Mapping Abandoned Cropland Changes in the Hilly and Gully Region of the Loess Plateau in China
Round 1
Reviewer 1 Report
Thank you very much for this opportunity to review this excellent manuscript. With the development of social economy, the abandonment of cultivated land has become a common social and economic phenomenon all over the world. If the land is abandoned too much, it will pose a threat to the country's food security. In this context, GIS/RS and other technical means were used to analyze the time-sequence map of land abandonment in Gaolan County hilly area of the Loess Plateau. In general, this is a meaningful work. The research design is clear, the method is feasible, and the conclusion is basically in line with the objective reality. It is suggested to publish after minor revision, with specific comments as follows:
(1) The marginal contribution of research needs to be further clarified. For example, the uniqueness of the methods/data used in this study compared to previous studies needs to be further pointed out. The present manuscript does not show where the core marginal contribution is.
(2) The conceptual definition of research needs to be further clarified. The abandonment of cultivated land is the core variable of the research. In fact, there are different standards for the definition of the abandonment of cultivated land. For example, there are seasonal abandoned, perennial abandoned. It is suggested that the author further discuss this area, because the setting of standards will affect the subsequent research results.
(3) The conclusions are too succinct. The research ideas/framework of this study are suggested to further illustrate the implications of mapping the abandoned farmland in China and other hilly areas of the world.
Author Response
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Author Response File: 
Author Response.docx
Reviewer 2 Report
In the manuscript, the authors presented the assessment results of land abandonment using remote sensing data. The authors used Landsat data from 2011. The work is well structured; the introduction gives basic information about the problem of land abandonment. However, the outlined objectives need to be corrected. "propose", "use kernel density methods" cannot be objective. They are, at best, research tasks. Finding relationships, risk assessment, etc., can be considered as a goal. Overall, the work done raises minimal questions in the methodology section in terms of the methods used.
The main questions are: How did the authors distinguish abandoned land from grassland? How did they estimate the areas occupied by perennial plants for hayfields? How did they consider crop rotation? How did they filter virgin land? Three years is too short; the authors need to be more responsible for choosing a period. It is recommended to use the criterion of appearance of tree and shrub vegetation on a particular field. Based on this, abandoned areas should include areas that are not used (this is the main criterion for assigning to abandoned or not abandoned land) for 10-15 years. Accordingly, the authors need to increase the time interval of the experiment.
The authors used the Landsat TOA product. How did the authors calibrate it to Surface Reflectance?
The authors do not analyze the results at all. What are the reasons for the abandonment? What is the abandoning related to? Slopes? Soil type? Fertility?
Figure 1 - Gaolan County is not visible on the map; enlarge it. The position of the study area relative to other states is also not clear.
The text needs serious rewriting of the English.
The manuscript is recommended for revision.
Author Response
Please see the attachment.
Author Response File: Author Response.docx
Round 2
Reviewer 2 Report
The manuscript looks more complete after the revision. I recommend that the authors rename Chapter 4 to "Results and Discussion" and Chapter 5 to "Conclusions.
