Stand structural diversity and elevation rather than functional diversity drive aboveground biomass in historically disturbed semiarid oak forests

•Secondary forests are important reservoirs of biodiversity and ecosystem services.•Aboveground biomass (AGB) changes along elevational gradient and canopy cover Structural diversity and elevation explain AGB variation in secondary forest.•Structural diversity overrides the relative importance of functional diversity.•Knowing the relationship between biodiversity and ecosystem functioning is key to forest management.