Articles | Volume 13, issue 13
Research article
06 Jul 2016
Research article |  | 06 Jul 2016

Simulating oxygen isotope ratios in tree ring cellulose using a dynamic global vegetation model

Sonja G. Keel, Fortunat Joos, Renato Spahni, Matthias Saurer, Rosemarie B. Weigt, and Stefan Klesse

Abstract. Records of stable oxygen isotope ratios in tree rings are valuable tools to reconstruct past climatic conditions and investigate the response of trees to those conditions. So far the use of stable oxygen isotope signatures of tree rings has not been systematically evaluated in dynamic global vegetation models (DGVMs). DGVMs integrate many hydrological and physiological processes and their application could improve proxy-model comparisons and the interpretation of oxygen isotope records. Here we present an approach to simulate leaf water and stem cellulose δ18O of trees using the LPX-Bern DGVM (LPX-Bern). Our results lie within a few per mil of measured tree ring δ18O of 31 different forest stands mainly located in Europe. Temporal means over the last 5 decades as well as interannual variations for a subset of sites in Switzerland are captured. A sensitivity analysis reveals that relative humidity, temperature, and the water isotope boundary conditions have the largest influence on simulated stem cellulose δ18O, followed by all climatic factors combined, whereas increasing atmospheric CO2 and nitrogen deposition exert no impact. We conclude that simulations with LPX-Bern are useful for investigating large-scale oxygen isotope patterns of tree ring cellulose to elucidate the importance of different environmental factors on isotope variations and therefore help to reduce uncertainties in the interpretation of δ18O of tree rings.

Short summary
Records of stable oxygen isotope ratios in tree rings are valuable tools for reconstructing past climatic conditions. So far, they have not been used in global dynamic vegetation models. Here we present a model that simulates oxygen isotope ratios in tree rings. Our results compare well with measurements performed in European forests. The model is useful for studying oxygen isotope patterns of tree ring cellulose at large spatial and temporal scales.
Final-revised paper