Ozone and coniferous species in South-East France
In South-East France, major loss of leaves by several coniferous species has been recorded in association with high concentrations of ozone. Recent research has made it possible to distinguish the symptoms specifically related to ozone in the leaves and needles from those caused by other stress factors. This study presents the levels of ozone measured in the year 2000 along the coast and in the hinterland near Nice and compares them to the degree of loss of colour and leaves observed on five coniferous species. On P. cembro, needles were taken to detect and verify the presence of specifically ozonerelated symptoms. Ozone levels were sufficient to produce visible symptoms and, probably, to affect the trees' growth. In any event, macro- and microscopic symptoms typically due to ozone were observable in the hinterland. They indicated a state of stress and an acceleration in the ageing of the needles for the P. cembro. Ozone is no doubt a factor contributing to the poor state of health of this species in the Alpes-Maritimes département. The extent of the role played by ozone as opposed to that of other stress factors, notably repeated drought conditions and recent changes in climate, requires further research.