Vegetation changes of the Molinio-Arrhenatheretea class in the Bystra valley, eastern Poland

The study objective was to analyze and assess the vegetation changes of the meadows ( Mo­linio-Arrhenatheretea class) located in the valley of the Bystra River in eastern Poland after a period of 38 years, and to identify the direction of plant communities succession. The studies were conducted in the years 1973 and 2011 on grasslands belonging to farmers. The floristic diversity was identified based on the phytosociological structure and mean number of species calculated based on the number of species in the particular releves of the phytocenosis under study. The highest frequency of occurrence was demonstrated by the Poa pratensis - Festuca rubra community within which more than half of the patches persisted over the 38-year period. New communities ( Scirpetum sylvatici , Alopecuretum pratensis , Lythro-Filipenduletum ) appeared after the withdrawal of habitats of the Phragmitetea class, due to the lowering of the groundwater level. A portion of the meadows and pastures were transformed into arable fields, gardens or building plots. Among ecological indicators, the greatest differences were observed in the mean soil moisture values between the two years compared, both for all meadows and the predominant community, which indicates an increase in habitat humidity.