Study On Leaf N,P Stoichiometry Of Evergreen Broad-leaved Forest In Successtional Stages In Tiantong National Forest Park

In this thesis,the leaf ecological stoichiometry of dominant and common species, soil nutrients and their correlation with leaf traits in various successional stages of the subtropical evergreen broadleaved forest(EBLF)were studied in,Tiantong National Forest Park.The findings are followed:1.The spatial patterns of leaf N,P stoichiometry between various successional satges in EBLF were rather consistent.Leaf N,P contents and N:P increased with the succession progress.The leaf N or P content can not be effective indicator to reflect successional stage,but the trends of leaf N,P and N:P are consistant with that of successional stages.The seasonal patterns of leaf N,P contents of various successional stages in EBLF are that the leaf N,P contents increased to the maximum value in spring,but decreased in summer,and then increased gradually in winter.2.In the earlier successional stage,e.g.the secondary shrub,leaf N:P in the community is the lowest,but leaf N:P increased in the later stages,which indicated that plant species' growth were limited with soil nitrogen supply in the earlier stage. but the ratio of leaf N:P is moe than 16 which indicated that plant species' growth were limited by soil phosphorus supply in the later successional stages.The N:P in the new leaf is obviously less than that of the old leaf,which implied that new leaf was more subject to be limited by nitrogen than old leaf.3.The soil nutrient of total N and P increased with successional progress which was consistent with that trends of leaf N,P contents.Soil N:P was far less than that of leaf and shows no obvious pattern in successional stages.The pattern of soil NO₃^--N variance in the successional stages is similar with leaf N and P contents and N:P ratio.There are no obvious pattern for soil NH₄⁺-N content.Soil nutrient and N:P ratio decreased with the soil depth.Soil inorganic nitrogen increased in the spring,then reached the peak in summer,but decreased again in autumn and winter.While soil total N and P contents show obvious opposite pattern compared with that of soil inorganic nitrogen.4.There are good fitness brtween leaf nutrient and photosynthesis in succession stages.Leaf mass area(LMA)decreased gradually with successional progress.LMA is negatively correlated with leaf nutrient and photosynthesis.Leaf N and P contents are positively correlated with photosynthesis.But there is no strong correlation etween Leaf N:P ratio and photosynthesis which demonstrated that leaf N:P ratio is just a week impact factor in leaf economic spectrum.Leaf traits of various successional stages in EBLF had the tendency of coevolution,which demonstrated the coevolution of leaf traits in small scale whether they were in earlier or later successional stage.