Impact of a climatic warming scenario on tree growth.

The climatic impact on tree radial growth resulting from an atmospheric CO2 doubling was studied for 24 populations of five tree species in the French Alps and the French Mediterranean area. The Arpege AGCM, which predicts a 3 degreesC increase in mean temperature and a light increase of precipitati on, is used to estimate the climatic perturbation. The method is based on t he integration of estimated climate in an empirical tree-ring to climate mo del, involving artificial neural networks. Only a few populations are sensi tive to the climatic change; all are located on the boundaries of their eco logical area and can be divided in two groups. The first one is composed of high altitude populations which show a growth increase induced by the warm er climate during the growing season. The second one, composed of a single Mediterranean Scots pine population, reacts with a severe growth reduction induced by the stronger water stress in summer. (C) 2000 Academie des scien ces/Editions scientifiques et medicales Elsevier SAS.