|The paper describes an interesting field experiment with interesting and relevant results, but the structure is difficult to follow, which makes the manuscript as a whole a struggle to read. The use of poorly-described acronyms persists, it seems as if the authors have invented their own language for describing the field site. The English usage is fine, but the results and discussion section badly needs restructuring for clarity. It just says things, often without support, and certainly with little internal structure to help the reader. Simply replacing this section with separate results and discussion sections – and (please) removing all extraneous information and assumptions (the list below is partial) would cut many pages from the manuscript and make it a pleasure to read and a valuable contribution to this understudied field.|
On line 36, low air temperature does not necessarily imply C sink and in the following sentence the carbon accumulation is partly attributable to the permafrost itself making C (largely) unavailable for respiration.
The end of the first paragraph could use references beyond those of Schuur et al. (not that these aren’t good references).
With respect to the statement on line 50 note http://www.pnas.org/content/112/9/2788.short
One may argue with the statement ‘The influence of temperature on CO2 cycling processes in the Arctic has been well studied (Belshe et al., 2013)’ given uncertainties with respect to permafrost
With respect to the statement on line 99, note http://iopscience.iop.org/article/10.1088/1748-9326/9/8/085004/meta to the extent that the observations noted in this paper can be used as a surrogate for long-term ecosystem changes.
Awkward wording on line 112: As a continuation of analysis hydrological manipulation
The methods section is written nicely, but what constitutes WTD low?
Subheader 2.2 should be plural
If the UGGA was used why are only CO2 flux data presented?
Space between 3 and sigma on line 200.
Personally I find it interesting if not a bit inefficient to parameterize a model usef for remote sensing for surface fluxes. From this standpoint, which references suggest the prescribed temperature parameters? Please use the multiplication sign or nothing at all rather than the dot which may be taken to mean the dot product. Also, how were the MODIS data used? The pixel may be too big to see relevant effects and at any rate to properly use modis the values around any given point should be averaged with it due to uncertainties in reshaping the ellipsoidal return function to a square(ish) pixel.
‘Eriophorum a.’ is uncommon usage. Use instead ‘E. angustifolium’. These and other errors make me question if all of the coauthors contributed to this version of the manuscript.
Please quantify ‘EriophorumShrub’ and ‘CarexShrub’. An explanation may appear possibly around line 405 but it’s certainly not quantified in the text.
I’m not sure that bootstrapping is the best way to estimate parameter uncertainty in this case. I recommend noting http://www.fasebj.org/content/1/5/365.full.pdf (http://www.fasebj.org/content/1/5/365.short)
Personally I feel that the results and discussion section would read much more nicely if separated into results then discussion. Section 3.2.2 is a particularly egregious example of a section that is difficult to read in the context of a long combined results and discussion section that should be restructured for clarity.
The paragraph beginning line 355 says little and is not supported by data.
The paragraph on line 360 is expository and belongs in the introduction or elsewhere.
The discussion of C:N ratios on line 364 was somewhat surprising given the topic of section 3.2.2: soil temperature and TD effects on CO2 fluxes.
The paragraph beginning on line 403 is confusing in part because of the insistence on using poorly defined acronyms like ‘control_low’ which probably reflects internal dialogue about these treatments rather than something that a reader can hope to understand. A figure might help, or a table of abbreviations.
The statement on line 426 is qualitative.
What is a ‘first vegetation effect’ on line 428?
What does ‘stabilize’ mean in the context of line 444. Do plants really ever stabilize?
The statement on line 445 doesn’t make sense. Note also this notion of ‘stabilization on line 449 which continues to not make sense.
Regarding litter added to the soil on line 474, can you be sure? What if shrubs have higher leaf area index?
The statement on line 504 doesn’t make sense.
From the conclusion, the results are nice and simple to follow. It’s a shame that the results and discussion section doesn’t reflect this. The first couple paragraphs should be the beginning of a restructured discussion section and the last paragraph of the conclusions should serve as a succinct conclusions section.
Table 1 is nice.
What does anything in Tables 4 and 5 mean?
Red and green should not be used simultaneously if avoidable (and it’s certainly avoidable) in figures 4, 6, 9, and S1.
Figure 9 isn’t particularly revealing, it may make sense to study the relationship between changes in air pressure and flux.