Hydrogen isotopes in n-alkanes of tree leaves and needles: experimental studies with ecophysiological, ecosystem, climate, and dust-related applications

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Stable isotopes of plant materials serve as natural biochemical tracers and integrators of both environmental and physiological signals that are of widespread interest in biology, ecology, geology, climate science, and food science. One interesting plant biochemical component in leaf waxes (normal-alkanes) is proposed to serve as both a biomarker in sediments recording climate signals and as a region-of-origin signal for modern ecological and food science applications. Laboratory experiments and field observations in this project will test a mathematical model of how an environmental and region-of-origin biochemical signal is recorded in the stable isotopes of leaf waxes. Our initial hypothesis is that the hydrogen isotope ratios of n-alkanes in leaf waxes record the isotope ratios of environmental water, which are already known to record significant geographic and climatic information. Alternative hypotheses are also proposed and will be tested. Using gas chromatography, mass spectrometry and isotope ratio mass spectrometry techniques, this project will analyze 36 perennial tree and shrub species from six different ecological systems across the western United States. One of the broader impacts of this project is to forge new interdisciplinary linkages among biology, geology, and climatology. Postdoctoral training in this project will focus on generating new scientists more capable of bridging the common interests of these disciplines. Research results will be incorporated into lecture and lab portions of an annual international stable isotope ecology course at Utah that already attracts a multidisciplinary spectrum of graduate students and post doctoral associates from geographically distributed institutions across the United States and from strong institutions around the world. The results of this project will be incorporated into web-based modules distributed at http://stableisotopes.net. Here the broader impacts of the research will allow users to explore isotope landscape-scale patterns, including determining source regions for n-alkanes in modern samples.