Territory heterogeneity study on the «types-areas» curve for a research of its floristic structure (on the example of the Soksky physiographic area)

Abstract

The Sok district is an elevated-flat forest-steppe region located in the northwestern part of Samara Region. A sufficiently large area of its territory can provide a variety of natural conditions, as a result of which there may be differences in the species composition of the flora of its parts. After the accumulation of data on the distribution of species across the territory, it is possible to study the change in species composition in different directions using the curve number of species-area. Zones of the most mass inflow of species can be considered as a different floristic region, having a different species composition. Taking into account the geographical configuration of the Sok district, the study was carried out in two directions: latitudinal (from north to south and from south to north), and also along the direction of the river bed (from the sources of the Sok River to the mouth and from the mouth to the sources). When studying the curve number of species-area in all cases, in addition to primary accumulation, there was an increase in the number of species in the middle region, and also at the end of the ascent. Accordingly, the identified heterogeneity of the species composition of the flora of the Sok district is divided into four zones. They were proposed to be considered as reference units for studying the floristic structure of the territory that is, determining the possible number of complete floras. When increasing the list with an increase in area, in addition to increasing the number of species, the position and proportion of some of the leading families were monitored. The constancy of families location should be noted: they do not change places and retain a sequence of locations. Only a share of the family in the series of floristic sampling is changing. The Sok physical-geographical district is a typical territory for the Fabaceae-zone. On its territory there is no change in the types of floras. We estimated the species specificity of the Sok physical-geographical district in relation to the Melekess-Stavropol region bordering it, located in the forest-steppe province of the Lowland Transvolga. The reference units of the flora of the two regions differ within different floras.