Response Of Leaf Traits Of Common Broad-leaved Woody Plants To Environmental Factors On The Eastern Tibetan Plateau

Leaf is one of the main plant organs for energy conversion and material accumulation.Leaf traits are closely related to plant‘s resource acquisition and utilization,thereby reflecting largely the adaptation strategies of plants to the environments.However,in terms of leaf trait variations at the regional scale,most previous studies have focused only on the influence of single environmental factors rather than multiple ones,and(or)considered it only at interspecies level but ignored at intraspecies level,both often resulting in a failure evaluation of leaf variation patterns.In addition,woody plants are important in structuring forest communities or even land ecosystem.Thus,a study on the relationship between woody plants‘ leaf trait variations and multiple environmental factors at both inter-and intra-species level is of great significance in predicting the environmental graidients in forest communities and the adaptation of woody plants to future climate changes.The study were set up on the eastern Tibetan Plateau,in which leaves of 666 populations from 332 common broad-leaved woody species were collected at 47 sites with significant altitudinal gradient,ranging from 1750 m to 3920 m a.s.l.For each population,14 leaf traits were measured,including eight leaf morphology traits and six leaf stomatal traits.We investigated the extent of leaf trait variation in this area,as well as the response of leaf traits to single and multiple environmental(altitudinal and climate)factors at both intra-and inter-species levels.The results showed:1.Overall,leaf area,petiole length,leaf area per petiole length,leaf width and leaf length had largest coefficients of variation.These five traits represent the size of individual leaf,indicating a high adaptative varaition in leaf size traits.2.Most leaf traits except stomatal density were significantly associated with altitude,in which leaf length,leaf width and leaf area decreased with increasing altitude both in both intra-and inter-specific analysis,suggesting that smaller leaves were selected to adapt to the high-altitude environments.3.Inter-species analysis showed that altitudinal variation in leaf thickness and specific leaf area were non-linear,in which the variation was nonsignificant until more than an altitudinal threshold(i.e.leaf thickness increased significantly from 2700 m a.s.l.but specific leaf area decreased significantly from 2600 m a.s.l.).4.For the relationship between altitude and stomatal length or stomatal width,an opposite result was found between intra-and inter-species analysis,in which the relationship was significantly negative at the inter-species level,but positive at the intra-species level.5.Climate factors were the important drivers of leaf trait variation because they explained 3%-29% of leaf trait variations.Based on the results of stepwise regression,factors related to air temperature/precipitation had the highest/lowest interpretation degree of leaf trait variation,while sunlight time could explain the variation of most leaf traits.6.the significant relationships between leaf traits and environmental(altitude and climatic)factors at intra-species level were far less than at inter-species levels.The reason may be the coordinated variation and trade-off between plant traits,which make the variation of intra-species traits relatively small,and thus weaken the intra-species correlation between leaf traits and environmental factors.