Terrestrial Plant Community Assembly Mechanisms During The Ecological Restoration Process In Dianchi Lakeside Zone

Lakeside zone,as a functional transition area linking aquatic ecosystem with terrestrial ecosystem,is a natural protection barrier of lakes.Therefore,the ecological restoration of lakeside based on plant community assembly is the key process during the recovering ecosystem of plateau lakes.The ecological restoration of Dianchi Lake is one of the important ecological management projects in China.Although a large body of studies about the research and practice of the restoration of the lakeside habitats in Dianchi Lake have been reported,the mechanism of terrestrial plant community assembly in the lakeshore is rarely studied.The assembly of plant communities is the result of the interaction of niche processes and neutral processes.However,exotic disturbance(especially human disturbance)always influence the succession and assembly process of plant communities.The lakeside zone of Dianchi Lake,which adjacent to the Kunming city,is densely-populated and under high frequency of human activities.Thus,the assembly of plant communities and the ecological restoration process of lakeside zone is undoubtedly influenced by exotic human disturbance.In the present study,we first conducted the detailed field investigation and analysis of different plant communities along the Dianchi lakeside.Then,we selected typical habitats and plant communities with natural community successions to study the mechanisms of terrestrial plant communities assembly in Dianchi lakeside zone by a phylogenetic and functional trait-based method.Meanwhile,the factors that influencing the community assembly were also explored based on redundancy analysis(RDA),variance partitioning analysis,Mantel test and multiple regressions on distance matrics(MRM).The results will provide a scientific theoretical basis for ecological restoration and management of Dianchi Lake shore.The main results and conclusions were summarized as below:1.Based on the field investigation of terrestrial plant communities in 23 sample plots along Dianchi lakeside,the habitats are classified into four types according to different land use patterns and intensities of human disturbance: wetland park(WP),abandoned wetland park(AW),abandoned farmland(AF)and mountain land(ML).The species composition of the four types of habitats are dominated by cultivated plants,especially trees and shrubs.The major natural-growing species are herbs,mainly distribute in the family of Poaceae and Asteraceae.In addition,a variety of invasive plants were found in different habitats,and the dominance of invasive species became more obvious with the increase of human disturbance.Therefore,the assembly and species composition of terrestrial plant communities in Dianchi lakeside are obviously influenced by human disturbance.2.The results of the plant community assembly mechanisms in 10 plots of 3 kinds of habitats(ML,AF and AW)showed that the phylogenetic signals of 8 functional traits of the dominant species in the 10 plots are not significant,suggesting the traits are convergent.The community phylogenetic structure indices(NRI and NTI)of 8plots do not deviate significantly from the null model,the phylogenetic structure of 3kinds of habitats show a random pattern.Thus,the plant community assembly are drived by competitive exclusion in Dianchi lakeside zone.The phylogenetic beta diversity patterns of the 3 habitats indicated that environmental heterogeneity influences the phylogenetic diversity of different plant communities in ML,while competitive exclusion affact the phylogenetic beta diversity of different communities in AF and AW.Community functional structures indices(S.E.S PW and S.E.S NN)in most plots of the 3 habitats also display a random pattern,suggesting that the neutral process is the driving factor of community assembly.However,the change of functional beta diversity in different communities indicated that environmental filtring might affact the assembly of plant communities in ML and AF,while the plant communities in AW may be influenced by strong human disturbance.Based on the combined analysis of phylogeny and functional traits,the assemmbly of terrestrial plant communities in 3 habitats in the Dianchi Lake littoral zone are driven by both competitive exclusion and neutral processes.3.The analysis of the impact factors which influence plant community assembly in Dianchi lakeside showed that the trade-off of leaves economic spectrum at community level varied among different habitats and it's related to soil factors.The RDA and variance partitioning analysis indicated that the habitat types and species invasion influence species composition,while soil and space factors relate to species richness of plant communities.NRI can be explained more by environmental factors and species invasion,but NTI is mainly affected by environmental factors.Functional structure of communities is influenced by environmental factors,spatial factors and species invasion,especially spatial and environmental factors are more important to explain the change of functional structure in different communities.The results of Mantel test and MRM analysis showed that the change of species in different communities are influenced by soil factors and species invasion,but the change of phylogenetic and functional diversity of pant communities are influenced by species invasion on nearest neighbor distance(Dnn).Consequently,we can conclude that the certainty factors(such as the differences of habitats and species invasion caused by human disturbance)drive the composition and dicersity of species and the change of phylogenetic and function structure in different plant communities,and the random factors(such as diffusion limitation)affect the species richness and function diversity of plant communities in Dianchi lakeside.In conclusion,the plant community assembly in the Dianchi lakeside zone is driven by both niche processes dominated by competitive exclusion and neutral process.Meanwhile,the community assembly and succession processes are influenced by the external disturbance dominated by human activities and species invasion,habitat soil conditions and diffusion limitation.The results of this study not only provided new insights into the assembly mechanism of disturbed plant communities,but also provided a scientific basis for the practice and management of ecological restoration in lakeside of Dianchi and other plateau lakes.