Important role of Fe oxides in global soil carbon stabilization and stocks

Iron (Fe) oxides can interact with soil organic carbon (SOC) to form Fe-bound organic carbon (OC-Fe), which strongly promotes SOC protection, mitigating global climate change. However, the global patterns and factors controlling OC-Fe are unclear. Here, we conducted a meta-analysis of 3,395 globally distributed soil profiles to reveal the role of Fe-Al oxides in global soil carbon stabilization and stocks. The global OC-Fe stock in topsoil is 233 PgC, accounting for 33 ± 15% of the total SOC stock. A substantial OC-Fe deficit (difference between OC-Fe and OC-Fe_max) was observed at the equator and at mid-latitudes. Our findings suggest that mineral factors should be incorporated into soil carbon models to improve model predictions. Although there are uncertainties in current OC-Fe extraction method, the global distribution of OC-Fe and OC-Fe_max constitutes a vital resource for future research targeting carbon cycling issues and offers innovative strategies for global soil carbon sequestration initiatives.