Elevate concentrazioni di ozono nell’Italia mediterranea: una sfida alle foreste?

Abstract

Abstract: Tropospheric ozone pollution has changed from local phenomenon to global issue, because of a continuous rising - especially in developing countries - and intercontinental transport. Ozone ground levels, however, are higher in the world regions with strong photochemical activity, like the Mediterranean basin. The aim of this work is to review available data on ozone ground levels and damages to forests in Italy, with focus on the areas exposed to the highest concentrations, i.e. Southern Italy. Data from both ozone monitors and passive samplers suggest that ozone levels increase North to South in Italy. Therefore, an increase in ozone damages to forests is likely across this gradient. Conversely, the reports (presence/absence) of visible ozone-like foliar injury do not show a clear geographic trend, although they are still limited in number. Preliminary investigations suggest that ozone tolerance in evergreen sclerophylls and Southern provenances is higher than in mesophilic species and Northern provenances. The higher tolerance is due both to avoidance, i.e. stomatal closure, and to an active antioxidant pool. This would suggest AOT40 is modified on the basis of both stomatal conductance and antioxidant capacity. Available data are still not enough to determine the effect of present ozone regimes on Italian Mediterranean forests. Future investigations should aim at: (1) filling the gap on ozone levels in Italian remote areas, by using passive samplers and/or biomonitoring; (2) establishing ozone responses in the most typical Italian vegetation, for both O3 uptake and detoxification, in realistic conditions and in interactions with other factors, mainly drought and the increase in atmospheric CO2 concentrations; (3) extensive monitoring and quantification of ozone-like foliar injury across Italy. Confirmation of higher ozone tolerance in the Mediterranean vegetation might imply differing ozone critical levels across Europe.