Spatial and Temporal Dynamics of Ecological Parameters in Various Land Use Types in China during the First 20 Years of the 21st Century

Round 1

Reviewer 1 Report

In this study (land-2959787), the authors investigated the spatio-temporal variation of some key ecological indicators, including NDVI, EVI, LAI, GPP and NPP, in different land use types, to reveal the relationship between these ecological indicators and land use. In my opinion, the manuscript is suitable for publication in the journal LAND after a major revision.

1.        The title “ecological indicators” does not accurately reflect the main content of this study. The authors used NDVI, EVI, LAI, GPP, and NPP to characterize vegetation growth. Therefore, it would be more appropriate to use the term “vegetation growth” instead of “ecological indicators”. If the authors follow this recommendation, they should modify most of the manuscript, including the aim, introduction, main findings, discussion, and conclusion.

2.        The language used in this study is unclear and difficult to understand. For example, the meaning of phrases such as “Based on the interaction among multiple spheres” (page 1, line 34) and “Ecological indicators change whether to consider LUTs” (page 10, line 267) is not clear.

3.        Several studies have investigated the effects of land use and land cover change (LUCC) on vegetation growth. The authors should aim to provide a clear and concise review of the relevant studies, using precise subject-specific vocabulary where appropriate.

4.        The MCD12Q1 product classifies land cover types. It is important to note that land cover and land use types do not have a one-to-one correspondence. However, the authors did not provide a method for deriving land use types from land cover types.

5.        The authors did not provide sufficient details on the specific methods used for resampling the land cover data, which can be done in various ways, each yielding different results.

6.        The current discussion is also about getting results, not discussing getting results.

7.        The text in the figures is significantly smaller than the main body, and some of it is illegible, such as Figure 6.

I believe the manuscript requires a major revision for the reasons stated above.

 Extensive editing of English language required.

Author Response

In this study (land-2959787), the authors investigated the spatio-temporal variation of some key ecological indicators, including NDVI, EVI, LAI, GPP and NPP, in different land use types, to reveal the relationship between these ecological indicators and land use. In my opinion, the manuscript is suitable for publication in the journal LAND after a major revision.

1. The title “ecological indicators” does not accurately reflect the main content of this study. The authors used NDVI, EVI, LAI, GPP, and NPP to characterize vegetation growth. Therefore, it would be more appropriate to use the term “vegetation growth” instead of “ecological indicators”. If the authors follow this recommendation, they should modify most of the manuscript, including the aim, introduction, main findings, discussion, and conclusion.

Response:

Thanks to the reviewer for your comments. The text explains that parameters like NDVI/EVI/LAI/GPP/NPP are commonly utilized to indicate vegetation growth and processes. However, the focus of the paper is on land use types rather than vegetation types. Therefore, the author believes it is more suitable to refer to these parameters as "ecological indicators" rather than "vegetation growth." In response to feedback from reviewers and the original article's purpose, the author modified it into “ecological parameters” in the revision draft.

2. The language used in this study is unclear and difficult to understand. For example, the meaning of phrases such as “Based on the interaction among multiple spheres” (page 1, line 34) and “Ecological indicators change whether to consider LUTs” (page 10, line 267) is not clear.

Response:

Thanks to the reviewers for your comments. The specified sentences have been revised in the updated draft, with the author making significant corrections and enhancements to the entire article.

3. Several studies have investigated the effects of land use and land cover change (LUCC) on vegetation growth. The authors should aim to provide a clear and concise review of the relevant studies, using precise subject-specific vocabulary where appropriate.

Response:

Thanks to the reviewers for your comments. Upon reviewing pertinent literature, few articles were found that specifically address the influence of land use and land cover change (LULC) on vegetation growth. While the discussed article primarily focuses on changes in Leaf Area Index (LAI) across various vegetation types, it does not delve into the effects of LULC on ecological parameters. Furthermore, the publication from 2023 highlighted the scarcity of studies examining alterations in ecological parameters of vegetation types.

Preference:

Ma, Y.Y.; Wang, W.Y.; Jin, S.K.; Li, H.X.; Liu, B.M.; Gong, W.; Fan, R.N.; Li, H. Spatiotemporal variation of LAI in different vegetation types and its response to climate change in China from 2001 to 2020. Ecol. Indic., 2023, 156, 111101. https://doi.org/10.1016/j.ecolind.2023.111101.

It is important to highlight that the ecological parameters discussed in the paper primarily pertain to their annual variations. The study explored the mean values and differences in variation of ecological parameters among different land use types, as well as the repercussions of LULC on these ecological parameters. This aspect was elaborated upon in the third section of the discussion and served as an innovative aspect of the article. The author has made appropriate adjustments to the specific terminology used in the article.

4. The MCD12Q1 product classifies land cover types. It is important to note that land cover and land use types do not have a one-to-one correspondence. However, the authors did not provide a method for deriving land use types from land cover types.

Response:

Thanks to the reviewers for your comments. In this study, the IGBP classification system derived from MCD12Q1 data is utilized to categorize the global land surface into 17 distinct classes, as illustrated in Figure 2.

The outcome of this classification process involves the consolidation of these 17 categories into 6 groups, which aligns with a more scholarly classification framework commonly employed in China. For further details on the specific types within these categories, readers are directed to the works and datasets provided by Liu's research team. It is asserted that there is general consensus with the reviewers regarding the classification of cultivated land, construction land, and unutilized land in the research paper. However, some deliberation is warranted on the classification of forest land, grassland, and water bodies. The rationale behind the classification decision is elucidated herein. It is worthwhile that categories 1-7 in the original data are unequivocally designated as forest land without contention. Conversely, categories 8 and 9, characterized by a prevalence in southern China with higher precipitation levels and predominantly shrub vegetation, are deemed more akin to woodland rather than grassland, as observed in African savannas. Furthermore, in line with Liu’s team's classification system, permanent wetlands, glaciers, snow, and water bodies are grouped together based on their shared underlying surface characteristics. The revised manuscript includes references to the pertinent classification systems and their practical applications for the reviewers' consideration.

5. The authors did not provide sufficient details on the specific methods used for resampling the land cover data, which can be done in various ways, each yielding different results.

Response:

Thanks to the reviewers for your comments. It is important to highlight that the author refrained from resampling the land use data, opting instead to reclassify it based on the original source data. This distinction underscores the differing processes and outcomes between the two approaches. In response to concerns regarding the reclassification methodology, the author has provided pertinent explanations in the fourth section of the document.

6. The current discussion is also about getting results, not discussing getting results.

Response:

Thanks to the reviewers for your comments. The discussion section of this research is structured into three main chapters, focusing on the inter-monthly variation of ecological parameters, the differing responses to climate change, and potential avenues for future research. A significant revision made to the original document pertains to the examination of monthly variations in ecological parameters. Initially, the author aimed to ascertain whether these parameters could be utilized to differentiate between various land use types based on known distinctions in ecological characteristics. However, feedback from a previous reviewer highlighted the lack of a sound rationale and a comprehensive methodological framework, leading to a revision that emphasized the inter-monthly changes in ecological parameters instead.

The discussion segment serves as an elaboration of the paper's analytical findings, drawing upon existing literature to enhance and refine the research outcomes. By addressing the limitations of prior studies, this section effectively supplements and advances the current understanding of the subject matter. Furthermore, the future research prospects acknowledge the shortcomings of the present study, with a call for continued enhancements in subsequent research endeavors.

7. The text in the figures is significantly smaller than the main body, and some of it is illegible, such as Figure 6.

Response:

Thanks to the reviewers for your comments. The font size of the map has been adjusted in the updated version, and further information can be found in the manuscript.

I believe the manuscript requires a major revision for the reasons stated above.

Author Response File: Author Response.pdf

Reviewer 2 Report

Brief summary:

The authors delve into the changes of ecological indicators in China from 2001 to 2020, while considering the influence of various land use types on these indicators. The consistency of the Data and Methods sections and the relevance of the Results are noteworthy. Addressing the issues surrounding land use types and their effects on ecological assessments is pivotal, especially in the face of environmental degradation in China.

General concept comments:

The manuscript is well-written, and its topics are highly relevant in the context of climate change. The description of the methodology and the results is satisfactory.

Specific comments:

In my opinion, a few adjustments are necessary.

Line 31: Rewrite as land-use and land-cover change (LULC).

Line 45: Please consider better describing the issues of vegetation determination in the context of LULC change initiatives.

Line 59-62: Please rewrite this consideration, as the NDVI also captures information from soil.

Line 129: The captions for Figure 1 are hard to read. Figure 3 also needs improvement. Same for Figure 6.

Line 524: Overall, the Conclusion section also requires improvement.

English very difficult to understand/incomprehensible.

Author Response

Brief summary:

The authors delve into the changes of ecological indicators in China from 2001 to 2020, while considering the influence of various land use types on these indicators. The consistency of the Data and Methods sections and the relevance of the Results are noteworthy. Addressing the issues surrounding land use types and their effects on ecological assessments is pivotal, especially in the face of environmental degradation in China.

General concept comments:

The manuscript is well-written, and its topics are highly relevant in the context of climate change. The description of the methodology and the results is satisfactory.

Specific comments:

In my opinion, a few adjustments are necessary.

Line 31: Rewrite as land-use and land-cover change (LULC).

Response:

Thanks to the reviewers for your comments. The pertinent information has been altered in the updated version of the document. For further information, please consult the manuscript.

Line 45: Please consider better describing the issues of vegetation determination in the context of LULC change initiatives.

Response:

Thanks to the reviewers for your comments. The pertinent information has been altered in the updated version of the document. For further information, please consult the manuscript.

Line 59-62: Please rewrite this consideration, as the NDVI also captures information from soil.

Response:

Thanks to the reviewers for your comments. The determination of vegetation cover involves the utilization of the NDVI. A particular approach involves focusing solely on values falling within the 5% to 95% range, while assigning values below 5% and above 95% directly to 0% and 100%, respectively. It is acknowledged that this methodology may lead to distortion in the values of certain areas. Consequently, adjustments have been made to the expression method in the manuscript to address these potential issues.

Line 129: The captions for Figure 1 are hard to read. Figure 3 also needs improvement. Same for Figure 6.

Response:

Thanks to the reviewers for your comments. The modified and simplified version of Figure 1/3/6 in the document can be found in the revised draft for further examination.

Line 524: Overall, the Conclusion section also requires improvement.

Response:

Thanks to the reviewers for your comments. The modified version of Conclusion in the document can be found in the revised draft for further examination.

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

I accept this manuscript published in present form.