Species mixing promotes plant biomass accumulation and nutrient cycling in forest plantations

Mixed-species plantations have been increasingly promoted as a strategy to enhance ecosystem functioning and related ecosystem processes; however, their global impacts on biomass production and nutrient cycling remain uncertain. Here we present a comprehensive meta-analysis based on a random-effects model of 8,450 paired observations from 328 studies spanning diverse climatic zones, stand structures, and silvicultural systems. We demonstrate that species mixing significantly enhances plant biomass and nutrient content compared to monocultures, with positive responses observed across trees, shrubs, litterfall, and both above- and belowground compartments. Mixed-species plantations also increase soil organic carbon, total nitrogen, phosphorus availability, microbial biomass, and leaf nutrient content while maintaining stable soil stoichiometric ratios, collectively reflecting more efficient stand-level nutrient cycling. Importantly, the magnitude of these effects was shaped by climatic and structural contexts, with stronger positive outcomes under warmer and wetter climates, increasing with species richness, and showing unimodal responses to elevation, stand age, and stand density. By synthesizing multi-scale evidence from diverse ecosystems, we reveal that species mixing promotes biomass accumulation, improves nutrient retention, and strengthens biodiversity-nutrient cycling linkages. This study highlights the potential of mixed-species plantations to enhance ecological function, advance forest restoration, and guide plantation management across diverse environmental conditions.