中文摘要：

外来植物入侵严重威胁着当地生物多样性和生态系统功能，引发巨大经济损失，已成为日益严重的全球性问题。光是热带和亚热带森林生态系统植物生长最重要的限制性资源之一，对光的捕获和利用直接影响植物在自然生态系统中的生存和适合度。本研究以华南地区危害严重的入侵植物薇甘菊（Mikania micrantha）和飞机草（Chromolaena odorata）为研究对象，对比二者生长、生物量分配及叶片特征对光照强度变化的响应，从而验证假设：外来植物入侵力受有效光辐射的限制，光照是影响不同演替阶段林型具有不同可入侵性的重要原因之一。研究结果表明，3％一60％全光照下两种外来植物均可存活，并显示较灵活的生物量分配策略，可见其对光照具有广适性，为其广泛分布提供生态学基础。低光严重抑制了两种外来植物的生物量积累，这可能是导致演替后期季风林入侵现象少的主要原因之一。对比两种植物叶片特征对光照强度变化的响应，高光下薇甘菊SLA降低。LAR、LARMR减小，叶片变小变厚，有利于植株保持强光下的水分平衡；低光下薇甘菊增加SLA和LAR，叶片变薄变大，增大对光的截获面积，以实现对光强减弱的适应。相比薇甘菊，3种光照处理对飞机草的SLA、LAR、LARMR无显著影响。以上结果提示：（1）光照影响所在群落对外来植物入侵的抵抗力；（2）攀援植物薇甘菊较丛生型草本飞机草对变化的光环境在叶片水平上具有更高的形态可塑性，有效寻觅光资源。

英文摘要：

As an important component of global environmental change, the invasion of exotic species represents one of the most serious threats to native biodiversity and ecosystem function worldwide and causes huge economic losses. Light is one of the most important limiting resources for plant growth in subtropical and tropical forests, wherein the plant abilities of capturing and utilizing light becomes a determinant for their establishment and fitness. In this study, we compared plant growth, biomass allocation and leaf-level traits in response to variations in light intensity in Mikania micrantha and Chromolaena odorata, which have invaded many habitats in South China causing significant damage. We hypothesized that the invasion potential of exotic intensity may play an important species will be restricted by the effective optical radiation they can capture, and light role in determining the community resistance to invasion. Our results showed that the two exotic species both could survive under 3%--60% of full solar irradiance and display a relatively flexible biomass allocation strategy. It indicated that they have acclimated to a wide range of variation in light resources, which supplies ecological foundation for their widely spread. Low light significantly decreased the biomass accumulation of the two exotic species and might contribute to the low invasibility in monsoon evergreen broadleaf forest （MEBF） to plant invasions. In addition, we found that high light resulted in smaller and thicker leaves （low SLA, LAR and LARMR） in M. micrantha, which is advantageous to maintain the water balance under high light. When growing under low light conditions, M. micrantha increased its SLA and LAR. Its leaves turned to bigger and thinner, which is helpful to capture more light in adapting to the decreasing light. By contrast, C. odorata demonstrated no significant change in its leave-level traits across the light treatments. Collectively, the vine M. micrantha had higher morphological plasticity than herb C. odorata i