Large-Scale Biochar Incorporation Does Not Necessarily Promote the Carbon Sink of Estuarine Wetland Soil

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The authors conducted a field experiment to investigate the effect of biochar application on carbon sink in wetland soil, which is significant for CO2 sequestration and estuarine wetland development. However, the experiment was not replicated, making it impossible to perform any analysis of variance or conduct multiple comparisons. The data presented in figures 1, 2, 3, 4, and table 1 lack scientific soundness, and therefore, the results and conclusions derived from them have little academic value.

Comments on the Quality of English Language

The readability, grammars, and words should be improved further.

Author Response

1. Comments: The authors must improve the paper to make the content succinctly described and contextualized with respect to previous and present theoretical background and empirical research on the topic.

Response: Thanks for this suggestion. We have shortened many paragraphs and make the content keep to the point. Especially for the parts of Introduction and discussion, we corrected several statements to add theoretical background and present study about this article. We also improved the design, questions, hypotheses, methods and results to make them more clearly.

2. Comments: the experiment was not replicated, making it impossible to perform any analysis of variance or conduct multiple comparisons. The data presented in figures 1, 2, 3, 4, and table 1 lack scientific soundness, and therefore, the results and conclusions derived from them have little academic value.

Response: Thanks for your suggestion. We have improved the figures and tables to make them more concise and sound. 

Thaks a lot for your checking and comments, your suggestion is extremely helpful to make our paper more logic, succinct and scientific. Furthermore, we have used English editing service by MDPI to improve the whole content.

Reviewer 2 Report

Comments and Suggestions for Authors

Why authors have used 50% and 30% of biochar. its very high dose.

Its better to add some key findings of the current study in values form in the abstract portion. 

Authors have used straw biochar in the introduction section, which type of straw was used

Please cite reference for biochar production method

Authors needs to mention all biochar levels in article abstract.

Please strongly modify your novelty statement. 

Please revise this "A PowerSoil soil DNA isolation kit ("

Please think about figure 4 x-axis

Please check the error bars of figure 3

if possible, please mention some results in values in conclusion section. 

Comments on the Quality of English Language

Check the grammatical mistakes 

Author Response

1. Comments: Why authors have used 50% and 30% of biochar. its very high dose.

Response: Thanks for this question, this rate of biochar is decided after our several years’ study and pre-experiments on biochar incorporation to soil. We previously used smaller rates such as 10% and 15%, the effects of biochar incorporation to soil respiration and carbon sink is negligible and not obvious. Only excessive rates of biochar incorporation can reveal the large scale of biochar incorporation effects on soil. For another, small rates of biochar incorporation have been many studied in other articles, and this paper is to assess the influences of large scale of biochar to soil carbon cycle. These are reasons that we used 30% and 50%. Furthermore, at present, the rate of biochar incorporation in the revised manuscript has been changed to biomass but not percentage.

2. Comments: It’s better to add some key findings of the current study in values form in the abstract portion. 

Response: This suggestion is meaningful, so have add the key present findings in the abstract to highlight the significance of our study.

3. Comments: Authors have used straw biochar in the introduction section, which type of straw was used.

Response: the type of straw is soybean (Glycine max (Linn.) Merr) which is mentioned in L134, P6, and we also added the genotype of soybean at L257, P5.

4. Comments: Please cite reference for biochar production method

Response: the reference of“Yin Q.X. (2020). Study on enhancement model of carbon sink function of chongming dongtan reclamation wetland based on straw returning. Doctoral thesis, Tongji University, China, Shanghai. ”was cited in the main text P5.

5. Comments: Authors needs to mention all biochar levels in article abstract.

Response: Thanks for this suggestion, so have improved the abstract and added more data statements including rates of biochar.

6. Comments: Please strongly modify your novelty statement. 

Response: Thanks for this suggestion, so have significantly modified our novelty statement.

7. Comments: Please revise this "A PowerSoil soil DNA isolation kit ("

Response: Thanks for this suggestion, the kit name is strictly followed by manufacturer’s brand.

8. Comments: Please think about figure 4 x-axis and check the error bars of figure 3

Response: the figures and tables have all been checked and improved.

9. Comments: Please if possible, please mention some results in values in conclusion section. 

Response: Thanks for this suggestion, so have improved the conclusion part by adding vital statistical results.

Thanks again for your advice, and we also used English editing service by MDPI to improve the whole conent.

Reviewer 3 Report

Comments and Suggestions for Authors

This study reported that the incorporation of large scale of biochar unnecessarily promotes carbon sink of estuarine wetland soil. Authors found that the introduction of biochar to wetland soil ruins anaerobic condition, which may in turn accelerate soil organic carbon degradation. These findings are important to people for understanding the comprehensive biochar environmental effects. It can be considered to be accepted by this journal but it needs to be revised remarkably.

 

(1)   In the title, how to understand the word “unnecessarily”? The meaning of it is “needless”, thus it is strange to use this word in the title.

(2)   In the abstract, there is no any data! Authors must provide some key data for the statement of their main conclusions. The addition rate of 30% and 50% are ambiguous. What proportion is the mass of biochar? Why authors chose such large rates? If you added 50 kg biochar into 100 kg soil, that was unimaginable, because biochar is much lighter than soil.

(3)   Although the biochar stimulated the soil respiration and resulted to more CO₂ release, the authors should consider the carbon introduced by the biochar itself, when you calculated the total carbon storage.

(4)   Why you called the control soil without any biochar as “BK”, this maybe confused.

(5)   Section 2.2, the weight ratio must be clarified.

(6)   “The treated soil was backfilled to the marked spot in Chongming Dongtan wetland and soil with different treatment was separated with boards to avoid soil interaction.” The samples were backfilled into soil. How to simulate the wetland system? Was the environment dry or wet?

(7)   Do not use the abbreviations in the separate part, for example, abstract, section title, conclusion. 2.3.2, what is “SR”?

(8)   The quality of the figures should be improved such as Fig. 5, Fig. 6 and Fig. 7. They can be combined.

(9)   5. Conclusions, “the large incorporation rate (50%) of biochar to soil induced heterotrophic microorganisms”? This sentence is not finished.

(10)  The full language needs to be further modified.

Comments on the Quality of English Language

 The full language needs to be further modified.

Author Response

1. Comments: In the title, how to understand the word “unnecessarily”? The meaning of it is “needless”, thus it is strange to use this word in the title. 

Response: Thanks for this question. The word “unnecessarily” means “not always”, “maybe not”. The more accurate statement should be “not necessarily” by Collins English Dictionary.

2. Comments: In the abstract, there is no any data! Authors must provide some key data for the statement of their main conclusions. The addition rate of 30% and 50% are ambiguous. What proportion is the mass of biochar? Why authors chose such large rates? If you added 50 kg biochar into 100 kg soil, that was unimaginable, because biochar is much lighter than soil.

Response: Sorry for the ambiguous description. We have rewrote several part of Abstract and added vital statistical statements. Furthermore, the rate of biochar is decided after our several years’ study and pre-experiments results. We previously used smaller rates such as 10% and 15%, the effects of biochar incorporation to soil respiration and carbon sink is negligible and not obvious. Only excessive rates of biochar incorporation can reveal the large scale of biochar incorporation effects on soil. For another, the rate of 50% or 30% is the biomass of fresh straw (before carbonization) incorporated to the soil, the accurate biomass of carbonized straw (biochar) should be multiplied with straw carbonization yield rate (36.57%), thus the biochar incorporation rate in this paper is 0.7%, 1.83%, 3.66%, 10.97% and 18.29%. To make it clear, we have used biomass of biochar incorporation instead of percentage. The correct description about rate of biochar and the biomass has been added in the Materials and Methods part and through the Results and Discussion part.

3. Comments: Although the biochar stimulated the soil respiration and resulted to more CO₂ release, the authors should consider the carbon introduced by the biochar itself, when you calculated the total carbon storage. 

Response: This suggestion is meaningful. To make the results more comprehensive, we added the discussion as below in the main text.

4. Comments: Why you called the control soil without anybiochar as “BK”, this maybe confused. 

Response: Thanks for this reminding, so the control group is changed to ‘CK’.

5. Comments: “The treated soil was backfilled to the marked spot in Chongming Dongtan wetland and soil with different treatment was separated with boards to avoid soil interaction.” The samples were backfilled into soil. How to simulate the wetland system? Was the environment dry or wet?

Response: Thanks for this question, the wetland system is simulated with field natural climate including precipitation, weather and sunlight, etc. In addition, the soil that biochar incorporated is also derived from Chongming island natural soil.

6. Comments: Do not use the abbreviations in the separate part, for example, abstract, section title, conclusion. 2.3.2, what is “SR”?

Response: Sorry for the mistakes, so have used the full name in the abstract and conclusion part. “SR” is soil respiration.

7. Comments: The quality of the figures should be improved such as Fig. 5, Fig. 6 and Fig. 7. They can be combined.

Response: Thank you for this suggestion, we have improved all the figures and combined several of them.

8. Comments: Conclusions, “the largeincorporation rate (50%) of biochar to soil induced heterotrophic microorganisms”? This sentence is not finished.

Response: Thanks a lot, and the whole conclusion has been improved.

9. Comments: The full language needs to be further modified.

Response: Thanks for the suggestion, so have modified the English writing using English editing service by MDPI.

Reviewer 4 Report

Comments and Suggestions for Authors

Journal: Sustainability (ISSN 2071-1050)

Manuscript ID: sustainability-2603416

Type: Article

Title: Large scale of biochar incorporation unnecessarily promotes carbon sink of estuarine wetland soil

Authors: Mengdi Xie , Xiaojuan Lu , Han Wang , Xiaohua Fu , Lei Wang *

 

 

The present research manuscript topic is investigated in the literature, and there is a very few of reference published. However, this paper gives significant contribution to the current knowledge in related field. The data are sound and it deserves to be published, after major revisions.

 

 

Overall Recommendation: Major Revisions

Prepare response letter with point-to-point replies to each comment.

 

Abstract:

1)      Abstract is not written as per Journal Format.

2)      Problem statement is missing/not well-defined.

3)      An abstract should be concise self-contained summary, should include the background / objective, purpose of the study (including its statistical significance), methods, results and conclusion in one paragraph. Need improvements.

 

Keywords:

4)      Keywords should not be the same as mentioned in the title or abstract.

 

.

Introduction

 

5)      Authors completely failed to develop the hypothesis with reference to title and objective, in the introduction section.

6)      Use www.turnitin.com to find and eliminate unnecessary self-repetition and any copied text.

7)      Don’t use introduction as second window of review of literature.

8)      Run spell check and proof the manuscript to avoid spelling mistakes and grammatical errors.

 

Materials and methods

9)      The text has many typing and grammatical errors, capitalization issues. English style and language requires a profound revision. However, the readability of the manuscript needs to be improved, preferably carefully reviewing by a native English speaker. All proper nouns must be abbreviated. Abbreviations must be described completely at first mention with brackets. Don’t start a sentence with an abbreviation here.

 

10)  Please add details for analytical methodologies to make it reproducible.

 

11)  Quality assurance of data is mandatory!!! How many batch, repeats, chemical grade and for used instruments manufacturers’ user manual and instructions were strictly followed or not!!!

 

12)  Add suitable published reference for statistical software used

 

Results and Discussion

 

13)  Data is sound one. It deserves to be published.

 

14)  Discussion needs improvements. Please cite Figure No. or Table No. in brackets at suitable places for a better connectivity in results and discussion sections as to facilitate the reader. I would have expected slightly greater discussion; more detail on the mechanisms and logical reasoning is required. There is much more scope here for discussing the implications of what the results means. Add suitable references throughout discussion section, where required.

 

 

Conclusion

15)  Novelty of this research work is again questionable with reference to practical significance and economic feasibility must be worked and mentioned. Kindly revise the conclusion subjected to conclusive findings only.

References

1)      A few very old references have been used. These must be updated with recent research findings or removed. Proper formatting is questionable. It must be according to MDPI SUSTAINABILITY Journal FORMAT. References formatting is inconsistent. Verify each reference from original source and cross check references in the text and reference section.

Comments on the Quality of English Language

The text has many typing and grammatical errors, capitalization issues. English style and language requires a profound revision. However, the readability of the manuscript needs to be improved, preferably carefully reviewing by a native English speaker. 

Author Response

Thank you for all your suggestions. According to your tips, we have rewrote many paragraphs through the whole manuscript, including adding statistical results in the Abstract, improving Abstract content as journal format, changing Key words, shortening Introduction and Discussion part, making references the same format as journal requirement and adding the latest references, English editing by MDPI, adding details for Materials and Methods, improving figures and tables, etc. At last, thanks again for your careful checking on my paper and your suggestions are very meaningful for improving our paper.

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

Although authors revised the manuscript, however, the experiment still has no replicates. I can not change my mind of rejecting the manuscript. 

Author Response

Thank you for your suggestion, so have supplement our pre-experiment data to this study. Before our formal field study, we have conducted twice of biochar incorporation to the soil on May and June to acquire a general change of soil and plant. So we add this part of data to compare with the present data derived from the biochar incorporation on July. Thanks again and hope our revised manuscipt can qualify your expects.

Sincerely

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

The authors have made major changes to the article, which is now more easily to read.

Author Response

Thanks again for your checking on my revised manuscript and also for your meaningful suggestion. Furthermore, my second round revision has been completed according to all the reviewers’ comments and please see the attachment. 

Author Response File: Author Response.pdf

Reviewer 4 Report

Comments and Suggestions for Authors

The text has many typing and grammatical errors, capitalization issues.  However, the readability of the manuscript needs to be improved.

Comments on the Quality of English Language

English style and language requires a profound revision.

Author Response

Thanks again for your checking on my revised manuscript and also for your meaningful suggestion. My second round revision of manuscript has been attached here, please see the attachment. Thank you!

Author Response File: Author Response.pdf