XVI International Botanical Congess

Since 1967 the Department of Geobotany of the St-Petersburg University has been realizing the works of biomonitoring of steppe vegetation. We established that the reserve vegetation is subjected to mesophytization. Since the description of the vegetation made in 1968 we have noticed some changes on the territories protected in the conditions of mowing rotation. Dominated at that time turf cereals (Stipa pennata,, S.tirsa, Festuca valesiaca) have changed to more mesophyting rhizome cereals. In 1979, Bromopsis riparius, B.inermis prevailed, and in 1993 Bromopsis reparius, B.inermis, Arrhenatherum elatius, Calamagrostis epigeos began to dominate. The amount of xerophyts in motleygrass reduced from 70% to 50%. And on the territory, which in 1979 was transferred in the condition of absolute reservation the amount of xerophyts was nearly 35%. The main dominating species are Calamagrostis epigeos, Bromopsis inermis. They are typical of meadow community. The main reasons of successions of the vegetation are anthropogenic influence and climatic changes (established by us using 50 years data of observation).