Soil Quality Assessment and Influencing Factors of Different Land Use Types in Red Bed Desertification Regions: A Case Study of Nanxiong, China

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

General Comment

It is good to know about your study on “Soil Quality Assessment and Influencing Factors of Different 2 Land Use Types in Red Beds Desertification Regions: A Case 3 Study of Nanxiong, China”. The flow and readability are good. However, there are some major corrections to be made. Below are some specific comments.

Specific Comment:

1.      Pg. 1, lines 28-30; “Regarding comprehensive soil quality indicators across various land use types, soils affected by red bed erosion and bare rock exhibited the lowest quality, with forest land unexpectedly showing lower quality as well.” It is difficult to know which is lower than the other. Therefore, I suggest you paraphrase this sentence. Let your results be clearly explained in descending order.

2.      Keyword: Humid region. Do you mean red bed desertification areas? If yes, I suggest you change “humid region” to “red bed desertification areas”. It is important for you to be consistent with the words you use in your manuscript to avoid confusion.

3.      Pg. 15, line 513; Change “rregion” to “region”

4.      In your study, chemical methods were used for evaluating soil quality. It would be a good idea to do some more literature review and include the recent technological development and why you chose to use the chemical method.

5.      It is good to know about the different soil types. However, you need to include the following information to your manuscript:

·         The soil’s bulk density and porosity.

·         How well the different soil types retain and infiltrate water.

·         Are there any contaminants or excessive salts present?

· For the land areas you considered in your study, are

 

 any soil amendments or fertilizers being applied and why?

6.      What is the major difference between your findings, and the findings of other researchers?

7.      I suggest you include a feasible recommendation in your manuscript for future consideration.

 

Overall, you need to do a major revision to your manuscript. I suggest you explicitly state the originality and significant impact of your study.

Comments on the Quality of English Language

The quality of the English is good.

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Reviewer 2 Report

Comments and Suggestions for Authors

Dear authors,

Your publication is highly significant as it emphasizes the importance of soil quality in red rock desertification regions for sustainable development and preserving ecosystem functions in these areas.

The methodology used is clearly described and is based on statistical reliability. A Principal Component Analysis (PCA) method was employed to create a minimum dataset (MDS) for calculating the Soil Quality Index (SQI). I appreciate the comprehensive coverage of the six different types of land use in the Nanxiong Basin, Guangdong Province.

The study relies on chemical indicators, classic indicators of soil quality. This is a well-known concept. Organic matter in the soil, pH, available phosphorus, exchangeable calcium, and available copper are significant factors affecting soil quality. The study indicates that the lowest soil quality is observed in the areas affected by erosion of red rocks and bare rocks.

My critical remarks are related to improving the material about the abbreviations of soil quality indicators used. For chemical elements, I recommend using their ionic forms – Ca²⁺, Mg²⁺, Cu²⁺, Zn²⁺, etc., because, in several chemical abbreviations, EC is a popular name for exchange capacity, not for exchange calcium. Exchange forms of phosphorus are usually also written with the formula P₂O₅ and K₂O – an estimate of the supply of available potassium. 

The only physical indicator is also better given as W% because it is more popular than the abbreviation, regardless of how it is described. You indicate that soil organic matter has been determined. Usually, the described chemical method of acid decomposition with a bichromate scheme considers the organic carbon in the soil, and soil organic matter is obtained by a coefficient calculation method. 

I suggest you cite each soil indicator from primary sources in the Methods section. Additionally, any publication focusing on soil as the subject of study should specify the soil types or use a soil classification from a national or World Reference Base for Soil Resources.

In my assessment, the study is not a novelty regarding methodology or choice of indicators. However, it is crucial to manage soil risk for people in this region for sustainable agriculture and for preventing their ecological functions.

Recommendation: I accept the article for publication after editing.

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Reviewer 3 Report

Comments and Suggestions for Authors

Soil Quality Assessment and Influencing Factors of Different Land Use Types in Red Beds

 

Introduction

Line 48:  105 should be 10⁵;  

Line75:  I like the MDS approach when working with soils.

Lines 79-80: Do these lines conflict with the statement in lines 45-46?

Line 94: delete “,” after (SQI)

The study has detailed objectives listed.

Material and Methods

Line 103: I would change “Higher” to “Greater” for easier reading.

Section 2.2

· If soil quality is the goal, why sample soil to only 10 cm depth. It does not even include the plow layer on the ag sites?

· If you have 3 samples per sampling plot and 87 plots, the sample number would be 261; but the text says 291. A misprint?

· What is the distribution of samples among the land use types?

· What is the justification for choosing the soil characteristics from among all the possibilities?

· Why measure SM when (i) it is a one-time measurement that can change rapidly; (ii) rain does not necessarily fall evenly daily throughout the area?

· Why was no textural data (i.e %clay) included. Given the origin of the bedrock in these areas, would one not expect that to be different between areas?

Line 144:  AHN is not mentioned in lines 132-134

Lines 205-209: What criteria were used to define the three groups. Was it vegetation growth. If so, it appears that  vegetation growth was not a measurement taken?

Results

3.1

Line 224: Eroded land has the highest SOM yet no plant growth? Does that make any sense?

Table 3. There is no real title for this table.

Figure 2. I do not see the reason for using different size balls and strength of color. The actual correlation coefficients would be much more useful and interpretable. One could highlight the number with color, but the actual number would be best.

??: I understand the use of PCA here. It is groups variables together that explain the maximum variance in the population while reducing the number of variables. But if this is to be used to explain soil quality as per the soils ability to function, how is this determining that? PCA does not define any outcome or predictor variables. It only works with the variance of predictors.

Line 286-7: These lines indicate that the SQI was computed based on the MDS and the relationship to soil characteristics and soil functions. Yet, I do not see any soil functions as part of this research. Soil functions include things like production, habitat, source of raw materials, cultural heritage, etc. Is it the authors idea that the soil function in this case is the ability to support vegetation? If so, that is a worthy function. Would not the data set need to include the amount and or type of vegetation to define the classes? Sorry, but I am confused about how the MDS can turn into a SQI unless there is a function or functions that relate to the SQI. Please help me understand.

Figure 3: The title does not explain the boxes and lines and dots.

Line 301:  How are soil quality index classes defined as to the ability of the soil to function? That seems to be missing in the methods. Given the classes, it appears to be support of vegetation? Yet there is no vegetation data per plot. How can forest soils have more area considered to have severe limitations to vegetation growth than eroded land which is defined by the lack of vegetation? How can REL have class II if it defined as not supporting vegetation?

Figure 4: This figure has print so small that it is unreadable at the scale it is presented. It also does not explain the difference between (a) and (b).

Discussion

Lines 347-348: Again, this says the MDS was suitable for evaluating soil quality, yet no dependent variable has been identified to help identify soil function to which the MDS can be related. Would it be more accurate to say that the MDS was most suitable to describing the soil population and its variability?

Lines 462:  I do not understand how planting the woodland area to acacias and pine are a reason for this group to have the most percentage of site III, and have a greater  percentage of III than REL. The pH of WL is 6.8, which is about as good as you could ask for, therefore the explanation given in this section does not seem to coincide with the data of the sites. By the way, the +/- values in Table 3 are not described as to whether they are CI or SD.

Conclusion

Line 504: The authors note that their data showed that most of the sites were of medium quality. Again, I do not understand how medium quality was defined.

 

To summarize, I appreciate the amount of work that the authors undertook. I appreciate and very much like the definition of a MDS and can see how PCA does a good job of reducing the variables. What I do not understand is how this is related to soil function, hence site quality. If the function is ability to support vegetation, then I would think vegetation data would be necessary. If it is not vegetation, then I am confused on how the three classes were defined. Also, some of the results are confusing. WL soils having a higher percentage of Class III than REL as noted above. It appears that the authors have a manuscript that is an example of how to define a MDS. It also appears that using MDS to determine a SQI is very confusing, and I wonder if it is even possible for all the reasons given above. I would like to see the authors address each of the comments above with particular emphasis on the SQI and soil function.

Comments on the Quality of English Language

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Author Response

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Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

Dear Authors,

You have done a comprehensive revision to your manuscript.

This significant revision has added to the quality of your paper.

Your hard work is impressive.

 

Author Response

Thank you for your professional advice, which has greatly enhanced the quality of our article. We also appreciate your positive feedback on our work and wish you all the best.

Reviewer 3 Report

Comments and Suggestions for Authors

Thank you for your responses to this review. Many of your responses were right on and understandable. However, I still have some things that I think would make your paper stronger.

Response 8:  This is somewhat confusing. Are you saying that your results are now confounded by newly implemented restoration work where organic material has been added to the red bed erosion land? That the land with no vegetation has more organic C than those with vegetation now makes sense, but what does that mean to your analysis? Is it not compromised and provides less useful information? Does not your grouping make less sense now based on soil chemistry features? It is a issue that should be directly addressed in the methods/results/discussion.

Response 17:  I question your response here given the above. If the REL data was influenced by initial restoration work, would this not be the reason that REL has less area in III that woodland? This should be addressed in the manuscript.

Summary

I think I now understand your work better. The one thing that I believe needs to be addressed which was not addressed in the methods is the relevant history of the REL plots. Since some (or all?) had newly implemented restoration work that included organic materials, the authors should provide this information in the site description so the audience has all necessary information.  Since vegetation is a crucial descriptor in this work, I would also want to see the limited information and survey of vegetation at least mentioned in the methods.

 

Author Response

Please see the attachment.

Author Response File: Author Response.docx