Age-driven shifts in functional composition and diversity shape ecosystem service provision in agroforestry systems

Land-use intensification has simplified functional biodiversity in tropical ecosystems, undermining the provision of ecosystem services. Although agroforestry systems (AFS) have been widely promoted as sustainable alternatives to deforestation, it remains unclear how system age influences plant ecological strategies and functional diversity, and how these functional patterns affect the provision of ecosystem services. We evaluated the functional traits and diversity of tree species across eight AFSs in western Amazonia, differing in age. We measured above- and below-ground traits linked to plant ecological strategies, along with ecosystem functions that act as proxies of key ecosystem services. These functions included primary productivity, soil water regulation, soil protection, and nutrient pool, which were linked to regulating ecosystem services following the Common International Classification of Ecosystem Services. We assessed how system age affects functional identity, trait complementarity, and multifunctionality, and how these functional patterns influence these ecosystem functions and, consequently, the provision of regulating ecosystem services. Our findings reveal that the human-driven functional composition of tree communities shifts systematically with AFS age, promoting soil fertility and protection, and aboveground biomass storage, which may reduce external inputs and enhance climate resilience. Also, in long-term AFSs, functional traits converged toward conservative strategies, while above- and below-ground traits remained orthogonal, which support ecosystem multifunctionality and may enhance stability while reducing management costs. Functional identity, particularly traits such as specific leaf area and root tissue diameter, was also related to ecosystem functions, including soil protection and soil water regulation, respectively. These results reinforce the need to consider functional traits in agroforestry planning and policy, which can improve resilience and long-term ecosystem service provision, particularly in degraded tropical areas, strengthening the role of agroforestry in sustainable agriculture.