Spectral estimation of grass canopy variables

Regression analysis of in situ spectral reflectance of a blue grama grass canopy sampled with approximately equal amounts of standing live and standing dead vegetation has identified spectral regions between 0.35 and 0.80 μm where the total wet biomass, total dry biomass, and leaf water content can be spectrally estimated. The amount of total wet or dry biomass was best estimated in the 0.35 to 0.44 μm region of the spectrum. This resulted from a combination of a relatively greater carotenoid than chlorophyll retention in the recent standing dead vegetation and of carotenoid and chlorophyll pigments present in the photosynthetically active or live vegetation. The leaf water content, highly related to the amount of photosynthetically active vegetation present, was best estimated in the ∼0.46 to 0.50, 0.63 to 0.69, and 0.74 to 0.80 μm regions. This resulted from strong chlorophyll absorption in the ∼0.46 to 0.50 and 0.63 to 0.69 μm regions and the high reflectance of living vegetation in the 0.74 to 0.80 μm region.