Submitted to: American Society for Photogrammetry and Remote Sensing Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: November 25, 2002
Publication Date: May 5, 2003
Citation: Walthall, C.L., Daughtry, C.S., Norman, J. The impact of corn leaf optical properties on image tone. In: Proceedings of American Society for Photogrammetry and Remote Sensing.
Remote sensing of plant canopy optical properties is being investigated as a tool for assessing plant condition, with particular emphasis on crop nitrogen status. Leaf optical properties, although different from canopy optical properties, are a major determinant of canopy reflectance. Leaf spectral reflectance and transmittance are influenced by physiological status via changes of pigment concentrations, internal leaf structure, and water content. An assessment of the variability of leaf optical properties within a single field and their impact on canopy reflectance would provide insight to the limits of our ability to remotely sense crop nitrogen status. This is conducted using a spatially dense sample from a single cornfield and a canopy reflectance simulation model. The results show that leaf spectral transmittance varies more than leaf spectral reflectance, and that visible wavelengths vary more than infrared wavelengths. Near infrared leaf transmittance and reflectance are shown to have greater impact on canopy reflectance than visible wavelengths. Large changes of leaf transmittance and reflectance are required before canopy reflectance is affected. Leaf reflectance changes appear to affect canopy reflectance more than changes of leaf transmittance and are most noticeable at higher foliage densities. The results have implications for remote sensing of plant chlorophyll and thus nitrogen status, and the use of imagery to "scale-up" hand-held chlorophyll meter readings from leaves of single plants to whole fields.