A COMPARISON OF SPECTRAL REFLECTANCE PROPERTIES AT THE NEEDLE, BRANCH, AND CANOPY LEVEL FOR SELECTED CONIFER SPECIES

The optical-reflective radiative transfer characteristics of three conifer species [Norway spruce (Picea abies), red pine (Pinus resinosa), and white pine (Pinus strobus)] and one broadleaf, deciduous species [sugar maple (Acer saccharum)] were measured and compared at the leaf, twig, branch and canopy level. The magnitude of reflectance throughout the visible and near infrared wavelength region was found to decrease dramatically for the conifer species as scene complexity increased from the needle, to the branch, to the canopy level. Comparison of the conifer data with equivalent data obtained for sugar maple served to validate quantitatively that conifer canopies, in general, are more absorptive than their deciduous counterparts, particularly in the near infrared region. These data emphasize the role of canopy constituents, such as needles, twigs, branches, bark, and understory material, in altering the reflectance characteristics of the overall "scene," and may be valuable in developing improved radiative transfer models for forest canopies.