Report on the Session

Abstract

Until recently, pollution damage to forests was largely due to individual sources, which affected trees in their immediate vicinity. An example of this type of problem was seen in our visit to the Grand-Chartreuse forest during this symposium. Dieback of conifers, and replacement by beech and other deciduous species had occurred in the vicinity of a small cement works situated at the bottom of a steep valley. Visible leaf injury could be observed close to the works, while analysis of leaf sulphur concentrations had shown significantly increased concentrations in the area around the works. Thus inspection of macroscopic damage in the area, together with a simple chemical test, had allowed the problem to be diagnosed as being due to SO₂ emissions from the works, with the spatial variation in symptoms in relation to the source being a key element in the diagnosis.