Lichens dominate a significant part of the Earth's land surface, and are valuable bioindicators of various environmental changes. In the northern hemisphere, the largest lichen biomass is in the woodlands and heathlands of the boreal zone and in tundra. Despite the global coverage of lichens, there has been only limited research on their spectral properties in the context of remote sensing of the environment. In this paper, we report spectral properties of 12 common boreal lichen species. Measurements of reflectance spectra were made in laboratory conditions with a standard spectrometer (350–2500 nm) and a novel mobile hyperspectral camera (400–1000 nm) which was used in a multiangular setting. Our results show that interspecific differences in reflectance spectra were the most pronounced in the ultraviolet and visible spectral range, and that dry samples always had higher reflectance than fresh (moist) samples in the shortwave infrared region. All study species had higher reflectance in the backward scattering direction compared to nadir or forward scattering directions. Our results also reveal, for the first time, that there is large intraspecific variation in reflectance of lichen species. This emphasizes the importance of measuring several replicates of each species when analyzing lichen spectra. In addition, we used the data in a spectral clustering analysis to study the spectral similarity between samples and species, and how these similarities could be linked to different physical traits or phylogenetic closeness of the species. Overall, our results suggest that spectra of some lichen species with large ground coverage can be used for species identification from high spatial resolution remote sensing imagery. On the other hand, for lichen species growing as small assemblages, mobile hyperspectral cameras may offer a solution for in-situ species identification. The spectral library collected in this study is available in the SPECCHIO Spectral Information System.

中文翻译：

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常见北方地衣物种的光谱分析


地衣占地球陆地表面的很大一部分，是各种环境变化的宝贵生物指标。在北半球，最大的地衣生物量位于北方地区的林地和荒地以及苔原。尽管地衣覆盖全球，但在环境遥感背景下对其光谱特性的研究仍然有限。在本文中，我们报告了 12 种常见北方地衣物种的光谱特性。反射光谱的测量是在实验室条件下使用标准光谱仪（350-2500 nm）和用于多角度设置的新型移动高光谱相机（400-1000 nm）进行的。我们的结果表明，反射光谱的种间差异在紫外和可见光谱范围内最为明显，并且干燥样品在短波红外区域总是比新鲜（潮湿）样品具有更高的反射率。与最低点或前向散射方向相比，所有研究物种在后向散射方向上具有更高的反射率。我们的结果还首次表明，地衣物种的反射率存在较大的种内差异。这强调了在分析地衣光谱时测量每个物种的多个重复的重要性。此外，我们使用光谱聚类分析中的数据来研究样本和物种之间的光谱相似性，以及这些相似性如何与物种的不同物理特征或系统发育密切性联系起来。总的来说，我们的结果表明，一些地面覆盖范围大的地衣物种的光谱可用于高空间分辨率遥感图像的物种识别。 另一方面，对于以小组合形式生长的地衣物种，移动高光谱相机可以为原位物种识别提供解决方案。本研究中收集的光谱库可在 SPECCHIO 光谱信息系统中获取。