Changes of species diversity indices along the ground temperature of permafrost in the source region of Datong River in the Qilian Mountains, northwestern China.

The study analyzed the changes of species diversity indices (richness index, ShannonWiener diversity index and Pielou evenness index) along the ground temperature of permafrost based on investigation data from 199 vegetation spots sampled and permafrost temperatures from an equivalentelevation model in the Datong River source region, northeastern QinghaiTibet Plateau in China. The results showed that with the increase of permafrost temperature, the species diversity indices firstly ascended, then decreased and finally ascended, meanwhile the maximum reached in the seasonal frozen zone. Warmed permafrost caused shift in plant succession in different temperature zones, i.e. the succession from alpine sparse vegetation to alpine meadow, and then from alpine meadow to alpine swamp meadow and finally from alpine swamp meadow to alpine meadow. Same vegetation community had different characteristics along the temperature gradient. Alpine sparse vegetation and alpine shrub firstly ascended and then decreased, whereas the values of alpine swamp meadow had an opposite trend. Alpine meadow had an ascend trend with the increase of permafrost temperature, and the biodiversity indices of alpine swamp meadow were lower than that of alpine meadow in the warmer zones compared with the values of the two vegetation types.