| Abstract [eng] |
Semi-natural grasslands are among the most valuable ecosystems in terms of biodiversity, but they are also highly sensitive. Their condition depends on appropriate use and management. When mowing or grazing is discontinued, competitive and expansive species may gradually establish, altering community structure and reducing species diversity and evenness. Resurvey studies are important for assessing such changes, as repeated surveys at the same sites allow vegetation dynamics to be evaluated. The aim of this master’s thesis was to assess the floristic, syntaxonomic and ecological changes in the meadow communities of the Šventoji River valley over the past decade. The objectives were to asses changes in plant species diversity in the studied meadow communities; to classify meadow communities to the alliance level syntaxa, to asses changes in the species composition and cover of meadow communities in the studied plots; to determine the correspondence of the studied communities to European Union natural habitat types and to assess their changes between the study periods; to assess the dependence of meadow community dynamics on ecological conditions during study period. A total of 159 vascular plant species were recorded. Species richness did not change significantly during the study period; however, the Shannon diversity index decreased significantly from 2.65 to 2.07. The most altered plots showed clear changes in species composition and cover, often associated with the dominance of competitive species such as Filipendula ulmaria, Calamagrostis epigejos, Anthriscus sylvestris and Elymus repens. The studied communities were assigned to syntaxonomic alliances reflecting differences in habitat conditions and species composition. EUNIS classification showed that wetter grassland communities were generally assigned to the broader grassland and tall-forb habitat type (R), whereas drier communities corresponded to the more specific dry grassland type (R1A). In some plots, changes in species composition also changed their EUNIS habitat assignment. Community distribution was significantly associated with all analysed Ellenberg indicator values, although no significant changes in these ecological conditions were detected between the study periods. Overall, the grassland communities of the Šventoji River valley remained relatively stable, but some plots showed structural changes linked to reduced species evenness and the spread of competitive species. |
