Drivers and CO2 flux budgets in a Sahelian Faidherbia albida agro-silvo-pastoral parkland: Insights from continuous high-frequency soil chamber measurements and Eddy Covariance

Abstract

Abstract. 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 CO₂ fluxes in a Sahelian agro-silvo-pastoral parkland dominated by F. albida, located in Senegal’s groundnut basin. CO₂ fluxes were continuously measured using automated static chambers, allowing the quantification of soil and crop respiration (Rch), gross primary production (GPPch), and net carbon exchange (FCO₂ch) under both full sun and shaded (under tree canopies) environments. Seasonal patterns of CO₂ 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. CO₂ 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 50 % of total ecosystem GPP, with a carbon use efficiency of 0.48. Net annual CO₂ exchange was estimated at −1.4 ± 0.02 and −1.8 ± 0.01 Mg C-CO₂ 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.