the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 29 Apr 2026
Simulation of long-term peat accumulation dynamics & vulnerability: Insights from a Pole Forest and Palm Swamp in Amazonia
Abstract. Peruvian peatlands represent one of the largest reservoirs of carbon in Amazonia. This heterogeneous landscape exhibits several types of ecosystems, including pole forest (PF), palm swamp (PS), open peatlands (OP), and seasonal flooding forest (SFF). We apply the HPMTrop_EcoTy model, a novel development that represents ecological succession via bespoke parametrisations of ecohydrological mechanisms, to gain insights into long-term peat accumulation dynamics across these ecosystems and to assess their vulnerability to carbon gain and loss. Model results suggest that carbon accumulation rates in Amazonian peatlands are similar to or greater than those reported for the Congo Basin and Southeast Asia. Peat and carbon accumulation in Amazonia are particularly sensitive to local-scale changes, especially those driven by ecosystem succession. Amazonian peatlands appear less sensitive to precipitation changes, likely due to the extremely high rainfall across the Peruvian Amazon. However, reducing rainfall to levels similar to those of the present-day Congo Basin (45 % reduction) produces an exponential decline in peat and carbon accumulation, suggesting a critical tipping point. Sensitivity analysis shows that PF, the most carbon-dense ecosystem, is the most sensitive, likely because it is rain-fed and therefore more vulnerable to ecohydrological changes, whereas SFF, the least carbon-dense, is the least sensitive. Considering the exceptionally high precipitation in the region, peatland formation appears mainly controlled by local processes such as river migration, which drives vegetation succession linked to peatland development.
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Status: open (until 02 Jul 2026)
- RC1: 'Comment on egusphere-2026-2272', Anonymous Referee #1, 22 May 2026 reply
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Major comments
This is an interesting site-specific modelling study investigating peat development in two Peruvian peatlands. Research on tropical peatlands is critically underrepresented. Therefore, more modelling studies on tropical peatlands are urgently needed. The model is validated against peat presence/depth over time using a single peat core from each site. I am particularly concerned about the lack of validation data. At this stage, it is not possible to say whether the model can reproduce peatland accumulation dynamics. The depth and presence of peat at a particular time point is a great first step to validating the model. However, the depth and presence of peat is not indicative of carbon accumulation rates or carbon storage. The manuscript refers to in situ NPP measurements from other studies. Can this be used to validate the model in the present day? WTD (estimated from precipitation) is the primary driver of NPP in the model. Can this be validated against present day site data? I encourage the authors to validate at least one other model output.
In terms of the structure and readability of the manuscript, much more can be done to improve the flow and readability. There are only five figures in the main text, despite an extensive supplementary material and appendix. The number of figures and tables is relatively low for a manuscript of this length. Many details are omitted from the main text, including a comprehensive description of relevant model processes and I think including more figures and tables in the main text would help clarify several details. It remains unclear which parameters were changed. This is a very exciting study and a wonderful application of the model. With a bit more work, this paper can become a very useful contribution.
Small comments:
L18. Peatland formation is the result of a very slow process spanning thousands of years, during which the material from dead vegetation accumulates a process regulated by climatic and hydrological conditions.
L22. I assume you mean unique or endemic? Can you give an example?
L25. Remove ‘their history and’.
L37. Important how? Carbon-rich? Biodiversity? Oldest?
L40. Here or in the methods? Could you explain how/why these sites have developed to be a pole forest and a palm swap?
L43- L48. Net primary production? How was this measured? Can this be used as validation data in this study?
L67. Large? Do you mean tall? How tall? How thin? What are the dominant aboveground species? What are the dominant peat-forming species?
L70. What is a permanent vegetation plot?
L71. What method was used to collect the core?
L72. Re Åkesson et al. data? Do you use this? Why is it referenced?
L73 – L76. What time periods does ‘initial formation’, ‘middle to later stage’, and ‘most recent stage’ span? What were the drivers of these transitions?
When giving the length of the ‘peat core’, was this the length of the core or the peat section? Did both cores include basal peat? It’s unclear.
L83. Again, pollen, DBD, LOI etc. Are you analysing this data? Why is it referenced?
L85. Again, what were the drivers of the transitions? What is the dominant vegetation today? And the dominant peat forming vegetation?
L95. Here an elsewhere. I don’t see the need to abbreviate ecosystem, palm swamp, and pole forest. It reduces the readability of the manuscript.
L98. Are you calling the new parameterisations, a new model? Is it not just a new application of an existing model? Was any model code changed? If only new parameters, I wouldn’t change the name of the model.
Table 2. Where does this information come from? You’ve derived this from the sampled cores? Does the information become model input? Or validation data?
Figure A1. Simulation results should be in the results section.
Figure 1. Please change labels, core VEN-O2 and NYO-03 to site names. Can you show a photo of the core for both sites? Perhaps this figure can be sperated into two: First figure: The two Maps. The second figure: photo of each site (are these photos of these specific sites or ecosystem type in general. Specific site would be preferable), Photo of each core, radiocarbon dates of each core. It would be good to perhaps use dots in the figure so it is clear, at what ages, the samples were taken .
L105. Can you include equations in SI?
L116. Where can I find the codedataavailability or Table HPMTrop_EcoTy_Parameters.xlsx? I looked throughout the manuscript but could not find it.
Table 1. How does the pollen record vs the peat core agree/disagree? Are the dates radiocarbon dates? How were the ecosystem types determined? Using pollen or peat core visual analysis? Figure A3 and A4 are useful to show you developed the ecosystem types and transitions. It would be great if these were included in the main manuscript alongside the core photos.
L140. Precipitation product was compared to meteorological station data and bias corrected. Can you show this in a figure?
L152. Was this WTD assumption validated against in situ site observations? This is critical to determine whether the simulated changes in NPP and peat accumulation are related to representative changes in WTD.
L155. Please include the equations for NPP, litter, peat depth, peat height, and carbon storage here in the main text. These equations are critical for interpreting the results of this study.
L200. Peat height relative to what?
Fig 4. Core/observed data should be in black. Please then use a solid line for the base simulation with shading to indicate ±25%. Which parameters were changed? Why does some figures have a grid and others not? Please be consistent. Why does the shaded grey patch span across all time period but the caption reads that it represents the Holocene hiatus? Shouldn’t this be vertical? Can you also include lines or discuss over which time periods you expect, based on literature, the Holocene hiatus at these sites?
Discussion: Perhaps, I missed it but a limitation of this study seems to be the reliance of pollen analysis to infer vegetation presence. Pollen records only capture pollen producing plants. Can the authors discuss to what extent non-pollen producing plants likely to have been present at these sites?
Table A1. It's a bit unclear but it seems that these are model input parameters. Without presenting model equations, it's difficult to understand how these parameters are relevant to the study or used by the model. Please provide model equations in the methods of the main text.