Towards accounting for leaf clumping within radiative transfer modeling

This work is an attempt to relate the gap fraction or extinction coefficient to some biophysical variables responsible of leaf clumping within canopies. Analysis study made on 3D numerical canopies showed in fact that clumping effect is mainly governed by the following variables: relative leaf size, plant density and relative position of leaves. First parameterization of clumping index as function of view zenith angle and relative leaf-stem distance is presented in this paper. This parameterization was then applied to estimate some biophysical variables such Leaf area index and LAI and Average Leaf Angle ALA using hemispherical photographs