Impacts Of Human-induced Vegetation Restoration On Plant Species Diversity Of Sandy-Land In Qinghai-Tibet Plateau

Desertification and loss of biodiversity occurring in arid or semi-arid regions recently are more and more serious, and have been a greater and greater menace to society's sustainable development. Therefore, human-induced vegetation restoration has become a far more important measure to combat desertification, to restore vegetations and to protect and utilize plant diversity in regions with severe desertification. In order to fulfill these tasks successfully in sandy-land of Qinghai-Tibet Plateau, from August to September 2002, some investigations and researches were made in some sandy-land of Shazuyu and Huangshatou, which is located in the Gonghe Basin, Qinghai Province. From this study, such important conclusions are drawn as the following:a. Strong and fluent activity of wind and sand is the key factor for plant species to settle in sandy-land. If mechanical and biological sand barriers are established in such land, sand can be prevented from drifting effectively, so that with the stabilizing of sand much more plant species can settle down easily, and the plant species richness can increase dramatically.b. Enclosing sandy-land merely without sand barriers can't lead to effective restoration of its vegetation. And in such sandy-land, the dominant plant species is still Agriophyllum arenarium, and the coverage and the species richness are rather low.c. Compared with straw-barriers or wooden barriers, clay-barriers may well be in favor of the settlement of plant species at first, in the long run, however, they will hold back the development of Leymus secalimus population, so that it will take much longer time for the plant community to restore to its climax stage.d. After mechanical and biological sand barriers are established in sandy-land, it occurs first that the plant species richness and the plant species evenness will increase temporarily. Then, with the maximal development of manual sand-fixing vegetation, its natural plant species richness will decrease obviously. Gradually, with the more and more transpiration of thevegetation, and with the reduction of the deep soil moisture, in the end, a kind of balance of soil moisture will appeared and be kept for ever between the precipitation and the transpiration of vegetation, and the manual sand-fixing vegetation will be transformed consequently into its natural climax stage completely, in which the dominant plant is Leymus secalimus, and in which the plant species richness is not too low, but the plant species evenness is the lowest.e. Due to favorable condition of soil moisture, weak activity of wind and sand, and low inter-specific competition intensity resulting from repeated alternation between sand dunes and inter-dunes, the plant species richness and the plant species evenness are quite high in inter-dunes.f. Moderate and rotational grazing can do some good to the development of Leymus secalimus population, and can't result in desertification in grassland.