EGU22-5707
https://doi.org/10.5194/egusphere-egu22-5707
EGU General Assembly 2022
© Author(s) 2022. This work is distributed under
the Creative Commons Attribution 4.0 License.

Elucidating soil pore N2O production and consumption processes using isotope and microbial gene analysis: A depth profile approach

Luisa I. Minich1,2, Matti Barthel3, Rafaela F. Conz3, Roman Hüppi3, Benjamin C. Wilde3, Roland A. Werner3, Thomas Kuhn4, Moritz F. Lehmann4, Frank Hagedorn2, Martin Hartmann3, Thomas Scholten5, and Johan Six3
Luisa I. Minich et al.
  • 1Department of Earth Sciences, Biogeoscience, ETH Zurich, Zurich, Switzerland
  • 2Swiss Federal Institute for Forest, Snow and Landscape Research WSL, Forest Soils and Biogeochemistry, Zurich, Switzerland
  • 3Department of Environmental Systems Science, Sustainable Agroecosystems, ETH Zurich, Zurich, Switzerland
  • 4Department of Environmental Sciences, Aquatic and Stable Isotope Biogeochemistry, University of Basel, Basel, Switzerland
  • 5Institute of Geography, Chair of Physical Geography, Eberhard-Karls-University Tübingen, Tübingen, Germany

N2O is a stratospheric ozone depleting substance and a potent greenhouse gas which significantly contributes to global warming. Although soils are the largest source of N2O emissions, knowledge gaps in the understanding of N2O production and reduction processes in soils still exist. Here, we investigated N2O production and consumption processes along soil depth profiles in a mesocosm experiment using natural-abundance N2O and NO3- isotopic signatures as well as abundances of soil microbial genes associated with N2O production (nirK, nirS) and reduction (nosZ). Soil columns either displayed undisturbed soil stratification (control treatments), or contained an artificial clay layer at 35 cm depth (clay treatment), which acted as a diffusion barrier and thus induced O2-limited conditions in deeper strata. We collected soil pore gas, soil solution and soil samples at five depths of the soil columns over the course of four weeks. In addition, we continuously monitored N2O fluxes at the soil surface and soil environmental parameters (oxygen, moisture, temperature) along the soil depth profiles. Microbial gene analysis in soil samples revealed similar abundances of nirK, nirS and nosZ in the two treatments across the entire soil depth profiles. The distribution of the functional genes was thus not indicative of enhanced N2O production and/or reduction in O2-limited conditions. However, lowest O2 concentrations below the clay layer were associated with highest 15N and 18O enrichments in both NO3- and N2O, indicating N2O production by denitrification and fractional N2O reduction. In addition, we found higher N2O concentrations and surface fluxes for the clay treatment. Our observations imply a dominance of N2O production over N2O reduction, even under conditions most favorable for complete denitrification.

How to cite: Minich, L. I., Barthel, M., F. Conz, R., Hüppi, R., Wilde, B. C., Werner, R. A., Kuhn, T., Lehmann, M. F., Hagedorn, F., Hartmann, M., Scholten, T., and Six, J.: Elucidating soil pore N2O production and consumption processes using isotope and microbial gene analysis: A depth profile approach, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5707, https://doi.org/10.5194/egusphere-egu22-5707, 2022.