Studi Trent. Sci. Nat., Acta Geol., 82 (2005): 101-107 ISSN 0392-0534 © Museo Tridentino di Scienze Naturali, 2007

Dendroecology and dendrochemistry in : the Grotta di Ernesto project

Jonathan G.A LAGEARD1, Nicola LA PORTA2, Peter A. THOMAS 3 & Neil J. LOADER4

1 Department of Environmental & Geographical Sciences, Manchester Metropolitan University, John Dalton Building, Chester Street, Manchester M1 5GD, UK 2 Istituto Agrario di San Michele all’, Via E. Mach 1, 38010 San Michele all’Adige (TN), 3 School of Life Sciences, Keele University, Staffordshire ST5 5BG, UK 4 Department of Geography, University of Wales, Swansea SA2 8PP, UK

SUMMARY - Dendroecology and dendrochemistry in Trentino: the Grotta di Ernesto project- Sampling and analyses for dendroecological and dendrochemistry studies have been carried out in forests of Trentino, south-eastern Italian , to complement the extensive speleothem database and recognize tools for cross-correlation of the two archives. Dendroecological data will be compared with the series of winter temperature and anthropogenic sulphate concentration trend obtained from three stalagmites sampled at the Grotta di Ernesto cave. The main objective of the investigation is to analyse different aspects of anthropogenic impacts recorded by the tree-ring series, such as variability in the load of pollutants and land use changes, and discriminate them from natural phenomena. We also aim at recognizing ecosystem storage of sulphur, which has been recognised in speleothem studies. Sampling was carried out for trees growing within 1000 m radius around the cave. We selected trees which had a minimum of 50 and 150 annual rings, a requirement for both computer assisted dendrochronology and isotope analysis. 85 trees belonging to the species Fagus sylvatica, Larix decidua, Picea abies and Abies alba were sampled through Pressler coring. Planned analyses included traditional dendrochronology, dendroclimatology (measuring carbon and oxygen isotopes and blue light refl ectance) and dendrochemistry (extraction of sulphur). The dendroecological data obtained by the study will be compared and correlated with meteorological series from 5 permanent stations dating back to 1812. The tree-ring data will be also compared with isotope values extracted from growth annual laminae developed from the year 1900 to the year 2000 AD in stalagmites from Grotta di Ernesto.

RIASSUNTO - Dendroecologia e dendrochimica in Trentino: il progetto Grotta di Ernesto - Un campionamento a scopi dendroecologici e dendrochimici su anelli di accrescimento annuali degli alberi è stato effettuato in vicinanza della Grotta di Ernesto (, TN) per confronto con serie di temperature medie invernali e di concentrazione di solfato antropogenico ottenute da tre stalagmiti della grotta. Il principale obbiettivo dello studio era analizzare i diversi aspetti delle trasformazioni antropogeniche registrate nelle serie degli anelli degli alberi dovute a inquinamento ambientale o cambiamento dell’uso dei suoli, e distinguerle da fattori naturali. Di particolare interesse è riconoscere fenomeni di immagazzinamento nell’ecosistema di zolfo da emissioni antropogeniche. All’inizio furono identifi cati alberi che crescevano entro un raggio di 1000 m dalla Grotta di Ernesto. Tra questi furono selezionate piante con un minimo di 50 e 150 anelli annuali, richiesti rispettivamente per analisi dendrocronologiche computerizzate e per analisi isotopiche. Ottantacinque piante appartenenti alle specie Fagus sylvatica, Larix decidua, Picea abies e Abies alba furono campionate con una Trivella di Pressler. Le analisi programmate includevano dendrocronologia tradizionale, dendroclimatologia (misurando isotopi di carbonio e ossigeno) e dendrochimica (estrazione di zolfo). I dati dendroecologici ottenuti in questo studio saranno confrontati con archivi di dati da 5 stazioni meteorologiche permanenti, poste a diverse distanze dalla grotta. Gli anelli legnosi saranno in futuro confrontati con i valori isotopici ottenuti dalle lamine di crescita delle stalagmiti della Grotta di Ernesto dal 1900 al 2000.

Key words: dendroecology, dendrochemistry, sulphur, Grotta di Ernesto Parole chiave: dendroecologia, dendrochimica, zolfo, Grotta di Ernesto 102 Lageard et al. Dendroecology and dendrochemistry in Trentino: the Grotta di Ernesto project

1. AIMS OF THE DENDROECOLOGY for the isotope work envisaged here, as there is an age STUDIES NEAR GROTTA effect clearly discernable in the isotopic records of DI ERNESTO SITE tree-rings. A climate signal cannot be found in young trees and therefore the isotopic records for the fi rst 40 The current palaeoclimate and environmental stud- years growth of individual trees are discounted from ies, in particular for the past few centuries, require climatic reconstructions. In an ideal world, tree-ring archives of proxy data with annual to sub-annual records of at least 200 years are desirable for tracing resolution. In the Trento Province both tree ring and environmental impacts related to changing climate speleothem proxy records have made substantial new and to industrial development in . Field contribution to our understanding of natural climate sampling took place between 11th and 20th July 2005 variability and the effects of anthropogenic forcing. In from the excellent base of the Albergo San Marco in particular, the Grotta di Ernesto cave is one of the key and with assistance of the Borgo sites for palaeoclimate and environmental research in Forest District of the Forest Service of Provincia the Alps (Frisia et al. 2003, 2005). Speleothems from Autonoma of Trento (PAT). this cave are temperature-sensitive in their growth rate, An exploratory fi eld investigation in 1997 had and encode in their chemical properties information identifi ed a number of species that might be suitable about atmospheric sulphur load. The forest trees near for this project: Fagus sylvatica (Beech), Larix decid- Grotta di Ernesto, therefore, would allow for multi- ua (European Larch), Picea abies (Norway Spruce) parameter comparison of tree rings and speleothem and Abies alba (Silver Fir). In that pilot study, larch proxy data at least over the past 150 years, which is seemed to have a good response to temperature. A the time interval that is better constrained in the an- search was then undertaken for mature/old trees in nually laminated speleothems (Frisia et al. 2003). In the area above and adjacent to Grotta di Ernesto. As particular, Frisia et al. (2003) not only found evidence can be seen in fi gure 1, the entrance to the cave is for correlation of speleothem growth rate and tem- on the upper slope of Valsugana to the west of the perature, but also identifi ed the 11-year sunspot cycle, village of Martincelli. Many dendroecological stud- which was related to ecosystem response to solar forc- ies have shown that the growth response of trees ing. A dendroclimatological study has the potential located on slopes can often mask meteorological to cast better insight on the interannual variations of signals (Urbinati et al. 1997; Oberhuber et al. 1998; climate parameters and how modes of variability have Oberhuber & Kofl er 2000; Oberhuber 2004) and changed through time. It is important, here, to remind therefore another important consideration was to fi nd that while tree rings are an excellent proxy for the tem- trees rooted on fl at or only gently sloping ground. perature in the growing season, speleothems, at Grotta The circle drawn in fi gure 1 describes a 1 km radius di Ernesto, preferentially record the cold season. centred on the entrance to the Grotta di Ernesto and The present study builds its rationale from the clearly illustrates why the search for suitable trees premise that tree-ring samples collected from trees focused to the west and south of the cave. in the vicinity of Grotta di Ernesto could be used to A further restriction on sampling is the extensive monitor tree response to climatic variables and to area of tree-less pastures. The word “malga” is a com- anthropogenic pollution over the previous 150 years mon prefi x for mountains meaning cattle-shed and can and provide data complementary to speleothem data. be found in many localities on the plateau within circa Planned analyses included traditional dendrochronolo- 6 km to the west/north-west of the cave (M. Aveati, gy, dendroclimatology (measuring carbon and oxygen M. Vacchetta, M. Val Capertadi Sotto, M. Campo di isotopes and blue light refl ectance as climatic proxies) Sopra, M. Val d’Antenne), indicating areas that have and dendrochemistry (extraction of sulphur). been pasture for some considerable time. The mixed forests in the area are predominantly of Picea abies, with Abies alba, Larix decidua and 2. SAMPLING Fagus sylvatica. Mean stand density is typically 250 trees per ha and tree basal area is about 25-30 m2 per Sampling of tree-rings was governed by a num- ha (Virgilietti 1998). Many stands over the last 40 ber of criteria in order to provide suitable samples years have been managed under a silvicultural system, for the analyses identifi ed above. Initially, it was “taglio di curazione”, which is similar to “naturalistic” important to identify trees species growing in the silviculture or a selection system (Ferrari 1984). area immediately surrounding Grotta di Ernesto, This semi-natural conifer forest with beech under- which would provide ring series suitable for basic storey is characteristic of this zone of Trentino at 1000- dendrochronology and, more importantly, ring series 1500 m a.s.l. in the Valsugana (Ferrai & Mazzucchi of suffi cient length to facilitate isotopic analyses. At 1974). Large old beech trees are present scattered in least 50 annual rings are required for computer-as- some parts of the forest, the remains of seed-producing sisted dendrochronology, and 150 rings are needed trees that were present in former beech coppices (Loss Studi Trent. Sci. Nat., Acta Geol., 82 (2005): 101-107 103

Fig. 1 - Location of Grotta di Ernesto on the northern, upper slopes of the Valsugana. Fig. 1 - Ubicazione della Grotta di Ernesto, verso la sommità Fig. 2 - Open pasture area with evidence of sparse re- del fi anco settentrionale della Valsugana. colonization. The whole plateau was once mostly exploited as summer grazing pastures. Fig. 2 - Pascolo aperto con segni di giovane ricolonizzazione & Ferrai 1984), or some were possibly just isolated da parte della foresta. L’altopiano era un tempo sfruttato trees in the pasture. These beech growing together principalmente come pascolo estivo. with larch are mostly found in private forests. Public forests are dominated by almost solely by Picea ab- ies and Abies alba. This major distinction in the forest World War. Ruins of trenches are still to be seen and is the result of the intensive silvicultural management it is not infrequent to fi nd in tree stems with the pres- that was practiced in the beech coppices and the inten- ence of splinters of bursting shells (G. Messina pers. sive grazing under larch trees on private lands. There comm.). are also the remnants of charcoal pits where charcoal Today these areas, formerly kept open due to inten- was made from beech wood and the waste wood from sive summer grazing (Fig. 2), are still being re-colo- conifers. nised by the forest, as it is generally the case in many This forest had been affected quite regularly by mountain regions in the Alps (Piussi & Pettenella disturbance and signifi cant regeneration occurred 2000). As a result, large areas of the plateau are cov- only after 1920 (Motta et al. 2002). Before the war ered by forest younger than 100 years (Fig. 3). the land had been exploited as pasture, as was quite common in such regions (Backmeroff 1996; Piussi 2002), especially where the slope was not excessive. A forest management plan from the ’20s (stored in the Forest District Archives) reveals that people exerted a large infl uence on the forest. Forest management plans for the Grigno area were useful in the interpretation of the data obtained through earlier dendroecological research, although events defi ned in the tree-rings did not always correspond with data from the management plans (yearly thinning, felling, wind-throw damage) as stand-level details were al- ways missing from the plans. These plans dealt with areas of several hectares (Motta et al. 1999). Despite these limitations, the information included in the management plans is of crucial importance in studying stand history, and only by using all sources of information it is possible to delineate and to identify the most important natural and human features of the history and disturbance that affected the origin and Fig. 3 - Forest re-colonisation of the plateau near Colle Dei subsequent growth of the forest stands. Meneghini. In addition to the culture impacts discussed above, Fig. 3 - Ricolonizzazione forestale dell’altopiano vicino al the area was also particularly affected by the First Colle dei Meneghini. 104 Lageard et al. Dendroecology and dendrochemistry in Trentino: the Grotta di Ernesto project

Fig. 4 - Location of large larch trees. Sampling a larch using a Pressler-type increment corer. Fig. 4 - Ubicazione dei larici con diametro del tronco largo. Fig. 6 - Location of wood piles sampled at 2 km (WP1) and Campionamento di un larice con un carotiere tipo Pressler 4 km (WP2) from the Grotta di Ernesto. a incrementi. Fig. 6 - Ubicazione delle cataste di legna campionate a 2 km (WP1) e 4 km (WP2) dalla Grotta di Ernesto.

Due to topographic restrictions and the generally youthful nature of the forest, detailed local knowledge of surviving older trees was essential to the success of the isotope part of the project. Foresters from the Forest Service of PAT took the sampling team to areas where there were large larch (Fig. 4) and beech trees (Fig. 5). Even the largest larch trees, such as the one shown in fi gure 4, were gener- ally only around 90 years old. Beech trees, such as the one illustrated in fi gura 5, were either standing or dead and fallen, all with central rot making them diffi cult to core and even more diffi cult to measure. Although there was strong beech regeneration in parts of the area indicated in fi gure 5a, there was no scope for bridging the dendrochronological gap between the living and dead trees. Fig. 7a - The wood pile WP1. See fi gure 6 for its geographic Attention turned to Norway spruce and Silver fi r. location. As with the larch, it proved very diffi cult to fi nd any Fig. 7a - La catasta di tronchi WP1. Si veda la fi gura 6 per living individuals over 100 years old. The forest- la sua localizzazione geografi ca. ers, however, knew of wood piles composed of trees thought to be old, which had been felled in the winter

Fig. 5 - Location of old beech trees. Sampling a dead Fig. 7b. - Inspecting trunk cross-sections at WP2 to check beech. for century-old trees. Fig. 5 - Ubicazione di vecchi faggi. Campionamento di un Fig. 7b - Ispezione delle sezioni trasversali di tronchi nella faggio morto. catasta WP2 per trovare tronchi centenari. Studi Trent. Sci. Nat., Acta Geol., 82 (2005): 101-107 105 of 2004-2005. Two wood piles were inspected, one impossibility of coring some trunks lodged within less than 2 km from the cave (WP1) and the other 4 the centre of the wood pile. Another drawback was km (WP2) (Fig. 6). Trees piled at each had not been that bark was sometimes missing from the visible transported far after felling and the wood piles also portion of the trunk and species identifi cation could permitted easy viewing of stem cross sections (Fig. only be confi rmed later by microscope examination 7a). Quick ring counts helped to identify a number of of the wood structure. In tangential sections, the rays trees of around 150 years and older. Large diameter of spruce are seen to be comparatively small – 10- trees were not always the old ones (Cherubini et al. 15 (25) cells high – with included resin canals while 1996; Rozas 2003; Jimenez et al. 2003) so being able the rays of fi r are 15-25 (40) cells high without resin to see the cross-sections saved much trial and error canals. coring. This sampling advantage was offset by the Increment cores, 5 mm and 12 mm diameter cyl- inders of wood, were removed using hand-operated Pressler-type corers (Figs 8a-d and Tab. 1). A few replicate disks were also removed using a chainsaw a (Fig. 8e).

c

Fig. 8a - Peter Thomas removing 5 mm and 12 mm cores using a Pressler-type increment borer at one of the wood piles. Fig. 8a - Peter Thomas sta campionando con un carotiere Pressler un tronco in una delle cataste.

b d

Fig. 8b - Jonathan Lageard coring a conifer in life position. The most critical part of the coring is hitting the centre of Fig. 8c and d - Peter (8c) begins coring a large trunk from the tree, which allows to obtain the age of the tree. one of the woodpiles. Jonathan (8d) has reached the centre Fig. 8b - Jonathan Lageard mentre carota una conifera in of a smaller trunk. posizione di vita. La parte più critica del campionamento Fig. 8c e d - Peter (8c) inizia a carotare un tronco piuttosto è centrare l’asse di crescita dell’albero per ottenere l’età largo nella catasta. Jonathan (8d) ha raggiunto il centro di dell’individuo. un tronco più piccolo. 106 Lageard et al. Dendroecology and dendrochemistry in Trentino: the Grotta di Ernesto project

a e

b

Fig. 8e - Sampling with a chainsaw to obtain a whole section of a tree. Fig. 8e - Campionamento di una rotella di legno con una sega elettrica per ottenere l’intera rotella di legno. Fig. 9 - Site chronologies E1_35 from wood pile WP1 and E1_4 from WP2. a. Raw ring-widths, b. detrended. Tab. 1 - Increment cores collected in 1997 and 2005. Fig. 9 - Cronologie E1-35 da campioni provenienti dalla Tab. 1 - Carote campionate nel 1997 e nel 2005. catasta di tronchi WP1 e E1-4 costruita da campioni provenienti dalla catasta WP2. In (a) i dati grezzi di spessore degli anelli di accrescimento degli alberi. In (b) I dati dopo Species No 5 mm cores No 12 mm cores elaborazione (de-trending). Fagus sylvatica 50 Larix decidua 16 0 Picea abies 23 10 Abies alba 24 5 ly made for trees from both wood piles E1_35 (WP1 Ð 12 trees) and E1_4 (WP2 Ð 3 trees) Ð see details in fi gure 9. A comparison of these chronologies with records from living trees confi rmed that the last ring 3. LABORATORY ANALYSES present in both chronologies was laid down in 2004. Twelve mm diameter samples and disks were Increment cores were taken to the Dendrochronology kept for isotope analyses and are currently being Laboratory at Manchester Metropolitan University analysed at the University of Wales in Swansea, in the (UK), where they were mounted on wooden channels Dendrochronology Laboratory. These cores will also and sanded using coarse through to fi ne grit sandpapers be subject to blue light refl ectance analysis which acts to clearly reveal tree-ring wood structure and in par- as a surrogate measurement of ring density, which ticular the boundaries between rings. Tree ring-width is known to correlate well with climate data. Other measurements were then made for each sample using a samples are undergoing trials for sulphur extrac- measuring stage, binocular microscope and specialist tion at the Geography Department of the University computer software. Measurement started with the in- of Birmingham. A successful application has been nermost ring (ring closest to the centre of the tree/pith) made to the European Synchrotron Facility (ESRF) in and followed by a series of consecutive rings towards Grenoble to analyse the molecular state of sulphur via the bark edge. X-Ray near edge absorption spectroscopy (XANES) technique at ID 21, which allow to discriminate sul- phate and sulphide. Other elements will be also ana- 4. INITIAL RESULTS lysed at ID 21 and at very high resolution by means of micro X-Ray fl uorescence spectroscopy within A ring-width record was made for each core and in- individual tree-rings and we expect to obtain also very dividual records were crossmatched (that is compared detailed maps. This technique has been commonly ap- with others for similarity). Using t-value correlations plied to archaeological wood, and will be here applied it was possible to combine contemporaneous series to for the fi rst time for comparison with speleothem data form site chronologies. Chronologies were successful- obtained with the same method (Frisia et al. 2005). Studi Trent. Sci. Nat., Acta Geol., 82 (2005): 101-107 107

Data produced from all the afore-mentioned analy- Cherubini P., Piussi, P., Schweingruber & F.H., 1996 - ses will be compared to meteorological data (monthly Spatiotemporal growth dynamics and disturbances in a and annual means) from meteorological stations listed subalpine spruce forest in the Alps: a dendroecological re- in table 2 and data obtained from analyses of the spe- construction. Canadian J. Forest Res., 26 (6): 991-1001. leothems from Grotta di Ernesto. Ferrai S. & Mazzucchi M., 1974 - Improving the forests in Valsugana: improvement fellings in the coppice stands and high forest. Monti e Boschi, 25 (6): 11-19. Tab. 2 - Meteorological data available for comparison with Ferrari L., 1984 - Forests and forestry in Trento Province, tree-ring data. Italy. Schweizer. Zeit. Forstwesen, 135 (7): 547-612. Tab. 2 - Dati meteorologici disponibili per il confronto con i Frisia S., Borsato A., Preto N. & McDermott F., 2003 - Late dati degli anelli degli alberi. Holocene annual growth in three Alpine stalagmites records the infl uence of solar activity and the North Meteorological Station Data coverage (years AD) Atlantic Oscillation on winter climate. Earth Plan. Sci. Lett., 216: 411-424 Milan 1812-2004 Frisia S., Borsato A., Fairchild I.J. & Susini, J., 2005 - Trento 1875-2004 Variations in atmospheric sulphate recorded in stalag- 1924-2004 mites by synchrotron micro-XRF and XANES analyses. 1921-2004 Earth Plan. Sci. Lett., 235: 729-740. Jimenez J., Kramer H. & Aguirre O., 2003 - Individual tree 1963-2004 growth in an uneven aged mixed coniferous stand based on stem analysis. Allgemeine Forst- und Jagdzeitung, 174 (9): 169-175. 5. FUTURE OBJECTIVES Loss A. & Ferrai S., 1984 - Coppice forests in Trentino: silvicultural and management aspects. Schweizer. Zeit. There is an exciting future for sulphur analyses in Forstwesen, 135 (7): 585-597. tree-rings of specimens collected near a site for which Motta R., Nola P. & Piussi P., 1999 - Structure and stand development in three subalpine Norway spruce ( increasing sulphur concentration trends have been de- Picea abies (L.) Karst.) stands in Paneveggio (Trento, Italy). tected for the past 100 years from the speleothem archive. Global Ecol. Biogeog., 8 (6): 455-471. It is envisaged that ring-width chronologies already built Motta R., Nola P. & Piussi P., 2002 - Long-term investiga- will be strengthened and it may also be possible to work tions in a strict forest reserve in the eastern Italian Alps: up tree-ring chronologies for larch and for fi r. The tree- spatio-temporal origin and development in two multi- ring team is looking forward to collating the results from layered subalpine stands. J. Ecology, 90 (3): 495-507. the range of analyses and to drawing conclusions about Oberhuber W., 2004 - Infl uence of climate on radial growth past climate in the hinterland of Grotta di Ernesto and of Pinus cembra within the alpine timberline ecotone. about the links Sulphur forges between natural and hu- Tree Physiol., 24 (3): 291-301. man modifi ed systems above and below ground. Oberhuber W. & Kofl er W., 2000 - Topographic infl uences on radial growth of Scots pine (Pinus sylvestris L.) at small spatial scales. Plant Ecology, 146 (2): 231-240. ACKNOWLEDGEMENTS Oberhuber W., Stumbock M. & Kofl er W., 1998 - Climate tree-growth relationships of Scots pine stands (Pinus This work is a part of the project AQUAPAST sylvestris L.) exposed to soil dryness. Trees-Structure fi nancially supported by the Provincia Autonoma of and Function, 13 (1): 19-27. Trento. The authors wish to thank Dr. Giorgio Messina Piussi P., 2002 - Spontaneous reforestation and post-agricul- and several other foresters of the Forest Service of the tural development. Monti e Boschi, 53 (3/4): 31-37. Provincia Autonoma di Trento for the very helpful as- Piussi P. & Pettenella D., 2000 - Spontaneous afforestation sistance in fi nding the trees and in collecting samples, of fallows in Italy. Weber N. (ed.), EFI Proceedings, 35: and Dr. Silvia Frisia, who coordinated the project and 151-163. revised the manuscript. Rozas V., 2003 - Tree age estimates in Fagus sylvatica and We thank the UK NERC for research support (NE/ Quercus robur: testing previous and improved methods. C511805/1 and NE/B501504/1). Plant Ecology, 167 (2): 193-212 Urbinati C., Carrer M. & Sudiro S., 1997 - Dendroclimatic response variability of Pinus cembra L. in upper timber- REFERENCES line forests of Italian Eastern Alps. Dendrocronologia, 15: 101-117. Backmeroff C.E., 1996 - The last thousand years history Virgilietti P., 1998 - Application of a matrix growth model of mountain larch in Comasine, Val di Pejo, Trentino. to uneven-aged stands in Valsugana, Trento. Monti e Dendronatura, 17 (1): 61-76. Boschi, 49 (2): 52-58 1998.