Dear Dr Zha,

Many thanks for your responses to referees, who all concur that your manuscript is of interest to readers of Biogeoscience, and of good or even excellent scientific quality. I am satisfied with your response to general and detailed comments, and welcome the inclusion of supplements. These look fine, but to ensure that I can see all changes and edits, I would like to ask you to submit as soon as possible a completely revised manuscript highlighting all changes from the original version. (Please note that I'm not asking for any additional revision, just a final, revised manuiscript that incorporates and higlioghts all reviewer comments.)

With best regards,
Jens-Arne Subke

Dear Dr. Zha,

Many thanks for the revised manuscript. I think that you have managed to incorporate the referees’ comments well. The main message of soil respiration being driven by organic matter in the soil and/or root-derived respiration is now clearer, but I find that there is still confusion caused by your use of the term “substrate”. This tends to refer to recent, root-derived photosynthates, even though obviously any form of organic matter can for the substrate of metabolic activity. This is an ambiguity I found confusing when re-reading the paper.
There is also a tendency to repeat the findings with regards to substrate distribution and phenology, which could be tightened up – I highlight one paragraph in particular below.
Overall I think that this paper can be published in Biogeosciences, provided you can make the further edits outlined here.

With best regards,
Jens-Arne Subke

Detailed comments:
p. 2, l. 7: delete “topographic”; change “flowering-bearing” to “flower-bearing”
p. 3, l. 3: The statement that desert ecosystems cover 45% is not correct. Asner et al refer to arid and semi-arid ecosystems, which is not the same. When cold deserts are excluded, the number reduces further. As your investigation looks at C dynamics in hot deserts (which differ dramatically from those of the Arctic), I would like you to include the appropriate figure for arid and semiarid ecosystems, and excluding Arctic ecosystems.
p. 3, l. 10: Please rephrase: “…, it is necessary to understand…”
p. 3, l. 16: “… exhibit significant heterogeneity as a result…”
p. 5, l. 17/18: Please indicate which direction (i.e. E or W) are lee- and wind-ward.
p. 6, l. 4: Delete “gas”!
p. 7, l. 17: Replace “less” by “fewer”. Also: “analyses” rather than “analysis”.
p. 7, l. 18: This is not clear; I suggest “… were first screened and values beyond the range of -1 and 15 μmol m-2 s-1 (mean ± 5 standard deviations) were removed…”
p. 7, l. 18-21: are the “spurious results” included in the 3% associated with instrument failure and quality control? If not, please indicate the percentage.
p. 7, l. 21: Why were days of rainfall excluded?
p. 8, l. 22: I suggest “only minor” rather than “nominal”.
p. 9, l. 13/14: Rather than giving detailed p-values, simply indicate “p > 0.05”.
p. 9, l. 15; Please switch figures 5 and 6 round so that you refer to them in the appropriate order.
p. 10, l. 21-22: Delete “Thus, we… vice versa.”
p. 11, l. 1-4: This paragraph would benefit from a concluding sentence for your observations regarding topographic position. Something along the lines that topographic position or height within the sand dune per se is a poor predictor of Rs.
p. 12, l. 2/3: This sentence makes no sense. Are you saying that forests and grasslands are not limited by the supply of recent photosynthates? Litter and dissolved organic matter from litter are also substrates! Please make this much clearer.
p. 12, l. 9; “input of Ts and VWC” makes no sense.
p. 12, l. 15: “flower-bearing”
p. 12, l. 15-21: This part of the discussion overlooks (or avoids) the fact that root biomass, litter amount and soil N are closely correlated.
p. 13, l. 12-20; this paragraph does not add anything new that hasn’t been discussed in earlier paragraphs.
p. 14, l. 6: “downed photosynthetic products” makes no sense. Are you referring to labile, exuded sugars “recent photosynthates”, or litter, or both? All of these are photosynthetic products!

Tables 1-3: Please report consistent numbers of significant digits, not fixed numbers of decimal places. E.g. in Table 1: “23.8” for Ts, but more decimal places for values of SWC. I suggest three significant digits for all mean values, but error terms may be fine with only 2 sign. digits, or matching number of decimal places of mean values.
Table 2: Include brackets for error term of N on north-facing slope.
p. 12, l. 5; “flower-bearing”
p. 12, l. 6: “shown”, not “showed”.
p. 12, l. 9-11: “Error bars represent standard errors.” No need of following sentence, as this is explained in the legend.
Fig. 4: State that, where shown, lines are linear regressions with p < 0.05.

Dear Dr Zha,

Many thanks for the quick response. I m now happy to advance this manuscript for publication, pending only a couple of minor edits to simplify and correct earlier changes. Once these have been implemented, this is ready for publication.


p. 12, l 4-8: Please edit: “In contrast, many studies in forests and grasslands report that topographic heterogeneity in Rs can be suitably explained by spatial heterogeneity in Ts and SWC (Kang et al., 2003; Liu et al., 2010)”. (I.e. delete “Spatial variation in Ts and SWC is reported to contribute to the spatial variation in Rs in forest ecosystems.”)

P. 30, l. 9/10: Please edit: “Error bars represent standard errors” (not “Error bar represents…”), and delete “Black color represents for whole period.”

Figure 6 caption still states “Figure 5”!


With best wishes,
Jens-Arne Subke