Matskási István (szerk.): A Magyar Természettudományi Múzeum évkönyve 89. (Budapest 1997)

Szollát, Gy., Stollmayer-Boncz, E. , Standovár, T. ; Kecskés, F.: Vegetation of the Réti-dűlő and Csömöri-tó (Hungary)

Altogether 7 protected and 5 threatened species were found. Table 3 shows the estimated population size of these species, whereas Fig. 2 shows their locations. VEGETATION MATERIALS AND METHODS A 1 : 4000 coloured aerial photograph - taken in June 1992 - was used for assisting vegetation survey. As a result of fast changes in water supply, the most valuable swamp and fen communities of the area are not always typical in their appearance. They form a complex, containing small fragments of different associations in close proximity. This is the reason why the units used for preparing the vegetation map of the area are not necessarily identical with any traditional phytosociological association. Some of them are the products of human activity (arable field, fallow, Robinia pseudo-acacia plantation). Researches of the Csömöri-tó started in the early 1980's. As major changes have taken place since that time, it is important to give a short summary of them to be able to assess the present status. About half of the Csömöri-tó was covered by open water hosting floating plant communities. There used to be a peat bog island (Salici cinereae-Sphagnatum recurvi) in the middle with valuable species (STOLLMAYER-BONCZ 1982). In winter 1986-87 the whole lake was covered by ice, so it was possible cut back the trees surrounding the lake to protect the high voltage transmission line above the lake. The vegetation of the lake was burned during next February and March. Because of the large amount of woody debris, the fire lasted longer and it was stronger than it could have been without the cut branches. It caused a considerable nutrient load (STOLLMAYER-BONCZ 1993a) and destroyed the most valuable part {Sphagnum bog) of the lake. All these and the extremely dry years afterwards have caused crucial changes in vegetation composition. Open water surface, and consequently floating communities have disappeared. A succession towards reed swamp has started. Table 2. Proportion of nature conservation ranks among the 274 vascular species (Flora) and their weighed importance in two communities (Drying fen, Sedge tuft) Nature conservation rank Flora Importance in Drying fen Sedge tuft Unique 0.4 0.0 0.0 Strictly protected 0.4 0.0 32.5 Protected 2.9 2,4 0.0 Dominant K.N 9.2 24.0 Common 33.6 75.9 40.6 Natural pioneer 1.5 0.0 0.0 Natural disturbance tolerator 25.2 11.5 1.7 Weed 25.5 0.0 1.2 Cultivated 0.7 0.0 0.0 Adventive l.l 0.9 0.0