Ground-based digital camera (RGB), spectroscopy, and pigment data from Toolik Vegetation Grid, Toolik Lake, Alaska

Ground-based spectroscopy measurements acquired systematically within the Toolik Vegetation Grid in the 2016 growing season. All data were collected in a subset of 1 x 1 m long-term monitoring plots representing three distinct vegetation communities three times representing early, peak and late season. Spectral data were acquired using a GER 1500 field spectrometer (350-1050 nm; 512 bands, spectral resolution 3 nm, spectral sampling 1.5 nm, and 8! field of view). Spectra were collected under clear weather conditions at the highest solar zenith angle between 10:00 and 14:00 local time. Data were collected at nadir approximately 1 m off the ground resulting in a Ground Instantaneous Field of View (GIFOV) of approximately 15 cm in diameter. Nine point measurements of upwelling radiance (Lup) were collected in each plot and averaged to characterize the spectral variability and to reduce noise. Downwelling radiance (Ldown) was measured as the reflectance from a white Spectralon© plate. Surface reflectance (R) was processed as Lup/Ldown x 100 (0-100%). Reflectance spectra were preprocessed with a Savitzky-Golay smoothing filter (n = 11) and subset to 400-985 nm to remove sensor noise at the edges of the radiometer detector. Digital camera data were acquired using a consumer-grade camera (Panasonic DM3 LMX, Japan) approximately 1 m off the ground with a white frame for registration of off nadir images. For detailed definitions of the RGB indices see metadata.docx. Leaves and stems of the dominant vascular species in a subset of the sampled plots were collected at early, peak, and late season for chlorophyll and carotenoid analysis.Samples were placed in porous tea bags and preserved in a silica gel desiccant in an opaque container for up to 3 months until pigment extraction (Esteban et al. 2009, doi:10.1007/s11120-009-9468-5). Each sample was homogenized by grinding with a mortar and pestle. Approximately 1.00 mg (+/- 0.05 mg) of homogenized sample was placed into a vial with 2 ml of dimethylformamide (DMF). Vials were then wrapped in aluminum foil to eliminate any degradation of pigments due to UV light and stored in a fridge (4C) for 24 hrs. Samples were measured into a cuvette prior to spectrophotometric analysis. Bulk pigments concentrations were then estimated using a spectrophotometer measuring absorption at 646.8, 663.8 and 480 nm (Porra et al. 1989, doi:10.1016/S0005-2728(89)80347-0) . Absorbance (A) values at specific wavelengths were transformed into µg/mg concentrations of chlorophyll a, Chla, chlorophyll b, Chlb, total chlorophyll, Chl, carotenoids, Car (for equations see metadata.docx). Pigment concentration was calculated as the average concentration of the dominant species in each plot. mean_"pigment" represents the mean of all biomass from each vegetation community and sd_"pigment" represents the standard deviation of each vegetation community