Use of narrow-band spectra to estimate the fraction of absorbed photosynthetically active radiation

Abstract

We propose a novel approach for using high-spectral resolution imagers to estimate the fraction of photosynthetically active radiation adsorbed, 𝑓ₐₚₐᵣ, by vegetated land surfaces. In comparison to approaches using broad-band vegetation indices, the proposed method appears to be relatively insensitive to the reflectance of nonphotosynthetically active material beneath the canopy, such as leaf litter or soil. The method is based on a relationship between the second derivative of the reflectance vs wavelength function for terrestrial vegetation and 𝑓ₐₚₐᵣ. The relationship can be defined by the second derivatives in either of two windows, one in the visible region centered at 0.69 μm, another in the near-infrared region centered at 0.74 μm.