Study on niche characteristics of the plant community in the alpine grassland of Big Youerdusi under a degeneration gradient

The Levins niche breadth index (BLi) and Pianka niche overlap index (Qik) were used to study the niche breadth and the niche overlap of 17 main kinds of plants within different degradation gradient in an alpine grassland of Big Youerdusi. Results showed that the niche breadth of dominant species Stipa purpurea was higher than others in the non-degraded stage, it was decline in the light degradation and moderate degradation stages, and then it increased in the heavy degradation stages. The change of niche breadth of other species changed based on the community structure. There was a phenomenon that plant species with narrow niche breadth had high niche overlap in different degeneration stages; the reason for this change of niche overlap was the interactive effects of different species’ ecological characteristics and grassland degradation on interspecific relationships. In conclusion, overgrazing has led to grassland degradation, and the plant species niche overlap is relatively low, in the alpine grassland of Big Youerdusi.