  This report revisits the role of the extinction coefficient in radar
backscattering-based models for forest monitoring. A review of a number of
works dealing with this issue has revealed a diversity of extinction values
being unclear its dependence on the sensor frequency and the forest type. In
addition, a backscattering model directly derived from the RVoG formulation is
employed to analyse the saturation of backscattering level as a function of
vegetation height and the presence of a decreasing trend of backscatter beyond
the saturation point as suggested in previous works in the literature.
According to this analysis it seems reasonable to think that further research
specially focused on dedicated experimental measurements of the extinction
coefficient should be carried out.
