Environmental controls of leaf-wax n-alkane hydrogen-isotopic signatures along an elevation transect at Mount Kilimanjaro
 

Objectives

Leaf-wax n-alkanes are produced by terrestrial plants, and through long-term preservation in sediments their stable hydrogen-isotopic signature (δ²H_wax) provides useful information on past hydrological variation for paleoclimate reconstructions. However, gaps remain in our understanding of the relationships between the isotopic signatures of leaf waxes and the plants’ source water. In this study, we report observations from a data-scarce tropical region in equatorial East Africa, with the overarching aim to improve mechanistic understanding required for reliable interpretation of δ²H_wax as paleohydrological proxy. We investigate the distribution patterns of leaf waxes (i.e. average chain length and carbon preference index) and δ²H_wax from diverse species and growth forms of terrestrial plants during four successive wet and dry seasons along an elevation transect which covers distinct ecosystems at Mount Kilimanjaro (see figure below). Variation in δ²H_wax will be analyzed with linear mixed-effect models and compared with the associated δ²H values from a wide range of water sources, including local precipitation as well as plant xylem and leaf water, to determine the hydrogen-isotopic fractionation between the distinct water sources and leaf-wax n-alkanes (Griepentrog et al., 2019).