Plant Community Assembly Mechanism In Alpine Meadow Based On Functional Traits And Phylogeny Along Different Abandoned Farmlands

With the increase of human activities,the carrying capacity of biotic and abiotic environments is severely affected,and the balance and stability between biotic and abiotic organisms are disrupted.The mechanism of biodiversity and coexistence of species is of great significance in maintaining the balance of the ecosystem.Therefore,research on biodiversity maintenance and the exploration of species coexistence mechanisms has become an urgent need at present,and biodiversity protection has become one of the focus issues that the ecological community is currently paying close attention to.Community construction aims to reveal the nature of the maintenance and coexistence mechanism of species diversity,and it is also the best description of the dynamic process of biological communities.Therefore,exploring the process of community construction helps to understand the coexistence of species within the community and maintain species diversity.Therefore,the mechanism of community construction has always been a very important part of ecology.This paper takes alpine meadow vegetation as the research object,selects five kinds of sample plots in different habitats according to the abandoned farming time,and combines field community surveys and indoor experiments to determine the environmental factors and soil nutrients in each abandoned farming plot(Soil moisture content,soil temperature,soil bulk density,soil organic carbon,soil total nitrogen,soil total phosphorus,and plant functional traits(plant height,specific leaf area,relative chlorophyll content,leaf total nitrogen,total phosphorus).Establish a zero model based on the functional traits of plants to test the size of the community 's filtering effect on the habitat,and analyze the relationship between plant communities and habitats under different abandoned farming years based on plant functional diversity and environmental factors.The closest relationship index(NRI,NTI)of the plant communities on the plots for each abandoned cultivation period was calculated.A phylogenetic tree of plant community was constructed based on Angiosperm Phylogeny Group(APG)III and I plant.Combining functional traits and phylogeny to calculate phylogenetic signals.This study attempts to explore the community construction process of alpine meadow communities under different abandonment succession stages by using phylogenetic methods and plant functional traits in order to explore how plant communities develop under natural restoration.The results show:(1)Significant changes in community composition occurred at different abandonment succession stages.Plant communities in the early and early middle stages(N1 and N2 stages)of abandoned cropping succession were mainly mixed with annual and perennial herbs,and plant communities in the middle and late stage of abandoned farming succession(N3 stage)were mainly perennial herbs.The plant community is dominated by perennial herbs.During this period,semi-shrub plants appeared in the community.In the late stage of abandoned cultivation succession,the plant communities were mainly mixed with perennial herbs and shrubs.The number of species in the community increased gradually with the succession stage of abandoned farming.(2)The physical and chemical properties of the soil under different abandonment stages in alpine meadows are significantly different.The soil moisture showed an increasing trend with the change of the abandoned tillage succession stage,while the soil temperature showed the opposite trend,which gradually decreased with the change of the abandoned tillage succession stage.Soil organic carbon and total nitrogen increased gradually from the early stage to the late stage in the abandonment succession stage.Soil total phosphorus showed more obvious changes in topography,but decreased in different abandonment succession stages.(3)Habitat filtering test results of different plant functional traits at different succession stages are different.Plant height and specific leaf area,leaf carbon,nitrogen,and phosphorus on the habitat filtration test are the same,showing that the role of habitat filtration gradually decreases with the change of abandoned farming succession stage.The null hypothesis is close.(4)The PD index and pedigree structure of the community showed a certain regularity with the change of abandoned farming succession stage.From the early stage to the late stage of abandonment succession,the PD index gradually increased,and the degree of divergence of the pedigree structure of the population gradually decreased,from the divergence to near zero hypothesis.The relative index in the late succession period was close to 0,and the phylogenetic structure in the early and middle succession period diverged.No phylogenetic signal was detected in the six selected traits,indicating that the selected six traits were not significantly affected by species evolution in alpine meadow plant communities under different abandonment periods.Comprehensive environmental factors and plant functional traits,communitycomposition,and phylogenetic structure,found that the environmental factors that have the strongest effects on communities at different abandonment stages are soil moisture and light intensity,which play a major role in driving the plant community construction For the purpose of habitat filtration,the community structure in the late and mid-late stages of abandonment succession showed that the community was affected by neutral processes and similarity constraints.Therefore,in a comprehensive view,the construction process of the community is mainly affected by the deterministic process,and also limited by the neutral process and similarity.