Sediment CO2 Flux from a Mangrove in Southern China: Is It Controlled by Spatiotemporal, Biotic or Physical Factors?
, Fen Guo 2, Zhifeng Yang 1,2 and Shing Yip Lee 4Round 1
Reviewer 1 Report
The manuscript entitled: “Sediment CO2 flux from a mangrove in Southern China: is it 2 controlled by spatio-temporal, biotic or physical factors?”
Studies on the dynamics of carbon in mangroves need to consider carbon gas flux, but the mechanisms that influence it are not always well understood. In this work, it is proposed that a number of factors regulate sediment carbon dioxide (CO2) fluxes in a natural mangrove in Southern China.
The manuscript is relevant for the field and presented in a well-structured manner, however there are several inputs that could improve the manuscript.
1. The introduction is needed to be strengthening. Mangroves are one of the forests with the highest carbon stores in the tropics and this is an interesting area to be elaborated. In addition Mangrove carbon stocks experience dynamics along with the growth in diameter, changes in mangrove area and density both naturally and by anthropogenic pressure. This too needs to be included in the introduction.
2. In the method “The invasion of cordgrass Spartina alterniflora has resulted in rapid encroachment of the intertidal mudflat seaward 84 to the mangroves, effectively suppressing mangrove expansion into the accreting coast ...” This is also an interesting fact that needed to be elaborated in the introduction as well or in the site description. As invasion by Invasive Species (Exotic or native) is important in affecting the mangrove ecosystem.
3. Please also provide list of the mangrove species in the study site and as well as other species and indicates which is native, non native
4. Please explain the reason and references to chose to test for season, tidal, light and species as the factors in your research design.
5. Among the dominant species that were chosen in the study does all species have similar DBH or height or similar age? This might also an interesting factor to be included.
6. If you could provide a spatial version of your results it would be more interesting. Modify the research site map with inputs from your results providing a nice info graphic style.
7. Please do not over use of self-citations. There are 6 self citations from the author detected.
In addition, several of the references used are older than 5 years; please provide references within the last 5 years.
Author Response
Thank the reviewers for further comments on our ms. The ms has been improved based on the reviewers’ comments. A revised version with tracked changes has been uploaded online and changes have been marked by coloured fonts. In the following responses, please be noted that the line numbers are numbers in the mode without tracking changes in the ms.
Recommended edits by reviewer 1:
The introduction is needed to be strengthening. Mangroves are one of the forests with the highest carbon stores in the tropics and this is an interesting area to be elaborated. In addition Mangrove carbon stocks experience dynamics along with the growth in diameter, changes in mangrove area and density both naturally and by anthropogenic pressure. This too needs to be included in the introduction.
Response: In the revised version, we have clarified that mangroves are among the most C rich forests in the tropics and discussed the dynamics of changes in mangrove C stocks. (l.34-5).
In the method “The invasion of cordgrass Spartina alterniflora has resulted in rapid encroachment of the intertidal mudflat seaward 84 to the mangroves, effectively suppressing mangrove expansion into the accreting coast ...” This is also an interesting fact that needed to be elaborated in the introduction as well or in the site description. As invasion by Invasive Species (Exotic or native) is important in affecting the mangrove ecosystem.
Response: The invasion of Spartina alterniflora into the mangrove has been further described in the Materials and Methods section (l.91-5).
Please also provide list of the mangrove species in the study site and as well as other species and indicates which is native, non native
Response: A table has been added in the revised version to give a list of the mangrove and saltmarsh species in the study site (Table 1).
Please explain the reason and references to chose to test for season, tidal, light and species as the factors in your research design.
Response: These factors have been shown to affect CO2 fluxes in previous studies but they have not been investigated together. This point has been added in the revised version (l. 112-3).
Among the dominant species that were chosen in the study does all species have similar DBH or height or similar age? This might also an interesting factor to be included.
Response: No, the species have different traits. Canopy height has been included as a factor in the revised version (l. 149-50, Figure 3).
If you could provide a spatial version of your results it would be more interesting. Modify the research site map with inputs from your results providing a nice info graphic style.
Response: A spatial map of CO2 fluxes for the study site has been added in the revised version (l. 230-2, Figure 4).
Please do not over use of self-citations. There are 6 self citations from the author detected.
Response: Some self-cited references have been deleted (l.37 and 56).
In addition, several of the references used are older than 5 years; please provide references within the last 5 years.
Response: Agreed and done (ref. 21, 26, 31 and 34).
Reviewer 2 Report
Title: Interesting
Abstract: CO2 flux was highest in Avicennia marina in comparison with Aegiceras corniculatum and Kandelia obovata.- please add synonym name before the scientific name, for readers to be more likely to understand
Add the importance on studying carbon in mangrove in the last sentences
Keywords: add more appropriate keywords in the article
Introduction: The introductio have the connection between paragraph, but lack of the importance of the study area. At the materials and methods, the authors shared the current situtation about the study area, but lack of reason on why the study should be conducted at the Southern China? Please add it in the introduction section
Methods: please share how big the author's sampling areas?
"Mangroves in the estuary are dominated by Avicennia marina, Kandelia obovata and Aegiceras corniculatum." - please add common name
Lack of references in the methods, please add more references for the methods section
Results: acceptable
Discussion: Please add more references for the author's discussion
Conclusion: accepatable
Conflict of interest: Please add if any
Author Response
Thank the reviewers for further comments on our ms. The ms has been improved based on the reviewers’ comments. A revised version with tracked changes has been uploaded online and changes have been marked by coloured fonts. In the following responses, please be noted that the line numbers are numbers in the mode without tracking changes in the ms.
Recommended edits by reviewer 2:
Abstract: CO2 flux was highest in Avicennia marina in comparison with Aegiceras corniculatum and Kandelia obovata. please add synonym name before the scientific name, for readers to be more likely to understand
Response: Synonym names have been added to the species names (l.22-23, Table 1).
Add the importance on studying carbon in mangrove in the last sentences
Response: Agreed and done (l.28-29).
Keywords: add more appropriate keywords in the article
Response: Agreed and done (l.30).
Introduction: The introduction have the connection between paragraph, but lack of the importance of the study area. At the materials and methods, the authors shared the current situation about the study area, but lack of reason on why the study should be conducted at the Southern China? Please add it in the introduction section
Response: We have justified why the study was done in Southern China in the revised version (l.76-7).
Methods: please share how big the author's sampling areas?
Response: The size of the sampling area has been described in the revised version (l.118-9).
"Mangroves in the estuary are dominated by Avicennia marina, Kandelia obovata and Aegiceras corniculatum." - please add common name
Response: Agreed and done (l.90-1).
Lack of references in the methods, please add more references for the methods section
Response: We have added more reference in the Material and Methods sections (l.21 and 150).
Discussion: Please add more references for the author's discussion
Response: Agreed and done (l.11-3 and 24-6).
Reviewer 3 Report
CO2 flux measurement was conducted in a natural mangrove in Southern China, aiming to examine the relationship between CO2 flux and a variety of variables, including seasons, tidal positions, species, sediment temperature, crab burrow and pneumatophore densities, and to identify the main factors resulting in the variation of sediment CO2 flux. My comments about the paper:
1- Figure 1 is of very low quality and does not meet the standards of this journal. I suggest making another figure, using suitable software for geolocation, such as ArcGis, R statístic, among others.
2- There is no adequate description of the methodological procedures. There is no detailed description of the measuring instruments, and there is not even an equation cited to demonstrate how the results shown were arrived at.
3- Figure 2 is extremely inadequate from a statistical point of view. I suggest that you do a principal component analysis (PCA) to better understand the contributions to flux variability.
4- The results do not address the climatic characteristics of the location, nor do they show the time series of the measured data. The climatology of the site and an annual boxplot of the CO2 data series must be presented.
5- Most references in the paper are old, 10 years or older. I suggest adding more recent references on the subject.
Author Response
Thank the reviewers for further comments on our ms. The ms has been improved based on the reviewers’ comments. A revised version with tracked changes has been uploaded online and changes have been marked by coloured fonts. In the following responses, please be noted that the line numbers are numbers in the mode without tracking changes in the ms.
Recommended edits by reviewer 3:
Figure 1 is of very low quality and does not meet the standards of this journal. I suggest making another figure, using suitable software for geolocation, such as ArcGis, R statístic, among others.
Response: Figure 1 has been replaced and geographic information has been shown in the revised version.
There is no adequate description of the methodological procedures. There is no detailed description of the measuring instruments, and there is not even an equation cited to demonstrate how the results shown were arrived at.
Response: We have added more details on how the flux was calculated in the revised version (l.137-44).
Figure 2 is extremely inadequate from a statistical point of view. I suggest that you do a principal component analysis (PCA) to better understand the contributions to flux variability.
Response: We have added the principal component analysis in the revised version (l.192-6, Fig. 3).
The results do not address the climatic characteristics of the location, nor do they show the time series of the measured data. The climatology of the site and an annual boxplot of the CO2 data series must be presented.
Response: Sediment CO2 fluxes were generally measured during a short incubation period (~2.5min) to avoid pressure built-up in the chamber. It is difficult to provide the time series data. This is also the case for similar studies cited in our study (e.g. Leopold et al. 2013 and Chen et al. 2012). We have shown the seasonal variation in CO2 fluxes over the mangrove nature reserve in the revised version (Figure 5).
Most references in the paper are old, 10 years or older. I suggest adding more recent references on the subject.
Response: We have removed some old references and added recent references (ref. 21, 26, 31 and 34).
Round 2
Reviewer 2 Report
The manuscript are now can be accepted since the improvement have been made
Reviewer 3 Report
Dear,
Significant changes have been made to the manuscript, I believe it is now in an acceptable standard for publication.
