Sarah Feakins - Colloquium Talk Abstract

Plant wax biomarkers in the Andes-Amazon: Signals of elevation, ecology and hydrology

Plant waxes perform multiple functions for living plants and through their remarkable resiliency they leave a rich sedimentary legacy for biogeochemical interpretation. In the past decade, I’ve studied the isotopic signatures of these compounds in sedimentary archives around the world, and now find it is time to answer hard questions about these biomarkers in challenging tropical environments. How well do plant biomarkers work as paleoenvironmental proxies in the tropical context of high biodiversity, and how are these biomarkers exported from source to sink? My talk will take you on a picturesque journey through from the tropical montane forests of the Andes, down into lowland Amazonia, via the Madre De Dios River within Peru. Through ambitious sampling campaigns in remote environments, my collaborators and I have acquired unprecedented sample sets across steep topographic, environmental and ecological gradients. In my lab at USC, my group has analyzed the leaf wax molecules in Andean and Amazonian forests and found they capture elevation-specific isotopic signatures. We analyzed the same biomarkers in fluvial transport to determine spatial and temporal integration processes, and the downstream propagation of those signals. This new study provides much needed insights into the source to sink processes of terrestrial biomarkers, needed for two important objectives: 1) the spatial significance of terrestrial signals in lake and marine core sediment core reconstructions, and 2) quantification of export versus remineralization of terrestrial organic carbon from major tropical montane river systems.