Addressing the Effects of Canopy Structure on the Remote Sensing of Foliar Chemistry of a 3-Dimensional, Radiometrically Porous Surface

Airborne and spaceborne imaging spectroscopy applied to measuring foliar chemistry has received considerable attention in the literature. Typically, results are based on data measuring all the reflective components that make up a given pixel. This introduces confounding variables that cannot be easily modeled. Spectral unmixing methods yield estimates of the percentage endmember coverage in each pixel. This methodology fails to provide spectra representing variations in these specific components and thus is not as accurate for inferring chemistry. We report on the integration of airborne LiDAR data with high resolution imaging spectroscopy. We compared laboratory-based leaf-level pigment modeling with results from airborne data. In this comparison two airborne datasets were generated; one representing spectra composed of all reflective elements within a forested plot, and a second representing the top of the dominant/codominant canopy. Empirical modeling indicated that there is an influence on the spectral reflectance recorded over a defined area from the lower canopy levels. This influence did not, however, add to our understanding of forest biology and structure.