Plant richness and functional traits drive ecosystem multifunctionality in Andean alder plantations

Introduction Restoration strategies may modify plant diversity and functional traits and thereby influence how ecosystems perform multiple functions. Objective To determine whether plant richness and functional traits drive ecosystem multifunctionality in protected monospecific Andean alder plantations. Methods Plant richness and functional traits were quantified in both Alnus acuminata plantations and naturally regenerated secondary forests. By sampling ecosystem functions, we derived an index of ecosystem multifunctionality. We then compared plant richness, traits, ecosystem functions, and multifunctionality between plantations and secondary forest stands using t‐test analyses and related the plant richness and functional traits to multifunctionality and ecosystem functions using a generalized linear model. Results We found a high plant richness and plant height kurtosis in the Andean alder plantation; however, specific leaf area (SLA) and plant height mean and variance were lower in the plantation than in the secondary forest. The alder plantation stands exhibited greater multifunctionality, litter stock, and soil phosphorus than the secondary forest stands. Although plant richness and functional traits were related to ecosystem functions and multifunctionality, the relationships varied between restoration strategies. The Andean alder plantation showed increased ecosystem multifunctionality with plant richness, SLA kurtosis, and positive SLA skewness. Conclusion As a pioneer nitrogen‐fixing species, A. acuminata creates specific habitat conditions that shape a plant community with a distinct functional trait composition. This unique assemblage promotes ecosystem multifunctionality using niche complementarity and the mass‐ratio effect, resulting in a pathway that differs from that of secondary forests.