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 !,β,and γ 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 !,β,and γ diversities,with more rare species and endemic species,while Kochia sieversiana community had lower !,β,and γ diversities,with few rare species and no endemic species.The γ diversity showed significant positive correlation with ! diversity,but no correlation with β diversity.There was a significant power function correlation between the α diversity and the area of single patch of the six communities,but no correlation between the β diversity(Bray-Curtis similarity index,S jk) and the area of single patch of the communities except for L.chinensis + K.integrifolia.Both the α and γ diversity showed significant correlations with the mean patch area and total patch area,but the β 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 β diversity for shaping species diversity pattern was related to the degree of habitat fragmentation.