【研究紹介】

Tree ring isotope composition to inform models assessing the sensitivity of the forest carbon budget to increased atmospheric CO₂ and climate change

　EPRON Daniel　　京都大学／特定教授（森林生理学）

　Reliable projections of future forest carbon dynamics are needed owing to the role of forest in the global carbon budget. The objective is to demonstrate that the isotope composition of tree rings provides invaluable information on the physiological response of forests to changes in atmospheric CO₂ and climate, not only at tree level but also at the ecosystem scale. We will demonstrate that the tree ring isotope signals track the interannual variations in canopy photosynthesis, evapotranspiration and stand level water use efficiency, by comparing simulation using a multi-layer ecosystem gas exchange model parameterized with long-term series of δ¹³C, δ¹⁸O and δ²H in tree rings with 20-year data of stand-level CO₂ and water fluxes, and 50-year data of evapotranspiration calculated from watershed hydrological data. Extending this innovative approach to other forests around the world will be useful to constrain global vegetation models and improve their parameterization.

Keywords：Tree rings, stable isotopes, forest carbon budget, atmospheric CO₂, climate change, watershed