CROISSANCE RADIALE ET SENSIBILITÉ AU CLIMAT DU PISTACHIER DE L’ATLAS, PISTACIA ATLANTICA DESF., EN ALGÉRIE

Few studies have been made of the Mount Atlas mastic tree, Pistacia atlan- tica Desf., despite its importance as part of Algeria’s steppe and desert eco- systems (Ahaggar: central Sahara). The species is of particular ecological and biogeographical interest as its associ- ation with other characteristic species  of arid and semi-arid Saharan habitats point to a  high  degree  of  resistance to global changes, especially climate change. The question addressed here is to understand how this tree species is responding to climate change along an aridity gradient. A dendro-ecological study was undertaken to identify the climatic factors governing radial growth in the species. Using this approach makes it possible to identify the rela- tionships, at different scales in space and time, between climate variability and the variability of radial  growth in the Mount Atlas mastic tree. The tree’s response to extreme climatic events was investigated through analyses of characteristic years. Four  populations in two different regions were analysed: the high steppes around  Djelfa  and  the pre-Saharan region around Bechar. The analysis showed that characteris- tic years are highly dependent on both average annual precipitation and aver- age annual temperature. Years with high growth are the wetter years, while years with low growth are the drier years. The response of the Mount Atlas mastic tree to wide climate variability is reflected in high values for the average sensitivity coefficient. Response function analysis shows the importance of precipitation in the radial growth of the species, and the lesser importance of temperature under conditions that vary with the biotope.