Functional Diversity And Stability Of Karst Woody Plant Communities As A Function Of Habitat Heterogeneit

The shallow and discontinuous soil and exposed bedrock in karst landforms of southwest China form the spatial heterogeneity of soil resources,which leads to uneven distribution of karst vegetation,the poor of community stability and resilience to disturbance.However,it is still unclear how the functional diversity,stability,and aboveground biomass of plant community variation under different habitat heterogeneity,which is crucial for maintaining the stability of karst plant community.Therefore,this study takes the typical karst forest in Pingba District of Anshun City as the research object,and sets 53 plots of 20 m × 20 m,and each plot is divided into 4subplots of 10 m ×10 m,a total of 212 subplots.Through the field community investigation and the indoor measurement of leaf functional traits,the functional diversity of the community was calculated based on six functional traits,including plant height(H),specific leaf weight(LMA),leaf carbon content(C),nitrogen content(N),phosphorus content(P),and potassium content(K);the functional redundancy index was calculated based on the Simpson index of species diversity and the Rao quadratic entropy index of functional diversity;the community stability was calculated based on species abundance and richness;the aboveground biomass of the community was calculated based on the H and DBH of the species using the existing biomass models in karst areas.The variation characteristics of functional diversity,functional redundancy,community stability,and aboveground biomass of woody plant communities under different habitat heterogeneity were analyzed.The impact of species diversity,functional diversity,and functional redundancy on community stability and the relationship between aboveground biomass and community stability were further explored.The main results are as follows:(1)The content and stoichiometric ratio of chemical elements in leaves of woody plant communities vary significantly with the increase of habitat heterogeneity and soil depth,as evidenced by a significant variation in leaf C content that decreases first and then increases with the increase in habitat heterogeneity,a significant variation in N/P ratio that increases first and then decreases with the increase in habitat heterogeneity,and a significant trend in N content and N/P ratio that increases with the increase in soil depth,the C/N ratio shows a significant downward trend as the soil depth increases;(2)The functional diversity of woody plant communities shows a significant trend of increasing first and then decreasing with the increase of habitat heterogeneity.When the intensity of habitat heterogeneity ranges from 1.227 to 1.462,woody plant communities maintain a high functional diversity.Among the microhabitat components,stone chinks,stone surfaces,and soil surfaces mainly affect functional diversity,and plant height of functional traits is the main functional trait indicator that affects functional diversity;(3)The functional redundancy index of woody plant communities showed a significant variation trend of first increasing and then decreasing with the increase of habitat heterogeneity,that is,the functional redundancy showed a significant variation trend of first decreasing and then increasing with the increase of habitat heterogeneity,and a significant decrease trend with the increase of rock exposure rate.The functional redundancy index showed significant positive correlation with the functional diversity of functional evenness,functional dispersion,functional divergence,Rao quadratic entropy,and the functional traits of plant height,the plant height is also the main functional trait index that affects the functional redundancy index;(4)The woody plant community is instability,the Euclidean distance from the stable point ranging from 0.2525 to 0.3596.The community stability increases significantly with the increase of soil depth.The species diversity index of Shannon Wiener,Simpson,Pielou has a significant negative correlation with community stability,and functional evenness in functional diversity index has a significant negative correlation with community stability,while the functional redundancy index has no significant negative correlation with community stability.Species diversity and functional diversity have a greater impact on community stability than functional redundancy,which is the main reason for affecting the stability of karst woody plant communities;(5)The aboveground biomass of woody plant communities increased significantly with the increase in soil depth and community stability.The species richness,functional richness,and functional dispersion in the diversity index showed a significant positive correlation with the aboveground biomass of the community.In conclusion,the stability of karst woody plant communities is weak,and community species play different ecological functions in maintaining community stability.The differences in functional traits of species lead to different ways of using resources and improving resource utilization efficiency,further reflecting that community species improve aboveground biomass and maintain stability of karst woody plant communities through niche complementation effects.