AN ATTEMPT AT SPECTRAL DETECTION OF PHENOLOGICAL CHANGES OF BOREAL VEGETATION (15th Symposium on Polar Biology)

Ground truth information for remote sensing to distinguish boreal and arctic vegetation species, biomass and phenology is needed in global scale climate change research activities. A boom-mounted 4-band spectroradiometer was installed to measure seasonal radiance patterns in green (560 nm), red (660 nm), near-infrared (830 nm) and mid-infrared (1650 nm) spectral bands from boreal vegetation canopies over the 1992 growing season in northernmost Finland, Utsjoki. The radiometer on top the rotating boom which was held horizontally about 4 m high above the ground looked downward on four plant plots in turn every 15 min. Plant growth stages were observed every week for each plot. Seven-band field spectra (560, 660, 830, 1100, 1200, 1650, 2200 nm spectral bands) were also taken there for autumn tint and leaf coloring of the major plant species at the end of August, 1992. Initial analyses indicated that the "wetness" index (near- to mid-infrared reflectance ratio) and red band reflectance could be potential indices to evaluate the autumn leaf coloring and withering of dwarf and mountain birch tree canopies