MODELED ANALYSIS OF THE BIOPHYSICAL NATURE OF SPECTRAL SHIFTS AND COMPARISON WITH INFORMATION-CONTENT OF BROAD BANDS

Spectral shifts characterized by the wavelength lambda(i) of the inflexion point in the red-edge region (670-780 nm) are analyzed using model simulations. Leaf optical properties are computed with the PROSPECT model, canopy reflectance with the SAIL model, and atmospheric effects with the 5S model. The information provided by the high spectral resolution index (lambda(i)) appears to be equivalent to that obtained from the red and near-infrared broad band reflectances at leaf level. This is not true at canopy level: lambda(i) is very sensitive to leaf area index and chlorophyll concentration and, when observed from space sensors, it minimizes the effects of atmosphere and soil background optical properties. Moreover, lambda(i) could be a pertinent indicator of canopy photosynthetic capacity. But its small dynamic range requires further studies in which sensor noise has to be considered, depending on the method of lambda(i) computation.