Nematode Assemblages Development Twenty-One Years after the Introduction of Meadow Soil into Bare Post Mining Spoil Heap

Round 1

Reviewer 1 Report

This article presents an interesting study of nematode community dynamics during regenerative succession. The study is well planned and performed. The conclusions are justified and have practical importance. The article has some controversial features, which I have outlined below.

 

1.     The authors formulate a hypothesis in which they mention "Transported blocks," but they do not mention this term anywhere before, and such a hypothesis looks somewhat speculative. It is necessary to give arguments or information on the basis of which this hypothesis was formulated in the literature review.

2.     The second hypothesis was formulated as follows: "total numbers as well as trophic distribution in the transported blocks will be similar to those in the spoil substrate after 20 years of succession". However, it is necessary to clarify whose total numbers and trophic distribution we are talking about. The category of similarity of abundance and trophic structure is indefinite, so it cannot be tested. When comparing the two variants, we can talk about whether there is a statistically significant difference or not. If we are talking about similarity, it is necessary to specify a third variant, and then the evaluation of the position of the studied object relative to the two (or larger) alternatives will be the measure of similarity. But the category of similarity is not explicitly considered in the article.

3.     Table 1: it is necessary to specify the response to which characteristic of the trophic structure was investigated: it was the proportion in percent or absolute abundance. Note that "percentage" characteristics belong to the category of the so-called composite variables for which it is unreasonable to apply the methods of statistical analysis that were developed for normal distributions. Table 1: it is necessary to specify the response to which characteristic of the trophic structure was investigated: it was the proportion in percent or absolute abundance. Note that "percentage" characteristics belong to the category of the so-called composite variables for which it is unreasonable to apply the methods of statistical analysis that were developed for normal distributions. In order to apply appropriate statistical procedures, including ANOVA, to the percentage data, they must first be transformed accordingly.  The absolute abundance of trophic groups can be directly analyzed using ANOVA, but usually the data are log-transformed previously. Ideally, the data should follow a normal law of distribution, but such a test requires a somewhat larger dataset, but usually such detail is not always followed. The role of community abundance in trophic group abundance variation should be extracted by applying community abundance as a covariate in the GLM procedure.

4.     Table 1: p-levels of significance of differences are presented in the tables, but the results do not indicate directions of change. Figure 1 can not be a source of this kind of information, because the variability of the indicators shown in it has a complex nature and to identify the causes of this variability and conducted ANOVA. Thus, the results of the analysis are not fully presented.

5.     Table 2. Various ecological indices (mean ± SD) – N ?

6.     Table 2: Descriptive statistics are obviously not enough to understand the factors that influence them. It is necessary to conduct tests of significance and role of predictors by ANOVA or GLM methods

7.     Not only the state of the initial nematode community, but also the transformation of soil conditions and the dynamics of organic matter play an important role in the formation of the community structure over 20 years. I think it makes sense to mention these features in the discussion of the obtained results.

 After minor improvements, the article can be recommended for publication

Author Response

Dear reviewer, thank you very much for the time and the effort invested into reviewing of my manuscript. I value your notes and comments and made following changes to the manuscript:    

1. The authors formulate a hypothesis in which they mention "Transported blocks," but they do not mention this term anywhere before, and such a hypothesis looks somewhat speculative. It is necessary to give arguments or information on the basis of which this hypothesis was formulated in the literature review.

- I mentioned this term in paragraph before and extended this paragraph (lines 72-75).

 

2. The second hypothesis was formulated as follows: "total numbers as well as trophic distribution in the transported blocks will be similar to those in the spoil substrate after 20 years of succession". However, it is necessary to clarify whose total numbers and trophic distribution we are talking about. The category of similarity of abundance and trophic structure is indefinite, so it cannot be tested. When comparing the two variants, we can talk about whether there is a statistically significant difference or not. If we are talking about similarity, it is necessary to specify a third variant, and then the evaluation of the position of the studied object relative to the two (or larger) alternatives will be the measure of similarity. But the category of similarity is not explicitly considered in the article.

 

- You are right, formulation of hypotheses was vague. We decided to make an assumption (that transported blocks will serve as refugium) and then defined only one hypothesis (lines 77-80).

 

3. Table 1: it is necessary to specify the response to which characteristic of the trophic structure was investigated: it was the proportion in percent or absolute abundance. Note that "percentage" characteristics belong to the category of the so-called composite variables for which it is unreasonable to apply the methods of statistical analysis that were developed for normal distributions. Table 1: it is necessary to specify the response to which characteristic of the trophic structure was investigated: it was the proportion in percent or absolute abundance. Note that "percentage" characteristics belong to the category of the so-called composite variables for which it is unreasonable to apply the methods of statistical analysis that were developed for normal distributions. In order to apply appropriate statistical procedures, including ANOVA, to the percentage data, they must first be transformed accordingly.  The absolute abundance of trophic groups can be directly analyzed using ANOVA, but usually the data are log-transformed previously. Ideally, the data should follow a normal law of distribution, but such a test requires a somewhat larger dataset, but usually such detail is not always followed. The role of community abundance in trophic group abundance variation should be extracted by applying community abundance as a covariate in the GLM procedure.

- Note about the transformation was added to  the Materials  and methods (lines 179-180)

 

4. Table 1: p-levels of significance of differences are presented in the tables, but the results do not indicate directions of change. Figure 1 can not be a source of this kind of information, because the variability of the indicators shown in it has a complex nature and to identify the causes of this variability and conducted ANOVA. Thus, the results of the analysis are not fully presented.

- I changed Figure  to graph with absolute abundances and relative abundances were added to the Table 1 with the results oh variance analyses.

 

5. Table 2. Various ecological indices (mean ± SD) – N ?

- Number of samples was added to the table

 

6. Table 2: Descriptive statistics are obviously not enough to understand the factors that influence them. It is necessary to conduct tests of significance and role of predictors by ANOVA or GLM methods

- The table was extended by results of One-way/Factorial ANOVA.

 

7. Not only the state of the initial nematode community, but also the transformation of soil conditions and the dynamics of organic matter play an important role in the formation of the community structure over 20 years. I think it makes sense to mention these features in the discussion of the obtained results.

 

• Paragraph dealing with this issue was added to the Discussion (lines 424-432).

Reviewer 2 Report

The study is interesting, implementing a long term hypothesis of high environmental importance for soil biodiversity recovery. There are some issues that have to be addressed:

 

lines 20-21, abundance differences between C and B, and C and A were also statistical significant? Please add this info here

 

Probably the part “lines 55-62” fits better after line 46, followed by the scope of the study afterwards

 

Also, the scope paragraph (lines 63-66) has to be written more in detail

 

In Materials and Methods, a short history off the coal mining in the study area should be added. When started etc

 

I would recommend the Figure S1 to be included as a regular figure instead of supplementary material. It describes an important part of the Materials and Methods

 

 

Lines 107, 121, 122: How were these species were identified? Morphologically? Using what keys? This has to be added

Author Response

Dear reviewer, thank you very much for the time and the effort invested into reviewing of my manuscript. I value your notes and comments and made following changes to the manuscript:    

 

 

lines 20-21, abundance differences between C and B, and C and A were also statistical significant? Please add this info here

• Added to the abstract. I also modified the statement after re-checking the results (lines 20-23)

 

Probably the part “lines 55-62” fits better after line 46, followed by the scope of the study afterwards

• Rearranged as proposed 

 

Also, the scope paragraph (lines 63-66) has to be written more in detail

• We extended the paragraph as suggested (lines 72-80)

 

In Materials and Methods, a short history off the coal mining in the study area should be added. When started etc

• I added some information about the heap (lines 82-85), however, I inspected several papers from this area and there is lack of information about local mining activities. Moreover, with all the respect to your opinion, I personally find this information redundant.

 

 

I would recommend the Figure S1 to be included as a regular figure instead of supplementary material. It describes an important part of the Materials and Methods

• As proposed, Figure S1 is now Figure 1 and added into the manuscript text.

 

Lines 107, 121, 122: How were these species were identified? Morphologically? Using what keys? This has to be added

-information about first sampling campaign added to Materials and Methods (lines 172-174)

Reviewer 3 Report

Manuscript is quite well written, however I have some remarks:

Line 65 – in the title you mentioned 19 years (not 20). And the soil was transported in 1995 – so it was 21 years for possible succession. Please be consistent.

All ecological indices should be explained in Material and methods (how they were calculated).

The discussion is too short, it should be deeper. For example these ecological indices are not mentioned at all in the discussion section.

Author Response

Dear reviewer, thank you very much for the time and the effort invested into reviewing of my manuscript. I value your notes and comments and made following changes to the manuscript:    

 

Line 65 – in the title you mentioned 19 years (not 20). And the soil was transported in 1995 – so it was

21 years for possible succession. Please be consistent.

- Thank you for noticing, you are absolutely right. 19 years is an interval between sampling campaigns – hence the Title. I rewrote it to 21 years since we are indeed talking about ongoing succession.

 

All ecological indices should be explained in Material and methods (how they were calculated).

- I added all equations to Supplementary material

The discussion is too short, it should be deeper. For example these ecological indices are not mentioned at all in the discussion section.

- I added some paragraphs into the discussion as advised (lines 414-432)