the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 22 Apr 2025
The oxygen budget of a peatland – new approach to estimating ecosystem oxidative ratio
Abstract. The oxidative ratio (OR) of an ecosystem in the terrestrial biosphere is defined as the ratio of the O2 released from that ecosystem to the CO2 adsorbed by that ecosystem. This study proposes that the OR of a terrestrial ecosystem could be calculated for the C budget of a peatland environment where stoichiometry and thermodynamics are constrained. Using detailed elemental analysis within an ecosystem with a known C and N budget it is possible to understand the amount of O2 consumed.
The study shows that, for the study site, although the majority of the O2 is consumed in the processing of organic-C (68 %), 32 % of O2 consumption is due to oxidation of NH4. The total amount of O2 consumed by organic C processing is not dependent upon the pathway after surface peat formation: O2 consumption is independent of production of DOC or CH4 or of deep peat. This approach shows that allowing for stoichiometric, energy and energy transfer efficiency constrains the ecosystem OR = 0.88. The calculated OR is consistent with disproportionation of C occurring in the environment. The implication of OR < 1 is that the annual flux of C to the terrestrial biosphere has been underestimated by 12 %.
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Status: final response (author comments only)
- RC1: 'Comment on egusphere-2025-1469', Anonymous Referee #1, 26 Nov 2025
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RC2: 'Comment on egusphere-2025-1469', Anonymous Referee #2, 04 Jan 2026
I cannot recommend this manuscript for publication. According to the General Terms for EGUsphere, at www.egusphere.net/about/general_terms.html, preprints should not have been published before. Figures 1 & 2 and much or all of Table 1 were published in Worrall et al. (2022), which they cite. I urge the editor to apply a plagiarism test to this work, before requesting further review. If JGR-Biogeosciences has provided consent to have their copyrighted materials reproduced here, then the overlaps (repetitions) should be removed before review, in my opinion.
Citation: https://doi.org/10.5194/egusphere-2025-1469-RC2 -
AC2: 'Reply on RC2', Fred Worrall, 15 Jan 2026
To further clarify, I have attached a pdf where I have screenshotted Figure 1 and 2 and Table 1 from this submission against those from Worrall et al. (2022) to show that for the Figures they have been redrawn; re-arrowed and colours and annotation altered. Ultimately, given that the approach in this study uses the same conception of the C budget as in previous studies of this catchment then there will always be similarity. But we did redraw both figures.
Equally, for Table 1 you will see the caption has been extended, the format altered, and the note removed. It is true that the order of samples is the same. Obviously, we cannot change the values in the Table as we are clear in the text that we are using the compositional data from the previous study. However, to avoid any issue I can modify the table further and happy to change the Table caption to make it clear, as written in the manuscript, that there is no new sampling or analysis in this study and it is a
Table 1. Median composition of the carbon pools examined in the study, with variation indicated by the 95th percentile range. Median stoichiometry is expressed relative to nitrogen content, except for cellulose, which is expressed relative to carbon. All composition data are as reported in Worrall et al. (2022).
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AC2: 'Reply on RC2', Fred Worrall, 15 Jan 2026
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AC1: 'Reply on RC2', Fred Worrall, 15 Jan 2026
We did not think that we had plagiarised or that this was plagiarism - the original source was cited in the text,, but to avoid any doubt an any copyright issue we are very happy to substantially redraw both diagrams and to rewrite the figure captions to:
Figure. 1. A schematic diagram of organic matter fluxes and reservoirs, with each arrow representing a carbon flux and boxes being the organic matter reservoirs (modified from Worrall et al., 2022).
Figure. 2. Map of the study catchment. CHS is Cottage Hill Sike, the stream water sampling location. Numbers refer to altitude in metres above sea level (modified from Worrall et al., 2022).
Citation: https://doi.org/10.5194/egusphere-2025-1469-AC1
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General
This paper proposes a method to estimate the oxidative ratio (OR) combining stoichiometry, thermodynamics, and elemental budgets, which is a novel approach. They apply this method to data they had gained in previous studies from a blanket bog in north England. They find an OR of 0.88 for this site, which is much lower than previously found and conclude that this could lead to an underestimation of the terrestrial carbon sink of about 12%. They also conclude that 32% of the O2 consumption is due to oxidation of NH4+. The general feeling is that the method proposed could be a valuable attribution and would be good to propose a way to use this to come to an estimate of the global OR. However, I have great concerns about the validation and the scaling of the method in this paper (see below).
In general I would say the method, and thus the paper, has much potential, but I would not recommend publishing it unless major changes are made in the validation and scaling of the method.
Concerns
There is an uncertainty analyses done based on the elemental analyses and Eg but they haven’t reported this in the paper. So, it’s not clear what the uncertainty of the OR is! Thereby, there are many more uncertainties. For instance, the C-budget (equation x), where each component has its uncertainty (I find 22% carbon stored as peat also unrealistically high). There are different possibilities of TEA, what would have happened if a different electron acceptor dominated? Denitrification and nitrogen deposition rates, what are the possible ranges for that? I was also wondering about the methanogenesis, this can also be done via the hydrogenotrophic pathway, did you consider that as well? A kind of sensitivity analyses about which elements influence the OR the most would have been useful as well.
There is also no validation done on the method. It is probably hard and expensive to do above-ground OR measurements, but isotopic validation or nitrate and sulphate concentrations measurements could have been done. Another option would be to apply this method where there are measurements from OR available.
The authors could have tried to apply the method to different ecosystems. Peatlands only cover 3% of the world’s land surface, and blanket bogs are even a rarity among them. They are different in the way they store carbon and how nutrients cycle in the system. So to see if the global carbon uptake would really change by applying a different method, you need to scale this to other systems. Or otherwise, don’t make a statement about the implications of the found OR on a global scale.
The paper is also a bit hard to read because they refer to other papers but don’t give a short well understandable summary. For a better understanding, I would highly recommend extending the descriptions of the methods and assume less inside information from your reader. I’ve made some suggestions below.
Detailed comments
L23: Mention what kind of site (peatland, blanket bog)
L88: Explain this a bit more, what ranges or units and how is it determined
L126: Lann = Laan
L138: These are not recent studies, see e.g. Evans et al. 2021, but there are many more!
L145-147: Explain a bit better why this is not sufficient
L208-209: It’s not so clear what is meant with how surface peat can become deep peat with these conversions. Could you explain this a bit better?
L220: terminal electron acceptor (TEA)
L229-231: Explain where these data come from (citation) and where you can find the ranges.
L 259: give a short description of how the carbon budget was established (flux measurements for 18 months e.g.).
L263 (eq X): match the uncertainties with the numbers above.
L346: What about the hydrogenotrophic pathway?
L381: make clear that the organic matter fluxes are estimated
L480-482: You cannot extrapolate this OR to a global scale