Climate signals in carbon and hydrogen isotope ratios of wood lignin methoxy groups

Background/Summary

The modern climate is facing a drastic rise in temperature due to the increasing emission of greenhouse gases. To predict how future climate will develop, models try to calculate possible scenarios based on paleoclimate reconstructions. Therefore, it is essential to collect paleoclimate data, to understand the most recent development in climate history under the influence of mankind.
 

Trees with their yearly increment tree rings are the perfect high-resolution method for paleoclimate reconstructions. Since trees grow in many different climate zones and can interact directly with the five geochemical spheres - Atmosphere, Hydrosphere, Lithosphere, Pedosphere and Biosphere - they can be used as a widespread climate proxy. The method of analyzing climate response of tree rings is called Dendroclimatology and enables annual resolved climate reconstructions by analyzing the relationship between several parameters like tree ring growth or stable isotope ratios and environmental conditions during the time of formation. By combining living and fossil tree ring chronologies, dendroclimatology provides an annual reconstruction of the paleoclimate for most of the Holocene.
 

This research group focuses on the climate parameter preserved in stable carbon and hydrogen isotopes of wood lignin methoxy groups (OCH₃). Next to cellulose, lignin makes up the main part of the wood with 25 - 30 %.
Our previous studies have shown that hydrogen isotope ratios of wood lignin methoxy groups primarily reflect large-scaled annual temperature, whereas carbon isotope ratios mainly preserve local summer temperature. Further studies will quantify the efficiency of isotope ratios of lignin methoxy groups as a climate proxy.