Leaf wax n-alkanes are long-chained lipids that are vital components of plant cuticles. What makes leaf wax n-alkanes unique is that their stable hydrogen isotope composition (δ²H) contains information on precipitation and plant water relations. In addition, leaf wax n-alkanes are abundant in leaves, soils, sediments and even the atmosphere and can persist with their δ²H values over millions of years. With this exceptional combination of properties, leaf wax n-alkanes and their δ²H values are now being celebrated as the much-needed ecohydrological proxy. Despite the enormous potential that leaf wax n-alkanes have as ecohydrological proxy, the exact type of hydrological information that is recorded in the δ²H values of leaf wax n-alkanes remains still unclear. This is because critical mechanisms that determine the δ²H values of leaf wax n-alkanes are not understood.

This project will perform the experimental work that is now needed to resolve the key mechanisms that determine the δ²H values leaf wax n-alkanes. These experiments will set the basis to develop a new numerical model that will allow to ultimately test the exact hydrological signal that leaf wax n-alkanes record in their δ²H values: Is it a mere hydrological signal reflecting the amount or origin of precipitation or a plant-shaped signal indicating plant water relations such as evapotranspiration? Building on this new model, COSIWAX will set out to test the potential that leaf wax n-alkane δ²H values hold as new ecohydrological proxy for ecology and ecosystem sciences. If successful, COSIWAX will establish with this research leaf wax n-alkanes δ²H values as an innovative ecohydrological proxy that has extensive possible applications in paleoclimatology, ecology, earth system sciences.