PHYTOSOCIOLOGICAL ANALYSIS OF RIVERINE FORESTS ALONG THE SAVA BOHINJKA, RADOVNA, UČJA AND SLATENIK RIVERS IN NORTHWESTERN SLOVENIA FITOCENOLOŠKA ANALIZA LOGOV OB SAVI BOHINJKI, RADOVNI, UČJI IN SLATENIKU V SEVEROZAHODNI SLOVENIJI Igor DAKSKOBLER1,2 & Andrej ROZMAN2 ABSTRACT UDC 630*26(497.452):581.9 IZVLEČEK UDK 630*26(497.452):581.9 Phytosociological analysis of riverine forests along the Fitocenološka analiza logov ob Savi Bohinjki, Radovni, Sava Bohinjka, Radovna, Učja and Slatenik Rivers in Učji in Slateniku v severozahodni Sloveniji northwestern Slovenia Po standardni srednjeevropski metodi smo Applying the standard Central-European method we fitocenološko raziskali obrežne gozdove ob rekah Savi Boh- conducted a phytosociological study of riverine forests along injki, Radovni, Učji in potoku Slatenik v severozahodni the rivers Sava Bohinjka, Radovna, Učja and the Slatenik Sloveniji in jih primerjali s podobnimi logi v povodju Soče brook in northwestern Slovenia and compared them to sim- ter v sosednjih državah Hrvaški, Avstriji in Italiji. Na podla- ilar riverine forests in the Soča river basin and the neigh- gi te primerjave smo jih uvrstili v naslednje sintaksone: Sa- bouring countries of Croatia, Austria and Italy. Based on licetum eleagno-purpureae, Salicetum albae, Lamio or- this comparison they were classified into the following syn- valae-Salicetum eleagni (tudi v novo subasociacijo -cari- taxa: Salicetum eleagno-purpureae, Salicetum albae, cetosum eletae) in Lamio orvalae-Alnetum incanae (tudi Lamio orvalae-Salicetum eleagni (also in the new subas- v novi subasociaciji -fraxinetosum excelsioris in -rhamne- sociation -caricetosum eletae) and Lamio orvalae-Alne- tosum fallacis). Opisali smo sukcesivno nadomeščanje tum incanae (also in the new subassociation -fraxineto- (conacijo) združb ob Savi Bohinjki od inicialnih prodišč sum excelsioris and -rhamnetosum fallacis). We described proti bukovim združbam na višje ležečih rečnih terasah. S successive replacement (zonation) of communities along the fitoindikacijko metodo smo ocenjevali produkcijsko sposob- Sava Bohinjka from initial gravel beds towards beech com- nost gospodarsko najvrednejše oblike preučenih logov, ses- munities on higher lying river terraces. Applying the phy- tojev subasociacije Lamio orvalae-Alnetum incanae toindication method we evaluated the production capacity fraxinetosum excelsioris. of economically the most valuable type of the studied river- Ključne besede: fitocenologija, sinsistematika, Alnion ine forests, stands of the subassociation Lamio orvalae-Al- incanae, fitoindikacija, Natura 2000, Bohinj, Julijske Alpe, netum incanae fraxinetosum excelsioris. Triglavski narodni park, Slovenija Key words: phytosociology, synsystematics, Alnion in- canae, phytoindication, Natura 2000, Bohinj, Julian Alps, Triglav national park, Slovenia 1 Dr., the Jovan Hadži Institute of Biology of the Scientific Research Centre of the Slovenian Academy of Sciences and Arts, Regional research unit Tolmin, Brunov drevored 13, SI-5220 Tolmin, [email protected] 2 Dr., Biotechnical Faculty of the University of Ljubljana, Department of Forestry and Renewable Forest Resources, Večna pot 83, 1000 Ljubljana, [email protected] FOLIA BIOLOGICA ET GEOLOGICA 54/2, 37–106, LJUBLJANA 2013 I. DAKSKOBLER & A. ROZMAN: PHYTOSOCIOLOGICAL ANALYSIS OF RIVERINE FORESTS ALONG THE SAVA BOHINJKA 1 INTRODUCTION Bohinj is a relatively well-preserved Alpine landscape alder (Alnus incana), exceptionally also white willow with numerous natural, cultural and historical specif- (Salix alba), as well as mixed deciduous stands with ics. The central water artery of this Alpine valley, dominating European ash (Fraxinus excelsior). Spruce which has been largely transformed by glaciers, is the (Picea abies) and beech (Fagus sylvatica) have estab- Sava Bohinjka, the river that springs in Ribčev Laz lished themselves on slightly more elevated terraces. where Jezernica and Mostnica come together and The softwood riverine forest (grey willow, grey alder whose headwaters are the Savica river that flows into forests) is a distinctive component of the montane (Al- lake Bohinj. The cultural landscape along the river is pine) landscape that plays an explicitly protective role, now dominated by meadows and smaller settlements, so it is imperative that it stays protected also in the and forest growth is limited to a narrow belt (hedges), future. The aim of our phytosociological analysis was with only a few larger areas of periodically flooded for- to gain insight into its species composition, syndy- est stands preserved. These were found and recorded namic processes and its similarity (dissimilarity) in along the Savica before its outfall in Lake Bohinj, along comparison with already studied riverine forests along the Sava at Bohinjska Bistrica, and the largest forest the Soča and its tributaries in the Primorje part of the stands on both sides of this river near Nomenj and Julian Alps (Dakskobler, Šilc & Čušin 2004, Dak- Soteska. There are no major barriers or other interven- skobler 2007, 2010) and with the general appearance tions into the river course in this part of the river, of riverine forests in Slovenia (Dakskobler, Kutnar which allows for formation of young gravel beds with & Šilc 2013). The comparative analysis included wil- intial grey (Salix eleagnos) and red willow (Salix purpu- low and grey alder forests along three small montane rea) stands, riverine forests of grey willow and grey rivers, Učja and Slatenik in the Soča river basin and Figure 1: Approximate localities of researched stands in northwestern Slovenia Slika1: Približna nahajališča raziskovanih sestojev v severozahodni Sloveniji 38 FOLIA BIOLOGICA ET GEOLOGICA 54/2 – 2013 I. DAKSKOBLER & A. ROZMAN: PHYTOSOCIOLOGICAL ANALYSIS OF RIVERINE FORESTS ALONG THE SAVA BOHINJKA Radovna in the Sava river basin, none of which had riverine forests along the Sava Bohinjka (stands of the been studied before. The floristic composition of river- syntaxon Lamio orvalae-Alnetum incanae fraxineto- ine forests of grey willow, grey alder and European ash sum excelsioris) are also commercially interesting, so in Slovenia was compared to similar riverine forests in we evaluated their production capacity applying the northern Italy, Austria and northern Croatia. Some phytoindication method. 2 METHODS Vegetation of riverine forests along the Sava Bohinjka tality (K), light conditions (L), moisture (M), soil reac- River was researched applying the Central-European tion (R), nutrients (N), humus content (H) and aera- method (Braun-Blanquet 1964). A total of 49 rel- tion (A). In our calculations we used van der Maarel’s evés were made between Ukanc and Soteska (Figure ordinal plant cover values as weight that was reduced 1). The comparative analysis considered also 23 pre- by half in indicator values with a higher degree of var- viously unpublished and uprocessed relevés of river- iation (Landolt et al. 2010). ing forests of grey alder in the Upper Soča Valley (the region of Bovec – Bovško) and nine relevés of riverine forests along the Radovna. All these relevés were en- tered into the FloVegSi database (T. Seliškar, Vreš & where WApop is the weighted average of indication A. Seliškar 2003). Combined cover-abundance val- values of plant species for an ecological factor on a rel- ues were transformed into ordinal values (van der evé, FVi is the phytoindication value of the ith species, Maarel 1979). Numerical comparisons were made Abundi is cover value, VRi is range of variation of phy- with the software package SYN-TAX (Podani 2001) toindication value (I = 1, II = 0.5) and s the number of and R (R Development Core Team 2012), using the species in a relevé. package “vegan” (Oksanen et al. 2012). The relevés The nomenclature source for the names of vascu- were compared using the following methods: “(Un- lar plants is the Mala flora Slovenije (Martinčič & al. weighted) average linkage” – UPGMA, “Incremental 2007). Martinčič (2003, 2011) is the nomenclature sum of squares” – MISSQ and “Principal Coordinates source for the names of mosses and Suppan, Prügger Analysis” – PCoA. Wishart’s similarity ratio was ap- & Mayrhofer (2000) are the nomenclature source for plied in all comparisons. These comparisons formed the names of lichenicolous fungi. The nomenclature the basis for four analytic tables (Tables 1–4). The es- sources for the names of syntaxa are Theurillat tablished syntaxa were compared to similar, already (2004) and Šilc & Čarni (2012). The data on the geo- described communities of grey alder riverine forests logical bedrock follow Jurkovšek (1987 a, b) and in the Soča Valley, northern Italy, northern Croatia Buser (1986, 1987, 2009); the source for the nomencla- and Austria (Table 5). This synthetic table provided ture of soil types are Urbančič et al. (2005). Some cli- the basis for the description of several new syntaxa. matological and hydrological data are taken from Ku- The comparison of site conditions in commercial- naver (1998) and Kolbezen (1998). The climate data ly more valuable riverine forests along the Sava Bohin- (precipitation volume, mean temperature) were ob- jka was conducted using Ellenberg’s (Ellenberg et al. tained on the website of the Environmental Agency of 1991), Landolt’s (Landolt et al. 2010) and Košir’s the Republic of Slovenia, Ministry of Agriculture and (1992) indicator values. In relevés we determined aver- Environment (http://www.arso.gov.si/). age conditions in terms of temperature (T), continen-