. and Wałek, G.* 2016. Use of GIS-Supported Comparative Cartography and Historical Maps in Long-Term Forest Cover Changes Analysis in the Holy Cross Mountains (Poland). Baltic Forestry 22(1): 63-73.

Abstract

In recent years forest research benefits from access to archived cartographic materials and geographic information systems technology, which both allow to analyze the processes of forest cover changes over time. Available digital elevation models (DEMs) and soil maps make it possible to consider terrain relief and soils characteristics in the research. The present paper analyzes changes of forest cover in the Holy Cross Mountains (central Poland) within the period of 1800–2011 and they relation to altitude and slope gradient classes as well as to genetic soil groups. The source materials consist of topographic maps created in 1800, 1900, 1930, 1983 and thematic maps: Polish Sozological Map in 1: 50,000 scale from 2011, Soil Map of Poland in 1: 300,000 scale and SRTM3 digital elevation model. Scanned maps were georeferenced to metric coordinate system and then forest areas were digitalized by on- screen vectorization. Digital elevation model was used to delineate elevation and slope gradient classes. Finally, the overlay geopro- cessing methods were used to analyze the areas of forest cover changes in time, also in addition to altitude zones, slope gradient and genetic soil type classes. Forest cover indicator (%) and mean annual index of forest cover change (ha·year-1) have been calculated. Forest cover was the highest at the beginning of the study period in 1800 and the lowest in 1930. The decrease in forest cover in this period equaled 35.3 %. A slow process of recovery began in 1930 and continues till today. However, the coverage noted in 1800 has not yet been achieved. Also forest cover stability analysis has been performed. Today forest areas of very high stability cover about 21 % of the Holy Cross Mountains and 49 % of the area covered by trees in 1800. The present analysis has been performed with the use of GIS-supported comparative cartography and historical maps, which have significantly improved the investigations of long-term forest cover changes.

Keywords: forest cover changes, comparative cartography, relief, soils, central Poland

Introduction 2012). The rapid progress of forest cover changes research is primarily due to recent development in geographic in- The identification of changes in forest cover is a key formation systems (GIS). This makes it possible to per- part of many environmental, sociological, and economic form accurate measurements using various source materi- analyses the results of which could be applied in forestry. als across a wide array of administrative, topographic and Numerous research publications of different topics have hydrographic regions, both large and small. tackled this issue from various spatial and temporal per- There are many research papers on forest cover spectives. Recently, some important papers describing changes that utilize historical maps and methods of com- long-term forest cover changes have been published in parative cartography (i.a. Więcko 1986, Kienast 1993, Pe- different parts of Europe (i.a. Wulf et al. 2010, Puddu et tit and Lambin 2002, Kozak 2003, Skalos et al. 2012). The al. 2012, Skalos et al. 2012). At the same time, the fol- use of such cartographic materials in land cover research lowing papers have addressed the issue of forest cover is well established because they are often the only source change in Poland: the Polish Carpathian Mountains in of long-term data on land cover, in particular from the last period 1800–2000 (Kozak 2010); the Kalisz Plateau in centuries. In Poland this type of research was conducted 1830–1998 (Markuszewska 2005); the Northern Carpath- already in the 1930s and included the Holy Cross Moun- ians in 1930–1990 and 1987–2000 (Kozak et al. 2007a,b); tains. A few decades later, a broad review of papers based Tuchola Pinewoods in 1938–2000 (Giętkowski 2009); the on historical maps analysis was published (Szymański Western Bieszczady Mts. in 1854–2004 (Gielarek et al. 1979). Forests in the Holy Cross Mountains sparked 2011); West Pomerania in 1618–2006 (Kunz 2012); Kro- the interest of researchers already in the 19th century toszyn commune in 1793–2005 (Macias and Szymczak (Barański 1972). A review of papers written over the last

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200 years has made it possible to identify two principal types and resulting soil agricultural potential (MacDonald research approaches in the area of forest cover analysis. et al. 2000, Wulf et al. 2010). This problem is scarcely The first approach addresses forest cover changes in the mentioned in forest cover change analysis but it has been context of historical, political, and economic conditions decided to tackle this determinant by taking into account (Szymański 1993). The second approach addresses en- a large variety of soil groups of different fertility existing vironmental determinants (Reniger 1956, Kowalkowski in the analyzed area of the Holy Cross Mountains. 2000). This environmental approach corresponds to the The objective of this study is to analyze changes in the aim of the present paper. forest cover in the Holy Cross Mountains over the last 200 The recent availability of digital elevation models years in the context of spatial morphological determinants (DEMs) has created further opportunities for the explora- such as altitude and relief as well as soil-based factors, tion of land cover changes in addition to terrain morphol- with the use of the comparative cartography methodology. ogy. Papers that utilize DEM and its derivatives in forest The present paper tries to answer the following questions: cover analysis include: the Swiss Alps (Hörsch 2003), What area was affected by changes in forest cover during the Andes (Bader and Ruijten 2008), Tuscany (Geri et each studied time interval? How did morphological and al. 2010), Simien National Park in Ethiopia (Wondie et soil-based factors influence these changes? What advan- al. 2011), the Carpathian Mountains in Poland (Kozak et tages does the use of GIS-supported comparative cartogra- al. 2007b), the Sudety Mountains in Poland (Szymura et phy and historical maps bring into forest research? al. 2010) and others. A number of researchers have stud- ied forest cover and its relationship with altitude, natural Materials and Methods succession, and human impact in Europe (Didier 2001, Hörsch 2003, Kozak 2003, Geri et al. 2010). The impact The source materials used in the research consist of of relief and non-environmental factors on forest cover in scanned maps, both new and historical: Map of Western the 19th and 20th centuries in the context of pan-European Galicia by Anthony Mayer von Heldensfeld, Karte Des trends is one of the latest research topics (Kozak 2010, Westlichen Russlands, Tactical Map of Poland, Polish Szymura et al. 2010). Research has shown that forest General Staff Map, Polish Sozological Map (Table 1). Old cover changes in mountain areas are dependent on soil maps were published on the basis of field mapping, which

Table 1. Maps used to analyze the forest cover

Year RMSE of GCPs Number of Forest Map Scale location (m) sheets representation topicality issue min – max

Map of Western Galicia by Anthony Mayer von Coloured polygons filled Heldensfeld 1800 1801–1804 ~1:28 800 16 –* with tree signatures (source: Österreichisches Kriegsarchiv, Vienna)

Karte Des Westlichen Polygons filled with tree Russlands 1900 1914–1915 1:100 000 9 31,5 – 129,8 signatures; dotted line (Map Archive of Geographic- boundaries Military Institute)

Polygons filled with tree Tactical Map of Poland (Map signatures indicating Archive of Geographic- 1930 1931–1934 1:100 000 9 29,4 – 63,0 deciduous, coniferous or Military Institute) mixed forest; dotted line boundaries

Polish General Staff Map Coloured polygons with (Archive of Institute of dotted line boundaries; text 1983 1985–1988 1:50 000 14 10,4 – 23,7 Geography, Jan Kochanowski indication of forest species University, Kielce) composition

Polish Sozological Map Coloured polygons (Main Centre of Geodetic and 2011 2011–2012 1:50 000 14 – showing protected and Cartographic Documentation, other forests Warsaw)

* – calculation was unnecessary because of the Thin Plate Spline transformation function used

2016, Vol. 22, No. 1 (42) ISSN 2029-9230 6466 BALTIC FORESTRY USE OF GIS-SUPPORTED COMPARATIVE CARTOGRAPHY AND HISTORICAL MAPS /.../ T. CIUPA ET AL. could have been performed years before the map publica- On the basis of georeferenced map images, forest ar- tion. On the basis of maps timeliness, forest cover was eas were digitalized by on-screen vectorization method to analyzed in the following years: 1800, 1900, 1930, 1983, the shapefile format, starting from the latest to the oldest 2011 and in the four time periods between them. Selection map, according to the comparative cartography methods of the source material from the 19th century to the first half of retrogression and elimination (Stevens and Tree 1951, of 20th century was very limited and therefore the present Wilson 2005, Plit 2008, Podobnikar 2010). Many publi- study is based on the only map series available for the pe- cations describe similar methodological issues connected riod and covering the area in question. It has been decided with forest cover analysis based on historical maps (i.a. to use 1:50,000 scale maps for the two last time periods to Kozak 2003, 2010, Wulf 2010, Gielarek et al. 2011, Kunz allow the most reliable comparison. Therefore, taking into 2012, Skalos et al. 2012). consideration their properties and the information about The morphological analysis was based upon the all the maps used taken from the literature, it can be stated SRTM3 DEM in raster format, created during the Shuttle that the general accuracy of the study is comparable to Radar Topography Mission in three arcsecond (90 m) res- 1:50,000 scale map. olution (Shuttle… 2004, Farr et al. 2007). This DEM was The fundamental step in data preparation was geo- converted into the Polish State Coordinate System 92 and referencing of the maps images. In this process, scanned, used to identify six altitude zones (under 250, 250–300, high-resolution images of historical maps were trans- 300–350, 350–400, 400–500, above 500 meters a.s.l.), formed in GIS into metric coordinate system (Poland designated by the elevation histogram analysis. As a re- CS92). It was performed with the use of a transformation sult of slope map calculation (Zevenbergen and Thorne based upon identical ground control points (GCPs), which 1987), six slope gradient categories were identified: 0–1, are stable in time and clearly defined objects or places 1–3, 3–6, 6–10, 10–15, >15o (all in degrees) according marked as signatures on each map series. In the study, the to the mechanism of surface water erosion processes in following GCPs have been used: churches, crossroads, Poland (Józefaciuk and Józefaciuk 1996). bridges and hilltops. The Karte Des Westlichen Russ- As far as soils are concerned, forest cover change lands, Tactical Map of Poland and Polish General Staff analysis was based on the above listed soil types. Soil cov- Map were georeferenced using Helmert transformation er was mapped using the IUSS, ISRIC, and FAO (2006) method, with 14 to 18 GCPs distributed evenly on each classification systems. Seven generalized groups of soils map sheet. The root mean square error (RMSE) of GCPs (formed on carbonate rock, sand, clay, loess, alluvial dust location on the output maps did not exceed 130 m (Table deposits, boggy and alluvial deposits, non-carbonate rock 1). This was in the case of one map sheet of Karte Des Westlichen Russlands in the 1:100,000 scale. The oldest of the analyzed map series – Map of Western Galicia, as the one with the biggest possible errors resulting from the time of its production, was transformed with a nonlinear method called rubber-sheeting, using thin plate spline functions (TPS). This method is used for georeferencing of maps and other spatial data with potentially big and unevenly distributed localization errors (White and Grif- fin 1985) – such as those on the maps from the beginning of the 19th century. The effect of this method is that the GCPs on the output georeferenced map are situated ex- actly in the same place, where they are in reality, and the space between them is interpolated to fill all the area. In this case, calculation of RMSE of the resulting GCPs was unnecessary. Map sheets from this series have the big- gest possible errors, even though they were made in the 1:28,800 scale. The Polish Sozological Map already had spatial adjustment in the desired coordinate system so we did not perform georeferencing for this data. The signatures representing forests are different on each map series; however, all of them are easy to distin- Figure 1. Examples of the historical maps used in the study along guish and allow to determine forest reach. An example of with the forest signatures: 1 – Map of Western Galicia by Antho- different cartographic signatures used to present forest on ny Mayer von Heldensfeld; 2 – Karte Des Westlichen Russlands; the maps is shown on Figure 1. 3 – Tactical Map of Poland; 4 – Polish General Staff Map

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Figure 2. Location of the Holy Cross Mountains. Legend: 1 – contemporary forests

2016, Vol. 22, No. 1 (42) ISSN 2029-9230 6668 BALTIC FORESTRY USE OF GIS-SUPPORTED COMPARATIVE CARTOGRAPHY AND HISTORICAL MAPS /.../ T. CIUPA ET AL. ztocze hill range. The Latin name Abietetum polonicum ests occupied 619.2 km2 (33.9 %) (Table 2). Forest cover emphasizes its endemic character. Beech and fir are the increased by 119.5 km2 between 1930 and 2011, with a most important forest stands component in the Łysogóry mean annual forest growth rate of 153.2 ha∙yr-1. There- Range, and are protected in the Świętokrzyski National fore, forest cover in the study area has not returned to its Park (Danielewicz 2000), where they grow on the north- state from the year 1800. For comparison, forest cover ernmost border of their natural range in Central Poland in Poland reached 29.3 % in 2011 and exhibits a growth (Matuszkiewicz and Matuszkiewicz 1996). Below the trend (Forestry 2013). borderline of Abietetum polonicum, forest areas of this re- gion host all most important forest tree species in Poland. Morphological determinants These lower altitudes are covered with pine forests as well Both deforestation and afforestation processes were as hornbeam and oak forests, while valleys feature sub- identified for each studied altitude zone in the period of montane riparian forests (Trampler et al. 1990). Significant human impact on forests in the Holy Cross Mountains dates back to Roman times. Ancient miners and ironworkers toiled in the region. Logging was a common practice (Orzechowski 1991). Permanent set- tlements emerged in the region in the Early Middle Ages and soon followed agriculture with deforestation in river valleys and on loess slopes. Glass was manufactured in the region between the 16th and 18th century, consuming large quantities of beech wood. This led to decreased bio- diversity and a resurgence of fir in the forests of the Holy Cross Mountains (Wyrobisz 1966, Wijaczka et al. 2004).

Results

Forest cover area in the Holy Cross Mountains was the greatest at the beginning of the study period (around the year 1800), 772.5 km2, which was 42.3 % of the total area of the region (Figure 3A, Table 2). This measure- ment was based on the map in the largest scale, therefore, the derived forest reach, in this paper treated as the forest cover changes starting point, could be considered as very reliable. Forest cover decreased to 510.8 km2 by the year 1900, and 499.7 km2 by 1930 (Figure 3B, Table 2). Hence, forest cover was reduced by 35.3 % between 1800 and 1930. The mean annual rate of deforestation in the period of 1800–1930 was -209.8 ha∙year-1. A slow increase in for- est cover was observed since 1930 (Table 2). Forest cover in the study area increased to 554.7 km2 (30.4 %) by 1983. The rate of increase between 1930 and 1983 was 103.8 Figure 3. Forest cover in the Holy Cross Mountains in 1800 (A) ha∙year-1. After 1983 the rate of afforestation reached and changes in the periods 1800–1930 (B) and 1930–2011 (C). 230.4 ha∙year-1. In 2011, in the Holy Cross Mountains for- Legend: 1 – forests, 2 – afforestations, 3 – deforestations

Table 2. Selected characteristics of forest cover in the Holy Cross Mountains between 1800 and 2011

Year 1800 1900 1930 1983 2011 28.0 27.4 30.4 Forest cover (%) 42.3 33.9 2 510.8 499.7 554.7 Forested area (km ) 772.5 619.2

Period 1800–1900 1900–1930 1930–1983 1983–2011

Mean annual index -251.7 -37.0 +103.8 +230.4 -1 of change (ha∙yr ) (1800–1930: -209.8) (1930–2011: +153.2)

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1800–2011. Deforestation was found to be the greatest in variable relief ranging from -9.3 % for more than 15o to each altitude zone during the 19th century, with a maxi- -15.0 % for 3–6o. Deforestation was the greatest on slopes mum value of -16.9 % between 350 and 400 meters above with a gradient of 1–3o (128.4 km2). The decrease in for- sea level. The lowest rate of deforestation was noted over est cover in this gradient interval ranged from 36.9 % to 500 m a.s.l. (-1.1%). Deforestation in other altitude zones 22.8 % or 14.1 %. Areas of this type are almost ideal for ranged from -11.6 to -15.8 % between 1800 and 1900. agriculture, easily accessible, and relatively unaffected by The two lowest altitude zones (under 250 m and 250–300 surface water erosion. Deforestation continued to occur m a.s.l.) experienced deforestation until 1930, reaching until 1930 only in the two lowest terrain slope intervals. -18.7 % and -14.7 %, respectively, for the period of 1800– All other slope intervals were characterized by afforesta- 1930 (Figure 4). tion (Figure 5). Above 300 meters of altitude, deforestation was halt- ed by the year of 1900 and by 1930 afforestation perma- Soil determinants nently replaced deforestation in every altitude zone. This In the Holy Cross Mountains the most soils are trend continued until the end of the study period in 2011. formed on loess 33.4 %, while those formed on clay oc- The greatest increases in forest cover occurred at the low- est altitudes: 175–250 m, 5.3 % (1930–1983) and 4.9 % (1983–2011). The lowest increases were noted over 500 meters above sea level: 1.3 % and 0.7 %, respectively. It is worth noting that the largest increases in forest cover were recorded for 350–500 m a.s.l. in the period of 1930–1983 and less than 350 m a.s.l. in the period of 1983–2011. In- creases in the period of 1930–1983 were largely the result of the abandonment of overused and often poorly accessi- ble farmland – especially this situated on higher altitudes. Between 1983 and 2011, afforestation was related to natu- ral conditions, but simultaneously reinforced by Poland’s transition from socialism to capitalism in the early 1990s. Abandonment of farmland in the last three decades led to natural succession as well as to afforestation in some plac- es, but was not clearly related to analyzed altitude zones. Within the whole analyzed period, the largest forest share was observed in the areas with high slope gradi- ents. In the year 1800 forest cover ranged from 30.6 % for 0–1o to 87.7 % for more than 15o, in the year 1900 – from Figure 5. Forest cover (in percent) by terrain slope in six inter- 16.1 % to 78.4 %, while in 2010 – from 19.5 % to 87.6 %. vals (in degrees) for the Holy Cross Mountains in 1800, 1900, In the 19th century, deforestation affected areas with and 2011

Figure 4. Forest cover changes at selected altitude zones in the Holy Cross Mountains from 1800 to 2011

2016, Vol. 22, No. 1 (42) ISSN 2029-9230 6870 BALTIC FORESTRY USE OF GIS-SUPPORTED COMPARATIVE CARTOGRAPHY AND HISTORICAL MAPS /.../ T. CIUPA ET AL. cupy 24.4 %, and on sand 19.3 %. Other soil types do The time period 1900–1930 was characterized by on- not exceed 10 % of the total regions area (Table 3). For- going deforestation in the areas with fertile soils includ- est share was the largest in the areas featuring rocky and ing loess (-31.2 %), alluvial dust (-7.6 %), carbonate rock skeletal soil types during the 200-year study period and (-6.0 %), and clay (-1.1 %). However, forests growing on ranged from 83.2 % (1800) to 72.2 % (1900). Significant other soil types were already experiencing afforestation. forest cover was also noted for soils formed of alluvial This was especially true for sandy areas. Forest cover in- dust, ranging from 65.3 % in 1800 to 40.9 % in 1930. creased across all soil types after 1930, as measured by However, this type of forest cover occupied only about the mean annual index of change: 6.1 ha∙year-1 (carbon- 14 % of the area of the Holy Cross Mountains. In 1800 the ate rock soils), 38.0 ha∙year-1 (sandy soils) (Figure 6). The largest forested areas were noted for clay type soils (238.2 period 1983–2011 was characterized by even larger in- km2) and sand type soils (162.2 km2). creases in forest growth in clay type soils (63.9 ha∙year-1) Only negative mean annual rates of forest change and loess type soils (48.9 ha∙year-1). As Poland made the were noted for the period 1800–1900, for each soil group transition from socialism to capitalism in the early 1990s, (Figure 6), the largest were noted for soils formed on agricultural production decreased across large swaths of clay (-90.6 ha∙year-1) and loess (-56.5 ha∙year-1). This was degraded soils that had been used for over 100 years. largely the result of high demand for fertile land needed for agricultural purposes.

Table 3. Changes in forest cover in the Holy Cross Mountains between 1800 and 2011 in addition to soil parent material

Soil area 1800 1900 1930 1983 2011 Soil type km2 km2 % km2 % km2 % km2 % km2 %

carbonate rock 70.5 20.6 29.2 13.3 18.9 11.5 16.3 14.8 21.0 16.6 23.5 sand 352.2 162.2 46.1 109.3 31.0 111.6 31.7 131.7 37.4 150.2 42.7 clay 444.8 238.2 53.5 147.5 33.2 147.2 33.1 159.7 35.9 177.6 39.9 loess 654.6 141.2 21.6 84.7 12.9 75.4 11.5 82.3 12.6 96.0 14.7 alluvial dust 132.9 86.8 65.3 56.6 42.6 54.3 40.9 58.2 43.8 62.5 47.0

boggy and alluvial 40.8 15.7 38.4 5.7 14.0 5.9 14.5 9.0 22.1 11.6 28.3

non-carbonate rock and 129.6 107.9 83.2 93.5 72.2 93.9 72.4 99.0 76.3 104.8 80.9 skeletal

Figure 6. Changes in forest share for selected soil types found in the Holy Cross Mountains from the begin- ning of the 19th century. Soils formed on: 1 – carbonate rock, 2 – sand, 3 – clay, 4 – loess, 5 – alluvial dust deposits; 6 – boggy and alluvial deposits, 7 – non- carbonate rock and skeletal

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Forest cover stability countryside, lack of environmental laws and regulations, The most stable forest areas that exist continuously lack of general government oversight, as well as an onset since 1800 create a number of dense forest complexes that of industrialization. In addition, rural residents used wood spatially correspond to the course of mountain ranges in to heat houses (Guldon 2000). All of the above factors the region (Figure 7). Their total area is 382,6 km2, which produced abrupt changes in forest ecosystems by altering is 21 % of the total region area and 49 % of the area cov- their initial state, leading to an overall decline in tree stand ered by trees in time of the maximum forest cover reach in density. Other negative consequences included physical the analyzed period – at the beginning of the 19th century. weakening of trees and a reduction in their longevity. It Permanently forested are tops and upper parts of slopes of is important to note that the abandonment of farmland the highest mountain ranges: Łysogórskie, Jeleniowskie, and the onset of natural succession in the last several de- Masłowskie and Klonowskie. Very high stability (f = 5) cades were documented earlier in other temperate forests is also observed in a number of lower mountain ranges: throughout Europe (Piussi 2000, Kozak et al. 2007b, Bose Orłowińskie, Iwaniskie, Zgórskie, Posłowickie, Sierado- et al. 2014). The rate of afforestation in the Holy Cross wickie. As the distance from the stable areas increases, Mountains as well as throughout Europe is much lower forest cover stability lowers. Forests with very low stabil- than the rate of deforestation prior to each region’s turn- ity (f = 1) were documented in the foothills of mountain ing point. As a result, forest cover in Poland and in Europe ranges, in Kielce-Łagów and Wilkowska valleys. Their has not returned to its state from the year 1800. total area is of 269.5 km2, which is 14.8 % of the total This work has attempted to show the significance of Holy Cross Mountains area. morphological and soil-based factors in changes of for- est cover. Both types of factors were used to explain the Discussion and conclusions process of deforestation in the 19th century and afforesta- tion in the 20th century. The economic and political situa- The research presented in this paper indicates that tion in Poland in the period of 1800–1930 brought about changes in the forest cover of the Holy Cross Mountains a significant decline in forest cover that occurred mostly after the year 1800 followed a pattern similar to that in on more fertile soils, not used so far for agricultural pur- other parts of Poland and throughout Europe (i.a. Didier poses, and also on higher altitudes with steep slopes. The 2001, Hörsch 2003, Rudel et al. 2005, Kozak et al. 2007a, period 1930–2011 was characterized by afforestation that Macias and Szymczak 2012). Process of deforestation could be explained by widespread abandonment of over- reached its peak in the Holy Cross Mountains in the 19th used farmland, migration of rural residents to cities, as century and remained active until a turning point in 1930. well as the passage of environmental protection laws. It A similar trend was observed throughout Northern Europe is noticeable that this process of afforestation begun at until the mid-19th century. In Southern Europe, deforesta- first on the areas with worse agricultural conditions than tion continued until the 1970s for a variety of environ- the others. mental, social and economic reasons (Rudel et al. 2005). Areas featuring the largest forest cover stability di- Some of the reasons for deforestation in the Holy Cross rectly correspond to a number of mountain ranges exist- Mountains included a shortage of farmland in the Polish ing in the region. Natural conditions in those areas are the

Figure 7. Map of forest cover stability in the Holy Cross Mountains based on historical maps from 1800, 1900, 1930, 1983, and 2011. Stability: 1 – very low (f = 1), 2 – low (f = 2), 3 – moderate (f = 3), 4 – high (f = 4), 5 – very high (f = 5)

2016, Vol. 22, No. 1 (42) ISSN 2029-9230 7072 BALTIC FORESTRY USE OF GIS-SUPPORTED COMPARATIVE CARTOGRAPHY AND HISTORICAL MAPS /.../ T. CIUPA ET AL. worst for agricultural purposes and because of that they References were not deforested. Those stable areas could also indicate large number of old trees. In the study area they are usu- Bader, M.Y. and Ruijten, J.J.A. 2008. A topography-based model ally protected by the law. This would be the Holy Cross of forest cover at the alpine tree line in the tropical Andes. Journal of Biogeography 35(4): 711–723. National Park (Polish: Świętokrzyski Park Narodowy), Barański, S. 1972. Lasy Gór Świętokrzyskich w Sylwanie z lat five landscape parks and eight special protected areas, 1820–1858 [Forests of the Świętokrzyskie Mts. in “Sylwan” which are part of the pan-European Natura 2000 system copies from years of 1820-1858]. Sylwan 106(3): 55–60 (in of environmental protection (Council Directive… 1992). Polish with Russian and English abstracts). 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Przegląd fito- Region in the 19th and 20th century based on cartographic ma- socjologiczny zbiorowisk leśnych Polski [The syntaxonomical terials]. Sylwan 137(4): 73–82 (in Polish). differentiation of forest communities in Poland]. Phytocoeno- Szymura, T.H., Dunajski, A. and Ruczakowska, A.M. 2010. sis 8 (N.S.) Seminarium Geobotanicum 3: 3–79. Zmiany powierzchni lasów na obszarze Karkonoskiego Parku Musierowicz, A. 1961. Mapa Gleb Polski w skali 1: 300 000 [Polish Narodowego w okresie 1747–1977 [Changes of forest cover Soil Map in the scale 1:300 000]. IUNG Puławy (in Polish). in the Karkonosze National Park area in 1747–1977 period]. Olszewski, J.L. 1992. Indywidualizm klimatyczny Gór Opera Corcontica 47 (suppl. 1): 159–166 (in Polish). Świetokrzyskich [Climatic individualism of the Świętokrzyskie Tomlin, C.D. 1990. Geographic Information Systems and Carto- Mts.]. Rocznik Świętokrzyski 19: 153–165 (in Polish with Eng- graphic Modelling. Prentice-Hall, Englewood Cliffs, New lish abstract). Jersey, 182 pp. Orzechowski, S. 1991. Próba rekonstrukcji stanu zalesienia Trampler, T., Kliczkowska, A., Dmyterko, E. and Sierpińska, A., północno-wschodnich obrzeży Łysogór w okresie wpływów 1990. Regionalizacja przyrodniczo-leśna Polski na podstawa- rzymskich – przyczynek do poznania środowiskowych wa- ch ekologiczno – fizjograficznych [The forest environment runków rozwoju świętokrzyskiego okręgu hutniczego [An regionalisation of Poland on the ecological and physiographi- attempt of recontruction of the state of forestation on the cal grounds]. Państwowe Wydawnictwo Rolnicze i Leśne, north-east margins of the Łysogóry range in the period of Ro- Warszawa, 159 pp. (in Polish). man influence: a contribution to the study on the conditions White, M.S. Jr. and Griffin, P. 1985. Piecewise Linear Rubber- of development of the Świętokrzyski smelting region]. Acta Sheet Map Transformation. The American Cartographer Archaeologica Carphatica 30: 167–186 (in Polish with Eng- 12(2): 123–131. lish abstract). Więcko, E. 1986. Zmiany lesistości i rozmieszczenie lasów w okol- Petit, C.C. and Lambin, E.F. 2002. Impact of data integration icach Warszawy w świetle kartografii i innych źródeł [The for- technique on historical land-use/land-cover change: Compar- est cover and its distribution changes in the Warsaw surround- ing historical maps with remote sensing data in the Belgian ings in the light of cartography and other sources]. Sylwan Ardennes. Landscape Ecology 17(2): 117–132. 130(2/3): 127–136 (in Polish).

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Wijaczka, J., Guldon, Z., Kubicki, Z. and Kazusek, S. 2004, 1960 in relation to soils and other driving forces. Landscape Dzieje regionu świętokrzyskiego od X do końca XVIII wieku Ecology 25(2): 299–313. [History of the Świętokrzyski region since the X century until Wyrobisz, A. 1966. Liczba i rozmieszczenie hut szklanych w the end of the XVIII century]. Wyd. Takt, Kielce, 408 pp. (in Małopolsce w XIV–XVII wieku [The number and location Polish). of glassworks in Malopolska in the XIV–XVII centuries]. Wilson, J.W. 2005. Historical and computational analysis of long- Przegląd Historyczny 57(2): 366–388. term environmental change: forests in the Shenandoah Valley Zevenbergen, L.W. and Thorne, C.R. 1987. Quntititative analy- of Virginia. Historical Geography 33: 33–53. sis of land surface topography. Earth Surface Processes and Wondie, M., Schneider, W., Melesse, A.M. and Teketay, D. 2011. Landforms 12: 47–56. Spatial and Temporal Land Cover Changes in the Simen Mountains National Park, a World Heritage Site in Northwest- ern Ethiopia. Remote Sensing 3: 752–766. Received 15 September 2014 Wulf, M., Sommer, M. and Schmidt, R. 2010. Forest cover chang- Accepted 08 October 2015 es in the Prignitz region (NE Germany) between 1790 and

2016, Vol. 22, No. 1 (42) ISSN 2029-9230 7573 BALTIC FORESTRY CHLOROPHYLL FLUORESCENCE: A NON-DESTRUCTIVE AND RAPID TOOL /.../ L. JIANG ET AL. Chlorophyll Fluorescence: a Non-Destructive and Rapid Tool to Select Chinese Fir Clones Best Adapted to a Particular Region

LI JIANG1, BO JIANG2, ZONGGEN SHEN1, SHENCHAO CHEN1, ZHECHEN QI3, JIADONG CHANG3, NITIN MANTRI4 AND HONGFEI LU1, 3* 1College of Chemistry and Life Science, Zhejiang Normal University, 688 Yingbin Road, Jinhua, 321004, China 2Department of Biological and Food Engineering, Changshu Institute of Technology, 99 Sanhuan Road, Changshu, 215500, China 3College of Life Sciences, Zhejiang Sci-Tech University, 2 Xiasha Road, Hang zhou, 310018, China 4School of Applied Sciences, Health Innovations Research Institute, RMIT University, Melbourne, Victoria, 3000, Australia Corresponding author: Hongfei Lu Tel.: +86-13566997763 E-mail:[email protected] Author: Li Jiang Tel.: +86-18757699705 E-mail: [email protected]

Jiang, L., Jiang, B., Shen, Z., Chen Sh., Qi, Zh., Chang, J., Mantri, N. and Lu, H. 2016. Chlorophyll Fluo- rescence: a Non-Destructive and Rapid Tool to Select Chinese Fir Clones Best Adapted to a Particular Region. Baltic Forestry 22(1): 74-80.

Abstract

Forestry management requires rapid and nondestructive methods to detect the optimal clones or cultivars or species suitable for particular geographical location. We compared the leaf size, plant height, chlorophyll content and chlorophyll fluorescence of four Chinese fir (Cunninghamia lanceolata) clones to understand the differences between their ecophysiological characteristics and pro- vide recommendations for cultivation. The results demonstrate that plant height of clone 13 was significantly higher (P < 0.05) than clone 3. Further, the content of chlorophyll a (Chl a), chlorophyll b (Chl b) and Chl a+ Chl b of clones 39 and 3 were significantly higher (P < 0.05) than the other clones, respectively. Compared to clones 39 and 3, clones 13 and 6 had higher Chl a/Chl b ratio. Furthermore, photochemical energy conversion (Yield) and electron transport rate (ETR) of clones 13 and 6 decreased slowly, and this corresponded well with lower non-photochemical quenching (NPQ) and its coefficient (qN) of clones 13 and 6 with increasing PAR. These results indicate that the clones 13 and 6 are suitable for high light environment but clones 39 and 3 are acclimatized to low light environment. In conclusion, this suggests that a deeper understanding of chlorophyll fluorescence, Chl b and Chl a/Chl b would improve our ability to select appropriate clones or cultivars or species for a particular location.

Key words: Chinese fir; plant height; chlorophyll content; chlorophyll fluorescence; light use efficiency.

Introduction that the main essential oil of Chinese fir has significant antimicrobial activity against Escherichia coli, Staphylo- Chinese fir (Cunninghamia lanceolata), belonging coccus aureus, Bacillus subtilis and Salmonella typhi (Ye to the gymnosperm, is an evergreen conifer with excel- et al. 2005). Although it is regarded as the most important lent timber quality (Farjon and Garcia 2003). It is widely timber tree species, its productivity is largely affected by planted in southern China with a planting history span- poor establishment (Si et al. 2003). Due to rapid growth ning more than 1000 years (Wu et al. 2011). Due to in- of human population, and associated demand for timber, creased demand of its timber for domestic and industrial planting Chinese fir has become a common practice of building and furniture, Chinese fir plantations have been forest management (Zhang 1993). rapidly expanding since the 1980s (Zhang et al. 2004) Different clones or cultivars of the same species pro- with an estimated plantation area in China of 9.11 million duce significantly different yields when cultivated at same hectares (Wu et al. 2011). In addition, it has been reported site. This can be attributed to the influence of climate, soil

2016, Vol. 22, No. 1 (42) ISSN 2029-9230 7476 BALTIC FORESTRY CHLOROPHYLL FLUORESCENCE: A NON-DESTRUCTIVE AND RAPID TOOL /.../ L. JIANG ET AL. nutrients, and water (Novoa and Loomis 1981, Yang et al. analyzed with WinFOLIA (Shen et al. 2007). Plant height 2013). It is relatively easy to control water/nutrient supply was determined using image analysis software (HarFA, through irrigation and fertilization. In contrast, light inten- Harmonic and Fractal Image Analyzer 5.4, freeware at sity (one of the most important plant growth requirements) http://www.fch.vutbr.cz/lectures/imagesci/) as described is more difficult to control (Wang et al. 2007). Under high by Pandolfi et al. (2009). A digital camera (EOS 50D, irradiance, the photosynthetic apparatus absorbs excessive Canon), set at a resolution of 1.5 million dpi, was used to light energy, resulting in the inactivation or impairment acquire images. of the chlorophyll (Chl) containing reaction centers of the chloroplasts (Bertaminia et al. 2006). As a consequence, Chl contents photosynthetic activity is reduced by photoinhibition (Os- Leaves were collected for determination of Chl con- mond 1994). In contrast, under low irradiance, insufficient tent including Chl a and Chl b. Chl pigments were ex- ATP is produced to allow for carbon fixation and carbo- tracted by grinding leaves in 80 % acetone in the dark hydrate biosynthesis. This leads to reduced plant growth. at room temperature. Absorbance of the resulting extracts Therefore, there is a crucial need to identify clones or cul- was measured at three wavelengths: 663.6, 646.6 and 470 tivars that can grow vigorously in native conditions. nm. Chlorophylls levels were expressed as mg/g FM from Leaves with higher Chl b content can absorb more light the equation given by Porra (2009) and Dai (2009). energy in weak light environment (Kramer and Kozlowski 1960). To identify precisely clones or cultivars suitable for Chl Fluorescence Measurements a particular location, it is desirable to conduct photosyn- A MINIPAM (pulse-amplitude modulation) fluorom- thetic capacity under controlled conditions (Medrano et eter (WALZ, Effeltrich, Germany) was used in this study al. 2009). The estimation of Chl b content of leaves using as reported by Zheng et al. (2010) and Jiang et al. (2013). Chl fluorescence technique allows rapid and nondestruc- The photochemical energy conversion in photosystem tive assessment of their suitability in a particular environ- II (Yield), electron transport rate (ETR), photochemical ment. However, there was little information about the Chl quenching (qP), non-photochemical quenching (NPQ) fluorescence of different Chinese fir clones. Therefore, the and its coefficient (qN) of Chl fluorescence were obtained aim of this study was to evaluate the Chl content and Chl over a range of PAR values from 0 to 1,200 µmol m-2 s-1. fluorescence of four Chinese fir clones to help estimation The leaves were dark-adapted for nearly 30 minutes prior of their suitability for planting under the same conditions. to measurements.

Materials and methods Data analysis Each experiment was repeated five times. Data was Plants and growth conditions expressed as mean ± SE (standard error). Statistical sig- Four disease-free clones of Chinese fir with a height nificance between mean values was assessed by Duncan’s of 11 cm were collected from Kaihua Forest Farm. Every multiple range tests (P ≤ 0.05 was considered as signifi- clone was five strains, respectively. The cutting seedlings cant). Data were analyzed by SPSS version 20.0 for Win- of Cunninghamia lanceolata (clone 39, clone 3, and clone dows (SPSS Inc., Chicago, IL). 13) and C. lanceolata cv. Glauca (clone 6) were planted in the Zhejiang Normal University botanical garden in Results September 2012. Plants were cultivated on a hillside in a mixture of peat, sand, and humic soil (1:2:1). Plants Leaf analysis and plant height comparison were grown in orthogonal design under the same light The leaf parameters and plant height of the four Chi- environment (800-2500 umol m-2 s-1 in the daytime). Lo- nese fir clones are showed in Figure 1 after six months of cal production practices such as fertilization regime was growth. Leaf length was not significantly different in the followed. The growth of plants was evaluated after six four clones. Clone 13 had significantly wider leaves (P < months of planting (March 2013). The tender leaves that 0.05) than clone 3, but leaves of clone 6 and 39 were not were just matured of the lateral branch were collected for significantly (P > 0.05) different. Further, the leaf area of analyses of leaf length, leaf width, leaf area, chlorophyll clone 6 and 13 were significantly larger than that of the (Chl) content and Chl fluorescence. other two clones, respectively. There was no significant difference between the leaf area of clone 6 and 13. The Leaf analysis and plant height plant height of clones 6 and 13 were not significantly dif- The growth characteristics of the plants including ferent (P > 0.05), although the plant height of clone 13 leaf parameters and plant height were evaluated after the was the highest of all four clones. Interestingly, the plant cut seedlings were planted for six months. Leaves were height of clones 13 and 6 were significantly taller (P < scanned with a Xatbed graphics scanner and the images 0.05) than clone 3.

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Chl fluorescence The changes of effective quantum yield of Yield were determined. Though the Yield of the four clones de- creased with increasing PAR, the Yield of clone 13 and 6 decreased slower than the other clones (Figure 3a). Clone 3 had the highest Yield when the PAR was between 0 and 225 µmol m-2 s-1. However, the Yield of clone 3 was lower than the other three clones between 300 and 1,200 µmol m-2 s-1. The Yield of clone 13 was the highest between 300 and 1,200 µmol m-2 s-1, followed by clone 6. ETR increased rapidly as PAR increased, and the ETR of clones 13 and 6 increased faster than the other two clones (Figure 3b). The ETR value of clone 3 was at its highest when the value of PAR was between 0 and 300 µmol m-2 s-1, and the ETR of clone 13 was the highest at PAR between 300 and 1200 µmol m-2 s-1. The ETR of clone 6 was lower than this of clone 39 at PAR between 0 -2 -1 Figure 1. Leaf length, leaf area, leaf width and plant height of and 300 µmol m s but it was higher than this of clone 39 -2 -1 the four Chinese fir clones at the age of six months. Values are at PAR between 300 and 1200 µmol m s . means ± SE The qP in clone 13 was the highest when its PAR was between 600 and 1200 µmol m-2 s-1, while values of clone Chl contents 3 were the lowest when its PAR was between 225 and The Chl content of the leaves of the four clones was 1200 µmol m-2 s-1 (Figure 3c). NPQ and qN also changed in analyzed (Figure 2). Clones 39 and 3 had significantly response to light irradiance at different levels. NPQ (Figure higher Chl a, Chl b, Chl a + b content (P < 0.05) than the 3d) and qN (Figure 3e) increased positively with increas- other two clones, respectively (Figure 2). The Chl a, Chl ing PAR. There is no significance of NPQ of four clones b, Chl a + b content of clone13 was lower than the other between 0 and 150 µmol m-2 s-1. The comparison of NPQ three clones, but it had higher Chl a / Chl b ratio value showed a trend (39-clone > 3-clone> 13-clone > 6-clone) than the other three clones (Figure 2). The lowest Chl a, between 225 and 1,200 µmol m-2 s-1. The qN of clone 39 Chl b and total Chl content and the highest Chl a / Chl b was higher than of other three clones at PAR between 150 ratio were observed in clone 13. and 1,200 µmol m-2 s-1. Further, these values were higher in clone 3 than in other two clones (clone 13 and 6) be- tween 225 and 600 µmol m-2 s-1.

Correlation of plant heightwith Chl content and Chl fluorescence The Pearson correlations of plant height with Chl content and Chl fluorescence parameters during the light intensity of 800 µmol m-2 s-1 are shown in Table 1. Inter- estingly, we found that the correlation of Chl a with Chl b was much high (P < 0.01). Chl fluorescence parameters (Yield and ETR) were negatively correlated with Chl b (P < 0.01), but being positively correlated with Chl a/Chl b ratio and plant height, respectively (P < 0.05) (Table 1). In addition, there was good correlation among Yield, ETR, Chl b, Chl a/Chl b ratio, plant height for the four Chinese fir clones, respectively. Clones 39 and 3 had sig- nificantly higher Chl b content (P < 0.05) than the other two clones, respectively. So the different photosynthe- Figure 2. Comparison of chlorophyll (Chl) content in leaves of sis physiological index of the four clones may change at the four Chinese fir clones . Values are means ± SE same irradiance.

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a d

b e

Figure 3. Changes in photosynthesis efficiency of the four Chinese fir clones at different Photosynthetically Active Ra- diations (PAR). (a) Changes in photochemical energy conver- sion (Yield) and irradiance (PAR) response curves of the four Chinese fir clones. (b) Apparent electron transport rate (ETR) and irradiance (PAR) response curves of the four Chinese fir clones. (c) Photochemical quenching (qP) and irradiance (PAR) responsecurves of the four Chinese fir clones. (d) Changes in non-photochemical quenching (NPQ) and irradiance (PAR) response curves of the four Chinese fir clones. (e) Changes in the coefficient of non-photochemical quenching (qN) and ir- c radiance (PAR) response curves of the four Chinese fir clones. Values are means ± SE

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Table 1.The Pearson correlations between pigment content (Chl a, Chl b and Chl a+Chl b), pigment parameters (Chl a/Chl b ratio) and chlorophyll fluorescence parameters (Yield, ETR, qp, qN and NPQ) at 800 µmol m-2 s-1

ETR qN Chl a Chl b Chl a+Chl b Chl a/Chl b Chl b 0.848**

Chla+Chl b 0.967** 0.914**

Chl a/Chlb -0.166 -0.635** -0.333

Yield -0.667** -0.869** -0.750** 0.605*

ETR -0.666** -0.869** -0.749** 0.606* 1.000** qp -0.211 -0.197 -0.206 -0.048 0.382 0.382 qN 0.336 0.331 0.321 -0.214 -0.237 -0.235 0.661**

NPQ 0.549* 0.476 0.495 -0.129 -0.509* -0.507* 0.120 0.784**

**P<0.01; *P<0.05

Discussion and conclusions significant decline of Yield that is a measure of the total photochemical efficiency of PSII under photosynthetic Light saturation rate of photosynthesis depends on steady-state conditions (Zlatev 2009). In this experiment, leaf traits such as effective leaf size (Koike 1988). Leaf the differences in the values of Yield indicate that the four area of clones 6 and 13 was the largest (Figure 1) and it clones had significant differences in the electron transport increased the photosynthetic capacity of their leaves. The activity of PSII when plants are grown under same condi- Chinese fir is used for its wood. Therefore, it is critical tions. Under stronger illumination, the quantum yield of to ensure that the plants maintain high growth rate. Our PSII was high in clones 13 and 6 and low in the clones results indicated that at the age of six months, the height 39 and 3. of clones 13 and 6 were higher than of the other clones The ETR value represents the relative quantity of (Figure 1), which was in accordance with their large leaf electrons passing through PSII during steady-state photo- size, Yield and ETR. synthesis (Tezara et al. 2003). Thus, ETR value reduction Chl content is closely associated with photosynthetic means loss of capture efficiency/excitation of Chl. The rate of plants in the field (Sang et al., 2011; Wang and ETR values of clones 39 and 3 reduced significantly be- Yuan, 2001). Chl a/ Chl b ratio is more directly involved tween 600 µmol m-2 s-1 and 1200 µmol m-2 s-1. Reductions in determining photosynthetic activity (Givnish 1988). in ETR may be due to the inefficiency of capturing ex- Further, Chl b is synthesized from Chl a by chlorophyl- citation (Flowers et al. 2007). Photochemical quenching lide a oxygenase and the conversion of Chl a to Chl b is (qP) depends on the proportion of reaction centers, which photochemical rather than biochemical process (Tanaka are photochemically “open”, rather than on the efficiency and Tanaka 2005). The results demonstrate that the con- with which an absorbed photon can reach a reaction cen- tent of Chl b in clones 39 and 3 were significantly higher tre (Maxwell and Johnson 2000). High qP is advantageous (P < 0.05) than in the other two clones. However, the Chl for the separation of electric charge in the reaction center, a/Chl b ratio of clones 39 and 3 was lower than this of the and is beneficial to electron transport and PSII yield (Guo other two clones. Chl b can increase the relative content of et al. 2006, Mao et al. 2007). Non-photochemical quench- concentrated pigment protein to absorb and make use of ing (NPQ) and its coefficient (qN) can represent the en- more scattered light and transmitted light so that leaves in ergy, which cannot be utilized to transport photosynthetic the weak light environment can absorb more light energy electrons being dissipated harmlessly as heat energy from for photosynthesis (Kramer and Kozlowski 1960). This PSII antennae (Muller et al. 2001; Vasil’ev et al. 1998, suggests that clones 39 and 3 are more suitable for grow- Veres et al. 2006). The lower NPQ of clones 13 and 6 in- ing under low light intensity than the other two clones. dicates that these plants effectively reduced the irradiance Light energy absorbed by Chl is transformed into Chl heat and efficiently utilized the energy absorbed by an- fluorescence (Maxwell and Johnson 2000). Chl fluores- tenna pigments in PSII. The higher NPQ of clones 39 and cence gives a valuable insight into the exploitation of ex- 3 suggested that the energy absorbed in the physiological citation energy by PSII and indirectly by the other protein range of irradiances was much higher than photochemi- complexes of the thylakoid membranes (Roháček 2002). cal utilization, which caused inhibition of photosynthesis The occurrence of photoinhibition was highlighted by the (Vasil’ev et al. 1998).

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Yield and ETR were negatively correlated with Chl References b, but being positively correlated with Chl a/Chl b ratio and plant height. Chl a/Chl b ratio is directly involved Aro, E. M., Virgin, I. and Andersson, B. 1993. Photoinhibition of in determining photosynthesis (Givnish 1988). Thereby photosystem. Inactivation, protein damage and turnover. Bio- chimica Biophysica Acta 1143: 113-134. Chl fluorescence gives a valuable insight into the exploi- Bertaminia, M., Muthuchelianb, K., Rubinigga, M., Zorera, tation of excitation energy by PSII and indirectly by the R., Velascoa, R. and Nedunchezhiana, N. 2006. Low-night other protein complexes of the thylakoid membrane. Chl temperature increased the photoinhibition of photosynthesis in fluorescence supports a possible non-destructive method grapevine (Vitis vinifera L. cv. Riesling) leaves. Environmen- tal and Experimental Botany 57: 25-31. to evaluate the chemical changes and provide a valuable Dai, Y. J., Shen, Z. G., Liu, Y., Wang, L. L., Hannaway, D. and insight into the exploitation of excitation energy by PSII Lu, H. F. 2009. Effects of shade treatments on the photosyn- (Roháček 2002). The Yield, ETR and qP values, and the thetic capacity, chlorophyll fluorescence, and chlorophyll con- NPQ value combined with leaf morphology (leaf size) tent of Tetrastigma hemsleyanum Diels et Gilg. Environmental and Experimental Botany 65 (2-3): 177-182. and plant height, and the ratio of Chl a/Chl b ratio of the Farjon, A. and Garcia, S. O. 2003. Cone and ovule development clones grown under the same condition in this experiment in Cunninghamia and Taiwania (Cupressaceae sensu lato) and suggested that clones 39 and 3 are suitable for low light its significance for conifer evolution. American Journal of conditions but the clones 13 and 6 are adapted to grow Botany 90 (1): 8-16. Flowers, M. D., Fiscus, E. L., Burkey, K. O., Booker, F. L. and under high light conditions. 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McGraw-Hill Book Company, New York, ther, clones 39 and 3 were more adapted for low light con- pp: 642. ditions and high light greatly reduced their photosynthesis Krause, G. H. 1988. Photoinhibition of photosynthesis. An evalu- ability and productivity. Chl fluorescence can be used as ation of damaging and protective mechanisms. Physiologia a measure of photosynthesis and status of photosynthetic Plantarum 74: 566-574. Mao, L. Z., Lu, H. F., Wang, Q. and Cai, M. M. 2007. Compara- apparatus thereby providing a quantitative index to select tive photosynthesis characteristics of Calycanthus chinensis appropriate varieties for a particular location. Therefore, and Chimonanthus praecox. Photosynthetica 45: 601-605. this technique is important for selecting appropriate cul- Maxwell, K. and Johnson, G. N. 2000. Chlorophyll fluorescence tivars for forest management due to its sensitivity, conve- – a practical guide. Journal of Experimental Botany 51 (345): 659-668. nience, and non-destructive characteristics. Medrano, H., Flexas, J. and Galmes, J. 2009. Variability in water use efficiency at the leaf level among Mediterranean plants Acknowledgements with different growth forms. Plant and Soil 317 (1-2): 17-29. Müller, P., Li, X. P. and Niyogi, K. K. 2001. Non-photochemical quenching. A response to excess light energy. Plant Physiol- This work was supported by Zhejiang Provincial ogy 125 (4): 1558-1566. Top Key Discipline of Biology and Zhejiang Provincial Novoa, R., and Loomis, R.S. 1981. Nitrogen and plant production. Universities Key Discipline of Botany. The authors also Plant Soil 58:177-204. acknowledge the workers from Kaihua Forest Farm for Osmond C. B. 1994. What is photoinhibition? Some insights from comparisons of shade and sun plants. In: Baker NR., Bowyer helping in cultivation of plants. JR. (Eds.), Photoinhibition of Photosynthesis, from the Mo- lecular Mechanisms to the Field. 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2016, Vol. 22, No. 1 (42) ISSN 2029-9230 8082 BALTIC FORESTRY RELATIONS BETWEEN SITE CHARACTERISTICS AND SPRUCE STAND PRODUCTIVITY J. LASOTA ET AL. Relations between Site Characteristics and Spruce Stand Productivity

JAROSŁAW LASOTA, EWA BŁOŃSKA* AND MACIEJ ZWYDAK Department of Forest Soil, Faculty of Forestry, University of Agriculture in Krakow, Al. 29 Listopada 46, 31-425 Kraków *Corresponding author [email protected]

Lasota, J., Błońska*, E. and Zwydak, M. 2016. Relations between Site Characteristics and Spruce Stand Productivity. Baltic Forestry 22(1): 81-89.

Abstract

The aim of this study was to estimate the effect of topographic factors and soil properties on the productivity of Norway spruce stands in the Sudety Mountains, Poland. pH, organic C and N contents, hydrolytic and exchangeable acidity, cation contents (Ca2+, Mg2+, K+, and Na+), and soil texture were determined. We present soil properties from five parent material types and include separate analyses for the organic and humus-mineral soil horizons. Edaphic factors, together with topography, were significantly related to the Norway spruce site index. Soil properties from the humus-mineral horizon or the organic horizon (with features of topographic position included in the models) accounted for 67 % and 56 % of the site index variability, respectively. Elevation, the Al3+/effec- tive cation exchange capacity ratio, and C and K+ contents were significant individual predictors of site index. A regression analysis indicated that elevation explains 49 % of the site index variability.

Key words: mountains forest sites; soil properties; site index.

Introduction and N, and CaCO3 contents, and soil moisture conditions explained site index variability. Starr et al. (2005) estimat- Site productivity is a quantitative estimate of the po- ed impact site, stand and climate factors on above-ground tential to produce plant biomass, and it may be assessed in litterfall production. Site productivity in mountainous several ways, usually using either geocentric or phytocen- areas is highly dependent on climatic conditions, and it tric methods (Skovsgaard and Vanclay 2008). Phytocen- is affected by soil fertility and geological substrates. Ac- tric methods are based on site index determination from cording to J. Socha (2008), the Polish West Carpathian the height and age of a tree stand. Geocentric productivity Mountains site index is a function of elevation, aspect, indicators are based on site properties, including climate, slope, the size of the mountain massif, and the soil par- topography, or soil characteristics (Hägglund and Lund- ent rock. Previous studies used a limited number of soil mark 1977). Topographic factors are used in combination characteristics and geological substrates to analyze spruce with edaphic factors. Soil texture and nutrients levels are stand productivity (Socha 2008, Bošela et al. 2013). Here, commonly used to estimate site index (Pacheco 1991). we present soil properties from five parent material types, Many studies have examined the relationships be- and include separate analyses of the organic and humus- tween site characteristics and productivity (Libiete 2008, mineral soil horizons. To our knowledge, information on Socha 2008, Afif-Khouri et al. 2011, Farrelly et al. 2011, the relationships between site index and multiple soil prop- Bösela et al. 2013). Kariükštis and Juodvalkis (2005), erties from multiple geological substrates is very limited. Kuliešis et al. (2010) studied forest site productivity. Ear- In Poland, the Sudety Mountains are more geologi- ly studies presented single-variable relationships between cally variable than the Carpathian Mountains. There are soil or climate variables and site index. Recent studies magmatic, sedimentary, and metamorphic rocks of dif- have generally employed multiple regression techniques ferent geological ages. In addition, in the past, this area that present the ratios of environmental variables to site was subject to a strong anthropogenic impact, and it is index (Socha 2012). Previous research examined the re- dominated by spruce monocultures. Norway spruce (Pi- lationships between site productivity and topography, cea abies (L.) Karst.) is the most economically important climate, and soil properties in lowland and mountainous forest species. In recent years, Europe has had to deal with areas. Sewerniak and Piernik (2012) estimated the impact spruce dieback that was caused by complex biotic and abi- of soil properties on the site index class of Scots pine on otic factors that represent a specific chain-escalating dis- + lowland sites, and found that pHKCl, the fine fraction, K , ease process (Małek and Barszcz 2008, Zwoliński 2013).

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One of the reasons for the spruce dieback is a change in a.s.l. Experimental, circular in shape plots of 0.25 ha were soil chemistry. Acidification is one of the main processes established. At each experimental plot, a detailed descrip- that can affect soil productivity (Małek 2010). Periodical- tion of the soil profile was performed, and samples were ly, extreme conditions or stress factors may appear which taken from each genetic horizon to perform a basic analy- could initiate the weakening of stands (water deficit or sis of the soil properties to determine the soil subtypes. mass gradations of insects). Now dying spruce cover ar- Samples from the organic horizon (average depth 0–10 eas located on both sides of the southern Polish border cm) and the humus-mineral horizon (average depth 10–25 (Małek et al. 2014). Understanding the relationships be- cm) were taken to determine soil chemical parameters tween productivity and site factors will help predict risks (Table 2). Prior to the analysis, soil samples were air-dried and possibly prevent spruce dieback. for about 1 week at room temperature, and sieved through The aim of this study was to estimate the relation- a 2-mm sieve. ships between topographic factors, soil properties, and The diameter at breast height and tree height of all the productivity of Norway spruce stands. Our study trees were measured in the experimental plots. Tree age evaluated which soil properties have the greatest impact was determined by a Pressler drill. Top height was esti- on spruce productivity. We hypothesized that (1) edaphic mated as the mean height of 100 largest diameter trees per factors, together with topography, explain Norway spruce ha. In particular, the number of trees of the sample plot cor- site index variability in the Sudety Mountains, and that (2) responding proportionally to the plot area was used, e.g. 25 the productivity of spruce stands depends on soil proper- largest trees in the 0.25-ha plot. The locations of the sample ties associated with the nutrient cycle and acidity. plots were determined based on topography. The topogra- phy was described by elevation, exposition, and slope. Materials and Methods The values of site index for the particular sample plots were determined using the model of the site index The study was conducted in the Sudety Mountains system for Norway spruce stands in Poland (Socha 2011) in Poland. It included the Izerskie, Kaczawskie, Stołowe, (eqs. 1 and 2): and Złote Mountains, and the Ślęża and Śnieżnik Mas- sif (Figure 1). In these research areas, Gleysol, Cambisol, [1] Podzol, Stagnosol, and Regosol soils prevail (WRB 2006). Soils were created on a variety of geological substrates (granite, greenstone, sandstone, gabbro, and crystal rock) (Table 1). The study areas were covered by spruce stands without any symptoms of weakening. [2] In July 2012, field data were collected from 39 sam- ple plots located in spruce stands aged 60–160 years. The where studied stands were located between 440 and 1,180 m SI is the site index; H is the top height of the stand (mean height of 100 thickest trees per hectare); and T is the stand age.

Statistical data analysis was performed using ad- vanced analytics software package Statistica 10. In order to reduce the number of variables in statistical data set and visualize multivariate data set as a set of coordinates in a high-dimensional data space the PCA method was used. The PCA method was also used in order to interpret factors depending on the kind of data set. The multiple forward stepwise regression method was used to develop models describing the relationship between estimated val- ues of site index to soil characteristics and topography.

Results

The organic horizon of the soils that developed on

greenstone had the highest pH (average pH in H2O of 4.2), the highest exchangeable Ca2+, K+, Mg2+, and Na+ contents, the highest C content (average 30.77 %), and Figure 1. Location of the research area a high N content (average 1.53 %) (Table 3). The lowest

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Table 1. Characteristics of research area

Elevation, Geological Plot Mountains region Exposition Slope Soil type a.s.l. substrates 1 Izerskie Mountains 622 NW 9 GR Humic Gleysol 2 Izerskie Mountains 756 E 5 GR Dystric Cambisol 3 Izerskie Mountains 795 E 15 GR Haplic Podzol 4 Izerskie Mountains 798 S 10 GR Dystric Cambisol 5 Izerskie Mountains 767 S 15 GR Albic Cambisol 6 Izerskie Mountains 640 W 5 GR Albic Cambisol 7 Izerskie Mountains 870 - 2 GR Haplic Podzol 8 Izerskie Mountains 846 NW 5 GR Gleysol 9 Izerskie Mountains 803 N 5 GR Hyperdystric Cambisol 10 Izerskie Mountains 624 NE 12 GR Haplic Podzol 11 Izerskie Mountains 857 E 7 GR Histic Stagnosol 12 Izerskie Mountains 1139 E 2 GR Regosol 13 Izerskie Mountains 1041 N 15 GR Haplic Podzol 14 Izerskie Mountains 980 SE 6 GR Haplic Podzol 15 Kaczawskie Mountains 512 SW 25 GS Hyperdystric Cambisol 16 Kaczawskie Mountains 537 N 25 GS Epidystric Cambisol 17 Kaczawskie Mountains 650 SW 20 GS Hyperdystric Cambisol 18 Kaczawskie Mountains 640 SW 15 GS Hyperdystric Cambisol 19 Kaczawskie Mountains 523 S 25 GS Hyperdystric Cambisol 20 Kaczawskie Mountains 690 NE 18 GS Hyperdystric Cambisol 21 Kaczawskie Mountains 440 W 10 SS Hyperdystric Cambisol 22 Kaczawskie Mountains 620 NWW 31 SS Haplic Podzol 23 Kaczawskie Mountains 630 NW 14 SS Haplic Podzol 24 Kaczawskie Mountains 630 W 18 SS Haplic Podzol 25 Stołowe Mountains 605 N 18 SS Hyperdystric Cambisol 26 Stołowe Mountains 670 W 15 SS Stagnosol 27 Stołowe Mountains 673 N 30 SS Haplic Podzol 28 Stołowe Mountains 775 SW 25 SS Hyperdystric Cambisol 29 Stołowe Mountains 708 SE 10 SS Eutric Cambisol 30 Stołowe Mountains 717 N 8 SS Hyperdystric Cambisol 31 Stołowe Mountains 670 W 30 SS Haplic Podzol 32 Ślęża Massif 570 SE 25 GB Hyperdystric Cambisol 33 Kaczawskie Mountains 547 SW 36 GB Hyperdystric Cambisol 34 Śnieżnik Massif 785 SE 20 CR Albic Cambisol 35 Śnieżnik Massif 1020 W 15 CR Albic Cambisol 36 Śnieżnik Massif 1180 NE 7 CR Stagnosol 37 Złote Mountains 1024 N 18 CR Albic Cambisol 38 Złote Mountains 1080 N 10 CR Haplic Podzol 39 Złote Mountains 1040 S 25 CR Haplic Podzol Geological substrates: GR – Granite, GS – Greenstone, SS – Sandstone, GB – Gabbro, CR – Crystal rock

Table 2. The sample parameters and methods of analysis

Analyzed parameters Methods determined potentiometrically, in H O and 1M KCl dm-3 solutions, with soil-to-solvent soil pH 2 proportion of 1:2.5 for mineral soils and 1:5 for organic soils

total C (CT) and total N (NT) CNS 2000 Leco elemental analyzer with the calculation of the C:N ratio (in two horizons) hydrolytic acidity (total acidity – Hh) the Kappen method in the extract of 1M of calcium acetate Exchangeable acidity (Hw), exchangeable

aluminium (HAl), exchangeable hydrogen the Sokolov method

(HH)

2+ 2+ calcium (Ca ), magnesium (Mg ), potassium in a 1M CH3COONH4 extract of pH 7.0 as determined with a Thermo Scientific iCAP (K+) and sodium (Na+) (base exchange 6000 ICP OES Spectrometer, with calculation of effective cation exchange capacity

capacity, S) (CECE) and total cation exchange capacity (CECT) available phosphorus Bray & Kurtz method Particle size Laser defraction method

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+ pH (average pH in H2O of 3.6) was noted in the organic the Na content, and exchangeable acidity negatively cor- horizon of soils that developed on granite and crystal rock. related with the spruce site index (Figure 2). These soils had low exchangeable cation contents (Table Performing a multiple regression analysis allowed 3). The mineral horizon of soils on greenstone and gabbro us to formulate an equation explaining the site index us- substrates had the highest dust and clay contents (Table 4). ing selected topographic parameters and the properties of The highest pH was noted in the mineral horizon of soils soils in the organic horizon. The results of the multiple on greenstone and gabbro substrates (average pH in H2O regression analysis showed that the site index of spruce of 4.1 and 4.4, respectively). The lowest pH in the mineral stands was significantly affected by elevation and C and horizon was reported for soils on granite (average pH in K+ contents in the organic horizon. The model describing

H2O of 3.9). The soils on greenstone and gabbro substrates the site index of spruce stands expressed as a function of exhibited better organic matter decomposition (average the above variables explained over 56% of the variance 2 C/N ratios of 20.2 and 17.0, respectively) (Table 4). (R adj = 0.56, equation 3). The highest average site index of spruce stands was noted in soils that developed on greenstone and gabbro SI = 54.3 − (0.02×Elevation) − (5.2×log[C]) + substrates, and the lowest one was reported for soils on + (1.89×log[K+]) [3] granite and crystal rocks (Table 5). The highest variability of the spruce site index was noted for soils on granite sub- Figure 3 presents the projection of topographic fac- strates, while soils on gabbro had the lowest one (Table 5). tors and properties of soil in the humus-mineral horizon on A positive correlation between site index and pH in the factor-plane 1×2. Strong relationships between spruce

H2O in the organic horizon and effective base saturation site index and exchangeable cation contents and base satu-

(VE), as well as exchangeable cation contents, particularly ration in the humus-mineral horizon were noted. Addition- Ca2+ and Mg2+, was observed. Elevation, C and N contents ally, the clay content correlated with spruce site index. The in the organic horizon, the total cation exchange capacity spruce site index deteriorated with increasing sand content

(CECT), the effective cation exchange capacity (CECE), in the humus-mineral horizon, increasing C/N ratio, and

Table 3. Chemical soil properties in the organic humus horizon (Ofh) used to develop the discriminant rule to estimate the site index in Picea abies on the different geological substrates

Variable GR GS SS GB CR C 28.00±11.18 30.77±5.78 25.61±9.97 30.26±1.68 31.20±11.76 N 1.31±0.54 1.53±0.24 1.24±0.43 1.35±0.17 1.59±0.53 C/N 21.6±1.9 20.1±1.9 20.4±2.1 22.5±1.6 19.3±1.3 S 2.49±1.72 12.97±9.76 4.13±2.14 10.47±1.95 5.46±3.28

CECT 82.1±33.0 82.5±12.2 67.3±33.6 77.2±10.2 95.4±55.2 V 3.4±2.8 16.1±12.8 7.5±5.4 13.5±0.7 9.0±10.5 pH H2O 3.6±0.3 4.2±0.5 3.7±0.2 4.0±0.3 3.6±0.3 pH KCl 3.0±0.2 3.4±0.5 2.9±0.2 3.2±0.2 2.7±0.3 Ca 19.8±16.2 190.2±152.4 55.8±40.1 174.3±28.2 71.6±54.6 K 28.3±23.5 47.9±32.5 23.9±7.7 23.0±0.6 30.2±10.9 Mg 7.5±4.4 25.9±17.4 7.9±3.0 13.4±6.5 12.5±5.7 Na 3.7±1.7 2.9±0.9 2.0±0.7 2.1±0.5 1.9±0.7

Ca/CECT 0.014±0.013 0.118±0.100 0.052±0.051 0.112±0.003 0.060±0.074

K/CECT 0.009±0.008 0.015±0.011 0.010±0.005 0.008±0.001 0.013±0.015

Mg/CECT 0.008±0.006 0.026±0.019 0.011±0.004 0.014±0.005 0.016±0.016 Hw 22.3±4.5 12.6±7.3 15.2±3.7 10.5±0.9 19.6±9.2

CECE 24.8±4.5 25.5±4.1 19.3±4.5 21.0±2.9 25.0±9.6 Al 19.5±4.9 9.5±6.9 12.7±2.9 8.6±0.6 17.5±9.0

Al/CECE 0.788±0.145 0.395±0.283 0.664±0.088 0.409±0.029 0.681±0.176 P 36.9±16.8 65.8±24.6 23.3±11.1 35.2±25.2 22.7±15.5 Geological substrates: GR- Granite, GS – Greenstone, SS – Sandstone, GB – Gabbro, CR – Crystal rock; C – total organic carbon . -1 (%), N – total nitrogen (%), C/N – C/N ratio, S – sum of exchangeable base cations (cmol(+) kg ), CECT – total cation exchangeable capacity (cmol(+).kg-1), V – saturation of base cations (%), Ca, K, Mg, Na – exchangeable Ca, K, Mg, Na (mg.100g-1), . -1 . -1 Hw – exchangeable acidity (by the Sokolov method) (cmol(+) kg ), CECE – effective cation exchangeable capacity (cmol(+) kg ), Al – exchangeable aluminium (mg.100g-1), P – available phosphorus (by the Bray & Kurtz II method) (mg.kg-1)

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Table 4. Chemical and physical soil properties in the mineral-humus horizon (A-AE) used to develop the discriminant rule to esti- mate the site index in Picea abies on the different geological substrates

Variable GR GS SS GB CR Sand 52.3±12.8 36.7±7.5 61.1±21.4 36.6±3.6 64.0±12.7 Dust 39.5±11.0 54.0±8.2 30.4±16.5 55.0±1.4 30.0±10.7 Clay 8.2±3.0 9.3±2.1 8.5±6.8 8.5±2.1 6.0±3.1 C 4.63±2.49 4.11±2.38 1.33±0.46 2.45±1.95 5.01±2.92 N 0.19±0.11 0.21±0.13 0.07±0.03 0.13±0.10 0.20±0.13 C/N 24.5±3.4 20.2±4.4 23.0±9.6 17.8±1.9 28.9±7.3 S 0.36±0.20 0.70±0.45 0.43±0.58 0.58±0.34 0.38±0.16

CECT 21.5±8.2 19.6±9.2 10.6±5.3 11.5±7.4 23.8±14.6 V 1.7±0.9 4.6±3.9 5.3±8.5 5.2±0.4 2.0±1.1

pH H2O 3.9±0.2 4.1±0.2 3.9±0.2 4.4±0.2 4.0±0.3 pH KCl 3.2±0.2 3.2±0.1 3.1±0.2 3.6±0.0 3.4±0.4 Ca 2.5±2.5 7.5±5.8 5.4±9.1 8.1±6.4 2.8±1.6 K 3.9±1.8 2.7±2.4 2.6±1.8 2.7±1.6 4.3±2.0 Mg 1.1±0.7 2.6±1.4 0.9±1.1 1.0±0.6 1.2±0.6 Na 1.0±0.4 1.0±0.3 0.4±0.3 0.7±0.2 0.7±0.2

Ca/CECT 0.006±0.007 0.021±0.011 0.035±0.072 0.033±0.006 0.007±0.003

K/CECT 0.005±0.001 0.004±0.003 0.008±0.007 0.009±0.009 0.006±0.006

Mg/CECT 0.004±0.002 0.018±0.023 0.008±0.008 0.007±0.000 0.005±0.003 Hw 12.1±4.3 14.0±2.2 7.4±5.2 9.3±1.5 9.5±3.9

CECE 12.5±4.4 14.7±2.2 7.8±5.6 9.8±1.9 9.9±4.0 Al 11.4±4.1 13.5±2.1 7.1±5.2 8.9±1.3 9.3±3.8

Al/CECE 0.914±0.031 0.921±0.046 0.877±0.083 0.908±0.042 0.939±0.010 P 11.3±9.9 5.2±2.7 1.4±0.5 3.5±0.5 4.8±4.1 Geological substrates: GR – Granite, GS – Greenstone, SS – Sandstone, GB – Gabbro, CR – Crystal rock; Sand, dust, clay (%), . -1 C – total organic carbon (%), N – total nitrogen (%), C/N – C/N ratio, S – sum of exchangeable base cations (cmol(+) kg ), CECT – total cation exchangeable capacity (cmol(+).kg-1), V – saturation of base cations (%), Ca, K, Mg, Na – exchangeable Ca, K, Mg, . -1 . -1 Na (mg 100g ), Hw – exchangeable acidity (by the Sokolov method) (cmol(+) kg ), CECE – effective cation exchangeable capacity (cmol(+).kg-1), Al – exchangeable aluminium (mg.100g-1), P – available phosphorus (by the Bray & Kurtz II method) (mg.kg-1)

Table 5. Site index (SI) of spruce and elevation on the different geological substrates

Parameters GR GS SS GB CR

Site index (SI) Average 26.1 32.1 31.2 32.1 26.1 Maximum 32.6 35.9 36.2 32.5 32.4 Minimum 8.1 26.9 23.6 31.8 18.5 SD 6.2 3.4 4.2 0.5 5.0 Altitude Average 824 592 649 559 1022 Maximum 1139 690 775 570 1180 Minimum 622 512 440 547 785

Geological substrates: GR – Granite, GS – Greenstone, SS – Sandstone, GB – Gabbro, CR – Crystal rock increasing soil acidity, expressed as the ratio of exchange- the analysis showed that the site index of spruce stands 3+ able hydrogen to CECE (H/CECE) (Figure 3). was significantly affected by elevation, the log of the Al / + Additionally, the multiple regression analysis al- CECE ratio, and the K content in the humus-mineral hori- lowed us to formulate an equation explaining the site in- zon. The model describing the site index of spruce stands dex using selected topographical parameters and proper- expressed as a function of the above variables explained 2 ties of soils in the humus-mineral horizon. The results of over 67 % of the variance (R adj = 0.67, equation 4).

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3+ SI = 47.6 − (0.024×Elevation) − (28.29×log[Al /CECE]) + content, sorption capacity, basic exchangeable cation con- + (1.78×log[K]) [4] tents, and decreasing sand content and acidity. The role of such geological substrates in creating soil is associated Growth of spruce stands and their site index depends with the height of the mountain range. The highest eleva- on the characteristics of the geological substrate. Less tions of the Sudety Mountains developed from granite and favourable conditions for spruce growth were found for poorer metamorphic rocks – crystal rock. Forest stands in soils that developed on granite and crystal rock. Higher regions with these rocks have the greatest range of site in- spruce stand site indices were found for soils that de- dex values. Greenstone and gabbro developed on the low- veloped on sandstone, and the best ones were found for est ridges, and stands on these rocks have the highest site soils that developed on greenstone and gabbro. Regoliths indices as a result of synergies between soil and climatic in the order of granite rock – crystal rock – sandstone – factors. Figure 5 presents the relationship between spruce greenstone – gabbro are characterized by increasing clay site index and elevation.

Figure 2. Projection of variables on the factor-plane 1×2 Figure 3. Projection of variables on the factor-plane 1×2 (site index and properties of the Ofh horizon) (site index and properties of the humus-mineral horizon)

Figure 4. Factorial plan of variables on the factor-plane 1×2 (geological substrates)

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Figure 5. Relation- ship between site in- dex of spruce stands and elevation

2009). Drawing conclusions on the basis of the properties Discussion and conclusions of surface horizons, where the distorting effect of spruce monocultures is focused, requires extreme caution. Many researchers have formulated growth models of Elevation was one of the site parameters that were mountain spruce stands and searched for site characteris- used to explain the site index of spruce stands in the Su- tics that determine spruce growth. M. Bošela et al. (2013), dety Mountains. The regression analysis indicates that who conducted similar studies in the Western Carpathians, this parameter explains 49 % of the site index variability. concluded that the most important factors influencing the In mountainous areas, elevation is directly related to ther- site index of spruce stands are climatic factors, particu- mal conditions and the length of growing season, and, in larly the length of growing season, and selected soil char- the Sudety Mountains, the geological substrate. Accord- acteristics. The authors analyzed only soil pH and the C/N ing to Socha J. (2008) and Gömöryova E. and Gömöry D. ratio in the first surface horizon to a 10-cm depth, with (1995), topographic factors, especially elevation, can be no division into the organic and humus-mineral horizons. used to explain the variability of the site index of moun- According to the authors, ecological factors explained tain spruce stands. The properties of the surface horizon most (76 %) of the site index variation. J. Socha (2008), of soil in these studies explain approximately 10–20 % in a study conducted in the Western Beskid Mountains, of the site index variation of spruce stands, depending on explained 79 % of the site index variability using site fac- whether the organic horizon or the humus-mineral hori- tors such as geological substrate, elevation, and position zon was considered. relative to the height of the mountain range. In our study, Among the properties of the surface soil horizons, the the soil properties of the humus-mineral or organic ho- regression analysis identified two features in the humus- rizons, together with features of position, accounted for mineral horizon that affect the growth of spruce stands. 3+ 67 % and 56 %, respectively, of the site index variability. The first feature, the Al /CECE ratio, can be treated as Obtaining a more accurate estimation of site index using an indicator of acidity, and it is correlated with the po- the properties of the humus-mineral horizon rather than tential toxicity of Al3+ in the soil (Gruba 2004a). Spruce those of the organic horizon is not surprising. The organic soil tests indicate that a high concentration of Al3+ in the horizon is less processed and it contains more labile C soil contributes to the inhibition of root growth and the fractions that are more diverse. Its physical and chemical inhibition of P and Ca2+ uptake and, consequently, leads properties are less stable, and are subject to strong fluc- to disorders in metabolic processes and growth inhibi- tuations (depending on thermal conditions, the structure tion (Gruba 2004b). The exchangeable K+ content was the of the stand, the understory vegetation, and micro-relief second property of the humus horizon that was shown by conditions) (O’Donnell et al. 2009). The humus-mineral the multiple regression analysis to affect the site index of horizon is better for assessing the quality of soils and sites spruce stands. According to the literature, spruce dieback than the organic horizon. The humus-mineral horizon is caused by a long-term disease process, which may have contains weathered, earthy parts that are associated with been initiated by rainfall deficits (Lexer et al. 2000). We much processing, and it has a more stable organic matter assume that a K+ deficiency in the soil (K+ is responsible fraction (Rumpel and Kögel-Knabner 2011). Additionally, for proper hydration and cell turgor) (Walker et al. 1996) the bio-physico-chemical properties of the humus-miner- leads to disorders in the growth of spruce stands and the al horizon are less variable. Mismatches between the tree subsequent growth inhibition. Gömöryova and Gömöry species composition and site conditions lead to changes (1995) proved in their study that there is a significant re- in soil properties (Maciaszek et al. 2000, Maciaszek et al. lation between the K+ content in the soil and the height of

2016, Vol. 22, No. 1 (42) ISSN 2029-9230 8987 BALTIC FORESTRY RELATIONS BETWEEN SITE CHARACTERISTICS AND SPRUCE STAND PRODUCTIVITY J. LASOTA ET AL. spruce stands. The total organic C content in the organic References horizon and the exchangeable K+ content in both horizons were the properties that best explain the variability of the Afif-Khouri, E., Álvarez- Álvarez, P., Fernandez-López, J., spruce site index. The K+ level is associated with meta- Oliveira-Prendes, J.A. and Cámara-Obregón, A. 2011. In- fluence of climate, edaphic factors and tree nutrition on site bolic processes and proper cell hydration. Additionally, index of chestnut coppice stands in north-west Spain. Forestry the deterioration of climatic conditions for the growth of 84(4): 385-396. spruce is closely associated with a higher accumulation of Bošela, M., Mališ, F., Kulla, L., Šeben, V. and Deckmyn, G. 2013. weakly decomposing organic matter on the surface of the Ecolohgically based height growth model and derived raster maps of Norway spruce site index in the Western Carpathians. mineral soil (Drewnik 2006). European Journal of Forest Research 132: 691-705. The area of the Sudety Mountains covered by the anal- Drewnik, M. 2006. The properties of topsoil humus horizons in the ysis in this study has unique characteristics. A large part of Polish Carpathians. Roczniki Bieszczadzkie 14: 221-235. the Sudety Mountains, especially the Izerskie and Karko- Farrelly, N., NiDhubhain, A. and Nieuwenhuis, M. 2011. Sitka spruce site index in response to varying soils moisture and nosze Mountains, were affected by an ecological disaster: nutrients in three different climate regions in Ireland. Forest a massive dieback of forest stands as a result of the strong Ecology and Management 262 (12):2199-2206. impact of industrial emissions in the 1970s (Landmann and Gömöryova, E. and Gömöry, D. 1995. Relationships between en- Bonneau 1995, Sienkiewicz et al. 2005). The tested spruce vironment al factors and height growth and yield of Norway spruce stands: a factor-analytic approach. Forestry 68(2): 145- stands survived, but for a long time the area has remained 152. under the influence of acid rain and toxic emissions. Our Gruba, P. 2004a. Potentially toxic forms of aluminium in soil – results indicate that the acidity of the forest soil, as well selected aspects of determination and interpretation of the re- as the nutrient cycle, affects the spruce site index. These sults. Ecological Chemistry and Engineering 11, 7: 573-578. Gruba, P. 2004b. Aluminium toxicity in forest soils. Sylwan 1: 50- soil properties may enhance the negative effects of stress 56. https://www.researchgate.net/publication/258156412_Al- factors, leading consequently to deterioration of spruce uminium_toxicity_in_forest_soils?ev=prf_pub productivity and, in extreme cases, to the disintegration of Hägglund, B. and Lundmark, J.E. 1977. Site index estimation stands. Strongly acidified soils with a K+ deficit will show by means of site properties Scots pine and Norway spruce in Sweden. Studia Forestalia Suecica 138: 5-38. a higher susceptibility to stress factors. To reduce the nega- Kariükštis, L. and Jodvalkis, A. 2005. The theoretical fundamen- tive impact of stress factors, one should ensure the correct tals of forming of the most productive stands. Baltic Forestry cycling of nutrients and prevent soil acidification. These 11(2): 38-50. soil properties can be improved by breeding spruce with Kuliešis, A., Saladis, J. and Kuliešis, A.A. 2010. Development and productivity of young Scots pine stands by regulating density. an admixture of deciduous species. These actions may be Baltic Forestry 16(2): 235-246. more effective at lower positions on a rich geological sub- Landmann, G. and Bonneau, M. 1995. Forest decline and atmo- strate (sandstone, gabbro, or greenstone). spheric deposition effects in the French Mountains. Springer Topographic factors do not fully account for the vari- Verlag, Berlin, Germany. Lexer, M.J., Vacik, H., Hönninger, K. and Unegg, F. 2000. Imple- ability of the site index of spruce stands in the Sudety menting a decision support for silvicultural decision making Mountains. The regression analysis indicates that eleva- in low-elevation Norway spruce forests. In: Klimo, E., Hager, tion explains 49% of the site index variability, while 20 % H., Kulhavý J. (eds.): Spruce Monocultures in Central Europe of the site index variation of spruce stands depends on soil – Problems and Prospects. European Forest Institute, p. 11-27. Libiete, Z. 2008. The use of forest resource inventory data in the properties. Using the properties of the humus-mineral ho- analysis of regional productivity differences in Pine and rizon rather than those of the organic horizon resulted in a Spruce stands in Latvia. LLU Raksti 20(315): 53-65. more accurate estimation of the site index. Properties as- Maciaszek, W., Gruba, P., Januszek, K., Lasota, J., Wanic, T. sociated with the movement of nutrients, in particular K+, and Zwydak, M. 2000. Degradacja i regradacja gleb pod wpływem gospodarki leśnej na terenie Żywiecczyzny [Deg- had the largest effects on the site index of spruce stands. A radation and regradataion soil under the influence of forest K+ deficiency in the mountain soils can lead to the growth management in Żywiec region]. Wydawnictwo AR in Krakow inhibition of spruce stands. Additionally, the concentra- (in Polish). tion of Al3+ in the sorption complex has an inhibitory ef- Maciaszek, W., Gruba, P., Lasota, J., Wanic, T. and Zwydak, 3+ M. 2009. Physicochemical properties of soils under natu- fect on site productivity. Furthermore, the Al CECE ratio ral stands and spruce monocultures in the Beskid Zachodni. can be treated as an indicator of acidity. Sylwan 153: 338-345. https://www.researchgate.net/publica- tion/258154203_Physicochemical_properties_of_soils_un- Acknowledgements der_natural_stands_and_spruce_monocultures_in_Beskid_ Zachodni?ev=prf_pub Małek, S. and Barszcz, J. 2008. Stability of Norway spruce (Pi- This work was financed by the State Forests National cea abies [L.] Karst.) stands in the Beskid Śląski and Beskid Forest Holding in Poland within the project: “Improve- Żywiecki Mts. from the aspect of their nutrition status. Jour- ment the diagnosis of sites for the mountain areas based nal of Forest Science 54 (2): 41−48. Małek, S. 2010. Nutrient fluxes in planted Norway spruce stands of on soil site index (SIG) introduced for the diagnosis of different age in Southern Poland. Water, Air and Soil Pollution sites in lowland and upland areas”. 209: 45–59.

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Małek, S., Januszek, K., Keeton, W., Barszcz, J., Kroczek, M., a review of the evolution of dendrometric concepts for even- Błońska, E. and Wanic, T. 2014. Preliminary effects of fertil- aged stands. Forestry 81 (1): 13-31. ization on ecochemical soil condition in mature spruce stands Socha, J. 2008. Effect of topography and geology on the site index experiencing dieback in the Beskid Śląski and the Żywiecki of Picea abies in the West Carpathian, Poland. Scandinavian Mts., Poland. Water Air and Soil Pollution 225: 1971. Journal of Forest Research 23: 203-213. O’Donnell, J.A., Romanovsky, W.E., Harden, J.W. and Mc- Socha, J. 2011. Site index curves for Norway spruce on mountains Guire, A.D. 2009. The effect of moisture content on the ther- habitats. Sylwan 155 (12): 816-826. mal conductivity of moss and organic soil horizons from black Socha, J. 2012. Long-term effect of wetland drainage on the pro- spruce ecosystems in interior Alaska. Soil Science 174(12): ductivity of Scots pine stands in Poland. Forest Ecology and 646-651. Management 274: 172–180. Pacheco Marques, C. 1991. Evaluating site quality of even aged Starr, M., Saarsalmi, A., Hokkanen, T., Merilä, P., Helmisaa- maritime pine stands in Northern Portugal using direct and in- ri, H.S. 2005. Models of litterfall production for Scots pine direct methods. Forest Ecology and Management 41(3-4): 204 (Pinus sylvestris L.) in Finland using stand, site and climate Rumpel, C. and Kögel-Knabner, I. 2011. Deep soil organic mat- factors. Forest Ecology and Management 205: 215-225. ter – a key but poorly understood component of terrestrial C Walker, D.J., Leigh, R.A. and Miller, A.J. 1996. Potassium ho- cycle. Plant and Soil 338: 143–158. meostasis in vacuolated plant cells. Plant Biology 93:10510- Sewerniak, P. and Pernik, A. 2012. Regression models for impact 10514. of soil properties on site index class of Scots pine (Pinus syl- WRB (World Reference Base for Soil Resource). 2006. FAO, ISRIC vestris L.) stands in south-western Poland. Sylwan 156(8): and ISSS. 563-571. Zwoliński J. 2003. Ocena zagrożenia lasów świerkowych w Sienkiewicz, R., Krzaczkowski, P. and Twarowski, R. 2005. Beskidzie Śląskim przez zanieczyszczenia powietrza atmos- Zanieczyszczenie powietrza i opadów atmosferycznych w ferycznego. [Risk assessment of spruce forests in the Silesian Karkonoszach [Pollution of air and precipitation in the Kar- Beskid caused by air pollution]. Prace Instytutu Badawczego konosze Mountains]. In: Karkonosze, przyroda nieożywiona Leśnictwa A 1: 53−68 (in Polish). i człowiek [The Karkonosze Mountains, inanimate nature and people] (Mierzejewski M.P., ed.). Publisher University of Received 03 March 2015 Wroclaw, p. 438-452 (in Polish). Skovsgaard, J.P. and Vanclay, J.K. 2008. Forest site productivity: Accepted 25 January 2016

2016, Vol. 22, No. 1 (42) ISSN 2029-9230 9189 BALTIC FORESTRY EFFECT OF GREEN WASTE COMPOST APPLICATION ON AFFORESTATION SUCCESS J. JÄRVIS ET AL. Effect of Green Waste Compost Application on Afforesta­tion Success

JÜRI JÄRVIS1*, MARI IVASK1, LEMBIT NEI1, ANNELY KUU1 AND AARNE LUUD2 1 Tallinn University of Technology, Tartu College, Puiestee 78, 51008 Tartu, Estonia; * Corresponding author [email protected], tel. +372 511 9714 2 AS Tallinna Vesi, Ädala 10, 10614 Tallinn, Estonia

Järvis, J.*, Ivask, M., Nei, L., Kuu, A. and Luud, A. 2016. Effect of Green Waste Compost Application on Afforestation Success. Baltic Forestry 22(1): 90-97.

Abstract

The impact of soil amelioration with green waste compost in the afforestation of depleted peat fields and sand pits was studied. Drilled planting holes (50 cm deep, 20 cm in diameter, 15.7 litres in volume) were filled with fertile compost soil. Containerized yearling seedlings of Alnus glutinosa (L.) Gaertn., Betula pendula Roth and Populus tremula (L.) × P. tremuloides Mischx. or bare- rooted ones of Alnus incana (L.) Moench were planted into the compost-filled planting holes (test seedlings) and control seedlings into untreated soil. The test growth period lasted for three consecutive growing seasons in 2012–2014. Compost increased significantly the total three-year height growth of the test seedlings compared to the control ones on the depleted peat mine test site in all four species studied. A significant increase in the total three-year height growth of the test seedlings compared to control ones was also observed in black alder on the sandy loam and sand test sites. A high mortality rate was observed on the sand test site among control seedlings of black alder and among silver birch and hybrid aspen, both test and control seedlings. An irrigation test on sandy loam test site (2014) gave significantly improved height growth to the tested black alder seedlings.

Keywords: green waste compost; compost application; planting seedlings; planting site; height growth; soil aeration; water retention.

Introduction used for improving sandy soils water retention properties (Singh et al. 2011, Shahid et al. 2012). Different mulching In Estonia, the renewable energy sectors are priority solutions using plastic, ridges and furrows for preventing areas for ensuring sustainable development (Wilkins et al. water evaporation with a combination of rainwater col- 1998). The reforestation of depleted peat and sand mining lecting abilities are also tested (Wang et al. 2009, 2011). areas is often complicated due to the unfavourable physi- Usage of the water retention ability of modified clay was cal, chemical and biological properties of soils. On peat- analysed by Zhang and Wang in 2013. Usage of Biochar lands, nutrient deficiencies or imbalances, low aeration and as a water retention medium in soil was tested in sandy excess water content can restrict the growth of seedlings loam soils (Ulyett et al. 2014). In the case of low water (Pearson et al. 2011). In depleted sand mines (sand pits), retention ability only in the upper layer of soil, conduct- lack of water and nutrients are limiting factors for affores- ing plant root growth through the dry upper soil layer to tation. The topsoil may easily desiccate during warm and deeper moist layers levels has been successful by using windy periods, and planted tree seedlings face the risk of artificial wick-roots (Jarvis et al. 2012). unsuccessful growth (Castro et al. 2005, Close et al. 2005). Watering planted forest trees to ensure adequate root There are several methods that enable better water re- development and initial growth is suggested by Goor and tention in sand soil. For example, inserting approximately Barney (1968). The root systems of plants are able to per- 1 cm thick manure-based organic layers 45-60 cm deep form water redistribution in soil upwards, downwards and into the sand can accumulate rainwater on the organic bar- horizontally using hydraulic redistribution. Hydraulic re- riers and enable cereal plants (rye and wheat) to produce distribution is described by several authors as a passive double grain yield compared to test sites, where the same water movement through roots from moister soil areas or amount of manure was mixed into the upper 25 cm of sand layers to roots and exiting roots in soil in areas with lower (Egerszegi 1964). Underground water percolation barriers water potential (Caldwell et al. 1998, Schulze et al. 1998, are made from sheet plastic (Smucker 2012) or a layer of Brooks et al. 2002, Liste and White 2008). asphalt a few millimetres thick (Saxena et al. 1969, Palta The mechanism anticipated to support further tree and Blake 1974). Hydrogel superabsorbent materials are growth is expected to work as follows: if the roots ex-

2016, Vol. 22, No. 1 (42) ISSN 2029-9230 9092 BALTIC FORESTRY EFFECT OF GREEN WASTE COMPOST APPLICATION ON AFFORESTATION SUCCESS J. JÄRVIS ET AL. tend into the surrounding soil with the help of nutrients Drilling planting holes and filling them with compost is achieved from the extended substrate supply, the bacte- expected to mitigate the problems with low soil aeration rial and mycorrhizal fungi communities that exist in the in peat and too low or too high moisture level and lack of applied compost will spread out into the surrounding some nutrients in all target soils. The hypothesis tested in nutrient-poor soil along the growing roots. The bacterial the current work was that locally enhanced soil conditions and mycorrhizal fungi communities use tree root exudates around the roots of the planted tree seedlings may enable to survive. Several authors (Uroz et al. 2009, Calvaruso faster development of the seedlings in poor soil. et al. 2010, Zhang et al. 2014) have found that the bac- terial communities inhabiting the areas around the tree Materials and Methods roots and using root exudates for nutrition can decompose soil minerals making soil more versatile and more suit- General description of the test sites able for further growth of the same trees. Decomposition Three test sites within 40 km of Tartu (coordinates: of soil mineral particles is also performed by mycorrhi- 58°23’ N; 26°43’ E; elevation: 30-60 m above sea level) zas (Hagerberg et al. 2003, Yuan et al. 2004, Schöll et were studied (Figure 1). al. 2008). In addition to bacterial and mycorrhizal fungi The peat test site was located on a depleted peat field communities around the roots, root exudates also cause that was used 15 years ago for producing peat for energy mineral decomposition of the surrounding poor soil com- (cutover peatland area). The test site was adjoined by a 60 ponents into the forms with higher assimilability for the cm deep ditch from the west, an area with 6 m tall trees from same trees by themselves (Dakora and Phillips 2002). the north and east and an open treeless area in the south. All selected four tree species: grey alder (Alnus in- The depth of peat was 74 cm on average. The peat layer was cana (L.) Moench), black alder (Alnus glutinosa (L.) underlaid with clay. The level of groundwater varied during Gaertn.), silver birch (Betula pendula Roth) and hybrid the test period from 40 to 70 cm depending on the rainwater. aspen (Populus tremula (L.) x P. tremuloides Mischx.) are All the seedlings were planted on 30 May, 2012. able to regenerate from roots or stumps after cutting (Uri The sand and sandy loam test sites were located on et al 2010). Alder species are pioneer species having abil- the flattened areas of sand pits with open treeless spots in ity to accommodate nitrogen-fixing bacterial communities the south. Groundwaters were several meters deep in both (Frankia alni) in root nodules (Claessens et al. 2010). cases. All the seedlings were planted on the sandy loam Though afforestation can be supported with mineral test site on 30 April, 2012 and on the sand test site on 30 fertilizers, wood or peat ash (Pärn et al. 2009, Kikamägi May, 2012. et al. 2013), the substances would not help mitigate prob- According to data of the weather stations near- lems with low aeration of the soil and too low or too high est to the test sites, precipitation in millimetres and ef- moisture. The aim of the current study was to test if these fective heat (average day temperature over +5°C) sums problems could be overcome by local enhancement of during the 2012-2014 vegetation periods are presented in growth conditions around the roots of tree seedlings, us- Table 1. These data are provided to indicate the climatic ing nutrient rich and air permeable green waste compost background since plants growth rate depends on solar heat with a good water holding capacity during afforestation. and water received from atmospheric precipitation.

Figure 1. Location of the test sites (1 – peat, 2 – sand, 3 – sandy loam) for assessment of the effect of compost application on the height growth of forest tree seedlings on soils of vari- ous types

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Table 1. Precipitation in millimetres and effective heat (over +5°C) sum in degrees C on the test sites from 01 April to 31 October during the three-year test period

Soil Peat Sandy loam Sand Precipitation, Effective heat Precipitation, Effective heat Precipitation, Effective heat Year mm sum, deg. C mm sum, deg. C mm sum, deg. C 2012 524 1606 503 1478 510 1571 2013 311 1754 403 1662 345 1802 2014 444 1659 448 1337 476 1723

Planting holes and compost site soils without having transpiration influence from the The planting holes were made with soil auger “Stihl seedlings. For comparison, the VWC values were mea- BT 121”. In order to ensure maximum volume of compost sured in the middle of growing season on 22 June 2013 available per plant, the biggest available 20 cm in diameter to have a full transpiration impact from the seedlings on soil drill was used to drill 50 cm deep planting holes. The water content in soil under compost application and in the volume of each drilled hole was 15.7 litres. Deep planting original soil. Both measurements were made two days af- holes were chosen because earlier tests with containerized ter a moderate rainfall (Table 3). seedlings have shown a positive correlation between in- In Table 2 the values of soil parameters were deter- creased container depth and seedling growth (Close et al. mined from soil samples as follows: pHKCl (pH was de- 2005, Chirino et al. 2008). Growing seedlings in deeper termined in KCl solution), total nitrogen (N) by Kjeldahl containers increases the number of primary roots and im- method, available phosphorus (P) content, potassium (K) proves the plant root system architecture (Nelson 1996). and calcium (Ca) by flame photometry (Helrich 1990), The relatively large planting hole filled with compost was magnesium (Mg) by flow injection analysis (Page et al, expected to minimize the seedlings transplanting stress 1982) and the soil organic matter content by the method by holding water, air and nutrients, as well as enabling of loss on ignition (Schulte 1995). the seedlings to form their own root structure as freely as On three test sites studied, soils were deficient in sev- possible. The planting holes were filled with green waste eral nutrients (Table 2). The planting holes were drilled into compost and compacted lightly. the soil and filled with compost (in the Table 2). The N, P, Green waste compost used in the tests (its properties K, Ca and Mg contents in the green waste compost were are given in Table 2) was produced from only plant-origin considered to be high or average for plant growth (Pihelgas residues in the Tartu Tree Nursery. The raw materials of the 1983, Kevvai 1996, Loide 2008). The concentrations of P compost were weeds, grass clippings and peat formerly used and K in the test sites soils are generally considered to be for growing forest-tree seedlings in seedbeds. This compost low or very low. A very high nitrogen and very low phos- was produced by piling the components and mixing already phorus content in peat is common. In this particular peat, matured compost into the piles during several years. Plant the calcium and magnesium contents were also very high, pathogens in the compost were not investigated. which sets off this peat from the majority of peats.

Moisture and nutrient content in soils and compost Planting of seedlings The volumetric water content (VWC) of the soil was Twenty black alder (Alnus glutinosa (L.) Gaertn.) measured with a Fieldscout TDR 300 (time domain re- and grey alder (Alnus incana (L.) Moench) seedlings (10 flectometry) soil moisture meter using 200 mm measuring test and 10 control seedlings) were planted on the peat rods. Volumetric water content values were measured in and sand test sites. Also, 10 silver birches (Betula pen- 04 October 2012 at the end of growing season to show the dula Roth) and 10 hybrid aspens (Populus tremula (L.)×P. difference in VWC between compost additions and test tremuloides Mischx.) were planted, with 5 test and 5 con-

Table 2. Results of chemical analysis of compost used for filling planting holes and soils from the test sites (soil layer 0-15 cm)

P, K, Ca, Mg, Organic matter, pH N, % KCL mg kg-1 mg kg-1 mg kg-1 mg kg-1 %

Compost 6.72 0.470 325.63 401.32 3622.80 505.87 14.63

Peat 5.39 2.33 0.185 24.62 15307.00 1651.83 70.00 Sand 8.67 0.005 4.31 9.94 1975.10 24.70 0.25 Sandy loam 6.25 0.029 39.10 36.80 338.87 48.69 0.73

2016, Vol. 22, No. 1 (42) ISSN 2029-9230 9294 BALTIC FORESTRY EFFECT OF GREEN WASTE COMPOST APPLICATION ON AFFORESTATION SUCCESS J. JÄRVIS ET AL. trol seedlings planted alternately (60 seedlings in total per mal browsing damage were excluded from the data. Also, test site, 30 test and 30 control seedlings alternately). On all negative annual height growths were excluded from the sandy loam test site, the number of each species of the height growth analysis. the seedlings was doubled (120 seedlings in total, 60 test and 60 control seedlings alternately). The distances be- Statistical analysis tween the seedlings were 2 m on all sites. Statistical analyses were performed with the MS All black alder and silver birch seedlings were grown Excel 2013 software. Two sample t-tests with assuming in containers with dimensions 60×60×80 mm; the hybrid unequal variances were used to test the effect of added aspen seedlings in containers with 60×80×80 mm. The compost on height growth. All statistical tests were con- grey alder seedlings were bare-rooted (grown in nursery). sidered significant at the level p < 0.05. All these seedlings were one year old. The test seedlings were planted into the centres of Results the compost fillings of the planting holes. Three litres of water was poured to each planted seedling in each compost Moisture content in soil soil filling during planting because the compost was too dry Supplied compost in peat may provide better aera- for planting. The same number of control seedlings were tion compared to the surrounding dense peat layers. Based planted directly into the original soil of the test plots (peat, on volumetric water content (VWC) measurements, the sand and sandy loam). Also, the control seedlings were irri- compost around the test plant roots was significantly dri- gated with 3 litres of water to provide equal treatment (ex- er on average than around the control plants roots when cept control seedlings on peat because the peat was soaked measured after the vegetation period (2012) and in the wet at the time of planting). No extra irrigation was carried middle of the vegetation period (2013). Undisturbed peat out after the planting day on any of the test sites. measured in 1 m distance from the control seedlings con- tained more water in both cases (Table 3). Irrigation test series on sandy loam The VWC trend was changing on the sandy loam To test the seedlings growth response to higher soil being higher after and lower during the vegetation period water content on sandy loam, three groups of 12 one year in compost around the test seedlings. old black alder seedlings were planted on 27 April, 2014. Improvement of the water retention ability of the The seedlings of two groups were planted into 1 m deep compost was detected on the sand test site both during and 10 cm in diameter holes with compost fillings (with a and after the vegetation period. volume of 7.9 litres). The third (control) group of 12 seed- lings was planted into untreated sandy loam soil. For one Height growth of the groups with compost fillings, an automatic drip ir- Black alder seedlings gave significantly higher rigation system was installed (model Irrigatia SOL C-24) growth compared to control seedlings through three-year that supplied 1 litre of water per seedling per day. growth test on all test sites. It is important to note that due to a high number of dieback of the shoots of untreated Measurements of height growth seedlings on sand the number of test seedlings with posi- The seedlings growth was monitored by measuring tive height growth was too small to be analysed during the their height with a measuring tape with 1 mm accuracy. second and third year. The height measurements were made after each vegeta- On the peat test site almost all the test seedlings of all tion period from 2012 to 2014. All the seedlings with ani- species studied showed significantly higher height growth

Table 3. Average volumetric water contents in soils (%) measured two days after rain

Peat test site Sandy loam test site Sand test site

Measure- ment Compost Soil Compost Soil Compost Soil Soil Soil Soil location / around around around around around around without without without measure- ment test control test control test control seedling seedling seedling time seedling seedling seedling seedling seedling seedling

After vegetation 27 39 43 23 18 20 18 8 8 period

In the middle of 14 28 34 8 9 11 5 3 3 vegetation period

2016, Vol. 22, No. 1 (42) ISSN 2029-9230 9593 BALTIC FORESTRY EFFECT OF GREEN WASTE COMPOST APPLICATION ON AFFORESTATION SUCCESS J. JÄRVIS ET AL. compared to the control seedlings every year except silver The number of observations is small to draw a conclusion birch during the first year (Figure 2). but the result can be considered as an indication. An additional positive effect of compost was also ob- served on the peat test site. The compost seemed to protect Effect of irrigation newly planted seedlings from frost heaving. All the seed- The results of the irrigation test during the 2014 lings in compost soil were well rooted and stood firmly in growing season showed a statistically significant differ- the ground, whereas four control seedlings out of 30 were ence in height growth between irrigated seedlings grown lifted by frost heaving after the first winter after planting. in compost compared to non-irrigated seedlings in com- post and the seedlings in untreated soil (Figure 3).

Figure 2. Comparison of the height growth (cm) of test seedlings “t” (with compost application) and control seedlings “c” (planted without treatment) belonging to four tree species under study on three test sites with peat, sandy loam and sand soils, respectively. SE is the standard errors of 3-year cumulative height growths (cm), error bars on graph represent standard errors. Number is the number of seedlings that gave positive height growth on the third growth year. Σ 3 years is the resultant height growth during three consecutive years (2012-2014)

Figure 3. Average annual height growth (cm) of one-year old grey alder seedlings during irrigation test on sandy loam test site in 2014 Growth is the height growth (cm); SE is the standard error of height growth (cm), error bars on graph represent standard errors; Number is the number of seedlings

2016, Vol. 22, No. 1 (42) ISSN 2029-9230 9694 BALTIC FORESTRY EFFECT OF GREEN WASTE COMPOST APPLICATION ON AFFORESTATION SUCCESS J. JÄRVIS ET AL.

Growth success ratio during the period of water availability compared to seed- The seedling response to the compost fillings can lings without treatment. No significant differences in be expressed as a percentage of seedlings with positive height growths were observed between grey alder test and height growths. Test seedlings had the following positive control seedlings, however, both had constant and steady height growths: 97 % cases on peat, 89 % on sandy loam growth through three years. and 70 % on sand compared to control seedlings (52 %, On the sandy loam test site, the higher nutrient con- 81 % and 37 %, respectively). tent in the compost was expected to give a significant ef- fect on the height growth of the test seedlings of all tree Discussion and Conclusions species compared to control seedlings. However, the ex- pected trend appeared only with black alder seedlings. On the peat test site, the compost added into planting The result corresponds to the tests performed with added holes was more aerated than the surrounding peat and en- biochar (Ulyett et al. 2014) or superabsorbent (Singh et abled higher root activity that resulted in faster growth of al. 2011, Shahid et al. 2012), where the added substances the test seedlings. The surrounding peat had a higher wa- improved water retaining capacity of sandy loam. The ter content compared to the compost-filled planting holes suspected water shortages in compost between rainfalls and acted as a water reserve always available for the roots were expected to be the reason for only modest growth grown out from the compost. In addition, the high growth improvement with test seedlings in compost fillings. The of the test seedlings was probably supported by a very conducted additional irrigation test (see “Effect of irriga- high level of nitrogen in the surrounding peat. The practi- tion”) seems to avoid a soil water deficit on the test site. cal absence of phosphorous in the peat was compensated However, the current test does not explain the roughly by its abundance in the compost. The height growth of the doubled height growth of both test and control seedlings test seedlings was higher during the second growing sea- during the third year, despite the precipitation rate being son, when there was a comparatively low amount of pre- roughly similar and the effective heat sum being smaller cipitation and relatively high effective temperatures (Table than during the previous years. 1). Higher growth of test seedlings with compost addition The study showed the differences in seedlings height corresponds to the results of another peatland afforesta- growth on test sites and between tree species. All the test tion test with sewage sediment compost, where compost seedlings (except silver birch during the first year) gave was spread uniformly over the test area and mixed with significantly higher three-year height growth on the peat peat soil (Pikka 2005). Growth test on peat substrate with test site. This result corresponds to the results of the stud- added sewage sludge compost and wood ash showed im- ies (Pärn et al. 2009, Kikamägi et al. 2013) that described proved growth of willows (Lazdina et al. 2011), which is improved height growth of silver birch and black alder in accordance with the results of current work. in response to ash addition. Also, statistically significant On the sand test site, the addition of compost in- differences in height growth between the irrigated seed- creased significantly only the height growth of the black lings grown in compost compared to non-irrigated seed- alder seedlings during the first two years and silver birch lings in compost and the seedlings in untreated soil were seedlings during the first growing year. Improved height measured. It confirms the statement that after planting, growth can be attributed to better water retention ability watering of forest tree seedlings results in their better and fertility of compost. Similar improvements of water establishment (Goor and Barney 1968). The hypothesis holding capacity in sand soils are achieved with addi- was confirmed showing that added compost caused sig- tion of modified clay (Zhang and Wang 2013) or rainwa- nificantly improved height growth of some tree species ter collecting solutions that use plastic film and changed seedlings on some soil types, hence enhanced the growth surface profile (Wang et al. 2009, 2011). Despite better conditions locally. water holding capacity compared to the surrounding sand, the amount of rainwater that accumulated into the com- Recommendations for future testing post-filled planting holes was not sufficient to provide a This work was expected to detect which species on constantly available supply for the test seedlings. Severe which soils can benefit from compost amendment. The drying of the shoot tops (dieback) occurred among the number of seedlings used in the tests was rather small and control seedlings of black alder, silver birch and hybrid the results of this experiment will be a good starting point aspen during the second growing season, when precipi- for further testing with a larger number of seedlings fo- tation was comparatively low and effective temperatures cusing on species and soils selected based on the results of were high. Dieback continued during the third growing the current work. Drilling planting holes and filling them season despite milder growing conditions. Higher nutrient with compost can be mechanized and automatized or even content in the compost compared to the surrounding sand robotized to some extent in levelled areas like depleted was expected to accelerate the treated seedlings growth peat fields and sand. In the case of deep planting holes,

2016, Vol. 22, No. 1 (42) ISSN 2029-9230 9795 BALTIC FORESTRY EFFECT OF GREEN WASTE COMPOST APPLICATION ON AFFORESTATION SUCCESS J. JÄRVIS ET AL. root activity should be supported with artificial aeration mental approach. Plant Ecology 181: 191-202; http://dx.doi. by embedding perforated plastic pipes into planting holes. org/10.1007/s11258-005-6626-5. Chirino, E., Vilagrosa, A., Hernández, E.I., Matos, A. and Valle- In further tests, other kinds of compost can be used, for jo, V.R. 2008. Effects of a deep container on morpho-func- example, compost of city sewage sediments, which may tional characteristics and root colonization in Quercus suber reduce the price of current afforestation method and help L. seedlings for reforestation in Mediterranean climate. For- reuse sewage waste. The sewage compost cannot be used est Ecology and Management 256 (4): 779-785; http://dx.doi. org/10.1016/j.foreco.2008.05.035. for agricultural purposes: it may contain an excess amount Claessens, H., Oosterbaan, A., Savill, P. and Rondeux, J. 2010. of chemical contaminants that can be assimilated by food A review of the characteristics of black alder (Alnus glutinosa crops (Lillenberg et al. 2010, Nei et al. 2011). However, (L.) Gaertn.) and their implications for silvicultural practices. sewage compost is rich in minerals, enabling long-lasting Forestry 83: 163-175; http://doi:10.1093/forestry/cpp038. Close, D.C., Beadle, C.L. and Brown, P.H. 2005. The physi- supply for the fast growth of plants. Chemical contami- ological basis of containerized tree seedling ‘transplant nants are expected to be consumed from compost by for- shock’: a review. Australian Forestry 68 (2): 112-120, DOI: est tree plants and accumulated in their timber, enabling to 10.1080/00049158.2005.10674954; http://dx.doi.org/10.1080 draw pollutants out from circulation (López et al. 2014). /00049158.2005.10674954. Dakora, F.D. and Phillips, D.A. 2002. Root exudates as mediators The amount of compost needed in the form of the fill- of mineral acquisition in low-nutrient environments. Plant ings in the planting holes is remarkably smaller and is and Soil 245: 35-47; http://dx.doi.org/10.1007/978-94-017- expected to pose a smaller threat to groundwater through 1570-6_23. leaching components compared to the method covering Egerszegi, S. 1964. Plant Physiological Principles of Efficient Sand Amelioration. Agrokemia es Talajtan 13: Supplementum 209- the soil with a sewage sediment compost layer for affores- 218; http://aton.hu:8080 [Cited 25 Jun 2014]. tation (Pikka 2005). Automated irrigation systems could Goor, A. Y. and Barney, C.W. 1968. Afforestation. 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2016, Vol. 22, No. 1 (42) ISSN 2029-9230 9997 BALTIC FORESTRY WOOD ASH FERTILISATION INCREASES BIOMASS PRODUCTION /.../ J. HYTÖNEN Wood Ash Fertilisation Increases Biomass Production and Improves Nutrient Concentrations in Birches and Willows on Two Cutaway Peats

JYRKI HYTÖNEN Natural Resources Institute Finland, Silmäjärventie 2, 69100 Kannus, Finland e-mail: [email protected]; tel + 358 29 532 3405

Hytönen, J. 2016. Wood Ash Fertilisation Increases Biomass Production and Improves Nutrient Concentrations in Birches and Willows on Two Cutaway Peats. Baltic Forestry 22(1): 98-106.

Abstract

The effect of wood ash (0, 6, 12, and 24 t ha-1) on the nutrient concentrations and biomass production in willows (Salix vimina- lis and S. x dasyclados) and birches (Betula pendula and B. pubescens) on two cutaway peats was studied in greenhouse conditions. In addition to ash, all treatments included fertilisation with nitrogen (150 kg N ha-1). The largest amount of wood ash increased the pH from 4.0 to 7.3 for Aitoneva peat and from 5.0 to 7.5 for Piipsanneva peat. Increasing the amount of ash also significantly increased extractable phosphorus, potassium, calcium, and magnesium concentrations in peat – even the smallest dose increased concentrations manifold compared to unfertilised peats. The growth of the studied species was affected by both peat type and fer- tilisation treatment. Unfertilised willows and willows fertilised with nitrogen died in Aitoneva peat and grew poorly in Piipsanneva peat. Biomass production of birches in unfertilised peat was low. Nitrogen fertilisation without ash did not increase growth. The best growth was recorded with the lowest dose of ash (6 t ha-1). Ash fertilisation significantly increased the foliar concentrations of phosphorus and potassium in all species studied and decreased those of calcium and magnesium. The study indicated that the original peat characteristics affect growth of seedlings even when the sites are fertilised. Wood ash proved to be a suitable fertiliser in afforestation of cutaway peatlands.

Key words: willow, birch, cutaway peatland, wood ash, fertilisation, biomass production

Introduction Uri et al. 2002, Hytönen and Saarsalmi 2009, Aosaar et al. 2012, Hytönen and Aro 2012, Johansson 2013). The need for reducing greenhouse gas emissions is Short-rotation plantations are usually established on increasing the value of renewable energy obtained from agricultural land. In peat-producing countries, peat-harvest- forests. Wood-based fuels and recovered fuels are play- ing areas are being released from production in increasing ing a leading role in Finland in attempts to reach national amounts. Accordingly, continuing energy production by and European Union goals for increasing the use of re- growing biomass for fuel with various energy crops could newable energy. The share of wood-based fuels in the to- be an attractive after-use option. Peat cutaway areas differ tal consumption of energy in Finland was 23 % in 2012 considerably from agricultural soils and forested peatlands (Ylitalo 2013). In addition to using wood fuels derived in their properties. They are characterised by usually low from existing forests, the establishment and utilisation of but variable peat thickness, low pH levels, high nitrogen woody-biomass energy plantations are gaining new inter- concentration, and low phosphorus and potassium concen- est in many countries. Short-rotation forestry involves trations in the residual peat (Aro et al. 1997, Kikamägi and the cultivation of rapidly growing deciduous tree species, Ots 2010, Kikamägi et al. 2013). The large nitrogen stores regenerated through sprouts, using short rotation peri- in the remaining peat layer are an advantage and could re- ods, intensive methods, and dense stocking. Salix species duce the need for fertilisation. However, nitrogen is bound have been widely used in the short-rotation experiments in the organic matter in the peat and becomes available to conducted in Europe and North America (Hytönen 1996, plants via mineralisation of the organic matter. Nutritional Mola‑Yudego and González-Olabarria 2010, Pučka and problems may be encountered in afforesting of cutaway Lazdiņa 2013, Guidi Nissim et al. 2013, Āboliņa et al. peatlands; consequently, the success of afforestation will 2014, Heinsoo and Dimitriou 2014). Also, densely plant- depend in many cases on soil amelioration and fertilisa- ed alders, birches, and poplars may be interesting species tion (Kaunisto 1983, 1987, Hytönen et al. 1995, Hytönen for biomass production (Saarsalmi et al. 1992, Ferm 1993, 1996, Aro et al. 1997, Hytönen and Kaunisto 1999, Aro

2016, Vol. 22, No. 1 (42) ISSN 2029-9230 98100 BALTIC FORESTRY WOOD ASH FERTILISATION INCREASES BIOMASS PRODUCTION /.../ J. HYTÖNEN and Kaunisto 2003, Huotari et al. 2008, Kikamägi and Ots mass production of these species suitable for wood energy 2010, Kikamägi et al. 2013). production. Apart from short-rotation willows, growing of oth- er potential biomass crops (e.g. native deciduous trees, Material and methods downy birch, alders, aspen, and native willows) on cut- away peatlands is little known. However, there are indi- Experimental design cations that growing dense stands of native tree species Well-humified Carex peat was collected from two peat could yield considerable amounts of biomass on cutaway cutaway areas, one in Kihniö (Aitoneva, 62o 12’ N, 23o 18’ peatlands (Hytönen and Kaunisto 1999, Hytönen and E) and the other in Haapavesi (Piipsanneva, 64 o 06’ N, 25o Saarsalmi 2009, Renou-Wilson et al. 2010). In addition 36’ E). The species used were downy and silver birch, as to downy birch (Betula pendula L.), silver birch (B. pu- seedlings, and willow (S. × dasyclados, clone P6011 and bescens Ehrh.), which does not grow naturally on peat- S. viminalis, clone S1511), as cuttings. Before planting, lands, has been shown to thrive well on cutaway peatlands the birches were grown in nutrient-poor unfertilised peat (Kaunisto 1981, Aro et al. 1997, Hytönen and Saarsalmi to 10–15 cm height. The willow cuttings had been taken in 2009, Hytönen and Aro 2012). Silver birch normally the previous autumn and kept in cold storage. Treatments produces a higher yield than downy birch (e.g. Koivisto included an unfertilised control and wood-ash levels of 0, 1959, Karlsson et al. 1997, Saramäki and Hytönen 2004, 6, 12, and 24 t ha-1. Ash was mixed in the 0-10 cm peat Johansson 2007, Hytönen et al. 2014). layer before planting the seedlings. The loose wood ash For exotic willows, annual nitrogen fertilisation even came from the nearby Sievi municipal heating plant. All on nitrogen-rich cutaway peatlands is necessary (Hytönen wood-ash treatments featured fertilisation with 150 kg N 1995). Also, to ensure good survival and growth of the ha-1 as ammonium nitrate with lime in order to ensure that exotic willows, the peat pH has to be increased since the nitrogen did not limit growth. Thus the treatments were willows may even die out on acid peat in the absence of A0+0 (no ash, no nitrogen; unfertilised control), A0+N (no liming (Hytönen 2005). However, low pH has not had a ash + nitrogen), A6+N (ash 6 t ha-1 + nitrogen), A12+N negative effect on the growth of silver birch and downy (ash 12 t ha-1 + nitrogen) and A24+N (ash 24 t ha-1 + nitro- birch (Ericsson and Lindsjö 1981, Rikala and Josefek gen). The smallest ash dose (6 t ha-1) contained 204, 714, 1990, Hytönen 2005). 1470 and 276 kg ha-1 of P, K, Ca and Mg, respectively. Consumption of primary biomass for energy pro- The experiment employed a randomised block de- duction generates increasing quantities of wood ash. In sign with two replications. Two seedlings or two willow Finland, the total amount of wood ash produced annually cuttings (10 cm long) were planted in each pot, sized 4.8 by the forest industry is estimated to be 200,000–300,000 litres. Altogether 80 seedlings were planted in the pots. tonnes. Large amounts of wood ash have been produced Seedlings were grown in a greenhouse for 96 days, from in recent decades also in other countries, especially in mid-May to the end of August, in ambient lighting con- Scandinavia and North America (Pitman 2006). Wood ash ditions. During the experiment, air temperature in the contains many of the essential nutrients required for plant greenhouse varied within the range 17–24 oC. The seed- growth – except, notably, nitrogen (N) – so may have lings were irrigated whenever necessary to eliminate wa- potential as a fertiliser for cutaway peatlands where bot- ter deficit as a limiting factor. tom peat is especially low in phosphorus (P) and potas- sium (K). Long-lasting positive effects of wood ash on Measurements and analyses the growth of conifers on forested peatlands have been Two samples of the wood ash were analysed for nu- reported from many studies (e.g. Silfverberg 1996, Sil- trient concentrations in the laboratory (HCl extraction, fverberg and Hotanen 1989, Moilanen et al. 2002, 2005). atomic absorption spectrophotometry; for methods see Since wood ash is a good liming agent (Saarela 1991) and Halonen et al. 1983) and mean nutrient concentrations has been found to decrease peat acidity (e.g. Silfverberg were calculated (P 34 mg g-1, K 119 mg g-1, Ca 245 mg g-1, and Hotanen 1989, Hytönen and Aro 2012, Moilanen et al. Mg 46 mg g-1, Fe 609 mg g-1, Mn 16 mg g-1, Zn 172 mg kg-1, 2012, Kikamägi et al. 2013, 2014, Maljanen et al. 2014), Cu 185 mg kg-1, and B 90 mg kg-1). The P and K concen- it can replace standard liming for short-rotation willows. trations of the ash were considerably high; however, simi- The main aim of the study was to determine the suit- lar concentrations have been measured from wood ash ability of wood-ash fertilisation for short-rotation willows especially when birch wood has been burned (Silfverberg (Salix viminalis and S. × dasyclados) and birches (B. pen- and Issakainen 2001, Moilanen and Issakainen 2003). dula and B. pubescens) on cutaway peats from two areas At the end of the experiment, soil samples were tak- and its effect on the nutrient concentrations in foliage and en from 0-10 cm peat layer of the pots where the downy peat. The hypothesis was that wood ash containing phos- and silver birch had grown. Conductivity and pH of the phorus, potassium and micronutrients would increase bio- substrate were determined from soil-water suspension

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(soil:water = 1:2.5) Nitrogen concentrations in the samples analysis of variance separately for birches and willows. In were measured by the Kjeldahl method. Acid ammonium the statistical testing of willow foliar nutrient concentra- acetate – EDTA (pH 4.64) extractable phosphorus, potas- tion treatment A24+N was excluded due to small number sium, magnesium, and calcium concentrations were deter- of analysed samples. The variance model used included mined as outlined in Halonen et al. (1983). Phosphorus was as fixed factors fertilisation, peat type, tree species, their determined photometrically and potassium, calcium and interactions (species × peat, species × fertilisation, spe- magnesium using atomic absorption spectrometry (AAS). cies × peat type, species × fertilisation × peat type), and Foliar samples were composed of all leaves of seedlings block. The variance model for soil characteristics included growing in the pots. Their N concentration was analysed as fixed factors peat type, fertilisation, their interaction using the Kjeldahl method. P (vanado-molybdate method) (fertilisation × peat type), and block. The unfertilised soils and B (azomethine-H method) (Halonen et al. 1983) con- were also tested separately (peat type, block). Tukey’s test centrations were measured spectrophotometrically and K, was used in post hoc pairwise multiple comparisons. All Ca and Mg concentrations (HCl extraction) were analysed analyses were computed using the IBM SPSS Statistics with atomic absorption photometer (Halonen et al. 1983). 20.0 package. The sample size of willow leaves in treatment A24+N was so small that only one sample was analysed. Results The height and base diameter of the seedlings were measured at the end of the 96-day growing period. Then Soil characteristics the seedlings were cut at ground level and their leaves The mean concentrations of soil characteristics in were separated. The dry mass of foliage and stems with the two peats and different treatments are presented in branches was determined via drying to constant weight. Table 1. Since there were significant peat and fertilisation interactions the differences in soil characteristics between Statistical analyses unfertilised peats were tested separately. The two unfer- Differences in biomass and foliar nutrient concen- tilised peats differed significantly from each other in their trations between the treatments were tested by means of conductivity (F = 11.863, p = 0.018), pH (F = 125.00,

Table 1. Conductivity (Con.), pH, total nitrogen, acid ammonium acetate (AAc) extractable phosphorus, potassium, calcium and magnesium concentrations

Con. tot N P AAc K AAc Ca AAc Mg AAc Site Fertilisation pH μS cm-1 % mg l-1 mg l-1 mg l-1 mg l-1 Aitoneva A0+0 0.21 4.0a 1.5a 12.8a 73.8a 663a 133a A0+N 0.31 3.7a 1.5ab 4.5a 56.3a 581a 133a A6+N 0.35 5.3b 1.4ab 82.8a 867.5b 2525a 568a A12+N 0.80 6.8c 1.4ab 230.0b 2275.0c 7150b 1425b A24+N 1.33 7.3c 1.3c 285.0b 4025.0d 10050c 2050c

Piipsanneva A0+0 0.16 5.0a 2.1a 6.8ab 65.5a 1006a 140a A0+N 0.24 4.7b 2.1a 0.6a 32.5a 925a 138a A6+N 0.38 6.5c 2.0ab 84.8bc 656.3a 4275b 758b A12+N 0.66 6.9c 1.9abc 127.5c 1500.0b 4850b 868b A24+N 1.55 7.5d 1.9bc 133.5c 3535.0c 9850c 1725c

Fpeat 671.9 55.3 621.3 17.7 8.7 0.0 4.3

ppeat 0.000 0.000 0.000 0.000 0.000 0.966 0.048

Ffert 98.2 211.3 14.0 46.3 186.3 142.6 101.8

pfert 0.000 0.000 0.000 0.000 0.000 0.000 0.000

Fpeat*fert 1.8 6.6 0.9 6.4 2.1 5.1 4.2

ppeat*fert 0.157 0.001 0.462 0.001 0.114 0.003 0.009 Notes: F-values and p-values from analyses of variance. Means on each peat type that do not differ from each other according to Tukey’s test at a significance level of 0.05 are marked with the same letter; peat = peat type, fert = fertilisation treatment

2016, Vol. 22, No. 1 (42) ISSN 2029-9230 100102 BALTIC FORESTRY WOOD ASH FERTILISATION INCREASES BIOMASS PRODUCTION /.../ J. HYTÖNEN p = 0.000), N (F = 264.933, p = 0.000), and Ca (F = 13.256, biomass production (Table 2). Peat type and fertilisation p = 0.015) concentrations. Unfertilised Piipsanneva peat treatment had a significant effect on the growth of birches. had significantly higher pH, and a greater total N and ex- Birches grew better on Aitoneva peat than on Piipsanneva tractable Ca concentration than unfertilised Aitoneva peat, one (Table 2, Figure 1). The birches grew very poorly in while Aitoneva peat had higher conductivity. The extract- both cutaway peats in the absence of fertiliser application able P (Aitoneva 12.8 mg l-1, Piipsanneva 6.8 mg l-1) and K (Figure 1). Nitrogen fertilisation increased significantly (Aitoneva 73.8 mg l-1, Piipsanneva 65.5 mg l-1) concentra- only the height growth of birches. However, addition of tions did not differ significantly in the two peats. wood ash and nitrogen increased the biomass production Fertilisation treatments had a significant effect on all studied soil characteristics (Ta- ble 1). Nitrogen fertilisation on its own had only a small effect on soil characteristics; however, it decreased pH of Piipsanneva peat significantly. Addition of ash (ash + N) increased significantly soil pH and nutrient (extractable P, K, Ca, Mg) concentrations. With the use of 6 t ha-1 of wood ash peat pH, and K concentration increased significantly in Aitoneva peat and those of pH, Ca and Mg in Piipsanneva peat. Addition of 12 t ha-1 of ash increased significantly all measured soil characteristics except total nitrogen concen- tration. The highest ash application amount 24 t ha-1 increased nutrient concentrations in the peat considerably more. The highest ash dose (24 t ha-1) decreased the peat total N concentration significantly.

Growth of seedlings The two birch species did not differ from each other in their height, diameter and

Figure 1. Height, base diameter, and above- ground biomass of the birch and willow seedlings at the end of the experiment. Fertilisation treat- ments that do not differ from each other according to Tukey’s test at a significance level of 0.05 are marked with the same letter

Table 2. Effect of peat type, species, fertilisation treatment and their interaction on height, diameter, and biomass of birches and willows

F-value Species Characteristic Fpeat Fspecies Ffert Fpeat*fert Fpeat*species Ffert*species Fpeat*fert*species Birch Height 5.1* 1.5 54.6*** 1.7 0.0 1.0 0.3 Diameter 7.0* 3.3 22.8*** 0.9 0.1 0.5 0.7 Biomass 15.4** 0.1 95.7*** 1.3 0.3 0.7 0.3

Willow Height 7.1* 0.1 16.4*** 0.4 1.2 0.6 0.6 Diameter 7.0* 1.7 11.5*** 0.6 0.2 0.4 0.4 Biomass 1.9 2.4 16.7*** 0.6 0.1 0.3 1.1 Stars indicate statistical significance in the analysis of variance: p < 0.05 = *, p < 0.01 = **, p < 0.001 = ***. peat = peat type, fert = fertilisation treatment.

2016, Vol. 22, No. 1 (42) ISSN 2029-9230 103101 BALTIC FORESTRY WOOD ASH FERTILISATION INCREASES BIOMASS PRODUCTION /.../ J. HYTÖNEN manifold compared to unfertilised seedlings (Figure 1). In- tions. Fertilisation with wood ash increased foliar P and creasing ash application rate from 6 t ha-1 to 12 t ha-1 did K concentrations: the more the higher the ash application not affect height and diameter, but significantly decreased dose. However, at the same time ash fertilisation decreased biomass production (Figu­re 1). Increase in ash applica- foliar Mg concentrations (Figure 2, Table 3 and 4). Highest tion rate from 12 t ha-1 to 24 t ha-1 decreased significantly ash application amount (24 t ha-1) decreased significantly height, diameter and biomass of birches (Figure 1). Thus foliar Ca concentrations of birch (Table 4). There was in terms of biomass best application rate proved to be the significant peat and fertilisation interaction in the foliar smallest one used (6 t ha-1). K concentrations (Table 3). Birches growing in Aitoneva The willow species studied did not differ from each (10.0 g kg-1) peat had higher potassium foliar concentra- other significantly in their height, diameter or biomass tion than those growing in Piipsanneva (5.3 g kg-1) one. production (Table 2). However, the willows were not able to thrive in Aitoneva peat without ash fertilisation (Fig- Table 4. Effect of fertilisation treatment on foliar nutrient con- ure 1). The application of wood ash was critical for the centrations of birch and willow growth of willows in both cutaway peats (Figure 1). The Fertilisation -1 lowest ash dose, 6 t ha , yielded the best biomass produc- Species Nutrient treatment tion also for the willows. Increasing the ash dose from A0+0 A0+N A6+N A12+N A24+N 6 t ha-1 to 12 t ha-1 did not affect height or diameter, but Birch N a b a b b decreased significantly biomass production. Increase in P a a b c d -1 -1 ash application rate from 12 t ha to 24 t ha decreased K a a b c d significantly height, diameter and biomass of willows Ca a a a a b (Figure 1). Mg ab a bc bc c Foliar nutrient concentrations Downy birch had significantly higher foliar Ca (6.1 g Willow N a b b b kg-1) and Mg (3.5 g kg-1) concentrations than silver birch P a a b b -1 -1 (Ca 3.9 g kg , Mg 2.8 g kg ) (Table 3, Figure 2). There K a a b c were no differences between the birch species in their fo- Ca a ab b c liar N, P and K concentrations (Table 3). The only differ- ence in the foliar concentrations between the two peats Mg a ab bc c was in the Mg concentrations. The birch Mg concentra- Notes: Treatments that do not differ from each other according tions were higher in Aitoneva peat (3.3 g kg-1) than in to Tukey’s test at a significance level of 0.05 are marked with Piipsanneva one (3.0 g kg-1) (Table 2). Fertilisation had the same letter. In the statistical tests of willows, the treatment a significant effect on all studied foliar nutrient concentra- Ash 24+N was not included, because of small sample size.

Table 3. Effect of peat type, species, fertilisation treatment and their interaction on foliar nutrient concentrations

F-value Species Nutrient Fpeat Fspecies Ffert Fpeat*fert Fpeat*species Ffert*species Fpeat*fert*species Birch N 0.5 3.6 13.5*** 1.9 0.0 1.7 0.6 P 0.7 2.7 48.6*** 1.0 1.1 1.8 0.3 K 0.0 0.7 439.2*** 8.3** 0.3 6.8** 1.5 Ca 0.0 64.0*** 11.6*** 1.0 0.2 1.9 0.1 Mg 6.1* 22.8*** 10.7*** 3.5* 0.1 4.0* 0.3

Willow N 17.1** 50.8*** 6.9** 1.0 10.1* 3.2 0.0 P 15.1** 13.4** 11.7** 1.7 7.0* 1.5 0.0 K 5.2* 0.7 136.6*** 9.0* 0.6 1.0 1.8 Ca 1.6 0.6 17.4*** 0.1 0.1 0.8 0.0 Mg 4.9 16.8** 20.6*** 0.4 0.2 0.5 0.1 Notes: In the statistical tests of willows, the treatment Ash 24+N was not included, because of small sample size. Stars indicate sta- tistical significance in the analyses of variance: p < 0.05 = *, p < 0.01 = **, p < 0.001 = ***. peat = peat type, fert = fertilisation treatment

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Figure 2. Foliar nutrient concentrations of the birches and willows. For willows, the treatment Ash 24+N was not included, be- cause of small sample size

Nitrogen fertilisation (A0+N) and ash doses 12 t ha-1 and trations (Figure 2, Tables 3 and 4). Nitrogen fertilization 24 t ha-1 increased foliar N concentrations of birches in increased willow foliar nitrogen concentration (Table 4). comparison to unfertilised (A0+0) peat (Table 4). S. viminalis had significantly higher foliar N (36.5 Discussion g kg-1) and P (1.8 g kg-1) concentrations than S. × dasy- clados (N 25.6 g kg-1, P 1.3 g kg-1) (Table 3, Figure 2). The growth of all studied species was poor in un- Foliar N, P and K concentrations of willows were higher fertilised cutaway peat. Wood-ash application increased with Aitoneva peat (N 38.7 g kg-1, P 2.4 g kg-1, K 38.4 the biomass production of birches and willows to many g kg-1) than with Piipsanneva one (N 27.9 g kg-1, P 1.2 times the level of unfertilised peat. Increasing the ash ap- g kg-1, K 27.5 g kg-1) (Table 3). Fertilisation with wood plication amount from 6 t ha-1 to 12 t ha-1 did not increase ash increased willow foliar N, P and K concentrations sig- yield and higher application amounts even decreased bio- nificantly compared to the unfertilised control treatment, mass production. However, the application amounts to be but at the same time decreased foliar Ca and Mg concen- used in nature cannot be directly based on results from

2016, Vol. 22, No. 1 (42) ISSN 2029-9230 105103 BALTIC FORESTRY WOOD ASH FERTILISATION INCREASES BIOMASS PRODUCTION /.../ J. HYTÖNEN greenhouse studies. Recycling of wood ash could promote The more it was used, the more ash increased the soil sustainable forestry on cutaway peatland sites and signifi- pH. The good liming effect of wood ash was evident from cantly reduce the waste problem that can arise when wood the increase in soil pH by 1.3–1.5 pH units after 6 t ha-1 fuels are used for energy production. In many studies, fer- application of ash and by 2.5–3.3 pH units after fertilisa- tilisation has not been found to increase the production tion with 24 t ha-1 of ash. Similar peat pH responses to of mature birch stands (Viro 1974, Oikarinen and Pyyk- wood ash have been reported for 1–3 years from wood könen 1981, Puro 1982, Moilanen 1985). However, this ash application on cutaway peats (Kaunisto 1983, Huo- study consistent with previous research on fertilisation tari et al. 2011, Kikamägi and Ots 2010, Kikamägi et al. was shown to increase growth of young birch stands (Viro 2013, 2014). Even 10 years from application of 5 t ha-1 1974, Kaunisto 1987, Saarsalmi et al. 1992, Hytönen and of wood ash, topsoil pH was 0.9 pH units higher in a cut- Kaunisto 1999, Hytönen and Saarsalmi 2009, Hytönen away peatland area in Finland (Hytönen and Aro 2012). and Aro 2012). Ash has already been shown to increase For willow survival and growth, a pH increase was neces- the growth of planted, naturally regenerated, or seeded sary with Aitoneva peat as substrate. Both of the willow birch seedlings on cutaway peatlands after four to five species studied died when grown in Aitoneva peat without growing seasons (Kaunisto 1987, Huotari et al. 2009, Ki- fertilisation or with only nitrogen fertilisation, emphasis- kamägi et al. 2013). The effect of ash fertilisation can be ing the significance of soil pH for energy-willow culti- quite long-lasting, and positive growth results have been vation. Earlier investigations have shown that willows in measured 15–21 years from wood-ash application on bioenergy-plantation require rather high substrate pH lev- birch stands (Aro and Kaunisto 1996, Hytönen and Aro els (5.0–6.0) (Ericsson and Lindsjö 1981, Hytönen 2005). 2012). From research results with pine in peatland forests, For reaching this optimal pH range, the wood-ash dose one can expect trees to show a response to ash fertilisa- of 6 t ha-1 was adequate. However, birches do not need tion that is still much longer (e.g. Silfverberg and Huikari an increase in pH for good growth (Ericsson and Lindsjö 1985, Silfverberg 1996, Moilanen et al. 2002, 2005). 1981, Rikala and Josefek 1991, Hytönen 2005), and lim- Wood ash proved to be a good source of phospho- ing has, while in some cases increasing mostly decreased rus and potassium for both birch and willow seedlings, the growth of birches (Kaunisto 1979, 1981, 1987). significantly increasing foliar concentrations of these nu- The two unfertilized cutaway peats differed from trients. Similar results have been shown in a field study each other in their chemical characteristics: Piipsanneva in Estonia (Kikamägi et al. 2011). Mere nitrogen fertilisa- peat had higher pH, total N, and acid ammonium acetate tion increased foliar N concentration of birches. For birch, extractable Ca concentrations than Aitoneva peat. How- foliar K concentrations of seedlings grown in unfertilised ever, the growth of birches was better in Aitoneva than peat and in peat fertilised with nitrogen was at the defi- in Piipsanneva peat. Cutaway peatlands have low P and K ciency level (6–7 g kg-1, Sarjala and Kaunisto 2002), but concentration in the residual peat (Aro et al. 1997, Kika- ash fertilisation increased K concentrations and eliminat- mägi et al. 2013). Thus, the higher P (Aitoneva 12.8 mg l-1, ed deficiencies. The effect of wood ash on nutrition of Piipsanneva 6.8 mg l-1) and K concentrations in the un- birch can be long-lasting. Wood ash has been reported to fertilised Aitoneva peat, even though differences between increase foliar P, K, and B concentrations 15 years from peat types were not significant, may have reflected in the application (Aro and Kaunisto 1996) and concentration of growth results. Ash fertilisation increased soil extractable P for even 21 years (Hytönen and Aro 2012). In this study P, K, Ca, and Mg concentrations in both cutaway peats ash decreased the foliar Ca and Mg concentrations of both studied with increasing application amounts. Similar high willows and birches. In the study of Huotari et al. (2011), increases in extractable P, K, Ca, and Mg concentrations wood ash (8 t ha-1) did not affect foliar Ca concentrations have been reported in field studies from cutaway peats but increased birch Mg concentration significantly after one to three years from application (Kikamägi et al. 2013, five growing seasons, and in the study of Kikamägi et al. 2014). The effect of ash on soil nutrient stores seems to (2011) ash increased foliar Ca concentrations but did not be long-lasting; for example, Hytönen and Aro (2012) re- affect Mg concentrations. The two birch species differed ported increases in amounts of extractable nutrients (P, K, from each other in their Ca and Mg concentrations, with Ca, Mg, and B) especially in the top peat layer even 10 downy birch having higher concentrations than silver years after application of 5 t ha-1 of wood ash. Probably birch, as reported earlier in some studies (Saramäki and on account of increases in mineral matter in the soil with Hytönen 2004, Hytönen 2005, Hytönen et al. 2014). S. ash application, the largest amount of ash reduced the soil viminalis was a more demanding species than S. × dasy- total nitrogen concentrations, as shown earlier by Kika- clados, which was reflected in this study by higher foliar mägi et al. (2013, 2014) on cutaway peatlands in Estonia. N and P concentrations.

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Conclusions Huotari, N., Tillman-Sutela, E. and Kubin, E. 2011. Ground vegetation has a major role in element dynamics in an ash- fertilized cut-away peatland. Forest Ecology and Management Large areas of peat-production fields will become 261: 2081-2088. available for other uses. Cutaway peatlands often have Huotari, N., Tillman-Sutela, E., Pasanen, J. and Kubin, E. 2008. high nitrogen content in the remaining bottom peat while Ash-fertilization improves germination and early establish- concentrations of mineral nutrients are low. Wood ash ment of birch (Betula pubescens Ehrh.) seedlings on a cutaway peatland. Forest Ecology and Management 255: 2870-2875. proved to be a good source of P and K for both birch Hytönen J. 1995. Effect of fertilizer treatment on the biomass pro- and willow seedlings, also significantly increasing their duction and nutrient uptake of short-rotation willow on cut- growth. The growth of all species was poor on unfertilised away peatlands. Silva Fennica 29(1): 21-40. peat. Ash also increases soil pH, a prerequisite for ener- Hytönen J. 1996. Biomass production and nutrition of short-rota- tion plantations. The Finnish Forest Research Institute, Re- gy-willow cultivation on peatlands. The usability of ash search Papers 586, 61 pp. on cutaway peatlands is enhanced by the technical ease Hytönen, J. 2005. Effects of liming on the growth of downy and of spreading ash in treeless and level areas. Variations silver birch and willow on two cutaway peat substrates. Baltic in inherent nutrient status between cutaway peats can be Forestry 11(2):68-74. Hytönen, J. and Aro, L. 2012. Biomass and nutrition of naturally expected to be of importance for afforestation or short- regenerated and coppiced birch on cutaway peatland during 37 rotation cultivation. years. Silva Fennica 46(3): 377-394. Hytönen, J. and Kaunisto, S. 1999. Effects of fertilization on the References biomass production of coppiced mixed birch and willow stands on a cutaway peatland. Biomass and Bioenergy 17: 435-469. Hytönen, J. and Saarsalmi A. 2009. Long-term biomass produc- Āboliņa, E., Luzadis, V.A. and Lazdiņa, D. 2014. Analysis of the tion and nutrient uptake of birch, alder and willow plantations adoption of willow growing practice in Latvia. Baltic Forestry on cutaway peatland. Biomass and Bioenergy 33: 1197-1211. 20(1): 78-87. Hytönen, J., Saramäki, J. and Niemistö, P. 2014. Growth, stem Aosaar, J., Varik, M. and Uri, V. 2012. Biomass production po- quality and nutritional status of Betula pendula and Betula pu- tential of grey alder (Alnus incana (L.) Moench.) in Scandi- bescens in pure stands and mixtures. Scandinavian Journal of navia and Eastern Europe: a review. Biomass and Bioenergy Forest Research 29(1):1-11. 45: 11-26. Johansson, T. 2007. Biomass production and allometric above- and Aro, L., and Kaunisto, S. 1996. Tuhkalannoitus eräillä suonpohjien below-ground relations for young birch stands planted at four turpeilla. [Ash fertilization on some cutover peatlands.] The spacings on abandoned farmland. Forestry 80(1): 41–52. Finnish Forest Research Institute, Research Papers 593: 31- Johansson, T. 2013. Biomass production of hybrid aspen growing 41 (in Finnish). on abandonend farm land in Sweden. Journal of Forestry Re- Aro, L. and Kaunisto, S. 2003. Jatkolannoituksen ja kasvatusti- search 24(2): 237-246. heyden vaikutus nuorten mäntymetsiköiden ravinnetilaan sekä Karlsson, A., Albrektson, A. and Soneson, J. 1997. Site index and puuston ja juuriston kehitykseen paksuturpeisella suonpohjal- productivity of artificially regenerated Betula pendula and la [Effect of refertilisation and growing density on the nutri- Betula pubescens stand on former farmland in Southern and tion, growth and root development of young Scots pine stands Central Sweden. Scandinavian Journal of Forest Research in a peat cutaway area with deep peat layers.]. Suo - Mires and 12:256–263. Peat 54(2): 49-68 (in Finnish with summary in English). Kaunisto, S. 1979. Alustavia tuloksia palaturpeen kuivatuskentän ja Aro, L., Kaunisto, S. and Saarinen, M. 1997. Suopohjien metsi- suonpohjan metsityksestä [Preliminary results on afforestation tys. Hankeraportti 1986-1995 [Afforestation of peat cutaway of sod drying fields and peat cut-over areas]. Folia Forestalia areas. Project report in 1986-1995.] The Finnish Forest Re- 404: 1-14 (in Finnish with summary in English). search Institute, Research Papers 634, 51 pp. (in Finnish with Kaunisto, S. 1981. Rauduskoivun (Betula pendula) ja hieskoivun summary in English). (Betula pubescens) luontainen uudistuminen turpeennoston Ericsson, T. and Lindsjö, I. 1981. Tillväxtens pH-beroende hos jälkeisellä suonpohjan turpeella Kihniön Aitonevalla.[Natural några energiskogsarter [The influence of pH on growth and regeneration of Betula pendula and B. pubescens on a peat nutrition of some energy forestry tree species.] Projekt Ener- cutaway area]. Suo – Peatlands and Mires 32(3): 53-60 (in giskogsodling. Sveriges Lantbruksuniversitet. Teknisk rap- Finnish with summary in English). port, 11: 7 p. (in Swedish with abstract in English). Kaunisto, S. 1983. Koripajun (Salix viminlais) biomassatuotos sekä Ferm, A. 1993. Birch production and utilization for energy. Bio- ravinteiden ja veden käyttö eri tavoin lannoitetuilla turpeilla mass and Bioenergy 4(6): 391-404. kasvihuoneessa [Biomass production of Salix viminalis and its Guidi Nissim, W., Pitre, F.E., Teodorescu, T.I. and Labrecque, nutrient and water consumption on differently fertilized peats M. 2013. Long-term biomass productivity of bioenergy plan- in greenhouse]. Folia Forestalia 551: 1-34 (in Finnish with tations maintained in southern Quebec, Canada. Biomass and summary in English). Bioenergy 56(1): 361–369. Kaunisto, S. 1987. Lannoituksen ja maanmuokkauksen vaikutus Halonen, O., Tulkki, H. and Derome, J. 1983. Nutrient analysis männyn ja rauduskoivun istutustaimien kasvuun suonpohjilla methods. The Finnish Forest Research Institute, Research Pa- [Effect of fertilization and soil preparation on the development pers 121, 28 pp. of Scots pine and Silver birch plantations on peat cut-over ar- Heinsoo, K. and Dimitriou, I. 2014. Growth performance of wil- eas]. Folia Forestalia 681: 1-23 (in Finnish with summary in low clones in short rotation coppice after sewage sludge ap- English). plication. Baltic Forestry 20(1): 70-77. Kikamägi, K. and Ots, K. 2010. Puittaimede kasvu stimuleerimine Huotari, N., Tillman-Sutela, E. and Kubin, E. 2009. Ground veg- erinevate biokütuste (puit, turvas) tuha liikidega ammendatud etation exceeds tree seedlings in early biomass production and freesturbaväljal [Stimulating the growth of trees with ashes of carbon stock on an ash-fertilized cutaway peatland. Biomass various biofuels (wood, peat) on a cutaway peatland]. Forest- and Bioenergy 333: 1108-1115.

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ry Studies Metsanduslikud Uurimused 52: 60–71 (in Estonian different tree species]. Folia Forestalia 507: 1–14 (in Finnish with summary in English). with summary in English). Kikamägi, K., Kuznetsova, T. and Ots, K. 2013. Effect of wood Pučka, I and Lazdiņa, D. 2014. Review about investigations of Sa- ash on the biomass production and nutrient status of young lix spp. in Europe. Research for Rural Development 2:13 -19. silver birch (Betula pendula Roth) trees on cutaway peatlands Renou-Wilson. F., Pöllänen, M., Byrne, K., Wilson, D. and Far- in Estonia. Ecological Engineering 58:17– 25. rell, E.P. 2010. The potential of birch afforestation as an after- Kikamägi, K., Ots, K., Kuznetsova, T. and Pototski, A. 2014. The use option for industrial cutaway peatlands. Suo - Mires and growth and nutrients status of conifers on ash-treated cutaway Peat 61(3-4): 59-76. peatland. Trees-Structure and Function 28(1): 53 - 64. Rikala, R. and Jozefek, H.J. 1990. Effect of dolomite lime and Koivisto, P. 1959. Kasvu- ja tuottotaulukoita [Growth and yield wood ash on peat substrate and development of tree seedlings. tables]. Communicationes Instituti Forestalis Fenniae 51(8): Silva Fennica 24(4):323-334. 1-49 (in Finnish with summary in English). Saarela, I.1991. Wood, bark, peat and coal ashes as liming agents Maljanen, M., Liimatainen, M., Hytönen, J. and Martikainen, and sources of calcium, magnesium, potassium and phospho- P. J. 2014. The effect of granulated wood-ash fertilization on rus. Annales Agriculturae Fenniae 30(3): 375-388. soil properties and greenhouse gas (GHG) emissions in boreal Saarsalmi, A., Palmgren, K. and Levula, T. 1992. Harmaalepän peatland forests. Boreal Environmental Research 19: 295-309. ja rauduskoivun biomassan tuotos ja ravinteiden käyttö ener- Moilanen, M. 1985. Lannoituksen ja harvennuksen vaikutus hies- giapuuviljelmällä [Biomass production and nutrient consump- koivun kasvuun ohutturpeisilla ojitetuilla rämeillä [Effect tion of Alnus incana and Betula pendula in energy forestry]. of fertilization and thinning on the growth of birch (Betula Folia Forestalia 797:1–29 (in Finnish with summary in Eng- pubescens) on the drained mires with thin peatlayer]. Folia lish). Forestalia 629:1–29 (in Finnish with summary in English). Saramäki, J. and Hytönen, J. 2004. Nutritional status and devel- Moilanen, M. and Issakainen, J. 2003. Puu- ja turvetuhkien vaiku- opment of mixed plantations of silver birch (Betula pendula tus maaperään, metsäkasvillisuuden alkuainepitoisuuksiin ja Roth) and downy birch (Betula pubescens Ehrh.) on former puuston kasvuun [Effect of wood and peat ash on the element agricultural soils. Baltic Forestry 10(1):2-11. content of forest vegetation and stand growth]. Metsätehon ra- Sarjala, T. and Kaunisto, S. 2002. Potassium nutrition and free portti 162, 91pp. (in Finnish). polyamines of Betula pendula Roth and Betula pubescens Moilanen, M., Hytönen, J. and Leppälä, M. 2012. The effect of Ehrh. Plant and Soil 238:141-149.

wood ash on soil CO2 emission and carbon stock of tree stand Silfverberg, K. 1996. Nutrient status and development of tree stands on a drained peatland – case study. European Journal of Soil and vegetation on ash-fertilized drained peatlands in Finland. Science 63(4): 467-475. Finnish Forest Research Institute, Research Papers 588: 1-27. Moilanen, M., Silfverberg, K. and Hokkanen, T.J. 2002. Effects Silfverberg, K. and Hotanen, J-P. 1989. Long-term effects of of wood-ash on the tree growth, vegetation and substrate qual- wood-ash on a drained mesotrophic Sphagnum papillosum fen ity of a drained mire: a case study. Forest Ecology and Man- in Oulu district, Finland. Folia Forestalia 742: 1-23. agement 17: 321-328. Silfverberg, K. and Huikari, O. 1985. Wood-ash fertilization on Moilanen, M., Silfverberg, K., Hökkä, H. and Issakainen, J. drained peatlands. Folia Forestalia 633: 1-25. 2005. Wood ash as a fertilizer on drained mires - growth and Silfverberg, K. and Issakainen, J. 2002. Puuntuhka ja kauppalan- foliar nutrients of Scots pine. Canadian Journal of Forest Re- noitteet suomänniköiden ravinnetalouden hoidossa [Wood ash search 35(11): 2734-2742. and commercial fertilizers in fertilization of Scots pine stands Mola-Yudego, B. and González-Olabarria, J.R. 2010. Mapping in peatlands]. Metsätieteen aikakauskirja 1/2001: 29-44 (in the expansion and distribution of willow plantations for bio- Finnish). energy in Sweden: Lessons to be learned about the spread of Uri, V., Tullus, H. and Lõhmus, K. 2002. Biomass production and energy crops. Biomass and Bioenergy 34(4): 442–448. nutrient accumulation in short-rotation grey alder (Alnus in- Oikarinen, M. and Pyykkönen, J. 1981. Harvennuksen ja lan- cana (L.) Moench.) plantation on abandoned agricultural land. noituksen vaikutus turvekankaan hieskoivikon kehitykseen Forest Ecology and Management 161(1-3): 169–79. Pohjanmaalla [The effect of thinning and fertilization on the Viro, P.J. 1974. Fertilization of birch. Communicationes Instituti growth of pubescent birch (Betula pubescens) on drained Forestalis Fenniae 81(4): 1–38. myrtillus spruce swamp in Ostrobothnia]. Folia Forestalia: Ylitalo, E. 2013. Puun energiakäyttö [Energy use of wood]. Metsäti- 486:1–15 (in Finnish with abstract in English). lastotiedote 15/2013, 6 pp. (in Finnish). Pitman, R.M. 2006. Wood ash use in forestry – a review of the environmental impacts. Forestry 79: 563–586. Received 10 February 2015 Puro, T. 1982. Lannoitusajankohdan merkitys eri puulajien kas- vureaktiossa [Effect of fertilization time on growth reaction of Accepted 25 January 2016

2016, Vol. 22, No. 1 (42) ISSN 2029-9230 106108 BALTIC FORESTRY A VERSATILE TERRAIN AND ROADSIDE CHIPPER FOR ENERGY WOOD PRODUCTION /.../ N. MAGAGNOTTI ET AL. A Versatile Terrain and Roadside Chipper for Energy Wood Production in Plantation Forestry

NATASCIA MAGAGNOTTI1, RAFFAELE SPINELLI*1,2, FABIO DE FRANCESCO1 AND CAROLINA LOMBARDINI1 1 CNR IVALSA, Via Madonna del Piano 10, I-50019 Sesto Fiorentino, Italy 2 AFORA, University of the Sunshine Coast, Locked Bag 4, Maroochydore DC, QLD 4558, Australia Corresponding author: CNR IVALSA, [email protected]

Magagnotti, N., Spinelli, R.*, Francesco, F. De and Lombardini, C. 2016. A Versatile Terrain and Roadside Chip- per for Energy Wood Production in Plantation Forestry. Baltic Forestry 22(1): 107-115.

Abstract

A new industrial chipper was designed for use in short-rotation forestry plantations, which requires high productivity and all- round mobility. The new machine was tested at seven different sites, representative of the main work environments negotiated by modern agroforestry contractors. The tests produced 114 chip containers, or 929 tonnes of fresh chips (ca. 3,500 m3 of loose chips). Productivity varied between 28 and 55 tonnes of fresh chips (or 105 and 194 m3 of loose chips) per productive work hour, excluding delays. Pure chipping productivity (calculated on chipping time only) was higher and peaked at 70 tonnes of fresh chips or 242 m3 of loose chips per hour. Fuel consumption ranged from 1.38 to 2.15 litres of diesel per tonne of green chips, or from 0.39 to 0.59 litres of diesel per m3 of loose chips. Machine utilization rate varied between 69 and 83 %. Highest efficiency was reached at plant yards, due to optimum pile layout, wide space availability and easy chip discharge. Due to its remarkable off-road mobility, the new machine can restore efficiency to terrain chipping, provided that the terrain is flat and solid, the piles are duly arranged and a large enough support fleet is available for moving the chips to their destination.

Keywords: biomass; energy; poductivity; fuel consumption; quality

Introduction The increasingly important role of plantation forest- ry is also visible in Europe. On one hand, Europe still has Managed natural forests are an important source of a large forest base but struggles to exploit it and leaves wood biomass, but remote location, difficult terrain and it largely underutilized (Ericsson and Nilsson 2006). On stringent environmental constraints make forest harvest- the other hand, agroforestry is supported by the European ing especially difficult, which may result in expensive and Union with attractive grant schemes, in an attempt to in- irregular supplies (Spinelli and Magagnotti 2014). For this crease wood biomass availability and to promote rural de- reason, an increasing proportion of the global wood bio- velopment (Stupak et al. 2007). In fact, recent projections mass supply is being sourced from dedicated plantations estimate the wood biomass potential of European agricul- established on farm land (Ragauskas et al. 2006). Plan- ture to be three times as large as that of European forests tation forestry is widely acknowledged as a sustainable (EEA 2006), which partly reflects the rapid expansion of source of wood biomass, and offers a viable alternative agroforestry in recent years (De Wit and Faaij 2010). to the overexploitation of the remaining natural forests, Agroforestry plantations offer a very different work where these are threatened by industrial development or environment compared with natural forests, and min- demographic pressure (Berndes et al. 2003). Planted for- imum-cost supply may be achieved with different tech- ests are generally established with fast-growing species, niques (Spinelli and Magagnotti 2011). In particular, such as Pinus, Eucalyptus and Populus (FAO 2009). Eu- agroforestry work may revive interest in terrain chipping, calyptus and Populus are probably the best performers, which has lost much of its appeal in natural forests (Kärhä with yields in the range from 20 to 40 m3 per hectare and 2011). With terrain chipping, the wood is reached by the year (Siry et al. 2005). Eucalyptus plantations cover 18 chipper directly in the field, and is extracted to the field million hectares, and are especially popular in the South- edge after comminution (Talbot and Suadicani 2005). ern Hemisphere. Planted poplar is mainly used in the This technique maximizes the benefits of size reduction Northern Hemisphere, and covers almost 9 million hect- by placing it at the very beginning of the supply chain ares worldwide (FAO 2012). (Björheden 2008). At the same time, it allows fastest dry-

2016, Vol. 22, No. 1 (42) ISSN 2029-9230 109107 BALTIC FORESTRY A VERSATILE TERRAIN AND ROADSIDE CHIPPER FOR ENERGY WOOD PRODUCTION /.../ N. MAGAGNOTTI ET AL. ing in the open field (Civitarese et al. 2015) and minimum best possible match to the needs of agroforestry contrac- contamination during handling (Greene et al. 2014). How- tors. It was powered by a 405 kW Scania engine, meeting ever, even when it is solid and even, forest terrain hinders Euro 6 compliance requirements (European Union 2007) the access of chipping machinery and limits their size and through the exhaust gas recirculation (EGR) and selective productivity, making roadside chipping a more efficient catalytic reduction (SCR) technologies. That removed the alternative (Marchi et al. 2011). For this reason, forest need for a conventional diesel particulate filter, which gen- biomass is generally chipped at roadside, all over Europe erally represents a severe fire hazard for machines work- (Díaz-Yáñez et al. 2013). On the other hand, agroforestry ing in dusty environments. The chipper was completely plantations are much easier to access than the most acces- redesigned and featured a new 3.5 t drum, with a width of sible natural forests, and that offers a new opportunity to 1400 mm and a diameter of 820 mm. The drum was of the terrain chipping (Spinelli et al. 2014a). closed type (Spinelli et al. 2014b), but used 5 staggered Recent studies have shown that under the condi- small knives instead of the classic two full-length knives. tions of European plantation forestry, terrain chipping is Chip evacuation was obtained through a new hydrau- more efficient and less expensive than roadside chipping lic blower with adjustable speed, for meeting variable (Spinelli et al. 2012). However, these very same studies ejection distance needs and minimizing fuel consumption. expressed concerns about the mobility of adapted farm- The no-stress feeding function could also be adjusted on- ing and forestry equipment, both considered sub-optimal the-fly to match different feedstock types. The operator for terrain chipping. Apparently, there is a need for dedi- cab could be lifted and turned towards the infeed opening, cated agroforestry machinery, capable of making the best to guarantee optimum worksite visibility through its wide of the opportunities offered by these new emerging crops. polycarbonate windows. Specific machines have already been developed, such as The carrier was designed and built by Pezzolato, and a few large-size industrial chipper models, obtained from featured four large diameter wheels (1,500 mm), equipped the combination of a forestry chipper and a large farmland with versatile (on-off road) tractor tyres. Transmission carrier, typically a forager (Manzone and Spinelli 2013) or and steering were fully hydrostatic, and three different a sugar beet harvester (Mihelic et al. 2015). However, the steering modes were provided. The complete machine flexible use of these machines is hindered by a base carrier was 2.5 m wide and weighed 25,900 kg, equally distrib- that was not developed for agroforestry use. Foragers typi- uted between the two axles. The vehicle was road legal cally mount small wheels on the rear axle, which detracts and could travel on public roads up to a maximum speed from their off-road mobility and makes terrain access dif- of 40 km h-1. This was an all-round industrial chipper that ficult when the soil is rough or wet. Sugar beet harvesters could travel across the plantations, as well as relocate rap- are not designed for carrying a heavy chipper, and once idly and independently between worksites. the chipper is installed on such a carrier, total axle weight The study consisted of field trials conducted at seven exceeds the road legal limit, which requires sub-optimum different sites (Table 1). These seven test sites included a solutions for allowing road access. However, in 2015 a full range of work conditions encountered by agroforestry completely new agroforestry chipper appeared on the contractors. Feedstock type, operation setup and logistics market, which did not result from the adaptation of a farm- varied between sites, which impacted the results of indi- land carrier, but had been designed from scratch so as to vidual trials. integrate all the requirements of agroforestry operations. The seven test sites reflected a full range of work- The goals of this study were 1) to determine the per- ing environments, from the typical agroforestry (poplar) formance of the new agroforestry chipper, in terms of plantations of the region, to industrial wood yards, clas- productivity, fuel consumption and chip quality and 2) to sic mountain landings and platforms for the accumulation gauge how much chipper performance is affected by differ- of park maintenance residues at the urban interface. All ent work environments, in order to probe machine versa- the poplar plantation sites (1, 2 and 3) represented ter- tility. Although specifically designed for matching the pe- rain chipping operations on flat terrain, after the stand had culiar requirements of agroforestry operations, an efficient been clearcut, the timber had been removed and all the chipper must offer a good performance also when deployed residues bunched in piles containing approximately 2-3 under different work environments, because industrial con- fresh tonnes each. The two plant yards (sites 4 and 5) con- tractors generally manage a diversified wood basket. sisted of a large paved yard with wood neatly piled in 4-m tall stacks. Finally, the two landings (sites 6 and 7) were Materials unpaved enlargements of an unpaved road, where wood was piled in one continuous pile about 4-m tall. The new chipper analysed in this study was the Pez- All tests were conducted in June 2015 in the Piemon- zolato PTH 1400/820 Allroad (Figure 1). The machine was te region, northwestern Italy. Each field trial lasted long designed and built from scratch, in order to provide the enough to produce a minimum of 8 loads. Total study time

2016, Vol. 22, No. 1 (42) ISSN 2029-9230 108110 BALTIC FORESTRY A VERSATILE TERRAIN AND ROADSIDE CHIPPER FOR ENERGY WOOD PRODUCTION /.../ N. MAGAGNOTTI ET AL.

Figure 1. The Pezzolato Allroad at work

Table 1. Characteristics of the test sites

Site Feedstock mc % Piece mass Kg Output type Material type species Mean SD Mean SD Loads t m3

1. Poplar clearcut Tops Poplar 48.2a 2.7 70.0a 5.8 9 80.9 276 2. Poplar hill Tops Poplar 45.5a 3.6 52.9a 6.7 10 89.5 342 3. Poplar salvage Tops Poplar 39.2c 2.8 50.5a 20.2 15 108.8 479 4. Poplar yard Slabs, offcuts Poplar 41.8c 4.1 6.4b 1.3 20 106.6 500 5. Chestnut yard 2m logs Chestnut 47.3a 2.8 72.0a 12.3 40 284.5 1000 6. Mountain operation Tops Chestnut, pine 31.6b 2.4 49.6a 23.5 8 100.4 374 7. Pruning residues Slash Garden trees/shrubs 39.4c 5.5 21.2a 5.0 12 158.7 522

Total 114 929.4 3493

Average 43.2 5.8 42.9 25.4 Notes: mc = moisture content (or water mass fraction); SD = Standard deviation; m3 = bulk volume of loose chips; Chestnut = Castanea sativa L.; Pinus = Pinus strobus L.; Poplar = Populus ×Euroamericana; Garden trees/shrubs = Cupressus sp., Pinus sp., Laurus nobilis L., Magnolia grandiflora L. etc. Different superscript letters along the same column indicate statistically significant differences between treatments (sites) for α = 0.05, according to Scheffe’s post-hoc test. amounted to 35.4 hours, including mechanical, person- Methods nel and operational delays but excluding local transfers and study delays. During the study, the chipper produced The authors carried out a typical time-and-motion 114 containers, amounting to 3,493 m3 loose chips or 929 study, designed to evaluate machine productivity and to tonnes of fresh chips (mean moisture content = 42.6%). The identify those variables that are most likely to affect it mean bulk density of the fresh chips was 266 kg m-3. The (Magagnotti et al. 2013). Each work cycle was timed in- machine was operated by the same driver, a well-trained, dividually, using hand-held field computers, running dedi- experienced and efficient professional, who was very pro- cated time study software. Productive time was separated ficient with his job and equipment. He had about 5 years of from delay time, but excessive further detail was avoided experience with the industrial chippers built by the same in order to contain error and guarantee repeatability of the manufacturer. The same 35 mm cut length adjustment and experiment (Spinelli et al. 2013). Productive time was di- 100 × 100 mm square-mesh screen were used for all trials. vided between chipping work proper and other work (e.g.

2016, Vol. 22, No. 1 (42) ISSN 2029-9230 111109 BALTIC FORESTRY A VERSATILE TERRAIN AND ROADSIDE CHIPPER FOR ENERGY WOOD PRODUCTION /.../ N. MAGAGNOTTI ET AL. moving the chipper along the piles, parking the container Tukey-Kramer test, which is especially suited to handle by the chipper and loader work other than chipper feed- unbalanced datasets and is relatively powerful. In contrast, ing). The filling of a chip container was considered as one heteroscedastic data were handled with non-parametric and cycle. All delays were included in the study, and not just post-hoc tests, robust to violations of statistical assump- the delays below a set duration threshold, because such tions, although less powerful than the Tukey-Karmer’s test. practice may misrepresent the incidence of downtime In particular, the Kruskal-Wallis test was used for checking (Spinelli and Visser 2008). However, delays caused by the the presence of statistically significant differences between study itself were removed from the data set. groups, and the Scheffe’s post-hoc test for pinning such dif- Total volume output was estimated by measuring the ferences onto specific groups. Both such tests are suitable internal volume of all containers and visually assessing the for data sets flawed by unequal numbers of observations, volume of any mounds or voids on the container top. Total non-normal distribution of data and heteroscedasticity mass output was determined by taking all loads to a certified (SAS 1999). The significance of any relationships between weighbridge at the load reception site, a local wood-fired productivity and piece size was tested with regression anal- power station. Piece size (i.e the size of the individual wood ysis. In that case, compliance with the statistical assump- element - log, top or branch - inserted into the chipper) was tions was checked through the analysis of the residuals. determined by dividing the mass of each load by the count of wood elements inserted into the chipper when produc- Results ing that load. Two 500 g samples were collected from each container load in order to determine moisture mass frac- The feedstock stored at the different worksites dif- tion and particle size distribution. Each 500 g sample was fered for type, size and moisture content (Table 1). Tops obtained after reduction of a larger sample assembled by were chipped at all agroforestry plantations sites and at mixing subsamples collected at different points from the the forest landing, whereas sawmill residues (slabs and container top. Moisture mass fraction was determined with offcuts) and logs were chipped at the two industrial yards. the gravimetric method, according to European standards However, the sawmill residues handled at the poplar yard (CEN 2009). Fresh weight was determined on-site with a were significantly smaller (ca. 6 kg apiece) than the logs portable scale, immediately after sample collection. Par- at the chestnut yard, and than any other feedstock types ticle size distribution was determined with the oscillating used for the trials, except for the pruning residues that screen method using four sieves to separate the sample into consisted of branches. With a water mass fraction of 31 %, five chip length classes: > 63 mm (oversize particles), 63- tops stacked at the mountain landing were significantly 46 mm (large-size chips), 45-17 mm (medium-size chips), drier than any other feedstock used for the trials, as the 16-3 mm (small-size chips), < 3 mm (fines). Each fraction result of their longer storage time. Freshly cut poplar and was then weighed with a precision scale (0.1 g). For the chestnut were significantly wetter than the rest (45 to 48 purpose of the analysis, particle size data was consolidated % moisture content), except for the diseased poplars com- into three functional classes: oversized (> 63 mm), accepts ing from the salvage operations, where a high proportion (63-3 mm) and fines (< 3 mm). of standing deadwood contributed to decrease mean mois- Fuel consumption was measured by parking the chip- ture content. The moisture content of freshly-cut salvaged per on the same level spot and filling the diesel tank with poplar (39 %) did not differ significantly from that of saw- a fuel pump accurate to 0.1 dm3, before starting and after mill and pruning residues (42 % and 39 %, respectively). completing each test. The fuel tank, pump and meter were Mechanical availability was 94 %, as could be ex- loaded on a pick-up truck that followed the chipper to the pected for a new machine. A large proportion of mechani- work site. Fuel consumption was the gross fuel consump- cal delays consisted of knife replacement. Mean machine tion for the chipper and the loader, since both were pow- utilization rate was 77 % and ranged from 69 to 83 %, ered by the same engine. due to the effect of all delays combined (Figure 2). Uti- The dataset was analyzed with the Minitab 16 and lization was the lowest in the mountain operation, as the Statview advanced statistics softwares, in order to check the result of landing space constraints and irregular chip truck statistical significance of eventual trends. Before analysis, flow - both related to the typical accessibility constraints the data was tested for normality using Ryan-Noyer’s test. of mountain landings (Spinelli et al. 2014c). The propor- Non-normal distributions were normalized using transfor- tion of accessory work to net work time was significantly mations. In particular, the arcsine transformation was used lower at both the chestnut and the poplar yards than at the for the percent efficiency data, and the logit transformation other sites, as a result of an easier working environment in for the percent particle size data; the latter already used in terms of larger and more orderly stacks, and wider space the same application by Eliasson et al. (2015). The data- for manoeuvring. Actual chipping time represented be- set was then checked for homoscedasticity using Bartlett’s tween 55 and 80 % of total worksite time, with the highest test. Normal, homoscedastic data were tested using the figures being recorded again at the plant yards.

2016, Vol. 22, No. 1 (42) ISSN 2029-9230 110112 BALTIC FORESTRY A VERSATILE TERRAIN AND ROADSIDE CHIPPER FOR ENERGY WOOD PRODUCTION /.../ N. MAGAGNOTTI ET AL.

Figure 2. Breakdown of worksite time by activity Note: Other work = moving the chipper along the piles, parking the container by the chipper and loader work other than chipper feeding

Total worksite productivity (inclusive of delays) varied the best performance was reached at the chestnut yard, between 19 and 44 fresh tonnes per scheduled hour, or be- where productivity reached the peak values of 70 tonnes tween 72 and 156 m3 loose chips per scheduled hour (Table and 242 m3 per hour. Expressing productivity in volume 2). Expressed as fresh weight, gross productivity was clearly rather than weight increased the resolution of the analysis, stratified: highest at the chestnut yard, lowest at the moun- by removing the confounding effect of variable moisture tain landing and intermediate in between. These differ- content. Chipping productivity had a positive but relative- ences were statistically significant. When productivity was ly weak correlation (R2 = 0.10) with piece size. However, expressed as loose volume the same pattern repeated, but when the yard data were removed from the analysis, cor- further divisions appeared within the intermediate stratum. relation improved remarkably (R2 = 0.33). Pure chipping productivity was calculated on the ba- Specific fuel consumption varied between 1.38 and sis of chipping time only, excluding other work time and 2.15 litres of diesel per fresh tonne, or between 0.30 and delays, and ranged from 28 to 55 tonnes per hour, or from 0.59 litres per m3 of loose volume. Fuel consumption fig- 104 and 194 m3 loose chips per hour (Table 2). Again, ures seemed to follow productivity trends, and were low-

Table 2. Productivity of the chipper at the seven test sites

Total worksite productivity Pure chipping productivity Site t SMH-1 m3 SMH-1 t h-1 m3 h-1 type n Mean SD Mean SD Mean SD Mean SD

1. Poplar clearcut 9 28.7c 2.7 99.2bc 13.2 35.9bc 3.4 124.2bcd 16.5 2. Poplar hill 10 30.7c 3.5 118.5cd 12.7 37.8bc 4.3 146.1cd 15.7 3. Poplar salvage 15 25.4c 5.6 112.5c 24.8 34.3c 7.6 151.8cd 33.5 4. Poplar yard 20 28.3c 3.9 133.1d 18.1 36.9c 5.1 173.7ad 23.6 5. Chestnut yard 40 44.3a 4.9 155.7a 14.8 55.1a 6.1 193.6a 18.4 6. Mountain operation 8 19.4b 2.7 72.2b 9.1 28.2b 3.9 105.2b 13.2 7. Pruning residues 12 26.2c 3.6 86.5b 13.4 31.6bc 4.3 104.2b 16.1 Average 32.9 9.7 125.2 32.1 41.8 11.5 159.4 39.1 Post-hoc test Tukey-Kramer Scheffe Tukey-Kramer Scheffe Notes: SMH = Scheduled Machine Hour, inclusive of delays; m3 = bulk volume of loose chips; SD = Standard deviation; Differ- ent superscript letters along the same column indicate statistically significant differences between treatments (sites) for α = 0.05. Tukey-Kramer’s post-hoc test was used for normally-distributed homoscedastic data, whereas Scheffe’s test was used for normal- ly-distributed heteroscedastic data.

2016, Vol. 22, No. 1 (42) ISSN 2029-9230 113111 BALTIC FORESTRY A VERSATILE TERRAIN AND ROADSIDE CHIPPER FOR ENERGY WOOD PRODUCTION /.../ N. MAGAGNOTTI ET AL. est when productivity was highest. However, differences in fuel consumption were not tested for statistical signifi- cance, because there were no replications within the treat- ments. The chipper tank was filled only twice per test: be- fore the test started and right after it ended. The tank was not refilled for each container load, because the amount of diesel used for producing a single chip load was too small for obtaining accurate enough fuel use figures when the tank-refill technique was used. Therefore, any statements regarding the differences in fuel consumption between treatments cannot be taken as conclusive. Chip quality closely related with feedstock type. The proportion of accepts ranged from 72 % to 92 % of total sample weight (Table 4). It was the highest for fresh pop- lar tops and the lowest for pruning residues. The reverse was true for the incidence of oversized particles, which were the highest for pruning residues and the lowest for fresh poplar tops. In general, the incidence of oversized particles was relatively high for short (sawmill residues) or branchy materials (pruning residues and tree tops). The box-plots in Figure 3 also show a neat stratification for

Table 3. Diesel fuel consumption per product unit

Site Fuel use type l t-1 l m-3

1. Poplar clearcut 1.67 0.49 2. Poplar hill 1.84 0.48 3. Poplar salvage 1.70 0.39 4. Poplar yard 1.43 0.30 5. Chestnut yard 1.38 0.39 6. Mountain operation 2.15 0.58 7. Pruning residues 1.95 0.59 Average 1.67 0.45

3 m = bulk volume of loose chips Figure 3. Box-plot of logit-transformed particle size distributions Table 4. Particle-size distribution of wood chips

Site Oversize, % Accepts, % Fines, % type n Mean SD Mean SD Mean SD

1. Poplar clearcut 9 1.1c 1.2 92.4ac 1.8 6.5c 1.8 2. Poplar hill 10 5.9b 3.7 86.0abc 6.1 8.1bc 3.5 3. Poplar salvage 15 5.9a 5.4 86.2ac 5.2 7.9bc 2.5 4. Poplar yard 20 15.7d 8.1 81.1bd 7.8 3.2a 1.4 5. Chestnut yard 40 5.9a 4.6 90.5a 15.0 3.6a 1.9 6. Mountain operation 8 10.8bd 5.6 82.1bd 4.0 7.1bc 3.4 7. Pruning residues 12 11.9a 6.7 72.4a 8.2 15.7d 5.9 Average 8.2 6.9 84.6 11.4 6.2 4.7 Post-hoc test Tukey-Kramer Scheffe Tukey-Kramer Notes: Oversize = particle length > 63 mm; Accepts = particle length 63-3 mm; Fines = particle length <3 mm; SD = Standard de- viation; Different superscript letters along the same column indicate statistically significant differences between treatments (sites) for α = 0.05. Tukey-Kramer’s post-hoc test was used for normally-distributed homoscedastic data, whereas Scheffe’s test was used for normally-distributed heteroscedastic data

2016, Vol. 22, No. 1 (42) ISSN 2029-9230 112114 BALTIC FORESTRY A VERSATILE TERRAIN AND ROADSIDE CHIPPER FOR ENERGY WOOD PRODUCTION /.../ N. MAGAGNOTTI ET AL. what concerns the incidence of fines, with pruning resi- of chip transports had been detached to support the chip- dues at the top, yard operations at the bottom and tops per and the tops had been bunched before chipping, so in between. That may indicate a relationship between the that interaction delays were minimized and productivity incidence of fine and the proportion of foliage in the feed- was maximized. Even so, if the machine had struggled stock. Yard feedstocks contained no leaves, while pruning manoeuvring or it had bogged down, overall efficiency residues included the largest proportion of foliage. Tops would have dropped significantly. That was certainly not had a significant foliage component, but also included a the case. In fact, the chipper was even used to boost a much larger stem portion than pruning residues. slipping tractor, when its trailer was so full that it could not drive up a ramp. In turn, restoring financial viability to Discussion terrain chipping would allow solving a number of practi- cal problems, including the need for a suitable space by The trial sites represented a wide variety of working the roadside for storing the biomass. Once chipped and environments and allowed testing the new machine under loaded on a trailer, the product can be moved more ef- the conditions offered by terrain chipping, roadside chip- ficiently, and it can be taken to a terminal or to the user ping and yard chipping. In no case the incidence of delays plant, when this is located nearby. Terrain chipping does exceeded 30 %, which is the benchmark reported for con- not avoid extraction and stacking, but makes them more ventional chipping operations in Italy (Spinelli and Visser efficient. 2009). Utilization and productivity were the highest when The new machine also fares well in terms of produc- working at a yard, regardless of feedstock type (chestnut tion potential, when compared with similar units currently logs or sawmill residues). Neat stack arrangement facili- available on the market (Table 5). Net chipping productiv- tated regular feeding, while quick trailer turnover allowed ity is about 20% higher than recorded for an agroforestry minimizing interaction delays. In contrast, utilization was chipper obtained from the conversion of a powerful for- the lowest and delays were the highest when working at ager, and used for chipping the same feedstock (Manzone a mountain landing, due to the access constraints typi- and Spinelli 2013). The productivity of the new machine cal for mountain sites, eventually resulting in extended is on par with that recorded for the Silvator 2000, its most manoeuvres and irregular chip van turn out. In this re- direct competitor in terms of size class and general design. spect, the most noteworthy result is the high efficiency In this respect, it is worth mentioning that the new Pez- achieved in the terrain chipping operations, which demon- zolato chipper is almost twice as heavy as the modified strates the success of the new design. The machine moved forager, and about 20% lighter than the Silvator, which easily across the plantations, matching the performance the manufacturer considers as a good balance between of forwarder-mounted units while maintaining indepen- strength and agility. dent relocation capacity. In contrast, forwarder-mounted As a family of machines, the new agroforestry chip- chippers need to be moved around on low-bed trucks, pers seem to have a higher productive and fuel efficiency because they are too slow for independent relocation on than conventional forestry chippers despite the fact that any distances longer than few kilometres, and they are two of the forestry chippers – the Erjo and the Jenz – were not road-legal in most European countries. Of course, the fed by a separate loader powered independently, whereas good results achieved with terrain chipping was not the all other chippers featured integral loaders powered by the exclusive merit of machine mobility and productivity, but same engine as the chipper. Of course, the data in Table arose from good organisation as well. A sufficient number 5 must be interpreted with much caution, because they

Table 5. Performance comparisons

Machine characteristics Productivity Fuel Reference Make Model kW m3 h-1 t h-1 l m-3 l t-1 Study Agroforestry Pezzolato AllRoad 405 105-195 28-55 0.39-0.59 1.3-2.1 Current study Albach Silvator 450 161-180 38-56 0.43-0.68 1.0-2.3 Mihelic et al. 2015 Pezzolato Forager 409 100-110 25-30 0.48-0.55 1.6-1.8 Manzone and Spinelli 2013 Forestry Pezzolato Chippertruck 400 69-97 22-28 0.55-0.76 1.8-2.8 Spinelli et al. 2015 Erjo 12/90 430 67-94 20-28 0.39-0.50 1.3-1.7 Marchi et al. 2011 Jenz 561 HEM 335 113-174 33-51 0.50-0.62 1.7-2.1 Spinelli et al. 2012

Notes: all studies were joined by the same principal investigators, which assured consistent methodology; the Erjo and Jenz units were fed by a separate loader, whereas the other units featured integrated loaders powered by the same engine as the chipper

2016, Vol. 22, No. 1 (42) ISSN 2029-9230 115113 BALTIC FORESTRY A VERSATILE TERRAIN AND ROADSIDE CHIPPER FOR ENERGY WOOD PRODUCTION /.../ N. MAGAGNOTTI ET AL. come from separate studies, and not from a single com- cause drier fuels will produce artificially low production parative study conducted under controlled conditions. For figures. In that respect, volume estimates are somewhat this reason, different work conditions and operator profi- fairer, but they may underestimate the additional effort ciency may account for part of the differences despite the made with wetter and heavier feedstock, and the result- use of similar feedstock types and experienced operators ing higher fuel consumption. In general, it is advisable to in all studies. Furthermore, all studies mentioned in Table use both measurements in conjunction, because use of a 5 were conducted or participated by the same principal single reference unit may not tell the whole story. investigators, which guarantees methodological consis- tency and facilitates comparisons. Conclusions This study also confirms the important relationship between productivity and piece size, as well as the capac- The new chipper can reach a very high productiv- ity of other factors to confound it. Piece shape, pile ar- ity, when deployed under the appropriate conditions. Its rangement and chipping site do have their own additional main advantage is that of bringing a full-scale industrial influence, as already demonstrated by previous studies operation directly to the stump site. This operation can (Spinelli and Hartsough 2001, Spinelli and Magagnotti release its full production potential if the biomass is duly 2010, Spinelli et al. 2015). The results obtained from site prepared, and a large enough support fleet is tasked with 4 can be taken as an example: there, the better handling moving the chips to their destination. One of the most im- quality of regularly-shaped tightly-packed slabs and the portant characteristics of the new chipper is the capacity favourable work space offered by an industrial yard ex- to combine the off-road mobility of a forwarder-mounted plained a very high productivity, despite the extremely unit with the road capability of a truck-mounted machine, small piece size. although its maximum speed is substantially lower than Chip quality is generally good, and shows the ex- that of a truck. Fortunately, this is not a serious problem, pected relationship with feedstock type. The highest unless relocation distances are particularly long: that is proportion of oversized particles occurred with sawmill rarely the case in plantation forestry, and generally in ru- and pruning residues. The former offered a multitude of ral areas. The combination of favourable terrain and dedi- small, short and brittle pieces that could easily turn side- cated chippers may restore profitability to terrain chip- ways when engaged by the chipper drum and produce ping, when deployed in plantation forests. As the surface long splinters; the latter contained a high proportion of of fast-growing plantations expands, these new chippers thin flexible twigs that could occasionally bend rather may become increasingly popular. than cut, and pass through the drum as long sticks. The same dynamics may explain the large proportion of over- Acknowledgements sized particles found in chips produced from forestry tops, which were also rich with small branches (Spinelli and The research led to these results has received sup- Hartsough 2001). port from the Regione Piemonte within the scope of proj- The incidence of fines seems to be directly propor- ect MCV2, and was funded with EU structural funds (PSR tional to the amount of foliage, being the highest with 2007-2013, Misura 124.2). The authors wish to thank Ser- pruning residues (maximum incidence of foliage) and the gio Cottura (Mombracco Energy Srl) and Daniele Berto- lowest with sawmill residues and logs (no foliage at all). glio (Pezzolato SpA) for their assistance with the trials. This relationship has already been reported in many pre- vious studies (Saudicani and Gamborg 1999, Nati et al. References 2010, Spinelli et al. 2011, Spinelli et al. 2015). Again, unit choice confirms its strong effect on pro- Berndes, G., Hoogwijk, M. and Van den Broek, R. 2003. The ductivity estimates (Spinelli et al. 2015). Direct measure- contribution of biomass in the future global Energy supply: a review of 17 studies. Biomass and Bioenergy 25: 1-28. ment of chipper output is only made in fresh weight (green Björheden, R. 2008. Optimal point of comminution in the biomass tonnes) or bulk volume (m3 loose chips): dry weight and supply chain. Proceedings of the Nordic-Baltic Conference on heating value are artificial figures that are extremely use- Forest Operations, Copenhagen 23-25 September 2008. Dan- ful for a correct evaluation of fuel production cost, but ish Forest and Lanscape, Copenhagen, Denmark. CEN 2009. CEN/TS 14774-2 Solid biofuels - Determination of much less valuable for estimating machine performance moisture content - Oven dry method - Part 2: Total moisture - in a typical engineering study. A chipper does not move Simplified method. Comité Européen de Normalisation, Brux- oven-dry tonnes or kilowatt hours: it moves an actual elles. 7 pp. fresh mass and bulk volume. Which of these two ones is Civitarese, V., Spinelli, R., Barontini, M., Gallucci, F. and Pari, L. 2015. Open-air drying of cut and windrowed short-rota- chosen for evaluating machine productivity, has a strong tion poplar stems. Bioenergy Research On-line first 10.1007/ effect on the results of the evaluation itself. Fresh weight s12155-015-9612-3. estimates may be biased by different moisture content, be- De Wit, M. and Faaij, A. 2010. European biomass resource poten- tial and cost. Biomass and Bioenergy 34: 188-202.

2016, Vol. 22, No. 1 (42) ISSN 2029-9230 114116 BALTIC FORESTRY A VERSATILE TERRAIN AND ROADSIDE CHIPPER FOR ENERGY WOOD PRODUCTION /.../ N. MAGAGNOTTI ET AL.

Díaz-Yáñez, O., Mola-Yudego, B., Anttila, P., Röser, D. and Asi- Spinelli, R., De Francesco, F., Eliasson, L., Jessup, E. and Mag- kainen, A. 2013. Forest chips for energy in Europe: current agnotti, N. 2015. An agile chipper truck for space-constrained procurement methods and potentials. Renewable and Sustain- operations. Biomass and Bioenergy 81: 137-43. able Energy Reviews 21: 562–71. Spinelli, R., Brown, M., Giles, R., Huxtable, D., Laina, R. and EEA 2006. How much bioenergy can Europe produce without harm- Magagnotti, N. 2014a. Harvesting alternatives for Mallee ing the environment? Report n° 7/2006. 72 pp. agroforestry plantations in Western Australia. Agrofororestry Eliasson, L., Von Hofsten, H., Johannesson, T., Spinelli, R. and Systems 88: 479-87. Tierfelder, T. 2015. Effects of sieve size on chipper productiv- Spinelli, R., Cavallo, E., Eliasson, L., Facello, A. and Magag- ity, fuel consumption and chip size distribution for open drum notti, N. 2014b. The effect of drum design on chipper perfor- chippers. Croatian Journal of Forest Engineering 36: 11-17. mance. Renewable Energy 81: 57-61. Ericsson, K. and Nilsson, L. 2006. Assessment of the potential Spinelli, R., Di Gironimo, G., Esposito, G. and Magagnotti, N. biomass supply in Europe using a resource-focused approach. 2014c. Alternative supply chains for logging residues under Biomass and Bioenergy 30: 1-15. access constraints. Scandinavian Journal of Forest Research European Union 2007. Regulation (EC) No 715/2007 of the Euro- 29: 266-74. pean Parliament and of the Council of 20 June 2007 on type Spinelli, R., Laina-Relaño, R., Magagnotti, N. and Tolosana, E. approval of motor vehicles with respect to emissions from 2013. Determining observer and method effects on the ac- light passenger and commercial vehicles (Euro 5 and Euro 6) curacy of elemental time studies in forest operations. Baltic and on access to vehicle repair and maintenance information Forestry 19: 301-6. (Text with EEA relevance). Official Journal of the European Spinelli, R. and Hartsough, B. 2001. A survey of Italian chipping Union L 171: 1-16. operations. Biomass and Bioenergy 21: 433-44. FAO 2009. Responsible management of planted forests: Voluntary Spinelli, R. and Magagnotti, N. 2010. A tool for productivity and guidelines – Preparation for action – the country level meth- cost forecasting of decentralised wood chipping. Forest Policy odology. Planted Forests and Tree Working Paper 45/E, FAO, and Economics 12: 194-8. Rome. Spinelli, R. and Magagnotti, N. 2011. Strategies for the processing FAO 2012. Improving lives with poplars and willows. Working Pa- of tree tops from hybrid poplar plantations. Baltic Forestry per IPC 12/E, FAO, Rome, 104 pp. 17: 50-7. Greene, D., Cutshall, J., Dukes, C. and Baker, S. 2014. Improv- Spinelli, R., Magagnotti, N., Paletto, G. and Preti, C. 2011. De- ing Woody Biomass Feedstock Logistics by Reducing Ash and termining the impact of some wood characteristics on the per- Moisture Content. Bioenergy Research 7(3): 816-23. formance of a mobile chipper. Silva Fennica 45: 85-95. Kärhä, K. 2011. Industrial supply chains and production machinery Spinelli, R. and Magagnotti, N. 2014. Determining long-term of forest chips in Finland. Biomass and Bioenergy 35: 3404- chipper usage, productivity and fuel consumption. Biomass 13. and Bioenergy 66: 442-9. Magagnotti, N., Kanzian, C., Schulmeyer, F. and Spinelli, R. Spinelli, R., Schweier, J. and De Francesco, F. 2012. Harvesting 2013. A new guide for work studies in forestry. International techniques for non-industrial forestry plantations. Biosystems Journal of Forest Engineering 24: 249-53. Engineering 113: 319-24. Marchi, E., Magagnotti, N., Berretti, L., Neri, L. and Spinelli, R. Spinelli, R. and Visser, R. 2008. Analyzing and estimating delays 2011. Comparing terrain and roadside chipping in Mediterra- in harvester operations. International Journal of Forest Engi- nean pine salvage cuts. Croatian Journal of Forest Engineer- neering 19: 35-40. ing 32: 587-98. Spinelli, R. and Visser, R. 2009. Analyzing and estimating delays Manzone, M. and Spinelli, R. 2013. Wood chipping performance in wood chipping operations. Biomass and Bioenergy 33: 429- of a modified forager. Biomass and Bioenergy 55: 101-6. 33. Mihelic, M., Spinelli, R., Magagnotti, N. and Poje, A. 2015. Per- Stupak, A., Asikainen, A., Jonsel, M., Karltun, E. and Lunnan, formance of a new industrial chipper for rural contractors. A. et al. 2007. Sustainable utilisation of forest biomass for Biomass and Bioenergy 83: 152-158. energy—Possibilities and problems: Policy, legislation, certi- Nati, C., Spinelli, R. and Fabbri, P. 2010. Wood chips size distri- fication, and recommendations and guidelines in the Nordic, bution in relation to blade wear and screen use. Biomass and Baltic, and other European countries. Biomass and Bioenergy Bioenergy 34: 583–7. 31: 666-84. Ragauskas, A., Williams, C., Davison, B., Britovsek, G., Cairney, Suadicani, K. and Gamborg, C. 1999. Fuel quality of chips from J., Eckert, C., Frederick, W. Jr., Hallett, J., Leak, D., Liot- freshly felled and summer dried Norway spruce on a poor ta, C., Mielenz, J., Murphy, R., Templer, R. and Tschaplin- sandy soil and a rich loamy soil. Biomass and Bioenergy 17: ski, T. 2006. The Path Forward for Biofuels and Biomaterials 199-208. Science 311: 484-9. Talbot, B. and Suadicani, K. 2005. Analysis of two simulated in- SAS 1999. StatView Reference. Cary (NC): SAS Publishing. field chipping and extraction systems in spruce thinnings.Bio - Siry, J., Cubbage, F. and Ahmed, M. 2005. Sustainable forest systems Engineering 91: 283-92. management: global trends and opportunities. Forest Policy and Economics 7: 551-61. Received 30 October 2015 Accepted 25 February 2016

2016, Vol. 22, No. 1 (42) ISSN 2029-9230 117115 BALTIC FORESTRY PRODUCTIVITY OF MULTI-TREE CUTTING IN THINNINGS /.../ J. LAITILA ET AL. Productivity of Multi-Tree Cutting in Thinnings and Clear Cuttings of Young Downy Birch (Betula pubescens) Dominated Stands in the Integrated Harvesting of Pulpwood and Energy Wood

JUHA LAITILA*, PENTTI NIEMISTÖ AND KARI VÄÄTÄINEN Natural Resources Institute Finland Yliopistokatu 6, FI-80101 Joensuu, Finland *[email protected]

Laitila*, J., Niemistö, P and Väätäinen, K. 2016. Productivity of Multi-Tree Cutting in Thinnings and Clear Cuttings of Young Downy Birch (Betula pubescens) Dominated Stands in the Integrated Harvesting of Pulpwood and Energy Wood. Baltic Forestry 22(1): 116-131.

Abstract

The purpose of this study was to determine the productivity of multi-tree cutting of pulpwood and energy wood in thinnings and clear cuttings of young downy birch (Betula pubescens) dominated stands, along with the time consumption of cutting work phases performed with a medium-sized harvester. On the basis of the time study data collected, tree-specific time consumption and productiv- ity models were prepared for the multi-tree cutting of pulpwood and energy wood in both thinnings and clear cuttings. In the multi-tree cutting time consumption model, productivity was explained in terms of tree volume (dm3) and harvesting intensity (number of trees 3 removed per hectare). Productivity was expressed in solid cubic metres per effective hour (m /E0h). Harvested assortments in the inte- grated harvesting included pulpwood with lengths of 3–5 m and energy wood, which consisted of undelimbed tops of pulpwood stems and undersized trees. As expected, clear cutting enhanced harvesting productivity in comparison with thinning, but multi-tree cutting had only a minor effect on productivity in the case of both harvesting methods due to the low share of multi-tree cutting. In the time study sample plots, 3 the values recorded for multi-tree cutting productivity per effective hour varied between 5.6–17.4 m /E0h in clear cuttings and 4.8–10.9 3 m /E0h in thinnings, respectively. On average, the harvester head processed 1.2 trees per grapple cycle in clear cutting and 1.1 trees per grapple cycle in thinnings. The study highlighted the need to improve the suitability of current harvesting equipment for the harvesting and multi-tree har- vesting of birch and other trees with bent and crooked stems. This is because harvesting conditions that are more favourable to clear cutting than thinning are the main factors behind the observed leap in productivity: 1) The tree-specific moving time shortened when more trees could be harvested at the same spot than during thinning; 2) The removal of trees was systematic in clear cutting whereas it was selective in thinning; 3) In clear cutting, the remaining tree stand did not hamper the delimbing, cutting or piling of trees.

Key words: Multi-tree cutting, integrated harvesting, peatlands, downy birch, first thinning, clear cutting, pulpwood, coppice forests

Introduction hectares (Niemistö and Korhonen 2008). Downy birch growing on peatlands and wet mineral soils produces rath- Downy birch resources and cultivation options in er low quality timber that is often inappropriate for veneer Finland or sawing purposes, but it is important raw material for Downy birch (Betula pubescens) is the most com- the pulp and paper industries and as a fuel. For example, mon broad-leaved tree species in Finland. According to in 2012, Finnish pulp and paper industries consumed 11.7 the results of the Finnish National Forest Inventory, the million m3 of hardwood (mainly birch), of which 4.1 mil- growing stock volume of downy birch in Finnish forests lion m3 was imported (Anon. 2013). is 250 million solid cubic metres (m3), which accounts for In traditional pulpwood production, tending to a 12 % of the total growing stock (Niemistö and Korhonen density of 2,500 seedlings per hectare has been recom- 2008). The growing stock volume of forests dominated by mended for pure and clearly birch-dominant downy birch downy birch, where downy birch accounts for more than stands and commercial first thinning to a density of 1,100 50 % of the volume, is 82 million m3 and 1.15 million trees per hectare (Niemistö 1991). In pulpwood produc-

2016, Vol. 22, No. 1 (42) ISSN 2029-9230 116118 BALTIC FORESTRY PRODUCTIVITY OF MULTI-TREE CUTTING IN THINNINGS /.../ J. LAITILA ET AL. tion, the rotation period of a downy birch-dominated et al. 2011, Picchio et al. 2012, Suchomel et al. 2011, Di stand is approximately 50 years. The thinning reaction of Fulvio et al. 2012, Suchomel et al. 2012). Correspond- downy birch promoting diameter growth has been found ingly, pure Scots pine or conifer-dominant mixture for- to be weaker than that of other tree species, especially ests have been used in the study of integrated harvesting in peatlands (Niemistö 2013). Downy birch also tolerates of pulpwood and energy wood (Jylhä and Laitila 2007, shading better than silver birch (Betula pendula) (Atkin- Spinelli and Maganotti 2010, Nuutinen et al. 2011, Kärhä son 1984, Ferm 1990). The maximum number of trees 2011, Lehtimäki and Nurmi 2011, Laitila and Väätäinen per hectare that can be grown to the size of pulpwood in 2013a, Laitila and Väätäinen 2013b, Sirén et al. 2013b, downy birch-dominated stands is 2,500-3,000, and even Di Fulvio and Bergstöm 2013). Time consumption func- in the very dense downy birch stands, the significant natu- tions for multi-tree cutting in thinnings and clear cuttings ral drain of pulpwood-sized trees will appear only after of young downy birch-dominated stands in the integrated the age of 40 years (Niemistö 1991, Niemistö 2013). harvesting of pulpwood and energy wood have not been The increase in the value of and demand for energy previously determined in Finland or in any other country. wood has brought about a new and attractive option in In order to update the above-mentioned silvicultural the silvicultural management of downy birch stands: a and economic analyses of downy birch-dominated for- dense downy birch stand is grown without any tending of ests (Niemistö 2013), Natural Resources Institute Finland seedling stands and commercial thinnings for regenera- studied the integrated harvesting of pulpwood and energy tion felling. Final felling with the integrated harvesting wood. Cutting was based on a two-pile cutting method, method is carried out at the age of approximately 40 years where pulpwood and energy wood fractions are stacked to exclusively produce energy wood or both pulpwood into two separate piles both in cutting young thinning and energy wood (Niemistö 2013). As a comparison, and clear cutting stands. The purpose of the study was to a very light thinning of a young downy birch stand can determine the productivity and time consumption func- sometimes lead to a slightly higher yield of stem wood tions of multi-tree cutting of pulpwood and energy wood and crown biomass than that of an unthinned downy birch in thinnings and clear cuttings of downy birch-dominated stand. However, low income from thinning removal hard- stands, along with the time consumption of cutting work ly compensates for the costs of thinning operations. An phases performed with a medium-sized harvester. In the intensive thinning, on the other hand, reduces the future time studies, the industrial wood fraction was harvested as growth of a downy birch-dominated stand too much. In delimbed and the energy wood fraction as non-delimbed. an unthinned dense downy birch-dominated stand, small According to the time consumption models, productivity trees die before regeneration felling, so the average stem was explained in terms of tree volume (dm3) and harvest- size in the regeneration felling is not significantly smaller ing intensity (number of trees removed per hectare). Pro- and the harvesting costs are thus no higher than in lightly ductivity was expressed in solid cubic metres per effective 3 thinned downy birch-dominated stands (Niemistö 2013). hour (m /E0h).

The objectives and implementation of the study Material and Methods In Finland, timber procurement is based on the cut- to-length (CTL) method and thus conventional CTL for- The machinery studied est machinery is used to harvest industrial roundwood and The study utilised a 6-wheel Komatsu 901.4 har- energy wood from tree stands (e.g. Laitila 2012, Ehlert vester with an attached Komatsu 350.1 harvester head and Pecenka 2013, Petty and Kärhä 2014). Despite the capable of multi-tree handling and a CRH 15 crane with high incidence of downy birch, there is very little pub- a maximum reach of 10 m (Komatsu Forest AB). Multi- lished research about the mechanised cutting of downy tree handling in the Komatsu 350.1 harvester head was birch (Lilleberg 1994, Di Fulvio et al. 2011, Niemistö et based on a software utilising the MaxiXplorer control and al. 2012, Fernandez-Lacruz et al. 2013). In earlier har- information system that enables the synchronising of the vesting studies, the main focus has primarily been on feed roller and delimbing knife functions to operate as an timber harvesting from pure or clearly conifer-dominant accumulating device (Komatsu Forest AB). The harvester stands (e.g. Sirén and Tanttu 2001, Wester and Elias- was a 2011 model and according to the manufacturer’s son 2003, Kärhä et al. 2004, Kärhä 2006a, Nurminen et information, the weight of the Komatsu 901.4 was 15100 al. 2006, Spinelli and Magagnotti 2013, Eriksson and kg and the engine power of the 6-cylinder SisuDiesel 66 Lindroos 2014). In terms of deciduous trees, CTL logging CTA–2V was 150 kW. The lifting torque of the crane was studies have mainly focused on poplar and eucalyptus or 156.5 kNm (gross) and the weight of the Komatsu 350.1 whole-tree harvesting from coppice forests or short ro- harvester head was 960 kg. The height of the harvester tation fields (Hartsough and Cooper 1999, Spinelli et al. head in cutting position was 1440 mm and the maximum 2002, Puttock et al. 2005, Spinelli et al. 2009, Danilovic feed roller opening was 520 mm (Figure 1). The number

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Figure 1. The Komatsu 350.1 harvester head used in the integrated harvest- ing of downy birch pulp- wood and energy wood. The operation of a har- vester head in multi-tree harvesting was based on the synchronising of feed roller and delimbing knife functions of feed rollers was three, the maximum feeding speed was ting work. Cuttings were carried out during the daytime 5 m/s and cutting was performed with a chainsaw (Kom- (06:00–17:00) and the ground had snow cover of between atsu Forest AB). 5 and 50 cm during the winter experiments. The tempera- ture was -24 to 0 °C during winter experiments and +5 to The time study 15 °C in summer conditions. In thinnings the harvester- The time study data on the integrated harvesting of operator chose the trees to be removed using the “thin- pulpwood and energy wood was collected from four dif- ning from below” method, in accordance with silvicul- ferent stands in Vaala (64°25’N, 26°42’E) in winter and tural recommendations (Niemistö 1991, Anon. 1994). All summer conditions from March to December 2013. There study plots were cut by the same harvester and operator. were two stands for clear cuttings and two stands for thin- The harvester-operator was skilful and he had 20 years nings. All the stands were located on drained peatlands of work experience in driving wheeled harvesters and six in close geographic proximity – within 10 km Euclidean years of work experience in multi-tree cutting using the distance – and all of the time study plots were free of un- two-pile method in thinnings and clear cuttings. dergrowth. According to the forest management plans, the In the time studies, the pulpwood fraction was har- average height of the trees before cutting at the stands were vested as delimbed and the tops as non-delimbed. Cutting in the range of 7–17 m and the diameters at a height of 1.3 was carried out by application of the multi-tree cutting m were in the range of 5–20 cm. The average initial density and the timber fractions were stacked into two separate was 1948 trees per hectare (SD 523) in the clear cutting piles along the strip road (Figure 2). In thinning, the trees time study plots, and 2368 trees per hectare (SD 415) in the were felled mostly perpendicular to the strip road and thinning time study plots (Tables 1 and 2). The probability piles were placed on both sides of the strip road at an an- of the t-statistics for equal initial densities was 0.0012, in- gle of approximately 90 degrees (Figure 2). In clear cut- dicating unequal stand characters. The 30 to 50-year-old ting, trees were felled forwards along the strip road, and first thinning stands were almost pure downy birch (Betula the piles were placed at the sides of the harvester almost pubescens). The boundaries of the visibly numbered time along the harvester moving line (Figure 2). study plots were marked with ribbons and poles at the stand. The total number of time study plots was 40 in clear cuttings and 25 in thinnings (Tables 1 and 2). The time study plots were 25 m long and the widths equalled the harvester’s work path (Laitila 2013a, Laitila 2013b). The area of the time study plots (m2) was calculated on the basis of an average strip road spacing of 16.6 m in clear cuttings and 23.8 m (6 plots) or 20.2 m (19 plots) in thinnings (cf. Chapter: The average spacing and width of strip roads). During harvesting, terrain conditions on the time study sites were estimated in line with the Finnish clas- sification system (Anon. 1990). The factors assessed were load-bearing capacity, roughness of terrain surface and steepness of the terrain. On the basis of the measurements, the study sites were classified as terrain class 1 (easy con- ditions). Strip roads were not marked in advance, but they Figure 2. Piling of pulpwood and energy wood fractions in were planned by the harvester-operator during the cut- downy birch-dominated clear cuttings (left) and thinnings (right)

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In the experiment, the pulpwood was harvested to the • Delays: time that is not related to effective work target top diameter of 5–7 cm (over bark) and a bolt length (repairs and maintenance, phone calls, etc.). of 3–5 m. In addition, trees that were less than 7 cm but The data analysis was conducted for effective work- more than 4 cm thick at a height of 1.3 m were considered ing time only (E0h), in order to avoid the confounding ef- to be energy wood. The operator visually estimated the di- fect of delay time, which is typically erratic (e.g. Spinelli ameter of the trees at that height. The target length of the and Visser 2008). The studies were also too short to re- energy wood, harvested as a whole tree, was 5–7 m. The cord representative delay times. non-delimbed tops of pulpwood stems were stacked with the energy wood into the same pile along the strip road Measurement of the timber volumes harvested (Figure 2).The energy wood fraction consisted mainly of The time study’s plot-wise mass and volume of har- the non-delimbed tops of pulpwood stems. vested timber fractions (for both pulpwood and energy The time study was carried out manually with a wood) were measured during forwarding using a crane Rufco-900 field computer (Nuutinen et al. 2008). The scale. Forwarding was completed immediately after cut- working time was recorded through the application of a ting trials with a Ponsse Wisent forwarder equipped with continuous timing method wherein a clock ran continu- a Ponsse LoadOptimizer crane scale, with an accuracy of ously and the times for different phases were separated 2 kg. The forwarder’s crane model was the PonsseK70+. from each other under distinct numeric codes (e.g. Hars- Pulpwood and energy wood were forwarded as separate tela 1991, Magagnotti et al. 2013). When the entire work timber assortments. The harvested pulpwood and energy process was recorded, the cutting functions had the high- wood was weighed first during loading at the time study est priority, followed by the moving and the arrangement plot and a second time at the roadside landing when un- elements. Auxiliary time use (e.g. planning of work and loading the full load. The weighting value at the roadside preparations) was included in the work phases in which landing was used as a correction factor for the plot-wise it was observed. Effective working time was divided into weighting values. The purpose of the weighing at the the following work phases: roadside landing was to improve on the accuracy of the • Moving forwards: begins when the harvester starts first plot-wise value because unloading conditions at the to move forwards and ends when it stops moving to per- roadside landing are more constant compared to loading form another activity. Moving can be divided into driving in the forest. The values for green tonnes of pulpwood and forwards from one work location to another and moving energy wood were converted to solid cubic metres (m3), at the work location. yielding green density values of birch and pine pulpwood • Positioning to cut: begins when the boom starts to and birch-dominant whole trees (Anon. 2010, Lindblad et swing towards the first tree and ends when the harvester al. 2010). There are seasonal variations in green density head is resting on the tree before the felling cut begins. values of harvested timber and in March, 935kg/m3 were • Felling or accumulating the felling: begins when the used for birch pulpwood, 923 kg/m3 for pine pulpwood felling cut starts, and ends when the accumulated tree bunch and 900 kg/m3 for birch-dominant whole trees (Anon. or tree starts moving to the processing point (the number of 2010, Lindblad et al. 2010). In September, the equivalent trees in each grapple bunch is observed and recorded). values were 866 kg/m3, 912 kg/m3, 900 kg/m3 and in De- • Transferring the bunch of trees to the processing cember 946 kg/m3, 959 kg/m3, and 1000 kg/m3 respective- point. The accumulated bunch of trees is moved next to the ly (Anon. 2010, Lindblad et al. 2010). strip road for delimbing and cross-cutting. This work phase In clear cuttings, the total number of trees harvested ends when the feeding and delimbing of the tree(s) starts. during the time study was 3234 and of the total volume, • Delimbing and cross-cutting: begins when the feed- 98.3 m3 were considered to be birch pulpwood, 9.2 m3 ing rolls start to roll the tree(s) and ends when the last pine pulpwood and 76.4 m3 non-delimbed energy wood. cross-cutting is done and the remaining tree top(s) is/are In thinnings, the total number of harvested trees was 1870 moved to the pile from the harvester head. and of the total volume 58.7 m3 were birch pulpwood, • Arranging stems, tops and whole trees into piles: 11.5 m3 pine pulpwood and 27.1 m3 non-delimbed energy arrangement of timber fractions into piles, with similar wood, respectively. The average forwarder payloads of timber assortments kept together in the pile (separately pulpwood and energy wood were 9.3 m3 and 4.7 m3 (full), outside the processing phase). and the payloads were noted to be equal both in thinnings • Moving backwards: Begins when the harvester and clear cuttings. starts to move backwards and ends when it stops moving The average volume (dm3) of trees harvested on a to perform another activity. Moving can be divided into time study plot was calculated by dividing the cutting re- driving backwards at the work location and speeding up moval (m3) by the number of trees harvested. On the clear the boom movements by moving the base machine back- cutting time study plots (Table 1), the average volume wards at the work location as necessary. of the harvested trees varied in the range of 16–96 dm3

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(mean 58 dm3), the harvesting intensity was 1,253–4,072 of the harvested trees varied in the range of 28–69 dm3 harvested trees per hectare (mean 1948 trees/ha), and cut- (mean 50 dm3), the harvesting intensity was 475–2,101 ting removal was 49–211 m3/ha (mean 111 m3/ha). On the harvested trees per hectare (mean 1,408/ha), and cutting thinning time study plots (Table 2), the average volume removal was 23–109 m3/ha (mean 63 m3/ha).

Table 1. Basic stand data for time study plots 1– 40 in clear cuttings

Plot number on Removal, trees Cutting removal, The share of assortments from the cutting Average volume of clear cuttings per hectare m3/ha removal: birch, pine & energy wood harvested trees, dm3

1 1879 146 48%; 9% & 43% 78 2 1711 111 45%; 7% & 48% 65 3 1421 91 43%; 13% & 44% 64 4 2096 104 21%; 22% & 56% 50 5 1976 89 15%; 8% & 77% 45 6 2289 81 20%; 10% & 70% 35 7 1542 76 27%; 10% & 62% 49 8 1759 59 20%; 15% & 65% 34 9 1711 100 12%; 27% & 60% 58 10 1590 85 39%; 9% & 53% 53 11 1253 61 23%; 17% & 60% 49 12 1470 92 21%; 27% & 52% 62 13 1711 78 33%; 3% & 64% 45 14 1783 107 29%; 7% & 65% 60 15 1421 77 53%; 0% & 47% 54 16 1807 117 39%; 11% & 49% 65 17 1518 114 53%; 3% & 43% 75 18 1735 101 54%; 0% & 46% 58 19 1927 118 62%; 1% & 37% 61 20 1446 77 63%; 7% & 30% 53 21 2217 72 51%; 0% & 49% 33 22 2409 75 58%; 0% & 42% 31 23 2602 77 56%; 0% & 44% 30 24 3228 105 39%; 6% & 55% 33 25 1686 49 40%; 4% & 55% 29 26 1807 58 37%; 0% & 63% 32 27 1759 66 39%; 13% & 47% 37 28 4072 66 0%; 0% & 100% 16 29 2048 164 75%; 1% & 25% 80 30 2168 181 75%; 0% & 25% 84 31 2000 176 70%; 0% & 30% 88 32 2241 147 71%; 0% & 29% 66 33 2192 211 73%; 1% & 27% 96 34 1662 153 77%; 0% & 23% 92 35 1952 172 72%; 3% & 25% 88 36 1494 91 78%; 0% & 22% 61 37 2385 178 66%; 0% & 34% 74 38 1446 119 63%; 0% & 37% 82 39 2000 190 79%; 2% & 19% 95 40 2506 196 73%; 0% & 27% 78 1948 trees/ha 111 m3/ha 48%; 6% & 46% 58 dm3 Mean (SD 523) (SD 43) (SD 20;8;16) (SD 21)

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Table 2. Basic stand data for time study plots 1– 25 in thinnings

Basal Mean Mean Number of Cutting The share of Average Plot area of Cutting diameter of height of remaining removal, assortments from the volume of number on remaining removal, remaining remaining trees per trees per cutting removal: birch, harvested thinnings trees, m2 m3/ha trees, cm trees, m hectare hectare pine & energy wood, % trees, dm3

1 17 14.3 14 1000 2101 109 37%; 19% & 39% 52 2 13 13.2 10 800 1126 33 36%; 11% & 48% 29 3 14 11 15 1000 2050 82 32%; 11% & 51% 40 4 15 12.9 13 800 1815 86 44%; 7% & 44% 47 5 19 16.2 13 800 1529 94 35%; 31% & 31% 62 6 14 14 14 1000 1681 76 34%: 19% & 42% 45 7 16 13.4 14 1000 1822 73 55%; 18% & 28 47 8 13 16 13 1000 1782 102 62%; 11% & 27% 68 9 12 14.9 10 800 1644 82 79%; 0% & 21% 59 10 10 11.6 10 1000 1307 67 72% ;4% & 24% 61 11 14 13.9 13 1000 1584 73 75%; 4% & 20% 54 12 15 14.9 11 800 1307 77 70%; 5% & 25% 69 13 11 13.4 14 1000 1782 75 81%; 0% & 19% 50 14 11 12.8 13 800 1267 73 54%: 27% & 19% 68 15 20 15.9 13 800 1960 109 45%; 36% & 19% 65 16 14 14.2 14 1000 931 46 74%; 4% & 22% 59 17 11 12 13 1000 1267 52 73%; 3% & 24% 48 18 11 11 15 1000 1109 37 52%; 8% & 40% 39 19 10 11.6 9 1000 1525 45 72%; 0% & 28% 35 20 9 11.5 10 1200 1564 42 70%; 0% & 30% 32 21 10 11.4 7 1000 970 23 67%: 0% & 33% 28 22 9 11.6 7 1000 851 26 77%: 0% & 23% 35 23 12 11.5 13 1200 475 24 47%; 39% & 14% 60 24 10 12.9 9 1000 931 31 82%; 0% & 18% 39 25 10 12.9 9 1000 812 35 80%: 0% & 20% 50 1408 12.8 cm 13.2 m 11.8 m2 960 trees/ha 63m3/ha 60%; 10% & 30% (SD 50 dm3 Mean trees/ha (SD 3.0) (SD 1.6) (SD 2.4) (SD 115) (SD 27) 17;12;10) (SD 13) (SD 430)

Inventory of the harvesting quality Tree data was collected after timber harvesting from two circular 50 m2 sample plots, situated as presented in Figure 3 on the time study plots. From the sample plots, the number of remaining trees, mean height (m), mean diameter at 1.3 m height (cm) and basal area (m2) were recorded (Table 2). In addition to basic tree data, both the width and the spacing of strip roads were measured at 40-metre intervals along the strip road. Their width was measured using the SLU method, in which the distances to the nearest trees were measured at right angles from the middle of the strip Figure 3. Location road, at intervals of 10 m on each side (Björheden and of the sample plots Fröding 1986). The measurement point on the trees was for stand measure- the cutting level, and the width of the strip road was the ments in the time sum of the two distances (Björheden and Fröding 1986). study areas in thin- These measurements were accurate to within 1 cm. The nings

2016, Vol. 22, No. 1 (42) ISSN 2029-9230 123121 BALTIC FORESTRY PRODUCTIVITY OF MULTI-TREE CUTTING IN THINNINGS /.../ J. LAITILA ET AL. distance between two parallel strip roads was measured birch-dominated stands, and the share of felling or accu- at right angles from the middle of the left‑hand strip road mulating fellings was 13–16 % (Figure 4). The propor- to the middle of the right-hand strip road. The accuracy of tion of the positioning-to-cut phase was 23–28 %. Moving these measurements was 10 cm. or driving in reverse between work locations represented 7–11 % of the effective working time (Figure 4). Transfer- Data analysis ring the bunch of trees to the processing point took 9–11 The recorded plot-wise time study data and the mea- % of the effective working time, and arranging timber as- sured harvested timber volumes were combined as a data sortments into piles took 1–2 % (Figure 4). 3 matrix. The time consumption of the main work elements Cutting productivity per effective hour (m /E0h) in- in the multi-tree cutting was formulated through the ap- creased as the volume of the harvested trees rose (Fig- plication of regression analysis in which the harvesting ure 5). On the time study sample plots, the lowest and conditions (volume of harvested trees and number of trees highest values recorded for multi-tree cutting productiv- 3 3 harvested per hectare) were independent variables. Sev- ity per effective hour were 5.6 m /E0h and 17.4 m /E0h 3 eral transformations and curve types were tested, so that in clear cuttings and 4.8 or 10.9 m /E0h in thinnings, re- we could achieve symmetrical residuals for the regression spectively (Figure 5). As for trees, the highest and lowest models and ensure the statistical significance of the coef- values recorded for cutting productivity per effective hour ficients. The regression analysis was carried out using the were 345 and 153 trees/E0h (mean 203 trees/E0h) in clear

SPSS statistics package, and characteristics of regression cuttings and 126–198 trees/E0h (mean 153 trees/E0h) in models are detailed in Table 3. The unit for calculation thinnings, respectively. Because the tree volume had an of effective time consumption was seconds per tree, and impact on the number of trees that fitted into the harvester multi-tree cutting productivity was expressed in solid cu- head, the number of grapple loads processed by means of 3 bic metres per effective hour (m /E0h). In the regression the multi-tree method (i.e. at least two trees in the grapple modelling, the work phases of multi-tree cutting were at a time) decreased as the trees’ volume increased (Figure combined into three main work elements: moving, ac- 6). On average, the harvester head processed 1.2 trees per cumulating felling, and processing (Table 3). In moving, grapple cycle, while grapple loads processed by means the time spent moving, also in reverse, was included. In of the multi-tree method accounted for 16 % of all time accumulation, the work phases of positioning to cut, ac- study data in clear cutting and 1.1 trees in thinnings per cumulating felling, and transferring the bunch of trees to grapple cycle and for 14 % of all time study data. the processing point were included. Delimbing and cross- cutting, and the arrangement of stems and tops into piles The time consumption models for the main work were included in the main work element of processing. elements Regression models were formulated for the time el- Results ements of moving, processing and accumulating felling and for the number of trees in the grapple during accumu- Distribution of work phases and the cutting produc- lating felling (Table 3). tivity in the time study Moving time (Tmoving) was dependent on the number In the time study of thinning and clear cutting, de- of trees harvested (Figure 7). The moving time per tree limbing and cross-cutting represented 36–43 % of the to- harvested decreased as the number of trees harvested per tal effective working time in multi-tree cutting of downy hectare increased; in such cases, it was possible to cut

Figure 4. Distribution of work elements when thinning or clear cutting downy birch- dominated stands in the integrated harvesting of pulpwood and energy wood. Total effective working time (E0h) recorded

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Figure 5. Cutting productivity recorded for the time study plots by average volume of har- vested tree in thinnings and clear cuttings of downy birch-dominated stands

Figure 6. The percentage of multi-tree cutting recorded for the time study plots by average volume of harvested tree in the integrated harvesting of pulpwood and energy wood in thinnings and clear cuttings of downy birch- dominated stands

Table 3. Statistical characteristics of regression models

Work phase Dependent r2 F-test N Term Constant/Coefficient t-test model variable F-value p Estimate Std. error t-value p

Moving TMoving T 0.141 3.626 0.070 25 Constant 6.873 2.282 3.012 0.006

in thinnings ln(x1T) -0.605 0.317 -1.904 0.070

Moving TMoving C 0.544 44.060 <0.001 40 Constant -0.023 0.198 -0.119 0.906

in clear cuttings 1/x1C 2375.117 357.826 6.638 <0.001

Accumulating NNumber of trees in the 0.049 1.088 0.309 25 Constant 1.064 0.080 13.236 <0.001 felling 3.960 3.797 1.043 0.309 grapple T 1/x in thinnings 2T

TAccumulating felling T 0.032 0.738 0.400 25 Constant 12.456 2.221 -0.859 0.400

x3T -1.667 1.940 5.608 <0.001

Accumulating NNumber of trees in the 0.768 125.749 <0.001 40 Constant 0.958 0.022 43.400 <0.001

felling grapple C 1/x2C 11.044 0.985 11.214 <0.001 in clear cuttings

TAccumulating felling C 0.167 7.632 0.009 40 Constant 12.599 1.055 11.941 <0.001

x3C -2.455 0.889 -2.763 0.009

Processing TProcessing T 0.514 23.298 <0.001 25 Constant 4.628 1.240 3.733 0.001

in thinnings x2T 0.116 0.024 4.827 <0.001

Processing TProcessing C 0.738 107.174 <0.001 40 Constant 1.799 0.540 3.328 0.002

in clear cuttings x2C 0.090 0.009 10.352 <0.001

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Figure 7. The time consumption of moving between work locations in thinnings and clear cuttings of downy birch-dominated stands as a function of trees harvested per hectare

more trees from a single work location. For thinnings, the NNumber of trees in the grapple T = 1.064 + 3.96×1/x2T , time consumption of moving was formulated as: where

Tmoving T = 6.873 - 0.605ln(x1T), NNumber of trees in the grapple T = the average number of trees in the harvester head per grapple cycle in thinnings;

where x2T = the average volume of the harvested trees in 3 Tmoving T = time for moving between work locations in thinnings, dm ; thinnings, expressed in seconds per tree; r2 = 0.049.

x1T = the number of trees harvested in thinnings, trees per hectare; TAccumulating felling T = 12.456-1.667x3T , r2 = 0.141. where

For clear cuttings, the time consumption of moving TAccumulating felling T = the time for positioning to cut, ac- was formulated as: cumulating felling, and transferring the bunch of trees to the processing point in thinnings, expressed in seconds

Tmoving C = -0.023 + 2375.177×1/x1C , per tree;

x3T = the average number of trees in the harvester where head per grapple cycle in thinnings; 2 Tmoving C = time for moving between work locations in r = 0.032. clear cuttings, expressed in seconds per tree;

x1C = the number of trees harvested in clear cuttings, For clear cuttings, the time consumption of multi- trees per hectare; tree cutting was formulated as: r2 = 0.544.

NNumber of trees in the grapple C = 0.958 + 11.044*1/x2C , The most important productivity factors in multi-tree cutting were the average tree volumes and the number of where trees in the harvester head per grapple cycle. The latter NNumber of trees in the grapple C = the average number of trees value (NNumber of trees in the grapple) was predicted on the basis of in the harvester head per grapple cycle in clear cuttings; the average volume of the harvested trees (Figure 8). The x2C = the average volume of the harvested trees in time consumed in accumulating fellings per harvested clear cuttings, dm3; 2 tree (TAccumulating felling) was dependent on the number of trees r = 0.768. in the harvester head in a grapple cycle (Figure 9):

For thinnings, the time consumption of multi-tree TAccumulating felling C = 12.599 - 2.455x3C , cutting was formulated as:

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Figure 8. The number of trees harvested per grapple cycle in thinnings and clear cuttings of downy birch-dominated stands as a function of average tree volume, dm3

Figure 9. The time consumption of stands as a function of trees per grapple cycle. accumulat- ing felling (more precisely, positioning to cut + accumulating the felling + transferring the bunch of trees to the processing point) per tree harvested, in thinnings and clear cuttings of downy birch-dominated

where where

TAccumulating felling C = the time for positioning to cut, ac- TProcessing T = time consumption of multi-tree process- cumulating felling, and transferring the bunch of trees to ing in thinnings, expressed in seconds per tree; the processing point in clear cuttings, expressed in sec- x2T =the average volume of the harvested trees in onds per tree; thinnings, dm3; 2 x3C = the average number of trees in the harvester r = 0.514. head per grapple cycle in clear cuttings; r2 = 0.167. For clear cuttings, the time consumption of process- ing formulated as:

Processing time per harvested tree (TProcessing) was modelled from the average volume of harvested trees TProcessing C = 1.799 + 0.09x2C , (Figure 10): where

For thinnings, the time consumption of processing TProcessing C = time consumption of multi-tree process- was formulated as: ing in clear cuttings, expressed in seconds per tree;

x2C = the average volume of the harvested trees in 3 TProcessing T = 4.628 +0.116x2T , clear cuttings, dm ; r2 = 0.738.

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The productivity of the multi-tree cutting and valid- 15–100 dm3 in clear cuttings and in 15–70 dm3 thinnings. ity of results Calculations using the time consumption model (TTotal)

The total time consumption (E0h) of multi-tree cut- showed that the harvesting intensity has a rather nominal ting per harvested tree (TTotal) was obtained by adding up effect on the cutting productivity compared to the average the time consumption values for the three main work ele- volume of harvested downy birch (Figure 11). According ments as follows: to the results, the cutting productivity per effective hour

TTotal = TMoving + TAccumulating felling +TProcessing increased almost linearly with the growth in the average The number of harvested trees per effective hour volume of harvested downy birch (Figure 11). In clear

(trees/E0h) was calculated by dividing 3600 seconds by cuttings, productivity was about 30–50% higher than cut- the total time consumption of a harvested tree (TTotal). Ef- ting productivity in thinnings (Figure 11). fective hour productivity expressed as a number of trees Figure 12 compares the cutting productivity recorded harvested (trees/E0h) was converted to solid cubic metres and modelled for the time study plots as a function of av- 3 (m /E0h) by multiplying the number of harvested trees erage volumes of harvested trees in thinnings and clear with the average volume of the harvested trees (x2). cuttings of downy birch-dominated stands. The results Figure 11 describes the effective working time pro- showed that time consumption models fit well to the time 3 ductivity (m /E0h) of the multi-tree cutting when the har- study data recorded and models do not systematically vesting intensity was 3,000, 2,000 or 1,000 trees per hect- give over- or underestimates for the cutting productivity are in clear cuttings and 1,500 or 1000 in thinnings. The of downy birch-dominated stands either in thinnings or average volume of harvested trees was within the range of clear cuttings (Figure 12).

Figure 10. The time consumption of multi-tree processing in thinnings and clear cuttings of downy birch-dominated stands as a function of average tree volume

3 Figure 11. Cutting productivity (m /E0h) in the integrated harvesting of pulpwood and energy wood as a function of average tree volume and number of trees harvested per hectare in thinnings and clear cuttings of downy birch- dominated stands

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Figure 12. Cutting productivity recorded and modelled for the time study plots as a func- tion of average volumes of harvested trees in thinnings and clear cuttings of downy birch- dominated stands

The average spacing and width of strip roads birch. In multi-tree cutting, non-simultaneous feed-in of The average strip road spacing observed on the first trees is a common problem, i.e. the delimbed trees do not time study thinning stand was 23.8 m (SD 2.1 m) and on pass through the grapple at the same pace (Heikkilä et al. the second stand it was 20.2 m (SD 2.4 m). The deviances 2006). This results in unwanted variation in the lengths of strip road spacing between two drained peatland stands and top diameters of harvested timber. were caused by the different spacing of the ditches on the However, in this study, non-simultaneous feeding led stands. The average distance between the strip roads were to interruptions in only a few cases, due to the operator’s significantly (p = 0.004) different from the recommended skills in selecting trees suitable for multi-tree cutting. minimum spacing of 20 m for thinnings (Anon. 2003). Like tree bends and curves, forked stems also prevent The average width of the strip roads was 422 cm (SD 25 multi-tree cutting: it has been found that processing takes cm) on thinnings, somewhat more than the recommended around 50% longer in the case of single-tree harvesting maximum width of 400 cm (Anon. 2003). The harvesting than in the usual felling, delimbing and piling of non- quality (Table 2) achieved the recommended silvicultural forked timber (Niemistö et al. 2012). In this study, the standards in thinnings (Niemistö 1991, Anon. 1994). The number of forked trees impeding cutting was limited to average strip road spacing observed on the clear cutting individual trees, since the harvested stands were mainly at stands was 16.6 m (SD 1.0 m). the first thinning stage, i.e. they were rather small in size. As regards clear cutting of downy birch-dominated Discussion and Conclusions stands, the results are consistent with those of Niemistö et al. (2012), when compared with the clear cutting of As expected, clear cutting enhanced harvesting pro- downy birch on a site where there is no need to retain or ductivity when compared with thinning, but multi-tree account for the understorey. In the harvesting study by Ni- cutting only had a minor effect on productivity in the case emistö et al. (2012), downy birch serving as shelter trees of both harvesting methods due to the low percentage of for spruce were harvested using a medium-sized thin- multi-tree cutting. Multi-tree cutting accounted for 16 ning harvester (John Deere 1070/745) and the single-tree % of all the time study data in clear cuttings and 14% method. The time study stands marked for cutting in the in thinnings. Compared to studies in Scots pine stands Niemistö et al. (2012) study were located in Kärsämäki, (e.g. Lehtimäki and Nurmi 2011, Kärhä 2011, Laitila and Pyhäjärvi and Kälviä, i.e. in fairly close geographic prox- Väätäinen 2013b, Petty and Kärhä 2014), the proportion imity to the stands situated in Vaala (50, 90 and 160 km of multi-tree cutting and cutting productivity was sig- Euclidean distance). nificantly lower. For example, in the thinning study by Lilleberg (1994) noted that as the share of downy Laitila and Väätäinen (2013b), grapple cycles processed birch increases, the possibilities of applying multi-tree by means of the multi-tree method accounted for 57 % cutting to final cuttings in Northern Finland decrease, of all time study data and cutting productivity were 5-6 whereas a higher number of trees per hectare and a higher 3 m /E0h higher than the productivity level of this study. share of conifers increase the same opportunities. In time Since downy birch stems are often bent and crooked, they studies conducted on Swedish final cutting sites domi- are ill-suited to multi-tree cutting using feeding and de- nated by conifer trees and small-dimensioned tree stands limbing harvester heads. This led to the fairly frequent (120–220 dm3 under bark), multi-tree harvesting has been use of the single-tree method when processing downy found to enhance work productivity in comparison to the

2016, Vol. 22, No. 1 (42) ISSN 2029-9230 129127 BALTIC FORESTRY PRODUCTIVITY OF MULTI-TREE CUTTING IN THINNINGS /.../ J. LAITILA ET AL. single-tree method by 4–16%, in line with the decrease that productivity curves based on follow-up studies are in the stem size of the trees (Brunberg 2012). Long-term significantly lower than productivity curves calculated follow-up studies have recorded an average productivity on the basis of time studies (Mäki 1999, Ryynänen and increase of 5% in the same harvesting conditions (Brun- Rönkkö 2001, Sirén and Aaltio 2003). The reasons for this berg 2012). According to Sirén et al. (2013b) and Brun- include the fact that time studies based on brief work on berg (2012), reasons for the low utilisation of multi-tree sample plots do not fully correspond to real-world work harvesting include the distribution of harvesting intensity throughout the year. Accordingly, a long-term follow-up over several tree species, the presence of a spruce under- study would give a more reliable picture of productiv- storey and, in some cases, the operators having little ex- ity in practice, as well as of the functional and technical perience of this work method. utilisation rate of the base machine and harvester head in The fact that downy birch tops were forked and variable stand conditions at different times of the year (Si- thick-branched favoured the harvesting of the downy rén 1998, Ryynänen and Rönkkö 2001, Kariniemi 2006, birch energy fraction as non-delimbed whole trees over Sirén and Aaltio 2003, Väätäinen et al. 2005, Spinelli and delimbed stems (cf. Laitila and Väätäinen 2012). From Visser 2008, Purfurst 2010, Eriksson and Lindroos 2014). the forwarding point of view, tree sections should be as Peatlands are very problematic from the bearing ca- long as possible in order to maximise the load size of the pacity point of view. Therefore, logging operations on forwarder (Björheden 1997). Payload is one of the most peatlands in Finland are mainly carried out during the important productivity and cost factors in forwarding, and coldest weeks in winter time. With regard to harvesting the lengthening of the forwarded timber is the easiest way logistics, it would be interesting to examine whether clear to increase its size. The disadvantages are that the exces- cutting facilitates the transformation of some peatland sive lengthening of forwarded timber complicates the mo- stands marked for cutting in winter into stands marked bility and loading work. Furthermore, the forwarders tend for cutting in summer (Ala-Ilomäki 2006, Ala-Ilomäki et to become tail-heavy (Laitila et al. 2007). al. 2011, Sirén et al. 2013a). This is because, compared to All study plots were cut by the same harvester and thinning, clear cutting allows greater freedom in the loca- operator. This is both advantageous and disadvantageous. tion of forwarding routes on site, as well as in organising When machine and operator are the same, we can elimi- route schedules, thus decreasing the soil disturbances (cf. nate the effect that is caused by these factors, but on the Uusitalo et al. 2015). other hand, the generalisation of harvesting productivity According to Heikkilä (2007), more efficient utili- is restricted. Due to a limited number of time study plots, sation of peatland forests requires determined efforts to stands, operators and machines, the results do not rep- prolong the harvesting season, since seasonal variation resent the nationwide time consumption and productiv- in harvesting results in high harvesting and timber stor- ity level of harvesting in young downy birch-dominated age costs, and complicates the recruitment of a profes- stands. However, the regression models presented provide sional workforce. On the basis of the simulation study by novel productivity estimates of modern multi-tree har- Väätäinen et al. (2010), it was found that year-round har- vesting system in typical harvesting conditions for cost vesting of timber from peatlands resulted in higher em- calculations and different types of simulation and model- ployment among operators and higher utilisation rates for ling purposes. machinery. It also provided the opportunity to increase the In the formulated regression models for time elements annual harvesting volume without adding to the amount and grapple sizes, the predicted variables were the same as of harvesting equipment. A survey of experts conducted in corresponding formulas in earlier studies (Siren 1998, by Metsäteho suggests that the prerequisites for increas- Ryynänen and Rönkkö 2001, Nurminen et al. 2006, Laitila ing the efficiency of timber harvesting in young forests and Väätäinen 2013b). Nevertheless, in some functions include better harvesting conditions and the rationalisa- the predictors were not statistically significant (p-value > tion of harvesting (Oikari et al. 2010). Greater harvesting 0.05). This could be particularly noted in part of the mod- efficiency has the aim of lowering unit costs. In practical els of the thinning method (see Table 3). Therefore, mostly terms, this means harvesting more timber within the same as a result of the relatively limited amount of observations time unit, or at a lower cost per operating hour. and lack of other possibly predicting variables in the for- Harvesting conditions in thinnings and clear cuttings mula, some of the presented regression functions do not fit of young downy birch-dominated stands are not similar well with the recorded observations. because the purpose of thinnings is to regulate the spac- Several studies have shown that the operator has the ing of vital trees as well as to improve quality properties, most important impact on harvesting productivity (e.g. Si- such as uniformity, reduced branchiness, and better stem rén 1998, Ryynänen and Rönkkö 2001, Kariniemi 2006, form of the remaining stand. Thinning from below also Väätäinen et al. 2005, Ovaskainen 2009, Purfurst 2010, salvages suppressed, damaged and dying trees that would Palander et al. 2012). Previous studies have also shown otherwise be lost through natural mortality. Thinning im-

2016, Vol. 22, No. 1 (42) ISSN 2029-9230 128130 BALTIC FORESTRY PRODUCTIVITY OF MULTI-TREE CUTTING IN THINNINGS /.../ J. LAITILA ET AL. proves the physical logging conditions of future cuttings, Björheden, R. 1997. Studies of large scale forest supply systems. whereas in clear cuttings both the high and poor quality Dissertation. Acta Universitatis Agriculturae Sueciae/Silves- tria 31, 23 pp. trees are removed simultaneously. For example, in our Brunberg, T. 2012. Flerträdshantering i slutavverkning ökär presta- study the harvesting intensity was 1,253–4,072 harvested tionen [Multitree handling in final felling improves productiv- trees per hectare in clear cuttings and in thinnings the har- ity]. Resultat från Skogforsk. Nr. 13/2012, 4 pp. (In Swedish vesting intensity was 475–2,101 harvested trees per hect- with English summary). Danilovic, M., Tomasevic, I. and Gacic, D. 2011. Efficiency of are. In clear cuttings, the cutting removal and the volume John Deere 1470D ECOIII Harvester in Poplar Plantations. of harvested trees is higher. Croatian Journal of Forest Engineering 32(1):533–548. The study highlighted the need to improve the suit- Di Fulvio, F., Kroon, A., Bergström, D. and Nordfjell, T. 2011. ability of the current harvesting equipment fleet for the Comparison of energywood and pulpwood thinning systems in young birch stands. Scandinavian Journal of Forest Research harvesting and multi-tree harvesting of birch and other (26)4:339–349. bent and crooked trees. This is because harvesting condi- Di Fulvio, F., Bergström, D., Kons, K. and Nordfjell, T. 2012. tions more favourable to clear cutting than thinning are Productivity and Profitability of Forest Machines in the Har- the main factors underlying the observed leap in produc- vesting of Normal and Overgrown Willow Plantations. Croa- tian Journal of Forest Engineering 33(1):25–37. tivity: 1) The tree-specific moving time shortened when Di Fulvio, F. and Bergström, D. 2013. Analyses of a single-ma- more trees could be harvested on the same spot than dur- chine system for harvesting pulpwood and/or energy-wood in ing thinning, 2) The removal of trees was systematic in early thinnings. International Journal of Forest Engineering clear cutting while it was selective in thinning, 3) In clear (24)1:2–15. Eriksson, M. and Lindroos, O. 2014. Productivity of harvesters cutting, the remaining tree stand did not hamper the de- and forwarders in CTL-operations in northern Sweden based limbing, cutting or piling of trees. Factors enhancing the on large follow-up dataset. International Journal of Forest En- efficiency of forwarding include better working condi- gineering (25)3:179-200. tions and higher removal per hectare than in the case of Ehlert, D. and Pecenka, R. 2013. 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thinning of Picea abies plantations. Scandinavian Journal of lokseen työpistetasolla [The significance of a harvester opera- Forest Research 25(1): 69–77. tor’s tacit knowledge for cutting with a single-grip harvester]. Spinelli, R. and Maganotti, N. 2013. The effect of harvest tree dis- Finnish Forest Research Institute Research Papers 937, 100 tribution on harvesting productivity in selection cuts. Scandi- pp. (In Finnish) navian Journal of Forest Research (28)7:701–709. Väätäinen, K., Lamminen, S., Sirén, M., Ala-Ilomäki, J. and Suchomel, C., Becker, G. and Pyttel, P. 2011. Fully mechanized Asikainen, A. 2010. Ympärivuotisen puunkorjuun kustan- harvesting in aged oak coppice stands. Forest Products Jour- nusvaikutukset ojitetuilla turvemailla − korjuuyrittäjätason nal 61(4):290–296. simulointitutkimus [Operational efficiency of the year-round Suchomel, C., Spinelli, R. and Magagnotti, N. 2012. Productiv- CTL-harvesting on sensitive sites in Finland - A simulation ity of Processing Hardwood from Coppice Forests. Croatian study]. Metlan työraportteja / Working Papers of the Finnish Journal of Forest Engineering 33(1):39–47. Forest Research Institute 184, 57 pp. (in Finnish). Uusitalo, J., Salomäki, M. and Ala-Ilomäki, J. 2015. The Effect Wester, F. and Eliasson, L. 2003. Productivity in final felling and of Wider Logging Trails on Rut Formation in the Harvesting thinning for a combined harvester-forwarder (harwarder). In- of Peatland Forests. Croatian Journal of Forest Engineering ternational Journal of Forest Engineering 14(2): 45–51. 36(1):125-130. Väätäinen, K., Ovaskainen, H., Ranta, P. and Ala-Fossi, A. 2005. Hakkuukonekuljettajan hiljaisen tiedon merkitys hakkuutu- Received 10 April 2015 Accepted 25 January 2016

2016, Vol. 22, No. 1 (42) ISSN 2029-9230 133131 BALTIC FORESTRY COMPRESSION STRENGTH PERPENDICULAR TO GRAIN CHARACTERISTICS /.../ R. ESEN ET AL. Compression Strength Perpendicular to Grain Characteristics of Impregnated Laminated Veneer Lumbers Exposed to Sea Water

*RAŞIT ESEN*, ŞEREF KURT AND CEMAL ÖZCAN Karabük University,Technical Education Faculty, Department of Furniture and Decoration Education, Karabük 78050, Turkey , *Corresponding author. Tel.: +90 370 433 82 00/1267 fax: +90 370 433 82 04 e-mail adress: [email protected]

Esen,* R., Kurt, Ş. and Özcan, C. 2016. Compression Strength Perpendicular to Grain Characteristics of Impreg- nated Laminated Veneer Lumbers Exposed to Sea Water. Baltic Forestry 22(1): 132-138.

Abstract

The purpose of this study is to determine the compression strength perpendicular to grain of laminated veneer lumber exposed to sea water 3, 6, 9 and 12 months and obtained from Scots pine by using different adhesive and impregnating materials. While the highest compression strength perpendicular to grain is obtained from then unimpregnated samples, which are not exposed to sea wa- ter, with 39.56 N/mm2 the lowest compression strength perpendicular to grain is obtained from the unimpregnated samples exposed to sea water for 12 months with 10.94 N/mm2.

Keywords: pine, compression strength perpendicular to grain, LVL, biodegradation, preservation

Introduction brought about by fungi, bacteria, insects, and marine bor- ers (Becker 1974). Wood is a hygroscopic material, and its mass, dimen- Toxic preservatives function by disrupting the cel- sions, and density, as well as its mechanical, elastic, elec- lular organisation of microorganisms so that the organ- trical, thermal, and transport properties are affected by its ism dies. Thus, numerous organic salts of copper, zinc, moisture content. The moisture content of wood in the arsenic, and boron have been used as wood preservatives, living tree is always above the fiber-saturation point. The generally with added chromium compounds, to reduce cell walls in green wood are, therefore, in the fully satu- rapid leaching of the water-soluble compounds. Among rated condition and no hygroscopic shrinking or swelling organic compounds, coal-tar creosote and pentachloro- occurs, except that resulting from changes in fiber-satu- phenol are important toxic preservatives in wide commer- ration points already referred to, which are a function of cial use (Subramanian 1984). temperature (Skaar 1983). Decomposition of wood is an important part of the The use of composite products gained from wood carbon cycle of nature. Decomposition is caused by fungi, increase day by day. One of these composite products insects, and marine borers that use the wood as food or is laminated veneer lumbers. In our country, an increase shelter, or both. Lignin in wood provides a physical bar- in the use of laminated veneer lumbers in specific fields rier to enzymatic decomposition of cellulose and hemicel- is observed. With the use of laminated veneer lumbers, luloses. This barrier is breached mechanically by insects products in desired curve and shape can be produced. Nat- and marine borers, biochemically by white- and soft-rot urally, there is a need for curved trees in the production fungi, and possibly by small nonenzyme catalysts in the of wooden boat and yacht, and in our country existence of case of brown-rot fungi. Rapid strength loss occurs with these kinds of wood materials may not be continuous. As all decay fungi, but especially with brown-rot fungi. an alternative to these kinds of curved trees which can be Strength loss due to insect attack is roughly proportional used in the production of wooden boat and yacht, lami- to the amount of wood removed (Kirk and Cowling 1984). nated veneer lumbers may be suggested. It should be appreciated that every application of The biodegradation of wood, whether it is above wood in its natural or unprocessed state is affected po- ground, by soil contact, or in marine applications, is tentially by the tendency to a relatively large cross-grain

2016, Vol. 22, No. 1 (42) ISSN 2029-9230 132134 BALTIC FORESTRY COMPRESSION STRENGTH PERPENDICULAR TO GRAIN CHARACTERISTICS /.../ R. ESEN ET AL. dimensional change whenever significant moisture con- Adhesives tent changes in service is expected. For example, the per- Polyvinylacetate (PVAc) adhesive is usually prefer- formance of every structural connection in wood, with the able for the assembly process in the furniture industry. possible exception of a glued joint, can be affected by dif- According to the producer’s recommendations, the adhe- ferent dimensional changes in the members. Even simple sive was applied in the amount of 180-190 g/m² to the glued joints, including those in laminated wood members, surfaces. Its viscosity was 16,000 ± 3,000 mPa·s at 25 ºC, show shrinkage or swelling stresses if the pieces put to- density 1.1 ± 0.02 g/ml at 20 ºC, and 20 minutes for cold gether do not have identical moisture response properties process is recommended at 6-15 % humidity. The TS 3891 (Bozkurt 1986). standard procedure was used for applying PVAc adhesive In focusing attention on wood bonding, we are deal- that supplied by a company (TSE 1983). ing with nature’s own unique material whose sophisticat- Manufacturer’s documentation describes Desmodur- ed structure and complexities are at the same time baf- VTKA as a polyurethane-based one-component solvent- fling and challenging. Thus there are several complicating free adhesive that is widely used for the assembly process factors in the study of wood as an adherend: the species; in the furniture industry. It is used for gluing wood, met- heartwood, sapwood, earlywood, latewood, surface planes als, polyester, stone, glass, ceramic, PVC, and other plas- in radial, tangential, longitudinal, or intermediate direc- tic materials. Its application is specially recommended in tions; pH, porosity, moisture content, and extractives are locations subjected to high-level humidity. The gluing all capable of modifying the bonding properties of wood process was carried out at 20 ºC and 65 % relative humid- (Blomquist 1983, Adhesive Bonding of Wood 1975). ity. According to the producer’s recommendations, the ad- Today, synthetic resins are being produced according hesive was applied in the amount of 180-190 g/m² to the to the wood materials used on dry and damp conditions. surfaces. Its viscosity was -14,000 ± 3,000 mPa·s at 25 ºC, They are also convenient for use in the workshops and the density was 1.11 ± 0.02 g/ml at 20 ºC, and it showed straight manufacturing. To prevent material scraps and resistance against the cold air (Polisan 1999). increase the quality, research studies have been carried The building blocks of PF are phenol and formal- on the development of glue and its new application areas dehyde. Phenol is derived from crude oil. A principal (Örs et al. 1999). feedstock of phenol is toluene and benzene. Toluene is The demand for engineered wood products such as converted into benzoic acid; benzene is combined with oriented strand board, glulam and laminated veneer lum- propylene into commune. Together with benzoic acid it ber, LVL, has increased due to a constant increase in the forms phenol. Phenol and formaldehyde are combined in global population. The grain of each layer of veneer as- a reactor into PF resin. It is commonly shipped to engi- sembled into LVL runs parallel with each adjacent ply neered wood product plants as a colloidal aqueous solu- (Badwin 1985). Being a homogeneous and dimensionally tion with a solid content between 30 % (for LVL) and 50 stable building material, LVL can be used where strength % (for HB and OSB). This liquid is odourless, of dark- and stability are required (Colak et al. 2004). brownish colour, and, of course, not flammable. LVL panels, like plywood, are manufactured using different synthetic resins depending on where they are Impregnation Chemicals used. Phenol formaldehyde resins are generally used as As impregnation chemicals; protim-paraffin, Tanal- a binder for exterior grade panel production (Pizzi 1993). ith-c (CCA) and creosote, were used. The mixture of pro- Main purpose of this research is to determine the re- tim and paraffin with the ratio equal 50 % concentrations sistance characteristics of laminated veneer lumbers both were used at 60 °C as solution. Tanalith-c with 4 % con- impregnated and bonded with different adhesives. For this centration and creosote without being diluted were used purpose, Scots pine wood was used. For the impregnation for the impregnation process. Features related to impreg- process, the mixture of protim-paraffin, Tanalith-c (CCA) nation materials have been shown in Table 1. and creosote were used. Table 1. Peculiarities of impregnation chemicals and test plan Materials Impregnation pH Density, g/ml Chemicals Wood Species BI AI BI AI Scots pine (Pinus sylvestris L.) was chosen randomly Tanalith – C 2.36 2.58 1.62 1.68 from timber supplier of Ankara, Turkey. A special empha- Protim – Parafin 5 5.2 1.08 1.15 sis was put on the selection of the wood material. Accord- Creosote 5.88 5.78 1.12 1.15 ingly, non-deficient, whole, knotless, normally grown Notes: BI: Before impregnation, AI: After impregnation (without zone line, reaction wood, decay, insect or fungal infection) wood materials are selected.

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Methods Md is the dry mass before impregnation, kg, V is the volume of the sample, m3, and Determination of density C, % is the concentration of the solution. The dry densities of the wood materials used for the preparation of treatment samples were determined ac- The characteristic features of the impregnation cording to TS 2472(1976). Accordingly, air-dried samples chemicals were determined before and after impregnation were oven dried up at 103 ± 2 °C until they reached con- processes. All processes were carried out at 20 ± 2 °C. stant weights. Then, the samples were cooled in a desicca- Impregnated test samples were kept at 20 ± 2 °C and 65 ± tor containing calcium chloride and weighed in an analyt- 3 % relative humidity until they reached constant weight. ic balance with ± 0.01 g sensitivity. Afterward, the dimen- Afterward, approximately 180 g/m2 adhesive was applied sions of the wood materials were measured by a compass to the bonding surfaces of samples, based on TS 5430 EN with ± 0.001 mm sensitivity and the volumes were deter- 204 (TSE 2003). Bonding was obtained with 0.5 N/mm2 mined by the stereo metric method. The oven dry density press pressure and 24-h pressing time. Press temperatures (δo) was calculated with the following equation: were applied as 110 °C for PF adhesive by taking the gen- eral curing temperatures recommended by their manufac- 80 = Mo/V0 (g/cm3), (1) turers into consideration. Control samples and impregnated samples were where exposed to water in Amasra district of Bartın for 3, 6, 9 Mo is the oven dry weight (g), and and12 months. V0 is the dry volume (cm3) of the wood material. The wood samples taken from the sea were condi- tioned at 20 ± 2 °C and 65 ± 3% relative humidity un- Preparation of experimental samples til they reached constant weight by holding them for 4-5 The wood samples cut from sap wood were condi- months in a climatization room. DensityS weights of the tioned at 20 ± 2 °C and 65± 3 % relative humidity un- samples taken from the sea were also determined. More- til they reached constant weight by holding them for 3 over, compression strength perpendicular to grain of sam- months in a climatization room. There were 1600 test ples, which were not exposed to water and which were samples with 12 % average moisture with dimensions of exposed to water for 3, 6, 9 and 12 months, was defined. 20 × 20 × 30 mm according to the procedure of TS 2473 for each wood species (1976). Execution of the Test The impregnation process was carried out according In accordance with TS 2473, compression strength to the principles of ASTM D 1413-76 (1976). A vacuum, perpendicular to grain was determined on match basis. which was equal to 60 cmHg, was applied to the samples. Universal test machine has been working quickly, within They were then dipped for 60 min in a solution subject 1-2 minutes from sample installation time to sample be- to open air pressure. Before the impregnation process all ing crushed coming up to 6 mm/min. Experiments on the samples were weighed and then kiln dried at 103 ± 2 °C physical action to the first cross section area of the sample until they reached constant weight. Then, the samples were allowed to measure compression force applied and then weighed in an analytic balance with a sensitivity of 0.01 g. to calculate compression strength perpendicular to grain, After impregnation, all impregnated samples were held for (σb), from the equation below: 15 days in circulating air for evaporation of the solvent. After this period the impregnated samples were kiln σb = Fmax /A N/mm², (4) dried at 103 ± 2 °C until they reached constant weight. After cooling, all dried samples in the desiccator were weighed where on the scale. The dry weights of the samples were deter- Fmax is the maximum force at crush; mined and recorded. The amount of retention (R, kg/m³) A is the sample cross section area (mm²). and ratio of retention (R, %) were calculated as follows: Data Analyses , kg/m³ (2) By using three different types of adhesive substances and control, three impregnation chemicals and control and four exposure time intervals and control, a total of 1600 , (3) samples (4 × 4 × 5 × 20) were prepared using 20 samples for each parameter. Multiple analysis of variance was where used to determine the differences between the bonding G is the mass of the sample after impregnation (T2, kg) strengths of the jointing surfaces of the prepared samples. minus the mass of the sample before impregnation (Tl, kg), The Duncan test was used to determine whether there was Mdi is the dry mass after impregnation (kg), a significant difference between the groups.

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Results to sea, not processed with impregnation by LVL, but bond- ed with D-VTKA. The lowest compression strength per- The averages of density are given in Table 2. The pendicular to grain (10.94 N/mm2) was obtained in unpro- highest density (0.819 gr/cm3) was obtained in prepared cessed samples impregnated for 12 months and massive. Scots pine samples impregnated with Tanalith-C, bonded with PVAc adhesive. Table 4. Average value of Compression strength vertical to The highest retention amounts are given in Table 3. grain (N/mm2) The highest retention amounts (550.0 kg/m³) were found to be in samples impregnated with Protim-Parafin. The Phenol Impreg- Exposed PVAc-D4 Formal- D-VTKA Control lowest retention amounts (8.80 kg/m³) were found to be nation to time in samples impregnated with Tanalith - C. dehyde The averages of compression strength perpendicular Control 32.06 34.52 36.62 25.85 to grain are given in Table 4. 3 month 31.36 32.67 35.77 22.95 The highest compression strength perpendicular to Protim- 6 month 17.35 30.52 35.33 16.67 grain (39.56 N/mm2) was obtained in samples not exposed paraffin 9 month 16.96 29.81 30.67 11.46 Table 2. Average values of density (gr/cm3) 12 month 16.85 28.76 30.06 11.82 Control 24.10 19.80 22.93 25.00 Impregna- Phenol 3 month 22.76 19.36 21.45 24.23 Exposed to tion PVAc-D4 Formal- D-VTKA Control time Creosote 6 month 21.20 18.17 25.19 23.42 Materials dehyde 9 month 20.27 17.24 23.97 21.47 Control 0.743 0.720 0.725 0.496 12 month 18.46 16.54 23.07 11.37 3 month 0.725 0.716 0.716 0.490 Control 26.43 25.11 23.80 24.50 Protim- 6 month 0.721 0.710 0.713 0.478 3 month 24.56 24.80 22.56 25.24 paraffin 9 month 0.716 0.669 0.707 0.466 Tanalith-C 6 month 22.51 23.46 22.65 27.04 12 month 0.706 0.618 0.700 0.453 9 month 19.16 21.70 22.23 19.76 Control 0.797 0.730 0.670 0.483 12 month 18.99 20.12 21.48 14.56 3 month 0.785 0.728 0.661 0.474 Control 36.87 25.20 39.56 26.75 Creosote 6 month 0.763 0.676 0.656 0.470 3 month 29.90 22.96 26.84 22.03 9 month 0.697 0.655 0.636 0.465 Control 6 month 27.51 25.53 25.45 14.49 26.29 23.62 24.38 11.80 12 month 0.687 0.650 0.624 0.454 9 month 25.59 22.90 22.99 10.94 Control 0.819 0.712 0.701 0.497 12 month 3 month 0.797 0.687 0.685 0.486 Table 5. Multiple variance analysis for evaluating the effect of Tanalith-C 6 month 0.793 0.680 0.682 0.481 adhesive substance type, impregnation materials, and exposure 9 month 0.788 0.675 0.678 0.479 time on compression strength perpendicular to grain 12 month 0.681 0.670 0.670 0.477 Type II 0.553 0.547 0.519 0.463 Mean Control Source Sum of df F Significance Square 3 month 0.546 0.540 0.515 0.461 Squares Control 6 month 0.540 0.535 0.508 0.454 Factor A 1634.553 3 544.851 49.315 0.000 9 month 0.535 0.520 0.505 0.443 Factor B 1002.737 3 334.246 30.253 0.000 Factor C 2149.748 4 537.437 48.643 0.000 12 month 0.530 0.508 0.500 0.437 A×B 2330.237 9 258.915 23.434 0.000 Table 3. Amount of retention (kg/m3) A×C 584.470 12 48.706 4.408 0.000 B×C 540.189 12 45.016 4.074 0.000 Impregna- St. Minimum Maximum Mean A×B×C 539.860 36 14.996 1.357 0.104 tion Devia- Variance value value value Materials tion Notes: Factor A =Adhesive substance type( PVAc-D4, D-VTKA, Phe- Tanalith - C 8.60 9.00 8.80 0.108 0.012 nol Formaldehyde), Kreozot 408.0 416.0 412.0 2.309 5.333 Factor B = Impregnation materials (Tanalith- C, Creosote, Protim - Protim-paraffin, control) 540.0 560.0 550.0 5.374 28.889 Parafin Factor C = Exposure time (Control, 3, 6, 9 and 12 month)

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The multivariance analysis applied on the data ob- material and exposure time, exposure time and adhesive tained from the compression strength perpendicular to type at the same time were statistically significant. On the grain in the following manner: other hand, according to the variance analysis, exposure Factor A = Adhesive type (PVAc-D4, D-VTKA, Phe- time, adhesive type and the effects of impregnation mate- nol Formaldehyde), rial interactions were not statistically significant. The re- Factor B = Impregnate materials (Tanalith- C, Creo- sults of the Duncan test of the compression strength per- sote, Protim-paraffin, control), pendicular to grain (N/mm2) are given in Table 6. Factor C = Exposure time (Control, 3, 6, 9, 12 months) As a result of the comparison of exposure time statis- According to the variance analysis, the effects of ad- tically, in the compression strength perpendicular to grain hesive substance type, the effects of impregnation mate- of Scots pine, the difference is observed statistically. No rial, exposure time separately, the effects of impregnation difference between sample groups, which were exposed

Table 6. Duncan test of Compression strength perpendicular to grain

Homogenity Homogenity Factors Mean Factors Mean Group Group

12 Month Control – Control 10.94 a 6 Month PF - Tanalith-C 23.46 rstuv 12 Month Control - Creosote 11.37 a 9 Month PF - Control 23.62 stuvy 9 Month Control - Protim- Parafin 11.46 a Control- D-VTKA - Tanalith-C 23.80 tuvy 12 Month Control - Protim- Parafin 11.82 a 9 Month D-VTKA - Creosote 23.97 tuvy 9 Month Control – Control 11.80 a Control - PVAc-D4- Creosote 24.10 tuvyz 6 Month Control – Control 14.49 b 3 Month Control - Creosote 24.23 tuvzyA 12 Month Control - Tanalith-C 14.56 b 9 Month D-VTKA - Control 24.38 uvyzAB 12 Month PF – Creosote 16.54 c Control - Control- Tanalith-C 24.50 vyzABC 6 Month Control - Protim- Parafin 16.67 c 3 Month PVAc-D4- Tanalith-C 24.56 vyzABC 12 month PVAc-D4- Protim- Parafin 16.85 c 3 Month PF - Tanalith-C 24.80 yzABCD PVAc-D4- Protim- Parafin 16.69 c Control - Control- Creosote 25.00 zABCDE 9 month - PF - Creosote 17.24 c 3 Month Control - Tanalith-C 25.04 zABCDE PVAc-D4- Protim- Parafin 17.35 cd Control -PF - Tanalith-C 25.11 ABCDE 6 month - PF - Creosote 18.17 de 6 Month D-VTKA – Creosote 25.19 BCDE PVAc-D4- Creosote 18.46 ef Control – PF- Control 25.20 BCDE PVAc-D4- Tanalith-C 18.99 efg Control- PF 25.45 CDEF PVAc-D4- Tanalith-C 19.16 fgh 6 Month- PF- Control 25.53 DEFG 3 month-PF- Creosote 19.36 ghi 12 Month- PVAc-D4-Control 25.59 DEFG Control - Tanalith-C 19.76 hi Control- Control - Protim- Parafin 25.85 EFG Control- PF - Creosote 19.80 hi PVAc-D4- Control 26.29 FGH 12 Month PF - Tanalith-C 20.12 i PVAc-D4- Tanalith-C 26.43 GH 9 Month PVAc-D4- Creosote 20.27 jk Control- Control 26.75 HI 6 Month PVAc-D4- Creosote 21.20 k 3 Month D-VTKA – Control 26.84 HI 3 Month D-VTKA - Creosote 21.45 k 6 Month Control - Tanalith-C 27.04 HI 9 Month Control – Creosote 21.47 kl 6 Month PVAc-D4- Control 27.51 I 12 Month D-VTKA - Tanalith-C 21.48 klm 12 Month- PF- Protim- Parafin 28.76 J 9 Month PF - Tanalith-C 21.70 klmn 9 Month PF- Protim- Parafin 29.81 K 3 Month Control-Control 22.03 lmno 3 Month PVAc-D4- Control 29.90 K 9 Month D-VTKA - Tanalith-C 22.23 lmno 12 Month D-VTKA - Protim- Parafin 30.06 K 6 Month PVAc-D4- Tanalith-C 22.51 mnop 6 Month PF- Protim- Parafin 30.52 K 3 Month D-VTKA - Tanalith-C 22.56 mnop 9 Month D-VTKA - Protim- Parafin 30.67 K 6 Month D-VTKA - Tanalith-C 22.65 mnopr 3 Month PVAc-D4- Protim- Parafin 31.36 L 3 Month PVAc-D4- Creosote 22.76 mnopr Control - PVAc-D4- Protim- Parafin 32.06 LM 12 Month PVAc-D4-Control 22.90 mnopr 3 Month PF- Protim- Parafin 32.67 M Control- D-VTKA - Creosote 22.93 mnopr Control- PF- Protim- Parafin 34.52 N 3 Month Control - Protim- Parafin 22.95 mnopr 6 Month D-VTKA - Protim- Parafin 35.53 NO 3 Month PF - Control 22.96 noprs 3 Month D-VTKA - Protim- Parafin 35.77 O 12 Month D-VTKA - Control 22.99 oprst Control- D-VTKA - Protim- Parafin 36.62 P 12 Month D-VTKA - Creosote 23.07 oprstu Control- PVAc-D4- Control 36.87 P 6 Month Control - Creosote 23.42 prstuv Control- D-VTKA - Control 40.06 P

2016, Vol. 22, No. 1 (42) ISSN 2029-9230 136138 BALTIC FORESTRY COMPRESSION STRENGTH PERPENDICULAR TO GRAIN CHARACTERISTICS /.../ R. ESEN ET AL. to sea water for 9 months and which were exposed to sea The effect of adhesive type and exposure time on water for 12 months in the same way has been observed in perpendicular compression value is given in Figure 2. interaction. No difference between sample groups, which In Figure 2, the effect of adhesive type and the dura- were exposed to sea water for 6 months and which were tion of the exposition of material to sea on the compres- exposed to sea water for 3 months in the same way, has sion strength perpendicular to grain have been searched. been observed in interaction. However, statistical differ- Among the samples exposed to sea, the best result has ence has been observed among other groups. been observed to be in D-VTKA adhesive. Among the adhesive types, D-VTKA adhesive gave Discussion and Conclusions better results in Scots pine especially after being exposed to sea water (see Figure 2). D-VTKA showed high dry The effect of impregnation materials and exposed and wet strength; resistance to water and damp atmo- time on perpendicular compression value is given Figure 1. sphere; limited resistance to prolonged and repeated wet-

Figure 2. Effect of adhesive type and exposure time on com- Figure 1. Effect of impregnation materials and exposure time pression strength perpendicular to grain on Compression strength perpendicular to grain ting and drying; gap-filling (Vick 1994, Kurt 2006). At According to Figure 1, as to exposure time among the high temperatures, D-VTKA adhesives can be advised as impregnated materials, the highest compression strength the building material used for long term use (Uysal et al. perpendicular to grain value was obtained in control 2008). Lay and Cranley (2003) stated that polyurethane samples. The lowest compression strength perpendicular adhesives have higher bonding strength and higher toler- to grain value was obtained in samples impregnated with ance against humidity. creosote and exposed for 12 months. According to Figure 2, when adhesive type and the According to Figure 1, when the effect of the dura- duration of the exposition of the material on the compres- tion of exposition to sea and impregnation material on sion strength perpendicular to grain is taken into consid- the compression strength perpendicular to grain in sam- eration, it can be observed that the longer the material ples is taken into consideration, it can be observed that is exposed to sea, the better the compression strength of if the material is exposed to sea for a longer period of LVL compared to massive samples is. The rate of de- time, there occurs a decrease in the compression strength crease in massive samples is 52 % in average, 33 % in perpendicular to grain gradually. The rate of decrease in samples laminated with PVAc, 21 % in samples laminated the unimpregnated samples is 36 % in average, 32 % in with D-VTKA, and 16 % in samples laminated with phe- the ones impregnated with protim-paraffin, 25 % in the nol formaldehyde. The highest decrease in compression ones impregnated with Tanalith-C, and 24 % in the ones strength perpendicular to grain values has been observed impregnated with creosote. The highest decrease in com- in unimpregnated samples. When unimpregnated samples pression strength perpendicular to grain values has been are exposed to sea water, there may occur decomposition observed in the unimpregnated samples. When unimpreg- caused by bacteria and fungus. nated wood material is exposed to sea water, there may Phenolic resins are used as binders for exterior in occur decomposition caused by bacteria and fungus. grade plywood and particleboard, which need the superi-

2016, Vol. 22, No. 1 (42) ISSN 2029-9230 139137 BALTIC FORESTRY COMPRESSION STRENGTH PERPENDICULAR TO GRAIN CHARACTERISTICS /.../ R. ESEN ET AL. or water resistance provided by these resins (Pizzi 2003). Kirk, T.K. and Cowling, E.B. 1984. Biological decomposition of Phenolic resins (PF) show complete resistance to hydro- solid wood. In: The Chemistry of Solid Wood. Madison, USA. Chapter 12, p. 455-487. lysis of the C-C bond between the aromatic nucleus and Kurt, Ş. 2006. Change of Some Technological Characteristics of the methylene bridge and, therefore, are used for water Impregnated Laminated Veneer Lumbers (LVL) in Sea Water. and weather resistant glue lines and boards such as water PhD Thesis, Zonguldak Karaelmas University, Turkey. and weatherproof particleboards, OSB, MDF, or plywood Lay, G.D. and Cranley, P. 2003. Polyurethane adhesives. In: Pizzi, A. and Mittal, K.L. (eds.). Handbook of Adhesive Technol- intended for use under weather conditions (Dunky 2003). ogy, 2nd ed., rev. and exp., Marcel Dekker, Inc., New York, p. In addition; Amasra is the area known for wood ma- 704-705. terial is most commonly destroyed by mussels Teredo no- Örs, Y,. Özçifçi, A. and Atar, M. 1999. Klebit 303, Kleıberit 305.0 valis L. In the first 6 months of life these organisms do ve Süper Lackleim 308 Tutkallarının Yapısma Dirençleri [Bonding Strengths of Klebit 303, Kleıberit 305.0 and Super damage more quickly in the perpendicular direction than Lackleim 308 Adhesives]. Turkish Journal of Agriculture and in the next period of their life, when their damage is more Forestry 23 (EK3): 757–762 (in Turkish). observed in the direction parallel to grain, and data on the Pizzi, A. 1993. Wood Adhesives: Chemistry and Technology, Vol.1, compression strength perpendicular to grain shows more Marcel Dekker, New York. Pizzi, A. 2003 Phenolic Resin Adhesives. In: Pizzi, A. and Mittal, resistance in a horizontal course. Consequently, it is said K.L. (eds.). Handbook of Adhesive Technology 2nd ed., rev. and that the use of impregnated LVLs increases their resis- exp., Marcel Dekker, Inc., New York. Chapter 26, p. 573-587. tance against the marine fungus. Polisan. 1999. Desmodur-VTKA. Dilovası. Polisan Inc.: Manufac- turer’s documentation. Gebze, Bolu, Turkey (in Turkish). Skaar, C. 1983. Wood-Water Relationships. In: The Chemistry of References Solid Wood, American Chemical Society, March 20-25, New York. p. 127-172. Adhesive Bonding of Wood 1975. Technical Bull. No. 1512, U.S. Subramanian, R.V. 1984. Bioactive Wood-Polymer Composites. Department of Agriculture, Forest Service, i-v+124 pp. In: Rowell R.M. (ed.). The Chemistry of Solid Wood. Ad- ASTM D 1413– 76. 1976. Standard Test Method of Testing Wood vances in Chemistry series 207. American Chemical Society. Preservatives by Laboratory Soil Block Cultures, Annual Washington, DC, USA. Chapter 7, p. 292 – 305. Book of ASTM Standards, P. 452-460. TS 2472. 1976. Wood - Determination of Density for Physical and Baldwin, R.F. 1995. Plywood and Veneer-Based Products: Manu- Mechanical Tests. Turkish Standards Institute, Ankara, Tur- facturing Practices. (Wood technology books series). Miller key, 10 pp. (in Turkish). Freeman Inc., San Francisco. TS 2473. 1976. Wood - Testing in Compression Perpendicular to Becker, G. 1974. Aspects, results and trends in wood preservation, Grain. Turkish Standards Institute, Ankara, Turkey, 9 pp. (in an interdisciplinary science. Wood Science Technology 8 (3): Turkish). 163-183. TS 3891. 1983. Adhesive polyvinyl acetate emulsions (For Wood). Blomquist, R.F. 1983. Adhesive bonding of wood and other struc- Turkish Standards Institute, Ankara, Turkey. 10 pp. (in Turk- tural materials. In: Clark C. Heritage memorial series on ish). wood, Vol. 3. Educational module for materials science and TS 5430 EN 204. 2003. Classification of Adhesives According to engineering (EMMSE) (R.F. Blomquist, A.W. Christiansen, Bond Strength Used at Wood Industries. Turkish Standards R.H. Gillespie, G.E. Myers, eds.), University Park, PA: Penn- Institute, Ankara, Turkey. 7 pp. (in Turkish). sylvania State University. Uysal, B., Kurt, Ş., Şahin, K.H., Özcan, C. and Yıldırım, M.N. Bozkurt, Y. 1986. Ağaç Teknolojisi [Wood Technology], İ. Ü., Or- 2008. Bonding Strength of Scots Pine Bonded with Different man Fakültesi, Yayın No.: 3403-3480, İstanbul, Turkey (in Adhesive After Aging Test. Technology 11(4): 287-295. Turkish). Vick, C.B. 1999. Adhesive Bonding of Wood Materials. In: Forest Colak, S., Aydın, I., Demirkır, C., Colakoğlu, G. 2004. Some Products Laboratory. 1999. Wood handbook – Wood as an en- Technological Properties of Laminated Veneer Lumber gineering material. Gen. Tech. Rep. FPL–GTR–113. Madison, Manufactured from Pine (Pinus sylvestris L.) Veneers with WI: U.S. Department of Agriculture, Forest Service, Forest Melamine-Added UF Resins, Turkish Journal of Agriculture Products Laboratory. Chapter 9, p. 9-24. and Forestry 28 (1): 109-113. Dunky, M. 2003. Adhesives in the wood industry. In: A. Pizzi, K.L. Mittal (eds.). Handbook of Adhesive Technology, 2nd ed., rev. Received 18 July 2014 and exp., Marcel Dekker, Inc., New York. Chapter 47. Accepted 25 January 2016

2016, Vol. 22, No. 1 (42) ISSN 2029-9230 138140 BALTIC FORESTRY THE EFFECTS OF DIFFERENT LOGGING TECHNIQUES /.../ H. EROĞLU ET AL. The Effects of Different Logging Techniques on the Physical and Chemical Characteristics of Forest Soil

HABİP EROĞLU1*, TEMEL SARIYILDIZ2, MEHMET KÜÇÜK3 and ERHAN SANCAL4 1Department of Forest Engineering, Karadeniz Technical University, 61080 Trabzon, Turkey, 2Department of Forest Engineering, Kastamonu University, 37100 Kastamonu, Turkey. 3Department of Forest Engineering, Artvin Çoruh University, 08000 Trabzon, Turkey. 4Artvin Forest Regional Directorate, 08000 Artvin, Turkey. * Corresponding author. E-mail: [email protected]

Eroğlu, H.*, Sariyildiz, T., Küçük, M. and Sancal, E. 2016. The Effects of Different Logging Techniques on the Physical and Chemical Characteristics of Forest Soil. Baltic Forestry 22(1): 139-147.

Abstract

In this study, we investigated the effects of four timber logging techniques (skyline, skidder, manpower and chute system) on the physical (permeability, field capacity, water holding capacity, bulk density, fine and coarse soil, sand, clay and silt ratios) and

chemical properties (electrical conductivity, organic matter, total lime, P2O5, K2O, Ca, Mg, Na, Fe, Zn, Cu and Mn contents) of for- est soil at two soil depths (0-15 and 15-30 cm) at loading, unloading, skid road, and undisturbed plots. The logging practices, each consisting of three steps, were executed at 12 testing sites in total, where logging through skylines, ground skidding with manpower, skidding with skidders, and sliding within the chute systems were performed. Our results demonstrate that logging by skidder and manpower can have an important influence on soil permeability, bulk density and soil water balance, and these techniques can significantly reduce soil organic matter content and nutrient levels. It was also noted that these two logging techniques constantly removed the litter and humus from the forest floor, reducing the amount of soil organic matter content and nutrients. The removal of organic matter content and nutrients from the soil will also affect soil organisms, which play an important role in regulating organic matter content decomposition rates.

Key words: logging, forest soil, chemical properties, soil damage, Artvin region.

Introduction skylines require less power compared to ground skidding and cause less damage to forest soil, the stand, and the The most difficult and costly stage of wood procure- quality and quantity of logs (Erdaş 1993). ment is logging, when the trees are cut down and hauled When harvesting is not performed using proper plan- to the nearest forest road. Logging is performed using a ning and techniques, it causes severe negative effects on variety of techniques, and it is important to utilize eco- forest soil (Bettinger and Kellogg 1993, Smidt and Blinn conscious, efficient, and the least harmful techniques to 1995, Marshall 2000, Pinard et al. 2000, Quesnel and transport harvested trees to reduce the negative impact on Curan 2000, Croke et al. 1999, Demir et al. 2007, Akay forests. et al. 2007, Makineci et al. 2007, Horn et al. 2007), the A great deal of man and animal power is used in log- planted trees remaining in the stand (Elias 1995, Johns et ging practices in Turkish forestry. The rate of mechanized al. 1996, Jackson et al. 2002, Krzic et al. 2003), seedlings production is fairly high in developed countries compared (Steege et al. 2002, Eroğlu et al. 2007, McDonald et al. to Turkey. The most widely used logging method in forests 2008), wildlife (LeDoux 1997, Scrimgeour et al. 2000) on steep terrain is skidding logs downhill by manpower and logging products (Holmes et al. 2002). As a result, using various manual tools and taking advantage of grav- environmental devastation such as degradation of forest ity (Erdaş 1993). As such, there is substantial loss in the land, negative effects on forest soil, erosion and deterio- quality and quantity of the transported products and heavy ration in water sources occur (FAO 1997). The most ap- damage is inflicted on saplings and planted trees in the log- propriate logging technique, particularly in mountainous ging areas (Acar and Eroğlu 2003, Eroğlu et al. 2009). areas, must be applied for sustainable forestry (Dykstra It is often impossible to use animal power and man- and Heinrich 1992). power under tough and steep highland conditions, and A number of studies on the negative effects of log- thus skylines are used for logging in these areas. Forest ging practices have been conducted in several countries

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(Elias 1995, Elias 1998, FAO 1997, Pinard et al. 2000, Taşlıca Forest District is located between 40°06’ - Steege et al. 2002, Gerwing 2006, Putz et al. 2008); log- 41°12’ north and 41°37’ - 41°46’ east. The research area ging techniques that cause severe environmental damage comprises the conditions of the Eastern Black Sea Region were compared to those that are less harmful, and the with its land structure, climatic conditions, and mountain- most convenient technique according to terrain conditions ous and forested aspects. was determined. Few such studies have been performed in The altitudes of the testing sites range from 1520 to Turkey and particularly in the Artvin region (North-East- 2175 m above sea level, land slopes vary between 40 and ern Turkey), the forested lands of which are present on 100 %, canopy closures vary between 70 and 100 %, and steep terrain. For logging operations in Artvin, manpower, hauling distances range from 100 to 450 m. The aspects skidders and skylines are used widely (Eroğlu and Acar of the testing sites are western, north-western, and south- 2007). This study investigated the effects of four logging western. The hauling direction of logging using man- practices on the physical and chemical properties of soil power was downhill, whereas logging using skidders and in this region. skylines was conducted in an uphill direction (Table 1). Method: In the testing sites and practice areas, in Materials and Methods which logging activities were conducted, soil samples were taken from four soil impact areas, in which: (1) the Study area: Our study area, the Artvin region, has logs to be hauled were loaded (Load), (2) the logs were challenging land conditions for forestry as a result of unloaded (Unload), (3) transportation or ground skidding steep, rugged slopes and the resulting negative environ- had an impact (Transport), and (4) control areas (Con- mental effects during timber harvesting. Artvin is also a trol). In these areas the forest soil is mainly affected by good region in which to compare the negative effects of the transportation of timber. In each testing site, three logging methods because machine-intensive techniques points for soil profile measurements were selected, and are used widely and recently developed plastic chute sys- soil was sampled at two depths for each profile (0-15 and tems have been implemented. 15-30 cm). Accordingly, a total of 288 soil samples were This study was conducted in natural oriental spruce collected. stands of the Taşlıca Forest District (FD) in Artvin For- The physical characteristics (permeability, field ca- estry Enterprise (FE), Turkey. The practices, three steps pacity, water holding capacity, bulk density, percentage for each, were executed at 12 testing sites in total, where of particles d < 2 mm, sand, clay and silt percentages, hy- logging through skylines (S1, S2, S3), ground skidding groscopic moisture content), physicochemical properties with manpower (M1, M2, M3), skidding with skidders (pH, organic matter content, electrical conductivity, total

(T1, T2, T3), and sliding within the chute systems (O1, lime content, and the P2O5, K2O, Ca, Mg, Na, Fe, Zn, Cu O2, O3) were conducted (Figure 1). and Mn levels of the soil samples were identified. The pH

Figure 1. Location of the testing sites

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Table 1. Properties of the testing sites

Testing Ground Transport Altitude, Tree Transport Site Logging Technique Comp. No Slope, Aspect Distance, m Species Direction No % m

M1 99 1520 40 West SP+S+F Downhill 200 M2 Manpower 99 1507 40 West SP+S+F Downhill 200 M3 99 1490 40 West SP+S+F Downhill 200 T1 206 1620 60 South-West S Uphill 100 Skidder T2 206 1612 80 North-West S Uphill 100 (MB Trac 900) T3 249 1600 100 West S+F Uphill 100 S1 104 2175 60 South-West S Uphill 400 Forest Skyline S2 104 2100 50 South-West S Uphill 450 (URUS M III) S3 103 2122 60 South-West S Uphill 450 O1 88 1750 30 North-East S Uphill 250 Chute System O2 88 1800 40 East S Uphill 150 (AcarOLUKPeF50/600) O3 84 1774 35 North-East S Uphill 175

SP: Scots Pine (Pinus sylvestris L.), S: Spruce [Picea orientalis L. (Link.)], F: Fir (Fagus orientalis Lipsky.) of the soil was determined in a 1/2.5 soil-water mixture unloading (0.47 cm h-1) and ground skidding (0.67 cm h-1) (Gülçür 1974). sites compared to the control site (0.93 cm h-1), whereas A one-way ANOVA and Tukey’s HSD test (p = 0.05) soil bulk density values were higher at the loading (1.33 g were used to determine the effects of logging operations cm-3), unloading (1.27 g cm-3) and ground skidding (1.22 on forest soil. All statistical tests were performed using g cm-3) sites compared to the control site (0.91 g cm-3). SPSS® 15.0 for Windows®. Similar effects were also noted for permeability and bulk density, when manpower was used for logging (Table 2). Results The use of skidders and manpower decreased soil permeability values in the subsoil samples (p < 0.001) Variations in the significantly changed physical prop- (Table 2), but had no significant effect on soil bulk densi- erties of the topsoil (0-15 cm) and subsoil (15-35 cm) ty. The percentage of field capacity, water holding capac- components exposed to the various logging techniques ity and soil clay were significantly influenced by skidder are provided in Table 2. In general, the results demon- activities (p < 0.05), but not manpower (Table 2). strate that using either the skyline or chute system for log- Variations in the chemical properties and nutrient ging does not significantly change the physical properties levels of the topsoil (0-15 cm) and subsoil (15-35 cm) of topsoils and subsoils, while using forest skidders and components with different logging techniques are shown manpower influences the physical properties of soil, espe- in Table 3. cially permeability and bulk density (Figure 2). Regarding In general, logging practices performed by either the components of topsoil exposed to skidders, soil per- manpower or skidders significantly affected the organic meability values were lower at the loading (0.53 cm h-1), matter content and soil nutrient levels compared to the

Figure 2. Changes in some physical characteristics of the forest soil according to logging technique and impact area

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Table 2. Soil physical characteristics according to logging technique and impact area, and one-way ANOVA-results

Soil Depth, Impact area Logging Soil Property 0-15 cm 15-30 cm Technique Load Transport Unload Control Load Transport Unload Control

Permeability (cm h-1) 0.71 0.88 0.77 0.94 0.41 0.52 0.29 0.20 Field capacity (%) 27.86 31.79 28.69 25.52 27.15 25.97 24.08 22.91 Water holding capacity (%) 46.43 53.05 56.20 47.30 44.41 40.86 38.30 36.83 Bulk density (g/cm-3) 0.94 1.00 0.83 0.79 1.10 1.19 1.20 1.13 Forest Particles d<2 mm (%) 55.37 67.08 53.95 56.42 67.43 74.78 55.64 54.89 Skyline Sand (%) 64.19 65.65 69.01 63.53 66.41 58.72 63.8 60.73 Clay (%) 20.46 19.03 16.29 19.42 23.23 22.49 19.60 24.63 Silt (%) 15.35 15.32 14.70 17.05 10.36 18.79 16.60 14.64 Hygroscopic moisture (%) 4.75 4.60 5.05 6.50 4.47 4.59 3.82 4.54 Permeability (cm h-1) 0.53a* 0.67b 0.47a 0.93c 0.32a 0.44b 0.34ab 0.58c Field capacity (%) 14.31 19.59 14.61 12.18 11.53a 19.12b 18.31b 12.59a Water holding capacity (%) 24.25 33.98 41.32 31.36 25.54a 35.32b 32.30b 28.66a Bulk density (g cm-3) 1.26b 1.25b 1.34b 0.94a 1.26 1.23 1.24 1.17 Skidder Particles d<2 mm (%) 29.26 47.70 43.55 49.14 47.82 41.56 44.86 52.85 Sand (%) 69.39 69.87 73.55 67.52 70.53 69.49 71.62 65.56 Clay (%) 12.62 13.43 11.94 15.29 12.12a 14.63a 13.25a 18.60b Dust (%) 17.99 16.70 14.51 17.19 17.35 15.87 15.13 15.84 Hygroscopic moisture (%) 3.68 4.42 3.89 3.38 4.10 3.59 3.39 3.10 Permeability (cm h-1) 0.16a 0.23a 0.22a 0.72b 0.18a 0.20a 0.25ab 0.34b Field capacity (%) 39.05 24.34 35.25 26.79 22.94 25.62 24.91 26.08 Water holding capacity (%) 71.38 32.94 39.18 45.26 49.37 41.86 36.27 42.74 Bulk density (g cm-3) 1.33b 1.22ab 1.27b 0.91a 1.26 1.33 1.29 1.23 Manpower Particles d<2 mm (%) 48.44 69.04 53.08 59.35 52.13 60.28 47.72 49.52 Sand (%) 65.61 63.66 63.80 65.97 67.33 58.78 60.55 56.51 Clay (%) 16.23 20.53 24.14 20.47 19.07 22.99 17.67 22.25 Silt (%) 18.16 15.81 12.06 13.56 13.60 18.23 21.78 21.24 Hygroscopic moisture (%) 10.54 9.81 9.49 9.57 9.89 10.79 10.30 10.78 Permeability (cm h-1) 0.69 0.59 0.62 0.96 0.64 0.62 0.54 0.46 Field capacity (%) 28.83 28.47 24.53 27.66 27.08 25.92 25.83 25.92 Water holding capacity (%) 57.89 55.68 58.92 55.92 41.17 46.40 39.23 41.80 Bulk density (g/cm-3) 0.84 0.85 0.87 0.73 1.21 1.24 1.17 1.20 Chute Particles d<2 mm (%) 59.70 69.37 57.20 65.57 59.30 67.90 64.60 58.33 System Sand (%) 62.38 63.04 64.28 63.69 65.17 64.38 64.80 62.25 Clay (%) 21.11 19.99 20.61 20.56 21.03 20.13 19.69 21.50 Silt (%) 16.50 16.97 15.11 15.75 13.80 15.49 15.51 16.25 Hygroscopic moisture (%) 6.09 5.16 5.74 6.52 4.00 4.17 4.59 4.27 * Note: Soil properties with significant differences between treatments printed in bold. Different superscript letters indicate statistical differences of total averages for a soil depth class between impact areas at p < 0.05 (Tukey’s HSD test) forest skyline and chute systems. The concentrations of Discussion nutrients, such as P2O5, K2O, Ca, Mg, Na, Fe and organic matter content in the topsoil and subsoil components were This study has demonstrated that among the four decreased considerably by use of skidder and manpower logging practices studied, skidders and manpower sig- logging techniques (Figure 3). nificantly influence soil physical and chemical properties compared to the skyline and chute system techniques. In

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Table 3. Soil chemical properties and content of nutrients according to logging technique and impact area, and one-way ANOVA-results

Soil Depth, Impact Area Logging Soil Property 0-15 cm 15-30 cm Technique Load Transport Unload Control Load Transport Unload Control

a* b b b pH (H2O) 4.15 4.45 4.54 4.42 4.44 4.59 4.71 4.69 Organic matter (%) 5.05 4.85 5.77 5.46 2.90 2.58 3.16 3.61 Electrical conductivity (µS) 40.1 38.0 37.6 43.3 24.40 28.9 25.1 31.1 Lime (%) 1.30 1.43 1.12 6.88 8.37 1.07 2.00 1.44 -1 P2O5 (mg kg ) 7.11 6.47 8.59 7.18 7.89 4.66 6.61 6.68 -1 K2O (mg kg ) 66.5 205.5 66.8 75.5 40.2 42.2 27.5 56.7 Forest Skyline Ca (mg kg-1) 244.3 645.7 492.3 442.7 238.4 839.9 237.2 497.9 Mg (mg kg-1) 56.3 125.0 114.3 108.8 68.0 178.1 132.7 151.7 Na (mg kg-1) 1.73 4.39 0.65 4.55 0.75 7.49 0.66 6.41 Fe (mg kg-1) 231.6 180.0 138.0 213.8 87.8 107.7 85.8 112.7 Zn (mg kg-1) 2.66 4.22 2.02 4.54 1.71 2.48 1.48 2.35 Cu (mg kg-1) 0.57 0.96 0.53 0.79 0.64 0.97 0.61 0.86 Mn (mg kg-1) 9.42 84.1 7.13 30.3 35.6 55.6 16.4 52.3

pH (H2O) 4.43 4.98 4.66 4.40 4.54 5.04 4.77 4.48 Organic matter content (%) 5.46b 3.94a 5.59b 6.24c 3.29a 3.59a 3.73a 5.03b Electrical conductivity (µS) 40.7 45.8 47.6 52.6 29.0 33.6 31.2 42.6 Lime (%) 2.47 2.67 1.70 1.87 1.97 8.23 5.40 6.57 -1 b a b c b a b c P2O5 (mg kg ) 7.55 5.99 7.25 9.66 6.53 5.70 6.40 8.97 -1 a b b c a c b d K2O (mg kg ) 22.5 42.1 44.5 79.7 46.3 67.4 58.4 85.2 Skidder Ca (mg kg-1) 205.8a 414.6c 332.0b 710.5d 313.2 492.8 333.9 472.2 Mg (mg kg-1) 44.7a 79.8b 82.4b 163.7c 81.2a 85.3a 82.2a 148.5b Na (mg kg-1) 2.54 5.50 5.06 5.42 3.35 0.42 6.11 1.95 Fe (mg kg-1) 194.2 131.3 107.9 175.1 59.6a 94.8b 104.4b 165.6c Zn (mg kg-1) 3.86 3.18 2.42 6.11 1.35a 1.57a 1.90b 3.40c Cu (mg kg-1) 0.80 0.48 0.37 0.37 0.24 0.67 0.45 0.32 Mn (mg kg-1) 27.2b 28.6b 10.5a 59.6c 4.03a 20.5c 13.3b 44.7d

pH (H2O) 5.69 5.46 5.35 5.25 6.04 5.83 5.45 5.77 Organic matter content (%) 5.08b 4.37a 5.53b 7.13c 3.61a 4.32a 3.41a 5.12b Electrical conductivity (µS) 161.9 83.6 96.2 82.7 56.3 99.0 96.9 71.8 Lime (%) 1.50 1.47 3.57 8.07 1.40 1.47 1.40 1.43 -1 c c a b P2O5 (mg kg ) 8.80 8.10 5.98 10.6 5.11 5.33 4.56 7.9 -1 c b a d b b a c K2O (mg kg ) 126.4 50.2 28.8 172.8 81.9 80.0 46.7 164.7 Manpower Ca (mg kg-1) 727.0b 588.2a 694.8b 1329.7c 611.3b 471.0a 1279.0c 1566.0d Mg (mg kg-1) 506.4b 357.4a 489.9b 805.6c 491.0b 389.5b 330.7a 663.0c Na (mg kg-1) 5.33a 11.0b 4.07a 6.91a 22.1a 32.1b 21.1a 35.0b Fe (mg kg-1) 82.6a 150.5b 152.7b 139.0c 43.3 41.9 50 41.7 Zn (mg kg-1) 1.44 1.12 1.29 1.17 0.43 0.38 0.94 0.34 Cu (mg kg-1) 2.18 2.04 1.70 1.86 1.86 1.50 1.43 1.75 Mn (mg kg-1) 40.2 45.4 48.8 43.9 19.9 23.4 16.8 32.9

pH (H2O) 4.48 4.42 4.41 4.49 4.55 4.59 4.62 4.63 Organic matter (%) 6.42 4.45 5.57 5.55 3.44 3.71 3.50 3.66 Electrical conductivity (µS) 42.90 40.43 34.70 40.30 26.53 27.73 27.30 26.17 Lime (%) 1.27 1.43 1.47 1.27 4.27 1.77 2.80 1.63 -1 P2O5 (mg kg ) 8.70 7.97 8.03 7.27 6.37 5.33 6.57 6.43 -1 K2O (mg kg ) 89.30 94.90 72.60 91.00 40.97 52.73 44.00 48.87 Chute System Ca (mg kg-1) 459.83 525.97 516.20 593.57 363.93 608.73 307.90 470.53 Mg (mg kg-1) 90.60 107.52 108.27 112.50 151.60 117.67 191.63 193.03 Na (mg kg-1) 2.67 4.10 2.10 3.70 1.80 4.07 4.43 5.23 Fe (mg kg-1) 204.83 189.90 158.53 189.20 149.40 109.80 118.07 107.97 Zn (mg kg-1) 2.30 4.33 4.57 3.97 2.00 2.37 1.73 1.93 Cu (mg kg-1) 0.77 0.97 0.53 0.97 0.77 1.00 0.80 0.80 Mn (mg kg-1) 17.05 33.78 14.99 38.12 51.47 55.00 45.37 58.33 * Note: Soil properties with significant differences between treatments printed in bold. Different superscript letters indicate statistical differences of total averages for a soil depth class between impact areas at p < 0.05 (Tukey’s HSD test)

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Figure 3. Changes in some chemical characteristics of the forest soil according to logging technique and impact area general, our results are in agreement with those of simi- power, animals, or skidders; these characteristics have lar studies. The properties of both the topsoil and subsoil been investigated previously. For example, Makineci et components, especially permeability, bulk density and al. (2007) analyzed changes in forest soil properties at dif- nutrient concentrations, were significantly affected by ferent distances on ground skidding trails in Abies stands ground skidding both by skidders and manpower tech- and found that clay content, percentage of field capacity niques. In addition, the soil on areas, where the harvested and bulk density decreased significantly at 0-5 and 5-10 spruce logs were loaded and unloaded, was also degraded cm depths of soils. Demir et al. (2007) studied beech and to a considerable extent. We observed that use of a skyline oak stands in the same region and found that ground skid- did not lead to a negative change in the physical char- ding operations increased the percentage of field capacity acteristics of forest soils. Similar studies by Elias (1998) and bulk density of topsoil (0-5 cm), but the same proper- and Bock and Van Ress (2002) showed that hauling logs ties of subsoil decreased markedly. using skylines did not cause major changes in the physical The impact of skidding operations on soil causes soil characteristics of soil due to minor contact of hauled logs compaction. According to Herbauts et al. (1996), these with the ground. impacts led to a 20 % decrease in the total volume of soil Changes in the physical characteristics of soils were pores. As the result, it was noted by Ablan et al. (1994) detected only along the ground skidding trails, which oc- that bulk density of soil increased by approximately 22 %. curred during logging practices performed using man- Conversely, Miller et al. (1996) reported that bulk density

2016, Vol. 22, No. 1 (42) ISSN 2029-9230 144146 BALTIC FORESTRY THE EFFECTS OF DIFFERENT LOGGING TECHNIQUES /.../ H. EROĞLU ET AL. values increased by up to 40 % in similar situations. We et al. 2005, Sarıyıldız and Küçük 2008, Sarıyıldız and detected an increase in bulk density of 42 % using skid- Küçük 2009). Other important sources of organic matter ders and 46 % using manpower. Decreased soil pore size and nutrients are tree roots; Fogel (1983) demonstrated increases water retention in the soil (Ballard 2000), and that the capillary root mass under coniferous forests var- soil compaction causes soil permeability to diminish by ies between 1,000-12,600 kg ha-1. Similar results were 30-50 % (Aust et al. 1998). Dickerson (1976) reported reported by Hendrick and Pregitzer (1993) in thickets that the permeability rates on areas without soil com- composed of a mixture of oak, beech and maple. Whether paction (11.4 cm h-1) decreased in skidder wheel tracks on the soil surface or underground, there is a relationship (1.1 cm h-1). Similar results were reported by Cullen et between the soil organic matter content and nutrient levels al. (1991) and Ballard (2000). In this study, while perme- due to the presence and decomposition of plant residue. ability values decreased by 50 % in areas logged using Besides providing the nutrients necessary for the devel- skidders, this reduction reached 70 % in areas subjected opment of trees within the forest ecosystem and allow- to manpower logging. ing these nutrients to become a source of sustenance in Soil compaction generated by heavy machinery or the cyclic process, litter decomposition is also a source of human activity has a great impact on the structural charac- energy for soil micro- and macro-organisms (Sarıyıldız et teristics, aeration, and water balance of soils, and may af- al. 2005, Sarıyıldız and Küçük 2008). Removal of these fect soil organisms and root development (Makineci et al. sources from the environment as a result of logging or 2007). The changes in these factors can reduce the growth creation of unsuitable conditions for the macro- and mi- of primary roots and their ability to penetrate through soil, cro-organisms will reduce the levels of organic matter and as well as weaken their ability to receive nutrients and nutrients in soil. water (Kozlowski 1999), eventually reducing tree growth (Gebauer and Martinkova 2005). Soil compaction and Conclusions shifts in soil characteristics cause soil fertility to decline by affecting the activities and varieties of organisms that The results of this study demonstrate that timber play significant roles therein by mediating litter decompo- haulage by manpower and skidders negatively affect soil sition, for example (Gobat et al. 1998). chemical properties and nutrient levels. These negative Although it is generally agreed that logging practices impacts will also affect plant nutrient intake, and hence using heavy machinery and humans have significant nega- also plant development. Logging performed using man- tive effects on areas with loamy and slimy soils (Fisher and power and skidders degrade the permeability of both the Binkley 2000), some studies have also reported that these topsoil and subsoil to a considerable degree, while also activities also affect the permeability and bulk density of increasing the bulk density. soils to a significant degree by causing soil compaction The pressure applied to the surface of the soil during in areas, where the content of sand is high (Ampoorter et cable skidding by skidders and ground skidding of logs by al. 2007). Likewise, in this study, logging practices us- humans leads to soil compaction and decreases pore sizes, ing skidders and manpower affected the permeability and thus negatively affecting soil permeability and increasing bulk density of soils to a marked extent despite the rela- bulk density. Over time, these effects will alter the soil tively high content of sand. structural features, water balance, root progression, or- Our results are similar to those of previous studies by ganisms, nutrients and water intake, and thus also affect Makineci et al. (2007) and Demir et al. (2007). Makineci soil fertility and tree development. These factors were not et al. (2007) reported about declined amounts of organic investigated in this study; therefore, further research on carbon and nutrients at depths of 0-5 and 5-10 cm of for- this subject is warranted. est soils exposed to ground skidding at various distances It would be useful to determine the appropriate log- in Abies stands. Logging techniques that apply pressure to ging time and technique to reduce soil losses caused by the soil surface and cause the litter on the surface to drift logging. This involves identifying routes suitable for free away negatively affect both the physical and chemical sliding with manpower and cable skidding by skidder, haul- characteristics of soil (Makineci et al. 2007). Among the ing of logs by skylines, and utilizing chute systems that are three techniques studied here, logging using skylines is least harmful to the environment in thin-scale forests. the most appropriate in forested areas as it does not affect the chemical properties and nutrient levels in the subsoil Acknowledgements and topsoil parts of the soil to any significant degree. The principal sources of organic matter and hence This study is funded by The Scientific and Techno- soil nutrients are leaching into and mixing with the soil as logical Research Council of Turkey (TUBITAK) with the a result of litter decomposition on the surface (Sarıyıldız project number 106O054.

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Building and Environ- Putz, F.E., Sist, P., Fredericksen, T. and Dykstra, D. 2008. Re- ment 42: 3461-3464. duced-impact logging: challenges and opportunities. Forest Eroğlu, H., Öztürk, U.Ö., Sönmez, T., Tilki, F. and Akkuzu, E. Ecology and Management 256: 1427-1433 2009. The impacts of timber harvesting techniques on residual Quesnel, H.J. and Curan, M.P. 2000. Shelterwood harvesting in trees, seedlings, and timber products in natural oriental spruce root-disease infected stands-post-harvest soil disturbance and forests. African Journal of Agriculture Research 4: 220-224. compaction. Forest Ecology and Management 133: 89-113. Fisher, R.F. and Binkley, D. 2000. Ecology and management of Sarıyıldız, T., Anderson, J. and Küçük, M. 2005. Effects of tree forest soils. Wiley, New York. 489 pp. species and topography on soil chemistry, litter quality, and de-

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composition in northeast Turkey. Soil Biology and Biochemis­ Scrimgeour, G.J., Tonn, W.M., Paszkowski, C.A. and Aku, try 37: 1695-1706. P.M.K. 2000. Evaluating the effects of forest harvesting on Sarıyıldız, T. and Küçük, M. 2008. Litter mass loss rates in decidu- littoral benthic communities within a natural disturbance- ous and coniferous trees in Artvin, northeast Turkey: relation- based management model. Forest Ecology and Management ships with litterquality, microclimate, and soil characteristics. 126: 77-86. Turkish Journal of Agriculture and Forestry 32: 547-559. Steege, H.T., Welch, I. and Zagt, R. 2002. Long-term effect of tim- Sarıyıldız, T. and Küçük, M. 2009. Influence of slope position, ber harvesting in the Bartica Triangle, Central Guyana. Forest stand type and rhododendron (rhododendron ponticum) on lit- Ecology and Management, 170: 127-144. ter decomposition rates of oriental beech (Fagus orientalis lip- sky.) and spruce [Picea orientalis (l.) Link]. European Journal Received 16 September 2014 of Forest Research 128: 351-1360. Accepted 08 October 2015

2016, Vol. 22, No. 1 (42) ISSN 2029-9230 149147 BALTIC FORESTRY QUALITY AND BENDING PROPERTIES OF SAWN TIMBER /.../ R. STÖD ET AL. Quality and Bending Properties of Sawn Timber from Commercial Thinnings of Scots Pine (Pinus sylvestris L.)

REETA STÖD*, ERKKI VERKASALO AND JAAKKO HEINONEN Natural Resources Institute Finland (Luke), Yliopistokatu 6, FI-80100 Joensuu *Corresponding author: Reeta Stöd, Tel. +358 29 532 6000; [email protected]

Stöd, R., Verkasalo, E. and Heinonen, J. 2016. Quality and Bending Properties of Sawn Timber from Commercial Thinnings of Scots Pine (Pinus sylvestris L.). Baltic Forestry 22(1): 148-162.

Abstract

In this study, the visual characteristics and static bending properties of Scots pine (Pinus sylvestris L.) sawn timber were de- termined using the material collected from thinning and final-felling stands in eastern Finland. The quality of boards was assessed based on the Nordic visual strength grading rules for timber, and the bending strength, and modulus of elasticity were determined according to the European standard test EN 408. Based on the visual strength grading, the majority of boards met the requirements of the visual grade T1, whereas the highest grade T3 was achieved by less than 10% of the boards. The bending strength and modulus of elasticity of sawn timber from the first thinnings were 42.0 MPa and 10.2 GPa, and those from the second thinnings 52.6 MPa and 12.8.GPa, respectively. The distribution of theoretic strength classes indicated a strong focus on C30 or higher for the material from the second thinnings, whereas the strength classes of C24 or lower were most common for the material from the first thinnings. Re- garding the bending properties, the sawn timber from the butt logs of the first-thinning trees was comparable with that of the middle or top logs from later cuttings. The strength and modulus of elasticity of the first-thinning material were relatively low, whereas the Scots pine sawn timber from the second commercial thinnings may be comparable with that from the current final fellings.

Key words: bending strength, modulus of elasticity, visual strength grading, Pinus sylvestris L., sawn timber, structural pro­ ducts, thinning.

Introduction The significance of thinning forests as a timber re- Scots pine (Pinus sylvestris L.) is increasingly used source, and the utilisation of thinning wood in mechanical for structural wood products, such as sawn timber and wood processing for construction timber and further-pro- glued laminated timber in columns, beams, roof trusses, cessed building products, are increasing. In Finland, for and joists. In construction uses, timber must meet certain example, according to the calculations of sustainable re- requirements of strength, stiffness and density, as well as covery of industrial roundwood and energywood based on dimensional and shape stability, and have an even mois- the 11th National Forest Inventory (NFI), the proportion of ture content (Madsen 1992, Glos 1995, Hoffmeyer 1995, merchantable timber harvested in thinning forests is ex- Johansson 2003). To guarantee the required level of struc- pected to increase from 26% to 36% of the total recovery tural safety for the users, the properties of timber must be during the period 2010–2039 (Salminen 2014). Nowadays, determined reliably. Grading into strength classes, which circa 60% of the forest land area is covered by young and express the load-carrying capacity of the products, allows advanced thinning stands; the change in the age structure the allocation of the pieces of sawn timber for the most of the Finnish forests towards the younger development suitable end-use applications. classes is due to the intensive draining of peatlands in the Bending is the most important mode of stress for struc- 1960s and 1970s, and the accelerated regeneration of old- tural timber. Accordingly, the strength classes of sawn tim- growth forests since the 1950s. In 2012, the first thinnings ber are determined by the density and the ability of a mem- were carried out on 190,300 hectares and other thinnings ber to resist bending, that is, bending strength and stiffness on 288,500 hectares, whereas a decade earlier the cover- (Desch 1981, Finnish Standards Association 2010, Hanhi- age was 175,000 hectares and 162,200 hectares, respec- järvi et al. 2005). The bending properties are easy to mea- tively (Finnish Forest Research Institute 2013). During sure, although, compared to other standard tests, more com- the current 10-year period, the recommended area of first plicated to analyse as bending results in a combination of thinnings is 2.2 times the area carried out during the pre- three-dimensional tension, compression, and shear strains vious period (Packalen et al. 2015). (Bodig and Jayne 1982). In addition to defects, density, Cuttings in thinning forests produce mainly pulp- moisture content and temperature of wood, and loading time wood, although the use of thinning wood as forest energy is affect the bending properties of sawn timber (Desch 1981). also increasing. The yield of logs and small-sized logs from

2016, Vol. 22, No. 1 (42) ISSN 2029-9230 148150 BALTIC FORESTRY QUALITY AND BENDING PROPERTIES OF SAWN TIMBER /.../ R. STÖD ET AL. thinning forest is limited, concentrating rather on the later cording to their silvicultural status as first-thinning, thinnings than on the first thinnings. The dimensions of second-thinning, and final-felling stands, respectively small-sized logs are those between the logs and pulpwood, (Table 1). The stands were located on mineral soils and thus varying notably depending on the receiving sawmill. drained peatlands (transformed types), due to which the For instance, the minimum diameter of 10 cm and length of variation in soil fertility was notable, from the Myrtillus 28 dm have been accepted for small-sized logs in Finland. type to the dwarf-shrub transformed type (Cajander 1949, From the thinnings in 2012, the volume of round- Paavilainen and Päivänen 1995). In each stand, the basic wood trade from standing sales was 1,236,000 m3 for pine properties, such as breast-height diameter (dbh), height logs and small-sized logs, and 842,000 m3 for spruce logs (h), and branch limits, were measured of circa 40 trees and small-sized logs (Finnish Forest Research Institute from a sample plot with the minimum area of 200 m2. Ten 2013). Thus thinnings produced 26% of the total volume sample trees were felled from each stand, representing the of pine logs, and 14% of the volume of spruce logs from dbh-distributions of the trees on the stands. From a sam- the standing sales of private forests. The Finnish wood ple tree, at least one 2.5-m-long log with the minimum products industry utilises approximately two million cu- diameter of 8 cm (over bark) had to be obtained. bic metres of domestic small-sized logs annually (Finnish The felled sample trees were cut into bolts down to Forest Research Institute 2013). In the pine sawmills, the the top diameter of 8 cm. In cross-cutting, no commer- proportion of small-sized logs of the total wood consump- cial bucking instructions were followed. From the base tion is approximately 16 %, and in the spruce sawmills of each log, a 3-cm-thick disc was sawn for determining 5-6 % (Finnish Forest Research Institute 2013). Sawn the wood properties, such as growth ring width. The stem timber from small-sized logs may be used in the prod- part up to the height of 4 m (±0.5 m) was classified as the ucts requiring high visual and technical quality, such as in butt log section, the stem part from 4 to 8 m (±0.5 m) as construction and in furniture, as well as in the non-visible the middle log section, and the rest of the stem down to or low-quality products. In yard equipment, small-sized the minimum top diameter as the top log section. From round timber is used, for instance, as poles and in fences. the first thinnings, 48 butt logs, 28 middle logs, and 6 top The aim of this study was to determine the visual logs were obtained, and from the second thinnings, 65 quality, bending strength (MOR), and modulus of elastic- butt logs, 52 middle logs, and 56 top logs. In addition, 39 ity (MOE) of Scots pine (Pinus sylvestris L.) sawn timber butt logs, 39 middle logs, and 103 top logs were obtained from commercial thinnings, and, furthermore, to study the from the final fellings (Figure 1). effects of different stand and tree characteristics on the The logs were sawn through-and-through, and edged strength properties. As a reference, sawn timber from final into boards with the dimensions of 50×50 mm, 50×75 fellings was studied. mm, and 50×100 mm (Figure 2). Due to the small size of the logs, most of them did not enable more than one board Material and Methods from both sides outwards from the pith; thus the majority of boards represented the centre yield. The 50×100-mm Material boards were most often obtained from the final fellings The data for the study were collected from twelve and the butt logs. The distributions of the smaller boards Scots pine dominated stands in the North Karelia region were relatively even between the stand types and log sec- in eastern Finland. The forests were young and advanced tions. The boards were stored outdoors in sticker-stacks thinning stands, and mature stands, here described ac- sheltered until the measurement of their quality.

Table 1. Characteristics of study stands and sample trees

Stand number Stand type Site type Stems/ha Age, yrs Dbh, cm h, m 1 First thinning Myrtillus type 1750 30 13.3 11.9 2 First thinning Myrtillus type 1850 36 14.3 13.2 3 First thinning Vaccinium type 2250 37 12.2 12.4 4 First thinning Vaccinium type 2350 50 13.6 15.4 5 First thinning Vaccinium vitis-idaea transformed type 1343 35 12.2 11.3 6 First thinning Vaccinium vitis-idaea transformed type 1364 50 15.7 15.5 7 Second thinning Myrtillus type 1500 68 22.4 21.3 8 Second thinning Vaccinium type 1100 66 20.9 21.6 9 Second thinning Calluna type 1600 70 14.6 15.4 10 Second thinning Dwarf-shrub transformed type 1833 90 15.5 14.6 11 Final felling Myrtillus type 375 85 26.3 23.0 12 Final felling Myrtillus type 500 75 30.4 27.4

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Figure 1. Top diameter distributions of the logs, according to the stand type

Figure 2. Number of boards, ac- cording to their dimensions, log sections, and stand types

Methods over a one-metre range in the middle of the board. The Selected visual properties of the boards were deter- length and width of shakes, resin and bark pockets, scars, mined in order to characterise their overall quality as po- top breaks, reaction wood, and decay were measured, and tential commercial wood products for construction. Here, the occurrence of blue stain was recorded. Growth ring the size, location, and number of knots, distortions, slope width was determined microscopically from the discs of grain, wane, shakes, resin and bark pockets, scars, top sawn from the base of each log; the mean calculated for breaks, reaction wood, and decay were taken into account. the discs represented the average growth ring width of the The degrees of distortions, bow, spring, cup, and twist boards between the upper and the lower disc. were measured as the largest deviation from the plane nor- Knots were classified as sound, dead, bark-ringed, mal (Finnish Standards Association 2010), and the slope rotten, loose, encased, spike, vertical, and pin knots, and of grain as the largest deviation of the grain angle, both their size and location in the boards were measured. Spike

2016, Vol. 22, No. 1 (42) ISSN 2029-9230 150152 BALTIC FORESTRY QUALITY AND BENDING PROPERTIES OF SAWN TIMBER /.../ R. STÖD ET AL. knots were classified as edge knots and vertical knots as I = second moment of area (mm4), and top breaks. Knot sum was determined on a range equal to w2–w1 = increment of deformation (mm). the width of the board. The weakest point of each board was determined visually, and its distance from the butt- The MOR and MOE were adjusted to the moisture end of the board was measured. content of 12% using the equations (Boström 1994): Based on the knots and other defects, the boards were graded visually into grades T0–T3, in accordance with the , (4) Nordic visual strength grading rules (Finnish Standards Association 2010). The bending strengths in the grades T3, T2, T1, and T0 are 30 MPa, 24 MPa, 18 MPa, and 14 , (5) MPa, respectively. Hence, T3 corresponds roughly to the strength class of C30, T2 to C24, T1 to C18, and T0 to C14. where

The boards were conditioned in a standard envi- fm,12 = bending strength at MC 12%, ronment (20 ± 2°C, RH 65 ± 5%) to achieve a constant E12 = modulus of elasticity at MC 12%, moisture content (MC). The MC was measured from each ω = MC, %, fω, and board with an electronic moisture meter. The MC of every Eω = bending strength and modulus of elasticity at tenth board was determined using the oven-dry method, the MC of ω%. according to which the true MC of the boards at the test conditions was on average 13%. The measured MC was The characteristic values of strength, modulus of approximately 1.3 percentage units lower than that given elasticity, and density were calculated for each stratum by the oven-dry method. Thus, the MC (%) of each board as stated in the standard SFS-EN 384 (Finnish Standards at the time of test was adjusted by means of the following Association 2010). The theoretic strength class of each linear regression model: unsorted stratum was determined based on the limiting values given in the standard SFS-EN 338 (Finnish Stan-

MCadjusted = 5.65 + 0.628 × MCmeasured , (1) dards Association 2010). The linear mixed model approach was used to study 3 The air-dry density (ρ12, kg/m ) of each board was the sources of variation at different levels in bending determined after weighing, and measuring its dimensions. strength and modulus of elasticity of sawn timber. The The density values were adjusted to the MC 12 % accord- linear mixed models with 3-level hierarchical random ef- ing to the standard methods (Finnish Standards Associa- fects were fitted for MOR and MOE, using IBM SPSS tion 2010). Statistics Software. Factors such as the stand type (first The tests of bending strength and local modulus of thinning, second thinning, final felling), site type (Myrtil- elasticity were carried out as edgewise four-point bend- lus type, Vaccinium type, Calluna type, Vaccinium vitis- ing, according to the standard EN 408 (Finnish Standards idaea transformed type, dwarf-shrub transformed type), Association 2003). When possible, the visually deter- log section (butt log, middle log, top log), board dimen- mined weakest point of the board was placed centred sion (50×100 mm, 50×75 mm, 50×50 mm), wood density, between the loading points, and tensile stress during the growth ring width, and tree age were entered in the LMMs test was applied on the weaker one of the edges. Bend- as fixed effects. The pairwise interactions of the fixed fac- 2 ing strength (MOR) (fm, Mpa = N/mm ) and modulus of tors were tested, as were the interactions among 3 inde- 2 elasticity (MOE) (Em, Gpa = kN/mm ) were calculated as pendent factors. The stand, tree, and log were included follows (Finnish Standards Association 2003): in the models as hierarchical random factors. The model assumptions of the final models were checked using re- , (2) sidual plots. In the best fit model for MOR, the stand type, site type, log section, board dimension, wood density, and , (3) growth ring width were entered as fixed factors (Equation 6). The interaction between site type and wood density where was noted significant, whereas the interactions among 3 a = distance between the loading position and the independent fixed factors were insignificant. nearest support, mm,

Fmax = maximum load, N, MOR = b0 + site + type + section + dim + 3 W = section modulus, mm , + b1density + + bsitedensity + b2grw + stand +

l1 = span, mm, + tree + log + ε, (6)

F2–F1 = increment of load, N,

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where Results MOR = bending strength of a board,

b0 = intercept, Quality and visual strength grading of sawn timber site = forest site type, In the boards from thinnings, the largest knot diam- type = development class of the stand, eters were smaller than 30 mm (Table 2). The maximum section = log section, diameters of sound and dead face and edge knots, bark- dim = board dimension, ringed knots, and the knot sum varied statistically signifi-

b1 = regression coefficient for density, cantly among the stand types, being, in general, larger in

bsite = difference between b1 and the regression coef- the final fellings than in the other stand types. The knot ficient for a site, sum was smallest in the boards from the second thinnings. density = basic density, When comparing the sizes of dry, rotten, and bark-ringed

b2 = regression coefficient for growth ring width, knots, they were noted to be the smallest in the butt logs. grw = growth ring width, The variation of knot diameters between the board dimen- stand = forest study stand (random effect), sions was smaller in the final fellings than in the other tree = sample tree within a stand (random effect), stand types. Generally, the knot diameters increased along log = individual log cut from a sample tree (random with the board dimensions. effect), Concerning the deformations, bow was more com- ε = error term. mon and, according to the analysis of variance, somewhat In the best fit model for MOE, the stand type, wood larger in size in sawn timber from the first thinnings than density, and knot sum were included as fixed factors from the second thinnings or the final fellings (Figure 2). (Equation 7). No significant interactions between fixed In addition, bow was larger in the final felling boards than factors were noted. in the second-thinning boards. The most common defects noted in the boards were slope of grain, top breaks, and

MOE = b0 + type + b1density + b2knot + drying shakes. Slope of grain was found in almost every + stand + tree + log + ε, (7) board, and it was somewhat steeper in the final fellings than in the first thinnings or the second thinnings (Figure where 3). Top breaks were longer in the boards from the first MOE = modulus of elasticity of a board, thinnings than in those from the other stand types, but no

b0 = intercept, statistically significant differences among the stand types type = development class of the stand, were found. Drying shakes, in turn, were longer and more

b1 = regression coefficient for density, common than the other types of shake in all stand types, density = basic density, and found in about 50% of the boards.

b2 = regression coefficient for knot sum, According to the Nordic visual strength grading rules knot = knot sum, for sawn timber, the proportion of boards in the highest stand = forest study stand (random effect), grade T3 was equal in the second thinnings and in final tree = sample tree (random effect), fellings, and somewhat lower in the first thinnings (Figure log = individual log cut from a sample tree (random 4). However, the proportion of boards allocated to the two effect), best grades, T2 and T3, was markedly higher in the first ε = error term. thinnings than in the later cuttings. Most of the boards met the requirements of the grade T1, whereas the proportion

Table 2. The diameters, types, and locations of the largest knots, and the knot sums, according to the stand type and board dimension

Stand type Board dimensions Largest knot Knot sum, mm size/diameter/type/location First thinning 50×50 mm (n=36) 26 mm/sound/edge 49 50×75 mm (n=15) 22 mm/sound/face 54 50×100 mm (n=37) 29 mm/rotten/face 54 Second thinning 50×50 mm (n=37) 23 mm/sound/edge 44 50×75 mm (n=18) 24 mm/sound/face 46 50×100 mm (n=123) 26 mm/sound/face 41 Final felling 50×50 mm (n=23) 44 mm/dead/edge 52 50×75 mm (n=14) 39 mm/bark-ringed/edge 51 50×100 mm (n=184) 29 mm/sound/face 54

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of boards allocated to the lowest grade T0 was at the same level in the first thinnings and in final fellings, but lower in the second thinnings. The 50×50-mm boards were mostly graded to T2, and those with the larger dimensions to T1. The visual strength grades of the smallest pieces of sawn timber were determined mainly by slope of grain, ring shake, and top break, whereas the strength grades of larger sawn timber dimensions were most affected by the face and edge knots, and slope of grain. Density, bending strength, and modulus of elasticity Comparing the stand types, the first thinnings pro- duced sawn timber with the lowest density, MOR, and MOE (Table 3). The properties of sawn timber from the second thinnings were somewhat better than those of the sawn timber from the final fellings. The variation of bending properties was notable; calculated from the entire data, the coefficients of variation (CV) of MOR and MOE were 36% and 27%, respectively. Density, MOR, and MOE decreased from the butt log section to the top log section. Roughly, the butt log section of the first-thinning trees corresponded to the middle and top log sections of the second-thinning and final-felling trees. The variation in the studied properties, especially in Figure 3. The sizes of deformations and defects (mm), accor­ density, was generally higher in the butt log section than ding to the stand type in the upper log sections.

Figure 4. Visual strength grade distributions of the pieces of sawn timber, according to the stand type

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The structure of study material was uneven among In the linear mixed model analysis for MOR, the the site types, the majority of boards originating in Myrtil- stand type was entered as a fixed factor, despite it being lus type forests (Table 4). Based on the arithmetic values, statistically insignificant (p = 0.493) (Equation 6). Other both MOR and MOE were highest on Calluna type, along fixed factors in the model were the site type (p = 0.002), with the highest wood density. log section (p = 0.002), board dimension (p = 0.044), Density, MOR, and MOE were highest in the larg- wood density (p ≤ 0.001), growth ring width (p ≤ 0.001), est boards (50×100 mm), which typically represented the and the interaction term of the site type and wood density centre yield of butt logs (Table 5). Density and MOE of the (p = 0.002). 50×75-mm boards were higher than those of the 50×50- Based on the estimated marginal means (EM- mm boards, whereas MOR in the 50×50-mm boards was MEANS), the bending strength of boards varied accord- at the same level with that of the 50×100-mm boards. ing to the forest development classes, i.e. stand types, be-

th Table 3. Means, standard deviations, and the 5 percentiles of density (ρ12), MOR (fm,12), and MOE (E12), according to stand type and log section

3 ρ12, kg/m fm,12, MPa E12, GPa Stand type Mean Std. dev. 5th per- Mean Std. dev. 5th per- Mean Std. dev. 5th per- Log section centile centile centile First thinning Butt log (n=54) 478.1 43.6 411.7 44.8 17.2 21.1 10.8 3.2 6.2 Middle log (n=29) 452.1 26.9 404.3 38.6 13.5 20.1 9.3 2.5 4.9 Top log (n=5) 433.7 34.6 n/a 32.3 13.4 n/a 8.3 2.8 n/a Total (n=88) 467.0 40.8 398.9 42.0 16.1 21.4 10.2 3.0 5.5 Second thinning Butt log (n=69) 531.2 53.1 450.9 64.2 12.5 44.0 14.8 2.5 9.9 Middle log (n=53) 482.2 37.4 430.3 48.8 11.9 30.7 12.3 2.3 8.2 Top log (n=56) 462.7 34.5 410.1 41.8 12.9 21.9 10.9 2.7 7.3 Total (n=178) 495.0 52.5 423.7 52.6 15.7 28.7 12.8 3.0 7.7 Final felling Butt log (n=66) 514.3 44.2 434.7 56.1 16.5 25.9 13.5 2.9 8.6 Middle log (n=48) 465.7 33.3 411.9 39.7 14.6 19.6 11.7 2.6 7.2 Top log (n=107) 460.1 24.2 413.9 36.4 9.8 20.6 10.2 2.5 6.8 Total (n=221) 477.5 41.0 418.6 43.0 15.7 21.6 11.5 3.0 7.2 All (n=487) 482.0 46.6 418.2 46.3 16.5 23.4 11.7 3.2 7.1

th Table 4. Means, standard deviations, and the 5 percentiles of density (ρ12), MOR (fm,12), and MOE (E12), according to site type

3 ρ12, kg/m fm,12, MPa E12, GPa Site type Mean Std. 5th per- Mean Std. 5th per- Mean Std. 5th per- dev. centile dev. centile dev. centile Myrtillus type (n=308) 474.1 41.7 415.6 42.7 15.4 21.3 11.4 3.1 6.8 Vaccinium type (n=96) 491.1 45.7 423.7 52.8 15.6 29.5 12.5 3.2 7.4 Calluna type (n=25) 546.5 61.1 437.8 65.8 12.9 41.7 14.9 2.5 9.7 Vaccinium vitis-idaea transformed type (n=34) 465.7 37.2 397.0 42.0 14.8 23.5 10.4 2.8 6.1 Dwarf-shrub transformed type (n=24) 503.7 39.5 456.5 52.4 16.2 29.1 12.1 3.0 6.7

th Table 5. Means, standard deviations, and the 5 percentiles of density (ρ12), MOR (fm,12), and MOE (E12), according to board dimension

3 ρ12, kg/m fm,12, MPa E12, GPa Board Mean Std. 5th per- Mean Std. dev. 5th per- Mean Std. 5th per- dimension dev. centile centile dev. centile

50×50 (n=38) 473.4 44.8 405.1 46.1 17.2 21.9 10.1 3.3 5.5 50×75 (n=13) 476.0 44.5 418.5 41.1 13.7 21.8 11.0 2.8 7.0 50×100 (n=138) 485.3 47.1 424.4 47.1 16.5 23.9 12.3 3.0 7.9

2016, Vol. 22, No. 1 (42) ISSN 2029-9230 154156 BALTIC FORESTRY QUALITY AND BENDING PROPERTIES OF SAWN TIMBER /.../ R. STÖD ET AL. ing the highest in the boards from the second thinnings, difference in MOR between the middle and top logs was whereas the strength levels of the first-thinning and final- statistically insignificant. The EMMEANS for different felling boards were relatively even. The pairwise com- board dimensions strongly indicated lower MOR values parisons between site types indicated markedly higher for the 50×75-mm boards than for the other dimensions. MOR of boards originating in the Calluna type mineral The bending strength decreased with increasing growth soils. The Calluna type forests were included in the study ring width, and the highest MOR values were noted for material from the second thinnings only. However, the in- trees with maximum 1.7-mm average growth ring width teraction of stand type and site type was noted insignifi- (Figure 5). Again, the growth ring width had the strongest cant in the LMM. A strong positive association between effect on the MOR of first-thinning boards. density and MOR was noted on all site types. The wood The stand type was entered as a fixed factor in the density as an individual fixed factor had a positive effect linear mixed model for MOE, even though it was found on bending strength (Figure 5). Changes in density and statistically insignificant (p = 0.065) (Equation 7). The growth ring width affected MOR most strongly in the first other fixed factors included in the model were the wood thinnings. With the low level of wood density, MOR was density (p ≤ 0.001) and the knot sum (p ≤ 0.001). somewhat higher in the second thinnings than in the other The estimated marginal means for the stand types stand types (Figure 5). As expected, the pairwise com- indicated the highest modulus of elasticity in the boards parisons showed the MOR to be markedly higher in the from the second thinnings, and the lowest one in those butt logs than in the upper parts of the stem. Instead, the from the final fellings. Expectedly, the modulus of elas-

Figure 5. Relationships of MOR (MPa) and MOE (GPa) with density (kg/m3), growth ring width (mm), and knot sum (mm), according to stand type

2016, Vol. 22, No. 1 (42) ISSN 2029-9230 157155 BALTIC FORESTRY QUALITY AND BENDING PROPERTIES OF SAWN TIMBER /.../ R. STÖD ET AL. ticity increased along with the increasing wood density thinnings, and 6% in the final fellings. In the first thin- (Figure 5). In the boards from the first-thinning stands, the nings and final fellings, the proportion of boards with the changes in density had a stronger effect on MOE than on bending strength of 30–39 MPa was the largest, whereas the other stand types. Moreover, the knot sum had a nega- the second-thinning boards most often had the strength tive effect on MOE. The modulus of elasticity was low of 60 MPa, or even higher. Furthermore, about 17% of especially in the boards with the knot sum larger than 50 the first-thinning and final-felling boards had a very high mm. Based on the regression lines, the knot sum affected bending strength of at least 60 MPa. MOE more dramatically in the second-thinning boards Based on the characteristic values of strength, den- than in those from the other stand types. sity, and modulus of elasticity, the unsorted sawn timber Boards with very low strength were obtained from from the first thinnings and final fellings was theoretically the first thinnings only (Figure 6). Where the other stand graded to C18 and that from the second thinnings to C24 types were concerned, the bending strength of sawn timber (Table 6). As entire populations, sawn timber from the was 18 MPa, at minimum. Only 2% of boards remained second thinnings was graded to C24, and that from the below 24 MPa in the second thinnings, 11% in the first other stand types to C18. Sorting by log section raised the

Figure 6. Bending strength distribution of the boards, according to the stand type

Table 6. Theoretical strength classes of the strata for stand type, log section, and cross-section size (Finnish Standards Association 2010)

1st 2nd Final Butt log Middle log Top log 50×50 50×75 50×100 thinning thinning felling

1st thinning C18 2nd thinning C24 Final felling C18 Butt log C16 C35 C24 C22 Middle log C18 C30 C18 C18 Top log C16 C20 C18 C18 50×50 C16 C16 C20 C22 C14 C16 C16 50×75 C18 C18 C20 C18 C20 C18 C18 50×100 C20 C30 C18 C22 C20 C18 C22

2016, Vol. 22, No. 1 (42) ISSN 2029-9230 156158 BALTIC FORESTRY QUALITY AND BENDING PROPERTIES OF SAWN TIMBER /.../ R. STÖD ET AL. strength classes of the butt logs and middle logs of second than those of the smaller board dimensions. Thus, in some thinnings into C35 and C30, and the butt logs of final fell- strata the characteristic values for defining the theoretical ings into C24. As a whole, sawn timber from the butt log strength classes were calculated for a smaller sample than section corresponded to the strength class C22 and that the minimum sample size stated in the standard. from the upper stem parts to C18. In general, the 50×50- The method of determining the local modulus of mm boards fell into the strength class C16, the 50×75-mm elasticity has been noted to have shortcomings in measur- boards to C18, and the 50×100-mm boards to C22. ing the deflection, and thus, in producing accurate results Comparing the theoretical strength classes (C) with (Boström 1999, Holmqvist and Boström 2000). The meth- the visual strength grades (T) indicated that the visual od is sensitive to the experimental setup; stiffness, espe- strength grading somewhat underestimated the prop- cially, is responsive to the duration of loading, and thus, erties of boards. In general, approximately 74% of all limitations of the long-term deflection must be applied in boards achieved a higher theoretical strength class than the design (Desch 1981). Boström (1999) compared the indicated by the visual strength grade. As an exception, local and global methods, and noted a significant differ- 42% of the boards graded into T2 were noted to fall into ence between the two (Standards Australia 1992, Euro- lower theoretical strength classes; especially where the pean Committee for Standardization 1995, American first thinnings were concerned, 64% of the boards had a Society for Testing and Materials 2005). Factors such as lower strength class than the C24 indicated by the visual the length between reference points in the deformation strength grade T2. measurement, timber quality, and shear deformations af- fected the ratio between the results of the local and global Discussion and conclusions method. In the test pieces with small depths, the size of a defect in relation to the distance between the reference The study stands represented the typical range of points was larger than in the test pieces with large depths. commercial forests in the geographical area in question, Thus, it was noted that the effect of the critical defect on the site fertility varying from the Myrtillus type on mineral the modulus of elasticity was more significant for the lo- soils to the dwarf-shrub transformed type on drained peat- cal method than the global one. The modulus of elasticity lands. The forest management practice recommendations is somewhat underestimated in the global method due to presume thinnings in commercial forests at certain phases the shear deformations, which should be taken into ac- of the rotation period. Especially the first commercial thin- count, when the deformation is measured as the mid-point nings principally aim at improving the quality of forest for deflection relative to the supports. For instance, in the growth, yield, and recovery of desired timber assortments study by Hanhijärvi et al. (2005), the average modulus in the future cuttings. The recommended thinning method of elasticity for Scots pine was 12.1 GPa, when measured for Scots pine forests is the thinning for quality, in which locally, and 11.8 GPa, when measured globally. Piter et the smallest trees, and trees with poor external quality, are al. (2003) noted a difference of 6–7% between the local removed. Thus, the yield of saw logs is often modest in and global modulus of elasticity of Argentinean Eucalyp- first thinnings, and, depending on the general quality of the tus grandis, the first-mentioned giving the higher values. forest, the quality of sawn timber can be markedly lower The majority of boards met the quality requirements than in mature forests. In the latter one or two thinnings, of the visual strength grade T1, whereas the highest grade sawn timber with higher quality can be expected (Kel- T3 was achieved by less than 10% of all boards. The boards lomäki et al. 1992, Verkasalo 2002, Stöd et al. 2006). This mainly represented the centre yield of the logs, owing to is due to the fact that, at these stages of rotation period, the which the knot quality of boards was good, especially in growing stock should be a result from tree selection for the material from the first thinnings. However, also the timber quality. In this study, each felled sample tree was distortions were the most extensive in the boards from the required to contain at least one small-sized log, and thus first thinnings, which may indicate problems in the further the quality of sample trees may have been somewhat high- processing, especially in drying. The notable occurrence er than the quality of trees removed in actual thinnings, of bow in the first-thinning boards, as well as in the final- especially in the low or average-quality forests, or in for- felling boards, might be explained by the juvenile-wood ests with smaller average stem size, such as on peatlands. effect, as the exceptional shrinkage properties of juvenile The structure of current study material was uneven, since wood are known to cause distortions. Here, besides the the number of logs and boards with different dimensions young wood material from the first thinnings, most of the varied markedly between the stand and site types. For in- final-felling boards were sawn from the upper parts of the stance, only few boards representing the top log were ob- stem, i.e., from the juvenile-wood area. Since the quality tained from the first-thinning stands, whereas about half of of boards was assessed after an indefinite period of stor- the final-felling boards were from the top log section. The age outdoors, the board deformations are not comparable number of 50×100-mm boards was also markedly higher with the results for artificially dried sawn timber.

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The research on sawn timber has concentrated main- In this study, the first thinnings provided sawn tim- ly on the larger logs from final fellings, and there are only ber with the lowest MOR and MOE, whereas the mate- a few published studies concerning the properties of tim- rial from the second thinnings provided the highest. The ber originating in thinning forests. The pith-enclosed tim- properties of sawn timber from final fellings lay between ber from thinnings has been studied by Boren (2001) and the other two stand types. However, when comparing the Fernández-Golfin et al. (2007). Comparing their results stand types, their different growth-affecting characteris- showed that despite the similar level of density, the MOR tics should be taken into account. The final-felling stands and MOE of machine-rounded Scots pine were markedly were located solely in the most fertile site type, while the higher than those of laricio pine (Pinus nigra Link.) (Bo- second-thinning stands were mostly poor in nutrients. ren 2001, Fernández-Golfin et al. 2007). Both studies This was indicated also by the growth rate of the trees; the concluded, however, that based on the bending proper- average growth ring width of 1.7 mm, at the stump height, ties, the pith-enclosed timber from thinnings was suitable was measured for the final-felling trees, 1.2 mm for the for structural use. Earlier, the bending properties of round second-thinning trees, and 1.8 mm for the first-thinning timber have been noted to be 5–15% higher than those of trees. The average age of the felled sample trees was 44 sawn timber, the difference being a result of the negative years in the first-thinning stands, 85 years in the second effect of mechanical tooling on the outer wood fibres of thinnings, and 82 years in the final-felling stands. Thus, sawn timber (Boren and Barnard 2000). Compared with the order of the second-thinning trees and the final-felling the round, pith-enclosed materials, the bending strength trees for the bending properties could be explained by the of sawn timber was markedly higher in this study than relatively high age and slow growth of the second-thin- that of laricio pine in the study by Fernández-Golfin et al. ning trees, or reversely, by more rapid growth of final-fell- (2007), and at the same level with Scots pine in the study ing trees caused by the favourable growth conditions. In by Boren (2001). Furthermore, the modulus of elasticity the second thinnings, especially the sample trees from the was higher for sawn timber than for pith-enclosed round Calluna type and the dwarf-shrub transformed type stands timber. increased the average tree age, and represented the slow- Where the final fellings were concerned, sawn timber est growth. Earlier, in a case study by Stöd and Verkasalo of this study had somewhat lower bending properties than (2005), very high bending properties were observed for presented earlier by Lindgren (1996). The difference be- Scots pine sawn timber from commercial second-thinning tween the two studies may be explained by the lower wood operations, the means of MOR, MOE, and density being density of this study, resulting from the different growth 55.1 MPa, 13.6 GPa, and 525 kg/m3, respectively. conditions of the trees. In comparison with the results For the other pine species, Clark et al. (1996), for by Verkasalo et al. (2007), the properties of sawn timber example, noticed a clearly better strength grade distribu- from the final fellings of this study were at the same level, tion of loblolly pine (Pinus taeda L.) sawn timber at the whereas in the study by Ranta-Maunus (2007), the bend- rotation age of 40 years compared to less than 30 years. ing properties of Swedish Scots pine sawn timber were McAlister et al. (1997) noted the modulus of elasticity lower than those reported in this study. of loblolly pine timber to be significantly higher at the The variation of the bending properties was the larg- rotation age of 40 years than at 28 or 22 years. Duchesne est in the first thinnings and the smallest in the second (2006) found a systematically better MOR and MOE of thinnings, indicating more homogeneity in the recovery jack pine (Pinus banksiana Lamb.) sawn timber at the ro- after selection through cuttings. The variation also de- tation age of more than 70 years compared to 50 years, creased from the butt logs to the top logs, indicating the and a decreasing trend in the strength, in particular, by effect of less transverse variation in the pieces of sawn growing dbh class of trees. In the studies by McAlister et timber that were obtainable. Compared with the data of al. (1997) and Duchesne (2006), the bending properties larger pine logs (Hanhijärvi et al. 2005, Hanhijärvi and of jack pine and loblolly pine were approximately at the Ranta-Maunus 2008), the variation of MOE was notable same level as in this study. The comparability of the bend- for the thinning material. The unpredictability of criti- ing properties of Scots pine and loblolly pine has been cal properties decreases the competitiveness of timber in reported in the literature survey by Grekin (2006). comparison to other, more homogenous materials. Hud- The highest values of MOR and MOE of this study son (1967), for example, noted the considerable differ- were measured from the butt log section, and the lowest ences between the individual pieces of European redwood values close to the tree top. In the butt log section, the sawn timber within samples to mask the variations of the differences between the stand and site types were moder- strength properties between the regions. Johansson and ate. At the low and moderate levels of density, MOR and Kliger (2000) named the lack of consistent, predictable, MOE were relatively even in the different log sections, reproducible, and uniform properties as the main disad- and an increment in density affected strength more the vantage of timber as engineering material. lower the position of the log section. The vertical within-

2016, Vol. 22, No. 1 (42) ISSN 2029-9230 158160 BALTIC FORESTRY QUALITY AND BENDING PROPERTIES OF SAWN TIMBER /.../ R. STÖD ET AL. tree variations of wood properties are well-known; in the growth most, are the nutrient-rich site, and the wide spac- tree species having the increasing density from pith to ing of trees (Kellomäki et al. 1992). The growth rate of bark, density decreases markedly from butt to top, and the trees was noted to affect the strength properties in along with it several other wood properties change fol- this study. In 9% of the sample trees the annual growth lowing the same trend. In maritime pine (Pinus pinaster exceeded 2.5 mm, which in the Nordic visual strength Ait.), for instance, a decrease greater than 20% in MOR grading rules is considered as the upper limit for the slow and MOE has been noted between the stem height lev- growth favourable for the quality of sawn timber (Finnish els of 35% and 65% (Machado and Cruz 2005). In the Standards Association 2010). studies by Duchesne (2006) and Zhang et al. (2006), the The average strength of the 50×50-mm boards was MOR, MOE, and density of jack pine decreased from butt higher than that of the middle-sized, 50×75-mm boards, to top. Johansson and Kliger (2000) noted concerning to and almost as high as of the largest 50×100-mm boards. Norway spruce timber that battens sawn from the first or Where the modulus of elasticity was concerned, it was not- second logs had significantly higher bending strength and ed to increase along with the board dimensions being low- modulus of elasticity than battens from the upper parts of est in the 50×50-mm boards and highest in the 50×100-mm tree. Also, according to Haartveit and Flæte (2002), the boards. Density, in turn, was notably lower in the 50×50- increased vertical position in the tree had a negative effect mm boards than in the 50×100-mm boards. The smallest on the MOR and MOR of Norway spruce timber. boards were sawn mainly from the top log section, thus not Density is usually the most important factor affect- explaining the nearly equal average strength of the boards. ing the mechanical wood properties, and their variation Instead, the small size, which decreases the probability of follows the development of density within a stem. Also the occurrence of knots and other defects, could, to some in this study, the wood density had a strong positive ef- extent, explain the good strength level of the 50×50-mm fect on both MOR and MOE. Very high basic density boards. The effect of the object size on the probability of a (over 500 kg/m3) was noted in Calluna type, in contrast weak point was presented by Bohannan in 1966, and it is with the more typical basic density levels in Vaccinium based on a statistical strength theory originally suggested and Vaccinium vitis-idaea types. Where timber from first by Weibull in 1939. In bending, the length effect has been thinnings was concerned, density was at the same level noted to be more significant than the depth effect, due to with those of earlier studies; in the study by Hakkila et al. the lengthwise variation of stresses in a piece of timber (1995), for instance, the basic density of young Scots pine (Isaksson 2003). Due to the size requirements set for the wood was approximately 395 kg/m3 in southern Finland. bending test pieces, in addition to the smaller cross-sec- In Sweden, the basic density of pine saw logs from thin- tional area, the 50×50-mm boards were also shorter than nings was 425 kg/m3 (Björklund and Walfridsson 1993). the 50×75-mm or the 50×100-mm boards. The density decreased within the trees of this study from A piece of timber consists of weak zones containing butt to top, the difference between the lowermost and defects, such as knots, groups of knots, or deviate grain the uppermost stem parts being approximately 57 kg/m3. angle, and the clear wood connecting them (Källsner et Repola (2006) noted an even larger difference, approxi- al. 1997, Ditlevsen and Källsner 1998, Isaksson 2003). mately 100 kg/m3, between the butt and the top of Scots Basically, the larger the size and the more frequent the pine trees, and Björklund and Walfridsson (1993) found defects in a piece of sawn timber are, the smaller the rela- a difference of 90 kg/m3 between the stump and the mer- tive effect of the clear wood properties on its properties chantable top of thinning trees. (Bodig and Jayne 1982; Madsen 1992; Hanhijärvi et al. A good growth of trees normally results in a large ear- 2005). The knots affect the mechanical properties through ly wood proportion within the year rings (e.g. Kellomäki the tension perpendicular to grain in their vicinity, as well et al. 1992, Kärkkäinen 2007). As early wood is, due to as the deviate angle of cells in the knots and the grain the lower density, weaker than late wood, increment in distortions near to them (Desch 1981, Bodig and Jayne the early wood proportion decreases MOR and MOE. The 1982, Hoffmeyer 1995, Forest Products Laboratory 2010, effect of ring width is not, however, caused solely by den- Kärkkäinen 2007). The effect of knots, however, varies sity; the weaker zone formed by early wood, and enabling from one mechanical property to another. Knots decrease cracks, as well as the increasing microfibril angle in the most strongly the longitudinal tensile strength, compres- middle layer S2, have been mentioned as the possible rea- sion strength parallel to the grain, and bending strength; sons for the phenomenon that even with constant density, in general, knots have been noted to have a greater effect bending strength is higher the narrower are the year rings on the strength properties than on the modulus of elastic- (Kärkkäinen 2007). Additionally, in the fast-grown trees ity (Desch 1981, Bodig and Jayne 1982, Forest Products branches grow thick, which results in wood material with Laboratory 2010). However, the individual large knots large knots, and, consequently, in lower strength (Lämsä had no effect on the bending properties in this study, but et al. 1990). The growth conditions, which promote tree the knot sum was noted to affect the modulus of elasticity.

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In every tenth board, the section of board with the largest cultivated trees. Instead, the negative effects of reaction knot sum was noted to equal the location of visually esti- wood in young trees with poorer stem straightness may mated weakest point of the board. have been somewhat underestimated. The theoretic strength-class distribution of samples indicated a strong focus on the strength classes of C30, Acknowledgements or higher, for the sawn timber from the second thinnings, but, in contrast, on the strength classes of C24, or low- This article was enabled by the grants from the Finn- er, for the sawn timber from the first thinnings. Samples ish Cultural Foundation and Puumiesten Ammattikasva- reaching the highest strength classes were found only in tussäätiö, and the project funding by Finnish Forest Re- the second thinnings, and the weakest samples only in the search Institute (Metla) and Natural Resources Institute first thinnings. Comparing the results with those from the Finland (Luke). The work done by the staff and the as- visual strength grading showed that especially in the high- sociate personnel of the Finnish Forest Research Institute est strength classes, the visual evaluation somewhat un- in Joensuu Unit and in Salla Experimental Office, while derestimated the quality and properties of sawn timber. As collecting the study material and carrying out the mea- an exception, the majority of first-thinning boards, which surements on sawn timber, is gratefully acknowledged. had been graded visually to T2, had a lower strength class Authors wish to thank Mr Tuomo Väärä from Kymenlaak- than the C24. This may be due to the fact that in 86% son ammattikorkeakoulu, University of Applied Sciences, of all the boards, the modulus of elasticity was noted to for organising the bending tests of sawn timber, and Ms be the critical factor affecting the potential strength class; Anne-Marita Järviluoto for revising the English language thus, despite the good strength and density values of the of the early version of the manuscript. boards, the low level of MOE decreased their estimated strength classes. As stated earlier, the MOE of wood is References determined by the clear wood properties rather than by the local weak points (Hanhijärvi et al. 2005, Hanhijärvi American Society for Testing and Materials. 2005. ASTM D4761, and Ranta-Maunus 2008). In the first thinnings, where Standard test methods for mechanical properties of lumber and wood-based structural material. 10 pp. the difference between the visual strength grading and Björklund, L. and Walfridsson, E. 1993. Tallvedens egenskaper i the strength classes given by the results from destructive Sverige - Torr-rådensitet, kärnvedhalt, fuktighet och barkhalt. tests, the visual quality of boards was good, but the oth- [Properties of Scots pine wood in Sweden: basic density, er factors, such as wood density, were lower than on the heartwood, moisture and bark content.] Sveriges Lantbruk- suniversitet, Institutionen för virkeslära, Rapport nr. 234. 67 other stand types. pp. (in Swedish) This study indicated that the quality of young Scots Bodig, J. and Jayne, B. A. 1982. Mechanics of wood and wood com- pine trees may be favourable for producing sawn timber posites. Van Nostrand Reinhold Company, New York, 712 pp. with good bending properties. The assessment based on Bohannan, B. 1966. Effect of size on bending strength of wood members. U. S. Department of Agriculture, Forest Service, the visual grading rules of sawn timber showed very high Forest Products Laboratory, Madison, WIS, Research Paper quality potential of boards originating in thinning forests. FPL 56, 30 pp. The visual evaluation and the standardised tests indicated Boren, H. and Barnard, G. 2000. Analysis of the strength and that Scots pine sawn timber with comparable or, in some stiffness properties for small round Scots pine timber tested in bending and compression parallel to grain. Paper and Timber cases, even better bending properties for structural prod- 82(1): 48–56. ucts may be obtained from second commercial thinnings Boren, H. 2001. Factors affecting the knottiness, twisting and me- than from the current final fellings. The bending proper- chanical properties of pith enclosed round and sawn timber of ties of sawn timber from the first thinnings are generally Scots pine (Pinus sylvestris) and Norway spruce (Picea abies) from thinnings in Southern Finland. Finnish Forest Research lower, even though still mainly acceptable for structural Institute, Research Papers 807, 164 pp. uses. The potential for structural timber is the best in sawn Boström, L. 1994. Machine strength grading, comparison of four timber from the butt logs, and, moderate in sawn timber different systems. Swedish National Testing and Research In- from the middle logs. Further research is needed to con- stitute, Building Technology, SP Report 49, 57 pp. Boström, L. 1999. Determination of the modulus of elasticity in firm the effects of site fertility, and silvicultural and cut- bending of structural timber: comparison of two methods. ting regimes on the mechanical properties of timber from Holz als Roh- und Werkstoff 57: 145–149. thinnings, as well as on its shape and dimensional stabil- Cajander, A.K. 1949. Forest types and their significance. Acta ity, moisture distribution, and applicability for machining Forestalia Fennica 56(5): 1–71. Clark, A. III, McAlister, R. H., Saucier, J. R. and Reitter, K. and mechanical connecting. The specific characteristics 1996. Effect of rotation age on lumber grade, yield, and and true effects of juvenile wood and reaction wood in strength of unthinned loblolly pine. Forest Products Journal thinning trees should also be precise. It appears that the 46(1): 63–68. negative effects of juvenile wood may have been overes- Desch, H. E., rev. by Dinwoodie, J. M. 1981. Timber: its structure, properties and utilisation, 6th edn. MacMillan Education Ltd, timated for northerly-grown Scots pine, even for younger London, 410 p.

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Centrum Hout, The Nether- European Committee for Standardization CEN. 1995. EN 408. Tim- lands, p. A4/1–A4/20. ber structures, Structural timber and glued laminated timber, Holmqvist, C. and Boström, L. 2000. Determination of the modu- Determination of some physical and mechanical properties, 19 lus of elasticity in bending of structural timber – comparison pp. of two methods. In: Proceedings of the World Conference on Fernández-Golfín, J. I., Díez-Barra, M. R., Hermoso, E. and Timber Engineering. Whistler, British Columbia, 8 pp. Mier, R. 2007. Mechanical characterization of visually classi- Hudson, W. M. 1967. The strength properties of European redwood fied, small-diameter laricio pine round timber. Spanish Jour- and whitewood. Ministry of Technology, Forest Products Re- nal of Agricultural Research 2007 5(3): 304-311. search, Special Report No 24, 25 pp. Finnish Forest Research Institute. 2013. 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(Eds.), Timber engineering. ajittelu. [Visual and machine strength grading of sawn timber.] STEP 1. Basis of design, material properties, structural com- Master’s thesis. Helsinki University of Technology, Depart- ponents and joints. Centrum Hout, The Netherlands p. A6/1– ment of Forest Products Technology, 75 pp. (in Finnish). A6/8. Lämsä, P., Kellomäki, S. and Väisänen, H. 1990. Nuorten män- Grekin, M. 2006. Nordic Scots pine vs. selected competing species tyjen oksikkuuden riippuvuus puuston rakenteesta ja kasvu- and non-wood substitute materials in mechanical wood prod- paikan viljavuudesta. [Branchiness of young Scots pine as ucts. Literature survey. Working Papers of the Finnish Forest related to stand structure and site fertility]. Folia Forestalia Research Institute 36, 66 pp.. 746: 1–22 (in Finnish). Haartveit, E. Y. and Flæte, P. O. 2002. Mechanical properties of Machado, J. S. and Cruz, H. P. 2005. 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2016, Vol. 22, No. 1 (42) ISSN 2029-9230 162164 BALTIC FORESTRY THE ALTERNATIVES OF TRANSPORT OF WOOD CHIPS /.../ M. IRDLA ET AL. The Alternatives of Transport of Wood Chips in Estonian Conditions: a Case Study

MAREK IRDLA*, ALLAR PADARI AND PEETER MUISTE * Estonian University of Life Sciences, Kreutzwaldi 5, 51014 Tartu, Estonia, phone: +372 53062624, e-mail: [email protected]

Irdla, M.*, Padari, A. and Muiste, P. 2016. The Alternatives of Transport of Wood Chips in Estonian Conditions: a Case Study. Baltic Forestry 22(1): 163-168.

Abstract

Year by year, the production and transportation of wood chips have increased in Estonia. The maximum gross weight of a road train is 44 tons, hence it is not feasible to use trailers with a capacity of more than 90 m3 because the moisture content of wood chips varies considerably and it is forbidden to exceed the weight restriction. As the majority of wood chips is cut right by the road side in Estonia, the entire process depends greatly on the weather and affects also the vehicle fuel consumption, since high precipitation and extremely variable temperatures (-25 °C...+30 °C) result in changing road conditions. Consequently, the goal of the case study was defined as to analyse the price formation of wood chips transportation in Estonian conditions. Within one year, all expenses related to a total of 9 vehicles on fuel, manpower and spare parts were examined. The vehicles were divided into 3 groups according to their transport routes. All vehicles were equipped with a GPRS tracking system that provides information on fuel consumption, working hours, driving speed and itinerary in real time and this data were later used to obtain a detailed overview. The fuel consumption var- ied between vehicles with different transport routes throughout the whole year. The group of vehicles with the lowest fuel consump- tion included three-axle trucks and the largest item of expenditure was fuel. However, transportation of wood chips with two-axle trucks proved to be the least expensive, because, considering total expenditure, the cost of one travelled kilometre was the lowest.

Key words: wood chips, transport, production cost

Introduction Renewable Energy Association 2014), the efficient use of fuelwood resources becomes essential. The 2030 Policy Framework for Climate and En- The main problems occurring in the use of biomass ergy presented by the European Commission seeks to include unstable forest use volume, sporadically insuffi- drive continued progress towards a low-carbon economy. cient reforestation and low cost-efficiency of used biomass Achieving the goals requires a significant increase in the harvesting. Managing the supply chain of wood fuels from use of wood as a renewable energy source, which may put the forest to the customers is a complex task to organise, a strain on the local wood market as the demand for wood especially for the interface between chipping and transport fibres of similar quality will increase. In Estonia up to processes and delays are not easy to detect but they are a now the producers of wood fuels have not yet adequately critical factor for the success or failure of these businesses analysed the production and transport costs although it is (Spinelli et al. 2009, Holzleitner et al. 2013). Similar stud- known that the share of these costs is high. For example, ies on the transport of wood chips have not been conduct- by the experience of SLG Energy OÜ, up to 1/3-1/2 of the ed in Estonia so far and therefore, no comparative material final price of wood chips. from earlier studies is available for reference. According to the statistical forest inventory, the area The efficiency, productivity and cost of long-distance of forest land in Estonia is 2.21 million ha. Based on the transportation depend on factors such as the form of the Forestry Development Plan until 2020, the sustainable use transported material, the energy content of the material, of wood arising from the age distribution of Estonian for- the moisture content, the transportation distance and the ests could be 12-15 million m3 per year (Hendrikson & Ko technical properties of the transport vehicle used. On av- OÜ 2010). According to the Estonian National Renew- erage, the transportation costs for forest chips and bundles able Energy Action Plan until 2020 (NREAP) the pres- make one-third and for loose residues half of the total sup- ent available woody biomass for energy is estimated to be ply costs in Finland (Ranta 2002). on the level of 6.2 million m3 per year. As the target for In Estonian conditions, only road transport is used 2020 by NREAP is to increase the nominal power of gen- internally for transporting wood chips. Rail transport is erating installations operating on renewable energy up to not used due to problems with ordering suitable transport 727 MW, which means a growth by 363.6 MW (Estonian wagons and increasing costs of repeated loadings, since

2016, Vol. 22, No. 1 (42) ISSN 2029-9230 165163 BALTIC FORESTRY THE ALTERNATIVES OF TRANSPORT OF WOOD CHIPS /.../ M. IRDLA ET AL. no larger CHP is located near a railroad. Furthermore, the chines were accounted. As the machines were monitored disadvantage of railways is the relatively dense motorway throughout the year seasonal variation in fuel costs could network in Estonia and since it is a country with a small be determined and also the impact of the load, volume territory, local distances remain too short for cost-efficient and moisture content could be observed. On the basis of rail transport. Shipping is only used to export wood chips the results of the study suitable technologies and logistics from Estonia, since internal waters are not navigable and solutions for Estonian conditions were specified. there is no proper integrated network of harbours in inter- The study also reveals the variation in fuel consump- nal water bodies. So far, it has been reported that transport tion depending on climate conditions. To retrieve this methods for unprocessed raw material are seldom used information, the average temperature of each month in because of the high unit weight transport costs and high Estonia was entered in the databases and later used for handling costs at the receiving facility (Angus et al. 1995). evaluating the effects of temperature on fuel consumption. For cost analysis of transport of wood chips the ini- Multi-lift trucks have Volvo FH500 as the traction tial data was collected from SLG Energy OÜ, one of the unit with the year of production of 2012. These trucks largest producers and transporters of wood chips in Es- utilise two containers when travelling with a full load, the tonia since 2004. Outside Estonia, the company is also total capacity reaching 76 m3. All studied semitrailers are present in Latvia, Lithuania, Finland, Sweden and Russia. produced by MAN within the period of 2004-2007. Trail- The company’s annual output of wood chips in 2013 was ers with a moving floor are manufactured by Carnehl and 1,114,460 bulk cubic metres produced by drum chippers Reich and their capacity is 90 m3 each. It would be con- and 214,279 bulk cubic metres produced by hammer mills. siderably more effective to use semitrailers with a larger Consequently, the goal of the case study was defined capacity but they are subject to the weight restriction im- to analyse the price formation of wood chips transporta- posed in Estonia. tion in Estonian conditions. The tracking system used was Navirec, which en- ables to monitor the trucks equipped with a GPS (Global Materials and Methods Positioning System) in real time. Data communication is forwarded by using the GPRS- General Packet Radio Ser- The initial data from SLG Energy OÜ was collected vice system, which guarantees the constant flow of data, within one year survey. Three different types of trucks (55 as a result of which the constant monitoring of cars on the in total) were observed: trucks with a rear driving axle location map is possible. Additional information such as equipped with a semi-trailer with a moving floor having speed, coordinates and all other required matters to get an 5 axles and a total payload of 40 tons, trucks with double adequate overview of the movement and functioning of driving axles with a semi-trailer with a moving floor hav- the car can always be monitored in the information win- ing 6 axles and a total payload of 44 tons and multi-lift dow. All that is required is a web browser and a small trucks with a trailer having 5 axles and a total payload of device that is placed inside the vehicle (Navirec 2014). 40 tons. All trucks were equipped with GPRS tracking de- To determine the fuel consumption, it was monitored vices, which recorded the route and the fuel consumption. in each vehicle on a daily basis separately for journeys During the study the average age of observed vehicles was with a full load and unloaded journeys. 7 years and this may lead to relatively high maintenance costs. For comparison the data concerning trucks with a Results maximum age of 2 years was analysed to find out the im- pact of higher capital costs and lower fuel consumption During the observation period, 9 examined vehicles and maintenance costs on total transport costs. travelled a total of 460,399 kilometres. The total fuel The observation period extended from 01.09.2012 to consumption for passing the distance comprised 189,684 30.08.2013. During the period, the actual mileages of all litres, which constitutes the annual average fuel consump- vehicles were detected and resulting from this, also the tion of 0.413 l km-1 per vehicle. fuel consumption was registered, which is the main item of expenditure in the transportation sector. In addition to Rear-driving axle trucks fuel consumption, the mileage, costs on manpower, depre- Among rear-driving axle trucks, two of them were ciation, repair costs and insurance costs were ascertained manufactured in 2005 with 287 kW and 316 kW engines. for each vehicle. All truck types travelled in different road The engine power of the third vehicle was 338 kW and types and different climatic conditions in Estonia. it was produced in 2004. During the observation period, Data from the entire forest fuel supply chain are these vehicles travelled a total of 168,668 kilometres and gained from extensive time studies for specific process their average fuel consumption was 0.419 l km-1. The fuel steps (Holzleitner et al. 2013). During the observation pe- consumption in loaded journeys was 0.476 l km-1 and in riod all costs and revenues related to the concerned ma- unloaded journeys it was 0.362 l km-1.

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The distribution of costs is shown in Figure 1. Based of total expenditure. Fuel consumption was followed by on the figure, it may be concluded that in the case of two- costs on manpower which constituted 29 % of total ex- axle trucks, the major item of expenditure was fuel, which penditure, being similar to the cost in the case of two-axle made up 43 % of total expenditure. Fuel consumption was trucks. Repair and maintenance costs attributed to 15 % followed by costs on manpower, which constituted 29 % and depreciation 14 % of total expenditure. These costs of total expenditure. Repair and maintenance costs attrib- were higher compared to two-axle trucks. Costs on insur- uted to 13 % and depreciation comprised 12 % of total ance were the lowest and only made up 3 % of total ex- expenditure. Costs on insurance were the lowest and only penditure. made up 3 % of total expenditure. Multi-lift trucks Double driving axle trucks All multi-lift trucks were manufactured in 2012 and Among double driving axle trucks two of them were their engine power was 375 kW. During the observation produced in 2005 and their engine power was 316 kW. period, these vehicles travelled a total of 141,312 kilo- Another vehicle was manufactured in 2007 with an en- metres and their average fuel consumption amounted to gine power of 353 kW. During the observation period, all 0.440 l km-1. In loaded journeys, the fuel consumption was these vehicles travelled a total of 150,419 kilometres and 0.502 l km-1 and in unloaded journeys it was 0.378 l km-1. their average fuel consumption was 0.381 l km-1. The fuel The distribution of costs is shown in Figure 3. Based consumption in loaded journeys was 0.441 l km-1 and in on the figure, it may be concluded that, as with other unloaded journeys it was 0.322 l km-1. groups of vehicles, the largest item of expenditure in the The distribution of costs is shown in Figure 2. Based case of multi-lift trucks was fuel, which constituted 34 % on the figure, it may be concluded that the major item of of total expenditure. Fuel consumption was followed by, expenditure in three-axle trucks was fuel, but its propor- differently from other groups of vehicles, depreciation tion was smaller than in two-axle trucks, forming 39 % costs which attributed to 31 % of total expenditure. Costs on manpower formed 29 % and costs on repair and main- tenance comprised 5 % of total expenditure. Similarly to the other types of vehicles, insurance costs were the low- est, making up a mere 1 % of total expenditure.

Fuel consumption depending on temperature In using collected data, we added the monthly av- erage temperature to the monthly fuel consumption data. These data are shown in Figure 4. Figure 4 clearly shows the changes in fuel consump- tion depending on changes in temperature. Unfortunately, there were no periods with a very low average temperature during the observation period otherwise the influence of temperature on fuel consumption would have been even more vivid. In order to obtain a comprehensive overview Figure 1. Rear driving axle trucks distribution costs

Figure 2. Double driving axle trucks distribution costs Figure 3. Multi-lift trucks distribution costs

2016, Vol. 22, No. 1 (42) ISSN 2029-9230 167165 BALTIC FORESTRY THE ALTERNATIVES OF TRANSPORT OF WOOD CHIPS /.../ M. IRDLA ET AL. of the changes in the fuel consumption for each group of Table 1. Total expenditure and mileage vehicles in both unloaded and loaded journeys, we added 2-axle 3-axle the results on all vehicles in a joint figure. Multi-lifts trucks trucks Figure 5 depicts the changes in the fuel consumption of all trucks with a different transport route in loaded and Manpower, EUR 53078 46991 60192 unloaded journeys depending on changes in temperature. It Repair costs ,EUR 21366 24567 9540 indicates that the vehicles with the highest fuel consump- Fuel ,EUR 70027 65026 71278 tion were multi-lift trucks and that applies for both loaded Depreciation, EUR 19150 22673 65088 and unloaded journeys. In the case of unloaded journeys, Insurance, EUR 4509 4716 1413 the fuel consumption of two-axle vehicles was almost as high as in multi-lift trucks, when the temperature dropped Total cost, EUR 168130 163973 207511 below 0 °C. This kind of a change in fuel consumption Haul distance, km 168668 150419 141312 was, however, not evident in loaded journeys. Cost, EUR/km 0.997 1.090 1.468

Figure 4. Differences in fuel consumption depending on temperature

Figure 5. Changes in fuel consumption in vehicles with a different number of axles depending on tem- perature

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By summing up all costs incurred during the obser- of two-axle trucks was 0.419 l km-1 and that of multi-lift vation period on different types of vehicles, we were able trucks was 0.440 l km-1. Multi-lift trucks demonstrated the to compile a table of expenditure, which also shows the highest annual average fuel consumption also on loaded vehicle mileages during the observation period. and unloaded journeys. Costs on manpower were the highest in the case of Compared with the results of wood chips transport by multi-lift trucks, which can be explained by their higher (Holzleitner et al. 2013), the fuel consumption was lower mileage compared to the other vehicles, as the travelled (0.409 compared to 0.497 l km-1) and (Lindholm et al. kilometre is also one of the components of wages. Two- 2005) estimated that the average fuel consumption for tim- axle and three-axle trucks incurred approximately equal ber was 0.560 l/km. These results are necessary for imple- repair costs within a year, although the cost per travelled menting and improving cost estimates and for using least kilometre was the highest in three-axle trucks. The repair cost surfaces for wood chip transport (Möller et al. 2007) costs of multi-lift trucks are low because the trucks are Analysis of gathered data indicated that two-axle new and they do not need much repair. Depreciation costs trucks had the lowest cost per each travelled kilome- are directly related to a vehicle accounting value; these tre, which was not expected, because the vehicles with costs were the highest in multi-lift trucks. the lowest fuel consumption were the three-axle trucks. Although the share of fuel consumption in total expen- Discussion and conclusions diture is large, the cost per travelled kilometre cannot be calculated for the vehicles by using only this component, A larger capacity of the trailer is not available since because the final price of a travelled kilometre is deter- the weight restriction on Estonian roads is 44 tons and mined after all items of expenditure have been taken into the weight of a truck loaded with wet chips may exceed account. Although the multi-lift trucks are considerably the maximum allowable weight. In Finland since 2013 newer than the other studied vehicles, their cost per kilo- the weight limit is up to 76 tons, for a 7-axle truck-trailer metre is much higher than that of older trucks. Moreover, combination and for longer module combinations. This the capacity of bulk transported with multi-lift trucks on a gives a possibility for large variation in the load volume single journey is only 76 m3 compared to the 90 m3 in oth- capacity with a practical maximum of 145 m3 for truck- er types of trucks, which increases the cost of each bulk trailers (Ranta et al. 2006). cubic metre of transported material by 15 %, because the Based on the data given above, it may be firmly sug- amount transported on a single journey is smaller. gested that the largest item of expenditure in wood chips logistics is fuel, which may, depending on the number of Acknowledgement axles in a vehicle, constitute up to 43 % of total expendi- ture. Fuel consumption in multi-lift trucks formed 34 % of The research was funded by ENERWOODS, wood total expenditure, thus being the lowest, since these trucks based energy systems from Nordic and Baltic forests. Sus- are considerably newer than the other studied vehicles, so tainable Energy Systems 2050. the result was expected. Costs on manpower accounted for an equal share in total expenditure for all three types References of vehicles, amounting to 29 %. If in older vehicles (two-axle and three-axle trucks), Angus, H.C., Stokes, B. and Twaddle, A. 1995. The transportation costs on manpower ranked second, the second largest item of fuel wood from forest to facility. Biomass and Bioenergy of expenditure in multi-lift trucks was depreciation, which 9(1–5): 191–203. is a highly likely result for new vehicles. In two-axle and Estonian Renewable Energy Association http://www.taastuvener- three-axle trucks, repair costs were always higher than geetika.ee/statistika/. depreciation costs by 1 %, whereas in multi-lift trucks, Hendrikson & Ko OÜ. 2010. “Eesti metsanduse arengukava aas- repair costs made up only 5 % of total expenditure, which tani 2020“ keskkonnamõju strateegilise hindamise aruanne is expected in new vehicles. The proportion will presum- [“Estonian Forestry Development Plan 2020”: Strategic En- ably rise as mileage increases. Insurance costs made up vironmental Assessment Report]. Keskkonnaekspert Riin 3 % of total expenditure in two-axle and three-axle trucks Kutsar (Litsents KMH 0131), Juhtekspert Heikki Kalle (Lit- and was even lower in multi-lift trucks with 1 %. sents KMH 0039). Töö Nr. 1336/10. Avalikule väljapanekule Surprisingly, three-axle trucks proved the most fuel- 21.09.2010. Tartu, 96 pp. Available from: http://www.envir. efficient, with their annual average fuel consumption per ee/sites/default/files/elfinder/article_files/mak_ksh_aruanne_ kilometre being 0.381 l km-1. This number was the lowest avalikustamisele_21-09-10.pdf (in Estonian) compared to the other vehicles on both loaded and un- Holzleitner, F., Kanzian, C. and Höller, N. 2013. Monitoring the loaded journeys. The annual average fuel consumption chipping and transportation of wood fuels with a fleet man-

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agement system. Silva Fennica 47(1): 11 pp.; article id 899. analysis. Doctoral thesis, Acta Universitatis Lappeenran- Available from: http://dx.doi.org/10.14214/sf.899 taensis 128, Lappeenranta University of Technology, Finland, Lindholm, E. and Berg, S. 2005. Energy requirement and environ- 180 pp. mental impact in timber transport. Scandinavian Journal of Ranta, T. and Rinne, S. 2006. The profitability of transporting un- Forest Research 20(2): 184–191. comminuted raw materials in Finland. Biomass and Bioenergy Ministry of the Environment http://www.envir.ee.1113320. 30(3): 231–237. Möller, B. and Nielsen, P.S. 2007. Analysing transport costs of Spinelli, R. and Visser, R. 2009. Analyzing and estimating delays Danish forest wood chip resources by means of continuous in wood chipping operations. Biomass and Bioenergy 33(3): cost surfaces. Biomass and Bioenergy 31(5): 291–298. 429–433. Navirec OÜ. 2011. What to avoid when choosing a vehicle track- ing provider. Available from: http://ee.navirec.com/content/ Received 18 May 2015 view/28/44/lang,english/ Accepted 25 January 2016 Ranta, T. 2002. Logging residues from regeneration fellings for biofuel production - a GIS-based availability and supply cost

2016, Vol. 22, No. 1 (42) ISSN 2029-9230 168170 BALTIC FORESTRY AN ANALYSIS OF THE PHYSICAL PROPERTIES OF SEEDS /.../ Z. KALINIEWICZ ET AL. BRIEF REPORT An Analysis of the Physical Properties of Seeds of Selected Deciduous Tree Species

ZDZISŁAW KALINIEWICZ1, PAWEŁ TYLEK2, ANDRZEJ ANDERS1, PIOTR MARKOWSKI1, TADEUSZ RAWA1, MAREK OŁDAKOWSKI1 AND ŁUKASZ WĄSOWSKI1 1 Department of Heavy Duty Machines and Research Methodology, University of Warmia and Mazury in Olsztyn, Oczapowskiego 11, 10-719 Olsztyn, Poland 2 Department of Forest Work Mechanization, University of Agriculture in Kraków, Al. 29 Listopada 46, 31-425 Kraków, Poland Corresponding author: Zdzisław Kaliniewicz, Department of Heavy Duty Machines and Research Methodology, University of Warmia and Mazury, Oczapowskiego 11/B112, 10-719 Olsztyn, Poland, ph. 48 89 523 39 34, e-mail: [email protected]

Kaliniewicz, Z., Tylek, P., Anders, A., Markowski, P., Rawa, T., Ołdakowski, M. and Wąsowski, L. 2016. An analysis of the physical properties of seeds of selected deciduous tree species. Baltic Forestry 22(1): 169-174.

Abstract

The physical properties of forest tree seeds are an important consideration in seed cleaning and sorting processes. In order to determine variations in and correlations between the pairs of the following parameters: the terminal velocity, thickness, width, length, mass and angle of static friction on steel were measured for seeds of seven deciduous tree species (common beech, copper beech, common hornbeam, small-leaved lime, black locust, mountain ash and grey alder). The results of measurements were pro- cessed statistically by correlation analysis and linear regression analysis. Seed mass was most highly correlated and angle of static friction was least correlated with the remaining parameters. The highest value of the correlation coefficient and the equation with the highest value of the coefficient of determination were reported for the relationship between the mass and terminal velocity of small-leaved lime seeds. In view of the above, a pneumatic separator is recommended for separating seeds of the above tree species. A pneumatic separator is also an effective device for separating the seeds of common hornbeam and grey alder. Common beech and mountain ash seeds should be separated with the use of mesh screens, and copper beech and black locust seeds should be separated with the use of a seed grader.

Key words: seeds, physical properties, processing, seed quality.

Introduction During processing, seeds are sorted into fractions based on selected physical traits. The seeds of forest trees Deciduous trees growing in natural habitats in Po- are generally sorted with the use of simple separating land begin to produce seeds at various age. Seeds can be devices, mostly pneumatic separators and mesh screens. harvested already from 5-year-old trees growing in open Seed separation into fraction improves germination uni- spaces (wild cherry, black locust), whereas dense stands formity, which is a particularly important consideration may begin to produce seeds only at the age of 70 years in tree nurseries. and more (common beech, sessile oak). Most tree species Changes in the physical attributes of tree seeds and growing in open spaces begin to produce seeds at the age the correlations among those parameters are poorly dis- of around 15 years, and trees in dense stands at the age of cussed in the literature. The above data is required for 20-30 years. In Poland, high seed yields from deciduous designing and modeling seed harvesting, transport, clean- trees are noted every 1-2 years, but in some taxa (sessile ing, sorting, storing, sowing and processing procedures. oak, common beech), the cycle may be prolonged to every Significant correlations between the physical traits of 5-8 years (Jaworski 2011). same-species seeds could indicate that those seeds have a

2016, Vol. 22, No. 1 (42) ISSN 2029-9230 171169 BALTIC FORESTRY AN ANALYSIS OF THE PHYSICAL PROPERTIES OF SEEDS /.../ Z. KALINIEWICZ ET AL. very similar shape, which has very important implications tion, symbol region of origin – 251, municipality – Bra- for the geometry of sorting devices. Weak correlations niewo, geographic location – 53.49°N, 20.36°E, forest between physical attributes also carry important infor- habitat – fresh mixed coniferous forest, age – 15 years). mation, and they support the determination of the range Seeds of the remaining tree species were supplied by of variations in the parameters of a sorting device. Ac- Dendrona of Pęcice and were harvested in the Region of cording to the literature (Khan 2004, Parker et al. 2006, Pomorze Zachodnie. Shankar 2006, Quero et al. 2007, Upadhaya et al. 2007, Seed batches were divided by halving (Załęski 1995). Castro et al. 2008, Norden et al. 2009), seed mass is one The analyzed batches of nutlets, seeds and achenes (re- of the main physical properties that affect germination ef- ferred to jointly as “seeds” in subsequent parts of this pa- ficiency of seeds of most species. Heavier seeds usually per) were halved, and one half was randomly selected for germinate faster and produce healthier seedlings as com- successive halving. The above procedure was repeated to pared with lighter ones. Seeds are difficult to sort based produce samples of around 100 seeds each. The result- on their mass. Thus, the correlations between seed mass ing seed samples had the following size: common beech – and other physical properties were analyzed in this study, 119, copper beech – 122, common hornbeam – 123, small- and the results were used to plan seed sorting processes. leaved lime – 114, black locust – 117, mountain ash – 103 The objective of this study was to determine the vari- and grey alder – 117. Moisture content was determined ations and the correlations between the physical proper- with the MAX 50/WH moisture balance (Radwag) on ties of seeds of selected deciduous trees to increase the samples collected from the remaining seeds. The moisture efficiency of seed sorting processing. content of seeds was as follows: common beech – 11.6 %, copper beech – 11.8 %, common hornbeam – 8.3 %, Materials and Methods small-leaved l-ime – 10.5 %, black locust – 8.7 %, moun- tain ash – 8.8 %, grey alder – 8.1 %. The analyzed material (Figure 1) comprised the nut- Terminal velocity of seeds was determined in the lets of common beech (Fagus silvatica L.), copper beech Petkus K-293 pneumatic classifier, seed dimensions were (Fagus silvatica atropurpurea), common hornbeam (Car- determined with the use of the MWM 2325 workshop mi- pinus betulus L.) and small-leaved lime (Tilia cordata croscope (length and width) and a thickness gauge, the Mill.), the seeds of black locust (Robinia pseudoacacia angle of sliding friction was measured on a horizontal L.) and mountain ash (Sorbus aucuparia L.), and grey plane with an adjustable angle of inclination equipped alder (Alnus incana (L.) Moench) achenes. The seeds with a steel friction plate (GPS – Ra = 0.48 µm), and of common beech, common hornbeam and small-leaved seed mass was determined on the WAA 100/C/2 labora- lime were harvested from the following tree stands listed tory scale. All measurements were performed according in the National Register of Forest Reproductive Material: to the methods previously described by Kaliniewicz et a) registration No. MP/1/8841/05 (category of seed al. (2011), Kaliniewicz and Poznański (2013) and Ka- propagation material – from an identified source, type – liniewicz et al. (2013). The angle of static friction was tree stand, region of origin – 157, municipality – Rychliki, determined as the average angle produced by two seed geographic location – 53.59°N, 19.36°E, forest habitat – arrangement patterns: with the longitudinal axis parallel fresh forest, age – unknown), and perpendicular to the direction of inclination. b) registration No. MP/1/40175/05 (category of seed The results were processed with the use of STATISTI- propagation material – from an identified source, type – CA PL v. 10 advanced analytics software package based on tree stand, symbol region of origin – 207, municipal- general statistical procedures, including correlation analysis ity – Czarna Białostocka, geographic location – 53.28°N, and linear regression analysis (Rabiej 2012). Statistical cal- 23.24°E, forest habitat – fresh forest, age – 114 years), culations were performed at the significance level of 0.05. c) registration No. MP/3/41096/05 (category of seed propagation material – qualified, type – seed planta-

Figure 1. Seeds of deciduous trees: a – common beech, b – copper beech, c – common hornbeam, d – small-leaved lime, e – black locust, f – moun- tain ash, g – grey alder

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Results efficient of variation was reported for seed mass, which ranged from 16.57 to approximately 41.48 %. The second The statistical distribution of selected physical attri- most variable trait in the analyzed seeds, excluding the butes of the analyzed seed species is presented in Table 1. common beech, was the angle of static friction, which Copper beech seeds were characterized by the lowest and fluctuated in the range of 10.37 to 37.25%. Seed mass small-leaved lime seeds were characterized by the high- was the most diverse trait in the analyzed seed species. est variation in parameters. The highest value of the co- The ratio of the average mass of grey alder and copper

Table 1. Statistical distribution of the physical properties of selected seed species

Value of trait Standard Coefficient of Seed species Property deviation of trait variability minimum maximum average trait % v (m s-1) 5.78 11.28 9.34 1.14 12.23 T (mm) 5.79 10.10 7.95 0.89 11.14 W (mm) 6.54 11.62 9.05 1.07 11.86 Common beech L (mm) 12.11 21.20 16.39 1.64 9.99 γ (°) 17.3 32.0 23.46 2.43 10.37 m (mg) 104.5 509.1 305.97 73.16 23.91 v (m s-1) 7.43 10.73 9.02 0.84 9.34 T (mm) 6.01 9.23 7.65 0.56 7.36 W (mm) 7.50 11.33 9.02 0.64 7.09 Copper beech L (mm) 14.37 19.97 17.45 1.33 7.65 γ (°) 16.5 31.5 25.00 2.95 11.80 m (mg) 160.1 464.3 312.31 51.74 16.57 v (m s-1) 6.33 10.73 9.65 0.80 8.30 T (mm) 2.33 4.41 3.06 0.29 9.57 W (mm) 3.20 6.86 5.22 0.63 11.98 Common hornbeam L (mm) 3.66 9.46 7.51 0.91 12.03 γ (°) 20.3 37.3 29.23 3.56 12.17 m (mg) 16.5 78.1 53.27 9.19 17.25 v (m s-1) 4.13 11.23 8.20 1.68 20.52 T (mm) 2.69 5.14 4.04 0.57 14.11 W (mm) 3.18 6.00 4.57 0.52 11.47 Small-leaved lime L (mm) 3.77 6.77 5.25 0.73 13.86 γ (°) 4.0 24.0 13.28 4.95 37.25 m (mg) 5.8 62.2 27.69 11.48 41.48 v (m s-1) 6.88 12.38 9.88 1.07 10.85 T (mm) 1.25 2.22 1.75 0.22 12.41 W (mm) 2.29 4.10 3.18 0.34 10.53 Black locust L (mm) 3.34 5.52 4.56 0.43 9.31 γ (°) 8.5 27.0 18.13 3.68 20.29 m (mg) 6.3 28.2 18.40 4.40 23.94 v (m s-1) 3.03 6.88 5.25 0.81 15.48 T (mm) 0.55 1.09 0.82 0.12 14.29 W (mm) 1.28 2.18 1.73 0.20 11.67 Mountain ash L (mm) 2.78 4.63 3.65 0.44 11.94 γ (°) 10.0 51.5 28.98 8.43 29.10 m (mg) 0.4 4.6 2.49 0.82 32.93 v (m s-1) 0.83 3.03 1.87 0.33 17.44 T (mm) 0.27 0.72 0.46 0.08 16.67 W (mm) 1.58 3.39 2.42 0.36 15.05 Grey alder L (mm) 1.96 3.82 2.77 0.33 11.94 γ (°) 20.5 70.0 49.82 11.37 22.83 m (mg) 0.2 1.0 0.49 0.17 34.17 v – terminal velocity, T – thickness, W – width, L – length, γ – angle of sliding friction, m – mass

2016, Vol. 22, No. 1 (42) ISSN 2029-9230 173171 BALTIC FORESTRY AN ANALYSIS OF THE PHYSICAL PROPERTIES OF SEEDS /.../ Z. KALINIEWICZ ET AL. beech seeds was determined at 1:637, and the mass ratio The above observations were confirmed by the re- between the heaviest grey alder seeds and the lightest cop- sults of linear regression analysis (Table 3), where math- per beech seeds was determined at 1:160. ematical dependencies between seed mass and the angle A linear correlation analysis (Table 2) of selected of static friction with a coefficient of determination higher physical attributes that can be potentially used in sepa- than 0.1 were not derived for any seed species. The equa- ration processes indicates that seed mass was most cor- tion with the highest coefficient of determination was de- related with the remaining traits. The highest values of rived for the correlation between the mass and terminal the correlation coefficient were noted in a comparison of velocity of small-leaved lime seeds (0.716). High values seed mass with terminal velocity (common beech – 0.499, of the coefficient of determination (higher than 0.4) were small-leaved lime – 0.846), seed thickness (common also noted in correlations between seed mass and: beech – 0.655), seed width (mountain ash – 0.705) and - terminal velocity of mountain ash seeds, seed length (copper beech – 0.604, black locust – 0.779). - seed thickness of common beech and black locust The mass of grey alder seeds was most correlated with seeds, seed thickness and terminal velocity (0.534). The angle - seed width of small-leaved lime, black locust and of static friction was least correlated with the remaining mountain ash seeds, parameters. - seed length of black locust seeds.

Table 2. Values of Pearson’s correlation coefficients between selected seed properties

Seed species Property T W L γ m

v 0.119 0.202 -0.059 0.307 0.541 T 1 0.591 0.193 0.034 0.655 Common beech W 1 0.122 0.062 0.583 L 1 0.105 0.405 γ 1 0.208 v 0.090 0.071 0.141 0.207 0.386 T 1 0.213 0.190 -0.285 0.551 Copper beech W 1 -0.040 -0.016 0.400 L 1 -0.252 0.604 γ 1 -0.213 v -0.001 0.219 -0.014 -0.002 0.499 T 1 -0.017 0.402 -0.228 0.458 Common hornbeam W 1 -0.068 -0.165 0.308 L 1 -0.149 0.403 γ 1 -0.231 v 0.244 0.392 0.335 -0.095 0.846 T 1 0.798 0.586 0.349 0.513 Small-leaved lime W 1 0.675 0.239 0.663 L 1 0.284 0.555 γ 1 0.108 v 0.658 0.264 0.282 -0.078 0.556 T 1 0.341 0.376 -0.308 0.764 Black locust W 1 0.603 0.139 0.680 L 1 0.147 0.779 γ 1 -0.052 v 0.630 0.428 0.152 -0.172 0.684 T 1 0.507 0.051 -0.215 0.622 Mountain ash W 1 0.395 0.011 0.705 L 1 -0.039 0.535 γ 1 -0.216 v 0.534 -0.102 0.013 0.067 0.433 T 1 -0.127 0.074 -0.039 0.301 Grey alder W 1 0.641 -0.199 0.358 L 1 -0.082 0.367 γ 1 -0.088 v – terminal velocity, T – thickness, W – width, L – length, γ – angle of sliding friction, m – mass; values in bold indicate that the correlation is significant at p = 0.05

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Table 3. Correlations between seed mass and each of physical (Basbag et al. 2010). The range of variations in the dimen- properties of selected seed species sions and mass of mountain ash seeds was similar to that noted by Paulsen and Högstedt (2002) and Bednorz et al. Coefficient Standard Seed Equation of determi- error of (2006), but the average values observed in this study were species nation R2 estimate lower than those given by the cited authors. The average m = 34.643v – 17.698 0.293 61.776 mass of grey alder seeds was lower than that observed by Common m = 54.075T – 123.898 0.429 55.527 Milbau et al. (2009). Seed mass was the most variable beech m = 39.754W – 53.951 0.341 59.667 physical trait in all analyzed species. Seed mass is high- m = 18.070L – 9.826 0.163 67.192 ly correlated with seed dimensions (Table 2), therefore, m = 23.744v + 98.228 0.149 47.922 every change in seed thickness, width or length leads to Copper m = 50.588T – 74.589 0.303 43.373 changes in seed mass. beech m = 32.401W + 20.172 0.160 47.616 The angle of static friction was least correlated with m = 23.409L – 96.263 0.365 41.418 the remaining attributes. The observations made in this m = 5.727v + 1.980 0.249 7.997 Common study and the results reported by Tylek (2006) for com- m = 14.390T + 9.267 0.210 8.204 hornbeam mon beech seeds suggest that the frictional properties of m = 4.082L + 22.615 0.163 8.445 seeds of deciduous trees may not be regarded as major m = 5.774v – 19.669 0.716 6.152 separating properties, but only as auxiliary attributes in Small- m = 10.349T – 14.096 0.263 9.900 leaved the separation process. Seed mass was most highly corre- m = 14.534W – 38.688 0.439 8.639 lime lated with the remaining traits. Similar values of the cor- m = 8.761L – 18.302 0.308 9.596 relation coefficient between seed mass and each of seed m = 2.284v – 4.173 0.309 3.677 dimensions were reported by Sivacioğlu (2010) in Scots Black m = 15.469T – 8.742 0.585 2.850 locust m = 8.927W – 10.025 0.462 3.245 pine, and Sivacioğlu and Ayan (2010) in black pine. Ac- m = 8.087L – 18.487 0.608 2.771 cording to many authors (Khan 2004, Parker et al. 2006, m = 0.691v – 1.133 0.467 0.603 Shankar 2006, Quero et al. 2007, Upadhaya et al. 2007, Mountain m = 4.356T – 1.079 0.386 0.647 Castro et al. 2008, Norden et al. 2009, Kaliniewicz et al. ash m = 2.869W – 2.468 0.497 0.586 2012, 2013), seed mass influences germination efficiency, m = 1.009L – 1.185 0.286 0.697 but heavy seeds do not always germinate faster than light m = 0.224v + 0.075 0.187 0.153 seeds. Heavier seeds are generally more likely to germi- Grey alder m = 0.166W + 0.092 0.128 0.158 nate and produce healthy seedlings because plump seeds m = 0.187L – 0.025 0.135 0.157 accumulate more storage reserves that are essential for seedling emergence. v – terminal velocity (m s-1), T – thickness (mm), W – width The observed correlations between seed mass and (mm), L – length (mm), m – mass (mg) the remaining attributes are characterized by relatively high determination coefficients for biological material. Discussion The noted results indicate that seeds of common horn- beam, small-leaved lime and grey alder would be sorted Seeds harvested from various deciduous tree species most effectively in a pneumatic separator (terminal ve- and characterized by different dimensions and mass were locity), common beech seeds – in mesh screens with lon- analyzed in this study. The heaviest common beech seeds gitudinal openings (thickness), mountain ash seeds – in were more than 2500-fold heavier than the lightest grey mesh screens with round openings (width), and the seeds alder seeds. Common beech seeds had similar dimensions of copper beech and black locus – in a grader (length). If to those given by Bodył and Sułkowska (2007), but they the preferred sorting device is not available, a pneumatic were considerably heavier. The above seeds were char- separator could also be used to sort mountain ash seeds, a acterized by lower terminal velocity than that noted by mesh screen with longitudinal openings to separate cop- Tylek (2011). The average mass of common hornbeam per beech, common hornbeam and black locust seeds, and seeds was higher than that described by Aguinagalde et a mesh screen with round openings – to sort seeds of the al. (2005). The evaluated seeds of small-leaved lime were common beech and small-leaved lime. similar in width and length to seeds harvested from a seed plantation in north-eastern Poland (region of origin – 106) Acknowledgments by Ludwikowska et al. (2011), but they were lighter than the samples investigated by Aguinagalde et al. (2005). This research study was financed by the Department The average mass of black locust seeds was lower in com- of Heavy Duty Machines and Research Methodology, parison with Greek seeds analyzed by Dini-Papanastasi et Faculty of Technical Sciences of the University of Warmia al. (2012), but higher in comparison with Turkish seeds and Mazury in Olsztyn.

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References Ludwikowska, A., Kowalkowski, W. and Tarasiuk, S. 2011. Wzrost szczepów lipy drobnolistnej (Tilia cordata Mill.) na Aguinagalde, I., Hampe, A., Mohanty, A., Martin, J.P., Duminil, plantacji nasiennej w Nadleśnictwie Susz [The growth of J. and Petit, R.J. 2005. Effects of life-history traits and spe- small-leaved lime (Tilia cordata Mill.) clones in a seed or- cies distribution on genetic structure at maternally inherited chard in the Susz Forest District]. Forest Research Papers markers in European trees and shrubs. Journal of Biogeogra- 72(2): 121-130 (in Polish with English abstract). phy 32: 329-339. Milbau, A., Graae, B.J., Shevtsova, A. and Nijs, I. 2009. Effects Basbag, M., Aydin, A. and Ayzit, D. 2010. The Effects of Differ- of a warmer climate on seed germination in the subarctic. An- ent Temperatures and Durations on the Dormancy Breaking of nals of Botany 104: 287-296. Black Locust (Robinia pseudoacacia L.) and Honey Locust Norden, N., Daws, M.I., Antoine, C., Gonzalez, M.A., Garwood, (Gleditsia triacanthos L.) Seeds. Notulae Scientia Biologicae N.C. and Chave, J. 2009. The relationship between seed mass 2(4): 125-128. and mean time to germination for 1037 tree species across five Bednorz, L., Walkowiak, R., Maciejewska-Rutkowska, I. and tropical forests. Functional Ecology 23(1): 203-210. Moliński, K. 2006. Seed variability of the Polish species of Parker, W.C., Noland, T.L. and Morneault, A.E. 2006. The ef- the genus Sorbus (Rosaceae). Dendrobiology 55: 3-9. fects of seed mass on germination, seedling emergence, and Bodył, M. and Sułkowska, M., 2007. Ocena zróżnicowania na- early seedling growth of eastern white pine (Pinus strobus L.). sion buka zwyczajnego (Fagus sylvatica L.) w Polsce w latach New Forests 32: 33-49. 1992−2004 [Estimation of European beech (Fagus sylvatica Paulsen, T.R. and Högstedt, G. 2002. Passage through bird guts L.) seed differentiation in Poland in the years 1992-2004]. Syl- increases germination rate and seedling growth in Sorbus au- wan 9: 12-21 (in Polish with English abstract). cuparia. Functional Ecology 16: 608-616. Castro, J., Reich, P.B., Sánchez-Miranda, Á. and Guerrero, J.D. Rabiej, M. 2012. Statystyka z programem Statistica [Statisctics 2008. Evidence that the negative relationship between seed with Statistica package]. Ed. Helion, Gliwice, ISBN 978-83- mass and relative growth rate is not physiological but linked 246-4110-9 (in Polish). to species identity: a within-family analysis of Scots pine. Tree Shankar, U. 2006. Seed size as a predictor of germination success Physiology 28: 1077-1082. and early seedling growth in ‘hollong’ (Dipterocarpus macro- Dini-Papanastasi, O., Kostopoulou, P. and Radoglou, K. 2012. carpus Vesque). New Forests 31: 305-320. Effect of seed origin, growing medium and mini-plug density Sivacioğlu, A. 2010. Genetic variation in seed cone characteristics on early growth and quality of black locust (Robinia pseudo- in a clonal seed orchard of Scots pine (Pinus sylvestris L.) acacia [L.]) seedling. Journal of Forest Science 1: 8-20. grown in Kastamonu-Turkey. Romanian Biotechnological Jaworski, A. 2011. Hodowla lasu. Tom III. Charakterystyka hodow- Letters 15(6): 5695-5701. lana drzew i krzewów leśnych [Silviculture. Volume 3. Breed- Sivacioğlu, A. and Ayan, S. 2010. Variation in cone and seed char- ing characteristics of forest trees and shrubs]. Ed. PWRiL, acteristics in clonal seed orchard of Anatolian black pine Warszawa (in Polish). [Pinus nigra Arnold subsp. pallasiana (Lamb.) Holmboe]. Kaliniewicz, Z., Grabowski, A., Liszewski, A. and Fura, S. 2011. Journal of Environmental Biology 31: 119-123. Analysis of correlations between selected physical attributes Tylek, P. 2006. Tarcie i sprężystość jako cechy rozdzielcze bukwi of Scots pine seeds. Technical Sciences 14(1): 13-22. [Friction and elasticity as separation properties of beech nuts]. Kaliniewicz, Z., Markowski, P., Anders, A., Rawa, T., Liszewski, Sylwan 5: 51-58 (in Polish with English abstract). A. and Fura, S. 2012. Correlations between the germination Tylek, P. 2011. Analiza cech aerodynamicznych našion jodły pospo- capacity and selected attributes of European larch seeds (Larix litej i buka zwyczajnego [Analysis of aerodynamic proper- decidua Mill.). Technical Sciences 15(2): 229-242. ties of common fir and common beech]. Inżynieria Rolnicza Kaliniewicz, Z. and Poznański, A. 2013. Zmienności i wzajemna 6(131): 247-253 (in Polish with English abstract). korelacja wybranych cech fizycznych nasion lipy drobnolist- Upadhaya, K., Pandey, H.N. and Law, P.S. 2007. The Effect of nej (Tilia cordata Mill.) [Variability and correlation of selected Seed Mass on Germination, Seedling Survival and Growth in physical attributes of small-leaved lime (Tilia cordata Mill.) Prunus jenkinsii Hook.f. & Thoms. Turkish Journal of Botany seeds]. Sylwan 157(1): 39-46 (in Polish with English abstract). 31: 31-36. Kaliniewicz, Z., Tylek, P., Markowski, P., Anders, A., Rawa, T., Załęski, A. 1995. Nasiennictwo leśnych drzew i krzewów iglastych Jóźwiak, K. and Fura, S. 2013. Correlations between the ger- [Management of coniferous forest trees and shrubs for seed mination capacity and selected physical properties of Scots production]. Ed. Oficyna Edytorska „Wydawnictwo Świat”, pine (Pinus sylvestris L.) seeds. Baltic Forestry 19(2): 201-211. Warszawa (in Polish). Khan, M.L. 2004. Effects of seed mass on seedling success in Ar- tocarpus heterophyllus L., a tropical tree species of north-east Received 29 June 2014 India. Acta Oecologica 25: 103-110. Accepted 25 January 2016

2016, Vol. 22, No. 1 (42) ISSN 2029-9230 164176 BALTIC FORESTRY FIRM FAILURE CAUSES IN THE FOREST SECTOR /.../ O. LUKASON ET AL. BRIEF REPORT Firm Failure Causes in the Forest Sector: An Analysis of Bankrupted Estonian Firms

OLIVER LUKASON1*, TANEL LUKASON1, URMAS VARBLANE1 1Faculty of Economics and Business Administration, Tartu University, Narva road 4, 51009 Tartu, Estonia *Corresponding author: Oliver Lukason, [email protected], phone: +3727376336

Lukason, O.*, Lukason, T. and Varblane, U. 2016. Firm Failure Causes in the Forest Sector: An Analysis of Bank- rupted Estonian Firms. Baltic Forestry 22(1): 175-180. (Brief report)

Abstract

This paper studies firm failure causes in the forest sector and is based on a thorough analysis of 50 bankruptcy cases from Estonia. The results indicate that in the forest sector in more than a half of the occasions firm failure was triggered by either only internal or external reasons. Namely, for 26 % of cases bankruptcy was caused by only internal reasons, for 30 % by only external reasons and for 44 % by both reasons. The most common causes noted in court judgments were concentration on only a few custom- ers (resulting in cessation of cooperation or unpaid claims), unfavourable market developments (drop in demand or in product prices and increase in competition or in input factor prices), lengthy unprofitable activities, lack of working capital, too low share of equity or inability to find additional financial resources, and management errors.

Keywords: forest sector, firm failure, bankruptcy causes

Introduction of higher share of woodland cover compared to other Eu- ropean Union countries except for Sweden and Finland Firm failure has been extensively studied for de- according to land cover and land use statistics (see Euro- cades, but so far such research has been dominated by stat 2012) and long traditions in the industry. According empirical studies about failure prediction. Studies about to Statistics Estonia (2015), the share of the previously failure causes have been rather infrequent (see e.g. Alt- noted three industries (ISIC divisions 02, 16, 17) ranged man and Narayanan 1997). Although there are numerous from 3.0 % to 4.5 % of total Estonian GDP in 2000-2013, notions of firm failure (see e.g. Cochran 1981 for different being the lowest in 2009 during the economic recession. definitions), this paper applies the most commonly used In the literature, there is no consensus whether firms term, that is bankruptcy (permanent insolvency). Still, it fail mainly because of management deficiencies (i.e., in- should be acknowledged that failure causes in case of dif- ternal causes) or unfavourable events in the environment. ferent definitions (e.g. failure in the sense of not achiev- Therefore, a broad range of different theoretical streams ing the expected rate of return) could differ from those (e.g. population ecology and strategic choice approaches) common to bankrupted firms. Available studies outlining try to explain the root causes of firms’ collapse, whereas failure causes based on the data of bankrupted firms con- more novel approaches focus on the interaction of differ- centrate on larger industries (see e.g. Hall 1992, Baldwin ent theories, that is, internal and external failure causes et al. 1997) and there are no studies available specifical- are considered simultaneously (Daily 1994). Correspond- ly about the forest sector. In this study, the forest sector ingly, Mellahi and Wilkinson (2004) have noted that is considered in its classical meaning (see e.g. Lebedys collapse caused due to only internal or external reasons 2004), namely the following International Standard In- emerges only in extreme circumstances (e.g. management dustrial Classification (i.e. ISIC; revision 4) divisions: a) fraud or serious incompetence, some external shocks 02 - forestry and logging, b) 16 - manufacture of wood like force majeure). Most generally, external causes are and products of wood and cork, except furniture; manu- defined as factors beyond the management control and facture of articles of straw and plaiting materials, c) 17 - internal causes as factors under the management’s con- manufacture of paper and paper products. In the Estonian trol (e.g. Boyle and Desai 1991: 34). As with theoretical economy, the forest sector holds a prominent role because approaches, a lot of fragmentation through findings can

2016, Vol. 22, No. 1 (42) ISSN 2029-9230 177175 BALTIC FORESTRY FIRM FAILURE CAUSES IN THE FOREST SECTOR /.../ O. LUKASON ET AL. also be found in empirical studies. Firstly, studies have This study aims to be the first one to identify the relied on varying data sources, like interviewing man- causes of firm failures in the forest sector. The paper in agement or owners (e.g. Gaskill et al. 1993), conducting the form of a brief report is structured as follows. The questionnaires among trustees (e.g. Baldwin et al. 1997), introductory part including a review of literature is fol- and applying opinions from court documents (e.g. Hall lowed by a section outlining methods and materials of the 1992, Blazy and Chopard 2010). Of these approaches, the study. Then, main results are presented with their discus- opinions of trustees or courts should be considered more sion, which is followed by conclusions. reliable, as the assessments by the owners or management of bankrupted firms can be biased (Beaver 2003). Previ- Materials and methods ous studies also show variation in the taxonomies of ap- plied failure reasons. Although in most cases the taxono- For the current study, we apply Estonian bankrupt- mies are more sophisticated than simple internal-external cy cases from ISIC divisions 02 and 16 during the peri- taxonomy, they can eventually be distilled into one. Gen- od 2002-2009, as for that period we possess registration erally, the internal failure causes as reasons of corporate numbers of court judgments about bankruptcies obtained collapse seem to be more frequent in empirical literature from the Estonian Ministry of Justice. For all firms the when compared with external failure causes (see e.g. Hall exact ISIC class is known from the last annual report and 1992, Gaskill et al. 1993). Still, the above could depend has been presented in Table 1. ISIC division 17 is not ap- on whether in case of overly passive or active responses to plied, as no cases could be obtained for this division for environmental changes (see e.g. van Witteloostuijn 1998), the studied period. The Estonian bankruptcy law obliges the cause is marked to be internal or external. Literature trustees to note failure causes in a specific court judgment provides little evidence about failure causes in the primary and therefore we downloaded all publicly available judg- sector (including logging firms). Lukason (2014), for in- ments based on their registration numbers for the given two stance, found internal and external reasons of failure to be ISIC divisions. In total, we obtained information about 50 almost equally important on the example of agricultural bankrupt firms, which are small- and medium-sized enter- firms. Laitinen et al. (2014) found that among European prises (SMEs) with the following pre-bankruptcy (period ISIC section A firms, the most common failure process t-2, where t denotes the year of bankruptcy) median values was gradual worsening of financial situation through pre- reflecting their size: 7 workers, assets of 187,000 Euros and bankruptcy years – a situation that according to a study sales of 246,000 Euros. In the viewed period 2002-2009, in by Lukason and Hoffman (2014) could be associated with total 57 firms belonging to ISIC division 02 bankrupted and multiple failure causes. There is more evidence about the same figure for division 16 was 149, thus in total our manufacturing firms, although in aggregated form, not for data represent around 24 % of all bankruptcies in these two different divisions of ISIC section C. Baldwin et al. (1997) divisions. In ISIC division 17, there was only one bankrupt- found that the most common external causes affecting cy in the viewed period. What concerns the statistics of ac- more than a half of the manufacturing firms were the tive firms, then figures about the year 2012 from Statistics economic downturn, competition and customer difficul- Estonia (2015) denote the number of firms with workers in ties, whereas from internal causes, general, financial and forest sector as follows: ISIC 02 – 1,130 firms, 16 – 1,005, marketing management problems were characteristic for and 17 – 56. Thus, the bankrupt firms form a quite small up to ¾ of these firms. According to Hall’s (1992) study, proportion from all active firms in the forest sector. manufacturing firms were mostly bankrupted because of The collection of court judgments was followed by operational management (all internal reasons) and strate- the extraction of failure causes from them, which were gic (mainly external reasons) problems. In summary, the provided there in a short summarized form, often accom- available evidence about why firms fail is divergent. panied by a more specific explanation of each cause. After Indirect evidence about firm failure causes can be the extraction of the failure causes, we processed them found in other streams of research. For instance, Hoff further to obtain a short list of causes to be presented in et al. (1997) found that being competitive in secondary the current study. The list was composed by two research- wood products industry is not only hindered by classical ers separately and then the results were compared in or- causes as government regulations, resource (including der to provide validity for the results. Then, the previous labour) availability and price, but also by innovation in examples by Boyle and Desai (1991) and Baldwin et al. different domains like technology, strategic management (1997) were used as benchmark taxonomies to attribute and marketing. Lähtinen (2007) noted the importance of each detected reason to be either internal or external. both tangible and intangible resources for gaining success Again, this was done separately by two researchers. Fi- in woodworking industry. Thus, both internal and external nally, for each case it has been noted in Table 1 whether factors have been found to influence firm vitality in the the insolvency for this case was caused by at least one in- forest sector. ternal and/or external reason. This is achieved by noting a

2016, Vol. 22, No. 1 (42) ISSN 2029-9230 176178 BALTIC FORESTRY FIRM FAILURE CAUSES IN THE FOREST SECTOR /.../ O. LUKASON ET AL. mark “+” before each case in the relevant column in Table Results 1. Besides analyzing the specific failure causes, the pre- viously described methodology allows us to apply three- The actual failure causes have been presented in Ta- component taxonomy in the further analysis: a) bankrupt- ble 1. Although the description varies through court judg- cy was caused only by internal reason(s), b) bankruptcy ments, some common tendencies can be found. Firstly, was caused only by external reason(s), and c) bankruptcy many firms have concentrated on a single or few custom- was caused by both internal and external reasons. ers and cessation of cooperation with them or an inability Our dataset of 50 firms breaks down as follows: 11 to pay outstanding debt by customers has therefore been logging firms (ISIC 0220), 17 sawmilling and wood pla­ the trigger for the collapse. Secondly, on numerous occa- ning firms (ISIC 1610), 2 manufacturers of veneer sheets sions, unfavourable market developments have been not- and wood-based panels (ISIC 1621), 13 manufacturers ed: a drop in demand or in product prices and an increase of builders’ carpentry and joinery (ISIC 1622), 4 manu- in competition or in input factor (materials, labour) prices. facturers of wooden containers (ISIC 1623), 3 manufac- Thirdly, as a regular collapse reason also found in the lit- turers of other wood products (ISIC 1629). In order to erature, lengthy unprofitable activities have been noted. study whether the failure causes (as classified according Fourthly, different financial factors such as lack of work- to the previously given three-component taxonomy of ing capital, a too low share of equity or inability to find ad- causes) have significantly different association with dif- ditional financial resources have been frequently reported. ferent industries (the ISIC classes) and bankruptcy years, Lastly, more or less severe mistakes by management also we will apply Fischer’s Exact Test (see e.g. Weinberg appear as very common collapse causes, sometimes even and Abramowitz 2008: 499). Due to the small number of in the form of fraudulent activities. Thus, it can be seen observations in some groups, the classical test for such that both internal and external reasons are very common analysis – the Chi-Square Test – would not be appropriate. contributors to collapses in the forest sector.

Table 1. Failure reasons for 50 forest sector firms (original reasons and also as classified into an internal-external taxonomy)

Class Year when Internal External of ISIC bankruptcy Specific reasons given in the court judgment reasons reasons rev 4 was declared

0220 2002 + Lack of working capital, mistakes made in accounting of taxes 0220 2003 + + Growth in competition, misuse of the firm’s cash Cooperation ended with the only client, machinery breakdown halted the production 0220 2003 + + process 0220 2003 + Growth in competition, increased material prices 0220 2007 + Grave errors in management 0220 2007 + + Changes in the tax law, employees left, cooperation ended with the main client 0220 2008 + + Growth in competition, increased costs, poor health of the manager Lack of working capital, constant underuse of equipment and their too high costs, 0220 2008 + incompetence of managers 0220 2009 + Grave errors in management (including embezzlement of the firm’s assets) 0220 2009 + Economic recession, reduction of demand in the industry 0220 2009 + Violation of contractual obligations by a foreign cooperation partner 1610 2002 + Operating with constant losses, a weak business plan, insufficient analysis of activities 1610 2002 + Too high rent costs, excessive leverage Loss of major customers, investors were not interested in providing additional capital, 1610 2003 + + failure of one investment project Under-exploitation of production capacity, violation of various management obligations 1610 2003 + (including proper book-keeping, acting with good care) Ongoing tax dispute, inability to sell goods due to an unfavourable market situation, 1610 2004 + + working with a very low profit margin Unrealized business plan, inability to find additional finance, lack of raw material, high 1610 2005 + + competition 1610 2006 + Inability to assess and forecast costs, low product quality

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1610 2006 + Too high labour costs, wrong cash flow forecast and assessment of risks 1610 2006 + Too high labour costs, disagreement between owners 1610 2007 + + Failed projects abroad, the equipment was stolen After enlargement, material prices increased more than product prices and demand 1610 2007 + also dropped 1610 2008 + + More unfavorable market situation than expected, constant unprofitable activities 1610 2008 + Clients failed to pay for the products 1610 2008 + Failed business plan Too many unprofitable contracts, some debtors defaulted, poor health of the manager, 1610 2008 + + the firm did not perform as planned since its foundation Low quality due to old machinery, high competition, growth in input material prices, 1610 2008 + + lack of qualified workforce 1610 2008 + Problems with getting raw material, no additional investors could be involved The main client was liquidated, new markets were not found, costs increased when 1621 2008 + + prices remained unchanged, low work efficiency, no funds to reorganise the firm Quick drop in demand in this sector, inability to reorganise activities, no credit 1621 2009 + + possibilities and inability to find additional capital, defaulted debtors Lack of working capital, failure of marketing policy, defaulted debtors, not managing 1622 2002 + + accounts receivable Increase in competition, no finance available for new investments, an incompetent 1622 2002 + + business plan (did not account for the market situation), revenues lower than costs 1622 2003 + Problems with a foreign cooperation partner, unsteady market situation 1622 2004 + Weak business plan and too low share of equity 1622 2004 + Defaults of foreign and local customers Fire in the production facility, depreciated equipment, loss of cooperation with foreign 1622 2007 + + clients, excessive dependence from the only local cooperation partner Drop of demand in the region, revenues insufficient to cover costs, too low insurance 1622 2007 + + compensation to buy new equipment after its breakdown Lease surface agreement ended and no new place of activity was found, revenues 1622 2008 + became lower than costs 1622 2008 + Low quality of export products, grave errors in management 1622 2008 + Collapse of market, inability to pay in time by debtors Increase in input prices, drop in product prices, drop in demand, low motivation by 1622 2009 + + owners, inability to involve additional capital Economic recession generally and at the market the firm was functioning, increase of 1622 2009 + loan interest rate by the bank Drop in demand for products the firm was manufacturing and misunderstandings 1622 2009 + + between the owners Lack of necessary sense of duty, too old equipment, too small production volumes, low 1623 2003 + + market prices, increase in competition Loss of the main customer resulted in sales’ drop and negative profit, strong 1623 2003 + competition and increase in raw material price Excessive orientation on a few clients, constant drop of profitability in the sector, 1623 2004 + + constant performance with losses 1623 2006 + The main client quit the contract Increase in production costs and decrease in the number of customers lead to 1629 2007 + unprofitability 1629 2007 + Bankruptcies of customers resulting in non-payment for goods 1629 2009 + + Very low level of working capital, non-payment of clients on time

Notes: The ISIC rev 4 codes have the following meaning – 0220 logging, 1610 sawmilling and planing of wood, 1621 manufacture of veneer sheets and wood based panels, 1622 manufacture of builder’s carpentry and joinery, 1623 manufacture of wooden containers, 1629 manufacture of other wood products. Although included in ISIC rev 4 1629 description, none of the firms in the current analysis dealt with manufacture of articles of cork, straw and plaiting materials.

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It can be seen that in less than a half of the cases in of this study (e.g. lack of working capital or a too low the sample (44 %) bankruptcy is caused by both reasons share of equity) have been very common predictors of (internal and external) contributing to the collapse. This collapse (see e.g. the literature review by Dimitras et al. finding varies through ISIC classes (see Table 2). Namely, 1996). What concerns grave errors in management, then only in two classes (1621 and 1622) the collapse because in the study by Lukason (2013) various fraudulent activi- of both reasons is the most common, whereas in two class- ties (e.g. embezzlement of firm’s resources, tax fraud, us- es (0220 and 1610) bankruptcies caused by either only age of fake invoices) accompanying firm bankruptcies internal or by both reasons are equally important. In one have been noted to be relatively common in Estonia. What class (1623) failures because of only external reasons or concerns the distribution of causes through bankruptcy both reasons are equally important, whereas in class 1629 years (see Table 3), it cannot be concluded that the share external causes are the most frequent. The specific results of external causes would have risen especially during the by classes can be followed in Table 2. Still, Fisher’s Exact economic recession characterizing the last years in the Test’s p-value is 0.554, indicating that the association be- current analysis (according to Statistics Estonia (2015) in tween failure causes and specific industrial classes is not the year of 2009 Estonian GDP fell around 17 %, there- statistically significant. In other words, firms in various fore affecting most of the industries). industrial classes of the forest sector do not collapse be- There are also several studies which on the exam- cause of remarkably different reasons. Table 3 shows the ple of other sectors have found a similar set of the most breakdown of failure causes through different bankruptcy important failure reasons, when compared with those es- years. Similarly with industry classes, for different years tablished in the current research on the example of only the distribution of failure causes varies, but Fisher’s Ex- forest sector firms. In Hall’s (1992) study, the three most act Test does not indicate significant differences (p-value common reasons were undercapitalization, poor manage- 0.622). The robustness of both tests was checked by ex- ment of debt and lack of demand for products. In Baldwin cluding either industry classes or years with a low number et al.’s (1997) study, the most prominent external causes of observations, but that did not alter the test results. were economic downturn, competition and customer dif- ficulties, whereas for internal reasons the most frequent Discussion were different general management and financial man- agement problems. Thus, it can be concluded that failure The most frequent failure causes found in the current causes reported in case of bankrupt Estonian forest sector study coincide with those noted in the available literature. firms coincide with those brought out in previous studies As in case of many ISIC 02 and 16 firms the business for different sectors and countries. process is set up to service only a few clients (see e.g. This research also challenges studies (e.g. Mel- D’Aveni and Ilinitch 1992), the importance of this fail- lahi and Wilkinson 2004), which propose that for most ure cause is logical. Fluctuations in timber prices have of the firm collapses, both internal and external causes been common in the studied period (see Sirgmets et al. contribute. According to this study, on less than a half of 2012), justifying the high frequency of input or output the occasions bankruptcy was triggered by both types of price dynamics as a collapse reason. Lengthy unprofitable causes simultaneously. Moreover, as shown in Table 2, activities have been found to be an especially important for some forest sector classes, the bankruptcies caused contributor to firm failure in previous studies (see e.g.rev - by both reasons were not the most frequent group at all. enue financing failure firms in Laitinen 1991). Through Table 2 also shows that for logging, sawmilling and wood numerous bankruptcy models established for manufactu­ planing firms, internal causes were more frequent than ring firms, financial variables noted in the results section external, whereas for manufacturers of wooden contain-

Table 2. Frequencies of re-classified failure causes through Table 3. Frequencies of re-classified failure causes through industry classes bankruptcy years

Only internal Both Only internal Both Industry class \ Only external Bankruptcy Only external causes causes causes causes Cause causes present year \ Cause causes present present present present present 0220 4 4 3 2002 3 2 0 1610 7 7 3 2003 1 4 3 1621 0 2 0 2004 1 2 1 1622 2 6 5 2005 0 1 0 1623 0 2 2 2006 3 0 1 1629 0 1 2 2007 1 4 3 Total 13 22 15 2008 3 5 4 2009 1 4 3 Total 13 22 15

2016, Vol. 22, No. 1 (42) ISSN 2029-9230 181179 BALTIC FORESTRY FIRM FAILURE CAUSES IN THE FOREST SECTOR /.../ O. LUKASON ET AL. ers, builders’ carpentry and joinery firms, external causes Beaver, G. Small business success and failure. Strategic Change were more frequent. Therefore the results allow us to hy- 12(3): 115-122. Blazy, R. and Chopard, B. 2012. (Un)secured debt and the likeli- pothesize that in case of more sophisticated products, the hood of court-supervised reorganization. European Journal of role of external forces (including market developments) Law and Economics 34(1): 45-61. could alter the destiny of forest sector SMEs more than Boyle, R.D. and Desai, H.B. 1991. Turnaround strategies for small internal decisions. This at least partially lends support to firms. Journal of Small Business Management 29(3): 33-42. Cochran, A.B. 1981. Small business mortality rates: a review of the the conclusions in Hoff et al.’s (1997) study focusing on literature. Journal of Small Business Management 19(4): 50-59. U.S. forest sector firms. Daily, C.M. 1994. Bankruptcy in Strategic Studies: Past and Prom- ise. Journal of Management 20(2): 263-295. Conclusions D’Aveni, R.A. and Ilinitch, A.Y. 1992. Complex patterns of vertical integration in the forest products industry: systematic and bank- ruptcy risks. Academy of Management Journal 35(3): 596-625. Firm failure has been studied extensively, but em- Dimitras, A. I., Zanakis, S. H. and Zopounidis, C. 1996. A survey pirical research reporting actual failure causes is rather of business failures with an emphasis on prediction methods infrequent, whereas there are no studies available about and industrial applications. European Journal of Operational Research 90(6): 487-513. forest sector firms. Both theoretical and empirical stud- Eurostat. 2012. Land cover statistics. [http://ec.europa.eu/eurostat/ ies have emphasized the importance of internal and exter- statistics-explained/index.php/Land_cover_statistics]. Re- nal causes in contributing to firm failure. Therefore, this trieved 3.2.2015. study also aimed to study the role of internal and external Gaskill, L.-A.R., Van Auken, H.E. and Manning, R.A. 1993. A factor analytic study of the perceived causes of small business causes in the failure of forest sector firms. failure. Journal of Small Business Management 31(4): 18-31. The sample in the current study consisted of 50 forest Hall, G. 1992. Reasons for Insolvency Amongst Small Firms – A sector firms (from ISIC divisions 02 and 16) that became Review and Fresh Evidence. Small Business Economics 4(3): bankrupt during 2002-2009 in Estonia. The analysis of 237-250. Hoff, K., Fisher, N., Miller, S. and Webb, A. 1997. Sources of court judgments, where the failure causes are reported, competitiveness for secondary wood products firms: A review indicated that in the majority of cases (56%) firms failed of literature and research issues. Forest Products Journal because of only internal or external reasons, which in turn 47(2): 31-37. were similarly represented (26% and 30%, respectively). Laitinen, E. 1991. Financial ratios and different failure processes. Journal of Business Finance & Accounting, 18(5): 649-673. The common causes for failure were relying on a few Laitinen, E., Lukason, O. and Suvas, A. 2014. Are firm failure customers or cooperation partners, unfavourable market processes different? Evidence from seven countries. Invest- developments, lengthy unprofitable activities, different fi- ment Management and Financial Innovations 11(4): 212-222. nancial causes and (severe) management faults. The study Lebedys, A. 2004. Trends and current status of the contribution of the forestry sector to national economies. FAO working paper on fi- also showed that although the shares of different failure nancing sustainable forest management FSFM/ACC/07. 138 pp. causes varied through industrial classes of the forest sec- Lukason, O. 2013. Firm bankruptcies and violations of law: an tor, there was no statistically significant association be- analysis of different offences. In T. Vissak, & M. Vadi (Edi- tween different classes and causes. This study could be tors), Dishonesty in Management: Manifestations and Conse- quences. Bingley, Emerald, p. 127-146. elaborated by applying a larger sample, by focusing more Lukason, O. 2014. Why and how agricultural firms fail: evidence from on specific cases and also by studying the interconnection Estonia. Bulgarian Journal of Agricultural Science, 20(1): 5-11. of failure causes and values of firms’ financial indicators. Lukason, O. and Hoffman, R.C. 2014. Firm Bankruptcy Probabil- ity and Causes: An Integrated Study. International Journal of Business and Management 9(11): 80-91. Acknowledgements Lähtinen, K. 2007. Linking Resource-Based View with Business Economics of Woodworking Industry: Earlier Findings and The study has been prepared with financial support Future Insights. Silva Fennica 41(1): 149-165. through grant IUT20-49 “Structural Change as the Fac- Mellahi, K. and Wilkinson, A. 2004. Organizational failure: a cri- tique of recent research and a proposed integrative framework. tor of Productivity Growth in the Case of Catching up International Journal of Management Reviews 5(1): 21-41. Economies” received from the Estonian Research Coun- Sirgmets, R., Kaimre, P. and Padari, A. 2012. Forest Sector Im- cil. Authors thank anonymous reviewers and Tiia Vissak pacts from the Increased Use of Wood in Energy Production in for comments and corrections. Estonia. Baltic Forestry 18(1): 125-132. Statistics Estonia. 2015. Statistical database. Retrieved 1.2.2015 from www.stat.ee References Van Witteloostuijn, A. 1998. Bridging behavioral and economic theories of decline: organizational inertia, strategic competi- Altman, E.I. and Narayanan, P. 1997. An international survey of tion, and chronic failure. Management Science 44(4): 501-519. business failure classification models. Financial markets, In- Weinberg, S.L. and Abramowitz, S.K. 2008. Statistics Using stitutions & Instruments 6(2): 1-57. SPSS: An Integrative Approach. Cambridge University Press, Baldwin, J., Gray, T., Johnson, J., Proctor, J., Raffiquzamann, Cambridge, 764 pp. M. and Sabourin, D. 1997. Failing concerns: business bank- ruptcy in Canada. Ottawa, Analytical Studies Branch, Statis- Received 02 July 2014 tics Canada. 69 pp. Accepted 08 October 2015

2016, Vol. 22, No. 1 (42) ISSN 2029-9230 180182 BALTIC FORESTRY DEVELOPMENT AND TRAITS OF WOLF TREES IN SCOTS PINE /.../ E. MAKRICKIENE ET AL. REVIEW PAPERS Development and Traits of Wolf Trees in Scots Pine (Pinus sylvestris L.): A Literature Review

EKATERINA MAKRICKIENE1*, LARS DRÖSSLER2, GEDIMINAS BRAZAITIS1, 1Aleksandras Stulginskis University, Institute of forest biology and silviculture, Studentų g.11, Akademija, LT-53361 Kaunas district, Lithuania, [email protected] 2 Swedish University of Agricultural Sciences (SLU), Southern Swedish Forest Research Centre, Rörsjövägen 1, SE-23053, Alnarp, Sweden

Makrickienė, E.*, Drössler, L. and Brazaitis, G. 2016. Development and Traits of Wolf Trees in Scots Pine (Pinus sylvestris L.): A Literature Review. Baltic Forestry 22(1): 181-188. (Review Papers)

Abstract

This article reviewed studies from Germany, Russia, Lithuania, Sweden and Finland about wolf trees in Scots pine (Pinus syl- vestris L.) forests and examined the definition of a wolf tree. In addition, we analyzed the main traits and parameters of these trees, such as lower crown ratio, more conical stem taper, partly deformed crown, and thicker and longer branches. The analysis revealed changes in the definition of a wolf tree during the XX century and different definitions over various regions. The differences between wolf trees and common trees were found in growth patterns, stress sensitivity and genetics. Also this article reviewed several pos- sible reasons for the occurrence of wolf trees in forest stands.

Key words: b-type trees, tree development, morphological types, competition, crown form, growth patterns, thinning.

Introduction eters, and utilize a larger growing space, thus reducing stand timber volume. Scots pine (Pinus sylvestris L.) is naturally occurring tree species found in the boreal forest region and high-al- titude forests along a large belt from north-west Europe to Siberia (Critchfield and Little 1966, Nikolov and Helmis- aari 1992). In Europe, Scots pine is one of the most im- portant tree species for commercial use (Mason and Alia 2000). For biodiversity, native pinewoods have a high conservation value (Lust et al. 2001, Kuuluvainen and Yl- läsjärvi 2011).The management of Scots pine has a long history (Cotta 1821, Schwartz 1991), which is reflected by various thinning programs developed over the last cen- turies (Schwappach 1908, Wiedemann 1943, Erteld 1960, Nilsson et al. 2010). In current silvicultural programmes, the quality of pine timber (Liziniewicz 2014), the role of tree species admixtures (Agestam 1985), and the potential for developing more heterogeneous stand structures (Ma- son 2000) are often emphasized. A key point in managing this tree species with its rapid early growth has been the removal of trees with undesirable form (‘wolf trees’) during the early stages of stand development. Wolf trees grow faster than the sur- Figure 1. Wolf tree (indicated with an arrow) in a 17-year old rounding trees, have a larger crown and other tree param- self-regenerated Scots pine stand in Lithuania

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Such trees are not favoured by foresters due to their more vigorous trees or other classifications like hierar- lower timber quality and because they hinder the de- chy, social classes or quality classes were also selected for velopment of better quality trees, which can negatively reading. Later, the accepted publications were divided into influence future timber harvests. However, trees of this those relevant for our three research questions concern- type could benefit biodiversity due to the provision of in- ing wolf trees, and those where general patterns of Scots creased stand structural complexity compared to stands pine stand development could be linked to our findings composed solely of trees that are regular in size and and ideas about wolf trees. In addition, silvicultural text- crown (McElhinny et al. 2005). Given the importance of books and management guidelines used in Germany, Swe- biodiversity questions for modern forestry, we summarize den, Russia and Lithuania were examined in their native existing information on wolf trees and their features as the language to include other relevant studies. We also used first step for further research. The objectives of our litera- snowball sampling – non-probability chain referral sam- ture review were (1) to examine how Scots pine wolf trees pling (Patton 1990) by using the literature references pro- were distinguished from other pine trees in the stand; (2) vided in selected studies to find other relevant literature. to explore reasons for the occurrence of wolf trees, and During the reading and analysis of the literature, (3) to explain their development. definitions and characteristics of wolf trees and possible reasons (hypothesized, studied or concluded) for their Methods emergence were recorded and later summarized in tables and figures. The statements of different authors about the The literature search for relevant articles consisted characteristics of wolf trees were divided into three cate- of three steps: gories, depending on whether these were stated (assumed/ 1. Web-based literature search to collect studies hypothesized), measured in field, or tested in a long-term which could refer to wolf trees in Scots pine; experiment. 2. Identification of the potentially relevant studies by reading the title and abstract of each collected article; Results 3. Analysis of the potentially relevant studies and extraction of information related to our three original re- In total 401 studies were collected using the Web of search questions. Science, when the syntax listed above was used. After con- The web-based literature search was performed fining the results to the research area of forestry, 16 studies through the search engines and databases provided by the were collected. 11 additional studies were collected after Web of Science and Google Scholar. During the search the search using Google Scholar. Ten studies, directly re- with the Web of Science the syntax was: lating to wolf tree issues, and seven more studies about general development of Scots pine were analyzed in the Topic=(“wolf tree*”) OR Topic=(b-typ*) results section of our paper; other papers were considered AND Title=(“scots pine”) OR Title=(“pinus sylvestris”) in the discussion. NOT Title=(canis) NOT Topic=(Mediterranean) NOT Topic=(population*) NOT Topic=(fung*) Development of wolf trees in Scots pine NOT Topic=(treat*) NOT Topic=(*preservat*) As stated by Spathelf and Ammer (2015), Scots pine NOT Topic=(expos*) NOT Topic=(chem*) shows the best growth on fertile sites but it is mainly found NOT Topic=(pollut*) NOT Topic=(strobus) on poorer soils due to the lower competitive abilities of NOT Topic=(herbivor*) the species. Vaartaja (1950) discovered that on richer soils massive germination occurred later, which could be Refined by: explained by greater competition from the ground veg- etation. However, some seedlings germinate earlier than Research Areas=( FORESTRY ) AND Document others and genetic differences between growth rate and Types=( ARTICLE OR ABSTRACT OR BOOK OR micro-site variation initiated subsequent size stratification REPORT ) (Kellomäki and Hari, 1980). These differentiation pro- Timespan=All years. cesses were strengthened by the resulting size difference Search language=Auto between the trees. Those trees which germinated earlier than others had extra time to develop, so they experienced The search in Google Scholar was performed using less competition (Kuuvulainen and Rouvinen 1997). the key words “Scots pine wolf trees”, “scots pine b-type” Hafemann and Stähr (2007) showed, that Scots pine and excluding the word “canis”. seedlings need large gap openings to develop a good qual- In step two, studies that referred to wolf trees in Scots ity stem. The optimal gap diameter for successful regener- pine were selected directly. Studies referring to larger or ation should be similar to a mature tree height (20-30 m.)

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Such gap size provides the optimal microclimatic and especially twisted and branchy, or had other low quality lighting conditions for seedlings. In smaller gaps, lower traits. Interestingly, he also classed forked trees in the quality branchy stems with poorer form are often found. “worse wolf” tree type. The study of Lönnroth (1925) is However, bigger gaps can also create unfavourable condi- the first mention of wolf trees in scientific literature. tions for regeneration, such as stronger direct sunlight and By the middle of the 20th century, the classifications bigger temperature fluctuations in the upper layers of the had become briefer, and two wolf trees’ classes were united soil. The lower capacity of Scots pine to self-prune also into one. Schädelin (1942) presented wolf trees as vigorous provides greater opportunity for seedlings to develop into individuals that differ from other trees by superior height wolf trees (Spathelf and Ammer 2015) or diameter growth and a poor growth form (forks, thick Productivity during stand development is the highest branches, crooked or bent stem axis). However, the under- for trees with long and small crowns (Spathelf and Am- standing of wolf trees in Scots pine stands was develop- mer 2015). This also corresponds to the study of Stähr and ing, and the second term for them, namely b-type trees ap- Hainke (2009), who stated that the relationship between peared in the German silvicultural literature. In contrast to tree growth and crown diameter decreases with age. The that, target trees with good stem quality and small amount issue about wider crowns and lower productivity with age of branches were called a-type trees. Thus, several names is also mentioned in thinning guides as the reason for ear- for the same wolf tree phenomenon can be found (see Table ly removal of wolf trees (Kerr and Haufe 2011). 1). Kräuter (1965), Pofahl et al. (1979) and Lockow (1992) defined b-type Scots pine trees as having a low crown ratio, Analysis of the studies regarding wolf trees relatively long and thick branches, small branch angles in These studies showed that wolf trees have been men- the lower part of the stem and a mostly irregular, partly tioned and described in the silvicultural literature for a one-sided crown. These studies also identified an interme- long time. However, for a long time this term was used to diate a/b type: trees with parameters close to common trees describe solitary trees. By the beginning of the 20th centu- but with longer and thicker branches. Other definitions ry the term had an important part in forest classifications. were provided by Smith et al. (1997), who described wolf For example, Lönnroth (1925) distinguished two types of trees as poorly formed dominants, and Matthews (1989), wolf trees: i) “better wolf”, strongly developed trees with who presented wolf trees as trees with straggling crowns larger branches, and ii) “worse wolf”, trees, which were and low branching, together with defective stems. Table 1. Different terms describing wolf trees, and authors using them

Term Description Authors Wolf trees Super-dominant trees with wide crowns and thick Lönnroth (1925), Schädelin (1942), Matthews branches (1989), Smith et al (1997), Gedminas and Ozolinčius (2006), Hagner (2012)

b-type trees Trees having low crown ratio, relatively long and Kräuter (1965), Pofahl et al. (1979), Lockow (1992), thick branches, small branch angles in the lower Hertel and Kohlstock (1994), Beck (2000) part of the stem and a mostly irregular, partly one- sided crown. Deformed seedlings Seedlings of abnormal form Freyberg and Stetsenko (2009)

Figure 2. Empirical studies on Scots pine wolf trees in Northern Europe and ages of the study stands. For comparison, the timing of pre-commercial thinnings (PCTs), thinnings and harvest in typical Scots pine forest man- agement as well as the natural forest develop- ment with more than 200 years old trees (see Lassila 1920 or Edwards and Mason 2006) are included in the Figure

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Table 2. Tree parameters of Scots pine wolf trees in comparison to other trees in the stand as presented by Kräuter (1965) and Her- tel and Kohlstock (1994) and complemented by other studies (* tested in combination with other features)

Morphological Tested/measured/ Tree parameter Study Trait stated Tested Pofahl et al. 1979*; Hertel and Kohlstock1994 Lower crown ratio Measured Kräuter 1965; Tree crown Stated Gedminas and Ozolinčius2006 Tested Hertel and Kohlstock 1994 Partly one-sided, more flat crown Stated Beck 2000 Tested Pofahl et al. 1979*; Hertel and Kohlstock 1994 Thicker branches in the lower part of stem Measured Kräuter 1965; Stated Gedminas and Ozolinčius 2006; Beck 2000 Tested Hertel and Kohlstock 1994 Branches Longer branches Measured Kräuter 1965; Stated Gedminas and Ozolinčius 2006; Beck 2000 Tested Hertel and Kohlstock 1994 Smaller branch angle in the lower part of stem Stated Gedminas and Ozolinčius 2006 Lighter color of needles Stated Gedminas and Ozolinčius 2006 Tested Lockow 2007; Smaller amount of needles Needles Stated Gedminas and Ozolinčius 2006 Drier needles Stated Gedminas and Ozolinčius 2006 Larger dry needle biomass Tested* Pofahl et al. 1979* More conical stem taper Tested Hertel and Kohlstock, 1994 Stem Lower wood density due to wider annual rings Stated Lockow 2007 Super-dominant Stated Gedminas and Ozolinčius 2006; Beck, 2000 Tested Hertel and Kohlstock 1994 Faster growth as a young tree Stated Gedminas and Ozolinčius 2006 Growth Distinguishable from the early age Tested Freyberg and Stetsenko2009 Faster growth Tested Pofahl et al. 1979*; Lockow 1992 Smaller photosynthetic efficiency Stated Gedminas and Ozolinčius 2006

Genetic Less genotype variation Tested Hertel et al. 1998 aspects Smaller heterozygosity Tested Hertel et al. 1998 More sensitive to stress Tested Beck 2004; Apel et al. 2005 Stability Tested Freyberg and Stetsenko2009 Less stable Stated Beck 2004; Lockow 2007

For the purpose of our study, we will use a very gener- The youngest wolf trees were mentioned by Frey- al understanding of wolf trees as described by Beck (2004). berg and Stetsenko (2009), who described the influence He characterizes wolf trees as super-dominant trees with of pesticides on the development of Scots pine seedlings. wide crowns and thick branches. This definition summa- In their study, seedlings of Scots pine were treated with rizes the most important points of the previous ones. pesticides, and then planted. The description of the seed- However, it is important to mention that the charac- ling appearance was very similar to the description of a teristics of wolf trees are relative and can only be com- wolf tree. Their results showed development into several pared with other trees within a particular stand. morphological types in the early growth stages, and the The studies, selected for our analysis, cover a range percentage of the wolf tree type was higher among the of tree ages between 2 and 159 years (see Table 3 and seedlings grown from the treated seeds, than this from Figure 2). They will be described below in the order of the non-treated ones. Another observation was that seedlings increasing tree age. with an abnormal morphological type had a much higher

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Table 3. Analyzed studies, concerning Scots pine wolf trees, ity to recover after Lymantria monacha attack and higher with publication year, location and experimental stand age. mortality (Apel et al. 2005). Beck (2004) concluded that after Scots pine trees stopped growing as an immediate re- Stand age, Authors Year Location sponse to drought and high temperature, dominant and co- years dominant individuals in general would continue to grow, Lönnroth 1925 Finland 14 to 159 while suppressed trees are less or not able to continue. Kräuter 1965 Germany 8 to 45 In addition, more juvenile wood, more uneven year-rings, Pofahl et al. 1979 Germany 22 and less self-pruning were mentioned by Lockow (2007). Lockow 1992 Germany 10 to 100 The study of Gedminas and Ozolincius (2006) covers Hertel and Kohlstock 1994 Germany 17 a wide range of tree ages, almost from germination un- Hertel et al. 1998 Germany 20 til the mature forest stage. The authors state the same is- Beck 2000 Germany 2 to 65 sue about the wolf trees’ position in the forest, as Lockow (2007): usually wolf trees are not the tallest trees in the Beck 2004 Germany 61 to 122 stand. The main trait of wolf trees, as stated in the study, Apel et al. 2005 Germany 50 to 78 was comparatively wide and branchy crown, lower branch Gedminas and Ozolinčius 2006 Lithuania 2 to 100 angle and thicker branches. Due to this fact, wolf trees take Lockow 2007 Germany 10 to 86 super-dominant position in the stand. Another important Freyberg and Stetsenko 2009 Russia 2 to 14 issue was the productivity of wolf trees. For example, if Hagner 2012 Sweden 8-19 we assign the relative solar energy usage efficiency coeffi- cient of 1.0 for trees of a normal morphological type, then probability of mortality compared to seedlings with a nor- for the wolf trees it would be only about 0.5-0.7 mal morphological type. Concerning the silvicultural promotion of larger pine The study by Hertel and Kohlstock (1993) was per- individuals, Degenhardt (2009) simulated the growth re- formed in 17-year old Scots pine stands with trees from sponse on the base of solitary trees and found relatively 72 progenies from Central and Eastern Europe. 90 trees small effects on growth compared to individuals of av- of the normal morphological type and 95 wolf trees were erage size. Stähr and Hainke (2009) showed that a four- chosen from these stands according to crown ratio, branch fold increase in growing space during the thicket stage thickness and crown width. Lateral buds were taken from resulted in twofold increased crown surface and growth. them, and a genetic analysis was performed. The results In the pole stage, the effect was even smaller (Stähr and of this analysis showed only a minor polymorphism dif- Heinke 2009). ference between the two morphological types. However, The economic impacts of the removal or promotion trees of the wolf tree type had a significantly lower geno- of wolf trees was explored by Hagner (2012), who studied type variation while trees of a normal morphological type two stands, planted at the same time in the same condi- had a higher level of heterozygosity based on a high num- tions. One stand was managed in a traditional way and in ber of rare alleles. However, Hertel and Kohlstock (1993) the second stand, individual wolf trees were promoted. It also stated that the classification of Scots pine trees into is important to note, that smaller healthy pines were left these two types was due to a combination of several ef- between the wolf trees. The study showed a bigger diam- fects, not only genetics. eter variation in wolf trees at the age 19. Still, the mean Knowledge about pine wolf trees in Germany was diameter of wolf trees was at least 2 cm bigger than the summarized by Lockow (2007), who referred to long- mean diameter of regular trees. Using the software pro- term observations covering stand ages from 10 to 86 gram “Tree”, an economical model was built to examine years. Trees classified as b-type had stronger branches the effects of future stand tending. The results showed that and a smaller crown length/crown width ratio than trees removing wolf trees with a diameter of 11-22 cm, stimu- classified as a-type. B-type trees were not the tallest trees lated growth of the smaller pines, which would be subse- in the stand; however, their diameter growth was faster. In quently ready for final felling at 90 years of age. This is 15 principle, the largest individuals at the beginning of the years later than in traditionally managed stands. However, study remained the largest trees over time, often charac- wolf trees could also be sold as low quality wood by the terized by non-concentric crown projections. For the same age 20. The total income in a wolf-tree stand was 115%, crown size (vertically projected on the stand area), b-type compared to a traditionally managed stand. trees had a smaller crown surface than other trees, and Based on the reviewed studies describing the mor- hereby less needle biomass (Lockow 2007). Therefore, phological differences between wolf trees and common Lockow (2007) concluded that a-type trees used the total trees, we created the following figure; summarizing the stand area more efficiently in terms of stand growth than main traits of a wolf tree and compared it with a common b-type trees. For b-type trees, there was also a lower abil- Scots pine tree (see Figure 3).

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silvicultural interventions may not always be necessary (Kohlstock 1982). Haapanen et al. (1997) observed low to moderate heritabilities for most stem parameters. How- ever, the heritabilities of branching angle and branchiness were among the highest observed. Based on these six studies, we suppose that seedlings established earlier on richer soils are more likely to develop into a/b intermedi- ate type trees, and the seedlings with a tendency to inherit low branching angle and branchiness are likely to develop into b-type wolf trees. Regarding the stability of wolf trees, we found contra- dictory statements. Apel et al. (2005) found a higher sen- sitivity to stress, at least a year after heavy insect attacks. However, in the studies of Augustaitis (1998, 2007) and Juknys et al. (2003) we can see a clear tendency of faster recovery of dominant trees after different types of stress. In the study of Augustaitis (1998) the most dominant trees had the biggest loss of foliage after a pest outbreak. However, during the next 3 years the dominant trees showed much faster recovery after the stress event than the other tree classes. The explanation could be found in older trees clas- sifications, where wolf trees were divided into two morpho- Figure 3. Comparison of wolf tree’s and common tree’s mor- logical types (Lönnroth 1925). The trees of a “better wolf” phological traits type, which are super-dominant, could be less sensitive to stress than normal trees, while the trees of a “worse wolf” type were most likely removed earlier from the stands de- Discussion and conclusions scribed in the studies of Beck (2004) and Lockow (2007). In the study of Ferris and Humphrey (1999) the wide Usually the silvicultural literature only mentions range of tree diameter distribution and canopy complexity wolf trees in relation to thinning rules. Therefore, the were listed among the most important factors, which affect identification of wolf trees depends on subjective judg- biodiversity in the stand. Wolf trees, with their fast diame- ments. Considering this fact, we used both information ter growth at a younger age, and thick long branches, could from wolf tree studies and general literature about the de- definitely benefit biodiversity by adding complexity to the velopment and growth of Scots pine forests. stand structure and creating a wider range of possible habi- Main features of the wolf trees described in the lit- tat from the earlier stages of the stand development. erature were wide crowns, thick branches, low branch In conclusion, we expect differences between the angle and a super-dominant position in the stand. In the number of wolf trees on fertile and poor sites: fertile soils thinning guidelines the super-dominant position is the key can promote a higher frequency of wolf trees and their feature for distinguishing a wolf tree in a stand. However, fast development. Considering the number of wolf trees definitions vary between regions and the variations in and the soil type, forest managers can decide how many conditions do not allow for a homogeneous picture of in- wolf trees to leave. This decision can also be based re- dividual wolf tree development. But there does appear to garding the amount, quality and perspective of the trees be a common understanding about those features, which around the wolf tree and the distance from the wolf tree to define a wolf tree. the neighbouring trees. For example, more free-standing Our analysis showed that most authors distinguished wolf trees could be left to provide future habitat, because wolf trees by their lower crown ratio and more one-sided, they would cause less effect on future crop trees. branchy crown. Uusvara (1991) showed that on more pro- ductive sites more Scots pine trees with thick branches, Acknowledgements bigger branch number and branch angle – typical features of wolf trees – were found. This corresponds to the stud- The authors would like to acknowledge Michael ies by Kräuter (1965) and Kohlstock (1982) who pointed Manton for the constructive remarks, Evaldas Makrickas out that earlier removal of wolf trees is required on more for the illustration of wolf tree and common tree morpho- productive sites to promote healthy individuals with few- logical traits and Darius Danusevičius for the inspiring er branches. However, in young stands on moderate sites idea to make a research of Scots pine wolf trees.

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Schorfheide]. AFZ/Der Wald 8: 391 (in German). and Bartkevičius, E. 2003.Scots pine (Pinus sylvestris L.) Augustaitis, A. 1998. Regeneration of Scots pine trees damaged by growth and condition in a polluted environment: from decline pests according to the retrospective analysis of tree ring time to recovery. Environmental Pollution 125 (2003) 205–212. series. In: Proceedings of the International Conference “Den- Kellomäki, S. and Hari, P. 1980. Eco-physiological studies on drochronology and environmental trends”, Kaunas, 1998: young Scots pine stands: I. Tree class as indicator of needle 151-159. biomass, illumination, and photosynthetic capacity of crown Augustaitis, A.2007. Pine Sawflies (Diprion pini L.)Related Chang- system. Silva Fennica, 14: 227-242. es in Scots Pine Crown Defoliation and Possibilities of Recov- Kerr, G. and Hauf, J. 2011 Thinning Practice. A Silvicultural ery. Polish Journal of Environmental Studies 16(3) 363-369. Guide. Version 1.0, January 2011. Forestry Commission. Beck, W. 2004.Wirkung der Witterung auf Wachstum und Vitalität Retrieved from: http://www.forestry.gov.uk/pdf/Silviculture_ von Waldbäumen und Waldbeständen [Effect of weather on Thinning_Guide_v1_Jan2011.pdf/$FILE/Silviculture_Thin- growth and vitality of forest trees and forest stands]. In: Aus- ning_Guide_v1_Jan2011.pdf wirkungen der Trockenheitim Jahr 2003 auf Waldzustand und Kräuter, G. 1965. Die Behandlung von Kiefernjungbeständen auf Waldbau. Arbeitsbericht der BFH Nr. 2/2004: 36-56 (in Ger- der Grundlage von biologischen und dynamischen Merkmalen man). der Einzelstämme [The treatment of pine young stands on the Beck, W. 2000. Silviculture and stand dynamics of Scots pine in basis of biological and dynamic aspects of single stems]. Con- Germany. Investigacion Agraria: Sistemos y Recursos Fores- ference report. AdL Berlin 75: 337-342 (in German). tales Fuera de Serie 9(1):199–212. Kuuluvainen, T. and Ylläsjärvi, I. 2011. On the natural regenera- Cotta, H. 1821. Anweisungen zum Waldbau [Instructions for silvi- tion of dry heath forests in FinnishLapland: a review of V. T. culture]. 3rd edition, Arnoldsche Buchhandlung, Dresden, 138 Aaltonen (1919), Scandinavian Journal of Forest Research pp. (in German) 26(10): 34-44 Critchfield, W.B. and Little, E.L. 1966. Geographic distribution of Kuuvulainen, T. and Rouvinen, S. 1997. Structure and asymme- the pines of the world. USDA Forest Service Misc. Publ. 991. try of tree crowns in relation to local competition in a natural Degenhardt, A. 2009. Wie viel Platz braucht ein Kiefernstamm? mature Scots pine forest.Canadian Journal of Forest Research Ergebnisse aus den Untersuchungen solitär erwachsener Kief- 27: 890-902. ern in Brandenburg [How much space does a pine stem need? Lassila, I. 1920. 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Medžiai-Vilkai, Medžiai- im norddeutschen Tiefland – Ökologie und Bewirtschaftung. Avys ir Sverto Taisyklė [Wolf-trees, sheep-trees and the rule Eberswalder Forstliche Schriftenreihe Band 32. 317-340 (in of lever]. Naturales Scientiae Omnibus. Retrieved from: http:// German). gamta.vdu.lt/bakalaurai/pop_straipsniai/medziai_vilkai_avys/ Lönnroth, E. 1925. Untersuchungen über die innere Struktur und medziai_vilkai_avys.html (in Lithuanian). Entwicklung gleichaltriger naturnormaler Kiefernbestände, Hagner, M. 2012. Försök att med röjning framställa talltimmer med basiert auf Material aus der Südhälfte Finnlands [Research hög kvalitet [Attempt to produce high-quality pine logs by tree into the internal structure and evolution of the same age removal]. UBICON, Umeå, 9 pp. (in Swedish) normal natural pine stands, based on the materials from the Hafemann, E. and Stähr, F. 2007. Zur Verjüngung der Kiefer [On southern half of Finland]. Acta Forestalia Fennica N 30 (in pine regeneration]. 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cion Agraria: Sistemos y Recursos Forestales Fuera de Serie Economic and statistical analysis of forest department of the 1–2000: 317-333. main station of forest research network in Eberswalde]. Neu- Matthews, J.D. 1989. Silvicultural Systems. Clarendon Press, Ox- damm, Eberswalde (in German). ford, 304 pp. Schwartz, E. 1991. Die Kiefer (Pinus sylvestris). Geschichtliches McElhinny, C., Gibbons, P., Brack, C. and Bauhus, J. 2005. For- zur Kiefernwirtschaft. [The Pine (Pinus sylvestris). History of est and woodland stand structural complexity: its definition the pine industry]. Berichte aus Forschung und Entwicklung, and measurement. Forest Ecology and Management 218: 1 – Band 24: 68-71, 77-87. Institut fürForstwissenschaften, Eber- 24. swalde (in German). Nikolov, N. and Helmisaari, H. 1992. Silvics of the circumpolar Sjoberg, K. 2000. Silviculture and Biodiversity of Scots Pine For- boreal forest species. In: Shugart, H.H., Leemans, R. and ests in Europe. Investigacion Agraria, Fuera de Serie 1: 317- Bonan, G.B. (Eds.). A systems analysis of the global boreal 336. forest. Cambridge University Press, Cambridge, p. 13-84. Smith, D.M.; Larson, B.G.; Kelty, M.J. and Ashton, P.M.S. Nilsson, U., Agestam, E., Eko , P.-M., Elfving, B., Fahlvik, N., 1997. The practice of silviculture: applied forest ecology. John Johansson, U.,Karlsson, K., Lundmark, T. and Wallentin, Wiley and sons, New York, 560 pp. C. 2010. Thinning of Scots pine and Norway spruce monocul- Spathelf, P., and Ammer, C. 2015. Forest management of Scots tures in Sweden – Effects of different thinning programmes pine (Pinus sylvestris L.) in northern Germany – A brief re- on stand level gross- and net stem volume production. Studia view of the history and current trends. Forstarchiv 86: 59-66. Forestalia Suecica: 219 pp. Stähr, F., and Hainke. K. 2009. Zum Einfluss von Soziologie und Patton, M.1990.Qualitative evaluation and research methods. Sage Standraum auf die Zuwachs- und Kronenentwicklung der Ge- Publications, Inc., Thousand Oaks, CA, the USA, 532 pp. meinen Kiefer (Pinus sylvestris) [On the influence of sociol- Pofahl, U., Lockow, K.-W. and Läuter, H. 1979. Zur Lösung von ogy and stand space on the growth and crown development of Klassifizierungsproblemenmit Hilfe der mehrdimensionalen Scots pine (Pinus sylvestris)]. Forst Holz 64:23–31 (in Ger- Varianzanalyse [Solution of classification problems using the man). multidimensional analysis of variance]. Beiträge für dieForst- Uusvara, O. 1991. Observations about the branchiness and the wirtschaft. 13 (2): 41-48 (in German). wood quality of young plantation-grown Scots Pine .Metsän- Schädelin, W. 1942. Die Auslesedurchforstung als Erziehungs be- tutkimuslaitoksen tiedonantoja 370, Helsinki. trieb höchster Wertleistung [Selective thinning as a tending Vaartaja, O. 1950.On factors affecting the initial development of operation of highest performance]. 3rd editon, Bern-Leipzig, pine. Oikos 2 (1): 89-108 147 pp. (in German). Schwappach, A.F. 1908. Die Kiefer. Wirtschaftliche und statist- Received 02 July 2014 ischeUntersuchungen der forstlichen Abteilung der Hauptsta- tion des forstlichen Versuchswesens in Eberswalde [The pine. Accepted 25 January 2016

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