[Contribution of the Brown-Blanquet method to the explanation of species richness of the plant communities].

A possibility of estimation of factors of formation of species richness of the plant communities by H-function as a measures of complexity of the phyto-sociological spectrum of communities is proved. The phyto-sociological spectrum reflects contribution of those various syntaxa to the coenofloras that indicate ecotope character and the successional status of communities. Analysis of a wide set of grassy vegetation of the South Ural region (from synanthropic to natural) revealed a linear positive correlation between H-function values and species richness. Primary factors of formation of species richness of the vegetation investigated are general favorability of the environment, variability of the moistening regime and successional status reflecting processes of vegetation transformation under influence of internal (regenerative succession) and external (cattle pasture) causes.