Scots pine (Pinus sylvestris L.) die-back by unknown causes in the Aosta Valley, Italy

For about ten years we have been recording some specific mortality phenomena firstly on Scots pine and secondly on other species in an area of the Aosta Valley where polluting substances may be present. A fast progressing die-back has been affecting, especially in spring, single trees and groups of different ages, no matter if dominant and apparently healthy, until Scots pine has almost disappeared from mixed woods of middle-low altitude on the north-facing mountainside. The Self-governing Region of the Aosta Valley (longitude 7° 30° W: latitude 45° 30° N) has been financed by the European Economic Community to realize an integrated study on the territory, including a survey of ecological parameters.