Spatial and Temporal Change Characteristics and Climatic Drivers of Vegetation Productivity and Greenness during the 2001–2020 Growing Seasons on the Qinghai–Tibet Plateau
Round 1
Reviewer 1 Report
Comments and Suggestions for Authors
Some questions:
1. This study considers all regions of the plateau, but some areas of the Qinghai-Tibet Plateau are devoid of vegetation or have sparse vegetation. Analyzing the spatiotemporal dynamic trends and driving forces in these areas may not be meaningful. It is recommended to use an annual average NDVI value less than 0.1 as a mask to exclude these areas.
2. What exactly is the lagged NDVI in Figure 6? It is not explained in detail in the methodology.
3. In Figure 8, it would be more intuitive if the legend was divided into three levels: Hurst < 0.5; Hurst = 0.5; Hurst > 0.5.
4. Is it reasonable to judge the future trend of NDVI solely based on the Hurst value? After all, the changes in vegetation NDVI are mainly influenced by climatic factors, but the calculation of the Hurst index does not include climatic factors. Additionally, this study finds that most areas of the Qinghai-Tibet Plateau exhibit a trend of decreasing NDVI in the future. Is this consistent with existing research?
Some other minor issues:
1. The MODIS NDVI data product has been available since 2000. Why does this study not start from 2000?
2. There are some minor reference errors in the article, such as L180, L190, L194, L203. Please revise the entire text.
Author Response
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Author Response File: 
Author Response.pdf
Reviewer 2 Report
Comments and Suggestions for AuthorsThe topic is quite interesting, however the manuscript is not prepared well in a few aspects, so it is not acceptable for a scientific publication.
First, English writing need substantial improvements, which includes grammar, terminology, as well as editing of text and citations. Many citations lost the link to references in the list!
Second, the component using the Hurst Index to predict future trends, and the integration with trend analysis to investigate changes in the past and trends in future, seems not to be convincing and needs more justification.
Introduction of the Moran's I and the Hurst index needs to be more in depth. Description on how these two indicators are actually calculated or the tools used for calculation, and their interpretation principles to link with physical environmental properties and phenomenon, should be more clear. These are more important than simply providing their equations, as likely people will use a tool rather than the given equations directly in their studies.
Both discussion and conclusion are repeat of results, lacking analysis of results with respect to understanding of physical principles, interpretations and inferences in the Discussion section, and summarization and abstraction in the Conclusion section.
A few specific comments:
1) Title: could replace NDVI with a physical term, like vegetation productivity and greenness.
2) lines 22-23" what is a geographic range of NDVI?
3) lines 24-25: Modify; what does it mean when the Hurst index is about 0.44 and "sustainability"?
4) Line 39: modify "Vegetation naturally integrates soil, water and atmosphere", it reads not correct; Line 41 "vegetation ecosystems" is not a proper term
5) Lines 54-55: meaning unclear. Please revise
6) Lines 73-74: There is a logical issue here:
Q-T Plateau is vulnerable to climate change means it is impacted by climate change, but this is not equal to state that, it has a larger feedback to climate change.
7) Lines 82-84 and 93: not sure if future trends can be studies with confidence using the data and analysis method presented in the manuscript; It might work with projected climate data and establish prediction models
8) Line 115: could you show "Forest" in the map?
9) Lines 145-146: revise. I don't think it is averaged over multiple years. Annual growing season average temperature is conventional, but precipitation is also averaged, or should it be summed?
10) Line 162: j ranges from 5 to 10!
11) Line 171: what does this mean "create a curve"?
12) Line 237: Modify "during the multi-year growing season"
13) Figure 2: given the vast spatial extent, the meaning of the trend of average NDVI over the whole plateau is not clear. It is better to put it together with the trends per vegetation classes in Figure 4
14) Line 263 and this manuscript: replace "stability" with "stable"
15) Line 360: please be more specific about the low-low and high-high
16) Table 2 Column-1 is miss-aligned with rows
17) Line 494: should not be linked to urbanization and human disturbance, as vegetation types are quite different
Comments on the Quality of English Language
English needs substantial improvement.
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Reviewer 3 Report
Comments and Suggestions for AuthorsI reviewed the ms. "Spatial and Temporal Change Characteristics and Climatic Drivers of NDVI During the 2001-2020 Growing Seasons on the Qinghai-Tibet Plateau.". Overall, the paper makes a valuable contribution to the understanding of vegetation dynamics on the Qinghai-Tibet Plateau and provides a solid foundation for future research in this area. he paper addresses a significant research gap, uses robust analytical methods, and provides valuable insights into the spatiotemporal dynamics of NDVI and their climatic drivers. I have minor suggestions:
- The title accurately reflects the content of the paper and includes the key variables (NDVI, spatial and temporal changes, climatic drivers) and the study region (Qinghai-Tibet Plateau).
- The abstract provides a concise summary of the study, including the objectives, methods, key findings, and implications. It is well-structured but could benefit from a brief mention of the significance of the study's findings in the context of existing literature. Take care with keywords. Provide different words from the title.
- The introduction clearly establishes the importance of studying NDVI in the Qinghai-Tibet Plateau in the context of climate change. It effectively highlights the ecological significance of the region and the need for understanding vegetation dynamics.
- The literature review is comprehensive, referencing key studies that have investigated NDVI trends and their climatic drivers. However, it could be strengthened by including more recent studies to ensure the research is up-to-date.
- The objectives are clearly stated, and the research questions are well-defined.
The methodology section could be more detailed to ensure reproducibility, and the discussion could be expanded to include more in-depth comparisons with recent literature and detailed recommendations for future research. The use of Theil-Sen trend analysis, Mann-Kendall significance testing, spatial autocorrelation analysis, and Hurst index calculation is appropriate for analyzing spatiotemporal changes and trends. However, the explanation of these methods could be more detailed to ensure reproducibility. Pearson correlation analysis is suitable for investigating the relationship between NDVI and climatic factors. The formulas and statistical tests used are appropriate, but the justification for choosing these specific methods could be elaborated.
Results and discussion: The interpretation of the results is generally sound. However, more in-depth discussion on the significance of the Hurst index findings and their implications for future vegetation trends would be beneficial. Suggestions for future research are provided, which is valuable for advancing the field. However, specific recommendations for addressing the identified limitations could be more detailed.
Overall Figures: PLease, check the letter size in the figures. It´s imposible read Figure 3, for example.
Author Response
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Author Response File: Author Response.pdf
