Ozone levels and foliar injuries on Mediterranean species

In the Alpes-Maritimes, in the South of France, a research is carried out to know the eventual impact of pollutant ozone on foliar damage noted these last years on specific pines forests. This concerned Pinus halepensis, Pinus sylvestris and Pinus cembra. This study is leaded as part of an European project (Interreg II) and a national project (Primequal). This publication indicates firstly ozone concentrations in 1999 summer, from the French Riviera coastal until the Mercantour mountains. This has been registered with the help of many diffusing passive samplers and a physic analyzer. The indicative value of AOT 40 is calculated, it is computed by summing the hourly excess ozone concentration above 40 ppb during daylight hours (global radiation > 50 W/m super(2)) over the growing season (taken as the period April-September). The critical level of AOT 40 is 10 ppm.h during a 6 month period. In the Riviera area, the near-ambient AOT 40 value, calculated during 4 months in summer 1999, is twice above the European indicative value. The sum of hourly ozone concentration, during the summer experiment, amounts to 162,2 ppm. In a same time, foliar damage is estimated on geographic sites where ozone diffusing passive samplers were located. Needle defoliation and discoloration percentage are evaluated according to their visible damage. Correspondence between ozone levels, geographic situations and foliar injury are leaded for understanding the interrelation of all these factors.