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Nagy, János, Figeczky, Gábor, Penksza, Károly, Fintha, István, Molnár, Attila, Tóth, Zoltán; Kalapos, Tibor: Contributions to the flora and vegetation of the Lake Bence-tó, NE Hungary

Spirodela polyrhiza, Utricularia vulgaris, Stratiotes aloides), which disappeared from the area as the duration of open water cover shortened markedly. Thus these species can be considered extinct from the lake Bence-tó. In 1995 60% of the open water surface of the lake was covered by Lemna minor, 30% by Spirodela polyrhiza and 10% by Hydrocharis morsus-ranae. Stratiotes aloides, Utricularia vulgaris (FlNTHA 1994) and Salvinia natans, recorded first in 1992-93, also occurred yet. Concerning fern species, Thelypteris palustris, which was recorded in large quantity in 1990 and was observed in 1992-93 as well, and Gymnocarpium dryopteris encountered only in the Salici cinereae-Sphagnetum recurvi association (Soó 1954) in 1990 with few specimens, were not found in 1995. Sphagnum magellanicum, a characteristic species of the Oxycocco-Sphagnetea association and occurring in a large population in 1990, has also disappeared from the area. Apart from these, Salix pentandra, Carex acutiformis, C pendula (in 1990 a few hundreds recorded), Glyceria fluitans, Pastinaca sativa, Bilderdykia convolvulus, Polygonum persicaria, Rorippa amphibia and Salix pentandra were not found in 1994-95 either. Twelve species found in the lake are protected. Four of these (Salix pentandra, Salvinia natans, Sphagnum magellanicum, Thelypteris palustris) probably became extinct from the area, while the survival of 1 species is uncertain. Out of the above 4 species Salvinia natans can also be found in the IUCN list and is protected by the convention of Bern as well. Eight protected species still occur in the area: Carex pseudocyperus, Chrysanthemum serotinum, Cicuta virosa, Dryopteris carthusiana, Iris pseudacorus, Sphagnum fimbriatum, Sphagnum squarrosum, Urtica kioviensis. In the Hungarian Red Data Book (RAKONCZAY 1990) Cicuta virosa is listed as currently endangered, Chrysanthemum serotinum as potentially endangered species. Vegetation Salici cinereae-Sphagnetum recurvi Soó 1954 This association covers the largest area extending along the lake bed. Its shrub layer consists almost exclusively of Salix cinerea, other shrub species (Rosa canina, Rubus caesius and Frangula alnus) occur only along the border of the association. Its herb layer is species poor with low cover values. Lycopus europaeus and Solanum dulcamara, creeping in the sunny clearings, occur in the highest amount. Out of ferns Athyrium filix-femina is present at a few places, Thelypteris palustris have not been found since 1993. The moss layer is dominated by peat mosses, but their cover decreased by 1/3 between the August of 1994 and 1995. The ratio of Sphagnum fimbriatum and Sphagnum recurvum is approximately 7:3. The shortage of water is also indicated by the change in the peat moss species: while Sphagnum magellanicum occurred abundantly in 1990,