How soil biota regulate C cycling and soil C pools in diversified crop rotations

Agricultural intensification has substantially reduced soil biodiversity as well as agroecosystem functions and services. Sustainable agroecosystems that increase crop diversity through rotation may promote soil biodiversity and above-belowground interactions. Studying ecological networks, soil communities, and abiotic impacts simultaneously increases our understanding of complex C cycling encompassing all components of a given system. Higher rotational diversity enhances primary productivity by increasing the photosynthetic intensity of crops in rotation relative to systems where a given crop is grown continuously. In addition, greater temporal crop diversity stimulates above-belowground interactions, which affects carbon allocation, rhizodeposition, and the growth of rhizobiomes. Stronger above-belowground interactions will intensify ecological connections between microbial and faunal networks among roots, rhizosphere, and bulk soil. This further strengthens soil functions and interactions between networks of biotic elements (plant inputs and soil food web functioning) and abiotic factors (soil matrix and microenvironments), providing positive feedback loops on soil organic C accrual. This review describes how interactions between rotational and biological diversity drive biodiversity-function relationships. By increasing the quantity, quality, and chemical diversity of C inputs, crop rotations with higher functional diversity foster soil communities and enhance biotic-abiotic interactions, with positive impacts on the formation and storage of soil organic matter.