In accordance with the distorted Born approximation, a wave approach is developed for the volume attenuation and backscattering coefficients associated with the foliage layer in forests at L- and P-bands. Since the foliage layer is not the dominant layer in forest modelling at longer wavelengths, the orientations of scatterers are assumed to be uniformly distributed. As a result, the ensemble average electric polarizability of scatterers becomes isotropic, generating both volume attenuation and backscattering independent of polarization. It is shown that multiple scattering efTects due to both near and far scatterers are insignificant. It is demonstrated that the total leaf biomass, the mean leaf volume, leaf shape and the dielectric constant are key parameters for the model.