[Spatial patterns of plant species diversity in a degraded successional series of fragmented Leymus chinensis meadow in Songnen Plain of Northeast China].

Species diversity pattern is a hot topic in the forward field of international biodiversity research. Taking a degraded successional series (six communities distributed in 144 isolated patches) of fragmented Leymus chinensis meadow in Songnen Plain as test objects, this paper studied the spatial patterns of alpha, beta, and gamma diversities and related mechanisms. Eighty seven plant species were recorded, but none of them were distributed across all patches. L. chinensis + Kalimeris integrifolia community or L. chinensis community had higher alpha, beta, and gamma diversities, with more rare species and endemic species, while Kochia sieversiana community had lower alpha, beta, and gamma diversities, with few rare species and no endemic species. The gamma diversity showed significant positive correlation with a diversity, but no correlation with beta diversity. There was a significant power function correlation between the a diversity and the area of single patch of the six communities, but no correlation between the beta diversity (Bray-Curtis similarity index, Sjk ) and the area of single patch of the communities except for L. chinensis + K. integrifolia. Both the alpha angamma diversity showed significant correlations with the mean patch area and total patch area, but the p3beta diversity did not. The higher the species richness in the communities, the more the rare species and endemic species, the larger the possibility of species depopulation in local patches was. The importance of beta diversity for shaping species diversity pattern was related to the degree of habitat fragmentation.