中文摘要：

全球变化背景下,冻土环境变化对地上植被的影响是近年来倍受关注的重大科学问题。鉴于此,在长江源区冬克玛底流域分析了植物物种多样性和生物量空间分布规律及其对冻土活动层埋深变化的响应。结果表明,1）地上植被的物种多样性指数随着冻土活动层埋深的增加表现出非单调性递减;在冻土活动层埋深约2m时,物种多样性指数较高（Patrick指数、Shannon-Wiener指数和Simpson指数分别为：26.43±3.31,2.06±0.38和0.83±0.08）。2）生物量的垂直分布规律整体表现出地下生物量明显高于地上生物量,地下生物量占总生物量的63%～96%。3）地上生物量和地下生物量与活动层埋深均具有显著的相关性（R2=0.65,P〈0.01;R2=0.79,P〈0.01）,随着活动层埋深的增加呈现出明显下降趋势。4）活动层埋深对0～40cm深度的地下生物量的垂直分布具有显著影响。活动层埋深约1m时,地下生物量垂直变化很小;活动层埋深大于1.5m时,呈倒金字塔形分布;活动层埋深大于3m时,10～40cm深度的地下生物量占总地下生物量的比例随着活动层埋深（3.11～4.81m）的增加而增加。

英文摘要：

With a background of global climate warming,the effects of permafrost changes on aboveground vegetation have attracted much attention.The effects of permafrost changes on distribution patterns of plant species diversities and biomass in the Dongkemadi River Basin（head water of Yangtze River） were investigated.1） Species diversity indexes non-monotonically decreased as the depth of the permafrost active layer increased,and the maximal values of species diversity indexes occurred at about 2 m depth of the permafrost active layer（the Partrick index,Shannon-Wiener index and Simpson index are respectively 26.43±3.31,2.06±0.38 and 0.83±0.08）.2） In terms of the vertical distribution of biomass,underground biomass was considerably larger than aboveground biomass,underground biomass occupied 63%-96% of the total biomass.3） There was a significant correlation between biomass and depth of the permafrost active layer（R2=0.65,P〈0.01 for aboveground biomass and R2=0.79,P〈0.01 for underground biomass）,and both aboveground and underground biomasses decreased as the depth of the permafrost active layer increased.4） The depth of the permafrost active layer had a considerable influence on the vertical distribution of underground biomass at soil depths of 0-40 cm： when the depth of the permafrost active layer was about 1 m,there was little vertical variation of underground biomass;but there was an obpyramidal pattern when the depth of permafrost active layer was larger than 1.5 m.When the depth of this layer was larger than 3 m,the ratio of underground biomass with soil depths of 10-40 cm to total underground biomass increased as the depth of the permafrost active layer increased.