[Contribution of syntaxonomy to the study of vegetation dynamics].

Of late decades, numerous studies on vegetation dynamics have been carried out and the spectrum of studied objects extended. However, syntaxonomy, while is capable to reveal patterns in vegetation changes, is virtually not used in analysis of succession. Prospects of syntaxonomy application to the study of vegetation dynamics are demonstrated by the example of succession analyses of pasture digression, vegetation changes under influence of recreation, progressive succession at the place of deserted settlements. The special role played by the analysis of syntaxonomic spectre of serial plant communities is discussed. The analysis makes it possible to estimate the serial status of communities by the ratio in their floral composition of species from cenofloras of classes that represent different serial stages of vegetation.

[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.