藏北高寒草地样带物种多样性沿降水梯度的分布格局

摘要

在藏北高原高寒草地样带上对40个围栏内草地群落物种多样性和地上生物量进行测定,探讨了生长季降水对高寒草地生物量和物种多样性分布格局的影响以及地上生物量-物种多样性之间的关系模式.结果表明,降水格局显著地影响藏北高原内部高寒草地群落物种丰富度、多样性和均匀度,群落结构特征与初级生产力关系密切;藏北地区高寒草地地上生物量、物种丰富度、Shannon- Wiener指数和Pielou均匀度指数随生长季累积降水呈指数增加趋势:在高寒草地群落物种丰富度-生产力关系研究中单峰模式的判别系数R2(0.754)略高于线性回归模型(0.743).沿藏北高原样带高寒草地物种丰富度随地上生物量单调递增,单蜂模式的单调递减区间并未出现;然而单峰模型预示着在地上生物量高于121.17 g/m2的高寒草地群落物种丰富度可能随生物量单调递减,从而使物种丰富度-地上生物量表现为较为标准的单峰模式;Shannon-Wiener多样性指数和Pielou均匀度指数与地上生物量也均呈单峰模式,但其单调递减区间窄于单调递增区间,峰值分别对应的草地群落地上生物量为71.90和60.90g/m2.%Aboveground biomass and community stricture at 40 sites with grazing exclusion were surveyed on a west-east alpine grassland transect along precipitation gradient in Northern Tibetan Plateau to evaluate effect of growing season rainfall on both aboveground biomass and species diversity and to discuss the relationship between aboveground biomass and species diversity indexes. The precipitation pattern significantly affected species richness, Shannon-Wiener diversity and Pielou evenness indexes of the alpine communities in inner Northern Tibetan Plateau and that community structure related closely with primary productivity. All of aboveground biomass, species richness, Shannon-Wiener diversity index and Pielou evenness index exponentially increased with growing season precipitation addition. In the relationship between species richness and aboveground biomass of alpine grasslands, the discriminant coefficient of the hump-shaped model (R2 =0. 754) was slightly higher than linear regression (R2= 0. 743), however, species richness monotonically increased with aboveground biomass of alpine grasslands along Northern Tibetan Plateau Transect without any monoton-ic decreasing interval in the hump-shaped model. Moreover, hump-shaped model in our results indicated that species richness more likely showed a monotonic decreasing with aboveground biomass when it was more than 121. 17 g/m2 and to make this humped relationship to be standard. Hump-shaped models described both Shannon-Wiener biodiversity and Pielou evenness index with aboveground biomass that decreasing intervals were relatively narrower than increasing ones and peak values took place at aboveground biomass of 71. 90 and 60. 90 g/m2 respectively.