Abstract: During May 2004 to July 2006,we investigated the effect of the yak grazing intensity on the species diversity of Dasiphora fruticosa(L.) Rydb.shrub grassland and the vegetation characteristics in summer and winter pastures in Yongfengtan,Tianzhu Tibetan,Gansu Province.The results showed that the biodiversities decreased gradually with the increased grazing intensities in summer pasture;significant differences existed between the light grazing(P<0.05) and medium grazing and there was no significant difference between the medium grazing and heavy grazing;significant differences were observed between the control and medium or heavy grazing(P<0.05),while no significant difference was between the control and light grazing;the tendency of the changes in abundance,evenness,and species diversity indices were consist with the indices of biodiversity.In winter pasture,the biodiversities decreased gradually along with the increased grazing intensities;no significant difference were between the control and light,medium,or heavy grazing,it might be resulted from that the winter grazing was conducted in the plant dormancy period,which had a little effect on vegetation;the changing tendency of the abundance,evenness,and species diversity indices were consist with the indices of biodiversity.

Key words: Yak, Grazing intensity, Biodiversity, Dasiphora fruticosa(L.) Rydb.shrub grassland

摘要： 2004年5月至2006年7月,在甘肃天祝永丰滩高寒草甸对夏、冬季牧场牦牛放牧强度作了对比试验,研究放牧强度对草地的影响。结果表明:夏季牧场随着放牧强度的增加,生物多样性指数逐渐降低,轻度放牧和中度放牧区差异显著(P<0.05),中牧和重牧区差异不显著,重牧、中牧区均与对照区差异显著(P<0.05),而对照与轻牧区差异不显著;丰富度指数、均匀度指数和物种数的变化趋势与生物多样性指数相一致;冬季牧场随着放牧强度的增加,生物多样性指数逐渐降低,轻牧、中牧和重牧区与对照间差异不显著,主要是由于冬季放牧在休眠期进行,放牧对植被影响较小,物种丰富度指数、均匀度指数和物种数的变化趋势与生物多样性指数相一致。

关键词: 牦牛, 放牧强度, 生物多样性, 金露梅灌丛草地