A Google Earth Engine Algorithm to Map Phenological Metrics in Mountain Areas Worldwide with Landsat Collection and Sentinel-2
Round 1
Reviewer 1 Report
Dear Editors,
This manuscript should be rejected due to incorrect structure. It lacks a true Discussion, which should be an interpretation of the obtained results against the background of previously published studies.
Without this, there is no point in considering the manuscript for publication in a scientific journal.
Kind regards
Author Response
Response to Reviewer 1 Comments
We would like to thank reviewers for their appropriate comments and helpful suggestions that have been carefully considered. Majority of provided suggestions highlighted gaps in the text and were really useful to improve, we hope, paper quality. In point referees can find their comments, in response authors’ actions to reply/satisfy requests.
In particular, the synthesis of reviewers’ comments suggested a deep revision in paper organization and harmonization. Consequently, you will find some structural changes aimed at simplifying paper reading and make content more effective.
All comments were carefully evaluated and for the most of them corrections and integrations have been provided. Thank you so much for your work!
Point 1 : This manuscript should be rejected due to incorrect structure. It lacks a true Discussion, which should be an interpretation of the obtained results against the background of previously published studies. Without this, there is no point in considering the manuscript for publication in a scientific journal.
Response 1: Firstly, we would like to thank the reviewer for his/her suggestion. However, we are sorry for your negative judgment of a job that have required a lot of time for the development of the code and its validation. Nevertheless, in order to change the reviewer's opinion, we have worked hard to improve the quality and rigor of the text in the light of his/her valuable criticisms and the comments of other reviewers. As suggested the discussion section has deeply revised considering better the interpretation of the results against the background of previously published studies. We hope that the text can now be judged differently. We therefore refer to the manuscript for the appropriate evaluations in this regard.
Reviewer 2 Report
This research develops a mountain phenological index algorithm based on Google Earth Engine algorithm, which is of certain significance in general. But there are still some problems:
(1) The presentation of the article is poor, and the tables and figures are very poor.
(2) 2. Materials and Methods seem to be a list, not a standard research paper, and need to be greatly modified.
(3) RMSE and MAE are put into the results, which should be put into the materials and methods.
(4) The conclusion has no substantive content and needs to be re
(5) It is difficult to be persuasive without quotation support.
Author Response
Response to Reviewer 2 Comments
We would like to thank reviewers for their appropriate comments and helpful suggestions that have been carefully considered. Majority of provided suggestions highlighted gaps in the text and were really useful to improve, we hope, paper quality. In point referees can find their comments, in response authors’ actions to reply/satisfy requests.
In particular, the synthesis of reviewers’ comments suggested a deep revision in paper organization and harmonization. Consequently, you will find some structural changes aimed at simplifying paper reading and make content more effective.
All comments were carefully evaluated and for the most of them corrections and integrations have been provided. Thank you so much for your work!
This research develops a mountain phenological index algorithm based on Google Earth Engine algorithm, which is of certain significance in general. But there are still some problems:
Point 1: The presentation of the article is poor, and the tables and figures are very poor.
Response 1: Firstly, we would like to thank the reviewer, we are partially agreed with the referee. The presentation has to be improved and we have done it (please see into the text) anyway our aim and the main core of the work was the algorithm (its open-source form) and its validation this is wahy the manuscript is short and there are not so many figures and tables anyway we have improved them as suggested.
Point 2: Materials and Methods seem to be a list, not a standard research paper, and need to be greatly modified.
Response 2: We agree with the reviewer and we have changed the text in order to be much much clear. It is worth noting that the input datasets ware reported as a “list” because of they are input collection Earth Observation data in Google Earth Engine from whom phenological metrics can be computed in GEE thanks to the code. Anyway, considering the reviewer suggestion we have changed deeply this section. Please see into the manuscript.
Point 3: RMSE and MAE are put into the results, which should be put into the materials and methods.
Response 3: The reviewer is right we have moved it to the material and methods section as wisely suggested. Please see into the text.
Point 4: The conclusion has no substantive content and needs to be improved.
Response 4: The reviewer is right we have rewritten this section and hopefully improved please see into the manuscript.
Point 5: It is difficult to be persuasive without quotation support.
Response 5: The reviewer is partially right therefore to be much more persuasive in discussion and conclusions we have better reported the results obtain and the potentiality of the code by underling also the robustness from a statistical validation analysis. Please see into the manuscript.
Reviewer 3 Report
Reconsider after major revision
Comments for author File: 
Comments.pdf
Author Response
Response to Reviewer 3 Comments
We would like to thank reviewers for their appropriate comments and helpful suggestions that have been carefully considered. Majority of provided suggestions highlighted gaps in the text and were really useful to improve, we hope, paper quality. In point referees can find their comments, in response authors’ actions to reply/satisfy requests.
In particular, the synthesis of reviewers’ comments suggested a deep revision in paper organization and harmonization. Consequently, you will find some structural changes aimed at simplifying paper reading and make content more effective.
All comments were carefully evaluated and for the most of them corrections and integrations have been provided. Thank you so much for your work!
Point 1: Line 33-35 authors can support these statements of wide applicability of using GEE with the recent studies (https://doi.org/10.3390/rs14041004) to strengthen their Introduction and also broader the readers perspective.
Response 1: We totally agree with the reviewer and as suggested we have added (just moved because we have already considered this reference into the text) the reference to support and strengthen the statement into the text. Please see into the manuscript.
Point 2: Authors have not discussed about the selection of NDVI index. It would be better to provide the advantages and disadvantages of using this index. I have a big concern of using NDVI has several
drawbacks such as topographic illumination, shading effect, solar angle issues which has not been
discussed and elaborated. These aspects of NDVI has been mentioned and explained clearly in one
of the recent paper from which authors can benefit. I would highly recommend authors to include
this recent study to describe the selection. https://doi.org/130.3390/cli9070109.
Response 2: We totally agree with the reviewer and as suggested we have added the reference and deeply discussed the NDVI advantages and disadvantages in computing phenological metrics in alpine and more in general geomorphological context environments. Please see into the revised manuscript.
Point 2: Consider more up-to-date references and pointing out why your study is timely. In the
present version, the novelty is not clear enough.
Response 3: We totally agree with the reviewer and as suggested we have included more up-to-date references and deeply discussed the novelty of the work. Please see into the revised manuscript.
Point 4:. Due to time restrictions, I haven't had a chance to thoroughly examine the package itself, but I commend the authors' efforts in creating it and making it freely available to a larger audience. But there are a few issues I have that, if they were resolved in a good edit, would improve the article.
Even if the work is intriguing in and of itself, I occasionally think the authors pay (too) little attention to recent advancements in satellite-based phenology research, especially when talking about high-resolution images.
Response 4: Firstly, we would like to thank the reviewer. We are grateful for your positive comments. Concerning the higher resolution satellite development for the computation of phenological metrics we are more than aware of its important developments. However, our intent has been to develop an open-source code for free and open-source satellite data. Very higher resolution data is not currently available as open-source and is not available in cloud processing platforms such as Google Earth Engine except for Planetscope for USA and CONUS areas only. Certainly, it would be interesting to develop routines for these data as well when they will be made free and available in GEE or similar platforms.
Point 5: Authors did not discuss their findings of their algorithm with other existing methods such as
phenofit. Also please cite the work by Dong et al., 2022 (phenofit: An R package for extracting vegetation phenology from time series remote sensing)
Response 5: We totally agree with the reviewer and as suggested we have already included Kong and discussed phenofit. Please see into the revised manuscript.
Point 6: Recent research using multi-annual/time-series optical (and maybe SAR) data for vegetation
phenology evaluation, together with the newly developed package's functions, should be
discussed in the Discussion section.
Response 6: We totally agree with the reviewer and as suggested we have included recent research using multi-annual/time-series optical data for vegetation phenology evaluation into the Discussion section. Please see into the revised manuscript.
Point 7: Authors have missed to include the drawbacks of other satellite phenology products such as
AVHRR, VIIRS, Himawari, and Planetscope etc based indirect vegetation proxies. I encourage
and recommend the authors to incorporate a comprehensive detailed review related to the use of satellite-based remote sensing products in the estimation of vegetation growth. Authors may like to find studies in line of their statements to add the scientific weight in their observations. There is a vast literature on this topic.
Response 7: We totally agree with the reviewer and as suggested we have included satellite-based remote sensing products in the estimation of vegetation growth such as AVHRR, VIIRS, Himawari, and Planetscope into the introduction. Please see into the revised manuscript.
Point 8: Although MODIS can meet the demand of this study, but if we want to obtain more accurate results, the omission error will become one of the fatal defects. The ideal way to solve this problem is to combined use of remote sensing images with different time and spatial frequencies, such as Sentinel images with high spatial-temporal resolution launched in recent years with high time resolution. The combine use of Sentinel, Landsat and SPOT sensors can provide remote sensing database with high temporal and spatial resolution.
Response 8: We agree with the reviewer. However, we would like to underline how our study is not based on MODIS but Sentinel-2 and Landsat missions precisely for the reasons highlighted by the reviewer as well as for a greater spatial and temporal resolution. MODIS was adopted only to validate the metrics extracted from the other satellite missions. The validation as illustrated was also conducted using the same data in high resolution and deriving the metrics in R packages to evaluate the consistency of the algorithm and code created in Google Earth Engine.
Point 9: Please add a summary of the results, comparing them with the initial motivation of the study. Have you answered all the research questions described in the Introduction? If yes, how? If not, what are the next steps needed for answering them?
Response 9: We totally agree with the reviewer and as suggested we have included a summary of the results, comparing them with the initial motivation of the study. And in the discussion and conclusion we have answered the question arisen by the reviewer. Please see into the revised manuscript.
Round 2
Reviewer 1 Report
The authors have significantly improved the manuscript, even though the Discussion is not very exciting and shows only the positive sides of such research. Even though the study seems to give promising results, the authors should point out that studies using satellite images also have some serious limitations. One is the resolution of the images, which will not allow identification of early phenological phases that begin much earlier than a few decades ago, such as the swelling and bursting of leaf buds on trees. Limitations will also apply to identifying phenological phases in rare species. It is important to remember that individual species can respond differently to meteorological conditions, and their phenological phases do not necessarily correlate.
Stenseth, N. C., & Mysterud, A. (2002). Climate, changing phenology, and other life history traits: nonlinearity and match–mismatch to the environment. Proceedings of the National Academy of Sciences, 99(21), 13379-13381.
In addition, studies using satellite imagery are unable to determine the exact growing season of trees, especially ring-porous trees, in which some studies have shown that there is no clear relationship between the timing of the onset of wood formation and leaf development, e.g.:
Sass-Klaassen, U., Sabajo, C. R., & den Ouden, J. (2011). Vessel formation in relation to leaf phenology in pedunculate oak and European ash. Dendrochronologia, 29(3), 171-175.
Puchałka, R., Koprowski, M., Gričar, J., Przybylak, R., 2017. Does tree-ring formation follow leaf phenology in Pedunculate oak (Quercus robur L.)? Eur. J. For. Res. 136, 259–268. https://doi.org/10.1007/s10342-017-1026-7
Satellite methods also have limitations when studying the herbaceous vegetation of forests and lower layers of grassland vegetation. Here, traditional methods, relying on regular ground observations, remain irreplaceable. The growing prevalence of data from Citizen Science databases seems to offer considerable hope for supplementing such large-area studies, e.g:.
Puchałka, R., Klisz, M., Koniakin, S., Czortek, P., Dylewski, Ł., Paź-Dyderska, S., Vitkova, M., Sadlo, J., Rasomavicius, V., Carni, A., De Sanctis, M., Dyderski, M., 2022. Citizen science helps predictions of climate change impact on flowering phenology: A study on Anemone nemorosa. Agric. For. Meteorol. 325, 109133. https://doi.org/10.1016/j.agrformet.2022.109133
They make it possible to obtain information on phenology where satellites will not go. It is important to remember that satellite data allow for different results than ground-based observations. For a complete understanding of phenology, it would be beneficial to use different approaches that complement each other.
Author Response
Response to Reviewer 1 Comments
We would like to thank reviewers for their appropriate comments and helpful suggestions that have been carefully considered. Majority of provided suggestions highlighted gaps in the text and were really useful to improve, we hope, paper quality. In point referees can find their comments, in response authors’ actions to reply/satisfy requests.
In particular, the synthesis of reviewers’ comments suggested a deep revision in paper organization and harmonization. Consequently, you will find some structural changes aimed at simplifying paper reading and make content more effective.
All comments were carefully evaluated and for the most of them corrections and integrations have been provided. Thank you so much for your work!
Point 1: The authors have significantly improved the manuscript, even though the Discussion is not very exciting and shows only the positive sides of such research. Even though the study seems to give promising results, the authors should point out that studies using satellite images also have some serious limitations. One is the resolution of the images, which will not allow identification of early phenological phases that begin much earlier than a few decades ago, such as the swelling and bursting of leaf buds on trees. Limitations will also apply to identifying phenological phases in rare species. It is important to remember that individual species can respond differently to meteorological conditions, and their phenological phases do not necessarily correlate.
Stenseth, N. C., & Mysterud, A. (2002). Climate, changing phenology, and other life history traits: nonlinearity and match–mismatch to the environment. Proceedings of the National Academy of Sciences, 99(21), 13379-13381.
In addition, studies using satellite imagery are unable to determine the exact growing season of trees, especially ring-porous trees, in which some studies have shown that there is no clear relationship between the timing of the onset of wood formation and leaf development, e.g.:
Sass-Klaassen, U., Sabajo, C. R., & den Ouden, J. (2011). Vessel formation in relation to leaf phenology in pedunculate oak and European ash. Dendrochronologia, 29(3), 171-175.
Puchałka, R., Koprowski, M., Gričar, J., Przybylak, R., 2017. Does tree-ring formation follow leaf phenology in Pedunculate oak (Quercus robur L.)? Eur. J. For. Res. 136, 259–268. https://doi.org/10.1007/s10342-017-1026-7
Satellite methods also have limitations when studying the herbaceous vegetation of forests and lower layers of grassland vegetation. Here, traditional methods, relying on regular ground observations, remain irreplaceable. The growing prevalence of data from Citizen Science databases seems to offer considerable hope for supplementing such large-area studies, e.g:.
Puchałka, R., Klisz, M., Koniakin, S., Czortek, P., Dylewski, Ł., Paź-Dyderska, S., Vitkova, M., Sadlo, J., Rasomavicius, V., Carni, A., De Sanctis, M., Dyderski, M., 2022. Citizen science helps predictions of climate change impact on flowering phenology: A study on Anemone nemorosa. Agric. For. Meteorol. 325, 109133. https://doi.org/10.1016/j.agrformet.2022.109133
They make it possible to obtain information on phenology where satellites will not go. It is important to remember that satellite data allow for different results than ground-based observations. For a complete understanding of phenology, it would be beneficial to use different approaches that complement each other.
Response 1: Firstly, we would like the reviewer for his/her valuable comments. We agree with the suggestion given and included also the limiting factor of Phenology detection using remote sensing in discussion section including all the reference suggested. Please see into the manuscript the revisions performed.
Reviewer 2 Report
This manuscript can be accepted.
Author Response
Response to Reviewer 2 Comments
We would like to thank reviewers for their appropriate comments and helpful suggestions that have been carefully considered. Majority of provided suggestions highlighted gaps in the text and were really useful to improve, we hope, paper quality. In point referees can find their comments, in response authors’ actions to reply/satisfy requests.
In particular, the synthesis of reviewers’ comments suggested a deep revision in paper organization and harmonization. Consequently, you will find some structural changes aimed at simplifying paper reading and make content more effective.
All comments were carefully evaluated and for the most of them corrections and integrations have been provided. Thank you so much for your work!
Point 1: This manuscript can be accepted.
Response 1: Firstly, we would like to thank the reviewer, we appreciate that he/she approve our manuscript.
Reviewer 3 Report
Accept in present form
Author Response
Response to Reviewer 3 Comments
We would like to thank reviewers for their appropriate comments and helpful suggestions that have been carefully considered. Majority of provided suggestions highlighted gaps in the text and were really useful to improve, we hope, paper quality. In point referees can find their comments, in response authors’ actions to reply/satisfy requests.
In particular, the synthesis of reviewers’ comments suggested a deep revision in paper organization and harmonization. Consequently, you will find some structural changes aimed at simplifying paper reading and make content more effective.
All comments were carefully evaluated and for the most of them corrections and integrations have been provided. Thank you so much for your work!
Point 1: Accept in present form
Response 1: Firstly, we would like to thank the reviewer, we appreciate that he/she approve our manuscript.
Round 3
Reviewer 1 Report
Currently, the manuscript requires only minor but necessary corrections:
L.512-519:
Moreover, studies using satellite imagery in some cases seem to be 512 unable to determine the exact growing season of trees, especially ring-porous trees, in which some researches have shown that there is no clear relationship between the timing of the onset of wood formation and leaf development. [Puchałka et al 2017; Sass-Klaassen et al. 2011]. Despite of all, EO data make possible to obtain information on phenology worldwide. Therefore for a complete understanding of phenology, it would be beneficial to use different approaches that complement each other and the code developed can be one of this to support ground studies and help also to rise the database from the traditional and citizen-science ground observation [Puchałka et al 2022].
L.2459 and L.2464: Pucha\lka ->Puchałka
All Appendixes should be placed in a separate file, outside the manuscript or after Literature references.
Author Response
Response to Reviewer 1 Comments
We would like to thank reviewers for their appropriate comments and helpful suggestions that have been carefully considered. Majority of provided suggestions highlighted gaps in the text and were really useful to improve, we hope, paper quality. In point referees can find their comments, in response authors’ actions to reply/satisfy requests.
In particular, the synthesis of reviewers’ comments suggested a deep revision in paper organization and harmonization. Consequently, you will find some structural changes aimed at simplifying paper reading and make content more effective.
All comments were carefully evaluated and for the most of them corrections and integrations have been provided. Thank you so much for your work!
Point 1: Currently, the manuscript requires only minor but necessary corrections:
L.512-519:
Moreover, studies using satellite imagery in some cases seem to be 512 unable to determine the exact growing season of trees, especially ring-porous trees, in which some researches have shown that there is no clear relationship between the timing of the onset of wood formation and leaf development. [Puchałka et al 2017; Sass-Klaassen et al. 2011]. Despite of all, EO data make possible to obtain information on phenology worldwide. Therefore for a complete understanding of phenology, it would be beneficial to use different approaches that complement each other and the code developed can be one of this to support ground studies and help also to rise the database from the traditional and citizen-science ground observation [Puchałka et al 2022].
L.2459 and L.2464: Pucha\lka ->Puchałka
All Appendixes should be placed in a separate file, outside the manuscript or after Literature references.
Response 1: Firstly, we would like the reviewer for his/her valuable comments. We agree with the suggestion given and performed correction. Concerning on the appendix this is the MDPI Geomatics structure and I cannot change as explained here: https://www.mdpi.com/journal/geomatics/instructions .
