Species Diversity Pattern And Maintenance Mechanism Of Mixed Evergreen Deciduous Broad-leaved Forest In Qizimei Mountains Of Southwestern Hubei

Objective:Species diversity is a direct reflection of biodiversity,and the maintenance mechanism of species diversity is the core content of community ecology research.The evergreen deciduous broad-leaved mixed forest in southwest Hubei is located in the core area of"Eastern Sichuan-West Hubei Endemic Phenomenon Center",one of the three unique phenomena of seed plants in China.Exploring the forest species diversity pattern in the region and revealing the formation and maintenance mechanisms behind it have important theoretical value for forest biological diversity protection.Methods:Based on the 6hm~2 sample plot of the National Forest Ecosystem Observation and research station of Qizimei Mountains National Nature Reserve in Southwest Hubei Province,on the basis of vegetation survey,topographic factor measurement and functional character sampling analysis,this study systematically studied the species abundance distribution pattern,species diversity character pattern,functional trait variation,functional diversity character pattern and structure,and explored the mechanism of maintaining species diversity in Qizimei Mountainsevergreen deciduous broad-leaved mixed forest.Results:(1)From the perspective of the abundance pattern of each life form species,the rare species increase with the increase of the scale and show a higher proportion.Compared with evergreen tree species,the number of deciduous tree species at each sampling scale is higher,and the diversity index is higher,but the number of individuals is relatively small.When the sampling scale is small,the statistical model fits well with the niche model.As the scale gradually expands,the neutral process explains the species abundance pattern more than the niche process;the deciduous tree species abundance pattern and the formation mechanism is closer to the abundance pattern and formation mechanism of all tree species in the plot than the evergreen tree species.(2)The 6hm~2 plot was divided into 5 habitats by multiple regression trees,representing 5 clusters.Altitude,slope,and convexity have certain effects on species composition and distribution,among which the altitude factor is more significant.The difference in topography between habitats directly affects the differentiation of the biomass and species diversity of clusters.The clusters?standing tree on the convex slope in the middle slope position have the highest density and average chest height section area;The shannon-winener index increases with habitat altitude shows a downward trend;clusters III and?simpson indice are lower,reflecting the lower uniformity of dominant species in the clusters;The pielou uniformity index is significantly different among the 5 clusters,and has an upward trend with the increase of habitat altitude.(3)The variation of leaf area and leaf dry weight among species is larger.The main sources of LA,LDW and SLA variation are interspecies variation,while the main sources of LDMC and WD variation are intraspecies variation.On the whole,interspecific variation contributes slightly more to the variation of traits than intraspecific variation.LA,LDW,and SLA trait values gradually increased with the increase of habitat altitude,while LDMC and WD tended to decrease with the increase of habitat altitude.The cluster level functional richness index decreased with the increase of habitat altitude,and the plots included in the middle and upper slope habitats(cluster?and cluster?)had lower functional richness,but the cluster level had higher functional richness and lower functional uniformity;cluster V of the convex slope on the middle slope shows lower functional richness and higher functional uniformity.The functional trait structure changes from aggregation to divergence,and the relationship changes from close to distant as the altitude of the cluster increases.Conclusion:The evergreen deciduous broad-leaved mixed forest in Qizimei Mountain is a zonal forest with high species richness.The maintenance of species diversity depends to some extent on the higher habitat heterogeneity of the local community.The formation mechanisms of the abundance pattern of deciduous and evergreen tree species are different;the ecological processes of the abundance pattern of the dominant species are different at different sampling scales.The altitude has a strong explanatory power on species diversity patterns,which significantly affects the species composition and functional strategies of the community.Intraspecific variation has a certain degree of contribution to trait variation,which reduces the filtering of species by biotic and abiotic factors,thereby promoting species coexistence,but the leading mechanisms for maintaining species diversity in different habitats are different.The mountain valley land and middle and lower slope position clusters are dominated by environmental filtering,while clusters on uphill slope are position significantly repelled by competition.