Effect of land-use types and slope gradients on soil organic carbon stocks in the Shabo Kalo micro-watershed, Lalo Kile district, Western Ethiopia

The purpose of this study was to examine how different land-use types and slope gradients influence soil organic carbon stock (SOCS) in the study area. The relationship between land-use categories and environmental change is of particular importance, as soils play a critical role in sequestering and storing atmospheric CO 2 , thereby contributing to climate change mitigation. To achieve this objective, soil samples were collected from four slope classes that were purposively stratified within each land-use type to assess the combined effects of land use and slope on SOCS. Soil samples were collected from 12 plots (10 m × 10 m) using a diagonal sampling approach with three replications. Undisturbed soil samples were obtained using a core sampler to determine bulk density across land-use types and slope gradients. In addition, 36 disturbed soil samples were collected from a depth of 0–30 cm using an auger to analyze SOCS at the watershed scale. The results indicated that both slope gradient and land-use type had a significant effect on SOCS. The highest SOCS value (71.3 Mg ha −1 ) was recorded on gentle slopes under forest land, whereas the lowest value (29.8 Mg ha −1 ) was observed on steep slopes under grazing land. In terms of carbon dioxide equivalents, one hectare of forest land soil sequestered 250.29 Mg CO 2 ha −1 , which was substantially higher than that of grazing land (195.98 Mg CO 2 ha −1 ) and cultivated land (127.35 Mg CO 2 ha −1 ) within the 0–30 cm soil depth. The findings of this study contribute to raising awareness among local farmers, relevant government institutions, and non-governmental organizations about the importance of sustainable land use and soil management practices for climate change mitigation.