Evaluating the use of near-infrared reflectance spectroscopy as a proxy measure of carbon and nitrogen isotopes in the leaves of Black Cottonwood (Populus trichocarpa) Leung, Andy
Stable isotopic measurements are one of the more powerful tools used to help advance our understating of plants and their environment. Yet this tool is underutilized because of the large amount of resources and time it takes to extract this information. In this study, I evaluated if near-infrared reflectance spectroscopy can be used as a faster and more economical way to estimate the ratios of carbon and nitrogen isotopes in tree leaves. The δ13C and δ15N values were determined with samples of Black Cottonwood leaves (Populus trichocarpa) taken from 3 different clones and grown in two different CO₂ concentration conditions. The samples were scanned with a near-infrared reflectance spectrometer (NIRS) to create calibration models. These models are created using partial least-squares regressions and tested by cross validation procedures. The resulting calibration models were unable to accurately predict the amount of δ13C and δ15N in the leaves as none of the models could produce a high correlation coefficient. The reflectance spectra produced by the NIRS was able to differentiate the two different CO₂ concentration treatments, and was also able to classify clones from different origins based on their reaction to the CO₂ concentration treatments.
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