Soil biota abundance supports ecosystem multifunctionality under carbon farming

Abstract Organic substrates from plants and animals are crucial for sustainable agriculture, yet their effects on agroecosystem multifunctionality remain underexplored at the global scale. Using a meta-analysis of 8509 field observations, we examined how plant-based carbon inputs (legume cover crops) and animal-based carbon inputs (vermicompost) influence nine ecological functions. Both carbon inputs significantly improved agroecosystem multifunctionality, with legume cover crops increasing it by 17% and vermicompost by 31%. These improvements were concentrated in supporting and provisioning services. Soil biota abundance was strongly linked to multifunctionality and showed more frequent win-win relationships with other functions than species richness. Across agroecosystems, soil biota abundance was primarily associated with local soil properties, followed by climate factors. Our findings highlight soil biota abundance as a community attribute complementary to species richness that contributes to agroecosystem multifunctionality. We further propose site-specific management strategies that align plant- and animal-based carbon inputs with local environmental conditions in global croplands to enhance multifunctionality.