Soil Physicochemical Properties and Fertility Evolution of Permanent Gully during Ecological Restoration in Granite Hilly Region of South China

Round 1

Reviewer 1 Report

General Comments

This an interesting and useful work. However, the work needs revision not so for wrong data or conclusions but mainly for clarifications. Sometimes the reader finds it difficult to understand what the authors mean.

Specific Comments

1. Page 1, lines 38-39. Change to : “Permanent gullies are defined as deep channels that cannot be ameliorated by normal tillage operations. They are landforms created ….gravity”.

2. Page 2, line 42. Delete “erosion”, it is repeated twice.

3. Page 2, lines 57-60. It is not clear what you mean. You speak about feldspars and quartz but here we have to deal with soils not parent material.

4. Page 2, line 68. Explain what Benggang is. Is it an area?

5. Page 2, lines 79-80. Change to: “Few studies have addressed soil fertility change caused in the process..China”.,

6. Page 3, line 114. Is the vegetation coverage different with comparison the other two areas?

7. Page 3, lines 121-122. Change to: “At each site the litter was removed and sampling points were selected along an S shaped line”.

8. Page 3, line 123. Describe in a more elaborate way how you mixed soil samples. How many samples did you have in total?

9. Page 3, line 124. Change to:”was air dried..”

10. Page 3. Lines 126-128. Delete all acronyms for the soil properties. You will use the later.

11. Page 4, 139. Describe the method you measured available N. Is there any reference?

12. Page 4, lines 140-141. Change to: “Available phosphorus (Olsen) was extracted with NaHCO₃ (pH 8.5) and measured in a U/V spectrophotometer”. Describe the method you used to develop the color.

13. Page 4, lines 143-144. Describe the method you used to determine the value of CEC.

14. Can you give a reason you determined only K and not Ca and Mg?

15. Page 4, line 146. Delete “consolidation” and use “calculation” instead.

16. Page 4, line 147. Delete “data mapping”

17. Page 4. Paragraph 3.1. For all the physical and chemical properties, give definitions of the acronyms.

18. In the results section describe briefly the results of the ANOVA.

19. In Figure 2, describe (in the text) what the legends (UC, DL, WT etc) are.

20. In Figure 2, the x-axis has the legends UC, WT and WM. What do they mean?

21. In Figure 4, the lowest part of the graph is not needed.

22. Figures 5 and 8 are very small. You have to magnify them.

23. The meaning of the capital and small letters are described only for figure 2. Does this thing stand for the other figures as well?

24. Page 8, lines 249-251. Do you want to say that pH values do not differ significantly?

25. Page 8, lines 265-269. Correct the English language.

26. Paragraph 3.4. The interpretation of PCA is completely incomprehensible. You have to take into account that soil scientists and the general readers are not statisticians. Make it much shorter and explain what are the factors affecting soil fertility. Also, explain what more the PCA can offer with regard to the Pearson correlation coefficients in this work.

27. In the Discussion section, you should not use acronyms but only the real names of the soil properties.

28. Page 16. Lines 446-450. What do the numbers 1.28, 0.33 and 0.95 mean and how were derived? Is there any index of fertility? If yes how did you calculate it?

29. Page 16, line 449. Have you done any measurements on biological activity and biodiversity? If not you should not mention them

Author Response

Response to reviewer #1:

General comments:

Reviewer #1: This an interesting and useful work. However, the work needs revision not so for wrong data or conclusions but mainly for clarifications. Sometimes the reader finds it difficult to understand what the authors mean.

Reply: Thank you for your affirmation and support for our research work. We have conscientiously revised the manuscript according to your suggestions and comments. As for grammatical errors and some chapters that appear difficult to understand in the revised manuscript we have carefully revised the text to make it better.

Comment 1: Page 1, lines 38-39. Change to: “Permanent gullies are defined as deep channels that cannot be ameliorated by normal tillage operations. They are landforms created...gravity”.

Reply: Thank you very much for your comments and suggestions. “Permanent gullies are defined that channels deep cannot be ameliorated by normal tillage operations, which are landforms created ... gravity” in the revised manuscript has been changed to “Permanent gullies are defined as deep channels that cannot be ameliorated by normal tillage operations. They are landforms created ….gravity” in the revised manuscript.

Comment 2: Page 2, line 42. Delete “erosion”, it is repeated twice.

Reply: Thank you for your suggestion. The word erosion on page 2, line 142 in the revised manuscript has been deleted.

Comment 3: Page 2, lines 57-60. It is not clear what you mean. You speak about feldspars and quartz but here we have to deal with soils not parent material.

Reply: The subject of the article discusses the changes in soil physicochemical properties of granitic soils during ecological and vegetation restoration, rather than the soil parent material. Therefore, the granite weathering crust, which is mainly composed of feldspar and quartz, does not fit the article topic and has been deleted in the revised manuscript.

Comment 4: Page 2, line 68. Explain what Benggang is. Is it an area?

Reply: “Benggang” is a Chinese word, meaning “a collapsing hill”. Now, many researchers named this erosional phenomenon “Benggang”. A Benggang gully, in which a steep collapsing wall forms in the revised mountain slope surface under the influence of water and gravity, is a particular type of permanent gully that is widespread in South China [1-3]. A Benggang gully consists of five parts: the upper catchment, collapsing wall, colluvial deposit, scour channel and alluvial fan [4-6]. Such landforms are mainly distributed in Hubei, Hunan, Jiangxi, Fujian, Guangdong, Guangxi and Anhui provinces [7-8]. Also, we added sketch of Benggang erosion in the granite hills of South China in the revised manuscript (Figure 1).

Figure 1. Sketch of Benggang erosion in the granite hills of South China.

1. Xu, J.X. Benggang erosion: the influencing factors. Catena. 1996, 27, 249-263, doi:10.1016/0341-8162(96)00014-8.
2. Jiang, F.S.; Huang, Y.H.; Wang, M.K.; Lin, J.S.; Zhao, G.; Ge, H.L. Effects of Rainfall Intensity and Slope Gradient on Steep Colluvial Deposit Erosion in Southeast China. Soil Sci Soc Am J. 2014. 78,1741-1752, doi:10.2136/sssaj2014.04.0132.
3. Chen, J.L.; Zhou, M.; Lin, J.S.; Jiang, F.S.; Huang, B.F.; Xu, T.T.; Wang, M.K.; Ge, H.L.; Huang, Y.H. Comparison of soil physicochemical properties and mineralogical compositions between noncollapsible soils and collapsed gullies. Geofis Int. 2018, 317, 56-66, doi:10.1016/j.geoderma.2017.12.006.
4. Sheng, J.A.; Liao, A.Z. Erosion control in south China. Catena. 1997, 29, 211-221, doi:10.1016/S0341-8162(96)00057-4.
5. Xia, D.; Deng, Y.S.; Wang, S.L.;Ding, S.W.; Cai, C.F. Fractal features of soil particle-size distribution of different weathering profifiles of the collapsing gullies in the hilly granitic region, South China. Nat Hazards. 2015, 79, 455-478, doi:10.1007/s11069-015-1852-1.
6. Deng, Y.S.; Cai, C.F.; Xia D, Ding, S.W.; Chen, J.Z.; Wang, T.W. Soil atterberg limits of different weathering profiles of the collapsing gullies in the hilly granitic region of southern China. Solid Earth. 2017, 8, 499-513, doi:10.5194/se-8-499-2017.
7. Zhong, B.L.; Peng, S.Y.; Zhang, Q.; Mac, H.; Cao, S.X. Using an ecological economics approach to support the restoration of collapsing gullies in southern China. Land Use Policy. 2013, 32, 119-124, doi:10.1016/j.landusepol.2012.10.005.
8. Deng, Y.S.; Shen, X.; Xia, D.; Cai, C.F.; Ding, S.W.; Wang, T.W. Soil Erodibility and Physicochemical Properties of Collapsing Gully Alluvial Fans in Southern China. Pedosphere. 2019, 29, 104-115, doi: org/10.1016/S1002-0160(15)60105-9.

Comment 5: Page 2, lines 79-80. Change to: “Few studies have addressed soil fertility change caused in the process...China”.

Reply: We appreciated your suggestion. “few studies have addressed on soil fertility change caused by soil nutrient in the process... China.” in the revised manuscript has been changed to “few studies have addressed soil fertility change caused in the process... China”.

Comment 6: Page 3, line 114. Is the vegetation coverage different with comparison the other two areas?

Reply: The active Benggang areas (AG), which have bare soils and sparse vegetation, were mainly dominated by ferns such as Dicranopteris dichotoma. In the semi-stable Benggang areas (MG), vegetation was dominated by Pinus massoniana and a small amount of undergrowth vegetation, such as Dicranopteris dichotoma and Miscanthus floridulus, and in the stable Benggang areas (SG), the vegetation coverage increased significantly.

Comment 7: Page 3, lines 121-122. Change to: “At each site the litter was removed and sampling points were selected along an S shaped line”.

Reply: Thank you very much for your comments. “At each site, first removed the litter, and carried out multi-point sampling according to the "S-shaped" strategy.” in the revised manuscript has been changed to “ At each site the litter was removed and sampling points were selected along an S shaped line”.

Comment 8: Describe in a more elaborate way how you mixed soil samples. How many samples did you have in total?

Reply: Combining the morphological distribution and spatial sampling points of the Benggang areas, soil samples were collected along the upper catchment, collapsing wall, colluvial deposit, scour channel and alluvial fan in the sample plots representing different stages of Benggang restoration. Each collapsing wall was divided into top, middle and lower sections for sampling, each colluvial deposit was divided into top and lower sections for sampling and each alluvial fan was divided into top, middle and edge sections for sampling. At each site the litter was removed and sampling points were selected along an S shaped line. The soils from multiple soil profiles at the same sampling point and the same depth layer were mixed into one soil sample, with a total of 30 soil samples.

Comment 9: Page 3, line 124. Change to: “was air dried...”.

Reply: Thanks for your suggestion. We have changed “well air-dried” in the revised manuscript changed to “was air dried”.

Comment 10: Page 3. Lines 126-128. Delete all acronyms for the soil properties. You will use the later.

Reply: Thank you for your positive comments on our research work! We have deleted all acronyms for the soil properties in lines 128 to 126 in the revised manuscript.

Comment 11: Page 4, Lines 139. Describe the method you measured available N. Is there any reference?

Reply: The alkaline permanganate oxidation method was determined Available nitrogen (AN).

Subbiah, B.V.; Asija, G.L. A rapid procedure for the determination of available nitrogen in soils. Curr Sci. 1956, 25, 259–260.

Comment 12: Page 4, lines 140-141. Change to: “Available phosphorus (Olsen) was extracted with NaHCO3 (pH 8.5) and measured in a U/V spectrophotometer”. Describe the method you used to develop the color.

Reply: We have changed “Olsen’s method was used for colorimetric determination of the content of available phosphorus (AP) in 0.5 mol NaHCO3 (pH 8.5)” in the revised manuscript changed to “The Olsen’s method was used for colorimetric determination of the content of available phosphorus (AP) in 0.5 mol NaHCO3 (pH 8.5)”.

Horta, M.D.C.; Torrent, J. The Olsen Pmethod as an agronomic and environmental test for predicting phosphate release from acid soils. Nutr Cycl Agroecosys. 2007, 77, 283-292, 16. doi:10.1007/s10705-006-9066-2.

Comment 13: Page 4, lines 143-144. Describe the method you used to determine the value of CEC.

Reply: Cation exchange capacity (CEC) was determined by ammonium acetate extraction buffered at pH 7.

Rhoades, J.D. Cation exchange capacity. In Page A L, Miller R H, Keeney D R (eds.) Methods of Soil Analysis. Part 2. America Society of Agronomy, Madison. 1982, pp, 149-157.

Comment 14: Can you give a reason you determined only K and not Ca and Mg?

Reply: During the investigation of sample plots, we made a preliminary experiment on the soil with granite parent material, and the experimental results showed that the content of calcium and magnesium in the soil was relatively low. Therefore, other nutrients may better respond to soil quality.

Comment 15: Page 4, line 146. Delete “consolidation” and use “calculation” instead.

Reply: Thank you very much for your comments. We have deleted "consolidation" in the revised manuscript and replaced it with "calculation".

Comment 16: Page 4, line 147. Delete “data mapping”.

Reply: Thank you very much for your comments. We have deleted “data mapping” in the revised manuscript.

Comment 17: Page 4. Paragraph 3.1. For all the physical and chemical properties, give definitions of the acronyms.

Reply: As showed in Table 1 (Statistical characteristic values of soil physical and chemical properties in the study area). The definitions of all the physical and chemical properties of the soils mentioned in paragraph 3.1 are indicated below. Soil physical and chemical properties all acronyms are defined as follows: GR: Gravel content; SA: Sand content; CL: Clay content; SI: Silt content; FWC: Field water capacity; SWC: Saturated water content; SHC: Saturated hydraulic conductivity; BD: Bulk density; STP: Soil total porosity; CP: Capillary porosity; NCP: Aeration porosity; SOM: Soil organic matter; CEC: Cation exchange capacity; TN: Total nitrogen; TP: Total phosphorus; TK: Total potassium; AN: Available nitrogen; AP: Available phosphorus; AK: Available potassium.

Comment 18: In the results section describe briefly the results of the ANOVA.

Reply: Thank you very much for your suggestions. In the revised manuscript, we did an ANOVA with a brief description of the soil physicochemical properties in different stages of Benggang restoration. For example, soil bulk density and pH were not significant differences in different stages of Benggang restoration; The difference analysis results showed that the TN contents in the different stages of Benggang restoration were significant difference. Total phosphorous (TP) and TK content in the stable stages of Benggang restoration were significant increased. Meanwhile, the TN, TP and TK among different locations in the different stages of Benggang restoration had significant differences and presented the following order: upper catchment > alluvial fan > scour channel > colluvial deposit > collapsing wall, indicating that the soil fertility was the highest in the upper catchment and poor on the colluvial deposit. The AN, AP and AK during different stages of Benggang restoration were obviously different and showed sta-ble stage > semi-stable stage > active stage.

Comment 19: In Figure 2, describe (in the text) what the legends (UC, DL, WT etc) are.

Reply: In this Figure, we have annotated each acronym of in the revised manuscript. The all acronyms are annotated as follows. AG: Active stage of Benggang; MG: Semi-stable stage of Benggang; SG: Stable stage of Benggang. UC: upper catchment; WT, WM, WL: the top, middle and lower of collapsing wall; DT, DL: the top and lower of colluvial deposit; SC: scour channel; AT, AM, AE: the top, middle and edge of alluvial fan.

Comment 20: In Figure 2, the x-axis has the legends UC, WT and WM. What do they mean?

Reply: The problems with the acronym in this Figure have been corrected in our revised manuscript. Also, the definition of each acronym in this Figure is explained in the response to comment 19.

Comment 21: In Figure 4, the lowest part of the graph is not needed.

Reply: Thank you for your suggestion. The lowest part of the graph represent the different stage of Benggang restoration component units in this Figure. And the different colors on the bar graph of each component unit indicate the soil particle size distribution. This graph is not exactly the same as the others, and its horizontal coordinates can better reflect the meaning of the indicators. To improve the clarity of the soil particle size distribution graph, we also plotted the soil particle size distribution graph again.

Comment 22: Figures 5 and 8 are very small. You have to magnify them.

Reply: Thank you very much for your valuable comment. We have revised the manuscript for issues such as inconsistent proportions of the figure.

Comment 23: The meaning of the capital and small letters are described only for figure 2. Does this thing stand for the other figures as well?

Reply: Yes. The meanings of the capital letters, lowercase letters, and acronyms in Figure 2 also represent the meanings of the capital letters, lowercase letters, and acronyms in the rest of the figure.

Comment 24: Page 8, lines 249-251. Do you want to say that pH values do not differ significantly?

Reply: Yes, We have explained it. “All soils were acidic and the pH values were no obvious vary in different stages of Benggang restoration” in the revised manuscript has been changed to “All soils were acidic, and the pH values did not vary in an obvious pattern in different stages of Benggang restoration”.

Comment 25: Page 8, lines 265-269. Correct the English language.

Reply: Thanks for your suggestion. We have corrected the English grammar and expression mistakes you pointed out in the revised manuscript.

Comment 26: Paragraph 3.4. The interpretation of PCA is completely incomprehensible. You have to take into account that soil scientists and the general readers are not statisticians. Make it much shorter and explain what are the factors affecting soil fertility. Also, explain what more the PCA can offer with regard to the Pearson correlation coefficients in this work.

Reply: Thank you for your affirmation and support for our research work. We have conscientiously revised the manuscript according to your suggestions and comments. The content of paragraph 3.4 has been modified accordingly. The steps of principal component analysis were also adjusted to make it easier for the reader to understand. From in Table 3, the main influencing factors were field water capacity, capillary porosity (CP), sand, clay, pH, organic matter (OM), cation exchange capacity (CEC), total nitrogen (TN), total phosphorous (TP), total potassium (TK), available nitrogen (AN), available phosphorus (AP) and available potassium (AK) for the first principal component and had the greatest influence on soil fertility. From the correlation analysis of each soil fertility parameter at different stages of Benggang restoration in Figure 11, it is clear that the evaluation of soil physical and chemical properties and fertility at different stages of Benggang restoration by only one soil parameter or the correlation analysis of a soil parameter with other factors often yields one-sided research results and cannot scientifically evaluate soil fertility at different stages of Benggang restoration. Therefore, in this study, PCA was performed on 20 soil parameters to evaluate soil fertility levels at different stages of Benggang restoration.

Comment 27: In the Discussion section, you should not use acronyms but only the real names of the soil properties.

Reply: Thank you very much for your comments and suggestions. The soil all acronyms used in the discussion section have been changed to the real names of the soil properties.

Comment 28: Page 16. Lines 446-450. What do the numbers 1.28, 0.33 and 0.95 mean and how were derived? Is there any index of fertility? If yes how did you calculate it?

Reply: PCA was applied to comprehensively evaluate the soil fertility at different stages of Benggang restoration. IBM SPSS Statistics 19.0 standardized the raw data for the 20 soil parameters involved in this study to ensure the objectivity and scientificity of the PCA results, while the 20 standardized soil parameters were recorded as ZSHC, ZBD, ZSTP, ZCP, ZNCP, ZSWC, ZGravel, ZSand, ZClay, ZSilt, ZFWC, ZpH, ZOM, ZCEC, ZTN, ZTP, ZTK, ZAN, ZAP, and ZAK. PCA was performed on the standardized data to derive the eigenvalues with variance contribution (Table 3) and the number of principal components (Table 3). Meanwhile, the loadings of each soil parameter corresponding to each of the three principal components were divided by the corresponding eigenvalues of the principal components (Table 2, λ₁=11.252, λ₂=3.689, and λ₃=12.281) to obtain the square root and the eigenvectors of eachparameter corresponding to each of the three principal components. Therefore, according to the formulas for calculating the principal components, the functional expressions of the first three principal components can be obtained. The specific expressions are given in equations (1), (2) and (3) in the revised manuscript. Finally, the composite of each principal component score and the product of its corresponding contribution was calculated, and the expression is shown in equation (4) in the revised manuscript. The results are shown in Table 4.

Finally, thank you again for your careful and detailed revision of this manuscript.

Author Response File: Author Response.pdf

Reviewer 2 Report

Detailed edits are attached. 

General comments: An important analysis of soil fertility and physical properties along in gullies. Introduction could be improved with photos and or diagram of gully components, and explanation of how restoration is occurring (naturally or human efforts). Methods are sufficiently detailed. Results need improvement. Figures are very hard to read without sufficient legends to interpret and text is often illegible in y-axis. Discussion is good. Any idea how long the process of stabilization takes? How long have the gullies that are stable had to build up the observed fertility? Also is it possible that areas of higher fertility were more resistant to degradation, or is it obvious from shape that they were once as degraded as the others?  Literature cited is extensive and relevant. I made small edits in the attached document to improve the clarity and grammar, and pointed out areas that were confusing to me. Thank you for the opportunity to contribute my review to this paper and I look forward to seeing the revisions. 

Comments for author File: Comments.pdf

Author Response

Response to reviewer #2:

General comments:

Reviewer #2: An important analysis of soil fertility and physical properties along in gullies. Introduction could be improved with photos and or diagram of gully components, and explanation of how restoration is occurring (naturally or human efforts). Methods are sufficiently detailed. Results need improvement. Figures are very hard to read without sufficient legends to interpret and text is often illegible in y-axis. Discussion is good. Any idea how long the process of stabilization takes? How long have the gullies that are stable had to build up the observed fertility? Also is it possible that areas of higher fertility were more resistant to degradation, or is it obvious from shape that they were once as degraded as the others?  Literature cited is extensive and relevant. I made small edits in the attached document to improve the clarity and grammar, and pointed out areas that were confusing to me. Thank you for the opportunity to contribute my review to this paper and I look forward to seeing the revisions.

Reply: We appreciated your comments and suggestion. We believe that the additional changes we have made in the revised manuscript have made this a significantly stronger manuscript. Meanwhile, we have added a sketch map of Granite Erosion in Benggang hills of southern China, and the crumbling post recovery is mainly a state of natural recovery. And make certain modifications to the relevant graphics in the revised draft. Below is our point-by-point response to your comments. It generally takes 15-20 years for the Benggang to recover and stabilize. In its shape, it is easy to identify because it still lets retain the appearance of the Benggang in its shape, but the vegetation restores very well and the organic matter content is significantly higher than that of the active stage of Benggang restoration.

Comment 1: Title is quite long.

Reply: The revised title has been changed to: “Soil Physicochemical properties and fertility evolution of permanent gully during Ecological Restoration in granite Hilly Region of South China” in the revised manuscript.

Comment 2: Page 1, lines 12-13. Change to: "A special type of permanent gully, called "Benggang" severly affects agricultural production in hilly areas". Is this limited to China, or found in other areas?

Reply: Thank you for your valuable comments on our research work! “As a special permanent gully, Benggang has severely affected the agricultural production in hilly areas.” in the revised manuscript has been changed to "A special type of permanent gully, called "Benggang" severly affects agricultural production in hilly areas". In the granite areas of tropical and subtropical South China, there is a widely distributed erosional phenomenon and the associated small scale erosional landform, called “Benggang” by the local people. “Benggang” is a Chinese word, meaning “a collapsing hill”. Similar landscapes are found in other countries. Now, many researchers named this erosional phenomenon “collapsing gully”. Gullies erosion not only occur in marly badlands and mountainous or hilly regions but also more globally in soils subjected to soil crusting such as loess (European belt, Chinese Loess Plateau, North America) and sandy soils (Sahelian zone, north-east Thailand) or in soils prone to piping and tunneling such as dispersive soils.

Comment 3: Page 1, lines 15. “correspoding” change to “corresponding”.

Reply: “correspoding” has been changed to “corresponding” in the revised manuscript.

Comment 4: Page 1, lines 34. what is a heat resource? Does this mean a suitable climate for agriculture?

Reply: Thank you very much for your comments and suggestions. We have replaced in the revised manuscript “The red soil region, which has abundant water and heat resources...” replaced with “The red soil region, which has abundant water resources and high temperatures...”.

Comment 5: Page 1, lines 35. Changed to “growing gap between food supply and population growth”.

Reply: Thank you very much for your comments and suggestions. “growing conflict between food and population” has been changed to “growing gap between food supply and population growth”.

Comment 6: Page 2, lines 44. Explain what 60Mt is.

Reply: Thank you very much for your comments and suggestions. The point we are trying to make here is that from 1950 to 2005, the total annual erosion in southern China was over 60 million tons. 60Mt=60 million tons.

Comment 7: Page 2, lines 55. Changed to “have not received sufficient study” instead of not paid attention to.

Reply: Thank you very much for your comments and suggestions. “not paid attention to” has been changed to “have not received sufficient study”.

Comment 8: Page 2, lines 57. Suggest including a photograph of a gully. Many readers will not be familiar with the large scale of the gullies.

Reply: Thank you very much for your comments and suggestions. We have added pictures to the components of the collapse post, as shown in Figure 1.

Figure 1. Sketch of Benggang erosion in the granite hills of South China.

Comment 9: Page 2, lines 67. Unclear what is meant by strongly burst. Perhaps - fail catastrophically? Burst sounds like a dam burst, releasing water, but I don’t believe that is what is meant here. Please clarify.

Reply: Thank you for your detailed suggestions. In the revised manuscript, we have made careful revisions. The revised content is that these gullies are characterized by fast development and strong burst, which makes it more threatening than common soil erosion.

Comment 10: Page 2, lines 67. Please define this term. Areas that could not be accessed by farmers because of the gully?

Reply: Benggang management area: only under the action of water force and gravity, the land on the slope of the hill is damaged and the erosion phenomenon of collapse and scouring. The total prevention area refers to the total area of Benggang erosion management for each Benggang with erosion management area of 60m² or more.

Comment 11: Page 2, lines 74. Add "is taking place".

Reply: Thank you very much for your comments and suggestions. "is taking place" has been added in the revised manuscript. The modified content is that there is no vegetation cover and serious soil erosion and gravity erosion is taking place.

Comment 12: Page 2, lines 74. Does the stabilization occur naturally? What leads to stabilization?

Reply: Benggang restoration is mainly a restoration process of natural state. It is mainly vegetation and ecological restoration to let it gradually stabilize.

Comment 13: Page 2, lines 74. plural - soil nutrients as there is more than one.

Reply: Thank you for your detailed suggestions. We have carefully revised it. The modified content is that few studies have addressed soil fertility change caused in the process of soil restoration in Benggang area of South China.

Comment 14: Page 3, lines 101. Depth to bedrock?

Reply: Granite soils are susceptible to erosion, mainly because of the deep soil weathering layer.

Comment 15: Page 3, lines 121. Modification “At each site, first removed the litter, and carried out multi-point sampling according to the "S-shaped" strategy”.

Reply: Thank you for your detailed suggestions. In the revised manuscript, we have changed it to “At each site the litter was removed and sampling points were selected along an S shaped line”.

Comment 16: Page 3, lines 124. Change to “were”.

Reply: Thank you for your detailed suggestions. “was” has been changed to “were” in the revised manuscript.

Comment 17: Page 4, lines 166. Do you mean smaller soil pores or fewer?

Reply: Thank you for your detailed suggestions. “lower” has been changed to “smaller” in the revised manuscript.

Comment 18: Page 4, lines 168. Change to “variation was classified into three categories:”.

Reply: Thank you for your detailed suggestions. “variation had three stages:” has been changed to “variation was classified into three categories:” in the revised manuscript.

Comment 19: Page 5, lines 185. If there were no significant differences between soil bulk density, you can’t say that soil bulk density decreased with developing restoration. The differences could be due to random variation.

Reply: Thank you for your detailed suggestions. We have corrected it in the revised manuscript.

Comment 20: Page 5, lines 187-191. This figure needs more explanation. I don’t see AG, MG SG on the figure, I see UC and WT and WM. Where are these and the different colors explained? Need a footnote or note in the caption. It this top middle and lower?

Reply: Thank you for your detailed suggestions. In this Figure, we have annotated each acronym of in the revised manuscript. The all acronyms are annotated as follows. AG: Active stage of Benggang; MG: Semi-stable stage of Benggang; SG: Stable stage of Benggang. UC: upper catchment; WT, WM, WL: the top, middle and lower of collapsing wall; DT, DL: the top and lower of colluvial deposit; SC: scour channel; AT, AM, AE: the top, middle and edge of alluvial fan.

Comment 21: Page 5, lines 194. This trend is improvement or degradation? I would expect the bulk density to be reduced as soil fertility increased and more organic matter was incorporated into the soil. Likewise I would expect porosity to increase.

Reply: Thank you for your detailed suggestions. We have corrected it in the revised manuscript. This trend is improvement. Soil porosity and bulk density showed an opposite trend of change, that is, the bulk density decreased and the porosity increased.

Comment 22: Page 5, lines 199. Change to “is shown”.

Reply: Thank you for your detailed suggestions. We have corrected it in the revised manuscript.

Comment 23: Page 6, lines 201. Ah good, that clarifies the earlier question. This is what I would expect. what region? what is the process by which clay accumulates in stable areas? Is it possible they are stable because of the clay (resists erosion) rather than they have clay because they.

Reply: The gravel content decreased by 12.24% and 16.58% when the Benggang restoration from active stage to semi-stable stage to stable stage. Soil texture analysis indicated that the study area had the greater sand contents (38.00~61.03%) and lower clay contents (12.69~31.06%). The sand content decreased with increasing Benggang restoration, whereas the clay content showed the opposite trend. The sand contents in the active, semi-stable, and stable stages of Benggang restoration were 51.79%, 46.74% and 45.31%, respectively. While the clay contents were only 19.49%, 19.69% and 22.90%, respectively. In addition, there was no apparent variation in the silt content among different Benggang restoration stages. During the stabe stage of Benggang restoration, the surface vegetation increases, soil erosion is weaker, and the amount of clay loss is less. Meanwhile, soil root secretions and organic matter may have promoted the bonding of granite weathering material particles.

Comment 24: Page 6, lines 209. Provide a better legend for Figure 3.

Reply: Thank you very much for your comments and suggestions. We have corrected it in the revised manuscript.

Comment 25: Page 7, lines 240. Figure 4 is overlaid and is shown separately.

Reply: Thank you very much for your comments and suggestions. We have corrected it in the revised manuscript.

Comment 26: Page 7, lines 242. Where is SHC, soil hydraulic conductivity defined in methods? Cant find it.

Reply: Thank you very much for your comments and suggestions. We have changed the acronym of soil properties to the official name of soil properties.

Comment 27: Page 8, lines 249. Change to “did not vary in an obvious pattern".

Reply: Thank you very much for your comments and suggestions. “were no obvious vary” has been change to “did not vary in an obvious pattern" in the revised manuscript.

Comment 28: Page 8, lines 254. Delete - repeats beginning of sentence.

Reply: “which were shown as follows stable stage > semi-stable stage > active stage of Benggang restoration” has been deleted.

Comment 29: Page 8, lines 257. Give percentage for active stage as well.

Reply: Thank you very much for your comments and suggestions. In this study the coordinates at this location are large meaning that the cation exchange capacity of soil in the semi-stable stage and the stable stage of Benggang restoration was increased by 33.40% and 62.23%, respectively, compared to in the active stage of Benggang restoration.

Comment 30: Page 8, lines 257. Change punctuation.

Reply: Thank you very much for your comments and suggestions. We have corrected it in the revised manuscript.

Comment 31: Page 8, lines 265. I am confused. How is an in increase of 30.09% not obvious?

Reply: Thank you for your detailed suggestions. After another careful revision of the original text and ANOVA, it was shown that Total phosphorous (TP) and TK content in the stable stages of Benggang restoration were significant increased.

Comment 32: Page 8, lines 266. Chang to “had”.

Reply: Thank you for your detailed suggestions. “were” has been changed to “had” in the revised manuscript.

Comment 33: Page 8, lines 266-270. Grammar incorrect.

Reply: Thank you for your detailed suggestions. We have corrected it in the revised manuscript.

Comment 34: Page 8, lines 266-270. Discussed the upper catchment is pre-disturance, we would expect it to be fertile. The colluvial is a deposit, so it would be sandy, and anything soluble in water, such a clay and nutrients would have been carried away.

Reply: Thank you very much for your comments and suggestions. The reason is that the upper catchment area has more vegetation on the surface, more organic matter, complete soil structure and less soil erosion, while the colluvial sediment soil is loose, and soil and nutrients are more easily lost under the action of hydraulic erosion and gravity erosion.

Comment 35: Page 10. Figure 8 is out of place.

Reply: Thank you very much for your comments and suggestions. We have adapted the original figure in the revised manuscript.

Comment 36: Page 12, lines 295. Confusing to combine positive and negative in the same sentence. Not very informative, suggest rewriting.

Reply: Thank you very much for your comments and suggestions. Rewriting: There were extremely significantly positive correlations between the clay content and field water capacity, pH, CEC, TN, TP, TK, AN, AP and AK ((p < 0.01). The sand content had extremely significantly negative correlations with it (p < 0.01).

Comment 37: Page 12, lines 302. Explain significance of color and size of circles in Figure 10.

Reply: Thank you very much for your comments and suggestions. In this figure, the acronyms, color and circle size of the individual soil parameters are indicated. SHC: Saturated hydraulic conductivity; BD: Bulk density; STP: Soil total porosity; CP: Capillary porosity; NCP: Aeration porosity; SWC: Saturated water content; FWC: Field water capacity; OM: organic matter; CEC: Cation exchange capacity; TN: Total nitrogen; TP: Total phosphorus; TK: Total potassium; AN: Available nitrogen; AP: Available phosphorus; AK: Available potassium. Circle: The larger the correlation coefficient, the larger the circle. The smaller the correlation coefficient, the smaller the circle. Red: the correlation coefficient is positive, the redder the color, the closer to 1. Blue: the correlation coefficient is negative, the bluer the color, the closer to negative 1.

Comment 38: Page 14, lines 348. what is that?

Reply: Thank you very much for your comments and suggestions. “that” has been changed to “and”.

Comment 39: Page 14, lines 351. Chang to “part”.

Reply: Thank you very much for your comments and suggestions. “s” has been deleted.

Comment 40: Page 14, lines 356-359. Determine the acronyms for Table 4.

Reply: Thank you for your detailed suggestions. We have corrected it in the revised manuscript.

Comment 41: Page 15, lines 394. Add “were”.

Reply: Thank you for your detailed suggestions. We have added the word “were”.

Comment 42: Page 15, lines 394. The soil fertility after ecological restoration of Benggang is still at a lower lower. What is the reason?

Reply: It was possible that this area was more susceptible to Benggang erosion because of coarser soil properties initially. Therefore, the damage caused by Benggang erosion is enormous, and ecological restoration of erosion is more difficult after erosion. In this study we strive to provide quantitative ecological restoration evaluation.

Comment 43: Page 16, lines 424. Chang to “which are”.

Reply: Thank you very much for your comments and suggestions. “are” has been changed to “which are” in the revised manuscript.

Comment 44: Page 16, lines 433. Chang to “had not accumulated”.

Reply: Thank you very much for your comments and suggestions. “were no” has been changed to “had not accumulated” in the revised manuscript.

Comment 45: Page 16, lines 447. Is this referring to the PCA results? Unclear where these numbers are coming from.

Reply: PCA was applied to comprehensively evaluate the soil fertility at different stages of Benggang restoration. IBM SPSS Statistics 19.0 standardized the raw data for the 20 soil parameters involved in this study to ensure the objectivity and scientificity of the PCA results, while the 20 standardized soil parameters were recorded as ZSHC, ZBD, ZSTP, ZCP, ZNCP, ZSWC, ZGravel, ZSand, ZClay, ZSilt, ZFWC, ZpH, ZOM, ZCEC, ZTN, ZTP, ZTK, ZAN, ZAP, and ZAK. PCA was performed on the standardized data to derive the eigenvalues with variance contribution (Table 3) and the number of principal components (Table 3). Meanwhile, the loadings of each soil parameter corresponding to each of the three principal components were divided by the corresponding eigenvalues of the principal components (Table 2, λ₁=11.252, λ₂=3.689, and λ₃=12.281) to obtain the square root and the eigenvectors of each parameter corresponding to each of the three principal components. Therefore, according to the formulas for calculating the principal components, the functional expressions of the first three principal components can be obtained. The specific expressions are given in equations (1), (2) and (3) in the revised manuscript. Finally, the composite of each principal component score and the product of its corresponding contribution was calculated, and the expression is shown in equation (4) in the revised manuscript. The results are shown in Table 4.

Comment 46: Page 16, lines 449. Delete “The biological activity...Benggang restoration.”

Reply: “The biological activity...Benggang restoration.” has been deleted.

Finally, thank you again for your careful and detailed revision of this manuscript.

Author Response File: Author Response.pdf