The Impact of Tree Species on Microbial Community Structure and Soil Function on Forest Plantations in the Central Hardwoods Region (CHR)
, Shaneka S. Lawson 3, Niall D. Lue Sue 3, Jeffery Handy 1 and Ralph H. Crawford 4Round 1
Reviewer 1 Report
Dear editor and the authors,
Here is the review of the paper titled " The impact of tree species on microbial community structure and soil function on forest plantations in Central Hardwoods Region (CHR)" written by Terrence G. Gardner & co-authors.
The manuscript has three objectives: (1) To evaluate the soil chemical properties for two hardwood tree monoculture stands - black walnut (BW, Juglans nigra and Northern red oak (RO, Quercus rubra) in Michigan (USA); (2) To identify whether soil microbial community composition and functions involved in nutrient cycling and SOM transformations differ by tree species in comparison with non-forested areas within the stands; and (3) to analyze the soil microbial dynamics across the four seasons. Methods used in the study included measurements of selected soil chemical properties, determination of microbial community structure using ester-linked fatty acid methyl ester (EL-FAME), and measurements of soil enzyme activities (EAs). The analysis showed a significant positive response to BW based on soil EAs and microbial indicators in comparison with RO. Microbial activcity was higher in summer than in winter. Fungi were dominant in microbial community structure with a fungal/bacterial ratio of 2:1. Gram-positive bacteria dominated the bacterial community. Acid phosphatase and arbuscular mycorrhizal fungi revealed strong correlations.
The manuscript English quality is very good. Introduction part should be expanded with the previous knowledge on the microbial community composition and enzyme activity within the tree stands of Juglans nigra and Quercus rubra. eDNA metabarcoding methods would add the additional perspective on the microbial composition of the same tree stands if performed in the future.
Please check my suggestions in the pdf version of the manuscript attached.
Best wishes, Reviewer
Comments for author File: 
Comments.pdf
Author Response
"The impact of tree species on microbial community structure and soil function on forest plantations in Central Hardwoods Region (CHR)" submitted to Forest.
Point-by-point response to reviewers comments:
We thank the reviewers and the editorial team for their interest in our work. All text changes in response to reviewer comments are now highlighted in yellow in the main text. We also modified Figure 1 and 2. We have responded to both reviewers and the content of these responses is below.
Answer to Reviewer 1
Dear editor and the authors,
Here is the review of the paper titled "
The impact of tree species on microbial community structure and soil function on forest plantations in Central Hardwoods Region (CHR)" written by Terrence G. Gardner & co-authors.
The manuscript has three objectives: (1) To evaluate the soil chemical properties for two hardwood tree monoculture stands - black walnut (BW, Juglans nigra and Northern red oak (RO, Quercus rubra) in Michigan (USA); (2) To identify whether soil microbial community composition and functions involved in nutrient cycling and SOM transformations differ by tree species in comparison with non-forested areas within the stands; and (3) to analyze the soil microbial dynamics across the four seasons. Methods used in the study included measurements of selected soil chemical properties, determination of microbial community structure using ester-linked fatty acid methyl ester (EL-FAME), and measurements of soil enzyme activities (EAs). The analysis showed a significant positive response to BW based on soil EAs and microbial indicators in comparison with RO. Microbial activity was higher in summer than in winter. Fungi were dominant in microbial community structure with a fungal/bacterial ratio of 2:1. Gram-positive bacteria dominated the bacterial community. Acid phosphatase and arbuscular mycorrhizal fungi revealed strong correlations.
The manuscript’s English quality is very good. The introduction part should be expanded with the previous knowledge on the microbial community composition and enzyme activity within the tree stands of Juglans nigra and Quercus rubra. DNA metabarcoding methods would add an additional perspective on the microbial composition of the same tree stands if performed in the future.
Please check my suggestions in the pdf version of the manuscript attached.
Suggestions on the manuscript attached:
Abstract
Line 24: regular font instead of italic
We replaced the letter type. Thanks for the suggestion.
Line 30: 2.1 -> 2:1
We changed the dot for the double dot. Thanks for the suggestion.
Line 34: mycorrhizal -> arbuscular mycorrhizal
We replaced mycorrhizal with arbuscular mycorrhizal. Thanks for the suggestion.
Keywords:
Omit author from keywords, Genus - first capital letter.
We made the changes suggested by the reviewers. Thanks for the suggestion.
Introduction
Line 40: regular font instead of italic
We replaced the letter type. Thanks for the suggestion.
Line 41: What is CHR, please describe it geographically?
We added more information about Central Hardwood Region. Thanks for the suggestion.
Line 76: Please list references about soil microbial community composition and function in BW and RO stands if there are any?
We added more information about soil microbial community composition and function in BW and RO in the introduction. There are not many papers that have studied the soil microbial communities using FAME analysis in Black Walnut or Red Oak. Thank you for the suggestion.
Material and Methods
Line 90: three
We change 3 by three. Thanks for the suggestion.
Line 99: Diameter of soil sample corer?
The diameter of the soil core was 3 cm and we added this information in the manuscript. Thanks for the suggestion.
Results
Line 153: Please use the term "saprotrophic" instead of "saprophytic" throughout the text.
We used the term "saprotrophic" throughout the text. Thanks for the suggestions.
Line 217: Part of the table is cut.
We moved the figure to have a better view. Thanks for the suggestions.
Discussion
Line 321: tanning content -> tannin content?
We changed tanning by tannin. Thanks for the suggestions
Line 358: regular font
We replaced the letter type. Thanks for the suggestion.
Line 373: mycorrhizal -> arbuscular mycorrhizal
We replaced mycorrhizal with arbuscular mycorrhizal. Thanks for the suggestion.
Line 442-445: Is this part of the manuscript?
We deleted this part of the text because It was an error from the original template. Thanks for the observation.
Reviewer 2 Report
The authors investigated the influences of tree species and season on soil microbial community and soil function. They found that tree species significantly influenced soil microbial community. However, after reading the whole manuscript, I found the statistical analyses and scientific writing were not well conducted. The below are some specific comments.
1. Line 31-32. Did this sentence clearly described? Please check it.
2. The numbers in keywords should be deleted.
3. Please improve the introduction by complementing research advances and elaborate the novelty.
4. Line 75. Please pay more attention for the tense of this sentence.
5. Line 88-96. Which growth stage is the BW and RO tree in 2019 and 2020? Are they in the same growth stage?
6. Line 107-112. Please add the methods of soil organic C determination or the calculation with TC. Analysis of Temp and Hum should also be described in this section.
7. Table 2. Why FAME abundances and EA were not compared among treatments with LSD or other statistical methods?
8. Table 2. Data in the last column were not well displayed.
9. Figure 1: Line 245-246. Where is the ANOVA results?
10. Table 3. Temp is temperature? Hum is soil moisture? These two environmental factors were not provided in table 1.
11. Line 449. ….decreased with RO should be checked again. From table 1, TOC, TC and TN did not significantly decreased with RO. Conclusions should be rewritten according to the results.
12. Why higher-resolution molecular-based techniques such as metagenomic DNA or RNA did not used in the current study? High-throughput sequencing have been widely used in the past years.
13. Please provide the importance of this research at the abstract or conclusions.
Author Response
"The impact of tree species on microbial community structure and soil function on forest plantations in Central Hardwoods Region (CHR)" submitted to Forest.
Point-by-point response to reviewers comments:
We thank the reviewers and the editorial team for their interest in our work. All text changes in response to reviewer comments are now highlighted in yellow in the main text. We also modified Figure 1 and 2. We have responded to both reviewers and the content of these responses is below.
Answer to Reviewer 2
The authors investigated the influences of tree species and season on soil microbial community and soil function. They found that tree species significantly influenced the soil microbial community. However, after reading the whole manuscript, I found the statistical analyses and scientific writing were not well conducted.
- We thank the reviewer for their constructive criticism of our manuscript.
The below are some specific comments.
- Line 31-32. Did this sentence clearly describe? Please check it.
We re-arranged the sentence with the objective to be more clear. Thanks for the suggestions.
- The numbers in keywords should be deleted.
We deleted the number in the keywords, thanks for the suggestion.
- Please improve the introduction by complementing research advances and elaborating on the novelty.
We added more information about research advances in black walnut and red oak. We also write about the importance of this work. Thank you very much for the suggestions.
- Line 75. Please pay more attention to the tense of this sentence.
We re-arranged the sentence with the objective to be more clear. Thanks for the suggestions.
- Line 88-96. Which growth stage is the BW and RO tree in 2019 and 2020? Are they in the same growth stage?
Both plant species were planted on the same date in 2008. They are young plants and have the same growth stage and maturity level.
- Line 107-112. Please add the methods of soil organic C determination or the calculation with TC. Analysis of Temp and Hum should also be described in this section.
We added the information on how TOC was calculated. The temperature and humidity information was obtained from U.S. Climate data (https://www.usclimatedata.com/climate/grand-rapids/michigan/united-states/usmi0344). Thanks for the suggestion.
- Table 2. Why FAME abundances and EA were not compared among treatments with LSD or other statistical methods?
Yes, both FAME abundance and EAs were compared with ANOVA. Tables 1, 2, and 3 have the p-values for the ANOVA analysis for comparison of Plant species, Season, and their interaction. The letters in the FAME abundance table were not added because there were no significant differences in the interaction between Plant species (PS) and season (S). We added the ANOVA analysis for the soil enzyme activities in Figure 1. Thank you for your indication.
- Table 2. Data in the last column were not well displayed.
We moved the figure to have a better view. Thanks for the suggestions.
- Figure 1: Line 245-246. Where are the ANOVA results?
We added the ANOVA results in Figure 1. Thanks for the suggestions.
- Table 3. Temp is temperature? Hum is soil moisture? These two environmental factors were not provided in Table 1.
The temperature was calculated based on annual temperature for only annual measurement for all the samples, for that reason, we did not put the values of temperature in Table 1 and we added them in the supplemental Figure 1.
- Line 449. ….decreased with RO should be checked again. From Table 1, TOC, TC, and TN did not significantly decrease with RO. Conclusions should be rewritten according to the results.
We re-written the conclusion according to the results. Thank you very much for your suggestions.
- Why were higher-resolution molecular-based techniques such as metagenomic DNA or RNA did not used in the current study? High-throughput sequencing has been widely used in the past years.
We acknowledge that higher-resolution molecular-based techniques such as metagenomic DNA or RNA are very important in this era and they can add tons of important information to our work. But FAME and molecular-based technologies have different objectives. In this work, we preferred to focus on quantitative traits like FAME abundance indicators and soil enzyme activities. We recognize that a more deep study of the microbial community compositions is needed but it is something that we will explore in the future. Thanks for the suggestions.
- Please provide the importance of this research in the abstract or conclusions.
We provided the importance of this work in both sections. Thanks for the suggestions.
Round 2
Reviewer 2 Report
Almost all questions have been addressed. The following section showed be reorganized carefully.
In abstract and conclusion sections, "This study is one of the first to assess how variations in microbial abundance and soil functions occur throughout the course of an entire year". In fact, microbial abundance and soil functions in different seasons have been investigated. I think it can be concluded as " these results indicate that ......"
Author Response
We thank the reviewer 2 and the editorial team for the second round of revisions.
Reviewer report
In abstract and conclusion sections, "This study is one of the first to assess how variations in microbial abundance and soil functions occur throughout the course of an entire year". In fact, microbial abundance and soil functions in different seasons have been investigated. I think it can be concluded as " these results indicate that ......"
We modified the text in the abstract and conclusions in accordance with these suggestions. We delated the phrase: "This study is one of the first to assess how" in both sections and we added " these results indicate that ......". Thanks a lot for the suggestion.
