Community Assembly Of South Subtropical Evergreen Broad-leav Ed Forest Based On Phylogeny And Functional Traits

The mechanism of species coexistence in forest communities is one of the core topics of community ecology research,which can reveal how different species form stable commu nity structures in the same habitat and how these structures maintain species coexistence an d diversity.South subtropical evergreen broad-leaved forest is one of the most biodiversityrich forest types in China,and revealing the mechanisms of their species coexistence can he lp provide scientific basis and technical support for forest biodiversity conservation and res toration,and promote the harmonization of forest functions,ecological services,human we ll-being and sustainable development.The analytical method of inferring the relative roles of different ecological processes on community species coexistence based on functional tra its and genealogical structure provides a new perspective and ideas to explore scientific iss ues such as species coexistence mechanisms.In this paper,we used a large scale permanent plot of south subtropical evergreen broad-leaved forest in Dinghu Mountain as the research object.Through field survey,determination of environmental factors and functional traits,and construction of a genealogical tree,we aimed to explore the mechanisms of species coe xistence in the southern subtropical evergreen broad-leaved forest community from the pers pectives of functional traits and genealogical structure.The main results are as follows:(1)Species coexistence mechanisms of common and occasional species in south subtr opical forests and their influencing factorsThe species of the southern subtropical evergreen broadleaf forest community in Ding hu Mountain were subdivided into common and occasional species to explore how they coe xist harmoniously in the community.The weighted mean values of functional traits differed significantly between common and occasional species,indicating that the two species adop t different adaptation strategies to their environments and thus occupy different ecological n iches to maintain the stability of the community species coexistence mechanism.Occasiona l species,which were less numerous in the community,maintained a high proportion of fun ctional entities.The number of functional entities was significantly and positively correlate d with the number of common and occasional species,and the functional entity richness inc reased much faster with the number of occasional species than with the number of common species,indicating that communities with high richness are less sensitive to species loss.F unctional redundancy was significantly and positively correlated with the number of specie s of common and occasional species,suggesting that southern subtropical forests with high species numbers have greater resistance to disturbance.Functional over-redundancy was si gnificantly and positively correlated with the number of occasional species,indicating that occasional species have a higher density of species in their functional entities.Functional v ulnerability was significantly negatively correlated with the number of common and occasi onal species,indicating that species-rich communities reduced potential functional vulnerab ility,but vulnerability was still higher in species-rich communities.Regarding topographic factors,elevation was the most critical topographic factor affecting the functional diversity of common species,and concavity was the most critical topographic factor affecting the fun ctional diversity of occasional species.In terms of soil factors,RSW was the most critical s oil factor affecting the functional diversity of common species,and AK was the most critica l environmental factor affecting the functional diversity of occasional species.Common an d occasional species differed in functional diversity and performed different ecological func tions in the community,contributing to their harmonious coexistence.The findings suggest that although species-rich tropical forests have high functional redundancy,the insurance ef fect they provide does not offset the functional vulnerability of the ecosystem.Reducing th e loss of species with unique functional entities and ephemeral species is an effective and n ecessary way to avoid damage to species coexistence mechanisms and ecosystem functions in tropical forest communities.(2)Quantifying the relative roles of various ecological processes on species coexistenc e mechanisms based on STEPCAM modelBased on the large-scale species data and functional trait monitoring data of large fixe d sample sites in the southern subtropical evergreen broadleaf forest of Dinghu Mountain,t he STEPCAM model was used to quantify the relative roles of dispersal limitation,environ mental filtering and similarity limitation on species coexistence.It was found that species c oexistence in southern subtropical broadleaf evergreen forests in Dinghu Mountain was ma inly driven by dispersal limitation processes,with the mean relative contribution of 76.7% f or dispersal limitation processes,15.4% for environmental filtering processes,and 7.9% for similarity limitation processes,and the relative contribution of the three processes differed significantly.As the spatial scale increased,the relative effects of diffusion limitation on co mmunity species coexistence did not differ significantly,the relative effects of environment al filtering on community species coexistence gradually decreased,and the relative effects of similarity limitation on community species coexistence gradually decreased.The relative roles of diffusion limitation,environmental filtering and similarity limitation were signific antly different at different individual growth stages,showing that diffusion limitation > env ironmental filtering > similarity limitation.The relative effects of diffusion limitation on sp ecies coexistence in forest communities first increased and then decreased with the growth of growth stages.The relative roles of environmental filtering and similarity restriction on s pecies coexistence in forest communities both became larger with the growth stage.(3)Analysis of species coexistence mechanisms in southern subtropical forest broadle af evergreen forests based on functional traits and genealogical structural characteristicsThis study investigated the effects of different ecological processes on the coexistence of community species by calculating the phylogenetic signals of functional traits and analy zing the distribution patterns of functional traits and genealogical structures.It was shown t hat the weak phylogenetic signal of functional traits in the southern subtropical broadleaf e vergreen forest community indicated that the evolutionary history had a low intensity of inf luence on species coexistence in this community.It also implies that the distribution pattern s of functional traits and genealogical structures may be different and lack consistency.The results based on the distribution patterns of functional traits suggest that the role of environ mental filtering on species coexistence in southern subtropical broadleaf evergreen forest c ommunities is scale-dependent and gradually increases with spatial scale.The results of spe cies coexistence mechanism based on genealogical structure showed that environmental filt ering played a dominant role in species coexistence in the evergreen broad-leaved forest co mmunities in the south subtropics,but did not have a scale-dependent effect,i.e.,no change with increasing spatial scale.By studying the functional traits and genealogical structural c haracteristics of the south subtropical forests,we can reveal the role of different ecological processes on community species coexistence at different scales and provide scientific basis for the conservation of diversity and sustainable development of forest communities in the region.