Modelling Soil Organic Carbon Dynamics Under Climate Change Scenarios in the Guinea Savanna of Plateau State, North Central Nigeria

This study applies the RothC soil carbon model to project soil organic carbon dynamics under current management and projected climate change scenarios in the guinea savanna zone of Plateau State, located in Nigeria's North Central geopolitical zone. Climate change is predicted to alter temperature and rainfall patterns in the Middle Belt, potentially accelerating soil organic matter decomposition and soil carbon loss, yet model-based projections of carbon dynamics under Nigerian climate change scenarios are essentially absent from the literature. Using calibration datasets from long-term experimental plots at the University of Agriculture Makurdi and the National Root Crops Research Institute, the RothC model was parameterised for guinea savanna conditions using climate, soil texture, and land management inputs. Soil organic carbon and radiocarbon measurements from archived samples were used for model validation. Projection scenarios included baseline current management, improved management with ISFM, and two RCP climate scenarios (RCP 4.5 and RCP 8.5) from CMIP6 model outputs downscaled to Plateau State. Findings revealed that under current management and RCP 8.5 warming, soil organic carbon would decline by an additional 18 percent by 2050 relative to stable climate projections, driven primarily by increased respiration under elevated temperature. ISFM management scenarios partially offset projected carbon losses, with organic input addition and reduced tillage together limiting net loss to 7 percent under the same warming scenario. The study provides the first RothC-based soil carbon projection framework for the North Central zone and recommends urgency in implementing organic matter restoration in the face of projected climate impacts. Keywords: RothC model, soil organic carbon, climate change, guinea savanna, Plateau State.