Unmixing of Aviris Hyperspectral Data from Dixie Valley, Nevada

The high temperature hydrothermal convection system underlying northwestern Dixie Valley, Nevada, is probably responsible for the development of certain geobotanical anomalies in the area. A large “die-off’ of Bailey’s greasewood (Sarcobatus baileyi) has been observed over the last several months and appears to be related to activity that preceded the appearance of a new fumarole. AVIRIS (Advanced Visible and Infrared Imaging Spectrometer) airborne hyperspectral data was acquired for this area in May 1995, several months before the die-off was first recognized. Analysis of hyperspectral remote sensing data using polytopic vector analysis has resulted in the characterization of vegetal-spectral anomalies in the area of the die-off. Four spectral “fingerprints” were resolved and mapped. One of the four appear related to the S. baileyi die-off. Its spectrum closely matches spectra of healthy S. bailey. EM-1 was largely absent in the present area of the die-off at the time of the AVIRS image was collected. The fact that the analyzed AVIRIS image was taken months before the die-off was observed in the field suggests that spectral unmixing may prove an effective tool in anticipation of vegetative stress.