中文摘要：

为探讨高寒牧区牧草生长季放牧强度对多年生混播人工草地群落特征及地上现存量的影响,从2003年至2005年在垂穗披碱草（Elymus natans）/星星草（Puccinellia tenuflora）混播草地上开展了牦牛放牧控制试验。结果表明：植被盖度随放牧强度的增加而降低,放牧强度对放牧区植物群落盖度的影响极显著（P〈0.01）;放牧强度与物种丰富度S、多样性指数H′、多样性指数D（除了第1年）和均匀度指数J′（除了第2年）均呈显著或极显著的二次回归,各放牧区与对照区植物群落的相似性系数与放牧强度成显著负相关（R=-0.9205）,说明各放牧区植物群落朝着远离对照群落的方向演替;放牧强度和放牧时间对地上生物量的影响极显著（P〈0.01）,且随着放牧强度的增加,各处理组同一时期地上生物量逐渐减小。

英文摘要：

Different grazing intensities for three years were conducted from 2003 to 2005 in Elymus natans/ Puccinellia tenuflora mixed-sown pasturer to study the effect of grazing intensity on community character and aboveground present biomass of Elymus natans/Puccinellia tenuflora mixed-sown Pasture during forage growing season in alpine pasture region. Vegetation coverage decreased with the increase of grazing intensity （P〈0.01） in grazing period. Moderate grazing caused highest species richness and diversity index except for diversity index at the first year. The negative correlation was observed between similarity index and grazing intensity （R=- 0.92）, indicating that grazing resulted in succession of plant community compared with no-grazing. Grazing significantly reduced aboveground present biomass and aboveground present biomass decreased with increase of grazing intensity.