The potential of UAV-borne spectral and textural information for predicting aboveground biomass and N fixation in legume-grass mixtures

Esther Grüner; Michael Wachendorf; Thomas Astor

doi:10.1371/journal.pone.0234703

Peer Review History

Original SubmissionDecember 16, 2019
5 Mar 2020 Decision Letter - Jana Müllerová, Editor PONE-D-19-34750 The potential of UAV-borne spectral and textural information for predicting aboveground biomass and N fixation in legume-grass mixtures PLOS ONE Dear Mrs. Grüner, 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. Please make sure you address all issues rised by the reviewers, especially focusing on Rew. 1 comments, clarifying the methods and providing both metadata and orthomosaics in supplements. We would appreciate receiving your revised manuscript by Apr 19 2020 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, Jana Müllerová, Ph.D Academic Editor PLOS ONE Journal Requirements: 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 http://www.journals.plos.org/plosone/s/file?id=wjVg/PLOSOne_formatting_sample_main_body.pdf and http://www.journals.plos.org/plosone/s/file?id=ba62/PLOSOne_formatting_sample_title_authors_affiliations.pdf 2. Our internal editors have looked over your manuscript and determined that it is within the scope of our Plant Phenomics & Precision Agriculture Call for Papers. This collection of papers is headed by a team of Guest Editors for PLOS ONE. The Collection will encompass a diverse range of research articles spanning disciplines, methods and applications. Additional information can be found on our announcement page: https://plos.io/phenomics. If you would like your manuscript to be considered for this collection, please let us know in your cover letter and we will ensure that your paper is treated as if you were responding to this call. If you would prefer to remove your manuscript from collection consideration, please specify this in the cover letter. 3. We note that you have stated that you will provide repository information for your data at acceptance. Should your manuscript be accepted for publication, we will hold it until you provide the relevant accession numbers or DOIs necessary to access your data. If you wish to make changes to your Data Availability statement, please describe these changes in your cover letter and we will update your Data Availability statement to reflect the information you provide. 4. Please include your tables as part of your main manuscript and remove the individual files. Please note that supplementary tables (should remain/ be uploaded) as separate "supporting information" files . [Note: HTML markup is below. Please do not edit.] Reviewers' comments: Reviewer's Responses to Questions Comments to the Author 1. 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: Partly Reviewer #2: Yes ******** 2. Has the statistical analysis been performed appropriately and rigorously? Reviewer #1: Yes Reviewer #2: Yes ****** 3. 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: No Reviewer #2: Yes ****** 4. 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 ****** 5. 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: 1. Is the manuscript technically sound, and do the data support the conclusions? Overall, the manuscript is technical sound and an interesting contribution to the field. The authors have performed a thorough data capture of field data and reference data as well. I would to suggest to review the following sections in order to provide a clarification: Materials and Methods A lot of data have been captured (multispectral UAS, Field Reference, GCP) and a lot of different variables have been computed and statistically analyzed. It would be very helpful to provide a summary table about all available data sets, calculated variables (VI, GLCM) and performed regression analysis. 165: Please make sure that the full experimental design necessary and relevant in order to follow your argumentation is summarized in this manuscript. It seems to me that this is described between 165 -174, please review this issue. 189 +: Fig. 1: From this figure it is not clear, how B (i.e. the design of the experimental Layout) can be seen in A? I would suggest to clearly indicate the layouts from B in A. UAV Image acquisition and data preprocessing. This chapter has significant potential for improvement. It is not clear why the UAS was flown manually and not using a predefined flight mission plan. This brings a certain level of uncertainty regarding data quality of UAS imagery as you always have different flight geometries. Furthermore, it is not clear why there has been a change of flight altitude between the first 2 flights and the 3rd flight resulting in different GSD’s for the different flights. Please argue, why flight 3 was included in the analysis as I assume a change in resolution will also affect for example the calculation of GLCM? In order make the photogrammetric processing transparent, I suggest to add as supplementary information the metadata from the processing reports, i.e. in particular the overlap, and also the RMSE as the authors have used GCP’s. In general, please add a comment what is the desired GSD in order to capture the desired grassland properly. How is this reflected in selecting the flight altitude in combination with sensor resolution. Please describe also, if, and if yes, how you performed a resampling as each UAS orthomosaic has a different resultion – what was here your final target resolution in order perform a proper coregistration of the individual images from each mission. It would also strengthen your manuscript, if you can provide the orthomosaics for all three missions. Data analysis and machine learning 245: Please explain, what do you mean by “avoiding the first 1.5 m”. In 167 you describe the size of a field plot is 1.5mx12m – if avoid 1.5 m – what is then left from the plot? Please clarify! Maybe a figure showing your analysis design in detail might help? A zonal statistic has been performed calculating the mean of each variable. I would suggest to provide here a basic statistic description of the variables including MIN, Max, STDV etc. At least I would suggest to add here a comment on variability of the individual variables and the potential of loosing information due to averaging? Texture features of images 251-252: Please explain, what is the rationale behind selecting 8 textural features out of the 14 as suggested by Haralick? Is there any evidence which of selected 8 is suitable for grassland texture? Please justify/argue/clarify your selection of texture features. Vegetation index calculation Please argue, why you have selected the mentioned 13 VI? 2. Has the statistical analysis been performed appropriately and rigorously? Yes. 3. Have the authors made all data underlying the findings in their manuscript fully available? Not for the review. 4. Is the manuscript presented in an intelligible fashion and written in standard English? Yes. 158: ……located in northern Hessen. Reviewer #2: The manuscript is very well organised and the English style is good. The topic is interesting for the potential impact on operational precision farming. I have just few concerns: 1) It seems that the multispectral images were calibrated in reflectance using the irradiance sensor installed on the UAV. If this is true, then your images were calibrated in reflectance at platform level and not in ground reflectance. Since you are processing a time series of images this could be an important aspect to discuss. Also VI can be affected by the atmosphere, depending on their formulation. I think that this argument deserves a discussion; 2) In you analyses you are using the 13 VI as independent variables. However I would like to stress that these VI are usually correlated and for sure they are correlated with the original bands values. Please confirm or not that this is not a problem for the validity of your application, from statistical point of view. Pag 17 - please check this sentence "The radiometric resolution was set to 0 to 255." ****** 6. PLOS authors have the option to publish the peer review history of their article (what does this mean?). If published, this will include your full peer review and any attached files. If you choose “no”, your identity will remain anonymous but your review may still be made public. Do you want your identity to be public for this peer review?** For information about this choice, including consent withdrawal, please see our Privacy Policy. 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. https://doi.org/10.1371/journal.pone.0234703.r001
Revision 1
31 Mar 2020 Author Response Manuscript ID: PONE-D-19-34750 - Response letter Dear Mrs. Müllerová, Dear Reviewers, thank you very much for the review of our manuscript titled „ The potential of UAV-borne spectral and textural information for predicting aboveground biomass and N fixation in legume-grass mixtures “, which greatly helped to improve it. We have carefully implemented the comments. Due to modification of the data processing (as proposed by Reviewer 1), major changes were made in section “UAV image acquisition and data pre-processing” (from L: 222), “Prediction models” (from L: 403) and minor changes in section “Discussion” (from L: 578). Providing metadata (140 data point with 52 variables) and eight orthomosaics to the supplements of this manuscript seems not operable to us. This data will be part of the published data in a public repository. Please find our specific answer to each reviewer’s comments below in bold letters. Yours sincerely Esther Grüner PLOS ONE Journal Requirements: 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 http://www.journals.plos.org/plosone/s/file?id=wjVg/PLOSOne_formatting_sample_main_body.pdf and http://www.journals.plos.org/plosone/s/file?id=ba62/PLOSOne_formatting_sample_title_authors_affiliations.pdf 2. Our internal editors have looked over your manuscript and determined that it is within the scope of our Plant Phenomics & Precision Agriculture Call for Papers. This collection of papers is headed by a team of Guest Editors for PLOS ONE. The Collection will encompass a diverse range of research articles spanning disciplines, methods and applications. Additional information can be found on our announcement page: https://plos.io/phenomics. If you would like your manuscript to be considered for this collection, please let us know in your cover letter and we will ensure that your paper is treated as if you were responding to this call. If you would prefer to remove your manuscript from collection consideration, please specify this in the cover letter. Yes, we would like our manuscript to be considered for Plant Phenomics & Precision Agriculture Call for Papers. Thank you. 3. We note that you have stated that you will provide repository information for your data at acceptance. Should your manuscript be accepted for publication, we will hold it until you provide the relevant accession numbers or DOIs necessary to access your data. If you wish to make changes to your Data Availability statement, please describe these changes in your cover letter and we will update your Data Availability statement to reflect the information you provide. Metadata and orthomosaics will be published at gfbio (German Federation for Biological Data: www.gfbio.org), which is in progress. 4. Please include your tables as part of your main manuscript and remove the individual files. Please note that supplementary tables (should remain/ be uploaded) as separate "supporting information" files . Done. [Note: HTML markup is below. Please do not edit.] Reviewers' comments: Reviewer's Responses to Questions Comments to the Author 1. 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: Partly Reviewer #2: Yes ________________________________________ 2. Has the statistical analysis been performed appropriately and rigorously? Reviewer #1: Yes Reviewer #2: Yes ________________________________________ 3. 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: No Reviewer #2: Yes ________________________________________ 4. 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 ________________________________________ Reviewer #1: 1. Is the manuscript technically sound, and do the data support the conclusions? Overall, the manuscript is technical sound and an interesting contribution to the field. The authors have performed a thorough data capture of field data and reference data as well. I would to suggest to review the following sections in order to provide a clarification: Materials and Methods A lot of data have been captured (multispectral UAS, Field Reference, GCP) and a lot of different variables have been computed and statistically analyzed. It would be very helpful to provide a summary table about all available data sets, calculated variables (VI, GLCM) and performed regression analysis. The authors agree, that a lot of different variables were included in the analysis. Therefore, a workflow (Fig. 2) for a better overview was designed and implemented to the section “Experimental site and ground truth data” (L. 299). 165: Please make sure that the full experimental design necessary and relevant in order to follow your argumentation is summarized in this manuscript. It seems to me that this is described between 165 -174, please review this issue. The authors ensured that all relevant information of the experimental design is included in section “Experimental site and ground truth data”. Minor changes were done (L. 173). 189 +: Fig. 1: From this figure it is not clear, how B (i.e. the design of the experimental Layout) can be seen in A? I would suggest to clearly indicate the layouts from B in A. The authors decided to keep two separate figures for a better overview. The figure (Fig. 1, L.: 188) has been modified for a better understanding how B is included in A by white borders of the plots in A. UAV Image acquisition and data preprocessing. This chapter has significant potential for improvement. It is not clear why the UAS was flown manually and not using a predefined flight mission plan. This brings a certain level of uncertainty regarding data quality of UAS imagery as you always have different flight geometries. Furthermore, it is not clear why there has been a change of flight altitude between the first 2 flights and the 3rd flight resulting in different GSD’s for the different flights. Please argue, why flight 3 was included in the analysis as I assume a change in resolution will also affect for example the calculation of GLCM? There are eight flight missions in total and two of them are done with a flight altitude of 50 m, whereas the remaining five are at 20 m. For these two flight missions the image overlap was 100%. Therefore, as a compromise between flight height and time, remaining cuts were flown at 20 m. All flight missions were flown manually as by removing the original camera, automatic flight missions were not possible due to internal technical problems. This information was included from L. 249 to 255. All flights were included in the analysis to keep data size high. This has only minor effects on spectral information, but the authors agree that it can affect texture analysis. Future work should focus on unified flight heights, which is now mentioned in section “Discussion” (L. 697). In order make the photogrammetric processing transparent, I suggest to add as supplementary information the metadata from the processing reports, i.e. in particular the overlap, and also the RMSE as the authors have used GCP’s. Done (S3 Table, L.: 965). The information about the number of overlapping images is given in L. 263. In general, please add a comment what is the desired GSD in order to capture the desired grassland properly. How is this reflected in selecting the flight altitude in combination with sensor resolution. GSD had minor effects on multispectral information. Our aim was to keep the flight missions feasible and, therefore, it was a compromise between flight time and resolution. This was implemented in L. 250. Please describe also, if, and if yes, how you performed a resampling as each UAS orthomosaic has a different resultion – what was here your final target resolution in order perform a proper coregistration of the individual images from each mission. The authors thank the editor for this comment and agree, that a resampling is necessary. The orthomosaics were resampled to a unified resolution of 4.5 cm (L. 280). Consequently, all analysis was repeated and results changed minor. It would also strengthen your manuscript, if you can provide the orthomosaics for all three missions. As there are eight orthomosaics in total (three harvests and five sub-sampling dates), such attachment would not substantially improve information in this manuscript. We suggest instead, that the orthomosaics will be part of the published data in a public repository. Data analysis and machine learning 245: Please explain, what do you mean by “avoiding the first 1.5 m”. In 167 you describe the size of a field plot is 1.5mx12m – if avoid 1.5 m – what is then left from the plot? Please clarify! Maybe a figure showing your analysis design in detail might help? To avoid disturbance of the sub-sampling in regrowth of biomass for the main harvests, the sub-sampling was restricted to the first 1.5 m (Fig. 1 B, light red area). Therefore, the remaining area for the analysis was 15.75 m2. This information was added in L. 290. A zonal statistic has been performed calculating the mean of each variable. I would suggest to provide here a basic statistic description of the variables including MIN, Max, STDV etc. At least I would suggest to add here a comment on variability of the individual variables and the potential of loosing information due to averaging? The authors agree, that by averaging variable values information may get lost. Nevertheless, by including texture features, spatial information is still part of the analysis. Due to the size and complexity the authors would like to avoid adding the statistical description (MIN, MAX, STDV etc.) for the 52 variables included in the study. Texture features of images 251-252: Please explain, what is the rationale behind selecting 8 textural features out of the 14 as suggested by Haralick? Is there any evidence which of selected 8 is suitable for grassland texture? Please justify/argue/clarify your selection of texture features. As the utilization of texture features was never done before in biomass estimation for grassland or legume-grass mixtures, there was no evidence for selecting certain texture features. This study was a first approach to using such information at all. This is emphasized in L. 307. In the future, a more systematic selection of the most important texture features may improve or simplify the biomass estimation models. Vegetation index calculation Please argue, why you have selected the mentioned 13 VI? We used VIs which could be created with the available 4 bands and which were mentioned in literature for biomass estimation of vegetation and grassland. This was clarified in L. 322. 2. Has the statistical analysis been performed appropriately and rigorously? Yes. 3. Have the authors made all data underlying the findings in their manuscript fully available? Not for the review. 4. Is the manuscript presented in an intelligible fashion and written in standard English? Yes. 158: ……located in northern Hessen. (L. 163) The authors disagree. In English the German state “Hessen” is called Hesse (though it sounds weird). Reviewer #2: The manuscript is very well organised and the English style is good. The topic is interesting for the potential impact on operational precision farming. I have just few concerns: 1) It seems that the multispectral images were calibrated in reflectance using the irradiance sensor installed on the UAV. If this is true, then your images were calibrated in reflectance at platform level and not in ground reflectance. Since you are processing a time series of images this could be an important aspect to discuss. Also VI can be affected by the atmosphere, depending on their formulation. I think that this argument deserves a discussion; The authors agree, that the atmosphere between sensor and ground can affect reflection. Nevertheless, flight height of 20-50 m was rather low and, thus, are the atmospheric effects on the reflectance. Additionally, it can be assumed that within the study area and given a very short flight time no fluctuation of the atmospheric conditions appeared. An atmospheric correction is rather used for satellite data and large areas, where atmospheric variation within the study area can be expected. Therefore, the authors would prefer to not discuss this in the manuscript. 2) In you analyses you are using the 13 VI as independent variables. However I would like to stress that these VI are usually correlated and for sure they are correlated with the original bands values. Please confirm or not that this is not a problem for the validity of your application, from statistical point of view. To deal with multispectral data, which usually suffers from multicollinearity, machine learning algorithms are a solution. This method is commonly used in the field of remote sensing also with grasslands. For a better understanding, this is emphasized in L. 341. Pag 17 - please check this sentence "The radiometric resolution was set to 0 to 255." (L. 309) Changed to 16 bits. Attachments Attachment Submitted filename: Response to reviewers.docx https://doi.org/10.1371/journal.pone.0234703.r002
19 May 2020 Decision Letter - Jana Müllerová, Editor PONE-D-19-34750R1 The potential of UAV-borne spectral and textural information for predicting aboveground biomass and N fixation in legume-grass mixtures PLOS ONE Dear Mrs. Grüner, 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. We would appreciate receiving your revised manuscript by Jul 03 2020 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, Jana Müllerová, Ph.D Academic Editor PLOS ONE Additional Editor Comments (if provided): Please add a short comment to the Discussion on the effects of atmosphere on your results [Note: HTML markup is below. Please do not edit.] 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: All comments have been addressed Reviewer #2: All comments have been addressed ******** 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: Yes ****** 3. Has the statistical analysis been performed appropriately and rigorously? Reviewer #1: Yes Reviewer #2: Yes ****** 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: No Reviewer #2: (No Response) ****** 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 ****** 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 really appreciate the work the authors have been performed in order to critically reflect and significantly have improved the research presented. From my point of view all comments have been clearly addressed and I recommend this contribution for publication. Reviewer #2: Dear Authors, it is true that a flight height of 20-50 m and a limited short flight duration (and small area) can suggest to do not apply any atmospheric correction. However my concern was about the processing of a time series of images. From one image time acquisition to another the atmospheric influence could be different. And this can affect the VI values. Please just shortly discuss this topic and how this could affect your analysis. ****** 7. PLOS authors have the option to publish the peer review history of their article (what does this mean?). If published, this will include your full peer review and any attached files. If you choose “no”, your identity will remain anonymous but your review may still be made public. Do you want your identity to be public for this peer review?** For information about this choice, including consent withdrawal, please see our Privacy Policy. 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. https://doi.org/10.1371/journal.pone.0234703.r003
Revision 2
22 May 2020 Author Response Manuscript ID: PONE-D-19-34750R1 - Response letter Dear Mrs. Müllerová, Dear Reviewers, thank you very much for the second review of our manuscript titled „ The potential of UAV-borne spectral and textural information for predicting aboveground biomass and N fixation in legume-grass mixtures”. We have carefully implemented the comments. Please find our specific answer to each reviewer’s comments below in bold letters. Yours sincerely Esther Grüner Reviewers' comments: Reviewer #1: I really appreciate the work the authors have been performed in order to critically reflect and significantly have improved the research presented. From my point of view all comments have been clearly addressed and I recommend this contribution for publication. Thank you. Reviewer #2: Dear Authors, it is true that a flight height of 20-50 m and a limited short flight duration (and small area) can suggest to do not apply any atmospheric correction. However my concern was about the processing of a time series of images. From one image time acquisition to another the atmospheric influence could be different. And this can affect the VI values. Please just shortly discuss this topic and how this could affect your analysis. We have carefully implemented this comment to L. 572-577 in the section “Discussion”. Attachments Attachment Submitted filename: Response to reviewers.pdf https://doi.org/10.1371/journal.pone.0234703.r004
2 Jun 2020 Decision Letter - Jana Müllerová, Editor The potential of UAV-borne spectral and textural information for predicting aboveground biomass and N fixation in legume-grass mixtures PONE-D-19-34750R2 Dear Dr. Grüner, We’re pleased to inform you that your manuscript has been judged scientifically suitable for publication and will be formally accepted for publication once it meets all outstanding technical requirements. Within one week, you’ll receive an e-mail detailing the required amendments. When these have been addressed, you’ll receive a formal acceptance letter and your manuscript will be scheduled for publication. An invoice for payment will follow shortly after the formal acceptance. To ensure an efficient process, please log into Editorial Manager at http://www.editorialmanager.com/pone/, click the 'Update My Information' link at the top of the page, and double check that your user information is up-to-date. If you have any billing related questions, please contact our Author Billing department directly at authorbilling@plos.org. If your institution or institutions have a press office, please notify them about your upcoming paper to help maximize its impact. If they’ll be preparing press materials, please inform our press team as soon as possible -- no later than 48 hours after receiving the formal acceptance. Your manuscript will remain under strict press embargo until 2 pm Eastern Time on the date of publication. For more information, please contact onepress@plos.org. Kind regards, Jana Müllerová, Ph.D Academic Editor PLOS ONE Additional Editor Comments (optional): Reviewers' comments: https://doi.org/10.1371/journal.pone.0234703.r005
Formally Accepted
15 Jun 2020 Acceptance Letter - Jana Müllerová, Editor PONE-D-19-34750R2 The potential of UAV-borne spectral and textural information for predicting aboveground biomass and N fixation in legume-grass mixtures Dear Dr. Grüner: I'm pleased to inform you that your manuscript has been deemed suitable for publication in PLOS ONE. Congratulations! Your manuscript is now with our production department. If your institution or institutions have a press office, please let them know about your upcoming paper now to help maximize its impact. If they'll be preparing press materials, please inform our press team within the next 48 hours. Your manuscript will remain under strict press embargo until 2 pm Eastern Time on the date of publication. For more information please contact onepress@plos.org. If we can help with anything else, please email us at plosone@plos.org. Thank you for submitting your work to PLOS ONE and supporting open access. Kind regards, PLOS ONE Editorial Office Staff on behalf of Dr. Jana Müllerová Academic Editor PLOS ONE https://doi.org/10.1371/journal.pone.0234703.r006

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