中文摘要：

垂穗披碱草（Elymus nutans）/星星草（Puccinellia tenuflora）混播草地三个放牧季的牦牛放牧试验结果表明：①经过连续三个放牧季的放牧,放牧强度与物种丰富度、多样性指数H′、多样性指数D（除了2003年）和均匀度指数J′（除了2004年）均呈显著或极显著的二次回归;②随放牧强度的增加,各处理组地上生物量呈降低趋势,且草生长季节地上平均生物量与放牧强度之间呈极显著的线性回归关系,0~30 cm的地下生物量（包括活根和死根）与放牧强度之间呈二次回归关系;③牧草生长季牦牛最佳放牧强度为7.23头/hm2。

英文摘要：

The results of yak grazing trial on Elymus nutans/Puccinellia tenuflora mixed-sown grassland through three grazing seasons showed： ①through continual grazing for three grazing seasons,there lied in significant or extremely significant quadratic regression relationship between grazing intensity and Richness（S）,Diversity（H′）,Diversity（D）（except for 2003） and J′（except for 2004）,respectively.② with the increase of grazing intensity,aboveground biomass for every grazing plot had a reduced trend,and there was a extremely significant linear regression relationship between average aboveground biomass in forage growing season and grazing intensity,but a quadratic regression relationship between belowground biomass during 0~30cm and razing intensity.③ optimal grazing intensity was 7.23yak/hm2 in forage growing season.