Enhancing the understanding of carbon storage based on Pentaclethra macrophylla Benth. and Acacia auriculiformis A. Cunn. agroforestry system in Congo Basin

Agroforestry systems (AFS) offer valuable ecological services and multifunctionality, yet there are gaps regarding interactions between tree species (particularly native ones) and food crops in the early stages of AFS across the Congo Basin. Acacia auriculiformis (exotic), and Pentaclethra macrophylla (native) are among the tree species grown in association with food crops in the Congo Basin. However, the knowledge of the carbon storage of these systems is limited, which would encourage their adoption. This study assessed the above-ground carbon (AGC) and soil organic carbon stock (SOCS) in AFS involving A. auriculiformis and P. macrophylla intercropped with cassava, maize, and peanut food crops. Research was conducted in the Lobilo watershed using a multifactorial design with two tree species, four planting densities (T1: 2500 trees × ha^-1, T2: 625 trees × ha^-1, T3: 278 trees × ha^-1; and T0: monoculture), and three intercrops (cassava, maize and peanut). Tree diameter at breast height (DBH) was measured at 1.3 m above the ground and recorded per plot, then integrated into allometric equations to estimate biomass and AGC. Soil samples were collected at 30 cm depth to determine SOCS. Data was analyzed using a mixed-effect model. Results revealed that A. auriculiformis stores more AGC than P. macrophylla. In addition, the planting density of 625 trees × ha^-1 and peanut food crops favored AGC sequestration over other planting densities and food crops. Regarding SOCS, agroforestry plots store more carbon than monocropping. Hence, A. auriculiformis intercropped with food crops improve carbon storage at the first stage while P. macrophilla, the local species, required more time to perform this flux. These findings have important policy implications for sustainable land use and climate adaptation in the Congo Basin. This study supports the integration of tailored agroforestry systems into national climate-smart agriculture strategies and land restoration policies. We recommend that policymakers promote agroforestry practices that include these species-particularly at a density of 625 trees × ha^-1 intercropped with peanuts-as viable options to enhance carbon storage, improve food production, and reduce the deforestation pressure caused by slash-and-burn agriculture.