A technique for determination of single leaf reflectance and transmittance in field studies

Abstract

Single leaf reflectance (ρ) and transmittance (τ) are important input variables to vegetative canopy reflectance models and need to be estimated simultaneously with field measurements. Our objective was to evaluate a technique for field measurements of ρ and τ that does not require an integrating sphere. Values of near-normal hemispherical ρ and τ of green leaves of common bean, maize, wheat, and senesced leaves of potato measured with an integrating sphere and a high resolution spectroradiometer were compared with estimates of ρ and τ derived from contrasting white and black backgrounds. Values of ρ and τ were determined from a relationship relating ρ and τ to reflectance from contrasting backgrounds using the hemispherical sensor head of the spectroradiometer and with leaves placed on a 0.6 m × 0.6 m white/black panel. Derivation of ρ and τ involved estimating infinite reflectance (R ∞) and then calculating ρ and τ. The technique produced good estimates of ρ and τ compared to the integrating sphere-derived measurements of ρ and τ. Based on these results, it was concluded that the radiometer used to measure canopy reflectance can be used to measure ρ and τ in the field.