PONE-D-19-19569

Up on the roof and down in the dirt: differences in soil properties (SOM, potassium, phosphorus and pH) and their relationship to each other between sedum and wildflower green roofs.

PLOS ONE

Dear Ms McAlister,

Thank you for submitting your manuscript to PLOS ONE. After careful consideration, we feel that it has merit but does not fully meet PLOS ONE’s publication criteria as it currently stands. Therefore, we invite you to submit a revised version of the manuscript that addresses the points raised during the review process.

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ACADEMIC EDITOR: Please address the comments listed under "Additional Editor Comments"

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Luitgard Schwendenmann

Academic Editor

PLOS ONE

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1. When submitting your revision, we need you to address these additional requirements.

Please ensure that your manuscript meets PLOS ONE's style requirements, including those for file naming. The PLOS ONE style templates can be found at

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3. In your Methods, please include a specific statement that permission was obtained from all building owners for the removal of green roof soil samples for the purposes of your study.

Additional Editor Comments:

While the topic is of interest, I would like to ask for further details regarding the methods and a critical assessment of the findings. 7 roofs were selected and a varying number of samples (depending on the size of the roof) were sampled. What is the reasoning to consider each sample taken at a given roof as independent (n=50). In my opionion these are pseudo-replicates. Further, did you test for an age effect (time since establishment) and even more critical is the difference between the substrates. It remains unclear whether your questions relate to substrate (e.g. line 163) or plant type (e.g. 172/173). How can substrate and plant type be separated (what is cause and effect)? Another aspect which needs to be addressed before I consider sending the manuscript for review is the difference between the carbon content at the time of establishment (baseline - carbon emboddied in the substrate) and time of sampling. In my opinion it is more relevant to consider the difference (not the total amount). I am looking forward to your response.

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Reviewers' comments:

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PONE-D-19-19569R1

Up on the roof and down in the dirt: differences in soil properties (SOM, potassium, phosphorus and pH) and their relationship to each other between sedum and wildflower green roofs.

PLOS ONE

Dear Ms McAlister,

Thank you for submitting your manuscript to PLOS ONE. After careful consideration, we feel that it has merit but does not fully meet PLOS ONE’s publication criteria as it currently stands. Therefore, we invite you to submit a revised version of the manuscript that addresses the points raised during the review process.

==============================

This paper provides a good snapshot but further revisions are required.

I agree with reviewer 1. If the material is an engineered green roof it is not appropriate to refer to them as soil. I recommend to use the term "substrate" throughout the manuscript. And replace "edaphic" by substrate characteristics.

The authors have to address this concern ("However, I don’t know how any conclusions can be made that sedum may be better than wildflowers at sequestering carbon. Are the differences in all the variables due to the plant type or to the differences in the soil components? The soils on the sedum roofs were composed of recycled bricks while the soils on the wildflower roofs were composed of an assortment of different aggregates and composts. Differences in SOM, pH, and P likely existed before plants were even installed. Maybe plant type had no effect.") and provide further clarification. This is a critical limitation of the study and needs to be discussed.

==============================

We would appreciate receiving your revised manuscript by Nov 07 2019 11:59PM. When you are ready to submit your revision, log on to https://www.editorialmanager.com/pone/ and select the 'Submissions Needing Revision' folder to locate your manuscript file.

If you would like to make changes to your financial disclosure, please include your updated statement in your cover letter.

To enhance the reproducibility of your results, we recommend that if applicable you deposit your laboratory protocols in protocols.io, where a protocol can be assigned its own identifier (DOI) such that it can be cited independently in the future. For instructions see: http://journals.plos.org/plosone/s/submission-guidelines#loc-laboratory-protocols

Please include the following items when submitting your revised manuscript:

• A rebuttal letter that responds to each point raised by the academic editor and reviewer(s). This letter should be uploaded as separate file and labeled 'Response to Reviewers'.
• A marked-up copy of your manuscript that highlights changes made to the original version. This file should be uploaded as separate file and labeled 'Revised Manuscript with Track Changes'.
• An unmarked version of your revised paper without tracked changes. This file should be uploaded as separate file and labeled 'Manuscript'.

Please note while forming your response, if your article is accepted, you may have the opportunity to make the peer review history publicly available. The record will include editor decision letters (with reviews) and your responses to reviewer comments. If eligible, we will contact you to opt in or out.

We look forward to receiving your revised manuscript.

Kind regards,

Luitgard Schwendenmann

Academic Editor

PLOS ONE

Additional Editor Comments (if provided):

This paper provides a good snapshot but further revisions are required.

I agree with reviewer 1. If the material is an engineered green roof it is not appropriate to refer to them as soil. I recommend to use the term "substrate" throughout the manuscript. And replace "edaphic" by substrate characteristics.

The authors have to address this concern ("However, I don’t know how any conclusions can be made that sedum may be better than wildflowers at sequestering carbon. Are the differences in all the variables due to the plant type or to the differences in the soil components? The soils on the sedum roofs were composed of recycled bricks while the soils on the wildflower roofs were composed of an assortment of different aggregates and composts. Differences in SOM, pH, and P likely existed before plants were even installed. Maybe plant type had no effect.") and provide further clarification. This is a critical limitation of the study and needs to be discussed.

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Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

1. If the authors have adequately addressed your comments raised in a previous round of review and you feel that this manuscript is now acceptable for publication, you may indicate that here to bypass the “Comments to the Author” section, enter your conflict of interest statement in the “Confidential to Editor” section, and submit your "Accept" recommendation.

Reviewer #1: (No Response)

Reviewer #2: (No Response)

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2. Is the manuscript technically sound, and do the data support the conclusions?

The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented.

Reviewer #1: Yes

Reviewer #2: Partly

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3. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #1: Yes

Reviewer #2: I Don't Know

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4. Have the authors made all data underlying the findings in their manuscript fully available?

The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified.

Reviewer #1: Yes

Reviewer #2: Yes

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5. Is the manuscript presented in an intelligible fashion and written in standard English?

PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here.

Reviewer #1: Yes

Reviewer #2: Yes

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6. Review Comments to the Author

Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)

Reviewer #1: I noticed that you have changed substrate to soil in many places in the manuscript (eg lines 96 , 171 in the revised manuscript with track changes). If the substrates on the green roofs really are engineer green roof media, I am not sure it is appropriate to refer to them as soils. I do understand that this can make the terminology cumbersome, but I think it is an important distinction.

Introduction

Lines 49-51: the list is missing commas.

Results

Lines 197-199: you say the first two components account for 89.6% of variation, which components are these?

Discussion:

Line 293: “However, the caveat that phosphorus…” this wording is a bit odd. I would suggest replacing caveat with another word.

Line 376: “connoting” seems like the wrong word to use hear.

Reviewer #2: The paper provides a good snapshot in time of the soil properties present at the time of measurement. However, I don’t know how any conclusions can be made that sedum may be better than wildflowers at sequestering carbon. Are the differences in all the variables due to the plant type or to the differences in the soil components? The soils on the sedum roofs were composed of recycled bricks while the soils on the wildflower roofs were composed of an assortment of different aggregates and composts. Differences in SOM, pH, and P likely existed before plants were even installed. Maybe plant type had no effect. There needs to be a soil analysis of the original soils. This is impossible now, but the soil samples could be mixed with the original ingredients that would give a reasonable estimate of the baseline properties.

Also, there is little information on plants. What is a sedum roof and what is a wildflower roof? Any grasses? Plant species could have a major impact on soil properties. A list of plant species should be included to describe each roof.

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Reviewer #1: No

Reviewer #2: No

[NOTE: If reviewer comments were submitted as an attachment file, they will be attached to this email and accessible via the submission site. Please log into your account, locate the manuscript record, and check for the action link "View Attachments". If this link does not appear, there are no attachment files to be viewed.]

While revising your submission, please upload your figure files to the Preflight Analysis and Conversion Engine (PACE) digital diagnostic tool, https://pacev2.apexcovantage.com/. PACE helps ensure that figures meet PLOS requirements. To use PACE, you must first register as a user. Registration is free. Then, login and navigate to the UPLOAD tab, where you will find detailed instructions on how to use the tool. If you encounter any issues or have any questions when using PACE, please email us at figures@plos.org. Please note that Supporting Information files do not need this step.

Up on the roof and down in the dirt: differences in substrate properties (SOM, potassium, phosphorus and pH) and their relationship to each other between sedum and wildflower green roofs.

PONE-D-19-19569R2

Dear Dr. McAlister,

We are pleased to inform you that your manuscript has been judged scientifically suitable for publication and will be formally accepted for publication once it complies with all outstanding technical requirements.

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With kind regards,

Luitgard Schwendenmann

Academic Editor

PLOS ONE

Additional Editor Comments (optional):

Thank you for replacing "soil" by "substrate". I highly recommend to replace "soil organic matter" by "organic matter" for consistency.

Reviewers' comments: