Contribution of the Soil Macro- and Microstructure to Organic Matter Stabilisation in Natural and Post-Mining/Industrial Soils under Temperate Climatic Conditions

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

Please see the attached file.

Comments for author File: Comments.pdf

Author Response

1. In the abstract, authors did not well concluded the contribution of the soil macro- and microstructure to organic matter stabilisation, please revise the abstract, how the soil macro- and microstructure influence the organic matter stabilisation?

The abstract was rewritten.

 

2. Line 12 , “ the old brownfield soils” this expression is not good, confused the reader, please revise to commonly used soil classification. For example, according to soil World Reference Base for Soil Resources 2014, Update 2015: International Soil Classification System for Naming Soils and Creating Legends for Soil Maps. World Soil Resources Reports No. 106., World Soil Resources Reports No. 106.

Studied soils were classified according to WRB 2022, and the names were included in tables. However, the former names were used throughout the article because the WRB classification did not allowed us to differentiate soils according to their age (brownfield and old brownfield soils), lines: 157-159

According to the IUSS Working Group WRB (2022) soil classification, the soils derived from gypsum belonged to  Gypsiric Chernic Phaeozems (Siltic or Arenic), while the mining and industrial soils were Spolic Technosols (Humic, Siltic, Toxic).

 

3. Line 146 and Line 174, “2.3. Laboratory analysis of disturbed soils samples” is same as “2.4. Laboratory analysis of undisturbed soils samples ”, please revise.

To make clearer the difference between line 146 and 173 the titles of these two subsections were modified

Line 146: Laboratory analysis of soil samples with a disturbed structure

Line 174: Laboratory analysis of soil samples with an undisturbed structure

 

4. Line 102, in 2.1. Study areas, soil bedrock and sampling section, please add the climate types of the study areas, and I suggest authors give a climate type for study area according to the climate classification of Köppen Geiger.

The climate description and code according to Köpper Geiger climate classification was included in section: 2.1. Study areas, soil bedrock and sampling . Lines 141-144

The climate of the study area is of continental type with a warm summer and rainfalls throughout the whole year, with an average annual precipitation about 600 mm and a temperature about 6°C, classified as: Dfb according to the climate classification of Köpper Geiger.

 

5. Line 343-345, please do not put the equation in the text of the discussion, you maybe put it in a table/figure/Appendix.

The equation was put in Table 4 and moved to Results section, lines: 357-360

Table 4. Multiple linear regression analysis

Equation	R2 adj	p
SOM=14.623 – 3.155CaCO3 + 0.065DHA + 8.55Por mac + 8.27Por mic + 0.029Agg mic             (0.000)    (0.007)           (0.011)          (0.015)             (0.015)             (0.024)	0.989	<0.000

Among the soil parameters included in the calculation CaCO₃ contents, DHA, Por mac, Por mic and Agg mic resulted as the parameters significantly influencing SOM contents in studied soils. 

6. Please give a short conclusion at the end of manuscript

Conclusions were added at the end of the manuscript. Lines 508-518

5. Conclusions

We checked the contribution of the soil macro- and microstructure on SOM stabilisation through comparing the SOM contents and its stabilisation (decomposition of SOM, aggregate formation and their water resistance) of natural well-stabilised SOM of gypsum soils with the one of mining/industrial soils of different ages. We established that the mining/industrial soils had either similar or lower amounts of SOM and types of microstructures to the rich in SOM gypsum soils, however the SOM stabilisation differed according to the age the brownfield soils, being less stabilised in 50-years old soils and similarly stabilised in the oldest, about 150-400 years old brownfield soils. The wider implication of the presented research is to draw attention of the decision makers to the environmental importance of chemically degraded soils, especially when due to the conditions immobilization of pollutants in the soil can be assumed.

 

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

In this article, by contrasting the physicochemical properties of natural gypsum soils and  mining areas soils, it is determined that soils within mining areas possess an inherent capability for self-rehabilitation, capable of engendering a carbon sequestration effect. The manuscript is characterized by a coherent overall structure and a comparatively rational design, rendering the research of certain practical relevance. However, there are several suggestions for the authors' consideration:

1. Is the objective of the study to compare natural soils with those of mining areas to ascertain their carbon sequestration effects?

2.It is recommended to augment the introduction with a discussion on the significance of the research.

3. In the sampling process, how are undisturbed points determined? Please provide additional clarification.

4.Does the article compare natural soils with those from mining areas and, by analyzing the physicochemical properties of the soils, conclude that the organic matter content is lower in comparison to natural soils, thereby inferring a carbon sequestration effect?

5.In the discussion, section 4.3 could benefit from an enhanced discourse on the relationship between porosity and soil organic matter content, facilitating a deeper understanding among readers of the impact of porosity on the stability of organic matter.

6.For the ease of readership, it is advisable to revise the format of the discussion to align scientific hypotheses introduced in the introduction with the ensuing discussion systematically.

Author Response

1. Is the objective of the study to compare natural soils with those of mining areas to ascertain their carbon sequestration effects?

The aims were added, lines: 103-106

In our work we aimed at: (i) checking in what degree physical properties related to macro- and microstructure affect the soil organic matter properties and stability,  and (ii) to compare natural soils with those of mining areas to ascertain their carbon sequestration effects

 

2. It is recommended to augment the introduction with a discussion on the significance of the research.

The significance of the research was added, lines: 92-98

The significance of this research leads in emphasising the environmental role of degraded soils, especially those left for years without reclamation, which may help in making appropriate decisions regarding their sustainable management. In the literature mining/industrial soils are studied mainly due to the risk to human health and environmental quality resulting from their contamination [11, 13, 16]. Their importance in the context of SOM storage and possible role in climate mitigation is much less considered [3, 22].

 

3. In the sampling process, how are undisturbed points determined? Please provide additional clarification.

The clarification of the sampling process was added, lines: 154-155

Undisturbed and disturbed soil samples were taken out from the same randomly selected sampling points at the site, after digging a pit.

 

4. Does the article compare natural soils with those from mining areas and, by analyzing the physicochemical properties of the soils, conclude that the organic matter content is lower in comparison to natural soils, thereby inferring a carbon sequestration effect?

The clarification of the capacity of SOM storage in mining/industrial soils compared to the natural ones was given below and in the text in Abstract and in Conclusions

The amounts of SOM in mining/industrial soils were similar or lower than these in natural soils, but SOM contents in mining/industrial soils were compared with natural soils which were very rich in SOM. Therefore the contents of SOM in mining soils even being lower than in natural ones still were high. Natural and mining soils differed in SOM stability. Generally more stable SOM characterized natural soils than mining/industrial ones, however the oldest among the mining soils had SOM of similar stability.

 

5. In the discussion, section 4.3 could benefit from an enhanced discourse on the relationship between porosity and soil organic matter content, facilitating a deeper understanding among readers of the impact of porosity on the stability of organic matter.

In the discussion section 4.3 additional information regarding relation between SOM and porosity was included, lines: 461-466 and 476-479.

For this reason, they often reflect the effects of the soil biota [42], determining the physical suitability of the space for microbial colonisation and moderating predation by the mesofauna thus optimizing the process of SOM transformation [39]. Biogenic pores are the effects of earthworms or roots activity, which both stimulate storage and aggregation of SOM. According to Bosch-Serra et al [13] and Johannes et al [42] the volume of pores and the pore structure are named quality descriptors of SOM because they are directly related with the formation of aggregates in which SOM is well stabilised.

The relationship between the formation of pores of different sizes and the accumulation of SOM as an aggregation agent was also confirmed in previous works by a positive correlation between the area covered by pores and the amount of organic C [41].

 

6. For the ease of readership, it is advisable to revise the format of the discussion to align scientific hypotheses introduced in the introduction with the ensuing discussion systematically.

The structure of the Discussion was slightly changed by changing the order of the sections. Now they are in order:

• Drivers of natural and mining/industrial soil formation

4.2. Factors affecting SOM storage

4.3. Share of aggregation and pore structure in SOM storage: Effect of excessive amounts of Zn, Pb and Cd in the mining/industrial soils

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

The papaer made a very good impression. However, there are some comments:

1) The paper does not describe the soil sampling technique; it only states that samples were taken to a depth of 15 cm at 24 points. It is not clear how many collection points were organized at each of the research sites.

2) There is no description of the plant community at the soil sampling site, only the annotation indicates that the samples were taken in with similar grass plant communities.

 

3) After the Discussion section, a Conclusion section should be added.

Author Response

1. The paper does not describe the soil sampling technique; it only states that samples were taken to a depth of 15 cm at 24 points. It is not clear how many collection points were organized at each of the research sites.

   The information about sampling technique was added, lines 153-156

At each site, three sampling points were designated, totalling 24 sampling points. Undisturbed and disturbed soil samples were taken out from the same randomly selected sampling points at the site, after digging a pit. For the analyses, we collected soil samples from the top layers 0–15 cm deep.

 

2. There is no description of the plant community at the soil sampling site, only the annotation indicates that the samples were taken in with similar grass plant communities.

List of main grass species was added in Appendix as Table A1.

TABLE A1. Main grass species occurring on studied sites

Grass species

Festuca ovina

Calamagrostis epigejos

Festuca rubra

Dactylis glomerata

Poa pratensis

Arrhenatherum elatius

Deschampsia caespitosa

Festuca pratensis

 

3. After the Discussion section, a Conclusion section should be added.

The conclusion section was added, lines: 507-518

5. Conclusions

We checked the contribution of the soil macro- and microstructure on SOM stabilisation through comparing the SOM contents and its stabilisation (decomposition of SOM, aggregate formation and their water resistance) of natural well-stabilised SOM of gypsum soils with the one of mining/industrial soils of different ages. We established that the mining/industrial soils had either similar or lower amounts of SOM and types of microstructures to the rich in SOM gypsum soils, however the SOM stabilisation differed according to the age the brownfield soils, being less stabilised in 50-years old soils and similarly stabilised in the oldest, about 150-400 years old brownfield soils. The wider implication of the presented research is to draw attention of the decision makers to the environmental importance of chemically degraded soils, especially when due to the conditions immobilization of pollutants in the soil can be assumed.

Author Response File: Author Response.pdf

Reviewer 4 Report

Comments and Suggestions for Authors

1.The abstract section needs to be improved to be more logical.

2.Line 81, I would use “few studies have investigated” rather than “no studies”. It is hard for the authors to review all papers about this problem.

3.The last paragraph in the Introduction section needs to be improved. It seems that the hypothesis was described in this paragraph. The research goal, method, main content, structure in this study should be clarified.

4.Table 1, “Buk”. The arrow obscures the text.

5.The authors provide a comprehensive discussion section. However, an independent conclusion section is needed, which describes the main findings of this paper. 

6.Line 475, for other conditions and soils, can authors predict or assume the results according to this study? The wider implications based on the conclusion of this study is recommended to be further provided.

Author Response

            1.The abstract section needs to be improved to be more logical.

             It was re-written.

 

2. Line 81, I would use “few studies have investigated” rather than “no studies”. It is hard for the authors to review allpapers about this problem.

            It was corrected

3. The last paragraph in the Introduction section needs to be improved. It seems that the

            hypothesis was described in this paragraph. The research goal, method, main content,

            structure in this study should be clarified.

             It was improved.  The significance of the study (lines: 92-98) and goals (lines: 103-106) were added,

The significance of this research leads in emphasising the environmental role of degraded soils, especially those left for years without reclamation, which may help in making appropriate decisions regarding their sustainable management. In the literature mining/industrial soils are studied mainly due to the risk to human health and environmental quality resulting from their contamination [11, 13, 16]. Their importance in the context of SOM storage and possible role in climate mitigation is much less considered [3, 22].

In our work we aimed at: (i) checking in what degree physical properties related to macro- and microstructure affect the soil organic matter properties and stability, and (ii) to compare natural soils with those of mining areas to ascertain their carbon sequestration effects.

 

4. Table 1, “Buk”. The arrow obscures the text.

It was corrected

 

5. The authors provide a comprehensive discussion section. However, an independent conclusion section is needed, which describes the main findings of this paper.

Conclusions were added.

5. Conclusions

We checked the contribution of the soil macro- and microstructure on SOM stabilisation through comparing the SOM contents and its stabilisation (decomposition of SOM, aggregate formation and their water resistance) of natural well-stabilised SOM of gypsum soils with the one of mining/industrial soils of different ages. We established that the mining/industrial soils had either similar or lower amounts of SOM and types of microstructures to the rich in SOM gypsum soils, however the SOM stabilisation differed according to the age the brownfield soils, being less stabilised in 50-years old soils and similarly stabilised in the oldest, about 150-400 years old brownfield soils. The wider implication of the presented research is to draw attention of the decision makers to the environmental importance of chemically degraded soils, especially when due to the conditions immobilization of pollutants in the soil can be assumed.

 

6. Line 475, for other conditions and soils, can authors predict or assume the results according to this study? The wider implications based on the conclusion of this study is recommended to be further provided.

It was provided at the of the conclusions.

The wider implication of the presented research is to draw attention of the decision makers to the environmental importance of chemically degraded soils, especially when due to the conditions immobilization of pollutants in the soil can be assumed.

 

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

Authors did a good revision based on the comments.

Reviewer 4 Report

Comments and Suggestions for Authors

Thanks for the authors' revision.