Dear Dr Natali,

Many thanks for your response to referee comments and revisions on the manuscript. You have addressed most of the points raised by the referees well I think, and the methods description particularly of belowground stocks is clearly improved. However, I have a remaining issue that has to be clarified before this is publishable (also raised by referee 2). There is some circularity in arguing that vegetation and/or moisture drive belowground C stores, as these parameters are all linked. Correlations are not clearly supported statistically (please see my comments on lines 327/328 below), and you should discuss more carefully the possibility that explaining soil C stores by vegetation and moisture alone is likely to be simplistic.

264-266: I can’t see how you can apply a parametric test with a sample size of 1. Using depth increments within 1 m sections is at best pseudo replication, and not a robust method to determine soil parameters, when true replication is n=1 per soil type. Your figure 5 shows no error bars (which is I think correct), but you can’t present differences between these two profiles as either statistically significantly different or not.

305: Remove space after commas within figures for tree biomass.

307: Do you mean “mostly highly correlated”, or “showed the highest (or best?) correlation”?

327/328: There is a tendency to treat significant correlation between scalars as explanatory variables (distinction of correlation an causation). Here, you suggest that moss and lichen cover “control” soil C content in the top 10 cm, even though the causal link is not clear. It’s possible that soil moisture influences both parameters creating the observed correlation without a direct dependence of these on one another. I also miss an indication of whether the correlations with moisture and moss/lichen cover were significant. Table S3 gives parameter values, but no statistical significance. From Figure 4, it looks as though any correlation would be weak. This is a central point in your results, and has to be supported robustly by statistics. If the correlation is weak (or indeed not significant), then you can not make some of the statements (including in the abstract).

357: You described belowground C pools (to 1 m) as representing 92% of C pools; aboveground C pools should hence represent 8%, not 9%. I know it’s a small (and statistically probably not significant) difference, but for consistency I think these figures should match.

Figure 3: Indicate in the figure caption that thaw depth was measured in July/August.

Table 4: Should the unit for C in permafrost cores not be kg C m-3?

Supplement tables are not well formatted. Please remove horizontal and vertical lines as appropriate. Some lines to separate e.g. sites (or possible cores within sites) are ok.

Best regards,
Jens-Arne Subke

Dear Dr Natali,

Many thanks for your swift reply. I’m happy with your corrections on the manuscript, and only have a very minor editing suggestion for one sentence. In lines 473-475, would you be happy to change phrasing to either “We found that soil samples with higher moisture content also had higher C density, which is likely due to …” or “We found that soil samples with higher moisture content also had higher C density; this is likely due to…”? If so, please proceed with the upload of the final manuscript.

Many thanks, and best regards,
Jens-Arne Subke