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
12 NATURA SOMOGYIENSIS Climate of this area is moderately warm, humid. Annual mean temperature is between 9,7°C and 9,9°C. Hottest summer days' average of many years is about 32,5°C, of coldest winter days is -17,0°C. Annual precipitation 800-840 mm, of which 450-490 mm falls in growing season. Most frequent wind direction is northern, second-frequent is southwestern. Floods of Drava comes in spring, early summer and autumn, low waters in late summer and winter. There are quaternary deposits in the Drava valley with fluvial and floodplain sand, gravel and mud (MARKÓ-JUHÁSZ 1997). In this area Drava is not constrainted in between dams, so it can change her bed even in our days. Surface of floodplain can be divided into low and high floodplain levels, oxbows and oxbow lakes. Elevation differences make only some meters. Groundwater can be reached anywhere between 0-4 meters, its quantity is reasonable, its level changes are in accordance with level changes of the river. Materials and methods Study areas were appointed inside the area effected by the planned power plant. Willow forest near Őrtilos is upstreams of the planned plant, the other one near Vízvár is downstreams of it. Permanent quadrats were assigned in typical parts of the given stand. (JUHÁSZ 1997, 2004, ORTMANN-NÉ AJKAI 2004). Near Őrtilos, according to terrain characteristics, one 20x10 m and one 20x5 m study plot were assigned, whose data were drawn together in Figures. Study plot near Vízvár is 100x25 m, continuously. Inside permanent quadrats microquadrats of lxl m size, chosen by semi-random way, were surveyed; in the smaller Őrtilos plot 30, in larger Vízvár plot 50 ones. Our aim was to represent all parts of the plots by the same chance. Surveys were made in the same part of the year in all study years, in June. Willow forests were surveyed by estimation of coverage percentages, as usual in phytocoenology. Studied variables: coverage of herb species in all microquadrats and coverage of canopy and shrub layer in permanent quadrats. Results Studied willow forests of both plots belong to Leucojo aestivi-Salicetum albae community (BORHIDI & KEVEY 1996). Data of surveys were ordered into coenological tabellas and analysed in various ways. In the following changes of coenological spectra of communities and changes of distribution of species by relative water demand and social behaviour types (BORHIDI 1995) are presented. In Figs 1-6 left-hand bars show results based on coverage data (est), right-hand bars show results based on presence-absence data (csr). More important growing place and coenologial characteristics of the study plot near Őrtilos are as follows. Here the left-side floodplain of Drava is very narrow, from the river (state border) to the loess hillfoots only 100-1100 m. Whole area is low floodplain, whose caharacteristic natural vegetation are willow forests. On appointed study plots canopy cover is between 25-70%. Most important dominant tree is Salix alba, beside it Alnus glutinosa and Alnus incana can be found. Humulus lupulus is a lian climbing up to canopy. Shrub layer is thin, its coverage is max. 10%, consists of Cornus sanguinea
