1. Trait values affect how plants function, with consequences that propagate through scales of ecological organization to affect ecosystem function. However, the pathway connecting trait expression to ecosystem function is complicated by feedbacks: trait expression may vary within species in response to community diversity, and trait expression also determines a community's functional diversity. The predictability and consequences of interactions between trait expression and community diversity are poorly understood, particularly in forest ecosystems.
2. Here we quantify the extent to which light access—which past studies suggest affects trait expression and differs as a result of interactions among plants—differs consistently with community diversity and explains intraspecific trait variation in trees. In a common garden, trees of five angiosperm and seven gymnosperm species were planted to form 37 communities ranging widely in species and functional diversity whereby confounding environmental variation was minimized. We sampled leaves of each species to characterize intraspecific variation within and among communities in three traits—leaf size, specific leaf area and nitrogen concentration—and estimated each leaf's access to light.
3. We found that light access explained a substantial portion of trait variation within all species, species tended to receive less light in more diverse communities and effects of community diversity on trait expression tended to be mediated by light.
4. Synthesis . This study shows that community diversity affects leaf trait plasticity in young trees through its effects on light availability. Moreover, trait responses across angiosperms and gymnosperms were remarkably similar, showing that shared biophysical constraints overwhelm divergent evolutionary histories. Together, these results illustrate how leaf trait expression responds to, and may subsequently shape, diversity in young tree communities in largely predictable ways via resource‐based interactions, with consequences that may scale from individuals to ecosystems.

中文翻译：

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光在功能和系统发育多样性的树木混合物中介导了群落多样性与性状可塑性之间的关系。

1. 特质价值影响植物的功能，其后果通过生态组织的规模传播，从而影响生态系统的功能。但是，反馈将特质表达与生态系统功能联系起来的途径变得复杂：特质表达可能会因物种的多样性而在物种内发生变化，而特质表达也决定了群落的功能多样性。特质表达与社区多样性之间相互作用的可预测性和后果知之甚少，尤其是在森林生态系统中。
2. 在这里，我们对光的获取程度进行了量化（以往的研究表明，这种影响会影响性状表达，并且由于植物之间的相互作用而有所不同）与社区多样性一致，并解释了树内种内性状的变异。在一个公共花园中，种植了5种被子植物和7种裸子植物的树木，形成了37个群落，物种和功能多样性广泛，从而使混杂的环境变化最小化。我们对每种物种的叶片进行了采样，以表征群落内部和群落之间三个特征（叶片尺寸，比叶面积和氮浓度）的种内变异，并估计了每片叶片的光照。
3. 我们发现光的传播解释了所有物种内性状变异的很大一部分，物种在更多样化的社区中倾向于接受较少的光，并且社区多样性对性状表达的影响倾向于由光介导。
4. 综合。这项研究表明，社区多样性通过影响光利用率来影响幼树的叶片性状可塑性。此外，被子植物和裸子植物的性状反应非常相似，表明共同的生物物理限制淹没了不同的进化历史。这些结果共同说明了叶片性状表达如何通过基于资源的交互作用以很大程度上可预见的方式对幼树群落的多样性做出反应，并随后塑造了多样性，其后果可能从个人扩展到生态系统。