Regulation of Methane Emissions in a Constructed Wetland by Water Table Changes
Round 1
Reviewer 1 Report
This paper regulated artificially the main controllable factors of the self-designed and constructed riparian wetland, namely hydrological conditions and additional carbon sources, and then measured methane fluxes. The results of this study may contribute to provide a theoretical basis for the management of the constructed and restored riverside wetland. However, there are some concerns that the authors should address before it can be considered for publication.
(1) The introduction is general and unspecific. The research progress and gaps of related study need to be further discussed.
(2) I suggest the authors add more references to back "Human activity not only changes wetland vegetation composition and hydrological conditions but also varies the soil permeability, oxidation reduction potential, and soil respiration rate, thus causing a certain amount of carbon loss (Zhang et al., 2019; Shen et al., 2020, 2021; Sui et al., 2021)"
(3) More mechanism explanations should be added to further explain the influence of driving factors on CH4-C.
(4) In order to further highlight the innovation of this article, it is better to compare the results of this study with more other studies.
(5) A paragraph of limitation discussion should be added to clarify the limitation or uncertainty of data and methods in this current study.
(6) The conclusion is not a simple restatement of the results. The authors should further clarify the contribution of the research results to the research field.
References:
Changes in wetland salinity, human activity and wetland vegetation abundances over the past 900 years. Global and Planetary Change, 2019, 182, 103000.
Marshland loss warms local land surface temperature in China. Geophysical research letters, 2020, 47, e2020GL087648.
Aboveground biomass and its spatial distribution pattern of herbaceous marsh vegetation in China. Science China Earth Sciences, 2021, 64, 1115-1125.
Soil physicochemical properties drive the variation in soil microbial communities along a forest successional series in a degraded wetland in northeastern China. Ecology and evolution, 2021, 11, 2194-2208.
Author Response
Dear Professor
First, I would like to thank you for the helpful comments provided for our paper. In the paper we’ve addressed all comments. Besides, we improved the novelty and importance of this study and rewrote the conclusion carefully. And we also checked the language, grammar, punctuation, spelling and overall style as well.
We provided an itemized reply to each of the reviewer‘s comments as follows：
(1) The introduction is general and unspecific. The research progress and gaps of related study need to be further discussed.
Answer: We have modified the introduction paragraph to present clear the aim of our research and the proposed objectives by adding such sentences in red.
(2) I suggest the authors add more references to back "Human activity not only changes wetland vegetation composition and hydrological conditions but also varies the soil permeability, oxidation reduction potential, and soil respiration rate, thus causing a certain amount of carbon loss (Zhang et al., 2019; Shen et al., 2020, 2021; Sui et al., 2021)"
Answer: We added more references in this part in red.
(3) More mechanism explanations should be added to further explain the influence of driving factors on CH4-C.
Answer: We added more mechanism explanations to further explain the influence of water level, moisture, and inundated time in red.
(4) In order to further highlight the innovation of this article, it is better to compare the results of this study with more other studies.
Answer: We added more other studies in the introduction part, and we rewrote the some parts to highlight the innovation of this article in red.
(5) A paragraph of limitation discussion should be added to clarify the limitation or uncertainty of data and methods in this current study.
Answer: We explained in more detail the use of the methodology.
(6) The conclusion is not a simple restatement of the results. The authors should further clarify the contribution of the research results to the research field.
Answer: We further clarified the contribution of the research results to the research field and rewrote the conclusion carefully.
Reviewer 2 Report
1- Line 30: leave a space between methane and to
2- Add a Schematic figure for the riparian wetlands indicating the gas flux measurement
3- Add a table that shows the Weather and properties of the area under study
4- Is there any other gas emissions from these CW (such as CO2 and nitrous oxide)
5- Specify the organic loading rates
Author Response
Dear Professor
First, I would like to thank you for the helpful comments provided for our paper. In the paper we’ve addressed all comments. Besides, we improved the novelty and importance of this study and rewrote the conclusion carefully. And we also checked the language, grammar, punctuation, spelling and overall style as well.
We provided an itemized reply to each of the reviewer’s comments as follows：
1 Line 30: leave a space between methane and to
Answer: We changed that.
2 Add a Schematic figure for the riparian wetlands indicating the gas flux measurement
Answer: We added a schematic figure for the riparian wetlands
3 Add a table that shows the Weather and properties of the area under study
Answer: We specified the weather and soil properties of the study area
4 Is there any other gas emissions from these CW (such as CO2 and nitrous oxide)
Answer: Yes, there are three main GHGs in the CWs, which are CH4, CO2, and N2O. And for the wetlands, CH4 contributes most to the atmosphere.
5 Specify the organic loading rates
Answer: We specified the organic loading rates in the paper.
Reviewer 3 Report
The manuscript describes the main factors that influence CH4-C flux. This study is helpful to guide the theoretical basis for the effective management of the constructed and restored riverside wetland. The authors provide an interesting and original study, the content is relevant to Sustainability. As it is, this paper is not fully acceptable for publication and requires some amendments and additional data or information.
The manuscript contains mental shortcuts that must be removed – e.g. line 250; CH4-C rebounded to 0.14±0.02 mg m-2 h-1 on the 238
32nd day, which differed from that of the -20 cm water table.
CH4-C emission/CH4-C flux? – please correct the entire manuscript
Why soil samples were collected only in August and October?
Why results about soil moisture and soil redox are presented in the discussion section?
Search the text for editorial errors - note the lack of spaces.
Lines 316-318;161-163;177-179;206-208;227-229;339-340 – respectively to what?
Fig. 1 and Fig.2 why is first -10 and then -20 on the x-axis?
Fig. 1 and Fig.2 Put the months in the correct order (don't start with August)
Fig. 3 and Fig. 4 – Why are the samples different colors?
Author Response
Dear Professor
First, I would like to thank you for the helpful comments provided for our paper. In the paper we’ve addressed all comments. Besides, we improved the novelty and importance of this study and rewrote the conclusion carefully. And we also checked the language, grammar, punctuation, spelling and overall style as well.
We provided an itemized reply to each of the reviewers' comments as follows：
- CH4-C emission/CH4-C flux? – please correct the entire manuscript
Answer: We checked the entire manuscript and corrected them.
- Why soil samples were collected only in August and October?
Answer: We thought that the physical and chemical properties of soil would not change in the short term, so we measured twice
- Why results about soil moisture and soil redox are presented in the discussion section?
Answer: Because Eh determined soil microbial and all kinds of soil enzyme activity and low Eh values could provide the necessary reduction conditions for methanogens. So we put that into discussion.
- Search the text for editorial errors - note the lack of spaces.
Answer: We changed that.
- Lines 316-318;161-163;177-179;206-208;227-229;339-340 – respectively to what?
Answer: We checked and changed that.
Fig. 1 and Fig.2 why is first -10 and then -20 on the x-axis?
Answer: We changed the x-axis.
Fig. 1 and Fig.2 Put the months in the correct order (don't start with August)
Answer: We corrected the order.
Fig. 3 and Fig. 4 – Why are the samples different colors?
Answer: We changed that.
Reviewer 4 Report
I have gone through the manuscript entitled " Regulation of methane fluxes in a constructed wetland by water table changes" and found it promising to accept. However, the following improvement/clearance need to be made before acceptance.
1. Line 81-82: soil classification should be given as per the soil classification.
2. A recently published article (https://doi.org/10.3390/w14060970) may help to improve the discussion of the present investigation.
3. Methane emission is subject to the change oxidative reduction potential. I suggest authors to discuss the output with inclusion of the ORP of the available primary/ secondary data.
4. Line 379-380: The statement "That flooded time is too long, which may also hinder the release of methane into the atmosphere and reduce methane emissions" is not clear. I suggest author to make it more clear and supportive investigation need to be cited.
5. Line 384-387 need to be checked, modified and supported by the relevant literature especially in case of the exponential increase in the water table only.
Author Response
Dear Professor First, I would like to thank you for the helpful comments provided for our paper. In the paper we’ve addressed all comments. Besides, we improved the novelty and importance of this study and rewrote the conclusion carefully. And we also checked the language, grammar, punctuation, spelling and overall style as well. We provided an itemized reply to each of the reviewers' comments as follows：
- Line 81-82: soil classification should be given as per the soil classification.
Answer: We specified the soil properties of the study area according to the soil classification
- A recently published article (https://doi.org/10.3390/w14060970) may help to improve the discussion of the present investigation.
Answer: Thank you for your help.
- Methane emission is subject to the change oxidative reduction potential. I suggest authors to discuss the output with inclusion of the ORP of the available primary/ secondary data.
Answer: We added some further discussion to this part.
- Line 379-380: The statement "That flooded time is too long, which may also hinder the release of methane into the atmosphere and reduce methane emissions" is not clear. I suggest author to make it more clear and supportive investigation need to be cited.
Answer: We added some further discussion to this part in red.
- Line 384-387 need to be checked, modified and supported by the relevant literature especially in case of the exponential increase in the water table only.
Answer: We added some further discussion to this part in red.
Round 2
Reviewer 1 Report
No further comments.
Author Response
We would like to thank you for the helpful comments provided for our paper.
Reviewer 2 Report
enhance the resolution of figures 2 and 3 (the typing on the axes is too small)
Author Response
We would like to thank you for the helpful comments provided for our paper. And we enhanced the resolution of figures 2 and 3. Thank you for your help again.
Reviewer 3 Report
The paper improved after the corrections and can be accepted for publication. Small language and form mistakes still could be found but can be corrected in the proof phase
Author Response
We would like to thank you for the helpful comments provided for our paper.
