Radial growth and response to climate of the mount Atlas mastic tree (&ITPistacia atlantica &ITDesf.) in Algeria's Theniet El Had National Park

The distribution range of the Mount Atlas mastic tree in North Africa extends from the Tellian Atlas mountains, where it is found together with Atlas cedars, to the central Sahara where it grows with acacias. It has a very wide ecological range making it a suitable candidate for extension with the advance of climate change effects. To follow a previous article on the relationship between climate and growth rings, this paper reports on the way climate determines the tree's radial growth in forested environments in a sub-humid bioclimate. The study was conducted in two stands on the slopes of Djebel Meddad, one south-facing and one north-facing. Our analysis of responses to extreme climatic events based on calculations for characteristic years shows that the species is more sensitive to extremes in warmer conditions of exposure, especially when these events inhibit growth. Average sensitivities are very similar on both slopes but low compared to those obtained for arid and semi-arid regions. Analysis of growth indicators shows that thin and thick growth rings always correspond to especially dry and especially rainy conditions. Average annual temperatures only have an additional effect. No very thin growth rings were recorded on either slope. The response functions show that climatic factors in a given year play a major role in the construction of growth rings.