Williams Laura J, Kovach Kyle R, Guzmán Q J Antonio, Stefanski Artur, Bermudez Raimundo, Butler Ethan E, Coq-Etchegaray Domitille, Glenn-Stone Catherine, Hajek Peter, Klama Johanna, Medlyn Belinda E, Messier Christian, Moradi Aboubakr, Paquette Alain, Park Maria H, Scherer-Lorenzen Michael, Townsend Philip A, Reich Peter B, Cavender-Bares Jeannine, Schuman Meredith C
Hawkesbury Institute for the Environment, Western Sydney University, Penrith, New South Wales, Australia.
Department of Forest Resources, University of Minnesota, St Paul, Minnesota, USA.
Ecology. 2025 Mar;106(3):e70032. doi: 10.1002/ecy.70032.
Greater tree diversity often increases forest productivity by increasing the fraction of light captured and the effectiveness of light use at the community scale. However, light may shape forest function not only as a source of energy or a cause of stress but also as a context cue: Plant photoreceptors can detect specific wavelengths of light, and plants use this information to assess their neighborhoods and adjust their patterns of growth and allocation. These cues have been well documented in laboratory studies, but little studied in diverse forests. Here, we examined how the spectral profile of light (350-2200 nm) transmitted through canopies differs among tree communities within three diversity experiments on two continents (200 plots each planted with one to 12 tree species, amounting to roughly 10,000 trees in total), laying the groundwork for expectations about how diversity in forests may shape light quality with consequences for forest function. We hypothesized-and found-that the species composition and diversity of tree canopies influenced transmittance in predictable ways. Canopy transmittance-in total and in spectral regions with known biological importance-principally declined with increasing leaf area per ground area (LAI) and, in turn, LAI was influenced by the species composition and diversity of communities. For a given LAI, broadleaved angiosperm canopies tended to transmit less light with lower red-to-far-red ratios than canopies of needle-leaved gymnosperms or angiosperm-gymnosperm mixtures. Variation among communities in the transmittance of individual leaves had a minor effect on canopy transmittance in the visible portion of the spectrum but contributed beyond this range along with differences in foliage arrangement. Transmittance through mixed species canopies often deviated from expectations based on monocultures, and this was only partly explained by diversity effects on LAI, suggesting that diversity effects on transmittance also arose through shifts in the arrangement and optical properties of foliage. We posit that differences in the spectral profile of light transmitted through diverse canopies serve as a pathway by which tree diversity affects some forest ecosystem functions.
更高的树木多样性通常会通过增加在群落尺度上捕获的光照比例和光利用效率来提高森林生产力。然而，光塑造森林功能的方式不仅是作为一种能量来源或压力源，还作为一种环境信号：植物光感受器可以检测特定波长的光，植物利用这些信息来评估其周边环境，并调整其生长和分配模式。这些信号在实验室研究中已有充分记录，但在多样化的森林中研究较少。在这里，我们在两大洲的三个多样性实验中（每个实验有200个样地，每个样地种植1至12个树种，总共约10000棵树），研究了透过树冠层的光的光谱特征（350 - 2200纳米）在不同树木群落之间的差异，为理解森林多样性如何塑造光质量以及对森林功能产生影响奠定了基础。我们假设并发现，树冠层的物种组成和多样性以可预测的方式影响透光率。总透光率以及在具有已知生物学重要性的光谱区域的透光率，主要随着单位地面面积叶面积（叶面积指数，LAI）的增加而下降，而叶面积指数又受群落的物种组成和多样性影响。对于给定的叶面积指数，阔叶被子植物树冠层往往比针叶裸子植物或被子植物 - 裸子植物混合树冠层透射更少的光，且红 - 远红比率更低。群落中单个叶片透光率的变化对光谱可见部分的树冠层透光率影响较小，但在该范围之外，与叶片排列差异一起对树冠层透光率有贡献。透过混合物种树冠层的透光率常常偏离基于单一栽培的预期，而这仅部分地由多样性对叶面积指数的影响来解释，这表明多样性对透光率的影响也通过叶片排列和光学特性的变化而产生。我们认为，透过不同树冠层的光的光谱特征差异是树木多样性影响某些森林生态系统功能的一条途径。
