Carbon Sequestration Potential of Parkland Agroforestry Systems in the Guinea Savanna Zone of Northern Nigeria

Parkland agroforestry systems, characterised by the retention of scattered trees on cropland, constitute the dominant land management system across the Guinea savanna zone of northern Nigeria and represent an undervalued component of national carbon accounting. This study quantifies the above-ground and below-ground carbon sequestration potential of parkland agroforestry across three states in the Guinea savanna belt (Kaduna, Niger, and Kwara) and identifies tree species and management factors that maximise carbon storage. Above-ground biomass of parkland trees was measured using species-specific allometric equations validated through destructive sampling of 45 trees across the study area. Below-ground carbon was estimated using root-to-shoot ratios from regional studies. Soil organic carbon was measured at multiple depths in paired parkland and treeless crop plots. Tree density, species composition, and farmer management intensity were recorded through household surveys and field census. Mean tree density across the study area was 12.4 trees per hectare, with Vitellaria paradoxa and Parkia biglobosa as the two most abundant species. Above-ground carbon stocks averaged 8.3 tonnes of carbon per hectare in parkland plots versus 1.1 tonnes in treeless controls. Soil organic carbon was 23% higher in parkland top soils. Total carbon sequestration potential under intensified parkland management was estimated at 4.2 tonnes of carbon per hectare per year. Certification of parkland agroforestry under voluntary carbon markets is recommended as a co-benefit incentive for farmers. Keywords: parkland agroforestry, carbon sequestration, Guinea savanna, Vitellaria paradoxa, northern Nigeria