西藏高寒草地物种多样性和生产力的环境驱动机制

全球变暖影响物种多样性和生产力及其关系。关于全球和区域的物种多样性与生产力关系已有许多研究,但气候变暖背景下西藏高寒草地物种多样性与生产力的关系及其环境驱动机制研究仍然很少。基于西藏高寒草地实测的35个样点调查数据,利用回归分析、Pearson相关性分析、方差分解和结构方程模型等方法,探究了物种多样性和生产力的关系及其影响机制。研究发现:(1)高寒草地的物种丰富度指数和香农-威纳指数与地上植被净初级生产力(ANPP)呈显著正相关关系,且ANPP对物种丰富度指数的变化更为敏感;(2)物种丰富度指数与经度、土壤有效氮、土壤有效磷、年降水量呈显著正相关;Shannon-Wiener指数与海拔和纬度呈显著负相关,与年均温度呈显著正相关;ANPP与经度、土壤有效氮、年降水量和年均温度呈显著正相关,与海拔、纬度和土壤有效钾呈显著负相关;(3)地理因子、土壤养分和气候因子的交互作用对物种丰富度指数和ANPP的贡献率最大,分别为10.99%和32.91%,地理因子和气候因子的交互作用对Shannon-Wiener指数的贡献率最大,为13.61%;(4)地理因子通过调控土壤养分和气候因子间接影响物种多样性和ANPP,土壤养分和气候因子均直接影响物种多样性和ANPP。研究结果揭示了环境因子对物种多样性和生产力的综合调控机制,为西藏高寒草地生态系统科学应对气候变化提供了依据。

Environmental driving mechanism of species diversity and productivity in Tibetan alpine grasslands

Global warming affects species diversity and productivity and their relationships. Lots of studies on relationships between species diversity and productivity have been done at the global and regional scales, but few studies have been done in the alpine grassland of Tibetan Plateau under the background of climate warming. This study explored the relationship between species diversity and productivity and its influencing mechanism by using measured data from 35 sample sites in alpine grasslands, combined with regression analysis, Pearson correlation analysis, variance partitioning analysis and structural equation model. The results showed that: (1) The species richness index and the Shannon-Wiener index of alpine grassland were significantly positively correlated with the net primary productivity of aboveground vegetation (ANPP), and the ANPP was more sensitive to the change of the species richness index. (2) The species richness index was positively correlated with longitude, soil available nitrogen, soil available phosphorus and mean annual precipitation. The Shannon-Wiener index was negatively correlated with altitude and latitude, but positively correlated with mean annual temperature. The ANPP was positively correlated with longitude, soil available nitrogen, mean annual precipitation and mean annual temperature, but negatively correlated with altitude, latitude and soil available potassium. (3) The interaction of geographic factors, soil nutrient and climatic factors had the largest contribution on the species richness index and ANPP with 10.99% and 32.91%, respectively, while the interaction of geographic factors and climatic factors had the largest contribution on the Shannon-Wiener index with 13.61%. (4) Geographic factors indirectly affected species diversity and ANPP through the regulation of soil nutrient and climatic factors while soil nutrient and climatic factors directly affected species diversity and ANPP. The results reveal the comprehensive regulation mechanism of environmental factors on species diversity and productivity, and provide a basis for the scientific response to climate change in the alpine grassland ecosystem of Tibet.