Soil organic carbon storage potential of Gerado watershed and its implication on climate change mitigation in the North-Eastern highlands of Ethiopia

Soils are key carbon sinks and play an important role in climate change mitigation, although their sequestration potential varies across landscapes due to differences in topography, land use, and vegetation. This study quantified soil organic carbon (SOC) stocks across four land-use types, three soil depths (0–10, 10–20, 20–30 cm), and two agroecological zones (midland and highland) in the Gerado watershed of northern Ethiopia, based on 72 soil samples. Three-way analysis of variance revealed significant variations in SOC among land uses, soil depths, and agroecological zones. Grazing lands stored the highest SOC (43.3 t/ha), followed by forests (33.6 t/ha), reflecting the influence of vegetation cover and manure inputs. SOC decreased consistently with soil depth due to lower organic matter inputs and higher bulk density in subsurface layers. Midland areas contained more SOC (32 t/ha) than highlands (25.4 t/ha), likely due to better vegetation cover and reduced erosion. The watershed stores 94.91 Gg of SOC in the upper 30 cm, equivalent to 348.32 Gg CO2 removed from the atmosphere, indicating meaningful climate change mitigation potential. These results indicate that sustainable grazing practices, forest conservation, and improved surface management, such as mulching and organic amendments, can enhance carbon storage and support local climate mitigation strategies. Targeted reforestation and erosion control in highland areas are recommended. Long-term monitoring is needed to evaluate SOC dynamics and optimize conservation strategies in the watershed.