Abstract:

Sand control and human-induced vegetation restoration is very important to improve local environments and achieve sustainable development in Qinghai_Tibet Plateau. Since 1958, a series of experiments to combat desertification have been conducted in Shazhuyu of Gonghe Basin, Qinghai Province. In this study, several indices of plant species diversity, increased rapidly after establishing sand barriers. At the earlier phase of artificial sand fixation vegetation, all these indices reached a maximum, and then decreased because of the overwhelming dominance of Leymus secliumus population in late succession. It indicated that on shifting sand dunes of Qinghai-Tibet Plateau, persistent erosion and sand drifting caused by strong winds are probably the limiting factor or bottleneck for plant species to survive shifting sand dunes. When mechanical and biological sand barriers are established, wind erosion and sand drifting can be weakened dramatically, which created relatively favorable conditions for native plant species to survive there and then accelerated the vegetation restoration. Total cover and cover of Leymus secliumus which is dominant in best-restored vegetaion are the most sound indices to evaluate degree of vegetation restoration, instead of plant species diversity which rose at the beginning of restoration but decreased reversely after a short time and dropped to bottom in best-restored vegetation. According to intermediate disturbance hypothesis, we argue that the low species diversity maybe results from the overwhelming dominance of Leymus secalimus that can exclude some other plant species.

Key words: Alpine sandy land, Sand barriers, Artificial sand fixation vegetation, Human_induced vegetation restoration, Species diversity