Analysing Carbon Stock Variability and Sequestration Potential in Nigerian Derived Savanna Woodlands

Derived savanna woodlands occupying the transition zone between the Guinea Savanna and lowland rainforest in south-central Nigeria represent an underappreciated carbon reservoir whose quantification is essential for Nigeria's national carbon accounting and REDD-plus programme implementation across the North Central and South West geopolitical zones. This study analyses the spatial variability of aboveground carbon stocks and estimates net carbon sequestration potential across derived savanna woodlands in Kwara, Niger, and Ogun States using field biomass inventory data, allometric equations, and remote sensing-assisted carbon mapping. Systematic forest inventory plots (30 metres by 30 metres) were established at 72 locations across the three states, recording species composition, stem diameter, and height for all woody stems above 10 centimetres diameter at breast height. Aboveground biomass was calculated using the Chave et al. pantropical allometric equation incorporating wood density, and converted to carbon equivalent using the 0.47 factor. Random forest regression modelling was applied in Google Earth Engine to upscale plot-level carbon estimates across the study area using Sentinel-2 spectral bands and Landsat-derived vegetation indices as predictor variables. Results reveal mean aboveground carbon stocks of 38.6 Mg C per hectare across the study area, with the highest densities in riparian gallery forest patches and lowest densities on heavily grazed savanna margins. Total estimated aboveground carbon in the study area is 14.8 million Mg C, with an estimated annual net sequestration potential of 820,000 Mg CO2 equivalent under a conservation scenario. The study provides the first high-resolution carbon density map for Nigerian derived savanna woodlands. Keywords: carbon stocks, derived savanna, remote sensing, sequestration, Nigeria.