High rates of N and C mineralization in upper permafrost of a thawing palsa mire and their implications for GHG dynamics

Lamprecht, Richard E.; Diáková, Kateřina; Voigt, Carolina; Siljanen, Henri M. P.; Šantrůčková, Hana; Martikainen, Pertti J.; Biasi, Christina; Marushchak, Maija E.

doi:10.5194/egusphere-2026-5330

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https://doi.org/10.5194/egusphere-2026-5330

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11 Sep 2026

| 11 Sep 2026

Status: this preprint is open for discussion and under review for Biogeosciences (BG).

High rates of N and C mineralization in upper permafrost of a thawing palsa mire and their implications for GHG dynamics

Richard E. Lamprecht, Kateřina Diáková, Carolina Voigt, Henri M. P. Siljanen, Hana Šantrůčková, Pertti J. Martikainen, Christina Biasi, and Maija E. Marushchak

Abstract. Rapid warming accelerates permafrost thaw in Arctic peatlands, exposing their large stocks of soil organic matter (SOM) to microbial decomposition. Despite the importance of permafrost peatlands for ecosystem-climate feedback, their coupled C and N mineralization potential and associated greenhouse gas (GHG) dynamics still remain poorly understood. Particularly interesting in this context is the upper permafrost, which is expected to thaw in near future and has been linked to substantial CO₂ and N₂O production in previous studies.

Here, we investigated depth patterns of SOM mineralization and GHG production in a subarctic palsa mire in a factorial incubation experiment, where peat from active layer and upper permafrost was exposed to three temperatures (4, 10, and 16 °C) and two oxygen conditions (aerobic, anaerobic).

The highest rate of CO₂ production with the lowest temperature sensitivity were found in the surface peat and upper permafrost. Surface peat showed CH₄ consumption under aerobic condition, while CH₄ production was negligible across all peat depths and oxygen conditions. The highest rate and lowest temperature sensitivity of net N mineralization were found in upper permafrost and active layer-permafrost interface, but this did not translate into high N₂O production; instead, the maximum N₂O production occurred under anaerobic condition in the lower active layer.

Overall, our study revealed distinct depth patterns of C and N dynamics in palsa profiles, with high mineralization potential in the upper permafrost, supported by labile SOM. Relatively high mineralization rates at low temperatures resulted in low temperature sensitivity in the upper permafrost, and indicate high potential for C and N losses under realistic temperature range expected with gradual active layer deepening in the deep peat layers.

Received: 07 Sep 2026 – Discussion started: 11 Sep 2026

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Richard E. Lamprecht, Kateřina Diáková, Carolina Voigt, Henri M. P. Siljanen, Hana Šantrůčková, Pertti J. Martikainen, Christina Biasi, and Maija E. Marushchak

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CC1:
'Comment on egusphere-2026-5330', Yanyu Song, 05 Oct 2026 reply
The authors investigated the vertical changing of soil carbon, nitrogen mineralization, CO2, CH4, N2O emission and their mechanisms under permafrost thawing, and found that the high substrate availability in the upper permafrost resulted in the highest CO2 production rates, surface peat showed CH4 consumption under aerobic condition, N2O production was primarily controlled by oxygen availability and coupled oxic-anoxic transformations. The results provide valuable support for assessing soil carbon and nitrogen stability under permafrost degradation. The method, data, results and discussion are appropriate. However, the research novelty and scientific rigor of the writing needs improvement.
Detailed comments:
Line 24, “C and N mineralization”, the full names of C and N should be given when they first appeared.

Lin3 77-94, “Click or tap here to enter text”, add the reference?

In the introduction section, more recently published references should be cited and the research gaps should be highlighted.

Line 250, 901, 905, “P ≤ 0.05”, P should be used in italic.

Line 289, “Cmic”, mic should be used in subscript.

Line 587, 722, CH4, line 599, 636, 650, 691, 729, 743, N2O, line 721, CO2......, 4 and 2 should be used in subscript.

Line 592-594, the words in the reference title should be revised as lowercase letters.

Line 898, 899, “CO2-C production rate (mg kg-1 DW (dry weight) day-1) and aerobic (c) and anaerobic (d) CH4-C production rate (µg kg-1 DW (dry weight) day-1)”, 2 and 4 should be used in subscript, -1 should be used in superscript, the same in other figure captions and tables.

Line 951, “p”should be revised as P and used in italic.

In the Supplementary materials, line 127, double “in”, line 136, “soil”should be deleted”, line 148, double “knocked”.

Line 280, the unit of Cmic is different from the figure S7.

Line 470, 476, “CO2 production rate unit is presented in mg C kg-1 dry weight day-1, however, in the table it is µg C kg-1 dry weight day-1).

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Citation: https://doi.org/10.5194/egusphere-2026-5330-CC1
RC1: 'Comment on egusphere-2026-5330', Anonymous Referee #1, 13 Oct 2026 reply

Lamprecht et al. investigated C and N mineralisation as well as GHG production at different depths from a sub arctic peat plateau. They included both oxic and anoxic incubation at three different temperatures, which is the novelty of this study. They found depth patterns for both C and N mineralisation with highest mineralisation potential in the surface layer and the top of the permafrost. They also found that the temperature sensitivity was lower in the permafrost samples compared to the active layer showing that potential mineralisation can happen even at low temperatures. The study is an interesting contribution to the field and improves our understanding of potential decomposition of organic matter across different depths and at different temperatures. With this being said, I do have some major and minor comments that should be considered.
Major comments:
In my opinion, the main challenge with the study is that they use soils that have already been thawed and used for a mesocosm study. While the discussion includes some comparisons with the mesocosm study, a more critical view should also be addressed; how can the fact that the soils have already been thawed and through a different experiment affect the results that you present? This is especially relevant for the permafrost samples that are described as newly thawed.
Another thing, that is missing from the study, is the temporal variability that inevitably will occur in a 161 days incubation experiment. In the method section for calculating the Q₁₀ it is described that CO2 production is fitted to an exponential function (lines 226-234), however, the CO2 production in the rest of the paper is presented as on number for the entire period. It would improve the paper if this was considered and discussed for especially CO2 and CH4. The temporal resolution of N2O is already touched upon when presenting the maximum production.
I think the paper is also missing some considerations about how representative these findings are. For instance, in line 136 it is described that the site was selected to be a site with high N2O production. How does this affect the results and especially the findings regarding N2O?
Minor comments.
Line 44: The number 415 ±147 Pg C refers to all northern peatland and not only the permafrost affected ones. This should be clearer.
Line 52: “most of the N stocks” is a bit vague and could be clearer, e.g., about two-thirds.
Line 67: Kjær et al. (2024) also measured N2O but found minute production.
Lines 76-94: Needs to be updated with references instead of “Click or tap here to enter text”.
Line 119: Could you specify why you expect higher mineralization rates in the PF compared to AL? Does it refer to the bioavailability?
Line 138: It would be nice with references to which part of the SI and which method section. Especially since most of the method is copied directly in the SI and it is a bit tedious to read it twice.
Line 144: No dash in 33-weeks
Line 147: What is the effect of thaw-refreeze on especially the permafrost?
Line 170: Again, please refer to where in the SI.
Line 172-178: Were the flasks opened between each sampling interval? If yes, then the first sentence should be rewritten. Either way this section could be rewritten to make it a bit clearer for the reader.
Line 188-192: Why not include the negative values? As you write it cannot be ruled out that chemoautotrophic CO2 consumption or anaerobic CH4 oxidation could have happed.
Line 199: Refer to where in SI
Line 214: Change from (Weishaar et al., 2003) to Weishaar et al. (2003).
Line 219: Please describe how you calculated the net nitrification.
Line 237: Specify the T1 and T2 in the text.
Line 251: You should specify in which way the testing differs for the incubation temperature as you describe the testing to be similar and not the same.
Line 270: Are the values in the table from before the mesocosm experiment? Or from before this experiment?
Line 288: Remember to add S in front of the figure numbers for all the figures. I can guess that Fig. S7, 8 and 10 refers to the SI since you don’t have figure 8 and 10. You should go through the whole text and double check this
Line 289: Cmic should be with subscript
Line 292: The asterisks in figure 2 need to be better explained. It is not clear what they indicate.
Line 369- 377: Very repetitive of the results and should be rewritten.
Line 387-393: The flow is a bit abrupt and could be improved. Maybe write it as a separate section from the previous.
Line 402-405: As the DOC in the surface peat is not as high as in the permafrost layer, I think you should change the phrasing. And maybe also mention why the mineralisation is high in the surface peat despite not having very high DOC.
Line 477-482: Long lag-phases for CH4 production has also been observed in anaerobic incubations. Was there any indication of increased CH4 over time?
Line 485-490: How is the temporal distribution of the CH4 in the aerobic incubations? Could it be release of previously stored CH4 rather than production?

Language:
It will improve readability if you correct the places where (xx) (xx). Write instead (xx; xx). Especially since you do it some places and not in others
Check subscript/superscript in the figure captions
A lot of DOI numbers does not work and should be checked

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Citation: https://doi.org/10.5194/egusphere-2026-5330-RC1

Richard E. Lamprecht, Kateřina Diáková, Carolina Voigt, Henri M. P. Siljanen, Hana Šantrůčková, Pertti J. Martikainen, Christina Biasi, and Maija E. Marushchak

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https://doi.org/10.5194/egusphere-2026-5330-supplement

Richard E. Lamprecht, Kateřina Diáková, Carolina Voigt, Henri M. P. Siljanen, Hana Šantrůčková, Pertti J. Martikainen, Christina Biasi, and Maija E. Marushchak

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Short summary

We studied carbon and nitrogen mineralization and greenhouse gas production in a subarctic palsa mire, sensitive to climate warming and permafrost thaw. We conducted a factorial incubation experiment, where we were looked at the effect of temperature, oxygen and peat characteristics on these processes. We found that the upper permafrost contained a highly labile carbon and nitrogen pool, supporting high CO₂ production and N mineralization, both associated with low temperature sensitivities.


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