Sources of nitrous oxide and the fate of mineral nitrogen in subarctic permafrost peat soils

• Published in: Biogeosciences
• Main Authors: Gil, Jenie, Marushchak, Maija E., Rütting, Tobias, Baggs, Elizabeth M., Pérez, Tibisay, Novakovskiy, Alexander, Trubnikova, Tatiana, Kaverin, Dmitry, Martikainen, Pertti J., Biasi, Christina
• Format: Text
• Language: English
• Published: 2022
• Subjects: permafrost; Subarctic; Tundra
• Online Access: https://doi.org/10.5194/bg-19-2683-2022; https://bg.copernicus.org/articles/19/2683/2022/

Nitrous oxide (N 2 O) 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 the subarctic tundra emitting N 2 O at high rates, such as bare peat (BP) surfaces on permafrost peatlands. Nevertheless, the processes behind N 2 O production in these high-emission habitats are poorly understood. In this study, we established an in situ 15 N-labeling experiment with two main objectives: (1) to partition the microbial sources of N 2 O emitted from BP surfaces on permafrost peatlands and (2) to study the fate of ammonium and nitrate in these soils and in adjacent vegetated peat (VP) surfaces showing low N 2 O emissions. Our results confirm the hypothesis that denitrification is mostly responsible for the high N 2 O emissions from BP. During the study period, denitrification contributed ∼ 79 % of the total N 2 O emissions from BP, whereas the contribution from ammonia oxidation was less (about 19 %). Both gross N mineralization and gross nitrification rates were higher in BP than in VP, with high <math xmlns="http://www.w3.org/1998/Math/MathML" id="M11" display="inline" overflow="scroll" dspmath="mathml"><mrow class="chem"><mi mathvariant="normal">C</mi><mo>/</mo><mi mathvariant="normal">N</mi></mrow></math> <svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="24pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="52d63b335eddc5e385ee84fd84bbc814"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="bg-19-2683-2022-ie00001.svg" width="24pt" height="14pt" src="bg-19-2683-2022-ie00001.png"/></svg:svg> ratios and a low water content likely limiting N transformation processes and, consequently, N 2 O production in the latter soil type. Our results show that multiple factors contribute to high N 2 O production in BP surfaces on permafrost peatlands, with the most ...