Tracking the isotopic fingerprint of defoliation in tree rings

Recent tree-ring isotope research has shown that defoliation events can be identified by a characteristic isotopic fingerprint stored in tree rings, showing a decoupling of cellulose-stored hydrogen and oxygen isotopes. However, until recently only a few studies have studied hydrogen in tree rings. Due to the novel mass spectrometry method developed at the WSL, we are now capable to produce triple-isotopes (C, O, H) chronologies stored in tree-ring cellulose. This project aims to detect a "defoliation fingerprint" by analysing the changes in H and O isotope ratios in tree rings from populations of different tree species that have been regularly exposed to abiotic (frost) and biotic stressors (insect outbreaks) causing severe defoliation.This methodology will be tested and developed on both fresh and archaeological wood samples. The successful identification of this "fingerprint" would serve as a valuable proxy for improving dating accuracy and detecting changes in defoliation frequency.