Impact of ground-level ozone on Italian forests: application of innovative monitoring methodologies in the forest

Ground-level ozone (O3) is one of the main atmospheric pollutants and can cause serious damage to forest ecosystems due to its high phytotoxic effect. Therefore, O3 forest monitoring is crucial to study its harmful effect on vegetation and establish new critical levels for the forest protection. Results of the application of innovative active monitoring stations in the forest, installed as part of the European project LIFE MOTTLES (MONitoring ozone injury for seTTing new critical LEvelS) are shown. The experimental areas were selected within the CON. ECO.FOR network, where two different cumulative indices based on exposure to O3 in the atmosphere (AOT40) and on the stomatal flow of O3 (PODY) were estimated. These metrics were correlated with forest health indicators such as visible foliar injury and crown defoliation assessed both inside the plot (ITP) and along the forest edge (LESS), to derive exposure-based (CLec) and flow-based (CLef) critical levels. Results suggest CLec and CLef of 17,000 and 19,000 ppb h AOT40 and 12 and 5 mmol m-2 POD1, respectively, for coniferous and broadleaved species. Active monitoring system allows to assess and steadily updates critical levels and legislative standards for the forests protection. Moreover, an active monitoring system resulted also more sustainable from an environmental, economic and social point of view in the long period than a traditional passive one.