Sammanfattning
Three different models (STEP–GENDEC–
NOflux, Zhang2010, and Surfatm) are used to simulate
NO, CO2, and NH3 fluxes at the daily scale for 2 years
(2012–2013) in a semi-arid grazed ecosystem at Dahra
(152401000 N, 152505600W, Senegal, Sahel). Model results
are evaluated against experimental results acquired during
three field campaigns. At the end of the dry season, when the
first rains re-wet the dry soils, the model STEP–GENDEC–
NOflux simulates the sudden mineralization of buried litter,
leading to pulses in soil respiration and NO fluxes. The
contribution of wet season fluxes of NO and CO2 to the
annual mean is respectively 51% and 57 %. NH3 fluxes are
simulated by two models: Surfatm and Zhang2010. During
the wet season, air humidity and soil moisture increase,
leading to a transition between low soil NH3 emissions
(which dominate during the dry months) and large NH3
deposition on vegetation during wet months. Results show a
great impact of the soil emission potential, a difference in the
deposition processes on the soil and the vegetation between
the two models with however a close agreement of the total
fluxes. The order of magnitude of NO, NH3, and CO2 fluxes
is correctly represented by the models, as well as the sharp
transitions between seasons, specific to the Sahel region.
The role of soil moisture in flux magnitude is highlighted,
whereas the role of soil temperature is less obvious. The
simultaneous increase in NO and CO2 emissions and NH3
deposition at the beginning of the wet season is attributed
to the availability of mineral nitrogen in the soil and also
to microbial processes, which distribute the roles between
respiration (CO2 emissions), nitrification (NO emissions),
volatilization, and deposition (NH3 emission/deposition).
The objectives of this study are to understand the origin of
carbon and nitrogen compounds exchanges between the soil
and the atmosphere and to quantify these exchanges on a
longer timescale when only a few measurements have been
performed.
NOflux, Zhang2010, and Surfatm) are used to simulate
NO, CO2, and NH3 fluxes at the daily scale for 2 years
(2012–2013) in a semi-arid grazed ecosystem at Dahra
(152401000 N, 152505600W, Senegal, Sahel). Model results
are evaluated against experimental results acquired during
three field campaigns. At the end of the dry season, when the
first rains re-wet the dry soils, the model STEP–GENDEC–
NOflux simulates the sudden mineralization of buried litter,
leading to pulses in soil respiration and NO fluxes. The
contribution of wet season fluxes of NO and CO2 to the
annual mean is respectively 51% and 57 %. NH3 fluxes are
simulated by two models: Surfatm and Zhang2010. During
the wet season, air humidity and soil moisture increase,
leading to a transition between low soil NH3 emissions
(which dominate during the dry months) and large NH3
deposition on vegetation during wet months. Results show a
great impact of the soil emission potential, a difference in the
deposition processes on the soil and the vegetation between
the two models with however a close agreement of the total
fluxes. The order of magnitude of NO, NH3, and CO2 fluxes
is correctly represented by the models, as well as the sharp
transitions between seasons, specific to the Sahel region.
The role of soil moisture in flux magnitude is highlighted,
whereas the role of soil temperature is less obvious. The
simultaneous increase in NO and CO2 emissions and NH3
deposition at the beginning of the wet season is attributed
to the availability of mineral nitrogen in the soil and also
to microbial processes, which distribute the roles between
respiration (CO2 emissions), nitrification (NO emissions),
volatilization, and deposition (NH3 emission/deposition).
The objectives of this study are to understand the origin of
carbon and nitrogen compounds exchanges between the soil
and the atmosphere and to quantify these exchanges on a
longer timescale when only a few measurements have been
performed.
| Originalspråk | engelska |
|---|---|
| Sidor (från-till) | 2049-2077 |
| Tidskrift | Biogeosciences |
| DOI | |
| Status | Published - 2019 maj 19 |
Ämnesklassifikation (UKÄ)
- Naturgeografi
