Phylogenetic Negative Density Dependence On Tree Mortality In A Deciduous Broad-leaved Forest In Baotianman National Nature Reserve

Conspecific density dependence effect is well detected in some large-scale tropical and subtropical forests plots.It has been examined that density dependence was a prevalent factor for trees' death in some temperate forest plots.However,there were few density-dependence studies in transition between temperate and subtropical zone.there were no similar studies reported among phylogenetic closely related species from deciduous broad-leaved forests in temperate-subtropical ecological transition zone.It is important to discuss ecological community process that whether density dependence regulates most of plant species.To determine the contributions of density dependence to spatial pattern and dynamics of live and dead trees in subtropical summer green broad-leaved forest,pair-correlation function g(r)was employed to examine whether the intensity of aggregation decreases with increasing DBH classes in the Baotianman Nature Reserve.Based on the two census date in 2009 and 2014 in a 1 hm2 in deciduous broad-leaf forest dynamic plot was established in 2009 of Baotianman National Nature Reserve were divided into three parts as saplings(DBH<5cm),juveniles(5cm ? DBH<10cm),adult trees(10cm?DBH),Data in the 1-ha plot were divided into two spatial scales and three growth stages to compare phylogenetic structures at different scales in the Baotianman National Nature Reserve.We found that,phylogenetic density dependence regulated phylogenetic structure at smaller sizes(10 m×10 m?20 m×20 m?25 m×25 m),NRI and NTI decreased with increasing spatial and growth scales.The results showed that:(1)The number of individuals with DBH?1 cm,The average annual mortality and recruitment rate of all species is 4.65%and 0.27%,respectively.(2)these tree species were found to exhibit density dependent by using spatial pattern analysis Our findings indicate that density dependence is a prevalent factor for spatial distribution pattern in Baotianman Nature Reserve.It provides support for the notion of Janzen-Connell hypotheses.(3)phylogenetic density dependence regulated phylogenetic structure the deciduous broad-leaved forest in the Baotianman National Nature Reserve;phylodiversity dependence is related sample scales;(4)most tree species survival negative correlated with neighbor conspecific basal area or abundance were found by using GLM in different neighborhood size.(5)We found that 5 m and 7.5 m size most tree species survival correlated with phylogenetic diversity by using GLMM analysis.These studies suggest that tree mortality were found to exhibit density dependent,phylogenetic diversity was responsible for tree mortality when tree density was high in 5 m neighborhood size,But,with the increase of the neighborhood size niche differentiation plays a main role.