Long term observations of carbon dioxide exchange over cultivated savanna under a Sudanian climate in Benin (West Africa)

•Eddy-covariance measurements were made above savanna during 29 months.•Moisture was found the main controlling factor of all ecosystem's dynamic.•TER was mainly driven by the soil moisture, but insensitive to temperature.•Site was annually a C sink of 232±27gCm−2, more efficient during wet season.