Proß Tobias, Bruelheide Helge, Haider Sylvia
Institute of Biology, Geobotany and Botanical Garden, Martin Luther University Halle-Wittenberg, Halle, Saxony-Anhalt, Germany.
German Centre for Integrative Biodiversity Research (iDiv), Leipzig, Saxony, Germany.
Ecology. 2025 Jul;106(7):e70160. doi: 10.1002/ecy.70160.
Leaf traits are important indicators of ecosystem functions. Trait values can vary widely between species, and a considerable amount of variation also occurs within species. However, within-individual variation is often neglected due to the limitations of traditional measurement tools. Many leaf trait values respond to light availability, which, in turn, is affected by the surrounding vegetation. Additionally, there is a strong within-individual light gradient, especially in tree canopies. In the BEF-China (Biodiversity-Ecosystem Functioning China) subtropical forest plantation, we analyzed how leaf trait values respond to light availability and neighboring tree species richness at the within-individual level. We sampled across the vertical light gradient formed by neighboring trees planted at varying diversity levels from monocultures to 24-species mixtures. We closely paired the leaf samples with sensor-based measurements of light availability. We used visible and near-infrared spectroscopy (spectral range: 350-2500 nm) to predict 14 leaf traits across 4981 leaves from 15 native tree species. Using a key feature of spectroscopy-deriving multiple leaf traits from a single spectral measurement of a sample-we assessed all traits simultaneously at the leaf level. We investigated whether an individual tree's direct neighbor or the surrounding tree species richness had a stronger influence on the light-trait relationship. Most trait values responded to light availability, though this response differed between deciduous and evergreen species. We found that tree species richness and a tree's direct neighbor could modify the light-trait relationship at the individual level. In some instances, a focal tree's direct neighbor influenced its leaf trait values more than the tree species richness in its local neighborhood. Specifically, in conspecific tree pairs of evergreens, specific leaf area and leaf nitrogen displayed a stronger response to changing light conditions. This response to light availability suggests a mechanism for avoiding within-species competition that is observable at the within-individual level. Our results show that biodiversity influences ecosystem functions through its effects on within-individual leaf trait variation. The fact that the interplay between light availability, biodiversity, and leaf traits can be observed within-individual trees highlights the importance of within-individual leaf trait variation in biodiversity research.
叶片性状是生态系统功能的重要指标。性状值在不同物种间差异很大，且在同一物种内也存在相当大的变异。然而，由于传统测量工具的局限性，个体内的变异常常被忽视。许多叶片性状值对光照可用性有响应，而光照可用性又受周围植被的影响。此外，个体内存在很强的光照梯度，尤其是在树冠层。在“生物多样性与生态系统功能中国”（BEF-China）亚热带人工林中，我们分析了在个体水平上叶片性状值如何响应光照可用性和邻近树种丰富度。我们在由从单一栽培到24种混交林等不同多样性水平种植的邻近树木形成的垂直光照梯度上进行采样。我们将叶片样本与基于传感器的光照可用性测量紧密配对。我们使用可见和近红外光谱（光谱范围：350 - 2500 nm）来预测来自15种本土树种的4981片叶子的14种叶片性状。利用光谱学的一个关键特性——从样本的单次光谱测量中推导多个叶片性状——我们在叶片水平上同时评估所有性状。我们研究了个体树木的直接邻体或周围树种丰富度对光-性状关系的影响是否更强。大多数性状值对光照可用性有响应，尽管落叶树种和常绿树种的这种响应有所不同。我们发现树种丰富度和树木的直接邻体可以在个体水平上改变光-性状关系。在某些情况下，一棵焦点树的直接邻体对其叶片性状值的影响比其局部邻域内的树种丰富度更大。具体而言，在常绿树种的同种树木对中，比叶面积和叶片氮含量对变化的光照条件表现出更强的响应。这种对光照可用性的响应表明了一种在个体水平上可观察到的避免种内竞争的机制。我们的结果表明，生物多样性通过其对个体内叶片性状变异的影响来影响生态系统功能。光照可用性、生物多样性和叶片性状之间的相互作用能够在个体树木内部被观察到，这一事实凸显了个体内叶片性状变异在生物多样性研究中的重要性。
