Community Assembly Of Evergreen And Deciduous Broad-leaved Mixed Forest Based On Phylogeny And Functional Traits In Karst Hills Of Guilin,Southwest China

Forest ecosystems are an important part of global biodiversity,and the community assembly research in forest ecosystems has always been a hot topic in ecological research.Due to the strong karstification and special geological background,the karst hills ecosystem is usually relatively fragile,especially under human disturbance,environmental problems such as rocky desertification,soil erosion,and drought often occur.Evergreen and deciduous broad-leaved mixed forest is one of the typical forest vegetation types in the mid-subtropical karst hills,and plays an important functional role in maintaining the ecological environment of the karst hills.In view of this,this study took the evergreen deciduous broad-leaved mixed forest community in the karst hills of Guilin as the research object.A 2 hm~2 plot of 200 m×100 m was established in Long Village,Luojin Town,Yongfu County,Guilin,in accordance with the standards of the Center for Tropical Forest Science（CTFS）.Through community survey,functional trait determination and environmental factor analysis,combined with the two different perspectives of phylogenetic structure and functional traits,to reveal the ecological mechanism driving the construction of evergreen and deciduous broad-leaved mixed forest community in Karst hills,and to clarify the factors that dominate the process of community assembly and its response to environmental changes.The purpose is to enrich the research on the community assembly in karst areas,and to provide a reliable theoretical basis for biodiversity conservation,restoration and reconstruction and sustainable development of karst hills plant communities.The main findings of this study are as follows:（1）Composition of evergreen and deciduous broad-leaved mixed forests in karst hills of GuilinA total of 110 species were recorded in this plant community survey,belonging to 47families and 86 genera,including 58 evergreens,52 deciduous plants,60 trees,45 shrubs,and 5 woody vines.（2）Distribution and variation of plant functional traits in evergreen and deciduous broad-leaved mixed forest in Karst hills of GuilinThe frequency distributions of the six functional traits of chlorophyll content,leaf thickness,leaf area,leaf dry matter content,specific leaf area,and branch tissue density at the leaf/branch,individual and species levels are mostly long-tailed distributions,indicating that the study The differentiation of functional traits in the region is larger,that is,the degree of niche differentiation is higher.On the organizational scale of family,genus and species,the relationship between family,genus and species explained most of the variance of functional trait variation,indicating that evolutionary history has a certain impact on community functional traits.（3）The community assembly of evergreen deciduous broad-leaved mixed forest in karst hills of GuilinThe research results based on community functional trait structure and phylogenetic structure show that the phylogenetic signal of the evergreen deciduous broad-leaved mixed forest community in Karst hills of Guilin is weak,indicating that evolutionary history has influenced the plants in the evergreen and deciduous broad-leaved mixed forest in Karst hills of Guilin.The community influence intensity is not high.At the same time,it also suggested that there may be large differences between the functional trait pattern and phylogenetic pattern,and the lack of consistency.The community assembly of the evergreen deciduous broad-leaved mixed forest in the karst hills of Guilin showed obvious scale dependence,that is,with the increase of sampling scale,the environmental filtering effect weakened and the similarity limiting effect became stronger.At the same time,the results of null model analysis based on functional traits showed that the community assembly of evergreen and deciduous broad-leaved mixed forest in karst hills of Guilin was driven by deterministic processes,namely environmental filtering and similarity restriction.（4）Responses of environmental factors to the community phylogenetic and functionalβ-diversity of the evergreen and deciduous broad-leaved mixed forest in the karst hills of GuilinMantel correlation analysis shows that the community phylogenetic and functionalβ-diversity distribution pattern of evergreen and deciduous broad-leaved mixed forest in karst hills of Guilin are significantly affected by the environment.The results of permutation multivariate analysis of variance indicated that soil available nitrogen and rock exposure rate were the main driving factors.Other important environmental factors include total soil phosphorus,available potassium,soil water content,slope,altitude and so on.In conclusion,the community assembly of evergreen and deciduous broad-leaved mixed forest community in the karst hills of Guilin is a complex ecological process,in which environmental filtering and similarity restriction play a leading role.The main environmental factors affecting the spatial pattern of evergreen and deciduous broad-leaved mixed forest were soil available nitrogen and rock exposure rate.