LEAF WAX HYDROGEN AND CARBON ISOTOPE RATIOS MEASURED FROM BASE-TO-TIP IN FIVE TERRESTRIAL C3 PLANT SPECIES: IMPLICATIONS FOR PALEOCLIMATE RECONSTRUCTIONS

Carbon and hydrogen isotope ratios in terrestrial leaf waxes are essential paleoclimate proxies for reconstructing the past climatic and ecological variability. However, further research on the controls of leaf wax isotope ratios and individual leaf wax gradients needs to be completed in order to more accurately infer past climate conditions. Many studies of modern leaf wax synthesis have studied the isotope ratios of entire leaf samples. Here, we divide individual leaves into four to seven sections (depending on the plant species), and assess the isotopic gradients along a leaf. Five species, all using C₃ photosynthesis, were sampled to determine their hydrogen and carbon isotopic ratios in leaf wax, and their hydrogen and oxygen isotopes ratios in leaf water. A similar analysis on C₄ grasses has been completed (Gao et al. 2012). Grasses show increasing hydrogen and decreasing carbon values from the base to the tip of a grass sample in C₄ plants. Analysis of C₃ plant species will provide a more comprehensive study of individual leaf isotopic gradients, as well as provide further insight to the controls of bulk leaf wax isotope ratios.