Comparison of Bacterial Diversity in the Rhizosphere of Chromolaena odorata (L.) R.M. King and H.Rob. in Different Habitats
Round 1
Reviewer 1 Report
In this study, authors compared microbial diversity in the rhizosphere of Chromolaena odorata among three different habitats, and found significant difference in the diversity and functional group of bacteria between abandoned land and eucalyptus forests. The study is simple, but the results are interesting and the manuscript is well written. I have only some minor comments.
Line 13: studies seldom focused on
Line 21: the three habitats
Line 55-56: This seems to mean that you will study a large number of invasive species. As you studied only one species, I suggesting removing this sentence.
Line 58: West India.
Line 63: the invasion of
L66-67: You may point out such studies conducted in nature reserves are particularly rare
Line 185: “A1–A3 are from the abandoned land, B1–B3 are from the young eucalyptus forest, and C1–C3 are from the mature eucalyptus forest.” should be “A1-A3 represent samples from the abandoned land, B1-B3 represent samples from the young eucalyptus forest, and C1-C3 represent from the mature eucalyptus forest.”
Line 196: “The young and mature eucalyptus forest samples are clustered to each other in the figure, which indicates a more similar species composition between the two types of soil” This sentence should be past tense.
Line 320-322：This sentence should be past tense.
Line 322-324: Please rewrite this sentence.
Please proofread the whole manuscript again.
Author Response
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Reviewer 2 Report
The study monitors three different environments in relation to the rhizosphere of the invasive species Chromolaena odorata. the study presents a series of statistical analyzes that are not detailed enough, for example, we can do an ANOVA in the R software with different packages and different parameter configurations. More information is needed on how the analyzes were implemented so that they can be repeated, which is a premise of the scientific method, after all, the present work is an exercise in applied statistics. The discussion and conclusion failed to say whether the results align with expectations or differ from the hypothesis that led to defining the rhizosphere of the invasive species Chromolaena odorata as the object of study. At the same time, more information in the literature review and discussion about the statistical techniques selected for these analyses are welcome.
Author Response
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Reviewer 3 Report
Attached
Comments for author File: Comments.pdf
Author Response
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Reviewer 4 Report
General:
The paper tries to describe the effects of a plant invader on the soil bacteria community amongst three different habitats. Whilst authors have used very advanced techniques and the paper has some newness, I believe they have forgotten some basics concepts. For instance, sampling is very low (9 samples, apparently), not all variables are correctly described in the methods and an underlying assumption that habitats were different prior to the invasion makes, at this stage, it difficult to accept the paper. Nonetheless, if authors clarify the issues raised here, I believe their work can advance the literature on plant invasions and soil bacterial communities. In addition, authors use many different acronyms which somehow impairs the readability of the paper. I would pick up the ones that appear more (like, OUT) and remove the others.
Abstract:
The abstract is well written, however, its last sentence “Results provided ideas for further exploring the mechanism of the successful invasion of C. odorata among different habitats” is inconclusive. Please, adjust here and give some insights for the future.
Introduction:
Why is important to study the effects of Chromolaena odorata invasion in the rhizosphere? It would be beneficial if the lack of studies was not the main reason for it. I mean, can this explain invasion success? Is this process linked to greenhouse gas emissions? By which mechanisms increasing the number of bacteria in the soil this plant invader increases it competitiveness?
Callaway et al. is missing the year of citation (Line 43).
Although authors describe their goals (Lines 71-75), I firmly believe that stating hypotheses is a better manner than what was done. The reason for this is that one can perceive how the plant invader can make the modifications in the environment, rather than reporting results after getting them.
Material and Methods:
Authors initiate the methodology stating in Lines 80-82 that “Due to the complex and changeable terrain of the nature reserve, the climate differs in the low mountains, peaks, valleys, and depressions”, so that habitat are contrasting naturally. I find it difficult to understand how the invasive species can explain the differences found in the soil bacteria community if, beforehand, the habitats are so diverse. Are there any characteristics that could eliminate a prior difference between sites? Perhaps, insert a table with summarizing this information/data regarding the habitats you have conducted the study. This will still not be sufficient, but it might be a start. In addition, I believe you will have to disentangle climate and habitat effects to really indicate how the invasion process can lead to differences in the soil bacterial community.
What are the main impacts this plant invader causes in the area? I found it difficult to understand. Please, provide some additional information here (Lines 84-85).
Please, indicate the age of the eucalyptus plantations. Young and mature forest are vague.
Authors mention they recorded information on the invasive plant cover, height, and number, but this is not present in the text (results and discussion). They later discuss density (and biomass), but this is a completely different ecological parameter. Please, standardize and input the information completely.
In Lines 98-106 authors mention a variety of methods to quantify different soil variables, but neither they provide any references, nor they correctly describe any of these. Please, adjust the text providing information on how you have obtained the data.
Why only the top 15 phyla were selected for the stacked histogram analysis? Are they the most abundant? Please, explain.
I am confused if authors used R or SPSS. Please, elucidate this better. Moreover, why did you pick Simpson instead of Shannon diversity index?
Results:
Authors began their results describing that there are many differences in soil physiochemistry features that are drivers of soil bacteria communities, which is consistent with my thoughts on prior differences amongst habitats driven not by the invader itself, but the habitats’ natures. Please, discuss this limitation of your work.
Authors refer to biomass results and density, but they did not mention in the methodology how they have assessed these data. Please, insert such relevant information describing the methods for harvesting plants and/or counted density.
Line 159 Habitats => habitats.
Apparently Figure 1 describes the OTUs that are shared by the different habitat researched, thought this need to clearer in the text.
I found Figure 2 quite confusing. Can the A1, A2, A3, and so on, follow their order? In addition, what is the scale in the right (goes from -1 to 2?)?
Where are the statistical values for the results?
I recommend dividing Figure 4 into two other figures. It is impossible to read Figure 4C.
I do not believe Figure 5 is needed. Would suggest putting as supplementary.
Discussion:
The discussion needs to be readdressed based on the results you got. I found it very difficult to keep reading and believe that you have deepened/focused to much on the different bacterial rather than the effects of C. odorata as a driver of it. The second and the third paragraphs are excessively big, and I recommend breaking both into other two.
I do not understand what authors have written in Lines 316-317: “Although only nine sets of soil data were used for data analysis, they were actually 316 produced by mixing 27 types of soils”. The reason for that is if you used 27 different types of soil would you end up having a replicate per soil, which is not enough for statistics. Please, reword or exclude.
Please, incorporate the limitations of your study. To me it is clear that you have not correctly evaluated the effects that habitats have on the soil bacteria community, which can contrast to your own results.
Conclusions:
How can your study provide a theoretical basis for further studies if you have not considered beforehand habitats differences?
Please, include more which taxon was modified by the presence of the invader and how this can affect ecosystem functioning as a result of the invasion.
Author Response
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Round 2
Reviewer 2 Report
Congratulations!
Author Response
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Reviewer 4 Report
Thank you for all your efforts to modify the manuscript. It has increased a lot the readability and also clarified most issues I was concerned about. Two things: (1) state in the abstract the age of the young (one-year) and mature (eight-years) of the plantations; (2) incorporate in the text that Simpson diversity index was not different between sites, while the other indexes were.
Author Response
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