To explore the formation and maintenance mechanisms of the understory plant diversity,the ecological stoichiometric characteristics of leaves of understory trees,shrubs,herbs and vines and their relationship with phylogeny were studied by conventional and phylogenetic comparison methods in Maoershan subtropical evergreen broad-leaved forest,Guangxi.The results showed that the phylogenetic signals(Blomberg's K)of leaf stoichiometric characteristics ranged from 0.020 to 0.183.The contents of N and P and the phylogenetic signals of C/P,P/Ca and K/Ca in leaves were significant,indicating that phylogenetic conservation existed in the process of species diversification.The contents of C,N,K and Mg in leaves and most of stoichiometric ratios were significantly affected by life form.The contents of N,K and Mg in leaves of vines were the highest,while the contents of C,Mg,C/N and C/P in leaves of herb were the lowest,which indicated that there were differences in the requirement and proportion of nutrient elements in leaves of different life forms.The stable selection of the optimal ecological stoichiometric characteristic values of leaves of different life forms was the optimal evolutionary model,which indicated that plants of different life forms chose the optimal combination of leaf stoichiometric characteristics to adapt to themselves in the evolutionary process.In addition,there was a close correlation between the stoichiometric characteristics of leaves during evolution.Therefore,phylogenetic conservation of leaf ecological stoichiometric characteristics and optimal stable selection in the process of species diversification jointly promoted the formation and maintenance of understory plant diversity in subtropical evergreen broad-leaved forests.
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