USING STABLE ISOTOPES OF PLANT LEAF WAXES FROM SONORAN DESERT NATIVES TO UNDERSTAND PLANT LIFE HISTORIES ON AN ANNUAL SCALE

Abstract

As climate change alters the Sonoran Desert, it is important to understand carbon movement within this unique ecosystem. Serving as one of the first known studies of its kind, this study uses carbon isotope fractionation tracers to investigate annual life histories of four key Sonoran Desert plant species that have evolved to incorporate either C3 or C4 photosynthetic mechanisms: Prosopis velutina (velvet mesquite), Olneya tesota (ironwood), Simmondsia chinensis (jojoba), and Aristida ternipes (spidergrass). Wax n-alkane chain-length distributions (average chain length, ACL; and carbon preference index, CPI) as well as n-alkane carbon isotopic composition (?13C) are analyzed to study how plants alter their waxy leaf coatings through the seasonal cycle in response to water stress and the growing seasons. C3 plants had an average leaf tissue δ13C value of -31.0‰ and C4 plants had an average value of -26.6‰. δ13C anomalies also show a greater enrichment of 13C in C4 plants, demonstrating C4 plants respond more readily to seasonal variability and precipitation events, in comparison. Overall, this study serves to provide possible implications for the role of an arid environment on plant n-alkane distributions within the Sonoran Desert Region.