Climate-dependent pedogenic trajectories control the carbon sequestration potential of agricultural terraces

Agricultural terraces, being among the most common man-made landforms, are known to significantly impact soil organic carbon (SOC). However, the direction and magnitude of this impact remain unclear. By integrating field observations from 14 sites across Europe with global data synthesis, we demonstrate that the magnitude of terracing-driven SOC sequestration is controlled by climate-dependent pedogenic trajectories, which determine fresh SOC inputs and mineralogical capacity of terraced soils to stabilize C. In humid terraces, excess moisture favors plant productivity and fresh SOC input, allowing for the recovery of lost topsoil C after terrace construction. Higher moisture availability also enhances mineral weathering and production of reactive mental oxides, facilitating the preservation of buried SOC within terraces. Consequently, terrace landforms consistently have higher SOC stock than non-terraced controls. Under arid climates, this effect is significantly smaller and can even be negative owing to moisture limitations on fresh C inputs and mineral weathering, thereby limiting SOC recovery and preservation. Terraced soils in arid climate are enriched highly crystalline oxides and base cations, which inadequately stabilizing buried SOC stock within terraces. Future terrace engineering should consider soil types, terracing structures and proper management practices to ensure the efficiency of runoff harvesting, land productivity and SOC sequestration potential.