ОСОБЕННОСТИ ИЗМЕНЕНИЯ РАСТИТЕЛЬНОГО ПОКРОВА ПСКОВСКОГО ОЗЕРА В УСЛОВИЯХ ДИНАМИКИ УРОВЕННОГО РЕЖИМА

Abstract

The results of the analysis of literature data since 1949 and original long-term (2007–2019) studies of the higher aquatic vegetation of Lake Pskov are presented. Pskov Lake is a shallow water body with heightened trophic level and annual fluctuations of water level. Currently, the flora of the Lake includes 117 species. Since first studies, certain changes have occurred in the flora composition of the lake. We have not found 10 species, 3 of which were included in the Red Book of the Pskov region Data. 16 new species have appeared, among which 4 are listed in the Red Book of the Pskov Region and 2 in the Red Book of Estonia. 64 associations in the composition of vegetation were noted. The main cenose-formers are Phragmites australis (Cav.) Trin. et Steud., Potamogeton perfoliatus L., Schoenoplectus lacustris (L.) Palla., which play leading role in the Lake overgrowth in all years of research. The decrease in the water level in Pskov Lake leads to an increase of associations and number of species in them. With an increase in the water level in the lake, the aboveground biomass of the southern reed, the main edificator among helophytes, decreases. Communities of helophytes play the main role in the overgrowth of the shores of Pskov Lake. According to the analysis of Landsat satellite images (1988–2017), the average value of the lake area occupied by helophytes was 4.14%. According to our data for the period from 2007 to 2019, the proportion of hydrophytes amounted to ~6.3% of the water area. The total overgrowth of Lake Pskov has clearly increased: in 1966–1970, the overgrowth area was 5% of the water area, in 1988–1989 – 7.9%, in 2005 – about 12%. Currently (2007–2019), macrophytes occupy ~10.4% of the lake area.