A Study On Mechanism Of Community Assembly In Qinling And Loess Plateau Quercus Wataishanica Forests

Mechanism of community assemblyhas long been a core issue in ecology,and reveals the potential process of species coexistence and the maintenance of biodiversity.The theory of community assembly has dominated community ecology for nearly a century,yet understanding of the mechanisms of community assembly has remained elusive.In recent years,the methods based on phylogeny and functional traits provide new sight in studying mechanism of community assembly from plant evolution and functional adaptation,and to increase the understanding of species coexistence and the maintenance of biodiversity.Vegetation destruction is serious in Qinling Mountains and the Loess Plateau due to the frequent impacts of human activities.Therefore,the protection of species diversity and the restoration must be highly valued.The study on the mechanism of forest community assembly is the basis of vegetation protection,restoration and reconstruction.Thus,focus on Quercus wataishanica forests,the most stable community in Qinling Mountains and the Loess Plateau,this study analyzed the mechanism of community assembly in Qinling Quercus wataishanica forests and Loess Plateau Quercus wataishanica forests,by using the method based on phylogeny and functional traits.The main results are as follows:(1)Correlation between leaf functional traits and non-leaf functional traits in Qinling and Loess Plateau Quercus wataishanica forestsproved the connection of the plant organs.Meanwhile,leaf functional traits were significantly correlated with seed mass and plant height,indicating that the functional traits of different organs and tissues were coordinated to maintain the life history of plants.Differences in environmental conditions between Qinling Quercus wataishanica forests and Loess Plateau Quercus wataishanica forests lead to different functional traits and their alpha,beta components.The relationshipsamongstfunctional traits and between traits environment were also different.All of these reflectedthat Qinling Quercus wataishanica forests and Loess Plateau Quercus wataishanica forests have different survival strategies.(2)The phylogenetic structure of Qinling Quercus wataishanica foreststended to be phylogenetically clustered,indicating that environmental filtering was the dominantprocess in community assembly.Soil p H and nitrate nitrogen contents significantly affected the phylogenetic structure,but the limiting similarity was still not to be ignored.Phylogenetic diversity of Qinling Quercus wataishanica forests was significantly correlated with multiple environmental factors,and it was proved once again that environmental filtering dominated the process of community assembly.Functional structuredepend on functional traits,and most functional traits exhibited functionally clustered in Qinling Quercus wataishanica forests,which indicated that environmental filtering was a core process in the community functional structureassembly.Functional richness index(FRic)was significantly correlated with soil available phosphorus content,which means that soil available phosphorus content was the main environmental factor affected the functional diversity.There had a difference of phylogenetic structure,phylogenetic diversity,functional structure,functional diversity(FRic,FDiv,FDis,Rao Q)between trees and shrubs in Qinling Quercus wataishanica forests,which reflected trees and shrubs adopted different life strategies for difference of competition ability.(3)The phylogenetic structure of Loess Plateau Quercus wataishanica forests also tended to be phylogenetically clustered,indicating that environmental filtering was the main driving factors of community assemblyprocess.Soil p H significantly affected the phylogenetic structure,soil water content and nitrate nitrogen positively correlated with phylogenetic βdiversity,soil ammonium nitrogennegatively correlated with phylogenetic β diversity.Most functional traits exhibited functionally clustered in Loess Plateau Quercus wataishanica forests,which indicated that environmental filteringis the dominantprocess in community functional structureassembly.Aboutfunctional diversity,functional evenness(FEve)was significantly positively correlated with soil water content.There was no significant difference of phylogenetic structure between trees and shrubs in Loess Plateau Quercus wataishanica forests,but the main environmental factor drove the community phylogenetic structurevaried.Soil p Hnegatively correlated with phylogenetic structure of trees,soil nitrate nitrogennegatively correlated with phylogenetic structure of shrubs.Phylogenetic β diversity,functional diversity(FDis,Rao Q)in trees was higher,which showed that the effect of environmental filtering inshrubswas obviousthan that in trees of Loess Plateau Quercus wataishanica forests.(4)Comparison of phylogenetic structure between Qinling Quercus wataishanica forests and Loess Plateau Quercus wataishanica forests found Quercus wataishanica forests phylogenetically clustered more in Loess Plateau,which means that environmental filteringcontributed more in Loess Plateau Quercus wataishanica forests.Qinling Quercus wataishanica forestshad higher phylogenetic diversity than Loess Plateau Quercus wataishanica forests,which may be caused by the difference of species diversity between two forests.There were differences in functional diversity,Qinling Quercus wataishanica forests was higher in functional evenness(FEve),but lower in functional richness(FRic).Community succession,environmental factors and other factors made the difference of community assemblymechanism based on phylogeny and functional traits.In summary,environmental filteringdominated thecommunity assembly of Qinling and Loess Plateau Quercus wataishanica forests in temperate regions,and this effect was more significant in the Loess Plateau Quercus wataishanica forests than that in Qinling Quercus wataishanica forests.Studying the mechanism of community assembly in Qinling Mountains and the Loess Plateau Quercus wataishanica forests can develop the understanding of species coexistence and the maintenance of biodiversity in plantcommunities.Meanwhile,it also provided scientific basis for the ecological construction of Qinling Mountains and the Loess plateau.