Imaging spectrometry for monitoring tree damage caused by volcanic activity in the Long Valley caldera, California

Developments in detector technology have triggered a new remote sensing technology: imaging spectrometry. Imaging spectrometers measure reflected solar radiance on a pixel-by-pixel basis in many narrow spectral bands, allowing the identification of materials or their properties by diagnostic absorption features. To date, only airborne imaging spectrometers are available, but several imaging spectrometers are planned for the next generation of space platforms. The abundance of information available in the continuous spectral coverage makes it possible to address questions in numerous environmental disciplies. This paper describes a study in the Sierra Nevada, using multitemporal images acquired by the Airborne Visible/InfraRed Imaging Spectrometer (AVIRIS) for monitoring tree damage by volcanic activity. Diffuse volcanic gas emanations deprive the roots of oxygen, resulting in trees that are under stress and ultimately die. Imaging spectrometry yields important information on tree conditions and on the presence of dead vegetative material. The spatial and temporal extent of the dead and stressed tree areas were mapping using AVIRIS data. The use of imaging spectrometry to map the diffuse volcanic gas emissions was less successful. Although the images yield noisy spatial patterns of carbon dioxide, it is difficult to separate atmospheric gases from the diffuse soil emanations.