The collection and preprocessing of this dataset has 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 bark reflectance spectra of ten boreal and temperate tree species. We measured hemispherical-directional reflectance factors (HDRF) of stem bark samples. The data were measured using a Specim IQ imaging spectrometer attached to a tree mounting setup. The imaging spectrometer operates in the visible and near-infrared wavelength region (400–1000 nm). The measurements were made in the Greater Helsinki area in Finland, and in Järvselja in Estonia. We measured 20 trees per species, accounting to a total of 200 unique stem bark samples. One sample refers to a hyperspectral reflectance image taken of a single tree stem. The 200 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 from May to August 2020. All measurements were made under natural illumination conditions and the images were taken in perpendicular view-angle to the tree stem. The dataset includes two tabular files that contain: 1) the mean reflectance spectrum for each of the ten common boreal and temperate tree species (calculated from the 20 samples per species), and 2) all 200 reflectance spectra (20 per tree species). The sampled species were: Scots pine (Pinus sylvestris L.), Norway spruce (Picea abies (L.) Karst), silver birch (Betula pendula Roth), grey alder (Alnus incana (L.) Moench), black alder (Alnus glutinosa (L.) Gaertn.), English oak (Quercus robur L.), European aspen (Populus tremula L.), European ash (Fraxinus excelsior L.), Norway maple (Acer platanoides L.), and littleleaf linden (Tilia cordata Mill.).
The two spreadsheets are organized as follows: first three rows that start with hashtag (#) contain comments for citing, first column "tree_species" (Pinus_sylvestris, Picea_abies, Betula_pendula...) indicates the tree species, 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 data in file "mean_tree_species_stem_bark_reflectance_spectra_Juola_et_al_2021.csv" is the same as what can be found in Version 1. We only changed the first row's naming to make it clearer.
If you use this dataset, please cite Juola et al. [1,2]:
 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
 Juola J., Hovi A., Rautiainen M., 2022. A dataset of stem bark reflectance spectra for boreal and temperate tree species. Mendeley Data, V2, doi: 10.17632/pwfxgzz5fj.2