Nitrogen-fixing trees increase organic carbon sequestration in forest and agroforestry ecosystems in the Congo basin

Experimental evidence on the effects of introducing nitrogen-fixing trees (NFTs) in forests and agroforestry systems on soil properties, crop yields, carbon (C) sequestration, and other ecosystem services in the Congo basin is scarce. A systematic literature review was conducted to study the effects of integrating NFTs in forests and agroforestry systems on tree biomass carbon stocks, soil properties (i.e., soil organic C (SOC), N, P, CEC, C:N ratio), crop yields and other ecosystem services; and examine their contribution to the objectives of 4 per 1000 Initiative. Electronic search engines (Google, Google Scholar) were searched focusing on Acacia auriculiformis-based agroforestry in the Democratic Republic of Congo (DRC) and Acacia mangium-based forestry in Republic of the Congo (RoC). This study suggests that integrating NFTs in both agricultural and forest landscapes in the Congo basin (DRC and RoC) improves the soil health through C sequestration and nutrient restoration relative to tropical savannas. This practice also generates other ecosystem services (i.e., pulp and fuelwood energy supply, poles for electricity network, food availability, land restoration). Integrating NFTs in forest and agroforestry ecosystems could therefore improve soil health and food security, mitigate climate change, and hence promote the objectives of 4 per 1000 Initiative.