Progress of the experimental activities
There is a synergy between the 3 experimental actions. We present, in this part, the main results and technical progress for the 3 experimental actions.
A large amount of data was collected at 30 plots in France and 49 plots in Italy (24 sites for ozone-induced symptoms campaign, 2 for ozone-fluxes campaign and 23 sites of the CONECOFOR network for radial growth data) by ENEA, GIEFS, IPP-CNR and ACRI-ST, as well as the follow-up of ozone and damages was successfully carried out in 2012 and 2013. The two ozone-induced symptoms campaigns were realized in summer 2012 and 2013 at 54 plots (30 in France and 24 in Piedmont region). At each plot, the transparency of the crown foliage (defoliation) and the leaf discoloration were noted. The ozone-induced symptoms were observed and noted on 5 trees at each plot. In parallel, in South-eastern France, 28 forest plots were equipped by ozone passive samplers (GIEFS) and changed monthly between April and September (growing season). From the flux-effect relationships, between AOT40, POD0, POD1 and the leaf loss, discoloration and percentage of leaf surface affected by ozone-induced symptoms, we derived and proposed new flux-based critical levels CLef for forest protection. An assessment based on phytotoxic O3 dose and real plant damage is more appropriate and we showed a better performance of PODY relative to AOT40. AOT40 is correlated with non-specific symptoms (leaf loss and discoloration) whereas specific O3-induced symptoms are only correlated with POD0 (or POD1 for Aleppo pine). POD0 and POD1 were provisionally identified for sensitive forest trees.
The ozone fluxes campaigns, in Castelporziano, San Rossore, Fontblanche and Puéchabon were successfully completed and measurements were retrieved, gathered and some statistical works are ongoing. The study in Castelporziano allowed a comparison between modeled and measured stomatal ozone fluxes and, then, a first validation of the stomatal flux model DO3SE (Deposition of Ozone and Stomatal Exchange). Thanks to the help and good cooperation of Stanislaw Cieslik, Carsten Gruening (JRC), Yasutumo Hoshika (JSPS) and Silvano Fares (CRA), it was possible to make these experimental campaigns and to download all the data recorded on the Eddy tower. The winter campaign at San Rossore was troubled due to a storm that damaged one of the instruments. An additional campaign at San Rossore will be held in January 2014. Both of the measurements, with the Eddy Covariance technique, allowed calculating stomatal ozone fluxes and will allow validating the DO3SE Model. This job is in progress. Advanced statistical approaches were used to investigate whether stomatal ozone fluxes affect gross primary production (GPP). Preliminary results did not show reductions in GPP either by ozone concentration or stomatal ozone flux, mainly due to the short time of measurements
A preliminary study, based on a comparison of the maps of total stomatal ozone uptake (POD0), threshold-based phytotoxic ozone dose (POD1), and concentrations exceeding 40 ppb (AOT40) for Pinus halepensis and Fagus sylvatica was conducted in South-eastern France and North-western Italy in 2010 and 2011. In 2012, we elaborated maps for 8 tree species: Abies alba, Fagus sylvatica, Pinus cembra, Pinus halepensis, Pinus pinaster, Pinus pinea, Pinus sylvestris and Quercus suber. The maps showed different distributions of AOT40 and PODY in this area. The information obtained by comparison of POD0 and POD1 trends didn’t show an improvement in the useful information adopting POD1 instead of POD0, and POD0 was suggested as the best indicator to predict the ozone impacts on vegetation.