oa Reconstructing Past Precipitation δ2H Values in a Small Swiss Lake: A Vegetation-Corrected Approach using Plant Wax Isotopes

Plant wax stable isotopes (d13C and d2H) in lake sediments are valuable tools for reconstructing past climate and environmental changes. Here we analyze a 14-m sediment core from Rotsee, a pre-alpine lake in central Switzerland, to disentangle hydroclimate signals from local vegetation influences. By integrating plant wax d13C values and molecular distributions, we quantify the relative contributions of woody plants and grasses, allowing for the reconstruction of past precipitation d2H values (d²Hprecip).

Our results indicate that during the Younger Dryas (12.9–11.7 ka), cold and arid conditions prevailed, with d2Hprecip reaching values around -75‰. A two-step increase in d2Hwax values marks the Early Holocene, driven first by hydroclimate changes (∼20‰) and later by vegetation shifts (∼30‰). The Holocene Thermal Maximum (9.5–6 ka) shows increased woody vegetation and aquatic plant input, with d2Hprecip peaking at -55‰. During the Roman Period (∼2 ka), d2Hwax declined sharply, suggesting human-driven deforestation, while d2Hprecip remained stable.

This study highlights the necessity of correcting for vegetation effects in d²Hwax records and provides a framework for d2Hprecip reconstructions across Europe, improving our understanding of past hydroclimate variability.