Key message

Leaf area index and species composition influence red-to-near-infrared and red-to-shortwave-infrared transmittance ratios of boreal and temperate forest canopies.

In this short communication paper, we present how the spectral composition of transmitted shortwave radiation (350–2200 nm) varies in boreal and temperate forests based on a detailed set of measurements conducted in Finland and Czechia. Our results show that within-stand variation in canopy transmittance is wavelength dependent, and is the largest for sparse forest stands. Increasing leaf area index (LAI) reduces the overall level of transmittance as well as red-to-near-infrared and red-to-shortwave-infrared transmittance ratios. Given the same LAI, these ratios are lower for broadleaved than for coniferous forests. These results demonstrate the importance of both LAI and forest type (broadleaved vs. coniferous) in determining light quality under forest canopies.

中文翻译：

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林冠层传播的短波辐射的光谱成分

关键信息

叶面积指数和物种组成会影响北方和温带森林冠层的红到近红外和红到短波红外透射比。

在这篇简短的交流论文中，我们基于在芬兰和捷克共和国进行的一系列详细测量，介绍了在寒带和温带森林中透射短波辐射（350-2200 nm）的光谱成分如何变化。我们的结果表明，林冠内透射率的林内变化取决于波长，并且对于稀疏森林林分来说是最大的。叶面积指数（LAI）的增加会降低总的透射率水平，并降低红到近红外和红到短波红外的透射比。给定相同的LAI，阔叶林的比率要比针叶林的比率低。这些结果表明，在确定林冠层下的光质量时，LAI和森林类型（阔叶与针叶林）都非常重要。