Simulation of solar radiation absorption in vegetation canopies

A solar radiation canopy absorption model, including multiple scattering effects, was developed and tested for a lodgepole pine (Pinus contorta) canopy. Reflectance above the canopy, spectral transmittance to the ground layer, and geometric and spectral measurements of canopy elements were made. Relatively large differentials occurred in spectral absorption by canopy layers, especially in the photosynthetically active region, as a function of solar zenith angle. In addition, the proportion of total global irradiance absorbed by individual layers varied greatly as a function of solar zenith angle. However, absorption by the entire canopy system remained relatively constant.