Degree of Dominance and Species Richness in Plant Communities with High and Low Intensity of Interspecies Competition

Abstract

The role of interspecies competition in the structuring of plant communities remains unclear. The purpose of our study was to test the assumption that the relationship between the degree of numerical dominance (DD) and local species richness may differ in plant communities with high and low interspecies competition intensity. The stands and open communities of the river shoals of the Western Caucasus were used as the object of research. The former were regarded as communities with a high intensity of interspecies competition, the latter were seen as communities structured mainly by the processes of species settlement. The results showed that the average DD values ​​are similar in the areas of these communities having an equal amplitude of variation in the number of individuals (shoots) and the size of the actual (cenotic) species pool. In the stands and communities of shallows there is a negative correlation between DD and species richness, which in both cases is a consequence of a reduction in dominants of the amount of resources and/or space available for other species. At the same time, we did not find any signs of other mechanisms that would be specific for stands or communities of shallows. However, the characteristics of communities with high and low intensity of interspecies competition can be manifested more strongly if we compare the ratio between DD and species richness in relatively large areas.