Changes in Vegetation and Earthworm Populations under Free Grazing European Bison (Bison bonasus) in Broad-Leaved Forests of the Kaluzhskie Zaseki State Nature Reserve

This paper studies the impact of a free-ranging bison population on the vegetation and soil fauna in spatially adjacent biotopes (meadow-transition zone-surrounding forest) in the Kaluzhskie Zaseki State Nature Reserve. It is noted that bison maintains meadows in the absence of haymaking. Analysis of phytosociological relevés shows that the forest vegetation has been significantly transformed by bison over 10–15 years, as evident from (1) differences in the ecological-coenotic structure of the vegetation in the different biotopes, (2) a larger ecological-coenotic diversity of communities in the transition zones in comparison with surrounding forests, and (3) an increase in the participation of nitrophilous species in the vegetation. A fairly high earthworm species diversity (a total of seven species in the biotopes) is found; Aporrectodea caliginosa dominates in the earthworm density and biomass. The total earthworm density and biomass became lower in the transition zone than in neighboring forests and meadows, and the differences in earthworm density between the transition zone and the meadows were statistically significant.