Understanding anatomical plasticity of Argan wood features at local geographical scale in ecological and archaeobotanical perspectives

The emergence of the Argan tree as an agricultural, pastoral, cultural, economic and ecological keystone species in Southern Morocco is considered to be linked to the settlement of agropastoral communities that favored its expansion. Nevertheless, the use and exploitation of Argan tree is documented by both few medieval written sources and archaeobotanical studies, from a single location, Îgîlîz (Toughmart, Morocco), a famous medieval site of the Anti-Atlas Mountains. Therefore, data remain scarce regarding the type of Argan communities exploited at this period. In order to document this question, a quantitative eco-anatomical approach aiming to understand variations of wood characters involved in sap conduction and reserve storage, is developed from modern samples collected in the area of Îgîlîz. Results show that diameter of branches and environmental factors are the major parameters explaining plasticity of wood anatomical characters. Quantitative eco-anatomical features of Argan archaeological charcoal confronted to two statistical models, allow assessing both the diameter of the branches from which it derives and the agro-ecological conditions of tree growth and development. This preliminary study may be considered as a relevant and pioneering work for the understanding of the eco-history of the Argan tree, and of its use and exploitation during the past.