Carbon stocks and yields in smallholder cocoa agroforestry systems along a climatic gradient in Ghana

Abstract Cocoa agroforestry systems are recognized for their potential to reconcile agricultural production with climate change mitigation, yet the mechanisms governing carbon storage across environmental gradients remain poorly understood. Here, we examined above- and belowground carbon stocks of cocoa and shade trees as well as soil organic carbon (SOC) in smallholder cocoa agroforestry systems across dry, intermediate (mid), and wet climatic zones in Ghana. Despite pronounced differences in shade tree density, size, and species richness, shade-tree aboveground carbon stocks (108–147 Mg C ha −1 ) as well as total farm-level carbon stocks were comparable across the climatic gradient (from dry to wet), with no negative effect on cocoa yield, signifying trade-offs in the structural characteristics of shade trees driven by management. Cocoa tree carbon and SOC stocks varied across the climatic zones but individually contributed less to ecosystem carbon stocks. Cocoa tree carbon stocks were highest in the mid climatic zone (41 Mg C ha −1 ) compared to 22 Mg C ha −1 for the dry and 27 Mg C ha −1 for the wet zone, reflecting the older cocoa tree stands and larger stem diameters of the mid zone. SOC was lower in the dry zone than in the mid and wet zones, by 23 and 27%, respectively, and mirrored the combined effects of climatic conditions and soil properties. The ratio of cocoa yield to total plant carbon increased from the dry to wet climatic zone, indicating a shift in carbon allocation toward productivity under wetter climatic conditions. Our results highlight the capacity of cocoa agroforestry systems to provide climate-mitigation benefits independent of climatic variations but with greater synergies of achieving high cocoa productivity and ecosystem carbon storage under wetter climatic conditions. Overall, these findings underscore the need for climate-specific management strategies that optimizes both carbon sequestration and cocoa productivity in West African agroforestry systems.