Croissance radiale et sensibilité au climat du pistachier de l'Atlas, Pistacia atlantica Desf., en Algérie

Abstract

Few studies have been made of the Mount Atlas mastic tree, Pistacia atlantica Desf., despite its importance as part of Algeria's steppe and desert ecosystems (Ahaggar: central Sahara). The species is of particular ecological and biogeographical interest as its association 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 relationships, 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 Béchar. The analysis showed that characteristic years are highly dependent on both average annual precipitation and average 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.