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Evolution of growth-climate relationships of three pine species in Kroumirie (North-West Tunisia) Volume 24, issue 2, Avril-Mai-Juin 2013

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Institut national de recherches en génie rural, eaux et forêts BP 10 Rue Hedi Karray - Menzah 4 2080 Ariana Tunisie

A dendroclimatological study was carried out in Kroumirie on radial growth series of three pine species ( Pinus halepensis Mill., Pinus pinea L. and Pinus pinaster subsp Renoui) in order to test the influence of climate on the year-to-year radial growth variation and to check whether the relationship between radial growth and climate has been stable or not over the last decades. The analysis of the tree growth to climate relationship of these pine species by means of statistical models (response functions) shows the high sensitivity of these species to April, May and June precipitation. The study of the variations in the relationship between radial growth and climate over time shows the occurrence of a positive correlation with April, May and June precipitation and a negative correlation with temperature, especially during the 1970-2001 period. These observations could express an increasing water deficit during a season when the water needs are maximal. Comparison between estimated and observed growth shows a downward trend for the estimated growth from the 70's for Pinus halepensis and Pinus pinaster, which could reflect a change in the relationship between radial growth and climate in relation with the increase of atmospheric CO2. However the increase of drought intensity during the 21st century as predicted by climate models could overcome the compensatory effect assumed by atmospheric CO 2, thus causing a severe forest dieback in Kroumirie.