Investigations of Fundamental Processes Affecting Hydrogen and Oxygen Isotope Ratios of Tree Ring Wood Cellulose

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This award supports a fundamental set of experiments in paleoclimatic research. Isotopic paleodendroclimatology is founded on the assumption that wood cellulose hydrogen and oxygen isotope ratios co-vary in a one-to-one fashion with those of the water available to a tree. Qualitative and quantitative interpretations of wood cellulose isotope ratios involve the further assumption that post-photosynthetic processes do not affect cellulose isotopic compositions, and predict that humidity will influence wood cellulose D/H and 180/160 ratios. Neither of the assumptions may be valid, and the prediction of a humidity effect may be incorrect. Experiments that will resolve these fundamental uncertainties are to be performed with potatoes, avocados, the aquatic plant Lemna gibba, and protoplasts cultured from a variety of tree species of interest to isotope paleodendroclimatologists.