Estimation of Forest Biomass from Estar Image Data

Image data from L-band airborne radiometer measurements over conifer forest stands in southern Virginia USA have shown a strong sensitivity to biomass and a weaker sensitivity to soil moisture. The data, was obtained by the horizontally polarized synthetic aperture radiometer, ESTAR, deployed aboard a NASA P3 aircraft. The data was acquired in July, August and November of 1999. The imaged region, which is owned by International Paper Company, consists of even aged loblolly pine stands of approximately one to two kilometers on a side. The stands range in biomass from 20 to 200 tons/hectare and are located on mostly flat ground. To understand the dependence of brightness temperature on biomass and soil moisture, a passive discrete scatterer model of the forest has been employed. Soil moisture and tree geometry measurements, made at the time of the over-flights, provide input data for the forest model. The model results agree with the measurements to within experimental error. The results of the measurements and the modeling indicate that L-band brightness temperature is sensitive to forest biomass. However, for stands of smaller biomass, the emission from the ground has an increasing role.