Soil organic carbon dynamics in agroforestry systems across urban and peri-urban landscapes

Background Rapid urbanization and intensive land use have degraded environmental quality in metropolitan regions, increasing the need for management strategies that enhance climate resilience. Urban and peri-urban Agroforestry Systems (AFS) are promising nature-based solutions for carbon sequestration and soil restoration. Methods This study evaluated the carbon mitigation potential of AFS in the Belo Horizonte Metropolitan Region, Brazil. We analyzed total organic carbon (TOC), its physical fractions (Particulate Organic Matter – POM and Mineral-Associated Organic Matter – MAOM), and aggregate-associated carbon in three AFS and paired reference areas. Statistical analyses included comparisons between treatments and Principal Component Analysis (PCA), interpreted as an exploratory tool. Results AFS increased soil carbon stocks by an average of 44% compared to reference areas, with a mean sequestration rate of 10.7 Mg C ha⁻¹ yr⁻¹. The MAOM fraction showed consistent increases across depths, suggesting enhanced long-term carbon stabilization, while POM increases were more pronounced in surface layers. Aggregate-associated carbon did not show clear statistical differences, but a tendency of accumulation in macroaggregates at 10–20 cm depth was observed. PCA showed a separation pattern between AFS and reference sites, indicating an association of AFS with greater carbon accumulation, including at deeper layers. Conclusion Urban and peri-urban AFS are effective carbon sinks that enhance both the quantity and stability of soil organic carbon. These findings reinforce the role of AFS as crucial nature-based solutions for climate mitigation and sustainable planning in tropical metropolitan landscapes.