Impact of micro habitat properties and seasonal weather conditions on N₂O fluxes in the Arctic

Lead: Dr. Nathalie Ylenia Triches

Impact of micro habitat properties and seasonal weather conditions on N₂O fluxes in the Arctic

Global warming and its impacts have been documented for more than three decades, especially in vulnerable regions that are crucial for the global climate. In (sub)- Arctic regions, where air temperatures have been increasing two to four times faster than the global average (1), the carbon cycle and greenhouse gas fluxes from carbon dioxide (CO₂) and methane (CH₄) have been documented for many years (2). Two decades ago, researchers started suggesting that substantial amounts of nitrous oxide (N₂O) may be emitted from organic- and ice-rich permafrost soils (3,4). This is important because N₂O affects both the local biogeochemistry and global climate, as it stays in the atmosphere for more than 100 years and has a 298 times stronger global warming potential than the same mass of CO₂ over a time frame of 100 years- although its concentration in the atmosphere is more than a thousand times lower than that of CO₂. In the Arctic, most studies have concentrated on high-emitting sites, neglecting the vast nutrient-poor areas which could show low N₂O fluxes or even an uptake of N₂O from the atmosphere into the soil (5). As a result, the magnitude and drivers of N₂O fluxes from nutrient-poor sites are still poorly understood.

During my PhD, I solved several research gaps concerning N₂O fluxes from (sub-) Arctic soils:

• Provide an extensive dataset investigating N₂O fluxes from permafrost soils (6)
• Produce guidelines on how to best measure low N₂O fluxes or N₂O uptake in nutrient-poor soils (7)
• Examine how N₂O fluxes are influenced by different micro habitats properties, seasonal weather conditions and microbial activity (8)

My overall aim was to bring forward our knowledge on N₂O fluxes in the Arctic by studying one subarctic palsa mire, the Stordalen mire, in detail. Palsas are raised peat mounds that form when frozen ice lenses push peat layers upward (see figure below). They are a common - but disappearing - landscape feature in Fennoscandia. The Stordalen mire is one of the best studied, but complex palsa mire underlain by sporadic permafrost located in subarctic Sweden (68° 20.0’ N, 19° 30.0’ E), 10 km east of Abisko (Ábeskovvu in Northern Sámi language). Permafrost has been thawing rapidly at this location over the last decades, and only remains in the dry uplifted areas on the peatland- the palsas.

Over three snow-free seasons (September 2022, May, June, July, and September 2023, and June, July, and August 2024), I, together with students from several international universities, measured N₂O, CH₄, and CO₂ fluxes on a palsa-bog-fen thawing gradient (dry to wet habitats) using dark and transparent chambers with portable greenhouse gas analysers (see photos on the bottom of the page). With the data we collected, we provide the most comprehensive dataset on Arctic N₂O fluxes to date, gathered using the manual chamber method (6). 

With our results, we

1. provide practical guidelines for successful Arctic N₂O studies, and emphasise the need to conduct both light and dark measurements, and, if possible, include simultaneous measurements of carbon fluxes (7). These recommendations are not only relevant to Arctic studies but also applicable to investigations of low N₂O fluxes in other ecosystems, such as peatlands and forests in temperate and boreal regions. The use of novel gas analysers, like the Aeris MIRA Ultra N₂O/CO₂ , while adjusting chamber closure times to the size of the chamber and ecosystem, are crucial for accurate measurements. Our expertise with this analyser has already gathered international attention, with researchers from around the world seeking our advice on its use.
2. demonstrate that a nutrient-poor peatland can acts as a continuous, non-negligible yet small sink for N₂O during the snow-free season—first in-situ evidence of sustained uptake in Arctic peatlands. However, we also identify a localised N₂O hot spot, showing that a single site could transform the ecosystem from a net sink to a net source (8).
3. identify photosynthetically active radiation (PAR) and net ecosystem exchange (CO₂ fluxes), impacted by vegetation, soil temperature and soil moisture, as the dominant drivers of low N₂O fluxes, with consistent differences between light and dark conditions (Wilcoxon rank-sum test: 0.37, p < 0.001; 8).

 

 

At Stordalen, I still closely collaborate with scientists from Finland and the US. Within the automated chamber (AC) system from the long-term project “EMergent Ecosystem Responses to ChanGE” EMERGE of the University of New Hampshire (PI: Ruth Varner), the University of Eastern Finland (UEF) installed a Picarro N₂O analyser in May 2022 to continuously measure N₂O and CH₄ fluxes on a thawing gradient. This analyser has been removed in August 2025, and the AC data is analysed within the Nitrogen-Permafrost project N-PERM at UEF (PI: Christina Biasi, Jenie Gil Lugo, and Maija Marushchak).

With scientists from UEF, we are having a close look at the micro organisms living in the soil to explain what drives the N₂O and CO₂ fluxes we measure in the field. Last but not least, scientists from the University of Helsinki (PI: Ivan Mammarella) installed an Aerodyne N₂O laser at the ICOS eddy covariance flux tower at Stordalen in August 2022. All our measurements will provide the first extensive database of N₂O flux measurements in the (sub-) Arctic.

References

1. Rantanen, M., Karpechko, A.Y., Lipponen, A. et al. The Arctic has warmed nearly four times faster than the globe since 1979. Commun Earth Environ 3, 168 (2022). https://doi.org/10.1038/s43247-022-00498-3 

2. Schuur, E.A.G., Abbott, B.W., Commane R. et al. Permafrost and Climate Change: Carbon Cycle Feedbacks From the Warming Arctic. Annu. Rev. Environ. Resour. 47, 343-371 (2022). https://doi.org/10.1146/annurev-environ-012220-011847

3. Elberling, B., Christiansen, H. & Hansen, B. High nitrous oxide production from thawing permafrost. Nature Geosci 3, 332–335 (2010). https://doi.org/10.1038/ngeo803

4. Marushchak, M.E., Kerttula, J., Diáková, K. et al. Thawing Yedoma permafrost is a neglected nitrous oxide source. Nat Commun 12, 7107 (2021). https://doi.org/10.1038/s41467-021-27386-2

5. Voigt, C., Marushchak, M.E., Abbott, B.W. et al. Nitrous oxide emissions from permafrost-affected soils. Nat Rev Earth Environ 1, 420–434 (2020). https://doi.org/10.1038/s43017-020-0063-9

 

6. Triches, N.Y., Rovamo, M., Hashmi, W. et al. Manual chamber CH₄, CO₂, N₂O fluxes + auxiliary data from Stordalen Mire, N Sweden, 2022-2024 (2026). Edmond V2, https://doi.org/10.17617/3.WOIQRC

7. Triches, N.Y., Engel, J., Bolek, A. et al. Practical guidelines for reproducible N₂O flux chamber measurements in nutrient-poor ecosystems (2025). Atmos. Meas. Tech. 18, 3407–3424, https://doi.org/10.5194/amt-18-3407-2025 

8. Triches, N.Y., Bolek, A., Rovamo, M. et al. Light and dark conditions control the nitrous oxide uptake and emission dynamics in a subarctic, nutrient-poor permafrost peatland. Commun Earth Environ 7, 471 (2026). https://doi.org/10.1038/s43247-026-03698-3

9. Triches, N. Y. Revealing drivers of nitrous oxide (N₂O) fluxes in a thawing sub-Arctic permafrost peatland (2026). Dissertationes Forestales, 1105,  https://doi.org/10.14214/df.383