Study On Seedling Functional Traits In Badagongshan Evergreen And Deciduous Broad-leaved Mixed Forest,Central China

Trait-based community dynamic is a focus in plant ecology.However,size-dependent changes of plant functional traits and variations in functional groups are still unknown,and how these changes affect seedling survival may potentially influence forest regeneration and species coexistence in forest communities.Based on 25 ha Badagongshan(BDGS)dynamic plot in Hunan province,we selected 24 common tree species and collected 826 seedlings.Leaf area,leaf biomass,stem biomass,specific leaf area(SLA),stem specific density(SSD),leaf thickness(LT),petiole length(PL),leaf carbon content(LCC),leaf nitrogen content(LNC),leaf phosphorus content(LPC)and leaf chlorophyll(Chl)were measured according to seedling height Combined with a 6-year continuous seedling monitoring,relationship between functional traits and seedling survival were analyzed by utilizing Generalized Linear Mixed Models(GLMMs).Variations of functional traits in different size and functional groups were analyzed by principal component analysis(PCA),one-way ANOVA and Fisher LSD.The main results are as following:(1)There were some significant variation trends in traits among different height.SLA and C/N decreased while SSD,PL,N/P and Chl increased with the growth of seedling.(2)No significance of SLA and remarkable differences of LT,Chl and N/P were detected between canopy,understory and shrub.Chl and N/P decreased at first then increased and LT decreased as the increase of vertical stratum height.(3)Evergreen trees had larger LT and Chl while deciduous trees had larger PL.Other traits showed no obvious pattern in different life forms.(4)Individual size and its interaction with SSD,Chl and LNC meant a lot in seedling survival.Evergreen and deciduous seedlings were more influenced by physiological traits while LPC and Chl acted inversely.In summary,seedlings adjusted functional traits as the surrounding environment changed and different functional groups would adopt different adaptation strategies.The functional traits in early life stage was not stable enough to predict community dynamics and plant size dependence should be concerned.Moreover,there was a nitrogen limitation in seedling growth in Badagongshan(BDGS)subtropical evergreen and deciduous broad-leaved mixed forest and this limitation became weaker with the growth of seedling.