白牦牛放牧强度对高寒草原植物群落物种多样性的影响

采用典型样地调查方法,对地处青藏高原东北缘的天祝地区3个典型白牦牛放牧地的夏季、冬季牧场进行植被调查,运用多样性、丰富度、均匀度、优势度指数对高寒草原植物群落进行物种多样性测度.结果表明,夏季牧场的放牧强度乌鞘岭(40.05头.d/hm2)>岱乾(14.7头.d/hm2)>南泥沟(11.25头.d/hm2),而它们的群落物种多样性指数分别是(1.44±0.321),(1.68±0.095)和(2.03±0.022).说明随着放牧强度的增加物种多样性指数逐渐降低.乌鞘岭、岱乾、南泥沟的物种丰富度指数分别是(1.29±0.05),(1.81±0.203)和(2.14±0.066);均匀度指数分别为(0.4±0.103),(0.43±0.115)和(0.55±0.034).3个夏季牧场的丰富度指数、均匀度指数和物种数的变化趋势与物种多样性指数的变化趋势相一致.冬季牧场的放牧强度南泥沟(320.55头.d/hm2)>岱乾(259.2头.d/hm2)>乌鞘岭(40.05头.d/hm2),而它们的物种多样性指数分别是(1.63±0.122),(1.74±0.052)和(1.44±0.321),即物种多样性指数,岱乾>南泥沟>乌鞘岭.南泥沟、岱乾和乌鞘岭的物种丰富度指数分别是(1.87±0.078),(1.91±0.082)和(1.28±0.05);均匀度指数分别为(0.41±0.085),(0.38±0.036)和(0.4±0.010 3).3个冬季牧场的丰富度指数的变化趋势与物种多样性指数的变化趋势相一致.随着放牧强度的增强,群落物种的多样性、丰富度、均匀度均有所降低,高寒草原植物群落结构越简单,原生优势物种逐渐被适口性较差的物种替代,优良牧草种数减少.

Effect of white yak grazing intensity on species diversity of plant communities in alpine grassland

The vegetations in summer and winter pasture of three white yak pastures of the Tianzhu County was investigated by typical sample method.And the species diversity of plant communities was detected on the basis of the indices of diversity,richness,evenness and dominance in 37 sample spots.The results showed that:in summer pasture,the grazing intensities were as following:Wushaoling(40.05(tou·d/hm~2))>Daiqian(14.7 tou·d/hm~2)>Nannigou(11.25 tou·d/hm~2),while the indices of species diversity were(1.44±0.321),(1.68±0.095)and(2.03±0.022)respectively.It indicated that species diversity index decreased with the increased grazing intensity,so did the indices of richness and evenness.In winter pasture,the grazing intensities were as followed:Nannigou(320.55 tou·d/hm~2)>Daiqian(259.2(tou·d/hm~2))>Wushaoling(40.05 tou·d/hm~2),while species diversity indices were(1.63±0.122),(1.74 ±(0.052))and(1.44±0.321)respectively.The indices of richness were(1.87±0.078),(1.91±0.082)and(1.28±0.05),and evenness(0.41±0.085),(0.38±0.036)and(0.4±0.0103).The richness indexes showed the same trend with species diversity.As a consequence,the species diversity,richness and evenness were gradually lower with the increase of grazing intensity,and plant species composition and structure tended to be simple.And overgrazing on grassland would inevitably result in converse succession.