Spatial and temporal distribution of ozone symptoms across Europe from 2002 to 2014

Ozone-induced visible foliar injury has been assessed during 2002-2014 according to ICP Forests standardized methods. This activity provided 29,809 records from 285 woody plant species, 169 plots and 19 countries. Data were evaluated for the entire period 2002-2014 as well as for 2009 only, when spatial coverage was the greatest. First results reveal that 55.0% of the assessed plots were symptomatic, and 26.0% of species developed ozone visible injury. Beech (Fagus sylvatica) was the species with the highest frequency of symptomatic observations (plot and years) in both 2002-2014 (40.1%) and 2009 (42.9%). The frequency of symptom reports occurred without a clear spatial pattern. In case, higher frequency of symptom occurrence seemed more common from northern Italy to NorthWest Germany, and towards East Europe. At country level, temporal trend analysis indicates a downward trend of mean frequency of symptomatic species for five out of six countries. Overall (all plots together), there is a slightly decreasing trend, which is consistent with the decreasing trend observed for ambient ozone concentrations. These first results demonstrate the potential of the survey on visible foliar injury to detect the potential impact of ozone on European vegetation. Further, enhanced quality control procedures are underway to aggregate the datasets and promote a more indepth exploitation of cause-effect relationships, considering ozone symptoms, ozone concentration and measurements on forest health, growth, nutrition, biodiversity and climate undertaken at the ICP Forests plots.