A dataset of stem reflectance spectra for standing dead Scots pine trees

The methods used to collect and preprocess this dataset have been reported in detail in Juola J., Hovi A., Rautiainen M., 2022. A spectral analysis of stem bark for boreal and temperate tree species. Ecology and Evolution. DOI:10.1002/ece3.8718 The dataset includes stem reflectance spectra of standing dead trees for the species of Scots pine (Pinus sylvestris L.). We measured hemispherical-directional reflectance factors (HDRF) of stem samples. The data were measured using a Specim IQ imaging spectrometer. The measurements were taken from the northern side of the stem at breast height (1.3 m), and the image acquisition distance was 20 cm. The imaging spectrometer operates in the visible and near-infrared wavelength region (400–1000 nm). The measurements were made in the municipality of Rovaniemi, Finland. We measured 13 standing dead Scots pine trees, accounting to a total of 13 unique stem samples. One sample refers to a hyperspectral reflectance image taken of a single standing dead tree stem (at 1.3 m height). The 13 mean spectral signatures (presented in this dataset) were calculated for each sample by averaging the HDRF values over all pixels per wavelength. The measurements were conducted in the beginning of August 2022. All measurements were made under diffuse illumination conditions and the images were taken in perpendicular view-angle to the standing stem. The dataset includes 1) one tabular file that contains all 13 mean reflectance spectra, and 2) a supportive document that has images of the individual standing dead trees and RGB visualizations of the measured hyperspectral reflectance images. The spreadsheet (.csv) is organized as follows: first two rows that start with hashtag (#) contain comments for citing, first column "tree_species" (standing_dead_tree_pinus_sylvestris) indicates the standing dead tree species, second column "id" (K1-K13) indicates the unique stem id's for which images can be found in the supportive document, and the subsequent columns "wl397.32"-"wl1003.58" indicate the measured HDRF value at that wavelength. The encoding of the csv file is UTF-8. The supportive document (.pdf) contains the dataset description given here, but also images of the standing dead trees taken in the forest and their corresponding RGB visualizations of the measured hyperspectral reflectance images. The Diameter at Breast Height (DBH) are given for each stem in the figure descriptions. If you use this dataset, please cite: Juola, J., Rautiainen, M., 2022. A dataset of standing dead tree stem reflectance spectra for Scots pine. Mendeley Data, V1, doi: 10.17632/8dvx3vvvk9.1 Funding: Academy of Finland (ARTISDIG, grant number: 348152) Acknowledgments: We thank Veli Juola and Erkki Tuovinen for assistance in the field campaign.本数据集的采集与预处理方法已详细发表于Juola J.、Hovi A.、Rautiainen M. 2022年的《A spectral analysis of stem bark for boreal and temperate tree species》（《Ecology and Evolution》，DOI:10.1002/ece3.8718）。本数据集涵盖欧洲赤松（Pinus sylvestris L.）枯立木的茎秆反射光谱。我们对茎秆样本的半球方向反射因子（hemispherical-directional reflectance factors, HDRF）进行了测量，所用设备为Specim IQ成像光谱仪。 测量点位设置于树干胸高（1.3 m）的北侧，图像采集距离为20 cm。该成像光谱仪的工作波段覆盖可见光与近红外区间（400–1000 nm），全部测量工作均在芬兰罗瓦涅米市开展。 本次共完成13株枯立欧洲赤松的测量，对应13份独立茎秆样本。每份样本对应单株枯立木胸高位置的高光谱反射图像。本数据集提供的13份平均光谱特征，通过对每个波长下所有像素的HDRF值取平均计算得到。测量工作于2022年8月初开展，所有测量均在漫射光照条件下进行，图像采集视角与枯立树干保持垂直。 本数据集包含两部分内容：1）一份包含全部13份平均反射光谱的表格文件；2）一份辅助文档，内含单株枯立木的实拍图像与对应高光谱反射图像的RGB可视化结果。 该CSV格式表格的结构如下：前两行以井号（#）开头的行包含引用注释；第一列"tree_species"（取值为standing_dead_tree_pinus_sylvestris）用于标注枯立木物种，第二列"id"（取值为K1-K13）为唯一茎秆编号，辅助文档中可查询对应编号的图像；后续列"wl397.32"至"wl1003.58"分别标注对应波长下测得的HDRF值。该CSV文件的编码格式为UTF-8。 辅助PDF文档除包含本数据集的说明文本外，还收录了森林中枯立木的实拍照片，以及对应高光谱反射图像的RGB可视化结果。每份茎秆的胸高直径（Diameter at Breast Height, DBH）信息已在图注中给出。 若使用本数据集，请引用以下文献：Juola J., Rautiainen M., 2022. 《A dataset of standing dead tree stem reflectance spectra for Scots pine》. Mendeley Data, V1, doi: 10.17632/8dvx3vvvk9.1 资助信息：本研究受芬兰科学院（ARTISDIG项目，资助编号：348152）资助。 致谢：感谢Veli Juola与Erkki Tuovinen在野外测量工作中提供的协助。