Vegetation transformation as a limiting factor in the existence of rodent populations in open area (using the example of Spermophilus suslicus)

A comparative analysis of the composition and structure of plant communities in two places of the former habitat of Spermophilus suslicus in the Nikolaevsky district of the Ulyanovsk region is provided. Our analysis of the current state of S. suslicus populations in the Volga region has shown that over the past fifty years there has been a critical decline in the numbers of the species, and even its complete disappearance has been noted in some regions. A number of researchers note that dynamic changes in vegetation have certain influence on these processes. Therefore, the goal of our work was a comparative study of the vegetation of biotopes at the time of high numbers of animals against the background of intensive grazing and in the absence of gopher settlements for more than 15–20 years in the absence of grazing. Our studies have shown an increase in the species richness and structural diversity of communities due to the introduction of species from the upland, nemoral and boreal ecological-coenotic groups into their composition. Phytocenoses of steppe meadows with a high participation of Festuca valesiaca, Poa pratensis, Helictotrichon pubescens, and Elytrigia repens after the cessation of grazing are replaced by cenoses of meadow steppes with the dominance of Bromopsis riparia, Poa angustifolia , and Calamagrostis epigeios . There is an increase in the total projective cover of the grass stand (from 40 up to 60– 70%). Forage species that are background ones when the number of animals is high sharply reduce their participation in the grass stand. Changes in the ecological conditions of biotopes are characteristic, namely: modern communities are formed in drier, less nitrogen-rich and “acidic” habitats. The preservation and possible restoration of spotted ground squirrel settlements in the Volga region is possible subject to scientifically based anthropogenic impact, implemented in the form of haymaking and grazing.