干旱区生态环境知识资源中心

The desert steppe exclosure system was constructed in 2003 to implement the Chinese policy that banned livestock grazing to permit recovery of overgrazed rangeland. Empirical data on the effectiveness of excluding livestock grazing on restoring degraded desert soils and vegetation in western China is limited. Additional data are necessary for making alternative grassland management decisions and implementing effective subsidy policy. In this paper, desert vegetation in an extremely dry area, which was fenced to exclude winter sheep grazing in 2003, was compared to adjacent sites where winter grazing has been continued. Vegetation was sampled to determine plant species richness, vegetation composition and herb-shrub layer cover. Soil properties were also measured. Results showed that excluding sheep grazing from desert steppe for 8years increased plant cover and approximately tripled the biomass of standing vegetation, especially the shrub component. Livestock exclusion was more favorable for the growth of perennial grasses. Annual forbs were more abundant in the grazed area than in the ungrazed area. Species richness, evenness and diversity as measured by Simpson or Shannon-Wiener indices did not differ between the grazed and ungrazed areas (0.05), which indicated that species composition of the desert vegetation is difficult to restore. Excluding livestock grazing increased soil organic carbon in the 0-10cm (by 66%) and 10-20cm (26%) soil depths, total nitrogen in the 0-10cm (110%) and 10-20cm (60%) soil depths and total phosphorus in the 0-10cm (114%) and 10-20cm (64%) soil depths (P<0.05). Our results demonstrated that vegetation biomass and soil properties can be improved by removal of sheep grazing, but had less impact on the species richness and diversity in this extremely dry region. It also affirms the current central government’s policy of banning grazing to benefit the recovery of ecological services.