Dear Dr. Exbrayat,

Many thanks for the revised manuscript.

You manage to address most of the comments made by the referees. However, I think a stronger statement of your actual objective in this research is needed, as requested by two of the referees. You should make it clear in the introduction why you have undertaken this exercise, i.e. state explicitly what the purpose of your paper is, and what is hoped to be learned. The final paragraph of the introduction gives an outline of what you do, but not a strong enough sense of your motivation and aims.

Please revise the manuscript on this particular point that I think will help readers understand better what it is you are trying to achieve.

Many thanks,
Jens-Arne Subke

Dear Dr. Exbrayat,

Many thanks for submitting the revised manuscript, and also for responding quickly to my request for more work on the introduction. I think that the revised manuscript has improved on the initial submission, but would like to seek the views of some of the reviewers on the revised paper.

With best regards,
Jens-Arne Subke

Dear Dr. Exbrayat,

First off, apologies for the delay. I have been travelling last week and hadn't had time to send you comments beforehand. I have received feedback from two referees on your revised manuscript. Whilst one is satisfied that their comments have been addressed well, one remains critical of the suitability of your methods and conclusions drawn. I have re-read the manuscript and agree that the applicability of your simplified modelling approach in cold biomes where freezing conditions have significant impacts on carbon cycling does not appear robust. Please carefully address all points raised in the reviewer’s statement below. I agree with the referee that the mounting number of caveats for using a simplified model structure limits the real insights we can gain from this exercise.

With best regards,
Jens-Arne Subke



Referee’s comments:

I feel that my main earlier criticisms of the paper aren't fully addressed in the revised manuscript. In particular, I feel strongly that the horizontal axis in figure 5 should be restricted to temperatures above the freezing point; since the authors acknowledge that they are not trying to address freeze/thaw processes it is misleading to include results in the range over which their assumptions do not hold. And the same goes with the zonal-mean profiles; it is insufficient to just say that one's model doesn't treat freeze/thaw or permafrost processes but that it nonetheless makes predictions about soil C changes at high latitudes. Better to mask out the high latitude regions and say that the simplified model is not appropriate for making predictions over that domain. This issue is of primary importance; what I would have suggested the paper could do if it had made an attempt to get the processes behind the high latitude soil C correct would be to use the current modeled vs. HWSD latitude profiles in soil C as a further constraint on the Q10 (beyond just the global integral, which is clearly a weak constraint) to reduce uncertainty; however this is not possible without some such detail. Lastly, the issue of approximating multi-pool systems as single-pool systems is important as well, and I don't think the authors have thought enough about what the implications are of making this assumption to their results.

Ultimately, my reaction to this paper is that the qualitative results are fairly obvious -- that increasing k leads to increasing initial soil C, and that there is a large degree of uncertainty on the response to warming based on k and how sensitive the decomposition is to temperature. But the degree of oversimplification in the single-residence time, single-Q10 model means that the qualifications to any more quantitative results are so high as to render them not useful. And dismissing these issues as side concerns I think risks creating further confusion in the community about what we do and do not know about soil C. So without more insight from the analysis I would not support publishing the manuscript in its current form.

Dear Dr Exbrayat,

Many thanks for the revisions on the manuscript I thin that you have now included sufficient explanations/caveats to illustrate what you want to (or don;t want to) achieve in your study. I am happy for it to be published subject to a small number of technical corrections and edits, listed below.

With best regards,
Jens-Arne Subke


Corrections:

L 29: Comma after “outliers”

L 31: Either remove comma after “carbon”, or add a comma after “change”.

L. 38: Not sure if “recent” is appropriate for the C4MIP Model Intercomparison, which is about 9 years back now.

L 56: either “it lacks” or “because of its lack of”

L. 112 and onwards – please make sure equations appear legibly in the PDF version of your anuscript

L152: This sounds like a response, rather than a description of methods – I suggest rephrasing, e.g. “While a multiple pool structure would provide diverging results, …”

L. 460-461: I can’t make sense of this sentence; is the hyphen meant to be there? Please rephrase/correct.

Please explain abbreviation of “Harmonized World Soil Database” in Figure captions