Ozone risk for vegetation in the future climate of Europe based on stomatal ozone uptake calculations

The negative impacts of surface ozone (O₃) on vegetation are determined by external exposure, leaf gas exchange and plant antioxidant defence capacity, all dependent on climate and CO₂ concentrations. In this study the influence of climate change on simulated stomatal O₃ uptake of a generic crop and a generic deciduous tree at ten European sites was investigated, using the LRTAP Mapping Manual stomatal flux model. O₃ concentrations are calculated by a chemistry transport model (MATCH) for three 30-yr time-windows (1961–1990, 2021–2050, 2071–2100), with constant precursor emissions and meteorology from a regional climate model (RCA3). Despite substantially increased modelled future O₃ concentrations in central and southern Europe, the flux-based risk for O₃ damage to vegetation is predicted to remain unchanged or decrease at most sites, mainly as a result of projected reductions in stomatal conductance under rising CO₂ concentrations. Drier conditions in southern Europe are also important for this result. At northern latitudes, the current parameterisation of the stomatal conductance model suggest O₃ uptake to be mainly limited by temperature. This study demonstrates the importance of accounting for the influences by climate and CO₂ on stomatal O₃ uptake, and of developing their representation in models, for risk assessment involving climate change.