Study On The Relationship Between Functional Diversity And Ecosystem Function Of Herbaceous Plant Community

Along with the development of functional ecology, researches of plant functional diversity, especially the effect of functional diversity on ecosystem function is now attracting more and more attentions. There are two hypotheses on the mechanism of functional diversity driving ecosystem processes:one is the mass ratio hypothesis based on dominant species, and the other is the diversity hypothesis based on ecological niche. This paper compared the aboveground biomass, species diversity, functional diversity (community weighted mean and Rao’s quadratic entropy) and several environmental factors among different meadow and marsh plant communities in the west of Jilin province. The functional diversity was calculated for7plant traits. The relationships between diversity index and aboveground biomass were explored. Furthermore, we tested whether the explanation ability of these two hypotheses to productivity is influenced by the existence of intensive environmental filter, which was flooded condition in this study.(1) Plant functional traits were closely correlated with each other. Leaf dry matter content was negatively significantly correlated with specific leaf area, but positively significantly correlated with leaf lignin content. Specific leaf area was negatively significantly correlated with leaf size, plant height and leaf lignin content. Leaf size was positively significantly correlated with plant height. Leaf nitrogen content and leaf carbon content had no significant correlation with other leaf traits. Compared with plant nutritional traits, there were more close relationships between plant morphological traits with other traits.(2) There were significant differences of functional diversity among communities, including community weighted mean and Rao’s quadratic entropy. Except FDh, other functional diversity indexes showed significant differences among meadow communities. The difference of about1/3functional diversity indexes were not significant among marsh communities.(3) Soil factors affected functional diversity. The main factors influencing Rao’s quadratic entropy were soil total nitrogen, soil total phosphorus and soil pH. While the main factors influencing community weighted mean were soil physical properties including soil electric conductivity, soil pH and soil volumetric moisture content.(4) Species diversity and function diversity was interconnected but not the same. FDmerged was positively significantly correlated with species richness and Shannon-Weaver index. For a single traits quantitative functional diversity, except FDLCC and FDLNC, other Rao’s quadratic entropy indexes showed significant correlation with species diversity. CWMLCC and CWMLignin were significantly negatively correlated with species diversity. CWMLCC and CWMLS were positively significantly correlated with Shannon-Weaver index.(5) Functional diversity could better explain community productivity change than species diversity. Only functional diversity indexes, including FDLs, FDLDMC, CWMH, CWMLS and FDSLA entered the final stepwise regression equation among all communities. And CWMH and CWMLS explained more variation of community productivity.(6) Community weighting mean and Rao quadratic entropy had different explanation ability on productivity change. Strong environmental filter affected the relationship between functional diversity and productivity. In meadow communities, CWMH and CWMSLA entered the final equation, and CWMH explained more variation of community productivity. In marsh communities, productivity was impacted by FDLDMC and soil pH.