不同坡向川西亚高山林木竞争与叶片表型可塑性的关系研究

表型可塑性是植物生长响应外界环境变化的重要表现形式，体现了植物个体在环境胁迫下的适合度。但是关于植物表型可塑性的驱动机制仍然存在很多争议。为了探讨植物表型可塑性的影响因素，以四川省阿坝藏族羌族自治州位于同一海拔梯度但坡向相反的天然次生林为研究对象，分析了不同坡向竞争强度与10种树木叶片功能性状表型可塑性的关系的差异。研究发现：(1)研究样地中阴坡水分和养分资源优于阳坡；(2)阴坡上林木平均种内和种间竞争强度高于阳坡，阴坡上林木种内竞争强度随着树木个体大小的增加而显著性减少，阳坡上林木种内竞争强度却随着个体大小的增加而增加；(3)阴坡上叶片表型可塑性高于阳坡，表型可塑性随着个体大小的增加而增加，在阳坡上却随着个体大小增加而降低。这些结果表明阴坡上水分等资源环境条件优于阳坡，林木生长受到环境资源限制较少。在林木生长过程中，较高的竞争强度引起的资源重叠加剧，尤其是种内竞争强度的变化，从而导致了阴坡上较高的叶片表型可塑性。因为较高的竞争强度，随着林木个体大小的增加，树木需要更高的可塑性赢得竞争优势来获取更多的资源支持生长。但是在阳坡上，资源相对缺乏，环境资源对树木生长的限制降低了叶片表型的可塑...

Relationships between competition intensity and leaf phenotypic plasticity of woody plants in subalpine forests on different slope directions

Phenotypic plasticity is an indicator of the responses of plant growth and development to environmental changes, which reflects the fitness of plant individuals under environmental stress. However, the driving mechanism of plant phenotypic plasticity is still controversial. To explore the impacts of environmental conditions and competition on the phenotypic plasticity of leaf traits in trees, we surveyed two secondary forests with different slope directions in the Ngawa (Aba) Tibetan and Qiang Autonomous Prefecture in western Sichuan, China and analyzed the difference in the relationship between competition intensity and phenotypic plasticity of 10 tree species leaf functional traits between shade and sunny slopes. Results show that:(1) water and nutrient availabilities were greater on shade slope than those on sunny slope. (2) Mean intraspecific and interspecific competitions of tree species on shade slope were higher than those on sunny slope; intraspecific competition intensity decreased with the increases of individual tree size on shade slope, but it increased along with the increase of individual size on sunny slope. (3) The leaf traits include specific leaf area (SLA), leaf carbon content (C), leaf nitrogen content (N), leaf phosphorus content (P), leaf kalium content (K), leaf carbon-phosphorus ratio (CPR), leaf carbon-nitrogen ratio (CNR), and leaf nitrogen-phosphorus ratio (NPR). Phenotypic plasticity of all eight measured leaf traits on shade slope was higher than on sunny slope. Phenotypic plasticity of leaf traits increased with the increase of individual tree size on shade slope, but decreased with the increase of individual size on sunny slope. These findings suggest that the environmental resources of community on shade slope were greater than on sunny slope. The growth of forest trees was less restricted by the availability of environmental resources on shade slope, where higher competition intensity led to the intensification of resource overlap, especially the high intraspecific competition intensity, ultimately resulted in the higher phenotypic plasticity of leaf traits on shade slope. Because of higher competition intensity, with the increase of individual size, trees need higher phenotypic plasticity to gain competitive advantage and obtain more resources to support growth. However, because resources were relatively poor, the limitation of the availability of environmental resources reduced to the lower phenotypic plasticity of leave traits on sunny slope. Due to the limitation of the availability of environmental resources, with the increase of individual size, trees were more likely to suffer resource constraints. Therefore, phenotypic plasticity of leaf traits on sunny slope decreased with the increase of tree individual size. To summary, our study demonstrated that leaf phenotypic plasticity was mainly affected by competition intensity on the shade slope, while it was mainly limited by the availability of environmental resources on the sunny slope.