羌塘高寒草地物种多样性与生态系统多功能关系格局

传统的生物多样性-生态系统功能研究大多侧重于单一生态系统功能与物种多样性的关系,忽略了生态系统的重要价值在于其能够同时提供多种功能或服务,即生态系统的多功能性。基于藏北羌塘高寒草地样带调查数据,选取植被地上生物量、地下生物量、土壤全氮、硝态氮及铵态氮含量、土壤全磷含量、土壤有机碳储量等7个与植物生长、养分循环、土壤有机碳蓄积相关的参数来表征生态系统多功能性。采用上述参数转换为Z分数后的平均值计算多功能性指数(M)。分析了不同生物多样性指数与生态系统多功能指数的关系以及年降水量和年均温度对物种多样性和生态系统多功能性指数的影响。结果表明,物种丰富度指数与生态系统多功能性之间呈极显著的正相关关系,Shannon-wiener和Simpson物种多样性指数也与多功能性指数间呈显著的正相关,但多功能性指数与Pielou均匀度指数没有表现出明显的相关关系。物种丰富度与表征植物生长、养分循环以及土壤有机碳蓄积的生态系统功能指数间也均呈极显著的正相关关系。降水格局显著影响羌塘高原物种丰富度和生态系统多功能指数,二者均随年降雨量的增加而显著增加,但物种多样性指数并未与年降水量呈现显著相关关系。研究强调了群落物种丰富度即群落物种数量对维持生态系统多功能性的重要意义,这意味着由于人类活动导致的物种丧失可能会给藏北高寒草地生态系统多功能和生态服务带来更为严重的后果。就退化草地恢复或草地可持续管理而言,在藏北羌塘地区,本地植物种的物种丰富度恢复和维持应作为重要目标之一。

The relationship between species diversity and ecosystem multifunctionality in alpine grasslands on the Tibetan Changtang Plateau

The classic species diversity-ecosystem function relationship studies attached more importance on single function and its correlation with diversity despite the fact that most ecosystems are managed or valued for their ability to maintain multiple goods and services simultaneously, so called multifunctionality. Therefore, multifunctionality is an important perspective for biodiversity-function research in point of view of comprehensive function analysis. We conducted an ecosystem multifunctionality vs. biodiversity study on the Tibetan Changtang Plateau, in terms of seven indicators of ecosystem functioning related to plant growth (aboveground biomass, belowground biomass), nutrient cycling (soil total nitrogen content, soil NO₃^- and NH₄⁺ content, soil phosphorus content), and soil carbon storage (soil organic carbon density). Z scores (standardized deviates) of the seven indicators were assessed to represent multifunctionality. The multifunctionality index (M) was calculated as the average Z-score for all indicators measured in each site. Linear regression was used to analyze the relationship between multifunctionality and species diversity indices (Species richness, Shannon-wiener index, Simpson dominance index, Pielou evenness index). We also tested whether ecosystem multifunctionality and species diversity were associated with climatic factors (mean annual temperature and mean annual precipitation) by using linear regression. It was indicated that ecosystem multifunctionality indices were correlated most significantly with species richness, notable positive with Shannon-wiener and Simpson index, but not with Pielou evenness index. Separate analyses of functions related to the plant growth, soil carbon storage and nutrient cycling also yield significantly positive relationships with species richness. Precipitation plays a positive role in affecting species diversity and ecosystem multifunctionality indices, as the species diversity and multiple functions increase linearly with mean annual precipitation. The present study highlights the importance of species richness in maintaining multiple ecosystem functions, goods and services in Changtang Plateau. Because each species contribute to different functions, studies with focus on single function (i.e. net production) might underestimate levels of species richness required to maintain multiple ecosystem goods and services. The alpine grassland ecosystem is vulnerable to climate change and human induced biodiversity loss. It is therefore implied that species loss may cause severe consequence for ecosystem functioning, which would threaten ecosystem health and human well-being in this region. We suggest that the species richness of native species must be maintained and sustained in order to meet the goal of degraded grassland restoration and sustainable management on the Changtang Plateau.