Relationship And Mechanism Between Community Functional Diversity And Productivity In Alpine Grassland

The relationship between biodiversity and productivity has long been a hot topic in ecology.Earlier studies focused on the relationship between species diversity and productivity.However,there is increasing evidence that species diversity has limitations in its ability to explain productivity.With the development of the understanding of biodiversity in different dimensions(species diversity,lineage diversity and functional diversity),it is found that functional diversity is a more effective indicator to explain the change of ecosystem function.However,most of the current studies on functional diversity focus on how to construct functional diversity index and verify the importance of functional diversity.However,there are relatively few studies on the formation of community functional diversity under special environmental conditions and the relationship between functional diversity and productivity and its mechanism.Therefore,based on the research method of plant functional traits,it is of great significance to explore the formation and regulation factors of alpine grassland functional diversity,and clarify the relationship between functional diversity and community productivity and its mechanism for the conservation of biodiversity and the efficient utilization and management of ecosystem in the alpine grassland on the Qinghai-Tibet Plateau.In this paper,the alpine meadow of the Qinghai-Tibet Plateau in Tibet region was selected as the research area.Seven research sites were selected along the environmental gradient.The data of plant community structure,plant leaf functional traits,above-ground biomass of the community and soil physical and chemical indexes were obtained through field investigation,sampling and laboratory analysis.Based on the formation of community functional diversity and the relationship between functional diversity and productivity,functional space was constructed,changes in community functional diversity and main regulatory factors were analyzed,and the relationship between community functional diversity and community productivity and its mechanism were clarified.The main research results are as follows:1.Three-dimensional functional space is constructed based on trade-offs between plant traits: that is,the functional axis PCA1(leaf area,leaf saturated fresh weight,specific leaf area,leaf thickness)is related to plant organ size,the functional axis PCA2(chlorophyll,nitrogen,phosphorus)is related to plant resource acquisition,and the functional axis PCA3(carbon,starch,soluble sugar)is related to plant stress resistance.PCA1,a functional axis representing plant organ size,decreased significantly with increasing elevation,the functional axis PCA2,representing resource acquisition,and the functional axis PCA3,representing plant stress resistance,increased significantly with the increase of elevation.The regulatory factors of each functional axis are different.Functional axis PCA1 is mainly affected by soil factors,functional axis PCA2 is mainly affected by climate,and functional axis PCA3 is mainly affected by soil factors.2.Based overall traits functional richness(FRic)and functional dispersion(Rao Q)decreased significantly with the increase of elevation,while functional evenness(FEve)did not change significantly with the increase of elevation.Functional richness and functional dispersion were mainly affected by species diversity,while functional evenness was mainly affected by soil factors.Functional diversity based on functional axis has a significant elevation trend.The functional richness,functional evenness and functional dispersion of PCA1 based on functional axis decreased with the increase of elevation,the functional dispersion of PCA2 based on functional axis increased with the increase of elevation,and the functional richness of PCA3 based on functional axis increased with the increase of elevation.The functional richness based on functional axis was mainly affected by species diversity.The functional evenness and functional dispersion based on functional axis were mainly affected by species diversity and soil factors.3.The community productivity changed significantly along the environmental gradient.With the gradual decrease of annual average precipitation,the community productivity decreased gradually,and the community productivity of alpine meadow was higher than that of alpine steppe.Community productivity increased significantly with the increase of functional richness and functional dispersion,but there was no significant relationship between functional evenness and community productivity.The community productivity was mainly affected by environmental factors,followed by the interaction of species diversity,functional diversity and environmental factors.Among the effects of functional diversity on community productivity,CWM had a greater effect on community productivity than Rao Q,indicating that the selection effect was more dominant than the complementary effect.