Geospatial Estimation of Sequestered Carbon in Soils and Vegetation of Some Forest Reserves in South-West Nigeria

Abstract

Carbon sequestration is essential for improvement of soil health and climate change mitigation. However, unsustainable land use and forest exploitation have negatively influenced carbon stability in tropical ecosystems. This study was conducted to quantify carbon stocks in soils and the vegetations of Omo Forest Reserve (OFR) and Gambari Forest Reserve (GFR), in Southwestern Nigeria, using geospatial tools. Two soil orders (Alfisol and Inceptisol) and three land use types were examined through detailed soil profile characterisation and classification under USDA Soil Taxonomy, WRB, and Local Series systems. Soil carbon was estimated using Batjes’ method, while vegetation biomass and carbon were derived from NDVI and biomas-carbon conversion factors. A higher soil carbon was obtained in OFR (1065.77 g C/m²) than GFR (842.44 g C/m²). Also, substantially greater vegetation biomass and carbon were found in OFR (215.37 Mg/ha and 107.69 Mg/ha) compared to GFR (22.16 Mg/ha and 11.08 Mg/ha). Although differences across soil types and horizons were not statistically significant, bulk density and horizon thickness enhanced carbon sequestration in the sub-surface horizons with Omo Forest Reserve having better carbon sequestration due to high healthy vegetation cover. This finding underscores the urgent need for policies that curb anthropogenic pressures, strengthen forest conservation, and integrate carbon accounting into sustainable land management strategies in Sub-Saharan Africa.