The Effects Of Leaf Functional Traits And Diversity On Litterfall Production And Decomposition Across Climatic Gradient And Successional Stages Of Broadleaf Korean Pine Forest

In this study,we selected four typical areas(Changbai Mountain,Jiao He,Wu Ying and Sheng Shan)of broadleaf Korean pine forest and set up 51 plots according succession progress.This study mainly focused these following questions:(1)the changes in leaf nitrogen(N)and phosphorus(P)stoichiometry of woody plants along an altitudinal gradient in Changbai Mountain,and the relative contribution of climate,plant characteristics,and phylogeny to the changes in leaf N,P concentration and N:P;(2)the latitudinal and successional trends of leaf functional traits at the individual level and community level;(3)the effects of leaf functional traits and diversity on two important ecosystem functions(total annual litterfall production and litter decomposition)among successional stages and climatic gradient.The main results were summarized as fol ows:(1)Leaf N concentration and N:P decreased with altitude,and were positively correlated with mean annual temperature(MAT)but negatively correlated with mean annual precipitation(MAP).Leaf P concentration had no significant relationship with altitude.Leaf N,P concentration and N:P were significantly different among different plant functional groups.Leaf N concentration of shrubs was higher than that of trees,but leaf P concentration and N:P did not differ significantly between shrubs and trees.Leaf N,P concentration and N:P of broad-leaved plants were significantly higher than those of coniferous plants.Similarly,leaf N,P concentration and N:P of deciduous plants were significantly higher than those of evergreen plants.The effects of climate on leaf N,P concentration and N:P were significant but very weak,with MAT and MAP together explaining 1.50%-2.98%of the variations.Phylogenetic groups explained 30.36%-54.38%of the variations,suggesting the critical effect of phylogeny.Our study also showed that the synergistic effect of climate and species composition(phylogeny)on leaf N and P stoichiometry was neglectable,at least along the altitude gradient of Changbai Mountain.(2)At the individual level,leaf carbon(C)concentration,leaf P concentration and leaf C:N increased;leaf N:P and C:P decreased with the increasing latitude,whereas no clear latitudinal trends of specific leaf area(SLA)and leaf N concentration were found.At community level,as latitude increased,leaf C:P had no significant relationship;leaf C,leaf P,leaf C:N increased and SLA,leaf N,leaf N:P decreased significantly.The latitudinal pattern of leaf functional traits at community level was more obvious than that of the individual.SLA,leaf N concentration,leaf N:P increased firstly and then decreased during the successional process,mid-succession stage had the maximum value;leaf C:N decreased firstly and then increased,mid-succession stage had the minimum value;leaf P,leaf C,leaf C:P had no significant change among different successional stages.(3)Total annual litterfall production decreased with increasing latitude and had no significant change among different successional stages.Litterfall production increased with SLA,leafN,N:P,but decreased with leaf C,C:N,C:P,and had no significant relationship with leaf P.Three types diversity indices(species diversity,functional diversity and phylogenetic diversity)had positive effect on litterfall production.Our results showed that litterfall production was controled by climate,leaf functional traits and diversity together and the climate had the greatest effect,followed by plant functional traits and then was diversity.The "sample effect" is more important than "the complementarity effect".Litter decomposition coefficient k also had no significant change among different successional stages.And increased with leaf P,leaf C,but decreased with N:P,and had no significant relationship with SLA,leaf N,C:N,C:P.Litter initial moisture had important effect for litter decomposition rate.Only phylogenetic diversity had significantly positive relationship with k.Climate and litter quality had strong synergistic effect and litter quality may be more important than climate in this study.