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Acta Silv. Lign. Hung., Vol. 7 (2011) The Riparian Alder Forests of the Sopron Hills Ferenc SZMORAD * Aggtelek National Park Directorate, Jósvafő, Hungary Abstract The present study demonstrates
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Acta Silv. Lign. Hung., Vol. 7 (2011) The Riparian Alder Forests of the Sopron Hills Ferenc SZMORAD * Aggtelek National Park Directorate, Jósvafő, Hungary Abstract The present study demonstrates the classification of the riparian alder forests of the Alpokalja region through the analysis of their stands in the Sopron Hills. Besides the historical, ecological and floristic data collection, the differentiation of these forests was examined using 36 coenological relevés recorded according to the Braun-Blanquet method. Cluster analysis, principal component analysis and TWINSPAN analysis were applied in the process; the definition of diagnostic species for the resulting units was carried out by fidelity analysis using the Ф coefficient. The presence of three alder forest associations was verified by the research in the study area. In the vicinity of the lower and middle sections of the streams, characterized by stagnant water, small patches of swampy alder forests (Angelico sylvestris Alnetum glutinosae) occur. In the fast-flowing stream sections alder woods rich in species of mesophilic deciduous forests (Aegopodio Alnetum glutinosae) can be found, while along the middle and upper sections of the streams, at sites with seepage water, mixed ash-alder forests with montane herb species (Carici remotae Fraxinetum) are typical. The investigations revealed that the Carex brizoides dominance-type alder groves were secondary forests that formed in former meadows and they belong to the 3 mentioned riparian alder forest types. riparian alder forests / phytosociology / Sopron Hills Kivonat A Soproni-hegység égerligetei. Jelen tanulmány az Alpokalja égerligeteinek osztályozási problémáit a Soproni-hegység állományainak elemzésén keresztül mutatja be. A történeti, ökológiai és florisztikai adatgyűjtés mellett a szerző a ligeterdők differenciálódását Braun-Blanquet módszere szerinti 36 cönológiai felvétel felhasználásával vizsgálta. A feldolgozás során cluster-analízis, főkomponens-analízis és TWINSPAN-elemzés készült, az elkülönített egységekre a diagnosztikai fajok kimutatása a hűség-értékek Ф koefficiens szerinti számításával történt. Az elemzések alapján a hegység területén három égerliget-asszociáció jelenléte volt igazolható. Az alsó és középső patakszakaszok kiszélesedő, pangóvizes részein kis foltokban láposodó égerligetek (Angelico sylvestris Alnetum glutinosae) fordulnak elő. Ugyanebben a fekvésben a patakok gyors folyású szakaszain üde lomberdei fajokban gazdag égerligetek (Aegopodio Alnetum glutinosae), míg a középső-felső patakszakaszok szivárgó vizes termőhelyein montán elemekkel színezett, kőriselegyes égerligetek (Carici remotae Fraxinetum) jellemzőek. A vizsgálatok feltárták, hogy a Carex brizoides dominancia-típusú égerligetek egykori rétek helyén kialakult, másodlagos jellegű erdők, s a fenti három égerliget-típushoz tartozó állományokat foglalnak magukba. égerligetek / növénycönológia / Soproni-hegység * H-3758 JÓSVAFŐ, Tengerszem u. 1. 110 Szmorad, F. 1 INTRODUCTION The near-natural vegetation of the border region between the Alps and the Pannonian Basin has a strong transitional character due to the combined effects of the sub-atlantic and subcontinental (and to a smaller extent sub-mediterranean) climates. The montane influence and the occurrence of montane plant species is most remarkable in the regions of the Kőszeg and the Sopron Hills, which can primarily be explained with the direct biogeographical connections, and the orographical characteristics of the two regions (ridges exceeding the height of 800 and 600 m a.s.l., respectively). The montane characteristics can be best detected in the riparian alder forests along the streams in both regions (see Szmorad 1994, Király Szmorad 2004a) where the microclimatic conditions of the stands situated between beech forests allow the occurrence of numerous montane plant species. On the other hand, the alder forest sections of the foothills resemble more of the stands described in the inner basin, while secondary stands formed as a result of earlier anthropogenic impact are also possible to be found. This complexity of the situation makes it difficult to create a coenological classification of these alder forests; the different syntaxonomical systems of the two neighboring countries, Austria and Hungary (see Wallnöfer et al. 1993, Kevey Borhidi 1996, Borhidi 2003, Willner 2007, Kevey 2008), and the different interpretations of the associations in the Austrian and Hungarian literatures further complicate this issue. The classification issues are presented in this paper as a case study on the alder forests in the Sopron Hills region, divided by the Hungarian-Austrian border (see Szmorad 2010). There are only a few short descriptions of the alder woods of this area from the Hungarian side (Soó 1941, Csapody 1964), whereas no research has been carried out on the Austrian part. There are very few coenological relevés published that could be analyzed, and most of the riparian stands have never been subject to vegetation research. The coenological, ecological and phytogeographical characterization of the stands also considering historical aspects have not yet been carried out and the question of the montane riparian ash-alder forests has not yet been resolved (see Kevey 2008). 2 STUDY AREA The Sopron Hills are the north-eastern subrange of the Alps reaching furthest into the Pannonian Basin together with the Kőszeg Hills. They are of medium height. To the west they are separated from the adjacent, nearly north-south running Rosalia Hills by a saddle above the village of Sieggraben. The area of the Sopron Hills is approx. 150 km 2 (Király 2004). Concerning the area s geology, the formations of two geological epochs play a major role: in the eastern part of the hills an island-like extrusion of a palaeozoic schist block (consisting of muscovite-gneiss, mica slate, quartzite and leucophyllite) can be observed (Vendl 1929) while the western part between that and the Rosalia Hills is covered with Miocene sandy, gravel clay sediments (Vendl 1930, Küpper 1957). On the southern face of the hills (between Ritzing and Neckenmarkt, also south of Kalkgruben) there are intrusions of Leitha limestone, while acidic sandstones (between Neckenmarkt and Harka) add to the geological structure, as well (Draganits 1996). In the north-western part of the region, significant areas are covered with a Badenian clay sequence (Fuchs Grill 1984). The main ridge runs in West-East direction, its highest point is the Brenntenriegel (606 m a.s.l.) situated within Austrian territory. The surface structure is defined by wide and flat ridges and slopes of varying steepness. The valleys are usually deeply cut in the schists, thus they are narrow with an upper-course character, without alluvial valley floors (Kárpáti 1955). The riparian alder forests of the Sopron hills 111 On the other hand, the valleys that formed on the Miocene sediments show mostly middlecourse characteristics, their streams often meander on the m wide alluvial valley floors. The hydrographic network of the area consists of small streams. Along their upper sections and in the vicinity of valley heads seeping springs are frequent, whereas smaller hallows with stagnant water appear along the middle and lower sections. The typical soil types of the valley floors are wet (in some cases affected by seeping or stagnant waters) alluvial and colluvial forest soils (Csapody Neuwirth 1963). On wider valley floors the site conditions are more defined by the groundwater. The climate of the region is basically cool with high precipitation. However, a definite macroclimatic gradient can be observed west-easterly; while the eastern hill front is warmer and dryer, the western, inner area is much cooler and has higher precipitation. The mean annual temperature varies between 8 9 ºC, and the annual precipitation usually between mm (Király 2004). From the phytogeographical point of view the Sopron Hills are situated in the border region of the Alpine (Alpicum) and the Pannonian (Pannonicum) floristic provinces. The phytogeographical classification of the area is difficult, since the detectable floristic gradients (Király Szmorad 2004b) indicate a transitional nature and a dualistic character, which often appears in the forest vegetation as well. 3 FORMER RESEARCHES The first references to the riparian alder forests of the Sopron Hills can be found at Gombocz (1906); later Soó (1941) studied the area. The latter mentions alder forests (Alnetum glutinosae) and ash-alder woods (Fraxineto Alnetum) based on some coenological relevés recorded on a single site at the upper section of the Rák Stream. He distinguished several different types (for the former Phragmites communis Caltha palustris, Carex remota, Impatiens noli-tangere, for the latter Veratrum album, Carex brizoides, Chrysosplenium alternifolium, Petasites hybridus types) and summarized his data in a synoptic table. After World War 2 the reviving Hungarian botanical research was mostly confined to the eastern part of the hills due to the state border zone. The essay of Orlóci Tuskó (1955), from this period mentions riparian forests dominated by black alder (Alnetum incanae Alnus glutinosa consociation) and mixed ash woods (Cariceto remotae Fraxinetum). In his phytogeographical study using mainly earlier data Kárpáti (1956) describes alder woods under the name Alnetum glutinosae-incanae in the Sopron Hills region and ash woods (Cariceto remotae Fraxinetum) in the Vadkan and Tacsi Valleys, the Fáber Meadow and the Nagyfüzes areas. The riparian forests along the streams of the eastern half of the Sopron Hills were examined in detail by Csapody (1964). The montane alder forests that he named Alnetum glutinosae-incanae Br.-Bl were characterized on the basis of 9 relevés and he also described the ash woods under the name Carici remotae Fraxinetum Koch 1926 orientialpinum Knapp 1942, publishing a single relevé. The potential vegetation map of Csapody et al. (1964) can be considered an addition to this study; the authors indicated montane alder forests in some sections of the Zsilip Valley, Hidegvíz Valley and the valleys of the eastern rim of the hills, as well as small ash wood stands in the head part of the Kovács Valley and two spots in Nagyfüzes. There was no significant research concerning the riparian alder forests of the Hungarian part of Sopron Hills following the previously mentioned ones; the botanical studies published until the early 2000 s only refer to earlier works and try to interpret these. Based on the floristic research of the region Király Szmorad (2004a) provide a very short description of 112 Szmorad, F. the riparian stands (Aegopodio Alnetum, Carici brizoidis Alnetum) whereas the historical aspects of the research on alder forests in the Alpokalja region are shortly summarized by Baranyai-Nagy Baranyai (2008). Publications about the Austrian side of the research area could not be found, and besides the general descriptions neither the work of Wallnöfer et al. (1993) nor that of Willner (2007) provides help concerning the coenological classification of the local riparian forests. 4 METHODS I studied all the stream valleys of the Sopron Hills (ca 130 km) in the course of my research and tried to gather all relevant data and information concerning the site characteristics, structure, species composition, earlier management, naturalness and dynamics of the riparian alder forests. For the documentation and detailed examination of these stands I have recorded 30 relevés with the classical coenological method (Braun-Blanquet 1951). The size of the sample areas was either or meters (= 400 m 2 ). The plots were not permanent; data acquisition was carried out once in May or June. When choosing the sampling plots I avoided disturbed and weedy stands (preferential sampling). Thus they were designated in middle-aged or old-growth stands with high naturalness and without conifers (in order to avoid the influence of such plantations, which had affected riparian sites, as well). Besides my own ones I have included some (6) relevés by Csapody ( ), surviving as manuscripts. These were also taken in the early summer and represented riparian forests with high naturalness. However, I have omitted some of Csapody s data (1964) since they were recorded in strongly disturbed stands as the high number and cover values of the species indicating disturbance would have strongly distorted the results of the comparative coenological analysis. In the course of analysing the coenological data with multivariate methods I first used the SYN-TAX 2000 software package (Podani 2001). Before the analysis the cover values of the tree species in the canopy, shrub and herb layers were assembled by species and the A-D values were converted into percentages equal to the central values of the intervals. In case of binary data the Jaccard index was applied for the cluster analysis, while the data transformed using logarithmic standardization (base 2 and 10) were analyzed using the Beta-flexible method (value: 0.25) and the Bray-Curtis index. Principal component analysis (PCA) was applied for ordination. I have also analysed the coenological data with the TWINSPAN method. This method of Hill (1979) is based on reciprocal averaging (correspondence analysis).the data have been processed with the 7.0 version of the JUICE software package (Tichý 2002, Tichý Holt 2006). Before the analysis the cover values of the tree species in the shrub and herb layers were assembled by species and the A-D values converted to percentages equal to the central values of the intervals. I chose the level of pseudospecies as 3; their values are 0, 5 and 25%. The TWINSPAN analysis was run with the maximum number of divisions (6) and I interpreted the resulting classification according to the level of the divisions. I have assigned the diagnostic species for the riparian alder forests for the finalized groups of relevés. Following the method of Chytrý et al. (2002) I defined these by calculating the fidelity values according to the Ф-coefficient. The table of synthetic data (fidelity, constancy) is published with Ф = 0.30, using Fischer s exact test (P 0.05) in order to emphasize species with high fidelity and to avoid bias due to small sample size. The results from the analysis of the coenological relevés were evaluated (including the experiences of the field trips) and the vegetation types derived from classification were The riparian alder forests of the Sopron hills 113 matched with the coenological units. Finally, I prepared the concise description of the region s alder associations, including a literature review. The letters in brackets signify the layers (A = canopy layer, BC = shrub and herb layer, C = herb layer, D= moss layer) in the descriptions. Constant and sub-constant species are represented above 60% constancy, dominant species above 60% cover (in the latter case the percentage values signify the frequency of the dominant occurrences). I used the vascular plant names of the identification book edited by Király (2009) while moss names are based on the checklist of Erzberger Papp (2004). 5 RESULTS 5.1 General results of the field research As stand types associated with streams, alder woods can be found in any valley of the Sopron Hills. Besides the continuous, ribbon-like stands there are some occurrences limited to short valley sections in the north-western and south-eastern part of area on sand-gravel sediments with lower clay content. The latter phenomenon is most apparent south of Marz (in the valley between Gruskogel and Hochkogel), and above Neckenmarkt (in the valley of the Goldbach) mainly due to intermittent streams absorbed by the loose ground. Besides the riparian stands in some parts of the hills (e.g. around Asztalfő) alder woods of similar character appear on wet patches close to springs. In the narrow valleys of the eastern part formed on schist, the alder stands are narrow, often only a single line wide. More extensive (with an extent of m) alder woods which are more suitable for coenological analysis only occur in the valleys of the area covered with sedimentary rocks. The original site conditions of these forests have been modified in many places by road and leat constructions, stream regulation works, drainage structures, buildings and artificial lakes (in the Austrian part nearly 30 ponds) during past centuries. Although such anthropogenic effects have influenced the sites of the alder stands (mainly the hydrological balance), most of them can still be considered quasi natural. On the other hand, former land use practices have significantly reduced the extent of the alder stands. The forests on the floodplains of the lower and middle stream sections were cut down centuries ago and replaced by extensive meadows. Many of the meadows are still managed (especially on the Austrian side), however, a large-scale reforestation process started in the 1950 s (see Baranyai-Nagy Baranyai 2008). Non-native tree species were also introduced therefore many stands of Picea abies, Pinus sylvestris and Populus euramericana can be seen on the valley floors. In the lower valley sections (near settlements and orchards) Juglans regia often occurs subspontaneously. In the riparian alder woods Alnus glutinosa is the dominant tree species, but the stands are usually mixed. Of the accompanying species Fraxinus excelsior can play a major (even codominant) role (especially along the upper stream sections, in wet or seepage sites). Alnus incana is generally missing; there are only two records of this species in the area. The Loipersbach Herrentisch occurrence is probably located in the Aubach valley, while the NNW Deutschkreutz in one of the alder woods at the south-eastern foot of Sopron Hills (see Király et al. 2004). The quasi natural stands of the Sopron Hills alder woods are very diverse and also show significant variability in terms of structure and species composition. The differentiation of the wood types is mostly determined by their vertical location, the morphological characteristics of the valley floor, the depth of the stream bed and water availability but earlier land use practices (meadow management, forest usage, etc.) also seems to have a major influence. 114 Szmorad, F. Depending on the background variables the different types of riparian forests are often alternately positioned along the longitudinal axis of a valley. The coenological characteristics of the riparian forests are defined by the species of mesophilic deciduous forests (Fagetalia) and riparian forests (Alnion incanae) but in sites with stagnant water some species of swamp forests (Alnetea glutinosae) and wet meadows (Molinetalia) also appear. According to the prior field studies the proportion of the coenological species groups within the stands (both with regard to species composition and cover) changes mainly depending on the water supply. Alder woods have a considerable spring aspect, except for the stands nearing swamp state. The most frequent species include Adoxa moschatellina, Anemone ranunculoides, Anemone nemorosa, Chrysosplenium alternifolium, Ranunculus ficaria, Lathraea squamaria while Allium ursinum, Corydalis cava, Dentaria enneaphyllos, Isopyrum thalictroides occur less often. The alder woods with an upper-course character are important sites of the montane plant species of Sopron Hills. Pleurospermum austriacum used to grow on the edge of a riparian alder wood and Antriscus nitida, Doronicum austriacum, Equisetum sylvaticum, Gentiana asclepiadea, Lysimachia nemorum, Petasites albus also partly or entirely occur in such woods (Király et al. 2004, Szmorad 2008). The occurrence of nume
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