MARITIME PINE FOREST DIEBACK ON NORTH-ATLANTIC COASTAL DUNES

Stand and ecophysiological data sets from 20 maritime pine plots, have been compared. These plots were stratified into 2 groups by degree of vitality: healthy and declining. Using a stepwise multiple regression we found a negative correlation between the radial growth index of one year and wet winters of the previous year. Another observation was that these forest are compound in origin, with 2 kinds of provnance, "Aquitaine" and "Iberian". The foliar calcium/sodium and potassium/sodium ratio in the needles differentiate both the healthy vs declining populations and the 2 provenances. Results of a principal components analysis suggested that maritime pine forest decline is a climate provenance interaction phenomenon due to sodium toxicity.