Abstract: The impacts of grassland fencing on rangeland plant communities during the plant-growing season were studied in the Ketu area, Haiyan County, Qinghai Province, China in 2001. The Ketu area is one of the main distribution ranges of a rare and critically endangered gazelle, the Przewalski gazelle ( Procapra przewalskii ). Grassland fences were built for the purpose of vegetation restoration in the desert in 1999. Domestic animals at high density grazed outside the fenced range, while the Przewalski's gazelle at low density grazed inside the fenced ranges. Above ground biomass, plant height, plant cover, and plant species diversity of the plant communities outside and inside the fenced ranges were randomly sampled and analyzed in the laboratory to determine the impact of different grazing rates outside and inside fenced ranges. (1) The above-ground biomass outside the fences in June was significantly lower than that inside the fences (p <0.05), however, the above ground biomass outside the fences in both July and August were significantly higher than those inside the fences ( p <0.05). (2) The range of plant heights outside the fences (mean: 11.2～37.0 cm) was broader than that inside the fences (mean: 20.6 ～28.0 cm). Plant height outside the fences in June was significantly lower than that inside the fences ( df= 39, p <0.05). There was no significant difference between plant heights outside and inside the fences ( df =39, p >0.05). (3) The plant coverage during both June and July were significantly lower outside the fences than inside the fences (June: df = 19, p<0.05; July: df = 19, p < 0.05), but during August plant coverage outside the fences was similar to that inside the fences ( df =19,p > 0.05). (4) The animal edible herbage outside the fences was significantly lower than that inside the fences ( df = 6, p<0.05). The percentage of Chinese Stellera among total plants outside the fences was significantly higher than that inside the fences ( df =6, p<0.05). (5) The biodiversity index of the plant community outside the fences was significantly higher than that inside the fences ( df=6, p <0.05). Based on the above results, we discuss the impacts of fencing on the range community and test the hypothesis that grazing affects the productivity of the plant community. We suggest solutions for range, endangered species and integrated biodiversity management.

Key words: northwestern China, biodiversity conservation, ecological crisis, studying ways