SPACEBORNE APPLICATIONS OF P-BAND IMAGING RADARS FOR MEASURING FORESTBIOMASS

In three sites of boreal and temperate forests, P band HH, HV, and VV polarization data combined estimate total aboveground dry woody biomas s within 12 to 27% of the values derived from allometric equations, de pending on forest complexity. Biomass estimates derived from HV-polari zation data only are 2 to 14% less accurate. When the radar operates a t circular polarization, the errors exceed 100% over flooded forests, wet or damaged trees and sparse open tall forests because double-bounc e reflections of the radar signals yield radar signatures similar to t hat of tall and massive forests, Circular polarizations, which minimiz e the effect of Faraday rotation in spaceborne applications, are there fore of limited use for measuring forest biomass. In the tropical rain forest of Manu, in Peru, where forest biomass ranges from 4 kg m(-2) in young forest succession up to 50 kg m(-2) in old, undisturbed flood plain stands, the P band horizontal and vertical polarization data com bined separate biomass classes in good agreement with forest inventory estimates. The worldwide need for large scale, updated, biomass estim ates, achieved with a uniformly applied method, justifies a more in-de pth exploration of multi-polarization long wavelength imaging radar ap plications for tropical forests inventories.