the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 12 Mar 2025
Long-term ecosystem dynamics of an ice-poor permafrost peatland in eastern Eurasia: paleoecological insights into climate sensitivity
Abstract. Northern peatlands are carbon-rich ecosystems highly sensitive to climate change, with nearly half of their carbon stocks associated with permafrost. Peat-based paleoecological records provide insights into the complex responses of permafrost peatlands to long-term climate variability, but most studies were conducted in ice-rich permafrost peatlands in Europe and North America. Here, we use multiple active-layer cores to reconstruct the ecosystem history of an ice-poor permafrost peatland in eastern Eurasia, near the southernmost limit of circumpolar permafrost but outside the circumpolar thermokarst landscape.
Our results show that the peatland, which developed on a floodplain since the late Holocene cooling, underwent a major phase of lateral expansion during the Little Ice Age. A fen-to-bog transition occurred in recent decades, with dry-adapted Sphagnum mosses replacing herbaceous vegetation across the site and having rapid surficial peat accumulation. Carbon isotope ratios of Sphagnum macrofossils, a proxy for surface wetness, indicate that Sphagnum mosses initially established under very dry conditions but that their habitats have since become gradually wetter.
Synthesizing these findings, we highlight that: (1) permafrost aggradation during climate cooling may promote new peatland formation over permeable mineral substrate by impeding drainage; (2) anthropogenic climate warming and active layer deepening can induce an ecosystem-scale regime shift, but ice-poor permafrost peatlands generally exhibit stability and homogeneity due to the absence of dynamic surface morphology (such as frost heave and thermokarst collapse); (3) recent wetting may result from surface adjustment–hydrology feedback and vegetation–hydrology feedback, demonstrating the internally driven resilience of ice-poor permafrost peatlands in maintaining their hydrology and carbon accumulation; and (4) ice-poor permafrost peatlands are likely to remain persistent carbon sinks under ongoing and future climate change.
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RC1: 'Comment on egusphere-2025-946', Sebastian Wetterich, 30 Apr 2025
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GENERAL REMARKS
The manuscript by Xia et al. entitled “Long-term ecosystem dynamics of an ice-poor permafrost peatland in eastern Eurasia: paleoecological insights into climate sensitivity” addresses late-Holocene to recent permafrost peatland development and ecosystem dynamics based on active-layer sampling and analyses of peat properties including density, contents of organic matter, carbon (C) and nitrogen (N), C/N ratios of the peats as well as plant macrofossil compositions. Further analytical work dealt with carbon (δ13C) and oxygen (δ18O) stable isotope compositions of Sphagnum cellulose samples to infer local changes in moisture conditions. The chronology of the peat cores is based on radiocarbon dating that was further employed to model peat accumulation and carbon sequestration. As the study was undertaken in an ice-poor peatland, which are generally poorly studied, the present work is certainly of interest for understanding hydrology-vegetation feedback mechanisms in permafrost ecosystems and clearly fits into the scope of Biogeosciences. The data are novel and especially the applied combination of analyses allows for deducing substantial conclusions on the functioning of ice-poor peatlands and their role as carbon sink under climate change. The conclusions are clearly based on and supported by the novel data of the present study. Needed references to previous studies are indicated and appropriate.
The overall presentation of the study is very good. The text is well structured, concisely written and easy to follow. The figures and tables are clear and informative. The methods are valid and mostly sufficiently described in the Material and methods section. Thus, the applied methods are sufficiently described to make the results traceable. Only the CN analyses and the radiocarbon dating require some more information on lab procedures, analytical errors etc., which might be included either providing relevant references or a more detailed description.
A very minor flaw relates to some potentially misleading understanding in terminology such as “circumpolar thermokarst landscapes” or “longterm”.
Please, find my minor remarks below referring to line (ln) numbers of the submitted ms.
MINOR REMARKS
Title
ln1-2: I find the term “longterm” misleading as it implies longer timescales than the late Holocene captured by the present study. Please, consider rewriting the title and elsewhere in the manuscript.
Abstract
ln13-15: As permafrost of the southern hemisphere is not relevant for the present study, consider using the more common term “circumarctic permafrost” here and elsewhere in the manuscript. I’m further unsure what do you mean by “circumpolar thermokarst landscape”; firstly because landscape captures in my understanding much smaller areas with comparable inventory, which is surely not the case on circumarctic scale stretching from the Arctic Ocean across lowlands and mountains, tundra and boral taiga, etc. Secondly, noting “thermokarst” probably indicates features of permafrost degradation—thermokarst is one of them—in areas of continuous distribution of ice-rich permafrost. As I understand, you refer to the Olefeldt et al. (2016), but in context of your abstract you might just write the permafrost in your study region is ice-poor.
Olefeldt et al. (2016). https://doi.org/10.1038/ncomms13043
ln16-17: It would be useful to restrict periods to one term throughout the manuscript. In ln376-380 you use “neoglacial period” and “late Holocene cooling” for the Little Ice Age (LIA). I further suggest defining the period by dates either from your study or from the regional literature as the timing and the expression of the LIA differed spatially. See e.g. Neukom et al. (2019).
Neukom et al. (2019). https://doi.org/10.1038/s41586-019-1401-2
ln18: „…leading to rapid surficial peat accumulation.”
Introduction
ln76: As you state in ln108 that your study site is within the zone of continuous permafrost distribution, but in ln122probably belonging to the zone of discontinuous permafrost distribution in general terms based on the IPA map, please be concise to avoid confusion. It might be useful to refer to the updated permafrost map by Obu et al. (2019).
Obu et al. (2019). https://doi.org/10.1016/j.earscirev.2019.04.023
ln114-115: “… allow us to draw a comprehensive picture …”
ln114-115: Delete “any”.
ln114-115: “spatial heterogeneity” of surface features and/or ground properties”
Materials and methods
ln119-124: Add information on ground temperatures, active-layer thickness (ALT) and if available further permafrost characteristics of the study region in this paragraph.
ln125: “The Tuqiang peatland developed on a …”
ln136-137: Polygon ponds? As the ice content of the frozen deposits is generally low?
ln140: Do you know when the annual maximum ALT occurs in the study region?
ln143 and ln148-151: As you sampled the unfrozen active layer, why did you freeze your samples altering the core lengths?
ln155-156: Please, see my general remark and add some more information on lab procedures, analytical errors etc., which might be included either providing relevant references or a more detailed description.
ln163-165: Same here: add some more information on lab equipment and the lab procedures, which might be included either providing relevant references or a more detailed description. Please, add also information on the calibration of the radiocarbon dates.
ln170: “…from 20 inspections.”
ln173-174: Move “at 1 cm or 2 cm intervals” to the end of this sentence.
ln196:
Results
Figure 2: Move the legend to empty space where it doesn’t overlap with plotted data. The TQ22-C2 seem suitable.
Figure 6: As in Fig. 6b the y-axis for cellulose δ13C is shown twice, please don’t extent the arrow “wetter-drier” over both axes but plot the arrow instead twice; one to each axis. Otherwise, you indicate wetter to drier conditions from –26 to –32 to –26 to –32‰.
Discussion
ln379: See comment on ln16-17.
ln380: “… lateral peatland expansion …”
ln481-484: In order to characterize the quality of freeze-locked OM, there are plenty of studies from ice-rich ancient permafrost deposits such as by Haugk et al. (2022) and references therein.
Haugk et al. (2022). https://doi.org/10.5194/bg-19-2079-2022
Synthesis and conclusions
No comments.
Appendix
No comments.
References
Not checked.
Citation: https://doi.org/10.5194/egusphere-2025-946-RC1
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