The dataset includes understory reflectance spectra in hyperspectral resolution (350–2300 nm), fractional cover of understory, and forest inventory variables from different types of boreal forest stands. The measurements were made in situ in 36 forest stands in Hyytiälä, Finland (61°50’N, 24°17’E) during 2018 and 2019 peak growing seasons (day of year 165–190) under diffuse illumination conditions. Each study stand represents a forest site (fertility) type: OMT (herb-rich), MT (mesic), VT (sub-xeric), or CT (xeric), based on Cajander’s theory of forest types . The fractional cover of understory was estimated for each stand from nadir view photographs of vegetation quadrats using the following classes: green vegetation (%-green), plant litter (%-litter), and lichen (%-lichen). Spectral data of the understory were measured in nadir view using ASD FieldSpec4 spectrometer in tandem with bare fiber sensor optics and a pistol grip. The spectral data are hemispherical-conical reflectance factors (HCRF), calculated from the ratios of measurement signals from the understory and white reference panel, with dark currents readily subtracted. A detailed description of the methodology is provided by Forsström et al. .
Measurement data from altogether 36 study stands are organized in spread sheets as follows: the first spread sheet includes the description of the variables, the second spread sheet include both the forest inventory data and fractional cover data, and the rest of the spread sheets (numbered 1-36) include the spectral data. Spectral data are further organized in columns, so that the first column is a list of measured wavelengths and columns 2-16 include the corresponding HCRFs from 15 sampling positions (~0.8 m apart along a transect line) per study stand. HCRFs in wavelength regions of high noise are assigned with NaN values for clarity.
We thank Ville Ranta and Daniel Schraik for collaboration. Data collection and preparation was supported by the Academy of Finland [BOREALITY, grant number 286390; and DIMEBO, grant number 3323004]; and by the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme [grant agreement No 771049]. The article reflects only the authors’ view and the Agency is not responsible for any use that may be made of the information it contains.
If you use this dataset, please cite Forsström et al. [2,3].
 Cajander, A.K., 1926. The theory of forest types. Acta Forestalia Fennica, 29(3), article id 7193. doi:10.14214/aff.7193.
 Forsström, P.R., Juola, J., Rautiainen, M. 2021. Relationships between understory spectra and fractional cover in northern European boreal forests. Agricultural and Forest Meteorology. doi:10.1016/j.agrformet.2021.108604
 Forsström, P.R., Juola, J., Hovi, A., Rautiainen, M., 2021. Dataset of understory reflectance spectra and fractional cover in a boreal forest area in Finland. Mendeley Data, V1, doi:10.17632/2g9nkcdj53.1
|Koska saatavilla||17 elok. 2021|
|Ajallinen kattavuus||2018 - 2019|