CLIMATIC EFFECT OF ATMOSPHERIC CO2 DOUBLING ON RADIAL TREE GROWTH IN SOUTH EASTERN FRANCE

The climatic effect of a doubling of atmospheric CO2 on radial growth of trees was studied in ten populations of three species in south east ern France using an Atmospheric General Circulation Model (AGCM) predi cting a 3 degrees C increase of mean temperature and a light rise of p recipitation. Results are based on empirical growth climate models, in volving an Artificial Neural Network (ANN) technique. Only two of the studied populations, on the boundaries of their ecological area, are s ensitive to the climatic variations. One is the larch (Larix decidua M ill.) population located at 2300m on elevation (near the timberline) w hich shows a radial growth increase. The other is the most southern Fr ench Scots pine (Pinus sylvestris L.) population which reacts with a s evere growth rate reduction.