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

JUHÁSZ M. & DÉNES A.: BIOMONITORING OF ALLUVIAL WILLOW FORESTS 17 Lysimachia vulgaris, Symphytum officinale. In case of untouched natural conditions this growing place is more wet; rarer and lower floods - relative drying of habitat - is indicated by masses of disturbance tolerant and weed species. Most common disturbace tolerant species is Rubus caesius; in some places Galium aparine, Urtica dioica, Glechoma hederacea can be found in masses too. Amongst alien invasive species Impatiens glandulifera is very frequent, Solidago gigantea is rare. Distribution of species by coenological characterictics in Vízvár plot are shown in Fig.4. It shows that this study stand is determined mostly by two large species groups: local characterstic species of willow forests and disturbance tolerant species. In case of good water conditions proportion of local characterstic species of willow forests increases, in dryer years proportion of natural disturbance tolerant and invasive species rises. Results based on presence-absence data on the lefthand side of the figure show finer coenological composition of the community. According to their species number general species of gallery softwoods and swamp and wet meadow species are well represented too. Fig.5. shows changes of distribution of species in Vízvár plot by relative water demand. On 12-degree scale of relativ water demand species occur also between values 4-10; but this stand is determined first of all by plants of moist soils. By surveys and analysing of diagrams we cocluded that Vízvár plot is a little dryer than Ortilos plot. It is shown also by the diagram of distribution of species by social behaviour types (Fig.6). Natural communities of floodplains need floods, need temporary water cover; if it is left out, weeds and degradation follow. Relative dryness of Vízvár plot is indicated by significant proportions of natural disturbance tolérants, native weeds and alien invasive species. Generalists and competitors, indicating natural conditions are also present, so species pool is given for complete regeneration of the community in case of appropiate water conditions. Conclusions Coenological studies of alluvial willow forests along river Drava were accomplished in five consequent years. Year-to-year changes in coenological characteristics of the community were pointed out. Analysis of data and field observations unambigiously prove that experienced changes are connected closely with changes of water supply of the growing place. Preservation of natural state of the community needs floods of the river temporal surface flooding of alluvial habitats connected to them.