Floristry and plant biogeography of the Eastern part of the Volga Upland

Abstract

Analysis of taxonomic indicators traditionally leads the overall analysis of flora. In this case, first of all, it is necessary to consider the range of families. The triad of leading families deserves special attention, according to the third member of which it is customary to distinguish the type of flora. The type of flora characterizes the corresponding territory within which a floristic “zone” is distinguished. According to the published data on the floras of the administrative units of the Volga basin, we have previously outlined the boundaries within the territory of the Middle and partly the Lower Volga region, on which the Fabaceae-type of flora is revealed. At the same time, the Upper Volga region is represented by Rosaceae-type floras. However, these selected administrative units are too large to outline more specific boundaries.In this article, we propose a similar analysis based on the data of the floras of physical-geographical regions with an area of 2.3–9.7 thousand km2. For the analysis, we selected six areas belonging to the forest-steppe province of the Volga Upland, which is part of the Middle Volga region. We found that the border of the floristic zones (Fabaceae and Rosaceae) runs along the considered area of the Volga Upland. With respect to physical-geographical regions the border runs on one side between Korsun-Sengileevsky and Sredne-Sviyazhsky areas, on the other, between Zasursky and Tsivil-Kubninsky areas. Within the studied territory, the border is determined by the occurrence of representatives of the genera Alchemilla and Potentilla (for Rosaceae), as well as Vicia and Astragalus (for Fabaceae) The prevalence in the number of the common lady’s mantles is more noticeable to the northwest. The genera Carex, Galium, Viola, Potentilla, Artemisia, Salix, Vicia, and Veronica are leading in the frequency of occurrence in the head part of the spectra of floras in the territory under consideration.