Comparative analysis of flora of the Middle Volga region

The authors took 32 local floras (LF) to study the floristic g-diversity of the Middle Volga region. Their species composition was studied on an area not exceeding 400 km², which is the optimal value for this area. For such an area, the number of vascular plant species was 679 species (the maximum value is 835, the minimum is 586). This sample size is sufficient to illustrate the main taxonomic parameters. The considered local floras are geographically located within 3 zones and five subzones according to zones and types of vegetation zonation in Russia and are located within the territories of the Republics of Tatarstan, Mordovia, Chuvashia, as well as Samara, Ulyanovsk, and Penza regions. Based on the family and genera spectra, we identified groups of similar LFs using the k-means method in the R package. When analyzing the spectrum of families, the determining feature for this territory is the third place in the spectrum, which is occupied by the families Fabaceae or Rosaceae . All 32 LFs considered ranged from the Fabaceae type in the southeast to the Rosaceae type in the northerly direction. We have identified the following boundaries of qualitative changes in the floristic composition at the level of large taxonomic groups (genera and families): 1) extreme types of flora, in which the characteristics of "forest" and "steppe" are most pronounced: Rosaceae -type, characterized by a large number of species from the genus Alchemilla , as well as Potentilla and Fabaceae type, which is determined mainly by the numerical combination of the genera Astragalus and Vicia ; 2) transitional types of floras arise due to a decrease in the number of representatives of these genera. The reason for this may be anthropogenic impact, primarily deforestation; 3) the greatest differences in the composition of large taxonomic groups are observed in the southernmost local flora of the Trans-Volga region (south of Samara region).

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