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Biogeosciences An interactive open-access journal of the European Geosciences Union
doi:10.5194/bg-2017-12
© Author(s) 2017. This work is distributed
under the Creative Commons Attribution 3.0 License.
Research article
10 Mar 2017
Review status
This discussion paper is under review for the journal Biogeosciences (BG).
Temporal and spatial decoupling of CO2 and N2O soil emissions in a Mediterranean riparian forest
Sílvia Poblador1,*, Anna Lupon1,2,*, Santiago Sabaté1,3, and Francesc Sabater1,3 1Departament de Biologia Evolutiva, Ecologia i Ciències Ambientals (BEECA), Universitat de Barcelona. Av. Diagonal 643, 08028, Barcelona, Spain
2Department of Forest Ecology and Management, Swedish University of Agricultural Sciences (SLU). Skogsmarksgränd 17S, 90183, Umeå, Sweden
3CREAF. Campus de Bellaterra Edifici C, 08193, Cerdanyola del Vallès, Spain
*These authors contributed equally to the development of this work.
Abstract. Riparian zones play a fundamental role in regulating the amount of carbon (C) and nitrogen (N) that is exported from catchments. However, C and N removal via soil gaseous pathways can influence local budgets of greenhouse gases (GHG) emissions and contribute to climate change. Over a year, we quantified soil effluxes of carbon dioxide (CO2) and nitrous oxide (N2O) from a Mediterranean riparian forest in order to understand the role of these ecosystems on catchment GHG emissions. In addition, we evaluated the main soil microbial processes that produce GHG (mineralization, nitrification, and denitrification) and how changes in soil properties can modify the GHG production over time and space. Mediterranean riparian soils emitted large amounts of CO2 to the atmosphere (1.2–10 g C m−2  d−1), but were powerless sources of N2O (0.001–0.2 mg N m−2 d−1) due to low denitrification rates. Both CO2 and N2O emissions showed a marked (but antagonistic) spatial gradient as a result of variations in soil moisture across the riparian zone. Deep groundwater tables fueled large soil CO2 effluxes near the hillslope, while N2O emissions were higher in the wet zones adjacent to the stream channel. However, both CO2 and N2O emissions peaked after spring rewetting events, when optimal conditions of soil moisture, temperature, and N availability favor microbial respiration, nitrification, and denitrification. Overall, our results highlight the role of riparian soils as hotspots of GHG emissions, and suggest that future alterations in hydrologic regimes can affect the microbial processes that produce GHG as well as the contribution of these systems to climate change.

Citation: Poblador, S., Lupon, A., Sabaté, S., and Sabater, F.: Temporal and spatial decoupling of CO2 and N2O soil emissions in a Mediterranean riparian forest, Biogeosciences Discuss., doi:10.5194/bg-2017-12, in review, 2017.
Sílvia Poblador et al.
Sílvia Poblador et al.
Sílvia Poblador et al.

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This study quantified for the first time simultaneous rates of carbon dioxide (CO2) and nitrous oxide (N2O) from a Mediterranean riparian forest. Our results showed a strong linkage between riparian hydrology, soil microbial processes and greenhouse gas (GHG) emissions. High CO2 effluxes occurred all year long, while N2O emissions were generally low and confined to saturated soils. Overall, this study highlights that riparian soils can be hotspots of GHG emissions within Mediterranean catchments.
This study quantified for the first time simultaneous rates of carbon dioxide (CO2) and nitrous...
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