Biodiversity Characteristics and Carbon Sequestration Potential of Successional Woody Plants versus Tree Plantation under Different Reclamation Treatments on Hard-Coal Mine Heaps––A Case Study from Upper Silesia

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The manuscript aims to compare plant diversity and C storage between plots with different types of reclamation and succession, carboniferous bare rock vs. sites reclaimed by applying 50 cm of topsoil. Where topsoil was applied, the authors also compared the carbon stock between three different restoration strategies: natural regeneration, planting involving a single species and planting involving three other species. Despite the low number of replicates collected within each treatment, the results can contribute greatly to the knowledge of the restoration of hard-coal mine heap ecosystems. However, some important points must be reviewed to validate the authors' conclusions.

 

Abstract

Line 30 – the authors state that “Higher average value of Shanonn-Wiener’s Index was on unreclaimed sites vs. reclaimed". However, the results of the statistical analyzes showed that no significant differences were detected between these two substrates, so they cannot affirm this, even if the average values differed between unreclaimed and reclaimed sites.

 

Introduction

The introduction is well-written, but lacks some details about what the authors expect from the different treatments in terms of plant species diversity and carbon stock in this short period of time, between 10 and 15 years. There is some information that is in the material and methods item that should be in the introduction (see below).

 

Materials and Methods

Study site

The authors describe the total area of the heap, but do not describe the size of the areas occupied by the different treatments (defined as variants by the authors). Furthermore, it would be important to describe the origin of the topsoil that was applied in the different variants, whether they were from the same location or whether it came from different locations far from each other.

Line 142 – 150. It would be better if this information was in the introduction of the manuscript to justify the objectives of the study.

Line 162 – 166 – Why were particle size, bulk density and pH measured? These data were not part of the objectives and did not directly contribute to the discussion of the results and the conclusion of the study. If the authors' intention was to improve the description of the study area, it would be more appropriate to place this information in the “Study sites” item.

Line 208. Table 1 describes the equations used to estimate plant biomass, but it lacks species that were present in the different treatments. On the other hand, there are equations for plant species that were not mentioned in the treatments.

Line 215 – 218. The concepts of alpha and beta diversity must be checked and references must be cited. Alpha diversity is described in the literature as local diversity, expressed by species richness or Shannon-Wiener diversity. Beta diversity quantifies changes in species composition from one location to another, or between sites.

 

Results

Tables 2 and 3 have extremely small font sizes, which are difficult to read.

Lines 246 – 251. The description of the results requires more detail. Does the data in the tables show the mean and standard errors for each parameter and each variant? If yes, although obvious, it needs to be described in the table captions. But the most important thing is that by examining and comparing the standard errors, it does not appear at all that the variances are homogeneous between the variants. The authors mention in the Data analysis item that tests of normality and homogeneity of variances were checked. Was this really done? Was any data transformation used?

Lines 253-259.  The authors compare the S-BR variant with the other three TS variants. How was this done? Have the data from the three TS variants been pooled? Were all replicas of the TS variants considered? That is, was a set of four replicas compared with a set of 12 replicas? Combining the three TS variants overinflates the variance, since it would be expected that there will be variations between the TS variants and, therefore, there is a great risk of Type II error. The authors could leave the four variants separate and use Tukey or orthogonal contrasts to specify only the differences between BR and TS. Either way, there is no clear reason why all variants are not represented in the figures. Another question is that the representation of this data using a Box-Plot is inadequate due to the very low number of replications. This type of representation is used when there are dozens or even hundreds of observations and serves to clarify specific questions about the distribution of the data. When data is normal, bar graphs with standard errors are sufficient. This also applies to the Shannon-Wiener analysis and representation of diversity.

Discussion and Conclusion

The authors explain in detail that the amount of carbon is reflecting what was in the soil before the restoration actions. This would be expected because the time of 10 – 15 years seems to be very short for the incorporation of carbon into the soil. At a depth of 0 – 10 cm, part of the detected carbon could have been incorporated into the soil due to vegetation. Therefore, it would be more interesting for readers if the authors focused on the accumulation of carbon from vegetation and litter. However, in lines 301 and 302 the authors state that there is a greater C stock in Rb-TS compared to S-TS, which seems to be reflecting more the amount of carbon in the topsoil that was placed in these two variants than the amount that was driven by vegetation, as the authors did not mention the origin of this topsoil. This becomes more evident when examining the amount of total biomass coming from vegetation, which does not differ between the four variants, although the variances do not appear to be homogeneous.

 

Line -  353.  The values presented for the stock in the soil do not match those presented in Table 4.

 

Author Response

Rev. 1.

Rev. Line 30 – the authors state that “Higher average value of Shanonn-Wiener’s Index was on unreclaimed sites vs. reclaimed". However, the results of the statistical analyzes showed that no significant differences were detected between these two substrates, so they cannot affirm this, even if the average values differed between unreclaimed and reclaimed sites.

# Resp. The analysis included 3 variants on TS and a variant on BR, showing differences between H' values as significant. The analysis included 3 variants on TS and a variant on BR, showing differences between H' values as significant. Therefore, the provision is justified. The text content was clarified by the authors.

Rev. The introduction is well-written, but lacks some details about what the authors expect from the different treatments in terms of plant species diversity and carbon stock in this short period of time, between 10 and 15 years. There is some information that is in the material and methods item that should be in the introduction (see below).

 # Done. We have significantly improved the introduction.

Rev. The authors describe the total area of the heap, but do not describe the size of the areas occupied by the different treatments (defined as variants by the authors). Furthermore, it would be important to describe the origin of the topsoil that was applied in the different variants, whether they were from the same location or whether it came from different locations far from each other.

# Resp. The top layers of soil used for reclamation came from the place next to the heap where the nearby highway was being built. The area occupied by individual variants has not been precisely estimated. This would require more precise measurements using e.g. GIS tools.

Rev. Line 142 – 150. It would be better if this information was in the introduction of the manuscript to justify the objectives of the study.

# Resp. While improving the article and taking into account the editor's comment, we decided to remove this fragment.

Rev. Line 162 – 166 – Why were particle size, bulk density and pH measured? These data were not part of the objectives and did not directly contribute to the discussion of the results and the conclusion of the study. If the authors' intention was to improve the description of the study area, it would be more appropriate to place this information in the “Study sites” item.

# Resp. We moved the description of soil texture, pH and BD to the “Study site” section. We also created a new table 1.

Rev. Line 208. Table 1 describes the equations used to estimate plant biomass, but it lacks species that were present in the different treatments. On the other hand, there are equations for plant species that were not mentioned in the treatments.

# Resp. The tree species occurring in study variants are listed in Table 1.

Rev. Line 215 – 218. The concepts of alpha and beta diversity must be checked and references must be cited. Alpha diversity is described in the literature as local diversity, expressed by species richness or Shannon-Wiener diversity. Beta diversity quantifies changes in species composition from one location to another, or between sites.

 # Resp. The reviewer's comment was justified, it was taken into account and the text was reworded.

Rev. Tables 2 and 3 have extremely small font sizes, which are difficult to read.

# Resp. Done.

Rev. Lines 246 – 251. The description of the results requires more detail. Does the data in the tables show the mean and standard errors for each parameter and each variant? If yes, although obvious, it needs to be described in the table captions. But the most important thing is that by examining and comparing the standard errors, it does not appear at all that the variances are homogeneous between the variants. The authors mention in the Data analysis item that tests of normality and homogeneity of variances were checked. Was this really done? Was any data transformation used?

# Resp. Done. Considering the low number of replicates (study plots), we decided to use non-parametric statistical tests.

Rev. Lines 253-259.  The authors compare the S-BR variant with the other three TS variants. How was this done? Have the data from the three TS variants been pooled? Were all replicas of the TS variants considered? That is, was a set of four replicas compared with a set of 12 replicas? Combining the three TS variants overinflates the variance, since it would be expected that there will be variations between the TS variants and, therefore, there is a great risk of Type II error. The authors could leave the four variants separate and use Tukey or orthogonal contrasts to specify only the differences between BR and TS. Either way, there is no clear reason why all variants are not represented in the figures. Another question is that the representation of this data using a Box-Plot is inadequate due to the very low number of replications. This type of representation is used when there are dozens or even hundreds of observations and serves to clarify specific questions about the distribution of the data. When data is normal, bar graphs with standard errors are sufficient. This also applies to the Shannon-Wiener analysis and representation of diversity.

# Resp. Changes were made, taking into account the detailed division into TS variants. All variants of the TS were considered separately in statistical analyses.

Discussion and Conclusion

Rev. The authors explain in detail that the amount of carbon is reflecting what was in the soil before the restoration actions. This would be expected because the time of 10 – 15 years seems to be very short for the incorporation of carbon into the soil. At a depth of 0 – 10 cm, part of the detected carbon could have been incorporated into the soil due to vegetation. Therefore, it would be more interesting for readers if the authors focused on the accumulation of carbon from vegetation and litter. However, in lines 301 and 302 the authors state that there is a greater C stock in Rb-TS compared to S-TS, which seems to be reflecting more the amount of carbon in the topsoil that was placed in these two variants than the amount that was driven by vegetation, as the authors did not mention the origin of this topsoil. This becomes more evident when examining the amount of total biomass coming from vegetation, which does not differ between the four variants, although the variances do not appear to be homogeneous.

# Done. Thank you for your comments, it has been taken into account. After non-parametric statistical analysis, no significant differences were found.

Rev. Line -  353.  The values presented for the stock in the soil do not match those presented in Table 4.

# Done. The values have been corrected.

 

Reviewer 2 Report

Comments and Suggestions for Authors

I am resubmitting my review since the last one was lost in the web.

It is a good paper and can be published. I have some points that need to be raised though: 

l. 223-224 Tukey test follows ANOVA to determine the sample pairs that differ. Mention ANOVA before Tukey tests.

Please add relevant citations for the above.

l. 215-218 Beta diversity measures the turnover (change) in species composition in different samples. We do not use species abundance data for beta diversity. Also, there are literally dozens of formulae that calculate beta diversity. The authors must let the readers know which one they will use. Be careful, Shannon 's index measures alpha diversity NOT beta diversity.

l. 29 We use the term alpha diversity NOT biodiversity alpha

Comments on the Quality of English Language

None

Author Response

Rev. 2.

 

 

Rev. l. 223-224 Tukey test follows ANOVA to determine the sample pairs that differ. Mention ANOVA before Tukey tests. Please add relevant citations for the above.

# Done. Considering the low number of study plots and the comment of Reviewer 1, we decided to use non-parametric statistical tests. Relevant citations was added.

Rev. l. 215-218 Beta diversity measures the turnover (change) in species composition in different samples. We do not use species abundance data for beta diversity. Also, there are literally dozens of formulae that calculate beta diversity. The authors must let the readers know which one they will use. Be careful, Shannon 's index measures alpha diversity NOT beta diversity. l. 29 We use the term alpha diversity NOT biodiversity alpha

# Changes were made. Thank you for pointing out the mistake.

 

Comments on the Quality of English Language

 

# Done. English proofreading by a native speaker was performed (on the website: https://proofreading.org/).

 

Reviewer 3 Report

Comments and Suggestions for Authors

1. In order for the chart to be relatively independent of the text, it is recommended that the full name of the variant be written in the note for the first occurrence.

2. Some data need to confirm the results of significant differences. Some experimental groups should have significant differences through the observation of data and standard deviation, which need to be confirmed. For example, Clay of 0-10 in Table 2, and tree density, stem biomass, branch biomass in Table 3.

3. Please add the total plant biomass to Table 3 including floor plant, shrub and tree.

4. Missing Important Data Table 4.

Comments on the Quality of English Language

Some words are not used properly, please check and revise them throughout.

Author Response

Rev. 3.

Rev.: 1. In order for the chart to be relatively independent of the text, it is recommended that the full name of the variant be written in the note for the first occurrence.

# Done.

Rev.: 2. Some data need to confirm the results of significant differences. Some experimental groups should have significant differences through the observation of data and standard deviation, need to be confirmed. For example, Clay of 0-10 in Table 2, and tree density, stem biomass, branch biomass in Table 3.

# Done. Considering the low number of replicates (study plots) and the comment of Reviewer 1, we decided to use non-parametric statistical tests. The tables present standard errors, which have lower values than standard deviations. No significant differences were found in the mean values of the mentioned parameters.

Rev.: 3. Please add the total plant biomass to Table 3 including floor plant, shrub and tree.

# Done.

Rev.: 4. Missing Important Data Table 4.

# Done.

Rev. Comments on the Quality of English Language - Some words are not used properly, please check and revise them throughout.Dół formularza

# Done. English proofreading by a native speaker was performed (on the website: https://proofreading.org/).

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

The manuscript has been corrected and improved compared to the previous version. All questions were answered, leaving the text clearer and more objective.

 

Author Response

Thank you for your thorough review and good comments.

Reviewer 3 Report

Comments and Suggestions for Authors

No changes have been made for this note.

Rev.: 3. Please add the total plant biomass to Table 3 including floor plant, shrub and tree.

Author Response

Done. Thank you for your thorough review and usefull comments.