EGU22-4337, updated on 23 May 2022
https://doi.org/10.5194/egusphere-egu22-4337
EGU General Assembly 2022
© Author(s) 2022. This work is distributed under
the Creative Commons Attribution 4.0 License.

Monitoring soil greenhouse gas (GHG) emissions in a Sahelian agrosilvo-pastoral parkland

Seydina Mohamad Ba1,2, Olivier Roupsard2,3,4, Lydie Chapuis-Lardy2,5, Frédéric Bouvery6, Djim Mouhamadou Lamine Diongue7, Yélognissè Frédi Agbohessou2, Frédéric Guérin8, Håkan Torbern Tagesson9,10, Bienvenu Sambou1, and Dominique Serça11
Seydina Mohamad Ba et al.
  • 1ISE, Université Cheikh Anta Diop, Dakar, Senegal (seydina.ba@ird.fr)
  • 2LMI IESOL, Centre IRD-ISRA de Bel Air, BP1386, CP18524, Dakar, Senegal
  • 3CIRAD, UMR Eco&Sols, BP1386, CP18524, Dakar, Senegal
  • 4UMR Eco&Sols, Univ Montpellier, CIRAD, INRAE, IRD, Institut Agro Montpellier, Montpellier, France
  • 5IRD, UMR Eco&Sols, Université de Montpellier-Cirad-INRAE-IRD-Institut Agro Montpellier, Montpellier, France
  • 6INRAE, UR PSH, Avignon, France
  • 7Département de Géologie, Université Cheikh Anta Diop, Dakar, Senegal
  • 8IRD, UMR GET, CNRS-IRD-Université Toulouse 3-CNES, Toulouse, France
  • 9Department of Physical Geography and Ecosystem Science, Lund University, Lund, Sweden
  • 10Department of Geosciences and Natural Resource Management, University of Copenhagen, Copenhagen, Denmark
  • 11LAERO, Université de Toulouse, CNRS, IRD, UT3, Toulouse, France

Estimates of greenhouse gas (GHG) emissions from soil are essential to understand possible climate change mitigation from ecosystems. There is currently very limited and reliable information on GHG emission factors for most land-use types of Sahelian Africa. GHG (CO2, H2O, CH4, N2O) and ammonia (NH3) emissions were measured in a Sahelian agro-silvo-pastoral parkland dominated by Faidherbia albida trees (Niakhar, Senegal) using 8 automatic chambers coupled to a Picarro G2508 gas analyser. The measurements were carried out in 2021 covering the late dry season (bare soil), the full rainy season (with groundnut plants in the chambers) and the beginning of the next dry period (senescent vegetation and bare soil). The chamber-based CO2 fluxes were compared to the Net Ecosystem Exchange of CO2 (NEE) as measured by a 4.5m-eddy covariance tower (below tree crowns) installed over the same agro-silvo-pastoral field. To avoid small scale heterogeneity, we compared here EC fluxes with chamber measured fluxes far from the Faidherbia albida area of influence. Indeed, for a given day, soil CO2 respiration is significantly higher under trees (shade) than far from trees (full sun) due to trees ‘island effect’ (p<0.0001).

Soil CO2 respiration was very low at the end of the dry season, with an average of about 0.6 µmol CO2 m-2 s-1. During the wet season, the maximum soil respiration at night was about 5 µmol CO2 m-2 s-1 and  the  maximum  net  CO2  uptake  during  the  day  was  around -6 µmol CO2 m-2 s-1. Only negligible fluxes of CH4, N2O and NH3 were recorded for all seasons. The low N2O fluxes could be related to low soil fertility and lack of nitrogen supply, and low soil moisture in these sandy soils does not favor soil gas production processes for both N2O and CH4. The CO2 fluxes from the automatic chambers showed similar typical semi-arid ecosystem patterns as that of the EC tower. We saw large emission peaks during the first rain events of the rainy season, positive and negative fluxes at night and day, respectively, high fluxes when the soil was wet, and decay during the next dry season. However, in average the soil CO2 respiration magnitude of the chambers with groundnut plant were much lower (1.26 µmol CO2 m-2 s-1) than the ecosystem respiration as seen from the EC tower (3.74 µmol CO2 m-2 s-1), and the difference was even worse for diurnal net CO2 uptake (by a factor of 7).

How to cite: Ba, S. M., Roupsard, O., Chapuis-Lardy, L., Bouvery, F., Diongue, D. M. L., Agbohessou, Y. F., Guérin, F., Tagesson, H. T., Sambou, B., and Serça, D.: Monitoring soil greenhouse gas (GHG) emissions in a Sahelian agrosilvo-pastoral parkland, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4337, https://doi.org/10.5194/egusphere-egu22-4337, 2022.

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