Potential of crop-livestock integration to enhance carbon sequestration and agroecosystem functioning in semi-arid croplands

While characteristics of semi-arid climates place limitations on soil organic carbon (SOC) storage, there is opportunity and urgency for increasing the quality and long-term persistence of cropland SOC content within these agroecosystems. Livestock re-integration into cropland shows potential to improve semi-arid agroecosystem functioning through shifts in biogeochemical processes and the facilitation of multiple ecosystem services involved in carbon and nutrient cycling and use-efficiency. Here we review the characteristics of grazing-based Integrated Crop-Livestock (ICL) systems and how various associated management practices may interplay with semi-arid agroecological and biogeochemical dynamics to influence soil microbial ecology and SOC accumulation and stabilization. We argue that livestock re-integration holds notable potential to increase cropland SOC through controls on landscape net primary productivity, allocation of biomass belowground, efficient recycling of residual crop nutrients, and soil biological activity related to a suite of soil ecosystem services. Achieving the full SOC accumulation potential of ICL management will require site-specific consideration of feedbacks between herbivory, soil microbial ecology, soil disturbance, and forage species interactions. Future research should focus on optimizing plant-soil-grazer feedbacks and understanding of mechanistic drivers of ICL system outcomes to optimize the design and management of semi-arid regional ICL systems for enhanced SOC quality and persistence.