Understanding how the Argan tree adapts its performance in a heterogeneous environment using wood anatomical and leaf functional traits

Abstract

Plant responses to environmental factors—specifically, in this study, sap conduction potential, resource use, and photosynthetic capacity—generally involve the simultaneous variation of both independent or correlated traits. To better understand these responses, we develop an integrated approach that examines multiple functional dimensions, defined as groups of correlated phenotypic traits that reflect the constraints and trade-offs shaping the Argan tree phenotype. Our aim is to assess the Argan tree's ability to withstand ongoing climate change, particularly the significant increase in temperature and aridity. In this study, we focus on wood anatomical traits related to sap conduction and reserve storage, alongside structural and physiological leaf traits. To date, this combination of traits has not been systematically studied in the Argan tree. By integrating these functional dimensions, our approach allows us to identify key traits and trait combinations that explain the species' distribution and resilience to heterogeneous environmental and climatic stressors. Furthermore, it enables the identification of bioindicator characters that are sensitive to variations in biogeographical, geographical and climatic factors, facilitating the development of trait-based models of plasticity or adaptation of performances along environmental gradients. Ultimately, this study establishes the eco-functional foundations of the Argan tree, providing insights into its tolerance and resilience to drastic environmental changes. Given its ecological, anthropological and socio-economic significance, understanding the adaptive strategies of this emblematic woody species is crucial for predicting its future persistence under increasing environmental pressures. • The Argan tree exhibits high plasticity in both leaf and wood anatomical traits. • Thermal conditions play a significant role in the plasticity of wood traits. • Leaf traits are modulated according to continentality/oceanity and aridity. • Coordination of wood and leaf traits reflects a whole-plant resource-use strategy. • Despite increasing stressful conditions, overexploitation remains the major threat.