Plant population niche characteristics research of desert Seriphidium transiliense degradation grassland

With the methods of space series substituting time series and of contrastive analysis, the niches of different degeneration gradients on desert Seriphidium transiliense degradation grassland were studied. The importance value, Levins niche breadth, Pianka niche overlapping indexes and niche similarity ratio were analyzed. With different degeneration gradients, the ecological niche was different in different populations. The niche width of constructive species of S.transiliense and the dominant species Petrosimonia sibirica decreased and that of the majority of remaining population was gradually increasing during the progress of the retrogressive succession. In different degradation stages, the niche breadth of P.sibirica is greater than the other species and there is large niche overlap between P.sibirica species and Trigonella arcuata species; Tulipa iliensis and T.arcuata have high niche similarity. During the progress of the retrogressive succession, the similarity ratio of P.sibirica and T.arcuata have higher niche breadth increased at the early stage and then reduce afterwards.