Abstract:

As a typical fragile ecosystem in the northwest arid regions in China， the species diversity and stability of the vegetation community are critical to ensuring ecological security and sustaining regional sustainable development. In this study， the distance from river bank was divided into three gradients， including 0.3 km （T_0-0.3）， 0.3 to 1.7 km （T_0.3-1.7） and 1.7 to 4.0 km （T_1.7-4.0） by the method of K-Means clustering with the data of soil moisture in the tail area of the lower Heihe River ， to investigate the vegetation types， species diversity and vegetation stability and satisfy the suitable soil water for plants. The results showed that： （1） vegetation are dominated by plants with the characteristics of resistance to wet saline， trees mingling with shrubs and herbs， and drought-tolerant shrubs and sub-shrubs within the 0-0.3 km， 0.3-1.7 km， 1.7-4.0 km distance from river bank. （2） The Simpson index， Pielou index， Shannon-wiener index and richness index are the largest and least within the 0.3-1.7 km and 1.7-4.0 km distance from river bank， respectively， the vegetation community stability and diversity index are opposite. （3） The suitable soil water for plants are 27%-31%， 15%-22% and 4%-7% within the 0-0.3 km， 0.3-1.7 km， 1.7-4.0 km distance from river bank， respectively. This study deepen our knowledge of sustaining the species diversity and community stability in the river-tail area in arid regions.

Key words: tail area of Heihe River, diversity, stability, optimum for soil moisture