What Are the Variation Patterns of Vegetation and Its Influencing Factors in China from 2000–2020 from the Partition Perspective?
Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsI reviewed the manuscript entitled "What are the variation patterns of vegetation and its influencing factors in China from 2000-2020 from the partition perspective?" by Guo et al. The authors investigated the vegetation dynamic in China using NDVI and statistical methods. They also studied the factors that influenced the NDVI changes. In general, the manuscript is well-written, and the quality of the presentations is nice. The authors provided most of the necessary explanations. However, several points still need to be addressed to improve the quality of the manuscript.
1- The Introduction section requires a revision. The second paragraph only includes case studies related to vegetation trend analysis. While the current structure is accepted, the authors should mention the limitations of the previous studies in China to highlight the necessity of the current study. What were the limitations of previous studies that led you to conduct the current research? What are the contributions of this study to the field? These points should be justified and clearly stated in the Introduction section.
2- Line 119: What is the source of the NDVI dataset? Which satellite dataset was used to create the NDVI dataset?
3- Line 122: How many stations were used for the investigations? Please add their location in Figure 1.
4- Section 2.3.1: Please add further details on how to calculate the gravity center model, especially equation 1.
5- Line 177: Why linear regression was used for trend analysis? Why not use the Mann-Kendall and Sen's Slope? Moreover, previous research suggests that vegetation covers may exhibit non-linear trends (see https://doi.org/10.3390/rs11212475—https://doi.org/10.3390/rs14153683). Identifying non-linear trends can offer valuable insights for future assessments and conservation efforts. Please consider incorporating relevant discussions in the study's limitations or future directions.
6- Line 191: Please explain what "U is the sum of squares of regression" means.
7- Section 3.2.2: The current explanations are mostly related to the technical interpretation of the gravity center model; however, the reader may be more interested to read about the ecological interpretation of the gravity center model. Please add further explanations regarding the ecological interpretation of this statistical approach.
8- Section 3.3: Please add detailed information regarding the lag time computation. The current explanations are hard to follow.
9- Section 3.4.2: Please add a new figure representing the dominant influencing factor across China. Such a figure can give an excellent overview of the influencing factors in the spatial domain.
Comments on the Quality of English LanguageAlthough the manuscript is well-written with good English quality, there are several typos that should be corrected.
Author Response
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Author Response File: 
Author Response.pdf
Reviewer 2 Report
Comments and Suggestions for Authorsforests-3111172 “What are the variation patterns of vegetation and its influencing factors in China from 2000-2020 from the partition perspective? Bing Guo, Mei Xu, Rui Zhang, Wei Luo and Jicun Yang
This is a very thorough piece of work, examining many aspects of vegetation monitoring at the scale of the whole of China.
There are some naming issues with Equation 10. You indicate that y (subscript) “i” is NDVI of the first year which should be y (subscript) “1” as the second term in the equation. Also shown is y (superscript) “^” which is not in Equation 10 but is likely the first term.
Are the NDVI change slope values in Table 1 chosen arbitrarily or from some analysis of the data?
Equation 11 can be condensed by removing the entire middle section, i.e., q = 1 – SSW/SSW, and then continue with Equations 12 and 13 as written. The paper has not typeset the variables (sigma) “s”in the description of the equations.
Figure 2 uses the thick grey boundaries of Figure 1 for the outline of mainland China and all outlying islands, but this is too thick when presenting spatial images as the border obscures all the data on complex parts of the boundary. The inset islands on each figure show nothing but grey boundary and none of the vegetation colours, for example. Perhaps a single thing black line would be better for this style of figure; later in the paper also as the frames are now half sized. Further, as the whole of China is subdivided into 6 sub-regions for analysis, showing that set of boundaries rather than the political/provincial boundaries is preferred.
Your description of Figure 3 is limited and not well expressed. Simply repeating the R2 value and the slope of the lines is not useful; please describe the change as “value of vegetation in Northeast China increased by 0.0038 per year” on line 238 for example.
Discussing which regions had the highest and lowest rates of NDVI change is useful, or if the maximum annual increases (or decreases) all occur in similar years that indicates large scale phenomena, or if they are random which might indicate human influences. Regions 1, 5 and 6 have the highest R2 values which indicate they are consistent and smooth, while the other three are more variable (or volatile).
Area 3 (East China) is the most interesting as it has high NDVI but also large variation. Area 4 (Northwest China) is also of note as it has the desert regions but still has increasing NDVI over the last two decades. Only Region 2 (North China) does not have consistent decreasing NDVI during the last three years. Some of these interesting areas should be discussed more in the Discussion section.
Figure 6 is not putting its point across because the majority is simply staying the same, so it is just bright green. Without thinking about the visually impaired, a gradient system where all increases are one shade and all decreases are another with the no change being white or beige so it doesn’t interfere with showing the changing pixels. Same applies to Figure 9 for example, where the majority of the picture is bright green indicating no change. The reader primarily wants to see the areas that are changing.
The lags in Section 3.3 should be described as “1-3 months” without the “ago” added.
Figure 7 has too many things shown in single panels. You have symbol shape for vegetation cover, colour for lag time, a full gradient DEM underneath plus provincial and country boundaries. This needs to focus on the lag times and vegetation types with perhaps only six in each category, e.g., lump together grassland and meadow, keep all coniferous forest together, broad-leaf forests, etc. Try to simplify the presentation or use multiple panels to show each sub-region separately.
The wall of text that is page 19 is a single paragraph from line 474 to 534. It needs to be broken up into three or four pieces for ease of reading.
The text or caption for Figure 11 should indicate what the colour scheme is for the values shown. Are these equal intervals or values that are related to statistical significance?
In the end, the Discussion and Conclusions are just a summary of the relationships they have derived, rather than some insight as a result of those relationships, but it does fit with the intention of the Special Issue.
Comments on the Quality of English LanguageThe English expression was repetitive but OK and not hard to understand.
Author Response
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Author Response File: Author Response.pdf
Reviewer 3 Report
Comments and Suggestions for AuthorsIntroduction:
The presentation of the section is not clear to me, there were many unclear statements. Please see my queries in the attached document. I didn’t see a definite direction as to where the authors arguments were hinged. The study aim and objective(s) were not clearly stated, why this study? What is new that study brings to the table?
I can see you have consistently used comma (,) in place of full stop (.) all through the manuscript, please check and correct.
Overall, I suggest a total rewriting of this section for better clarity.
Materials and methods
The section was well written, but I would like you to do a more specific description of the study area. You centred your description more on the geographical locations of the study area. Kindly tell more about the vegetation which is the main point in this study.
Results
The results section was too wordy, there confusing the main message you were trying to convey. I will suggest you summarize your key findings by speaking succinctly to the figures and tables you presented.
Discussion
The discussion does not speak explicitly to the key findings of the study, it is quite shallow. I will suggest you do a comprehensive discussion telling us the implications of the results you got in the course of your study.
Comments for author File: Comments.pdf
Moderate grammatical corrections are needed.
Author Response
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Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
Comments and Suggestions for AuthorsI appreciate the authors' efforts in addressing the comments of the previous round. Most of the comments were addressed and implemented, and the quality of the manuscript has improved. However, two minor issues related to comments 5 and 9 remain.
First, please add further explanations regarding the usage of Mann-Kendall and non-linear trends with suitable justification, along with their advantages/limitations. The current explanations and hypotheses are not enough. Second, please apply changes to Figure 11 for better readability of the influencing parameters. The background can be modified so the influencing parameters will be more observable.
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
