Drivers and vertical CO 2 flux balances in a Sahelian agroforestry system: Insights from high frequency measurements

Agroforestry systems – combining trees with crops and/or livestock – are increasingly promoted as sustainable and climate-resilient land-use strategies. Despite their widespread presence in the Sahel, experimental data on their potential as carbon sinks are scarce. This study presents a full-year, high-frequency dataset of CO 2 fluxes in a Sahelian agro-silvo-pastoral parkland dominated by Faidherbia albida , located in Senegal's groundnut basin. CO 2 fluxes were continuously measured using automated dynamic chambers, allowing the quantification of soil and crop respiration (Rch), gross primary production (GPPch), and net carbon exchange ( F CO 2 ch) under both full sun and shaded (under tree canopies) environments. Seasonal patterns of CO 2 fluxes were similar in both environments, with peaks during the rainy season. Rch and GPPch were significantly higher under tree canopies, indicating a “fertile island” effect. CO 2 flux variability was primarily driven by soil moisture and leaf area index. Chamber-based GPP estimates closely matched those from Eddy Covariance measurements. On an annual scale, F. albida trees contributed approximately 23 % of total ecosystem GPP, with a carbon use efficiency of 0.48. Net annual vertical CO 2 exchange was estimated at −1.4 ± 0.46 and −1.8 ± 0.17 Mg C-CO 2 ha −1 using chamber and Eddy Covariance methods, respectively. These findings underscore the role of F. albida -based agroforestry systems as effective carbon sinks in Sahelian landscapes, supporting their potential contribution to climate change mitigation.