Preprints
https://doi.org/10.5194/bg-2021-228
https://doi.org/10.5194/bg-2021-228

  26 Aug 2021

26 Aug 2021

Review status: this preprint is currently under review for the journal BG.

Sources of nitrous oxide and fate of mineral nitrogen in sub-Arctic permafrost peat soils

Jenie A. Gil1,2, Maija E. Marushchak3, Tobias Rütting4, Elizabeth M. Baggs5, Tibisay Pérez6, Alexander Novakovskiy7, Tatiana Trubnikova1, Dmitry Kaverin7, Pertti J. Martikainen1, and Christina Biasi1 Jenie A. Gil et al.
  • 1Department of Environmental and Biological Sciences, University of Eastern Finland, Kuopio, P.O. Box 1627, FI-70211, Finland
  • 2Department of Integrative Biology, Great Lakes Bioenergy Research Center, Michigan State University, 288 Natural Science Bldg., East Lansing, MI 48824-1302, USA
  • 3Department of Biological and Environmental Science, University of Jyväskylä, P.O. Box 35, FI-40014 University of Jyväskylä, Finland
  • 4Department of Earth Sciences, University of Gothenburg, Box 460, 405 30 Gothenburg, Sweden
  • 5Global Academy of Agriculture and Food Security, The Royal (Dick) School of Veterinary Studies, University of Edinburgh, Easter Bush Campus, Midlothian EH25 9RG, UK
  • 6Centro de Ciencias Atmosféricas y Biogeoquímica. IVIC. Aptdo. 20634. Caracas 1020A. Venezuela
  • 7Institute of Biology, Komi SC UB RAS, 167982 Syktyvkar, Russia

Abstract. Nitrous oxide (N2O) emissions from permafrost-affected terrestrial ecosystems have received little attention, largely because they have been thought to be negligible. Recent studies, however, have shown that there are habitats in subarctic tundra emitting N2O at high rates, such as bare peat surfaces on permafrost peatlands. The processes behind N2O production in these high-emitting habitats are, however, poorly understood. In this study, we established an in situ 15N-labelling experiment with the main objectives to partition the microbial sources of N2O emitted from bare peat surfaces (BP) on permafrost peatlands and to study the fate of ammonium and nitrate in these soils and in adjacent vegetated peat surfaces (VP) showing low N2O emissions. Our results confirm the hypothesis that denitrification is mostly responsible for the high N2O emissions from BP surfaces. During the study period denitrification contributed with ~79 % of the total N2O emission in BP, while the contribution of ammonia oxidation was less, about 19 %. However, nitrification is a key process for the overall N2O production in these soils with negligible external nitrogen (N) load because it is responsible for nitrite/nitrate supply for denitrification, as also supported by relatively high gross nitrification rates in BP. Generally, both gross N mineralization and gross nitrification rates were much higher in BP with high N2O emissions than in VP, where the high C / N ratio together with low water content was likely limiting N mineralization and nitrification and, consequently, N2O production. Also, competition for mineral N between plants and microbes was additionally limiting N availability for N2O production in VP. Our results show that multiple factors control N2O production in permafrost peatlands, the absence of plants being a key factor together with inter-mediate to high water content and low C / N ratio, all factors which also impact on gross N turnover rates. The intermediate to high soil water content which creates anaerobic microsites in BP is a key N2O emission driver for the prevalence of denitrification to occur. This knowledge is important for evaluating future permafrost –N feedback loops from the Arctic.

Jenie A. Gil et al.

Status: open (until 20 Oct 2021)

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Jenie A. Gil et al.

Jenie A. Gil et al.

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Short summary
N2O emissions from permafrost soils represent up to 11.6 % of total N2O emissions from natural soils and their contribution to the global N2O budget will likely increase due to climate change. A better understanding of N2O production from permafrost soils is needed to evaluate the role of Arctic ecosystems in the global N2O budget. By studying microbial N2O production processes in N2O hotspots in permafrost peatlands we identified denitrification as the dominant source of N2O in these surfaces.
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