长白山木本植物叶片氮磷含量的海拔梯度格局及影响因子

Changes in leaf nitrogen and phosphorus stoichiometry of woody plants along an altitudinal gradient in Changbai Mountain, China

叶片是植物进行光合作用的器官,研究叶片氮(N)、磷(P)含量和氮磷比(N:P)在地理和气候梯度上的变异规律有着重要的意义。该研究沿着长白山海拔梯度设置了14块样地,测定了48种木本植物431份叶片样品的N、P含量和N:P,以研究气候、植物功能型、谱系对叶片N、P含量以及N:P的相对影响大小,探讨叶N、P化学计量特征在海拔梯度上的变化机制。结果表明,叶片N含量、N:P随海拔的升高而降低,与气温正相关,与降水量负相关,叶片P含量与海拔没有显著相关性。植物功能型是叶片N、P含量变异的重要影响因子,灌木物种的叶N含量显著高于乔木,两者的叶片P含量、N:P差异不显著;阔叶、落叶物种的N、P含量和N:P分别显著高于针叶、常绿物种。气候对叶片N、P含量和N:P的作用显著,但解释力不高(1.50%–2.98%)。系统发育关系是叶片N、P含量和N:P海拔格局形成的最主要因素,解释了30.36%–54.38%的变异,远大于气候的解释力。海拔梯度上的气候和物种组成变化对叶性状没有明显的协同作用。

Aims Leaf is the organ of plant photosynthesis, and it is important to understand the drivers for the variations of leaf nitrogen（N） and phosphorus（P） stoichiometry along geographical and climatic gradients. Here we aimed to explore： 1） the changes in leaf nitrogen（N） and phosphorus（P） stoichiometry of woody plants along an altitudinal gradient in Changbai Mountain, and 2） the relative contribution of climate, plant characteristics, and phylogeny to the changes in leaf N, P concentration and N：P. Methods We measured leaf N and P concentration, and N：P of 48 woody species in 14 plots along an altitudinal gradient in Changbai Mountain. General linear models（GLMs） and variation partitioning analyses were used to explain leaf N and P stoichiometry with parameters related to plant functional groups, climate and phylogenetic groups. Important findings 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. More comparative studies between altitudinal and latitudinal gradients are needed to better understand the drivers of the changes in leaf stoichiometry along an environmental gradient.