| Leaf is the main organ for a series of important ecological processes,such as carbon assimilation and water transport,and its traits variation and correlation are closely related to plant survival strategies.Among those functional traits,the ones related to light capture,water transport and gas exchange of leaves have attracted much attention,such as leaf economic traits,vein traits and stomatal traits.Studies on plant functional traits provide a reliable way for us to further understand and explore species coexistence,community dynamics and ecosystem functions.However,it is not clear how species shade tolerance,plant life history stage and soil fertility drive traits variation,and the effects of plant size,functional traits and environmental factors on plant growth rate also need to be further explored.In view of this,based on plant functional traits,plant growth rate and environmental factors,our study explored the variation,the correlation and main driving factors of plant functional traits,and analyzed the main driving factors of plant growth rate.The main results were as follows:(1)Based on four major distribution plots of mixed broadleaved-Korean pine(Pinus koraiensis)forest in northeast China,we measured the leaf economic traits,vein traits and soil fertility factors of five different shade tolerance tree species(including Populus davidiana;Betula platyphylla;Fraxinus mandshurica;Tilia amurensis;Acer mono),we explored the variation and correlation between economic traits and vein traits,and analyzed the effects of shade tolerance tree species and soil fertility factors on leaf traits.The results showed that shade tolerance of tree species drove the variation of leaf economic traits and vein traits,but the variation trend was different with different traits.For shade intolerance tree species,there was a decoupling relationship between the two groups of traits dimensions(p > 0.05).As shade tolerance of tree species increased,the correlation between the two groups of traits dimensions changed into a coupling relationship(p < 0.05),and the coupling relationship became stronger with the increase of shade tolerance.There were significant correlations among the economic traits group and the vein traits group,and part of traits between these two groups,but the interspecific correlation was stronger than the intraspecific correlation.The correlation between traits and soil fertility factors at the interspecific level was weaker than that at the intraspecific level,and the correlation between leaf dry matter content and the sum of main vein length and soil fertility factors was stronger than other traits.The main soil fertility factors driving the variation of traits were determined by traits;The correlation between trait plasticity and soil fertility factors at interspecific level was almost equal to that at intraspecific level,and soil carbon content was the main driving factor for trait plasticity variation.Our study suggests that taking shade tolerance of tree species into account in studies of trait variation,trade-offs,and responses to soil fertility can help better understand plant resource utilization strategies.(2)Based on leaf economic traits,stomatal traits and soil fertility factors of six major broad-leaved species in the mixed broadleaved-Korean pine forest in Liangshui Nature Reserve of Heilongjiang Province(including Betula platyphylla;Fraxinus mandshurica;Ulmus laciniata;Betula costata;Tilia amurensis;Acer mono),we investigated the effects of plant life history stages(including sapling;young tree and adult tree)and soil fertility on traits variation and correlation.The results showed that the economic traits and some stomatal traits of leaves varied significantly with the life history stage of plants,and the main factors affecting the traits variation changed with the life history stage.There were significant correlations among some traits,and the correlations among stomatal traits were stronger than economic traits in the three life history stages of plants,while the correlations among groups were stronger in young tree than in adult tree than in sapling.There was coupling relationship between economic and stomatal traits in sapling and young tree(p < 0.05),and decoupling relationship in adult tree(p > 0.05).In the whole life history stage,the correlation between traits and soil total P content was stronger than other soil fertility factors.In different life history stages,the correlation between traits and soil fertility factors depended on life history stage.In addition,there were differences in the main soil fertility factors of driving traits variation at different life history stages.For sapling and adult tree,soil p H was the main soil fertility factor affecting traits variation.For young tree,soil nitrogen content was the main factor affecting traits variation.The results indicate that adult plants have more conservative nutrient strategies than sapling and young tree,and it is suggested that in future studies,the effects of life history stages on the correlation among traits or traits and soil fertility factors should be emphasized in the application of some traits.(3)Based on plant diameter at breast height(DBH),growth rate,functional traits and environmental factors(including light density,soil nutrients and soil water content)in three different life history stages of six major broad-leaved species in the mixed broadleaved-Korean pine forest in Liangshui Nature Reserve of Heilongjiang Province,the main influencing factors of plant growth rate at different life history stages and intraspecific and interspecific levels were analyzed.The results showed that the functional traits and soil nutrient factors selected by the optimal structural equation model were different in different life history stages.In sapling and adult tree,soil nutrients and functional traits had direct effects on plant growth rate,and soil nutrients also had indirect effects on plant growth rate by influencing functional traits;For young tree,environmental factors tended to have indirect rather than direct effects on plant growth rate by influencing functional traits.Overall,the proportion of functional traits and environmental factors explaining plant growth rate in sapling and adult tree was higher than that in young tree.At the intraspecies level,the effects of DBH,functional traits and environmental factors on plant growth rate depended on tree species selection.The functional traits and soil nutrient factors selected by the optimal structural equation model of each tree species were different,and all factors had the greatest effect on the growth rate of Acer mono(0.667)and the least effect on Betula platyphylla(0.103).There were differences between the main factors affecting plant growth rate at interspecific level and intraspecific level,and the effect of factors on the growth rate of interspecific level was weaker than the average level of intraspecific.There were significant variations in plant functional traits between different negative tolerant tree species and different life history stages,and the main soil factors driving the variation of leaf functional traits depended on traits;The effects of plant size,functional traits and environmental factors on plant growth were influenced by life history stage and the level of intraspecific and interspecific studies. |
