Geographic Exploration of the Driving Forces of the NDVI Spatial Differentiation in the Upper Yellow River Basin from 2000 to 2020
Round 1
Reviewer 1 Report
Authors, this is an interesting paper using MODIS data to characterize landscape heterogeneity and change in regard to natural and human influences. I commend you for your interesting and effective research. This paper has potential to be an effective addition to research on satellite remote sensing and image analysis. The research is an interesting approach for using NDVI that utilizes what appear to be meaningful and useful approaches to data analysis and interpretation. I feel that the paper does have need for improvement. Please provide a clear objectives statement in the last paragraph of the introduction. Explain what the overall purpose of the paper is, and how this data will be used to address this question. You could include your hypotheses with this. I would encourage you to provide more explanation when defining terms and provide context to your research results in the discussion section. I provide specific examples of these in the detailed comments below. I would also encourage you to continue working on providing clear, concise, and grammatically correct sentences throughout the paper.
Here are specific detailed comments to consider:
Page 1, Line 14: modify the wording of this statement “To fill the gap of quantitative research on the driving forces of spatial distribution difference to the Normalized Difference Vegetation Index” to improve clarity. Its not clear what you are describing.
Page 1, Line 15: consider changing the wording from “To fill the gap of quantitative research on the driving forces of spatial distribution difference to the Normalized Difference Vegetation Index (NDVI) in UYRB recently, this study employs the NDVI to examine the temporal and spatial variation characteristics of vegetation growth in UYRB from 2000 to 2022.” to “To fill a quantitative research gap on the driving forces of the spatial distribution of vegetation in the UYRB, a normalized difference vegetation index (NDVI) was used to examine temporal and spatial variability between 2000 to 2022.”
Page 1, Line 19: you use a single NDVI value to describe an entire basin. It would be helpful to first explain how this NDVI was derived. Was this from a remotely sensed image? What type of sensor was used and what was the resolution. Its just not clear what the landscape is like that would allow for NDVI to be applied.
Page 1, Line 20: what do you mean by “The spatial vegetation coverage was significantly improved.”
Page 1, Line 21: be more specific with the description of the yellow river source area becoming deteriorated. I am not sure what you mean. The watershed is degraded? Plant communities are in bad condition?
Page 1, Line 27: how would you regulate precipitation? Also, what is the ecological project?
Page 1, Line 37: the sentence states that the use of remote sensing to monitor vegetation dynamics is a recent development. Remote sensing has been used extensive for this purpose for over 50 years. I would be more specific with this statement to provide a more accurate description.
Page 2, Line 45: MODIS has a spatial resolution of 250m (which you describe later). Compared to other satellite sensors (Landsat), this could be described as low resolution rather than high. Make sure you are clear with what you comparing MODIS with when you make this statement.
Page 2, Line 60: you should include a citation for this sentence which describes the interaction of human and natural factors.
Page 2, Line 70: I would rewrite this sentence as “There are only a few studies utilizing NDVI in UYRB.” You should probably include a reference to 2-3 of these since you make this point. It will allow the reader to know what these studies include.
Page 2, Line 74: can you be more specific with what you mean by “latest year”? What year are you referring to? The most recent year? Why is this significant?
Page 2, Line 75: Please insert a very clear objectives/purpose statement here. Provide a statement explaining why this research is being conducted prior to describing the methods. This paragraph currently starts by jumping right into the methods (using MODIS…).
Page 3, Line 101: I would love a brief description of the dominant vegetation and soils of this area. Maybe include several specific species that are most prevalent in this region.
Page 3, Figure 1: I like the color and layout of this map. Its nice. I do think it would be helpful to include an inset map showing where this study site is located in relation to Mongolia.
Page 3, Line 109: how did you determine these NDVI coverage grades? Did you just break them up into equal intervals because it created 5 even bins, or was it based on an ecological approach? If so, is there a reference or justification you can provide why these were chosen?
Page 4, Line 133: I like the description of the different layers used in this analysis. That was helpful. Table 1 is a little hard to understand (due to layout), but I eventually got it. I would consider separating the columns a little more so its clear that there are two columns of variables (9 per column). Also, the title caption “detection factor” is confusing and not informative. Write out what this table is about and what the information represents. Have this be a stand alone description of the table, and if you use the word “detection factor”, make sure its clear to the ready what you are talking about.
Page 4, Line 134-148: I am not sure how to make sense of this paragraph. It contains a number of categories and types, and how its presented is a little confusing. I would try to rewrite this paragraph so its clear what you are presenting and what those data represent.
Page 5, Line 166: you have somewhat done this, but I would encourage you to provide a very clear description of each detection type (factor detection, risk detection, interactive detection..). There are many terms being used and it would help to have a clear explanation of each. You could do the same for ecological exploration. Just make sure its easy for the reader to understand what you mean.
Page 5, Line 180: the same applies here regarding the table caption. You should provide a greater amount of detail describing the content of this table. What are the data and what do they represent?
Page 6, Line 205: I could probably be convinced that is isn’t critical, but it would be nice to see a paragraph describing the statistical analysis description of how you determined significance. You mention that you determined significant at an alpha of less than 0.05, but it would help to see this portrayed more clearly in the methods.
Page 6, Line 222: with the slope values in this table, you may want to include the percentage of each slope category so the reader understands its relevant importance.
Page 10, Line 309: this discussion section summarizes meaningful results and describes the interpretation of the analysis. This is good. It lacks in how it compares to other studies, and how is relates to other studies. It would be interesting to hear how these results are compared to the body of literature on temperature and precipitation influences on vegetation change and ecological dynamics of this area. I could see this applying well to your discussion on elevation change. Its an interesting subject, but not much context is given in the discussion.
Page 11, 361-365: these appear to be results and would be more suited to the results section. You could summarize their relevance here, particularly in relation to other studies,
Author Response
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Reviewer 2 Report
Comments for author File: 
Comments.pdf
Author Response
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Reviewer 3 Report
This work shows some interesting statistical analysis of changes in NDVI for a relatively long (20 ys) period of MODIS acquisitions on a specific area of the Yellow River basin. Those changes have been correlated against a series of impacting factors, including changes in raining and temperatures, showing a contextual increase of the vegetation index which seems geograpically stated and even empyrically sensed. While I would expect even some analysis of impacts from human activities (e.g. soil consumption), these results seem interesting per se. I would suggest usual grammar and spelling checks, too.
Author Response
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Round 2
Reviewer 1 Report
Thank you for responding to my original comments. I feel like the paper has improved and appreciate the attention to comments provided. It’s a well written and interesting paper and provides a meaningful contribution to remote sensing research. I have gone through the entire document again and have identified additional items that should be addressed. Hopefully these comments will continue to help improve this manuscript and bring it closer to being acceptable for publication.
Page 1, Line 13: I like how you set up the paper by describing the use of NDVI to detect vegetation distribution, however, this sounds more like a methods statement than an objectives statement. I don’t think that stating the use of NDVI to “examine temporal and spatial variability between 2000 to 2020” at the UYRB describes the purpose of this research. Consider stating something like “the purpose of this study was to evaluate remotely sensed imagery and vegetation indices as tools for accurately quantifying the driving forces of vegetation distribution. To accomplish this, we utilized NDVI to examine the temporal and spatial variability of vegetation distribution at the UYRB between 2000 and 2020.”
Page 1, Line 17: to be consistent with the surrounding sentences, I believe that you should replace “are” with “were” to state “…, and suitability of NDVI were detected.”
Page 2, Line 50: this is an important sentence, so I think it needs to be stated clearly. Be more specific with what you mean when you say that changes in phenological characteristics lead to changes in vegetation cover. How is cover influenced. Also, change “…changing the vegetation cover.” to just “changing vegetation cover.”
Page 2, Line 65: put a space between “other [20].”
Page 2, Line 67: This sentence is not clear. How about something like “This method effectively detects the consistency in spatial distribution patterns using dependent and independent variables by analyzing spatial heterogeneity.”
Page 2, Line 77: you need to finish this thought. Multi-year what?
Page 2, Line 79: this is the same issue as in the abstract (see above for Page 1, Line 13. I would not describe a method and study site as an objective of the research. State what this work accomplishes in addressing an important ecological question, and then state how it was done using NDVI in the YRB.
Page 11, Line 363: change wording to “… and developed in industry and agriculture, leading to lower vegetation cover.”
Author Response
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Reviewer 2 Report
The manuscript is sufficiently improved by addressing my concerns.
Best wishes,
Author Response
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