Estimating Canopy Biochemistry through Imaging Spectrometry

Broad-band reflectance measurements of vegetation have been widely applied in the form of indexes based on the unique differential between chlorophyll absorption in the red wavelengths and reflectance in the near infrared region to aid in the assessment of carbon fixation/allocation patterns, nutrient availability and soil respiration.

Abstract

Broad-band reflectance measurements of vegetation have been widely applied in the form of indexes based on the unique differential between chlorophyll absorption in the red wavelengths and reflectance in the near infrared region. Background and atmospheric effects also have an influence on the measured signal and are only partially removed through ratioing of wavebands. High spectral resolution data acquired by imaging spectrometers provides information on absorption feature characteristics. Spectral shape parameters such as width, depth, skewness, and symmetry are more indicative of biochemical state and canopy physiology than average reflectance measured over relatively broad spectral regions. Variations in spectrum shape in the visible region relate to chlorophyll concentration, chlorophyll degradation, and other pigment activity. Other canopy biochemical constituents, such as cellulose and lignin, influence reflectance in the shortwave infrared and can potentially be quantified using imaging spectrometry. Capability to estimate biochemical properties in terrestrial ecosystems would aid in the assessment of carbon fixation/allocation patterns, nutrient availability and soil respiration.