| The premise of this investigation is to elucidate the connection between changing geochemical substrates, resultant changes in conifer biochemistry (i.e., monoterpenes in oleoresin and other coincidentally responding constituents) and any associated alteration of the plant's reflectance curve. Predicting a change in monoterpene/oleoresin chemistry as a function of tree health due to changes in the substrate chemical environment, using field spectroscopy was the ultimate goal of the research behind this project. Three phases of field sampling and laboratory analyses to evaluate this relationship has been conducted at several CO2 induced tree kill areas around Mammoth Mountain in eastern California. Needle and branch samples of lodgepole ( Pinus contorta) and white bark (Pinus albicaulis) pines in various stages of stress (apparently healthy, stressed or dying/dead) were collected and analyzed in late summer/fall of 2000, 2001 and 2002.;This study identifies significant differences in the monoterpenes between lodgepole and white bark pine samples collected from the at the Mammoth Mountain sampling areas. It was also determined that the monoterpene composition pattern of each species also significantly varied as the conifer health degrades. Even though it was determined that the relative ratios of the monoterpenes in each conifer varies as the health of the tree declines, the overall differences in the monoterpenes between the two species remains intact.;Several vegetation spectral indices (i.e., NDVI and WI) and four SWIR spectral bands (1650, 1730, 2100 and 2300 nm) were found to significantly co-vary with two monoterpenes (alpha-pinene and myrcene) of needle resin from lodgepole pines collected around the tree kill areas. Review of the literature and our own findings indicate the possible relationship of the four SWIR spectral bands with hydrocarbons like the monoterpenes. A model is presented describing the probable occurrence of monoterpenes on or enveloping the needle surface. Though previous research has led to speculation that the monoterpenes may be associated with the spectral character of the four SWIR peaks, the covariance results of this study are the first showing a significant correlation of the spectral reflectance of the four SWIR bands with monoterpenes thus supporting earlier speculation by previous researchers. |
