A model for radiative transfer in heterogeneous three-dimensional canopies

A model, dubbed TRIM, for the interaction of electromagnetic radiation with inhomogeneous vegetation canopies is presented. It is based on the four flux theory for homogeneous canopies. The canopy is assumed to consist of ellipsoidal subcanopies located on the ground at periodic intervals. The model is inverted with field measured data for reflectance from corn canopies in the near infrared region. It is shown that TRIM correctly identifies the architecture of the canopy (homogeneous or row canopy, percentage of ground cover) and gives a good estimate of leaf area index.