Review History


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Summary

  • The initial submission of this article was received on May 8th, 2017 and was peer-reviewed by 2 reviewers and the Academic Editor.
  • The Academic Editor made their initial decision on June 21st, 2017.
  • The first revision was submitted on August 23rd, 2017 and was reviewed by 2 reviewers and the Academic Editor.
  • A further revision was submitted on September 23rd, 2017 and was reviewed by 2 reviewers and the Academic Editor.
  • The article was Accepted by the Academic Editor on October 18th, 2017.

Version 0.3 (accepted)

· · Academic Editor

Accept

The reviewers agreed that you successfully dealt with previous concerns. I agree as well. As noted by reviewer 2, take care to proof your final text.

Reviewer 1 ·

Basic reporting

No comment

Experimental design

No comment

Validity of the findings

No comment

Comments for the author

The authors have made all of the requested revisions. I believe the manuscript may now be accepted for publication.

Reviewer 2 ·

Basic reporting

I have no additional substantive comments- I think that the manuscript could still stand improvement in narrative organization and editing of a few remaining English grammar issues, but to a certain extent this is a matter of preference and relates to the elements of style more than content. As indicated by the editor, further efforts here are not necessary for the publication of this manuscript. I would encourage the authors to just take one last scan for grammar, in particular, as this may improve paper's impact in terms of readership.


The authors have attended to my previous substantive concerns in the last round of review. Good job- I think the manuscript encapsulates substantial work and interesting results.

Experimental design

no additional comments

Validity of the findings

no additional comments

Version 0.2

· · Academic Editor

Minor Revisions

Pay attention to the comments of reviewer number 1 who gave more substantive comments. I agree with those comments and your paper will be improved by dealing with them.

Reviewer 1 ·

Basic reporting

All of the criteria are met, with the following exceptions:

Text added to the manuscript by the authors since the original submission needs editing. I provided suggestions in my review.

Figures 1 and 2 were not in the materials I downloaded for review; but they were part of the original submission's supplementary information.

Experimental design

All criteria are met

Validity of the findings

All criteria are met

Comments for the author

The authors have adequately addressed the reviewers’ constructive criticisms. Specific comments below are largely related to editing of text to improve clarity, with the exception of line 583 (see details below). This conclusion needs to be put into the context of functional redundancy of ecoenzyme expression by microbial communities with different taxonomic composition, given that the authors included a citation about functional redundancy in the introduction of the manuscript.

Specific comments

Line 51 (abstract): change to “Soil communities within both sites …”

Line 53: “… to face up the wet years” is not a phrase commonly used in English. I would change the sentence to something like the following:

However, the community of the site with lower resources (RS) is well adapted to acquire P resources by ecoenzyme upregulation during years with adequate precipitation, suggesting that this community is resilient after drought occurs.

Line 56: change to:

the soil microbial communities of both sites could be vulnerable to drought through C and P co-limitation and reallocation of resources to physiological acclimatization strategies in order to survive.

Line 95: ‘The’ is not needed at the start of the sentence.

Line 370: change ‘AP’ to ‘PME’

Line 418: Figures were not included in the manuscript I downloaded, so I assumed Figs. 1-2 were moved from the supplement of the original submission.

Line 474: Needs editing. I suggest:

These results suggest that the microbial community in the RS soil, with lower resource availability, must reduce growth as a result of: 1) the physiological cost associated with a low reallocation to P-rich ribosomal RNA, as suggested by the growth rate hypothesis (GRH) (Sinsabaugh & Follstad Shah 2012; Sterner & Elser 2002; Zechmeister-Boltenstern et al. 2015) and 2) the required investment of energy towards the acquisition of P in order to produce ecoenzymes (Evans & Wallenstein 2012; Schimel et al. 2007; Wallenstein & Hall 2012).

Line 537: ‘resilient’ not ‘resilience’. I would add the phrase ‘during times of adequate moisture’ at the end of the sentence.

Line 557: I am not sure this statement is accurate. I would change it to:

‘Our results show how values of TERC:N and TERC:P may shift with respect to variation in annual rainfall and different vegetation cover.’

Line 568: Needs editing. I suggest:

Our results for the dry year (2012) showed that the ecoenzymatic activities associated with C and P acquisition were lowest in the RS and G soils. Values for TERC:N and TERC:P were similar between the RS and G soils, suggesting that both sites may be vulnerable to drought.

Line 575: Needs editing. I suggest:

Similarly, increased ecoenzyme activities associated with P acquisition and elevated TERC:P values when the water is not limiting (2013 and 2014) suggest that the RS soil microbial community is well adapted to acquire P resources via ecoenzyme upregulation post drought.

Line 579: Needs editing. I suggest:

We suggested that, under the scenario proposed by Global Climate Change models for desert ecosystems that predict reduced annual precipitation and increased rainfall variability, the microbial community from both sites could be vulnerable to drought events, but the RS soil microbial communities can make adjustments in order to obtain nutrients in wet years, suggesting that this community is resilient post drought.

Line 583: This result would occur only if functional redundancy is lost through change in community composition.

Line 590-597. Needs editing. I suggest:

Soil communities of both sites (RS and G) may be vulnerable to drought. However, the community at the site with lower resources (RS) may have evolved adaptations, such as rapid ecoenzymatic upregulation, under chronic P limitation. This adaptation confers greater resilience within the community to respond to precipitation events post drought. Under the Global Climate Change scenarios for desert ecosystems that predict reduced annual precipitation and an increased intensity and frequency of torrential rains and drought events, soil microbial communities within both sites could be vulnerable to drought through the combination of C and P co-limitation and reallocation of energy and nutrient resources to physiological acclimatization strategies in order to survive.

Reviewer 2 ·

Basic reporting

The introduction still has a few English language issues which I tried to edit- In addition, I'm not sure the communication of the study is quite at a level where the manuscript will make the intended impact. I have included an attached version in which I try to make some edits to the intro to improve the logic/flow of the intro/narrative. The authors should consider these possible edits. Edits/comments are in track changes.

Experimental design

no comment

Validity of the findings

no comment

Comments for the author

The introduction still has a few English language issues which I tried to edit- In addition, I'm not sure the communication of the study is quite at a level where the manuscript will make the intended impact. I have included an attached version in which I try to make some edits to the intro to improve the logic/flow of the intro/narrative. The authors should consider these possible edits-

Version 0.1 (original submission)

· · Academic Editor

Major Revisions

We have two good reviews. Both suggest careful revision to more clearly relate results to the conclusions. I agree with the reviewers that you have overstated your conclusions so reframe the paper to be explicit in this regard. Also you must respond point by point to the other concerns expressed by these reviewers.

Reviewer 1 ·

Basic reporting

Some text, particularly in the Introduction, needs editing by a native English speaker. Specific suggestions to improve clarity are given below, but there are other areas of text where editing could make meaning more clear while reducing length of text. In some cases, clarity could be improved by separating ideas into two sentences (e.g., lines 143-147).

Literature references are appropriate.

Table and figure structures are professional. Raw data is shared.

The paper's theoretical constructs and organization could be improved to better use the results to support the conclusions. The strength of conclusions, as stated, should be toned down. Please refer to the attached document for details.

Experimental design

The scope is appropriate for the journal.

The research question is relevant, but the approach could be better described through re-organization of the text. See the attached document for details.

Data collection met high technical standards.

Methods are described with sufficient detail.

Validity of the findings

The paper has two primary novel aspects. The authors note, in one case, that such results have not yet been reported.

Data is statistically sound.

Conclusions are a bit overstated. Reorganization of text could improve linkage to research questions. See attached document for details.

Reviewer 2 ·

Basic reporting

The authors of this research present interesting findings that are well supported by thorough attention to various measures of microbial biogeochemistry (microbial biomass stoichiometry, enzyme activity, soil nutrient pools) and analysis in a desert ecosystem. The authors demonstrate that desert ecosystems may respond the variability in rainfall in unique ways depending on soil nutrient content (plant cover) (e.g. under wetter conditions an increase in relative production of P-targeting enzymes in RS soils and higher microbial nutrient concentration in G soils) and also in broad overarching ways as well. These responses are observed both in soil microbial mediated boigeochemsitry as well as bacterial community composition. I believe that the content that is presented in this manuscript is of interest in building understandings of microbial community function in these ecosystems with increasing pressures of climate change and precip variability.

I do believe that the communication of this study could stand to improve a bit. I think that the discussion is well related to past studies and prevailing theory, but I think that generally these results are over-interpreted. For example, when one of the wet years has significantly greater enzyme activity in one cover than another and conclusions are drawn about mechanism. I think that the scope of this journal may be okay for this type of study, but I do as the author to include a caveat about the generalizability of their study (being limited). If the study had a more limited scope in its thesis, I think it could be better communicated.



Title:
Unclear what “vulnerability” refers to. Can you think of a title that more reflects the central findings: That microbial responses to variation in annual precipitation depend on soil nutrient status in a desert ecosystem. This is the type of insight that I draw from this study…. And the narrative could stand to improve my having a clear thesis as such.

It appears that this is a discussion of “interannual variation”- so I would specify that in title and after when talking about variation.


Line 39: Please introduce the acronym earlier in the paragraph with parentheticals before using.

Line 80-81: This sentence does not make sense “… are highly enzymatic activity..” ??

Line 83: This sentence does not make sense “In the rainy enzymatic…” ??

Line 132: I would just ask the authors to consider that there could be great functional redundancy with these enzymes (many microbes produce them) and that the change in microbial structure does not necessarily relate to adaptation to different variable precipitation, but just the turnover of microbial communities and the fact that many different microbes can produce the enzymes (unless some sort of correlation is shown between precip->microbial community structure->enzyme activity.

Line 181: word choice… perhaps “dynamic” instead of “aspect”


Lines 510-514: Can you move this up from the discussion to frame the hypothesis- that basically high nutrient environments are more resilient to variability in precip?

Line 220: 2011 was sampled in Feb. Can you make a note that this timepoint was left out of regression analysis- to clarify it is not confounding this results if so.

Lines 292-294: This can go in results

Lines 286-291: First please write out J. Craig Venter Insitute (JCVI) if this is what is meant. Secondly, please include a citation that details the JCVI pipeline methods for sequence processing/analysis.

Experimental design

My other concern is just to ask if the authors could make sure to communicate how they address that other factors other than precipitation change from year to year. For example, is it clear that the soil moisture content actually reflects the differences in annual precipitation? these two things exist on such different scales and it could be soil moisture driving differences rather than interannual variation in precip, per se. In the results- moisture seems to be significantly different between years, and moisture itself could control variation in nutrient dyanamics (and is known to affect enzyme activity) on temporal scales that are disjointed from annual precipitation- and yet the regression models are all focused on annual precipitation (year). pH also changes… The manuscript could better address how variability is annual precipitation is actually synonymous with year and not confounded by other factors and temporal scales.

I don’t believe the study adequately tests responses variability itself, but rather seeks to understand the relationships of variable precipitation with soil/microbial mediated processes. There is no control to test variability over the years or a measure of variability itself, but the study rather show correlations between annual precipitation and dissolved nutrients/microbial nutrient ratios etc. over 3 years. Thus, I believe the manuscript needs to be reframed to communication this and not claim to assess the impact of variability itself (which I think in many sections is okay- but should be attended to). There may be some implications regarding increasing variability in precip with climate change that can be generated from this study…but must be framed as such and not as a study of this in itself.

Validity of the findings

Overall, I think if the scope of the study were more focused on the differences in response to changes in precip across different nutrient regimes, the manuscript would be better communicated.

Please see above in study design for questions of validity in interpretation of the findings

Lines 491-509: No statistics are actually demonstrating any connection between enzyme activity and microbial taxa relative abundances, I think this is a bit too handwavey and should be much more limited if included.

Comments for the author

Overall the authors to a great job of collected and analyzing interesting and compelling data regarding nutrient dynamics, microbial activity, and bacterial community composition in desert soils across two different vegetation covers (soil nutrient status). I think that the manuscript could just be limited in the scope of its findings/interpretation to avoid taking on questions like variability in precip (interannual- which only has 3 years here, etc.) Rather focus on the interesting differences from year to year within the study's two cover types/nutrient levels.

Best

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