Effects Of Plant Size And Leaf Age On The Leaf Traits And The Relationships Between Traits In Pinus Koraiensis

Investigating the effects of plant size and leaf age on leaf traits is important for understanding the utilization and distribution of resources in the process of plant growth.Pinus koraiensis is one of the constructive species in the Chinese boreal forest.In this study,we measured the leaf dry mass per area(LMA),leaf density(LD),leaf volume per area(LVA),leaf dry matter content(LDMC),mass-based nitrogen content(N),mass-based phosphorus content(P),and cross-sectional morphological and anatomical traits of four leaf age classes of 67 Pinus koraiensis of different sizes.We aimed to explore the effects of plant size and leaf age on leaf traits and on the relationships of them,the effects of environmental factors on traits,and the anatomical characteristics of LMA,LD and LVA.The results showed that:(1)Vascular tissue traits such as xylem and phloem were the most variable traits.Leaf trait variation was mainly influenced by plant size and leaf age.Tree height showed significant linear positive correlations with LMA,LD,LVA,LDMC,morphological and anatomical area traits.Tree height showed no significant correlation with N and a significant negative correlation with P.Fraction of vascular tissues and transfusion tissues showed the trend of increasing and then decreasing with increasing tree height.LMA,LD,LDMC,phloem and vascular bundles traits showed significant increasing trend with increasing leaf age,while N and P showed significant decreasing trend.In addition,the variation of LDMC,N,P,cross-sectional morphological and anatomical area traits with leaf age were also influenced by tree height.Compared with individual developmental factors,environmental variables had less influence on leaf traits.(2)N-LMA and N-LDMC showed significant negative correlations,and the absolute value of the slope tended to decrease with increasing tree height;N-P showed significant positive correlations,and the slope tended to increase with increasing tree height.LDMC-LMA showed a significant positive correlation among different leaf age groups,and the slope tended to decrease with the increase of leaf age.LD-LMA showed a significant positive correlation among different tree height groups and leaf age groups,and there were differences in slope.LVA-LMA showed a significant positive correlation in some height groups and all leaf age groups,and there was no difference in slope.LMA was positively correlated with cross-sectional anatomical and area traits(except resin canal area).Cross-sectional anatomical traits(except vascular tissue traits)were similarly related to LMA and to LVA.LD was positively correlated with phloem and vascular bundle traits.Overall,plant size is an important driver of variation in leaf traits,and the hydraulic function is likely to be maximum in medium-sized trees.in the early stage of individual development and leaf life,the needle traits tend to be "low investment-quick returns" resource strategy.In contrast,in the late stage of individual development and leaf life,they tend to be "high investment-slow returns" resource strategy.This study reflects the optimization of resource allocation of Pinus koraiensis between its own traits according to its functional needs in individual life history and leaf life history.