Tartu Observatory, EE2444 Tõravere, ESTONIA
Markov properties of stand geometry are incorporated into an analytical multispectral canopy reflectance model. The correlation of leaf positions in adjacent layers significantly influences the gap probability in a stand and, consequently, the canopy reflectance (CR) and its angular distribution. The sensitivity analysis demonstrated that the effect is the greatest on the angular distribution of multiply scattered radiation. Validation of the new CR model that considers the Markov stand geometry demonstrated an improved agreement between model calculations and measured directional reflectance distribution of NIR reflectance for barley and soybean stands. As a consequence, inversion of the new model in the NIR spectral region and in two spectral bands simultaneously allowed to estimate the leaf area index of a stand significantly better than the Nilson-Kuusk model which assumes a Poisson stand geometry.