Microbial Biomass and Rhizosphere Soil Properties in Response to Heavy Metal-Contaminated Flooding

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

Comments are included in the pdf file. 

Comments for author File: Comments.pdf

Author Response

Reviewer 1. comments and questions: (the replies are in italics)

1. Is not clear this sentence, It's means that chloroform fumigation and microscopic techniques were used to determine the soil microbial biomass C? Microscopic techniques is so large precise each one.  (Line 51.)

It was a citation of a work, where soil microbial biomass was estimated by two independent methods: chloroform fumigation and microscopic biovolume technique which resulted in the same conclusion. I do not know which of them is more precise, but using the chloroform fumigation method for estimating soil microbial biomass is more widespread. But it is not an important detail therefore we deleted this.   

2. Line 59. in the introduction: The question was if biomass specific respiration was increased resulted from the each treatment ?

We revisited the cited literature and modified it accordingly.

3. Line 142: Abbreviation for LE-extract:

Lakanen-Erviö (LE) extract; has changed in the text.  

4. Line 165: only acide phosphatase was measured it's better to test also the alkaline phosphatase beacause acid phosphatase was determined  also in plants not only by soil microorganism

We agree because the soil phosphatase enzymes could have originated from plants or soil microorganisms, but we measured only acid phosphomonoesterase activity because the soil was slightly acidic.

5. Line 176: correlation analysis with each test? Pearson test?  indicate the test used for correlation analysis in the text.

We are sorry to neglect to mention it. We have used Pearson’s correlation tests. It was amended in the text.

6. Line 194. add sulfur content data in the Tables 2 and 3

We have no data for soil sulfur content in our samples. We have soil sulfur data from a later sampling, but not in the same sampling points. We added these data to the text.

7. how to explain that basal soil respiration was increased in polluted soil however in the unpolluted soil the substrate-induced respiration was higher!!!

Virtually the means of basal soil respiration was higher in willow 1 and willow 2 polluted soils, but these differences were not significant. The substrate-induced respiration as an alternative method for estimating soil microbial biomass C, showed significantly higher values in corn and willow 2 unpolluted samples, while in willow 1 unpolluted were not significantly different (Figure 2). We added possible explanations in the discussion: 1) In heavy metal stress situations, the maintenance energy required to sustain microbial cells is higher than in non-stress situations, as evidenced by higher respiration rates, especially when expressed per unit microbial biomass rather than per unit soil mass.; 2) Heavy metal pollution reduces soil microbial biomass C, as reported in several studies.

Reviewer 2 Report

Comments and Suggestions for Authors

Attached

Comments for author File: Comments.pdf

Comments on the Quality of English Language

Minor editing will improve the quality of the manuscript.

Author Response

Reviewer 2. comments and questions, (response in italics): 

Title: It is suggested to revise the title like Microbial Biomass and Rhizosphere Soil Properties in Response to Heavy Metal Contaminated Flooding

We changed the title accordingly.

 L-81: “environs”- Is it environments?

We changed environs to environments.

 L-101:  a.s.l.-write full form

We amended it.

 L-229-230: willow-2 row had the highest soil microbial biomass C, while there was no significant difference between the willow-1 and corn rows (Figure 3)- There is no lettering in the tables as well as in the figures. Without the lettering, how to confirm whether there is significant difference or not?

 -In the tables, results are presented for the sampling points. To my opinion, it is better to present the results based on planting types (planting rows) like willow-1 unpolluted, willow-1 polluted…… corn unpolluted, corn polluted. Mean values for different sampling points should be considered. It is also suggested to use letters for the understanding of the significance status among the planting types. Other statistical values like CV (coefficient of variation) value, level of significance might be added.

We agree, for the indication of significant differences if exist, we added lettering for tables and symbols of significances in figure 2, 3 and 4.

 

 L-242: “these later had no significant difference”- not clear.

We have reworded the text.

L-277-279: “toxic metals Cd, Pb, Zn, As, and Cu, while a negative correlation was observed with soil phosphorus content (Figure 5). Significant correlations were found for key pollutants including zinc, cadmium, and lead.”- In figure 5, there is no indication regarding the positive or negative correlation. It should be mentioned in the figure legend.

We have reformulated Figure 5, showing Pearson’s correlations r by a color scale from -1 to 1, while the significance level has been also indicated.

Discussion: Need discussion on some points like “the pollution decreased in the three remediation rows in the following order: willow-2, willow-1, and corn.” It is suggested to include proper explanation in the discussion section.

- For heavy metals, it is important to discuss whether the values are exceeding the maximum permissible limits as prescribed by WHO or relevant organization.

We added the permissible environmental limits for soils in Table.

 

Overall comments: It is suggested to improve the results section by arranging the data as suggested. Discussion section should be improved based on the findings of the study. Discuss more elaborately the reasons of observed relationship between the studied soil parameters.

We tried to improve the results section by rearranging tables and figures and also the related text. We added more discussion about the observed relationships between the studied soil parameters.

Reviewer 3 Report

Comments and Suggestions for Authors

In this study, the authors investigated the soil microbial properties and determined the correlations between the biological and chemical properties of the soil at a metal-contaminated site in the northwest Hungary. They found that the soil of the contaminated sites had significantly higher levels of As, Pb, Zn, Cu, Cd, and Ca, whereas the unpolluted sites had significantly higher levels of phosphorus and potassium. The substrate-induced respiration showed a positive correlation with MBC and a negative correlation with the respiration quotient (qCO2). They proposed that the enhanced respiration quotient (qCO2) together with the decreased MBC/SOC ratio could be used to indicate the harmful effect of soil contamination by heavy metals in floodplain soils. However, I have some concern about this MS.

 

1.      A phytoremediation experiment was conducted, but there was no information or data on phytoremediation experiment in this MS. Phytoremediation for vegetation recovery or heavy metal removal?

2.      Could the authors provide the figure or map for sampling plots layout (18 plots, not only one point in figure 1)?

3.      The data in Table 1 and Table 2 were not analyzed, thus the differences in soil properties were not be concluded.

4.      The information in table 4 is the same with figure 2, figure 3, and figure 4. In my opinion, the figures could be better as the value was the mean ± SD. Please give the results of the statistical analysis. Meanwhile, the figures should be optimized.

5.      In section of conclusion, most of the text are result descriptions, the main results should be summarized in this section. The conclusion is not the replications of all results.

Comments on the Quality of English Language

Not easy to understand.

Author Response

Reviewer 3. comments and questions (responses in italics)

1. A phytoremediation experiment was conducted, but there was no information or data on phytoremediation experiment in this MS. Phytoremediation for vegetation recovery or heavy metal removal?

We added some more information about the phytoremediation experiment.

2. Could the authors provide the figure or map for sampling plots layout (18 plots, not only one point in figure 1)?

We supplemented the Figure 1 with the sampling area together with planting rows and sampling points.

3. The data in Table 1 and Table 2 were not analyzed, thus the differences in soil properties were not be concluded.

We added it.

4. The information in table 4 is the same with figure 2, figure 3, and figure 4. In my opinion, the figures could be better as the value was the mean ± SD. Please give the results of the statistical analysis. Meanwhile, the figures should be optimized.

Table 4 has been removed, and Figures 2,3, and 4 optimized supplementing with statistical analysis.

5. In section of conclusion, most of the text are result descriptions, the main results should be summarized in this section. The conclusion is not the replications of all results.

We wrote another conclusion, hoping that it would be suitable.

Comments on the Quality of English Language

Not easy to understand.

We tried to improve the clarity of the text, and also an English language improvement provided by the Author Service of the MDPI.

Round 2

Reviewer 2 Report

Comments and Suggestions for Authors

After revision, quality of the manuscript has improved. Some minor revision is needed

Include (Elaborately) the soil codes in the footnote of the tables.

L-390-391: “while the willow 1 not.”- It is better to write “except willow 1”.

Comments on the Quality of English Language

Minor editing is requires

Author Response

Comments and Suggestions for Authors

After revision, quality of the manuscript has improved. Some minor revision is needed

Include (Elaborately) the soil codes in the footnote of the tables.

L-390-391: “while the willow 1 not.”- It is better to write “except willow 1”.

Thank you for reviewing our manuscript, and thank you for your positive opinions.

The latest revision of the text has been highlighted in yellow.

The soil codes have been added to the footnotes of all tables.

The text has changed from “while the willow 1 not.” to “except willow 1”, as suggested.

Minor English editing was made.

Reviewer 3 Report

Comments and Suggestions for Authors

All my concerns have been addressed well. In my opinion, No more than 70 refs. may be more welcome.

Author Response

Reviewer comment:

All my concerns have been addressed well. In my opinion, No more than 70 refs. may be more welcome.

Thank you for reviewing our manuscript, and thank you for your positive opinions.

The latest revision of the text has been highlighted in yellow.

The number of references is considerable, but if it is not necessary to omit any, then it should not be done because that would necessitate changing the structure of the text by abbreviating it.