IMPACT OF WATER LEVEL FLUCTUATIONS ON THE TALAB ISLANDS FLORA STRUCTURE IN PSKOVSKO-CHUDSKOE LAKE
Water level fluctuations, the absolute amplitude of which is 3 m in Pskovsko-Chudskoe Lake, lead to the annual change in the coastline and to the appearance of extensive beaches in dry years. Overgrowing of exposed sand spits and beaches on the Talab islands in dry 2006-2007 years has led to an increase in flora species affluence and to changes in the ratio of eco-cenotic groups. Taxonomic list of vascular plants was increased by 24 species and 2 families. There were discoveries of new flora species in Pskovsko-Chudskoe Lake, among which was Pycreus flavescens, included to the Red Book of the Pskov Region. In cenotic groups except weeds coastal species were separated out. The number of adventive species increased, intensive resettlement of environmentally aggressive Hera-cleum sosnowskyi has occurred. The appearance on the beaches of Phragmites australis continuous thickets stopped the process of islands erosion and led to steep slopes overgrowing.