THE EFFECTS OF CHANGES IN FOREST BIOMASS ON RADAR BACKSCATTER FROM TREE CANOPIES

We validated a canopy backscatter model for loblolly pine forest stand s at the Duke Forest, North Carolina, by comparing the observed and mo delled SAR backscatter from the stands. Given the SAR backscatter data calibration uncertainty, the model made good predictions of C-HH, C-H V, L-HH, L-HV, L-VV, P-HH, and P-HV backscatter for most of 25 stands studied. The model overestimated C-VV backscatter for several stands, and largely overestimated P-VV backscatter for most of the stands. Usi ng the collected SAR backscatter and ground data, and the backscatter model, we studied the influences of changes in biomass on SAR backscat ter as a function of radar frequency and polarization, and evaluated t he feasibility of deriving the biomass from the backscatter. This stud y showed that C-HH, C-HV, C-VV, L-VV, and P-VV SAR backscatter may be insensitive to the biomass change. L-HH, L-HV, P-HH, and P-HV SAR back scatter changed more than 5 dB as the biomass varied. This study also showed that the L-HH and P-HH backscatter or L-HV and P-HV backscatter may be used to develop algorithms to retrieve trunk biomass or canopy biomass of the loblolly pine forests.