Ábrahám Levente: Biomonitoring a Dráva folyó magyarországi szakasza mentén 2000-2004 - Natura Somogyiensis 7. (Kaposvár, 2005)

Juhász, Magdolna - Dénes, Andrea: Biomonitoring of alluvial willow forests - Ártéri fűzligetek monitoring vizsgálata

16 NATURA SOMOGYIENSIS and Viburnum opulus. Coverage of herb layer changes with quantity and duration of surface water cover. Phalaroides arundinacea and Succisella inflexa are determinant local characteristic species of willow forests. Further characteristic species: Carex gracilis, Equisetum hyemale, Galium palustre, Iris pseudacorus. Carex pseudocyperus, Carex vesicaria, Angelica sylvestris, Stachys palustris, Polygonum mite also occur. In some places in the herb layer sometimes swamp and wet meadow species - most often Lysimachia vulgaris and Symphytum officinale - can reach significant coverage. Disturbance tolerant and weed species have significant coverage mostly in drier parts. Most important natural disturbance tolerant is Rubus caesius; Urtica dioica and Galium aparine are also common. Alien invasive species occurring here are Impatiens glandulifera and Solidago gigantea. Distribution of species by coenological characterictics in Ortilos plot are shown in Fig.l. It shows that this study plot is determined by changing proportions of local characteric species of willow forests, swamp and wet meadow species and disturbance tolerant species. In case of long, high water cover swamp and wet meadow species gain space. In years with average water level changes the stand is determined by total coverage of local characteristic species of willow forests. In drier years proportion of natural disturbance tolérants grow. Results based on presenceabsence data on the right-hand side of the figure show finer coenological composition of the community. Here even those coenological groups can be seen which take part in composition of the community with insiognificant cover values. Coenological colouring species like this are species of mesophilous woodlands and indifferent species living in many different communities. Sometimes some species of mesophilous woodland are settle in the study plot; they come supposably from hornbeam-oak forests of the nearby loess hills. Fig.2. shows changes of distribution of species by relative water demand. On 12-degree scale of relative water demand species occur between values 4-10. Community is determined mostly by plants of moist soils and plants of wet, not well aerated soils; their proportions change according to water level changes. Extremities appearing in the study plots are plants of semidry habitats indicating extreme dryness, and water plants of frequently flooded soils indicating extrem wetness. Fig.3. shows distribution of species by social behaviour types in the Ortilos study area. In this respect community is determined by competitors, generalists and disturbance tolérants in changing proportions. In certain years weeds and invasive alien species appear with significant coverage. More important growing place and coenologial characteristics of the study plot near Vízvár are as follows. Left-side flood area of Drava here is also relatively narrow. The river - trying to change her bed - steeply undermines the higher level of the neighbouring land. Floodplain is low, only 0-1000 m wide, its characteristic natural community is alluvial willow forests. In appointed study area canopy is formed exclusively by Salix alba with 65% coverage. Up the trees climb masses of Humulus lupulus and in some places Hedera helix too. Coverage of shrub layer is about 25%, its characteristic species is Cornus sanguinea; Sambucus nigra is also common. Coverage of herb layer shows small changes year by year, according to height and duration of surface water coverage. Amongst local characteristic species of willow forests Phalaroides arundinacea is most common, in some places Carex gracilis and Caltha palustris can also be found in masses. Iris pseudacorus, Angelica sylvestris, Equisetum hyemale, Galium palustre, Carex vesicaria, Myosotis palustris, Polygonum mite, Succisella inflexa also occur. Amongst local characteristic species of alluvial softwoods Galeopsis speciosa is relatively common, Circaea lutetiana and Cucubalus baccifer are more rare. Occurence of swamp and wet meadow species is significant by their species number, more insignificant by their coverage. These species are: Carex acutiformis, Carex elata, Lythrum salicaria,