ALIEN AND NATIVE DOMINANTS HAVE A SIMILAR EFFECT ON THE SPECIES RICHNESS OF SYNANTHROPIC PLANT COMMUNITIES OF THE WESTERN CAUCASUS

Abstract

It remains unclear whether alien dominants, on average, have a stronger effect on the species richness of plant communities than native ones. We examined this issue on the example of 20 areas of synanthropic plant communities dominated by species of different biogeographic origin (the study area is the Western Caucasus, the Belaya River valley, 190-680 m above the sea level). Within each of them, samples of aboveground biomass were taken from 25-30 plots of 0.25 m with different coverings of dominants, which were then sorted by species and weighed. Analysis of the data has shown: 1) the average species richness of samples with a similar degree of dominance of alien and native species differs mainly insignificantly; 2) the close relationship between the degree of dominance of alien species and species richness is, on average, about the same as between the degree of dominance of native species and species richness; 3) the relationship between these characteristics in most cases can be satisfactorily explained on the basis of "energy-diversity" hypothesis; 4) the share of synanthropic plant species in communities with high participation of both alien and aboriginal dominants is not higher than in communities with low participation of these dominants. On the whole, our results indicate a similar and predominantly nonselective nature of the impact of alien and native dominants on accompanying species of communities.