Evaluation of Chamber-based soil greenhouse gas emissions in contrasted land use of the Sudanian savanna

The effects of major greenhouse gas (GHG) emissions in West Africa remain insufficiently documented. Over two consecutive years, we monitored soil GHG emissions using a chamber-based experimental setup across four contrasting land management conditions in the Sudanian savanna. The environmental drivers of the emissions were assessed through stepwise linear regression and ANOVA statistical tests. Our results show that, regardless of land management conditions, N₂O release occurs at the highest rate in rice fields (4.29±2.9 µg N m^-2 h^-1). The soil acts as a sink for CH₄ in the forest reserve (-1.09±7.67 µg C m^-2 h^-1), whereas degraded lands, such as cropland and rainfed rice farms, exhibit CH₄ release at rates of 1.03±13.1 µg C m^-2 h^-1 and 5.93±12.28 µg C m^-2 h^-1, respectively. Livestock breeding contributes significantly to CH₄ emissions in grasslands, where the annual mean CH₄ flux is the highest (16.79±6.69 µg C m^-2 h^-1). The statistical analysis indicates that 53.8% and 50.2% variability in the CH₄ flux is explained by soil moisture and soil temperature respectively in the grassland and rice field. Soil moisture is negatively correlated with N₂O release, while the relationship with CH₄ is positive in grassland and rice fields, where higher CH₄ emissions are observed. N₂O flux shows a positive correlation with soil temperature. These findings suggest that land degradation exacerbates CH₄ emissions, and the effect of fertilizer use on biomass during the growing season increases CH₄ release in rice fields by approximately threefold. At the peak of the raining season, the forest CH₄ sink reaches the highest -6.08±14.7 µg C m^-2 h^-1 while the rainfed rice field releases 9.14±29.57 µg C m^-2 h^-1. Overall, there is intra annual variability of GHG fluxes with dry and wet years showing different magnitude of N₂O and CH₄ emissions. The patterns of GHG flux dynamics in this data-scarce region is better clarified through our investigation. We conclude that GHG emissions in response to land cover degradation and agricultural practices, such as fertilizer use, are significant in the Sudanian savanna and urgent decisions are needed to mitigate these effects.