Phytosociological Data in Assessment of Anthropogenic Changes in Vegetation of Rzeszów Reservoir

Abstract

Phytosociological research on aquatic and marsh vegetation was conducted in Rzeszów Reservoir (SE Poland): 134 relevés according to the Braun-Blanquet method were collected there in 2016 and compared to 91 relevés published in 1994 (225 relevés in total). Changes in vegetation type, diversity measures, species composition, and Ellenberg Indicator Values (EIVs) for light, moisture, reaction, and nitrogen were analysed. Over the 22 years (1994–2016), the greatest changes were noted in communities of the classes Lemnetea and Potametea and the alliance Salicion albae. The long-term observations demonstrated the disappearance of 14 phytocoenoses and the occurrence of 12 new ones. An expansion of marsh communities (Typhetum latifoliae, Typhetum angustifoliae, Glycerietum maximae, Leersietum oryzoidis) was noted, causing a decline of several species and vegetation types. According to canonical correspondence analysis (CCA), four environmental variables (light, moisture, nitrogen, and pH) were related to plant distribution. The strong disturbances reflected in intensive eutrophication were due to human activity, which is the main factor shaping the ecological succession and overgrowing of the reservoir.