Monitoring of soil moisture and vegetation water content variations in boreal forest from C-band SAR data

The response of ERS-2 SAR to changes in soil and forest canopy moisture is investigated at a boreal forest test region in Finland. An inversion approach to estimate moisture characteristics from SAR data is applied. The method requires that a priori information on forest biomass (stem volume) and soil type distribution is available. The inversion technique provides estimates that are here, in addition to backscattering signatures, directly compared with daily in situ moisture values. The results indicate that time-series of C-band radar observations can be used for the monitoring of boreal forest moisture variations. Especially, the detection of the driest and the wettest conditions on mineral soil sites appears to be a feasible application even for single channel radar. The obtained SAR-based soil moisture estimates showed an RMSE level of 6% units against the in situ data for pine-dominated mineral soil sites.