Solar zenith angle effects on vegetation indices in tallgrass prairie

The examination of the effects of solar zenith angle is based on computations of spectral vegetation indices (VIs) computed from spectral reflectance factors. The indices are examined in terms of biomass and LAI, and low-density canopies show no change in the low VI values during the day. The spectral VIs appear to measure the instantaneous, projected, and illuminated LAI canopy fraction relative to the illuminated substrate.