EGU General Assembly 2022
© Author(s) 2022. This work is distributed under
the Creative Commons Attribution 4.0 License.

Spatial changes in nitrogen inputs drive short- and long-term variability in global N2O emissions

Eliza Harris1,2, Longfei Yu3,4, Yingping Wang5, Joachim Mohn3, Stephan Henne3, Edith Bai6, Matti Barthel7, Marijn Bauters8, Pascal Boeckx8, Chris Dorich9, Mark Farrell10, Paul Krummel5, Zoe Loh5, Markus Reichstein11, Johan Six7, Martin Steinbacher3, Naomi Wells12,13, Michael Bahn1, and Peter Rayner14,15
Eliza Harris et al.
  • 1Functional Ecology Research Group, University of Innsbruck, Austria
  • 2Swiss Data Science Centre, ETH Zurich, 8092 Zurich, Switzerland
  • 3Laboratory for Air Pollution & Environmental Technology, Empa, Switzerland
  • 4Institute of Environment and Ecology, Tsinghua Shenzhen International Graduate School (SIGS), Tsinghua University, China
  • 5Climate Science Centre, CSIRO Ocean and Atmosphere, Victoria, Australia
  • 6Institute of Applied Ecology, Chinese Academy of Sciences, China
  • 7Department of Environmental Systems Science, ETH Zurich, Switzerland
  • 8Isotope Bioscience Laboratory, ISOFYS, Ghent University, Belgium
  • 9Natural Resource Ecology Laboratory, Colorado State University, Fort Collins, USA
  • 10CSIRO Agriculture and Food, South Australia, Australia
  • 11Department of Biogeochemical Integration, Max Planck Institute for Biogeochemistry, Jena, Germany
  • 12Centre for Coastal Biogeochemistry, Southern Cross University, Australia
  • 13Department of Soil & Physical Sciences, Agriculture & Life Sciences, Lincoln University, New Zealand
  • 14School of Geography, Earth and Atmospheric Sciences, University of Melbourne, Victoria, Australia
  • 15Melbourne Climate Futures Climate and Energy College, University of Melbourne, Victoria, Australia

Anthropogenic activities, particularly fertilisation, have resulted in significant increases in nitrogen in soils globally, leading to negative environmental impacts including eutrophication, acidification, poor air quality, and emissions of the important greenhouse gas N2O. Potential changes in terrestrial N loss pathways driven by global change and spatial redistribution of N inputs are highly uncertain. We present a novel coupled soil-atmosphere isotope model (IsoTONE; ISOtopic Tracing Of Nitrogen in the Environment) to quantify terrestrial N losses and N2O emissions and emission factors for the period 1850-2020. The soil module is initialised using a global isoscape of natural soil δ15N values generated from measurement data using an artificial neural network. The model is optimized within a Bayesian framework using a high precision tropospheric time series of N2O isotopic composition as well as emission factor measurements from many sites across the globe.

N inputs from atmospheric deposition caused the majority (51%; 3.6±0.3 Tg N2O-N a-1) of total anthropogenic N2O emissions from soils (7.1±0.9 Tg N2O-N a-1) in 2020. Growth in total and anthropogenic soil N2O emissions over the past century was driven by both fertilization and deposition, however N inputs from biological fixation were responsible for subdecadal variability in emissions. N2O emission factors show large spatial variability due to climate and soil parameters. The mean global EF for N2O weighted by N inputs was 4.3±0.3% in 2020, much higher than the land surface area-weighted mean of 1.1±0.1%, as a large proportion of N inputs were in regions with relatively high emission factors. Climate warming as well as redistribution of fertilisation inputs have led to an increase in global EF for N2O over the past century; these additional emissions account for 18% of the total anthropogenic soil flux in 2020. Predicted increases in fertilisation in emerging economies will accelerate N2O-driven climate warming in the coming decades, unless targeted mitigation measures focussing on fertiliser management in developing regions are introduced.

How to cite: Harris, E., Yu, L., Wang, Y., Mohn, J., Henne, S., Bai, E., Barthel, M., Bauters, M., Boeckx, P., Dorich, C., Farrell, M., Krummel, P., Loh, Z., Reichstein, M., Six, J., Steinbacher, M., Wells, N., Bahn, M., and Rayner, P.: Spatial changes in nitrogen inputs drive short- and long-term variability in global N2O emissions, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1150,, 2022.

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