Soil Bacteria and Soil Fungi Respond Differently to the Changes in Aboveground Plants along Slope Aspect in a Subalpine Coniferous Forest
Viola Kurm
Round 1
Reviewer 1 Report
In the article titled “Soil bacteria and soil fungi respond differently to the changes of aboveground plants along slope aspect in a subalpine coniferous forest” by He and colleagues aims at investigating the association between the belowground microbial community and the aboveground plant community on different slope aspects in a mountainous region. They found differences in both plant and microbial diversity and community composition between the north- and southward facing slope and a flat valley and several correlations between species richness, community structure and plant biomass, sometimes but not always differing between slope aspect. After performing an SEM they conclude that slope aspect influences the interaction between the plant community and the fungal community.
In general, especially the results and discussion sections are very hard to follow, partly due to structuring, partly due to incorrect language use, and it is therefore difficult to evaluate the merit of this study. From looking at the results I would conclude that it was found that some abiotic factors differ between slope aspects, which influences both plant and microbial community. This does not essentially differ from what was discovered in previous studies.
The article needs major improvements to readability to allow for a more detailed evaluation of its contents.
General
Introduction
The introduction contains many complex concepts, such as the effect of plant diversity on the microbial community and the effect of the microbial diversity and functional groups on plant diversity. In addition, the influence of abiotic factors is mentioned. While being concise is important, I recommend spending some more sentences on explaining these concepts. At the moment they are condensed in very long and hard to understand sentences. See specific comments for some of these sentences.
Sometimes there is a lack of coherence within one paragraph. The sentences are strung together, sometimes explaining different concepts, sometimes the same, but the chain of reasoning does not become clear. This is for example the case in the paragraph in l. 88-109. I recommend rewriting in a way that makes clearer how the individual sentences are connected.
The hypotheses are very vague. If possible, formulate more specific hypotheses. Which differences in community composition do you expect, which correlations (between diversity, specific functional groups?), which responses to plant productivity etc.
Material and methods
The sampling area is quite unclear to me. For example, in L. 144, which rows and lines are meant. Please explain this in more detail also by giving a more detailed description of figure one.
Results
A lot of different correlations were calculated, which makes reading the results rather confusing. I recommend only keeping the most important in the main text and moving others to the supplementary.
Discussion
In my opinion, figures should only be referred to in the results, but not in the discussion.
It would be beneficial to the flow of the paper if the order of the discussion would follow the order of results presented.
In general, this section is extremely difficult to read. The whole article might benefit from concentrating on the most important results and then discussing them one by one. In addition, the sentences should be shorter and more focused to increase readability.
Specific comments
Introduction
The use of “could“ in e.g. lines 54, 57, 68 seems strange. I suggest replacing it with for example “was shown to” or similar formulations.
L. 66 and following: I do not quite understand this sentence. Why would C/N ratio decrease with plant diversity and how would that promote niche differentiation? Perhaps the authors could clarify and possibly split this sentence into several to explain in more detail.
L. 72, 73: I do not quite understand how increased fungal diversity increases symbiotic mycorrhiza. Also the cited article does not include this.
L. 80-82: The cited article shows that pH impacts the correlation between plants and microbial diversity.
L. 117: What are fragile habitats?
Material and Methods
L. 177: Where is Fig. 1B?
L. 185-193: When not describing the method in full, please give a reference.
L. 220: How many sequences were identified? 15? 070? Or 916? I assume something went wrong in the formatting there, as well as in the following lines.
Data analysis: Was any filtering applied to the bacterial and fungal sequencing data, rarefaction or calculation of relative abundance? I recommend to at least use one normalization method to account for differences in sequencing depth.
Results
L. 319, 320: Is this the same community composition as already mentioned in L. 312, 313? If so, please remove.
L. 350: This sounds a bit as if you investigated the correlation between the bacterial and fungal community composition, which I assume was not the case. Please rewrite.
Fig. 7: What was the reason that so many different diversity measured were correlated with each other?
Fig. 9: What do the numbers on the arrows denote?
Discussion
L. 427: Please restate the hypothesis.
L. 445: What do you mean by “incomparable”? That it could not be compared or that the results differ?
L. 458, 459: Less extent compared to what?
L. 465-469: I am sorry, but I do not understand the sentence at all. Please rewrite.
L. 484-492: Please do not reiterate all results here, but rather give a summary of the most important results.
L. 492-493: closer compared to what?
I recommend language editing. Especially the use of the words “could” and “would” should be critically reviewed.
Author Response
Please see the attachment.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
The research (Soil bacteria and soil fungi respond differently to the changes of aboveground plants along slope aspect in a subalpine coniferous forest) investigates the relationship between the aboveground plant community and belowground soil microbial communities with the change of slope aspect.
1. In the abstract authors mentioned that Soil bacteria were determined based on 16S rRNA and soil fungi on ITS rRNA, fungi based on what???
2. Why the authors constructed the gene sequence area into bacteria only (16S rRNA), while they perform the fundamental research on bacteria and fungi?
3. In DNA extraction, amplification, high-throughput sequencing, and bioinformatics analysis, authors only mentioned the bacteria 16S rRNA and discard the 18S rRNA of fungi.
4. In the determination of soil properties authors said that The protocols introduced by Lu (2000) were adopted. The reference is missing add it to the manuscript.
5. In the determination of soil properties, the information’s about N and P analysis is very brief, authors must include the proper information’s about the analysis.
6. What are the potassium concentrations in the soils?
7. Why is the lowest species richness found in the north-facing slope, however, the region has high organic matter than the flat site.
8. Figure 5. It has a bad resolution the name of the microbes is unclear.
9. The authors need to correct and revise the reference list individually to meet the journal requirements.
The whole research needs English editing and grammar correction
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
Unfortunately, I cannot comment further on this manuscript, since it is too difficult to understand. I strongly urge the authors to improve the quality of English.
I strongly urge the authors to improve the quality of English.
Author Response
Dear Editor and Reviewers,
We have improved the English quality of our manuscript as required. We have been submitted the manuscript to the MDPI English Editing to obtain the corresponding revised manuscript, and then made modifications according to our manuscript needs. The revised part has been highlighted in our manuscript.
Author Response File: 
Author Response.docx
Reviewer 2 Report
The author enhanced the manuscript in a good way and gave sufficient answers to the questions.
The manuscript needs language revision by a native speaker.
Author Response
Dear Editor and Reviewers,
We have improved the English quality of our manuscript as required. We have been submitted the manuscript to the MDPI English Editing to obtain the corresponding revised manuscript, and then made modifications according to our manuscript needs. The revised part has been highlighted in our manuscript.
Author Response File: Author Response.docx
Round 3
Reviewer 1 Report
Another round of English editing should be considered. I actually encourage the use of shorter sentences, which will probably be less prone to mistakes.
Introduction
L. 59-61: Please clarify what is meant by positive changes in composition and structure. What is considered positive?
L. 71-75: Please clarify this sentence. What is meant by “a mechanism of negative density dependence that inhabits the abundance…”?
L. 78-80: Also this sentence does not seem correct to me. Consider: …”…the impact of soil pH…” and “…this impact was…”
Material and Methods
I miss how the correlations were calculated.
L. 211: Please explain how 16S rRNA was extracted. I know of no method to specifically extract one RNA sequence.
L. 212: amplified instead of amplificated.
Results
L. 309-313: Please correct this sentence with respect to grammar.
Fig. 7: There is unfortunately no explanation on which kind of correlations were done, but for all the R2 is extremely low. Also from looking at the data-points most of the correlation results are tenuous at best. When evaluating correlations, one should not only take the p-value into account.
Fig 8: See comment on Fig. 7.
Discussion
L. 478: Please rewrite “poor nutrients of soil”.
Section 4.2.: Since the correlations were very weak, as indicated in above, I do not see strong support of the second hypothesis.
L. 502- 503: Please correct the grammar of this sentence.
L. 510-515: Please revise and correct the grammar.
Conclusion
L. 524: What does “correlatedly change” mean?
L. 526-528: please revise in terms of grammar.
Another round of English editing should be considered. I actually encourage the use of shorter sentences, which will probably be less prone to mistakes.
Author Response
Introduction
Point 1: L. 59-61: Please clarify what is meant by positive changes in composition and structure. What is considered positive?
Response 1: We changed this expression as “correlated changes”.
Point 2: L. 71-75: Please clarify this sentence. What is meant by “a mechanism of negative density dependence that inhabits the abundance…”?
Response 2: We change this to be “a mechanism of negative density-dependence that checks the abundance…”. And we cite an explanation of this in the following for reference.
Negative density-dependence, or density-dependent restriction, describes a situation in which population growth is curtailed by crowding, predators and competition.
Point 3: L. 78-80: Also this sentence does not seem correct to me. Consider: …”…the impact of soil pH…” and “…this impact was…”
Response 3: We corrected this with “this impact was generally detectable across most environments”.
Material and Methods
Point 4: I miss how the correlations were calculated.
Response 4: We added a sentence as follows.
To examine the relationship between aboveground plant community and belowground soil microbial communities, linear regression was performed to evaluate the correlations of plant richness, aboveground total basal area, and plant community structure with species richness, diversity index and community structure of soil bacteria and fungi, respectively.
Point 5: L. 211: Please explain how 16S rRNA was extracted. I know of no method to specifically extract one RNA sequence.
Response 5: We are sorry for this misunderstanding expression. We changed to this to be “16S rRNA gene”. In addition, we also modified this in the abstract.
Point 6: L. 212: amplified instead of amplificated.
Response 6: Thanks. We agreed to using the word amplified.
Point 7: L. 309-313: Please correct this sentence with respect to grammar.
Response 7: We have corrected the grammar.
Point 8: Fig. 7: There is unfortunately no explanation on which kind of correlations were done, but for all the R2 is extremely low. Also from looking at the data-points most of the correlation results are tenuous at best. When evaluating correlations, one should not only take the p-value into account.
Response 8: We have added a sentence to explain that the linear regression was performed to obtain correlations showed in Fig. 7 (and Fig. 8 as well). The extremely low R2, especially when the data of the sites put together, was the result of discretion of dispersion of those data. The significant revealed by the p-value we assumed that there was a general trend of correlations.
Point 9: Fig 8: See comment on Fig. 7.
Response 9: Thanks again for these two comments. When we review these two figures, we noticed that the unit of aboveground total basal area (m2 ha-1) was missing, and we have added it in the figure captions.
Discussion
Point 10: L. 478: Please rewrite “poor nutrients of soil”.
Response 10: Here we changed to “soil of low nutrients”, or it may be “low-nutrient soil” as well (in our revised line 482). And we also changed it in the introduction accordingly.
Point 11: Section 4.2.: Since the correlations were very weak, as indicated in above, I do not see strong support of the second hypothesis.
Response 11: We appreciate this comment. But, by taking into consideration of the result that soil bacteria and soil fungi responded differently to the aboveground plant productivity, we think our second hypothesis can be supported, and we did not say that the evidence strongly supported this hypothesis.
Point 12: L. 502- 503: Please correct the grammar of this sentence.
Response 12: Done.
Point 13: L. 510-515: Please revise and correct the grammar.
Response 13: We have separated this sentences into three short ones.
Conclusion
Point 14: L. 524: What does “correlatedly change” mean?
Response 14: Thanks. We changed to be “correspondingly change”.
Point 15: L. 526-528: please revise in terms of grammar.
Response 15: This has been done.
Comments on the Quality of English Language
Another round of English editing should be considered. I actually encourage the use of shorter sentences, which will probably be less prone to mistakes.
Response：Thanks. We have taken your suggestions to revised our sentences that may lead to misunderstanding.
Author Response File: Author Response.docx
