中文摘要：

采用样方法对祁连山大通河源区高寒植被生态系统进行了调查，计算了丰富度指数、多样性指数和均匀度指数等表征物种多样性的定量指标。根据已有的等效高程模型得到植被采样点的冻土地温，并基于冻土地温时空转换模式得到一个温度从低到高的温度梯度带，通过分析高寒植被物种多样性随冻土地温梯度的变化探讨了多年冻土环境变化对高寒植被的影响。结果表明：随着冻土地温的升高，物种丰富度、物种多样性、均匀度呈上升一降低一上升趋势，并在季节冻土区内达到最大值；植被类型由高山稀疏植被向高寒草甸演替，高寒草甸向高寒沼泽草甸演替，最终向高寒草甸演替。相同植被类型在不同地温带具有不同的物种多样性分布特征，高山稀疏植被和高寒灌丛随着地温的升高呈现先增加后降低的变化趋势；高寒沼泽草甸植物群落多样性指数、丰富度指数、均匀度具有先降低后上升的变化趋势；高寒草甸的3个多样性指数随地温的升高呈上升趋势；而且在较高冻土地温环境下，高寒草甸的3个多样性指数高于高寒沼泽草甸。

英文摘要：

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 equivalentelevation 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.