Analysis On Species Coexistence And Diversity Maintenance Of Three Forest Communities At Mt.huangshan

Forest structure determines function,and its structural stability and functional complexity are affected by biodiversity.The coexisence of species and the formation of biodiversity in a community are influenced by both internal factors,such as species competition exclusion,dispersal restriction and genetic variation,and external factors such as spatial distance and environmental factors including climate,topography and soil.Therefore,it has always been a classic content of ecological research to infer the assembly process of different communities and explore how various factors affect the construction of community.Based on the forest dynamic monitoring plots established at Mt.Huangshan,three different types of forest communities were studied in this paper according to the latest viewpoints of ecological theory,focusing on Evergreen Broadleaf Forest(EBF),Deciduous Broadleaf Forest(DBF)and Mixed Needleleaf and Broadleaf Forest(MNBF).The spatial structure and stability of the community were evaluated based on four spatial structure parameters.The phylogenetic tree was constructed based on three DNA barcodes(ITS2,rbc L,mat K)and APG IV system.Six functional traits of tree species were quantified by morphological and chemical analysis,and then functional tree was constructed.We explore the differences among three different communities and their responses to environmental factors and spatial distance according to the methods of species diversity,phylogenetical and functional diversity.The relationship between spatial structure parameters and multidimensional biodiversity was analyzed based on Pearson correlation.The objective of this study is to explore the mechanisms of species coexistence and diversity maintenance of forest communities at Mt.Huangshan,and to analyze the potential impacts of environmental changes on community structure and function.The main conclusion of the study is as follows:1.The characteristics of stand diameter distribution in three forests showed that the lognormal distribution fitted best.Most trees in the three communities were extremely dense and slightly clumped,with a moderate size differentiation and high mixed structure,which not reached the natural climax community.In Mixed Needleleaf and Broadleaf Forest,the distribution pattern of tree species was the best,that is,the stand stability was the highest,followed by Evergreen Broadleaf forest and Deciduous Broadleaf Forest.With the increasing of elevation,the degree of the mingling index(M)and the crowdedness index(C)increased,however,there was no influence on the uniform angle index(W)and the diameter dominance index(U).Further,at the same elevation,the uniform angle index(W)and the mingling index(M)of shady slope were larger than that of sunny slope,however,there was no difference in the diameter dominance index(U)and the crowdedness index(C)between sunny and shade slope.2.The comparative analysis of species α-diversity showed that Mixed Needleleaf and Broadleaf Forest > Evergreen Broadleaf Forest > Deciduous Broadleaf Forest,and speciesα-diversity of shrub canopy layer in each community was larger than tree canopy layer,which was greatly affected by the spatial distance.The results of speciesβ-diversity showed that the species composition of Deciduous Broadleaf Forest was the largest,followed by Evergreen Broadleaf forest and Mixed Needleleaf and Broadleaf Forest.The results of species β-diversity decomposition showed that species replacement contributed moreto species β-diversity in EBF and DBF,while Jaccard similarity in Mixed Needleleaf and Broadleaf Forest.The richness difference in three communities contributed little to β-diversity.Species-diversity was significantly affected by environmental factors and spatial distance,but the percent of explained by environmental factors was higher.3.The phylogenetic tree with ITS2+rbc L+mat K was a higher identification(93.18%)than phylogenetic tree with single brocading.The constrained tree with the guiding tree of APG IV was better phylogenies than the unconstrained tree and the APG IV tree.The phylogenetic structure of three different canopy layers in Evergreen Broadleaf Forest and Evergreen Broadleaf forest is clustered,however,the phylogenetic structure of total and tree species in Deciduous Broadleaf Forest is dispersion,and shrub species showed clustered.Both environmental factors and spatial distance had significantly effect on phylogenetic structure.The results of phylogenetic α-diversity showed Mixed Needleleaf and Broadleaf Forest >Evergreen Broadleaf Forest > Deciduous Broadleaf Forest;the diversity of phylogeneticβ-diversity was driven by both phylogenetic displacement and phylogenetic nesting components,which phylogenetic displacement contributed more than the nested components and phylogenetic displacement provide most higher in Deciduous Broadleaf Forest.Phylogenetic β-diversity was significantly correlated with spatial distance and environmental factors,and environmental factors explained more β-diversity.4.There was a coupling tradeoff between the six functional traits in three different forests at Mt.Huangshan,that is,specific leaf area(SLA)was significantly negatively correlated with leaf thickness(LT),leaf carbon concentration(LCC)and leaf phosphorus concentration(LPC),SLA was significantly positively correlated with leaf nitrogen concentration(LNC),LNC was positively correlated with LPC.The variation analysis of six functional traits showed that the intraspecific variation was greater than the interspecific variation in LCC in Deciduous Broadleaf Forest,and the interspecific variation was greater than the intraspecific variation in other communities.The six functional traits showed weak phylogenetic signals in three forest communities(K<1),which was lower than the expected value of Brownian motion model.For EBF and MNBF,the functional structure of different canopy layers exhibited clustered.However,for tree species in DBF,the functional structure showed random or slightly dispersion and clustered was observed for total and shrub species.For three communities,Functional richness(FRic)in MNBF played a predominant role,but functional evenness(FEve),functional dispersion(FDis)and functional divergence(FDiv)in DBF was the highest.The functionalβ-diversity of Evergreen Broadleaf Forest and Mixed Needleleaf and Broadleaf Forest was dispersion,while the shrub canopy layer of Deciduous Broadleaf Forest showed clustered.Similarly,function displacement and function nesting components drive function β-diversity together,and function displacement contributed more.Linear regression between mean pairing functional-phylogenetic distance(MFPD)and forest types found that functional distance and phylogenetic distance were equal in total canopy layer at Mt.Huangshan,but functional distance was greater than phylogenetic distance in tree and shrub canopy layer.Environmental factors and spatial distance have significant effects on functional diversity.Similarly,environmental factors had a higher explained rate for the variance.It is suggested that niche-based processes may dominate the assembly of forest communities at Mt.Huangshan,and neutral processes may also contribute to it.5.Mixing(M),uniform angle(W)and crowdedness(C)were positively correlated with species diversity.The uniform angle(W)was positively correlated with functional evenness(FEve),while the crowdedness(C)was negatively correlated with functional dispersion(FDis)and functional dispersion(FDiv).Crowdedness(C)and uniform angle(W)were positively correlated with phylogenetic diversity(PD).Species diversity was positively correlated with phylogenetic diversity and functional richness,but negatively correlated with functional evenness(FEve),functional dispersion(FDis)and functional dispersion(FDiv).The phylogenetic diversity for total and shrub species was negatively correlated with functional diversity,while the phylogenetic diversity for tree species was positively correlated with functional diversity.In summary,environmental factors and spatial distance may jointly drive the spatial structure and multi-dimensional biodiversity of the forest community at Mt.Huangshan,which are the results of deterministic and neutral processes.These factors should be considered comprehensively in the management and protection of forest ecosystem,so as to provide data support and theoretical basis for the maintenance of biodiversity,resource development and sustainable management.