Main Trends in the Vertebrate Animal Population Dynamics in a Clayey Semidesert of the Trans-Volga Region Since the Mid-18th Century

Animal a The paper considers the main natural changes associated with climatic fluctuations and economic activity in a clayey semidesert of the Volga-Ural interfluve over the past 250 years. The authors distinguish four climatic periods determined by the humideness of the territory, namely: the mid-18 th century – 1820s; 1830s – 1950s; 1960s – the end-1980s; and 1990s – 2010s. For each period, features of the area are described, related to humidification and human economic activity, and, as a result, changes in flora and fauna characteristics of the region. In the clayey semi-desert in the Trans-Volga region, only the existence and character of aquatic and near-water communities is shown to directly de-pend on climatogenic factors. Most changes in the animal world of other community types reflect various stages and forms of the economic use of the territory and are only corrected by climatic changes. The ravine forests in lake depressions existed until the 19 th century ensured the presence of a complex of ravine-forest species in the regional fauna. After the deforestation of these communities, some part of the species of this complex completely disappeared from the region, some part became synanthropes, and the other one firstly disappeared but later returned to the region, after the appearance of polydominant tree-bush communities in lake depressions and artificial forest belts and gardens on the plain. Because of the strong grazing during an arid climatic period, there was a change of steppe plant associations on the plain to desert ones, so that some steppe animal species also disappeared from the region with some desert ones having come to their place. The plowing of plain areas has led to the appearance of species in the region, which use plowing as their feeding sites. Various forms of human development of the territory have led to the arrival of a number of species from other regions. Acknowledgments : This work