Impact of tropospheric ozone on the Euro-Mediterranean vegetation


A. Anav, tel. +33 1 69 33 51 47, fax+33 1 69 33 51 08, e-mail:


The impact of ozone (O3) on European vegetation is largely under-investigated, despite huge areas of Europe are exposed to high O3 levels and which are expected to increase in the next future. We studied the potential effects of O3 on photosynthesis and leaf area index (LAI) as well as the feedback between vegetation and atmospheric chemistry using a land surface model (ORCHIDEE) at high spatial resolution (30 km) coupled with a chemistry transport model (CHIMERE) for the whole year 2002. Our results show that the effect of tropospheric O3 on vegetation leads to a reduction in yearly gross primary production (GPP) of about 22% and a reduction in LAI of 15–20%. Larger impacts have been found during summer, when O3 reaches higher concentrations. During these months the maximum GPP decrease is up to 4 g C m−2 day−1, and the maximum LAI reduction is up to 0.7 m2 m−2. Since CHIMERE uses the LAI computed by ORCHIDEE to estimate the biogenic emissions, a LAI reduction may have severe implications on the simulated atmospheric chemistry. We found a large change in O3 precursors that however leads to small changes in tropospheric O3 concentration, while larger changes have been found for surface NO2 concentrations.