片段化森林中檵木幼苗种内叶经济性状变异及其驱动因子

在异质性生境中，种内功能性状变异有助于植物对环境的适应，进而影响种群更新、群落构建和生态系统过程。探讨了种内叶经济性状的变异及受生境异质性的塑造情况。以千岛湖片段化生境中的常见种檵木（Loropetalum chinense）的幼苗为研究对象，测定了200株檵木幼苗个体水平的7个叶经济性状（比叶面积SLA、叶全碳量C、叶全氮量N等）及其对应的生境因子（郁闭度、土壤全碳量、土壤全氮量等），采用相关性检验、主成分分析和线性混合效应模型等方法探讨片段化森林中檵木幼苗的种内叶经济性状变异及生境异质性对该变异的驱动作用。结果显示：（1） 在7个叶经济性状所构成的21对相关性分析中，有12对显著相关。经主成分分析降维后，主成分1（PC1）占性状总变异的43.02%，主要与比叶面积、叶绿素浓度、叶全氮量呈正相关，与叶干物质质量分数和叶碳氮比呈负相关，体现了檵木的种内叶经济谱，可反映叶片的最大光合效率。（2）片段化对生境条件和叶经济性状均有影响。岛屿森林群落的郁闭度显著低于大陆。相对于大陆，岛屿中的檵木幼苗趋向于更小的PC1值（缓慢投资-收益策略）；大岛边缘较大岛内部偏向于更小的PC1值。（3）生境因子中，郁闭度对PC1具有显著正效应。研究表明，片段化生境中的檵木在幼苗阶段存在叶经济谱，生境片段化可通过影响生境条件进而改变檵木幼苗的叶经济性状。随着生境片段化程度的加剧，檵木幼苗的叶经济性状逐渐向缓慢投资-收益策略靠拢。

The driving factors of intraspecific leaf economic traits variations of Loropetalum chinense seedlings in fragmented forest

Intraspecific trait variations contribute to the adaptability of plant to the heterogeneous environments,which affect population regeneration,community assembly and ecosystem processes.This study aimed to explore the intraspecific variations of leaf economic traits and how it was shaped by habitat heterogeneity in fragmented forest.We measured seven leaf economic traits (i.e.specific leaf area (SLA),leaf total carbon content (C),leaf total nitrogen content (N),etc.) of seedlings (n=200) of a common native shrub species,Loropetalum chinense,in the Thousand Island Lake (TIL),as well as in site habitat conditions (i.e.canopy closure,soil total carbon content,soil total nitrogen content,etc.) of each seedling.We then performed the correlation test,principal component analysis,linear mixed effects model and so on to examine the variability of leaf traits and underlying environmental drivers.The results are as follows: (1) 12 of the 21 correlations composed of seven leaf economic traits are significant.Principal component analysis (PCA) showed that PC1 explains 43.02% of the total trait variations,which is positively correlated with SLA,N and chlorophyll concentration (Chl),and negatively correlated with leaf dry matter content (LDMC) and leaf carbon nitrogen ratio (C∶N),indicating an intraspecific economics spectrum of L.chinense seedlings that reflects maximum photosynthetic capacity. (2) Habitat fragmentation alters the environmental conditions and leaf economic traits of L.chinense seedlings.Specifically,canopy closure is significantly lower on islands than in mainland.On the other hand,leaf traits of L.chinense seedlings on islands are with lower PC1 value (i.e.the 'slow' end of leaf economics spectrum) than seedlings in mainland.Within islands,leaf traits of L.chinense seedlings at the edge of large island are with lower PC1 value compared to seedlings at the interior of large island.(3) The environmental influences on intraspecific leaf economic traits of L.chinense are mainly manifested as a significant positive effect of canopy closure on PC1.This study shows that leaf economics spectrum exists at the growth stage of L.chinense seedlings in fragmented habitats.Moreover,habitat fragmentation can affect intraspecific leaf economic traits of L.chinense by altering habitat conditions.Habitat fragmentation initiates the shift of leaf economic traits of L.chinense seedlings towards a slower resource-use strategy.