MULTIVARIATE-ANALYSIS OF AVIRIS DATA FOR CANOPY BIOCHEMICAL ESTIMATION ALONG THE OREGON TRANSECT

High spectral resolution data from the Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) acquired over several forest stands in west-central Oregon were analyzed with respect to variations in forest canopy biochemical content (kg ha-1), foliar biochemical concentration (mg cm2 leaf area), and leaf area index (LAI). The Lowtran-7 atmospheric radiative transfer code was used to convert AVIRIS at-sensor radiance into reflectance factor The correlation of reflectance factor and first-difference AVIRIS spectra with total nitrogen (TN), lignin, starch, total chlorophyll content (kg ha-1), and LAI is presented. Correlogram structure in the 1200-2400 nm region is compared with the occurrence of known absorption features associated with organic molecular bonds which comprise foliar biochemical constituents. Regression equations relating the first-difference AVIRIS data to chemical variables and LAI were developed. The chlorophyll red edge spectral region was strongly related to LAI, canopy TN content, and canopy chlorophyll content. Generally good correspondence was found between wavelength selections for TN and lignin (concentration and content) and overtones of fundamental C-H and N-H absorptance features. The AVIRIS data were not significantly correlated with either starch concentration or starch content, although wavelength selections for starch were consistent with those made in previous laboratory-based studies.