In recent years, there has been an increasing interest in the use of r
adar data for observations of forest ecosystems. In particular, it was
shown that the intensity of SAR images at L band was proportional to
the forest aboveground biomass. More recently, the analysis of NASA/JP
L SAR data over the Landes forest (south-west France) revealed strong
correlation between P-band backscatter and biomass of pine trees and r
elated characteristics (tree age, height, diameter). Also, similar rel
ations have been obtained on two different forests (maritime pine at L
andes forest, France, and loblolly pine at Duke forest, U.S.A.). This
paper presents a step further in the understanding of the observations
, using theoretical modelling applied to calibrated SAR data to explai
n the radar backscatter from the forest canopy under study. The study
is presented at P band, which was found to be an optimal frequency ban
d for forest observations. It was found that the HH return is physical
ly related to both trunk and crown biomass, whereas VV and particularl
y HV returns are linked to crown biomass. Through allometric equations
, relations between radar backscatter intensities and most of the fore
st characteristics can thus be explained. The validated model has been
used in a next step to simulate a diversity of forest and observation
conditions. The results have been used for a preliminary assessment o
f the possibility of inverting SAR data into forest biomass.