Environmental Science: Water Science and Technology
; Earth and Planetary Sciences: Earth-Surface Processes
; Environmental Science: Environmental Chemistry
英文摘要:
The alternating between dry and wet seasons and the consecutive microbial responses to soil water content in semiarid ecosystems has significant consequences on nitrogen exchanges with the atmosphere. Three field campaigns were carried out in a semi arid sahelian rangeland in Dahra (Ferlo, Senegal), two at the beginning of the wet season in July 2012 and July 2013, and the third one in November 2013 at the end of the wet season. The ammonia emission potentials of the soil ranged from 271 to 6628, indicating the soil capacity to emit NH3. The ammonia compensation point in the soil ranged between 7 and 150 ppb, with soil temperatures between 32 and 37 �C. Ammonia exchange fluctuated between emission and deposition (from −0.1–1.3 ng N.m−2s−1), depending on meteorology, ambient NH3concentration (5–11 ppb) and compensation point mixing ratios. N2O fluxes are supposed to be lower than NO fluxes in semi arid ecosystems, but in Dahra N2O fluxes (5.5 � 1.3 ng N m−2s−1in July 2013, and 3.2 � 1.7 ng N m−2s−1in November 2013) were similar to NO fluxes (5.7 � 3.1 ng N m−2s−1in July 2012, 5.1 � 2.1 ng N m−2s−1in July 2013, and 4.0 � 2.2 ngN m−2s−1in November 2013). Possible reasons are the influence of soil moisture below the surface (where N2O is produced) after the beginning of the wet season, the potential aerobic denitrification in microsites, the nitrifier denitrification, and nitrification processes. The presence of litter and standing straw, and their decomposition dominated N compounds emissions in November 2013, whereas emissions in July 2012 and 2013, when the herbaceous strata was sparse, were dominated by microbial processes in the soil. CO2respiration fluxes were high in the beginning (107 � 26 mg m−2h−1in July 2013) and low in the end of the wet season (32 � 5 mg m−2h−1in November 2013), when autotrophic and heterotrophic activity is reduced due to low soil moisture conditions These results confirm that contrasted ecosystem conditions due to drastic changes in water availability in semi arid regions have important non linear impacts on the biogeochemical nitrogen cycle. � 2017 Elsevier Ltd
Laboratoire d'A�rologie, Universit� de Toulouse, CNRS, UPS, France; INRA, UMR Ecosys INRA-AgroParisTech, Universit� Paris-Saclay, Thiverval-Grignon, France; Institut des Sciences de l'Environnement, Universit� Cheikh Anta Diop, Dakar, Senegal; Centre de Recherche Zootechnique, ISRA, Dahra, Senegal; Department of Geosciences and Natural Resource Management, University of Copenhagen, Denmark; CESBIO, Universit� de Toulouse, CNRS, UPS, CNES, IRD, Toulouse, France; Geosciences Environnement Toulouse, Universit� de Toulouse, CNRS, UPS, CNES, IRD, France
Recommended Citation:
Delon C,, Galy-Lacaux C,, Ser�a D,et al. Soil and vegetation-atmosphere exchange of NO, NH3, and N2O from field measurements in a semi arid grazed ecosystem in Senegal[J]. Atmospheric Environment,2017-01-01,156