Ábrahám Levente: Válogatott tanulmányok II. - Natura Somogyiensis 9. (Kaposvár, 2006)
Juhász Magdolna - Dénes Andrea: Biomonitoring of alder swamp forests - Égeres mocsárerdő monitoring vizsgálata
40 NATURA SOMOGYIENSIS stand - situated in Hungarian effect area of the planned Croatian hydroelectric power plant - and designating exact study area was made in 2000. Permanent quadrat of 50x50m was designated in a typical plot of the stand. Inside it 50 micro-quadrats (lxl m each), chosen by a pseudo-random way were surveyed. Goal of pseudo-random survey was to represent all parts of study area evenly. Field surveys were made at the same time of every year, in June, with estimation of percentage cover, as usual in phytocoenology. Variables studied: covering of herb layer species in all micro-quadrats and covering of shrub layer and canopy in the whole permanent quadrat. Results Alder swamp forest studied belongs to plant community Angelico sylvestri - Alnetum glutinosae (BORHIDI & KEVEY 1996). It is a ground-water influenced forest occurring in depressions of floodplains. During floods the growing place characterized by aerobic processes, because there are a lot of oxigén in the moving water; but time to time there is standing water which induces anaerobic processes to start. Alder swamp forests are two-faced, transitional between alder moors (Car ici elongatae - Alnetum) and hardwood alluvial forests (Carici brizoidis - Ulmetum). Beechwood (Fagetalia) species are missing almost totally, so alder swamp forests are categorized coenotaxonomically into moor forests; but true moor species are also missing, even name-giving species of moor forests, Carex elongata. Herb layer between trees is more closed, characterised by highgrowing sedges (Carex acutiformis, С riparia, C. gracilis, C. vesicarid). Our study site is situated near village Gyékényes. Characteristics of the growing site and the coenosis (Fig.l., Fig.2.) are as follows. Left-side floodplain of river Drava is very wide here, study site can be found on high floodplain level. Effects of floods are indirect, realized through rise of subsoil water level in the gravel bottom. Characteristic natural forest communities in the surroundings: hardwood alluvial forests, in deeper parts alder moors and alder swamp forests. In the designated study plot canopy is monodominated by alder (Alnus glutinosa) with a coverage of 65%. Shrub layer is sparse, its coverage is 20%, consist mostly of Frangula alnus and saplings of Alnus glutinosa. Solanum dulcamara creeps on tree trunks in some places. Between the trees soil is covered with water in most of the year. In the five study years, in June, when surveys were made, water depth changed between 0-80 cm. Eastern and southern part of the plot lies a bit deeper, here water coverage is longer. Coverage of herb layer change mosaically, in micro-quadrats surveyed it was between 0.1-90%. In herb layer Carex acutiformis occurs in masses. Moor-like species: Hottonia palustris, Urtica kioviensis, Thelypteris palustris, Galium palustre, with a significant frequency and abundance. Softwood species: Leucojum aestivum, Galeopsis speciosa, Solanum dulcamara, Stachy s palustris, Scrophularia nodosa, with lesser frequency and abundance. Swamp species are also very significant, most common ones: Sparganium erectum, Oenanthe aquatica, less common ones: Iris pseudacorus, Lysimachia vulgaris, Myosotis palustris, Rorippa amphibia, Alisma plantago-aquatica, Mentha aquatica, Symphytum officinale. At high water level there are floating water plants, e.g.: Lemna minor, Lemna trisulca, Hydrocharis morsus-ranae, Riccia fluitans . Indifferent species are: Ranunculus repens, Lycopus europaeus, Eupatorium cannabinum, which occurs seldom in study plot. After field survey data were arranged into coenological tabelles and analyzed by different methods. Changes of coenological character spectra of communities and changes of relative water demand and social behaviour types (BORHIDI 1995) are presented in the
