西藏草地植物功能性状与多项生态系统服务关系

针对植被功能性状与生态系统服务功能之间的相互关系,构建了西藏草地株高和可食性两种功能性状的9项指标,并基于土壤和植物采样,分析了9项植物功能性状指标和5项生态系统服务指标间的相关性,探讨了4种机制(Mass ratio,Selection,Niche complementarity及Insurance)在西藏草地的适用性。结果表明,9项功能性状指标中,株高Rao和可食种与所有种株高CWM比分别与土壤有机碳、土壤全氮和土壤含水率3项生态系统服务指标呈显著负相关及显著正相关。说明群落植被对光能竞争的互补性及可食性状植株在群落中的光能资源相对竞争力,与土壤固碳、肥力供给及水源涵养有显著相关关系。而群落可食种、优势种、优势种与次优势种对光能资源竞争力水平,可食植株多样性、可食植株在群落中的优势度及其光能资源竞争力均值,对草地生态系统服务无显著影响。西藏草地植物功能性状对多项生态系统服务的影响机制从光能资源竞争角度更符合Niche complementarity和Insurance理论,而从可食功能性状角度更符合Mass ratio和Selection理论。

The relationship between plant functional traits and multiple ecosystem services in a Tibetan grassland ecosystem

We studied the relationships among plant functional traits and multiple ecosystem services. Nine indicators of plant functional traits of plant heights and palatability were established, which were Rao index of plant heights, the community weighted mean value (CWM) of plant heights of all species, the CWM of plant heights of dominant species, the CWM of plant heights of dominant and subdominant species, the richness of palatable plants, the richness ratio of palatable species to all species, the ratio of palatable biomass to total biomass, the CWM of plant heights of palatable species, and the CWM of the ratio of heights of palatable plants to all plant species. The ecosystem services we analyzed included forage supply, soil carbon stocks, soil fertilization supply, water regulation, and soil retention. Further, we attempted to test four candidate mechanisms by which plant functional traits influence ecosystem services. These were:1) mass ratio, 2) selection, 3) niche complementarity, and 4) insurance. In 2012, we collected soil and vegetation samples from Xincang village, Lhasa, Tibet. Ecosystem services and plant functional traits were quantified based on these samplings. Pearson correlations were calculated among the nine functional traits, as well as between the functional traits and ecosystem services. The results showed that among the functional traits, the Rao index of plant heights was significant negatively correlated with soil organic carbon, soil total nitrogen, and soil water content. The ratio of the CWM of the heights of palatable plants to all plant species was significant positively correlated with soil organic carbon, soil total nitrogen, and soil water content. However, the CWM of the plant heights of all species, palatable species, dominant species, dominant and subdominant species, as well as the richness of palatable species, the ratio of the palatable specie richness to all species, and the ratio of palatable biomass to all species, were not significantly correlated with any of the ecosystem services. Our results demonstrated that the niche complementarity of the light captures of the plant community has negative impacts on ecosystem soil carbon stock, fertilization provisioning, and water regulating services. However, the relative niche competitiveness of light captures of palatable plants in the community has positive impacts on ecosystem soil carbon stock, fertilization provisioning, and water regulating services. The results imply, from the perspective of resource competitiveness, the concepts of niche complementarity and insurance best characterize the mechanisms by which plant functional traits determine ecosystem services in grassland. However, from the perspective of palatability, the concepts of mass ratio and selection are more reasonable.