ENVIRONMENTAL INFLUENCES ON SPECTRAL REFLECTANCE AND OLEORESIN CHEMISTRY OF CONIFERS, MAMMOTH MOUNTAIN TREE KILL AREAS, CALIFORNIA

Sampling and analyses of lodgepole and white bark pines to evaluate the relationship between oleoresin chemistry and spectral reflectance changes as a function of plant health were completed at the Horseshoe Lake and other CO2-induced tree kill areas around Mammoth Mountain, California during the fall of 2000, 2001, and 2002. Literature review and evaluation of the Mammoth Mountain datasets indicate that each variable undergoes a series of changes that relate not only to the health state but also the nature of the impact (i.e., biotic vs. abiotic). Analysis of the 2000 dataset collected from the Horseshoe Lake tree kill-area identified a series of absorption features and monoterpene compositions that discriminate between the two end-member health states (healthy versus dying/dead). Several of the adsorption features found (e.g., 1650, 1730, 2100 and 2300 nm) fall within spectral regions typically associated with olefinic hydrocarbons such as the monoterpenes.

An expanded sampling design was used during the 2001 field program incorporating conifers from other CO2 tree kills (Red's Lake, Chair 12 & Secret Spot) and several background areas. Initial interpretation of the complete 2001 dataset indicated that, in addition to plant health, both herbivory and the geochemistry of the substrate contributes to the composition of monoterpenes and the spectral reflectance of the conifers. Covariance and regression analysis between the hydrocarbon-related spectral features and monoterpene concentrations measured from the pine samples indicate that several statistically significant models exist distinguishing healthy, stressed, and dying/dead samples after correcting for effects of herbivory and substrate geochemistry. Similar results from the 2002 survey further evaluating the relationship between the spectral features, monoterpene composition and environmental factors such as CO2-induced plant stress, herbivory, and geochemical substrate are also discussed.