Functional Traits Differentiation And Environmental Explanation Of Grassland Community In A Semi-arid Loess Watershed

The semi-arid loess area is the most serious area for soil erosion,and it is also the key area for ecological restoration.Scientific and rational vegetation construction is the key to ecological restoration and healthy and sustainable development in the area.Plant functional traits can reflect the community's adaptation strategy to the environment and determine the function of the ecosystem.It is one of the effective ways to study the relationship between vegetation and environment.The spatial heterogeneity and environmental drive of community functional traits at small watershed scale,the response to driving factors and the variation of driving factors,the correlation between response traits is of great significance for local vegetation resource management and vegetation restoration and reconstruction.In this study,we used a combination of sample and sample to investigate the grassland community in a typical semi-arid loess basin,and selected plant height,leaf length,leaf width,leaf thickness,leaf area,specific leaf area,and leaf dry matter content.The relationship between functional traits and environmental factors was studied by variance decomposition,ranking analysis and regression fitting methods.The key driving factors affecting spatial heterogeneity of the weighted mean of community functional traits in the community were identified and the response traits of driving factors were screened.The response of the weighted mean of the response traits and the functional diversity index and the species diversity index to the driving factors and the correlation between the response traits were analyzed.The results show:(1)The influence of environmental factors on the spatial heterogeneity of the weighted mean of community functional traits is soil physical property>soil chemical property>topographic factor,and the correlation between the three groups is strong and the interaction is large,indicating that environmental factors jointly influence and determine the functional traits of vegetation through interaction.Soil available water,total carbon,available nitrogen,total nitrogen,organic carbon,p H,and soil bulk density have significant effects on the spatial heterogeneity of the weighted mean of community functional traits,and soil available water is the dominant factor.(2)In the seven traits of plant height,leaf length,leaf width,leaf thickness,leaf area,specific leaf area and leaf dry matter content,except leaf width and soil available water were not significantly correlated,leaf length,leaf area,specific leaf area,plant height,leaf thickness and leaf dry matter content were significantly correlated with soil available water,which could be identified as grassland response traits of community levels to soil available water.Grassland community adapts to the decrease of soil available water by reducing plant height,leaf length,leaf area and specific leaf area and increasing leaf thickness,dry matter content.The leaf dry matter content has the best fitting goodness and is the optimal response trait to soil available water.Among the soil available water response traits,except that there was no significant correlation between leaf thickness and leaf length,the other functional traits were all significantly correlated,indicating that the functional traits of the grassland community generally had a trade-off relationship on the water gradient.(3)In the four functional diversity index,functional separation index,functional richness index and functional evenness index and soil available water extremely significant positive correlation(P < 0.01),the correlation between functional richness index and soil available water is the strongest(R2 = 0.86),There was no significant positive correlation between functional diversity index and soil available water(R2 = 0.12,P = 0.062).Among the three species diversity indexes,the species richness index and the species diversity index have extremely significant positive correlation with soil available water(P<0.01),the species richness index has the highest correlation with soil available water(R2=0.84),and the species evenness index has no significant positive correlation with soil available water(R2=0.15,P=0.058).