the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 11 Sep 2026
High rates of N and C mineralization in upper permafrost of a thawing palsa mire and their implications for GHG dynamics
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.
- Preprint
(1815 KB) - Metadata XML
-
Supplement
(2251 KB) - BibTeX
- EndNote
Status: final response (author comments only)
-
CC1: 'Comment on egusphere-2026-5330', Yanyu Song, 05 Oct 2026
-
AC1: 'Reply on CC1', Richard E. Lamprecht, 12 Nov 2026
CC1: 'Comment on egusphere-2026-5330', Yanyu Song, 05 Oct 2026
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.
We thank Yanyu Song for the comment and suggestions to improve our text. We are grateful that our work is seen valuable for this research field and that our scientific approach is seen appropriate.
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).
We thank Yanyu Song for the detailed comments and suggestions and will revise the text accordingly.
Citation: https://doi.org/10.5194/egusphere-2026-5330-AC1
-
AC1: 'Reply on CC1', Richard E. Lamprecht, 12 Nov 2026
-
RC1: 'Comment on egusphere-2026-5330', Anonymous Referee #1, 13 Oct 2026
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
Citation: https://doi.org/10.5194/egusphere-2026-5330-RC1 -
AC2: 'Reply on RC1', Richard E. Lamprecht, 12 Nov 2026
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2026/egusphere-2026-5330/egusphere-2026-5330-AC2-supplement.pdf
-
AC2: 'Reply on RC1', Richard E. Lamprecht, 12 Nov 2026
-
RC2: 'Comment on egusphere-2026-5330', Anonymous Referee #2, 24 Oct 2026
This study examines how carbon and nitrogen mineralization and greenhouse gas (GHG) production vary with depth in a subarctic palsa mire. The authors conducted an incubation experiment using peat from the active layer and upper permafrost, exposed to three temperatures (4, 10, and 16C) under aerobic and anaerobic conditions. The study addresses an important question: how might the thawing of previously frozen peat affect C and N cycling and greenhouse gas production as the active layer deepens?
The results show clear differences in C and N cycling across the peat profile. CO2 production was highest in surface peat and upper permafrost, while net N mineralization was highest in the upper permafrost and at the active-layer-permafrost interface. However, these high mineralization rates did not correspond to high CH4 or N2O production, highlighting that greater C and N turnover does not necessarily result in greater GHG production.
Overall, the study addresses an important topic, and the incubation experiment provides useful insights into the potential for C and N turnover at different peat depths. However, some aspects of the manuscript need further clarification. In particular, I have concerns about experimental methods and the calculation of temperature sensitivity, the interpretation of the PCA, and how the results are linked to potential ecosystem-level responses to permafrost thaw. The Results section could also be improved to make the main findings easier to follow, rather than presenting the results largely as a sequence of individual variables. Finally, there are some formatting issues and paragraphs that need clarification. I believe that addressing these points would strenghten the manuscript and help ensure that the conclusions are well supported by the results.
More specific comments
Introduction and Methods
Lines 77-94: There appear to be formatting issues in this section, potentially involving missing citations. Multiple sentences end with “Click or tap here to enter text.” Please check and correct these errors to ensure that the text and references are complete.
Line 112: I am not sure that the concept of “vulnerability” is directly assessed by the experimental setup. The experiment appears to quantify the potential for C and N mineralization and GHG production under different temperature and oxygen conditions, rather than vulnerability itself. Please consider revising this statement to more accurately reflect the study objectives, for example, by stating that the aim was to quantify C and N mineralization rates and associated GHG production across peat depths and experimental conditions.
Line 118: Although it is clear that the peat material was obtained from a previous experiment, please briefly describe the experimental approach used in the present study before introducing the hypotheses. This would help readers understand the study design without having to consult the earlier publication.
Line 134: Please add a space between the preceding word and the parenthesis.
Line 139: “Four” should not be capitalized in this context.
Lines 135-148: Please specify when the peat cores were collected, including at least the season. Readers should be able to understand the sampling context without having to consult the previous publications.
Line 145: The phrase “regular water additions” is somewhat ambiguous, as it could be interpreted as referring to a particular type of water. Please rephrase this but also clarify the source and composition of the water used to maintain moisture during the experiment. Since the study site is described as ombrotrophic, the chemical composition of the added water could influence the mineral and nutrient baseline and potentially affect microbial processes. Were any chemical or nutrient analyses performed on the water used during the incubation? If so, please report the relevant results. If not, please clarify the water source and acknowledge this as a potential consideration where appropriate.
Line 152: Please clarify what is meant by “high layers.” If this refers to peat sections of the same length, “equal-length peat layers” may be more appropriate.
Line 220: The authors estimate the temperature sensitivity of CO2 production by fitting an exponential model across the incubation temperatures, whereas Q10 for net N mineralization is calculated from rates measured at only two temperatures. Please clarify the rationale for using these different approaches, particularly if measurements were available at additional incubation temperatures, and explain how the temperature interval used for calculating Q10Nmin was selected.
Furthermore, because net N mineralization represents the balance between gross mineralization and microbial immobilization, rates may be close to zero or negative, potentially making the conventional Q10 calculation inappropriate or difficult to interpret. Please clarify whether such cases occurred and, if so, how they were handled. These methodological details are important for assessing the robustness and interpretation of the reported temperature sensitivities.
Line 254: Please change “I)” to “1)” for consistency with the subsequent numbering.
Results
General comment: The Results section reads largely as a sequence of variables and statistical tests. I suggest revising it to improve the narrative and highlight the main patterns across the peat profile, rather than reporting each parameter in isolation. Grouping related characteristics and more clearly distinguishing statistically significant depth-dependent patterns from nonsignificant trends would make the results easier to follow and help readers better appreciate the key findings.
Line 292 and elsewhere: Please specify whether the reported error values represent standard deviations or standard errors, and use this terminology consistently throughout the manuscript, including in the figures and tables where applicable.
Lines 344-366: The interpretation of the PCA would benefit from clarification regarding the inclusion of Q10Nmin alongside net N mineralization rates. Because Q10Nmin is derived from N mineralization rates measured at two temperatures, its inclusion alongside Nmin may introduce mathematical dependence among the variables and influence the ordination.
Furthermore, Q10Nmin was calculated using rates at 10 and 16C, whereas the authors report the clearest separation among peat layers in the PCA at 4C. Thus, this variable does not directly characterize the temperature response underlying the patterns observed at 4C. Please clarify the rationale for including Q10Nmin in the PCA and consider whether the main patterns and conclusions are robust to its exclusion. If the aim is to identify the factors associated with variation in N mineralization across temperatures and peat layers, an analysis that explicitly accounts for temperature and peat layer may provide a more direct assessment.
Discussion
Lines 491 until the end of that section: The discussion of potential greenhouse gas responses following palsa collapse would benefit from a more balanced consideration of the processes governing the ecosystem carbon balance. While the authors acknowledge that the establishment of productive vegetation may increase labile carbon inputs and stimulate CO2 and CH4 production, they do not consider that vegetation also fixes atmospheric CO2 through photosynthesis. Consequently, changes in microbial CO2 and CH4 production alone are insufficient to infer the net greenhouse gas balance following collapse. This balance will depend on the interplay between photosynthetic uptake, ecosystem respiration, methane production and oxidation, and carbon accumulation or export. I suggest that the authors acknowledge these competing processes and avoid implying that increased greenhouse gas production necessarily translates into greater net ecosystem emissions.
Furthermore, the statement that anaerobic incubations likely underestimated CH4 production because of microbial limitations, which would supposedly be rapidly alleviated following palsa collapse, appears speculative unless supported by evidence from the incubation results or relevant literature. Please clarify the basis for this interpretation and acknowledge that the direction and magnitude of potential biases in incubation-derived rates depend on the experimental conditions.
Finally, although discrete soil incubations cannot fully capture ecosystem-level greenhouse gas fluxes or climate feedbacks, they remain valuable for quantifying process potentials and identifying depth-dependent controls. I recommend revising this discussion to distinguish more clearly between the processes measured experimentally and the broader ecosystem-level implications inferred from them.
505: N mineralization rates *were*
517: gets -> becomes
Figures
Figure 5: Some points in the PCA plot appear larger than others. Please clarify whether point size represents a variable or has any other meaning. If it encodes information, this should be explained in the figure legend; if not, please ensure that the points are displayed consistently to avoid implying an unintended visual distinction.
Citation: https://doi.org/10.5194/egusphere-2026-5330-RC2 -
AC3: 'Reply on RC2', Richard E. Lamprecht, 12 Nov 2026
The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2026/egusphere-2026-5330/egusphere-2026-5330-AC3-supplement.pdf
-
AC3: 'Reply on RC2', Richard E. Lamprecht, 12 Nov 2026
Viewed
| HTML | XML | Total | Supplement | BibTeX | EndNote | |
|---|---|---|---|---|---|---|
| 438 | 196 | 85 | 719 | 122 | 81 | 83 |
- HTML: 438
- PDF: 196
- XML: 85
- Total: 719
- Supplement: 122
- BibTeX: 81
- EndNote: 83
Viewed (geographical distribution)
| Country | # | Views | % |
|---|
| Total: | 0 |
| HTML: | 0 |
| PDF: | 0 |
| XML: | 0 |
- 1
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: