Transformation of begetation and Earthworm Population Under Free Grazing of Bisons Bison Bonasus in Broadleaved Forests of the "Kaluzhskie Zaseki" State Nature Reserve
We have studied an impact of a free-ranging bison population on vegetation and soil fauna in spatially conjugated biotopes as meadow, transition zone which is forest visually changed by bison and forest without traces of bison activities, in the “Kaluzhskie zaseki” State Nature Reserve. We found that bison maintains meadow species in the absence of haymaking. On the basis of analysis of phytocoenological relevés, it was shown that forest vegetation is significantly transformed by bison in the transition zone after 10-15 years of grazing. Ecological-coenotic structure of vegetation is significantly different between the biotopes. Ecological-coenotic structure of vegetation communities in the transition zones is more diverse than in the background forest and a share of nitrophylous species increases. Earthworm species diversity is rather high (7 species totally). The endogeic species Aporrectodea caliginosa dominates the total earthworm density and biomass. Earthworm density and biomass are lower in transition zone than in neighboring forests and meadows. The differences in earthworm density between transition zone and meadows are statistically significant.