Effects Of Environmental Conditions On The Leaf Traits Variations In Five Species Of Carpinus In Maolan Karst Forest

Differentiation in functional traits among closely related species and their relationships with the environment is an important topic of community ecology.Herein,focused on species in the genus Carpinus in the Karst Forest of Maolan National Nature Reserve,the transect survey method were conducted at nine sites,and the leaves of 293 Carpinus plants,which belongs to five species,namely Carpinus tschonoskii,C.polyneura,C.tsaiana,C.pubescens and C.rupestris,were sampled.In th lab,eight leaf traits,including leaf thickness(TH),leaf area(LA),specific leaf area(SLA),leaf dry-matter content(LDMC),leaf carbon content(C),leaf nitrogen content(N)and leaf phosphorus content(P)and the carbon-nitrogen ratio(C:N),were measured.The DBH(diameter at breast height)of the sampled plants were measured in field,as well as the topographical and soil conditions.Furthermore,soils samples were drawn in site whenever possible,and the total carbon(TC),total nitrogen(TN),total phosphorous(TP)and total calcium(TCa)were measured in lab.The phylogenetic tree of the five Carpinus species was constructed using ITS sequence from the NCBI database.Mantel test was adopted to estimate the relationship between leaf traits differentiation and phylogenetic distance.Pearson correlation coefficient and principal component analysis(PCA)were adopted to estimate the relationships between leaf traits.Generalized linear mixed-effects model was adopted to investigate the effects of environment on leaf traits.The results are as below:(1)There was no correlation between leaf traits and phylogenetic distance,which implies that leaf traits of these species were not constrained by their recent evolutionary history.(2)At both the genus and species levels,morphological traits,such as LA,SLA and LT,showed the greatest variances,whereas leaf elements,such as C and N,show the least.Further,most leaf traits showed larger interspecific than intraspecific differences,implies divergence between species in leaf traits.(3)At both the genus and species levels,a large number of correlations were detected between leaf traits,and PCA commonly showed the principal component one(PC1)of leaf traits was positively related to SLA,N and P,and negatively related to LDMC and C:N,supports the presence of a leaf economics spectrum,and suggests the variation in resource-use strategies.(4)At both the genus and species levels,topography and soil nutrients both played important roles in shaping the leaf traits.For example,SLA,N and the PC1 of leaf traits declined,while LDMC and C:N increased,with the increase of elevation;the PC1 of leaf traits also increased,while LDMC decreased,with the increase in the principal component two(represents soil TP)of soil nutrients.The findings suggest Carpinus plants adopt their resource-use strategies according to environmental conditions,as the environment resources declined,the leaf traits shifted towards more conserved resource-use strategies.This study contributes to the understandings of functional trait differentiation among closely related species in the karst forests,as well as karst forest plant strategies in coping with environmental heterogeneities,which sheds light on the biodiversity maintenance mechanisms in karst forests,and provides theoretical support for the conservation of karst forest biodiversity.