26 Oct 2023
 | 26 Oct 2023
Status: this preprint is open for discussion.

Modelling CO2 and N2O emissions from soils in silvopastoral systems of the West-African Sahelian band

Yélognissè Agbohessou, Claire Delon, Manuela Grippa, Eric Mougin, Daouda Ngom, Espoir Koudjo Gaglo, Ousmane Ndiaye, Paulo Salgado, and Olivier Roupsard

Abstract. Silvopastoral systems (SPSs) have been shown to improve ecosystem resilience and provide sustainable land management solutions in the Sahel. However, accurately estimating the contribution of Sahelian ecosystems to the overall greenhouse gas (GHG) balance is a challenge, in particular the magnitude of carbon dioxide (CO2) and nitrous oxide (N2O) emissions from soils. In this work, we spatialized and applied the process-based model STEP-GENDEC-N2O to investigate the magnitude, spatial, and temporal patterns of herbaceous mass, as well as CO2 and N2O emissions from soil in Sahelian SPSs. Our results show that over the last decade (2012–2022), there was a heterogeneous spatial distribution of herbaceous mass production, as well as of soil CO2 and N2O emissions in Sahelian SPSs. Spatial variations in soil CO2 emissions are primarily controlled by soil carbon content, temperature, herbaceous mass, and animal load, while soil nitrogen content, soil water content, and animal load are the main factors driving the spatial variations in N2O emissions from soil. The estimated CO2 and N2O emissions from soil in Sahelian SPSs over the 2012–2022 period were equal to 58.79 ± 4.83 Tg CO2-C yr-1 (1 Tg = 1012 g) and 21.59 ± 3.91 Gg N2O-N yr-1 (1 Gg = 109 g), respectively. These values are generally lower than estimates reported in the literature for tropical areas and croplands. Furthermore, our simulations indicated a significant annual rising trend of soil CO2 and N2O emissions between 2012–2020 as herbaceous mass increases, making more C and N available for nitrification, denitrification and decomposition processes. By mapping soil CO2 and N2O emissions, we provide crucial insights into the localization of emission hotspots in Sahelian SPSs, thereby offering valuable information that can be used to devise and implement effective strategies aimed at fostering carbon sequestration in the Sahel. 

Yélognissè Agbohessou et al.

Status: open (until 27 Dec 2023)

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Yélognissè Agbohessou et al.

Model code and software

2D model STEP-GENDEC-CN Yélognissè Agbohessou, Claire Delon, Manuela Grippa, Eric Mougin, Olivier Roupsard

Yélognissè Agbohessou et al.


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Short summary
Emissions of greenhouse gases in the Sahel are not well represented, because considered as weak compared to the rest of the world. However, natural areas in the Sahel emit carbon dioxide and nitrous oxides which need to be assessed because of extended surfaces. We propose an assessment of such emissions in Sahelian silvopastoral systems, and how they are influenced by environmental characteristics. These results are essential to inform on climate change strategies in the region.