Research on Promoting Carbon Sequestration of Urban Green Space Distribution Characteristics and Planting Design Models in Xi’an

Round 1

Reviewer 1 Report

The paper is very interesting and useful, also well prepared (well constructed, methodically proper) and clearly written. 

The topic and contents of the paper are very current as regards cities planning adopting them to climate warming and as regards comfort of life in urban areas. It concerns, what the ability of plant cover/green areas for carbon sequestration depends on,  how to plan/create green areas to cause bigger carbon sequestration by vegetation cover and soil properties. VERY CURRENT TOPIC.

However, the subject, purpposes and results of reserarch are not very revealable (so I assessed the originality as medium one). Presented research results rather confirm previous research results (but sume aspects are partly new!) and/or are easily predictible, intuitively expected. Properties of plants / plant communities, including their ability to carbon sequestration, are widely known and confirmed. Nevertheless, presented reserarch results have provided the hard evidence, for example, as positive correlation between carbon sequestration ability and 1) land use types (vegetation cover types), 2) forest/green area size, 3) density and multi-layered structure of vegetation cover. The Authors also formultaed (on the base of their research results) some interesting guidelines, what species of plants to use and how to construct/plan green areas to make higher increase of carbon sequestration - useful for planners, landscape architects and decision-makers.

Detailed notes:

line 421 - probably there is the lack of the word "less" (...is 3 times less than...)

line 424 - Remove "Error! Bookmark..."

line 452: write in lower case: drought ( not Drought).

In general, I estimate the paper highly as very interesting and very important because of climate change being a result of many environmental demages caused by man. The paper is worth publishing.

 

 

 

Author Response

Please see the attachment

Author Response File: Author Response.docx

Reviewer 2 Report

Text interesting, here are my comments:

78. “In the urban environment, plant carbon sequestration are the main source of carbon

sequestration in urban green space, and also the main component of urban carbon sequestration.” – this sentence seems to repeat the content unnecessarily, I suggest removing it or replacing it with: In the urban environment, plant carbon sequestration is provided by different communities however mainly urban forests are analyzed with significant lack according greenery dispersed along roads and small green spots in settlements.

 229. According Figure 3, I can’t find visible relation to carbon sequestration as stated in caption. Figure gives only carbon emission data related to years. Sequestration depends on much more factors than amount of CO2 in the air.

 376. Community density is mainly positively related to carbon sequestration but we must notice dysymilation occurrence in shade and that is the reason of phenomenon described in 4.2.

 424. Error! Bookmark not defined

 To complete the suggestion for low-carbon green space planting design, it seems necessary to pay attention to natural succession and naturalization of green areas by nature itself. As mentioned in the text (420) consumption and maintenance of plantations cause carbon emissions, so the more artificial the environment with the dominance of ornamental species, the lower the summary efficiency of carbon sequestration. Nature should be allowed to develop freely in a part of the places, otherwise, despite good intentions, the implementation of our ideas will entail processes contrary to the goals of these ideas.

 449.” for the middle layer of large shrubs plants with higher branches and leaves”

 462-464. “In addition, shade-tolerant, flood-tolerant and drought-tolerant plants should be selected respectively to shade and moisture conditions, such as Oxalis corymbose and Miscanthus sinensis.”

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Reviewer 3 Report

The paper describes an interesting and complex study about the estimation of carbon sequestration of different urban green areas in Xi’an. Nevertheless, there are many aspects of concern. First of all, the introduction is redundant, with many paragraphs reporting the same concept, so I suggest making it more concise.

The methodology is confusing and only partially described. For instance, it does not clearly explain the process starting from the carbon sequestration mapping and its evaluation in different districts to the assessment of carbon sequestration by the plant communities in the specific green spaces. I wonder if the plant and soil carbon sequestration mapping is really needed in this paper.

The methodology for the estimation of the soil carbon sequestration is not explained, along with the remote sensing analysis.

In addition, there are missing details about the leaf gas exchange measurements (e.g., how many leaves have been used for the different types of vegetation, from which part of the canopy they have been selected, how many times in a year the same trees have been measured). The formula used for the estimation of the carbon sequestration seems to be based on the average of measurements taken in a day (authors state that the measurements were taken every two hours and along one year) but you don’t provide important information such as the number of days for each tree/species, number of trees and leaves measured and position within the canopy.

In order to compare different species carbon absorbance, how did you manage photosynthesis rates of different species varying upon the seasonal changes and ecological conditions?

Then, you assume the daily carbon sequestration based on the LAI and crown surface. Explain why and add a citation in the case this method has been used by other studies. The oxygen release is based on the “photosynthesis” reaction equation which is wrong and assuming that one molecule of O2 is released for one molecule of absorbed CO2, I do not understand why you used the photosynthesis rate for the estimation of O2 and since O2 is not mentioned in the results, I wonder why it should be mentioned in the methodology.

The results are not well structured, reporting part of the methodology and some results. More specifically:  - Lines 180-194 do not describe the results. This part should be shortened and included in the introduction.

-  Lines 199-202. The two sentences seem to be in contrast. On one side you have a decrease of woodland surface, and on the other side you write that the increase of carbon sequestration is related to the increase of woodland area.

-  Lines 202-228 This part concerning the description of Figure 3, seems to report about a different study and it is confusing.

-  Caption of Figure 3 does not report the carbon sequestration.

-  Line 234, now you mention “carbon sequestration of water, construction land and bare land” which is confusing. How did you estimate it? Maybe it’s a matter of terminology and you refer to all that is not agriculture or forest cover.

-  Line 239, again, underground carbon sequestration has not been mentioned in the methodology.

-  Caption of Figure 4 does not report carbon emissions, maybe you mean “carbon balance values”?

-  Chapter 3.3 should be moved to Materials and methods.

-  Chapter 3.3.2, Table 1 and Table 2, Table 3: Use international system units of measure (kg/km2 or kg/m2)

-  Table 3 should also include the number of individuals for each species.

-  Canopy density (line 319) and community density (line 331) are not described in materials and methods. It should be described.

-  Graphs in figure 6: move one parameter (Annual carbon sink or the other parameter) to the secondary Y axis. Then, uniform the terminology since the figure caption reports “canopy closure”.

The discussion is a mix of results and discussion. Move to results table 4 and relative description and delete table 5 if it does not bring additional information as compared to table 2.

Lines 437-439 Add a citation.

 

More detailed comments in the attached reviewed version.

Comments for author File: Comments.pdf

Author Response

Please see the attachment

Author Response File: Author Response.docx

Round 2

Reviewer 3 Report

I found the paper improved as compared to the previous version, however, there are still some descriptions of materials and methods that need further clarification, especially the formulas used for the calculation of the carbon sequestration. See detailed suggestions and comments in the pdf attached.

Comments for author File: Comments.pdf

Author Response

Dear Reviewer,

We are very grateful to you for your time and effort reviewing the manuscript. Your professional suggestions make our articles better. All our revisions to articles are marked with the "track changes" feature. In the uploaded file, we respond to your suggestion one by one. In the article, the content of this modification is as follows:

-Firstly, we performed extensive English-language revisions of the manuscript and enlisted a native English-speaking colleague to check and correct grammatical errors in the article.

-Secondly, according to the reviewer's request, we supplemented the detailed information of the research in Materials and Methods: the type of instrument used in the survey, the detailed estimation process of carbon sinks, the symbol errors in the formulas, and the references that are not relevant to this study were deleted.

- Finally, we have reworked the Abstract, Introduction and Conclusion sections to express clear ideas in more concise language.

 

Thank you again for your valuable comments, which are very important and instructive for our future research, and we hope we can learn more from you!

 

Author Response File: Author Response.pdf