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Open AccessArticle
Peer-Review Record

Evaluation of Normalized Difference Water Index as a Tool for Monitoring Pasture Seasonal and Inter-Annual Variability in a Mediterranean Agro-Silvo-Pastoral System

Water 2019, 11(1), 62; https://doi.org/10.3390/w11010062
Reviewer 1: Anonymous
Reviewer 2: Anonymous
Reviewer 3: Anonymous
Water 2019, 11(1), 62; https://doi.org/10.3390/w11010062
Received: 31 October 2018 / Revised: 20 December 2018 / Accepted: 25 December 2018 / Published: 1 January 2019
(This article belongs to the Special Issue Water Management Using Drones and Satellites in Agriculture)

Round  1

Reviewer 1 Report

Manuscript is of great interest to Water readers, in relation to use Satellite data to build index to pasture management in arid and semi-arid regions. 

However, this manuscript is a second part of previous manuscript published in this Special Issue. I suggest introduce in the title: Part 2: XXXX, and delete some redundant paragraphs, including reference to publish paper.

Moreover, authors should explain more detailed information about the use of Sentinel data, due to some band use to determine NDWI is only at 20x20m grid. This aspect must be incorporated and clarified previous to final publication.

In general, manuscript is well structured and written, except that the introduction is too long. In addition, in the section of methods, an aspect must be clarified regarding the methods of analysis used (pasture determinations), as well as what images have been used?. In this last aspect, the authors could include a supplementary table in which to show all the dates that have been studied to obtain satellite images, indicating the percentage of cloudiness that has led to discard them.

The revised manuscript is attached, which includes comments that the authors must respond and modify prior to the final acceptance of the work.

Comments for author File: Comments.pdf

Author Response

Special Issue "Water Management Using Drones and Satellites in Agriculture"

Water-389820

___________________________________________________

 Reviewer 1- Comments and Suggestions for Authors

Manuscript is of great interest to Water readers, in relation to use Satellite data to build index to pasture management in arid and semi-arid regions. 

R: Thank you very much for your comments, suggestions and corrections.

-However, this manuscript is a second part of previous manuscript published in this Special Issue. I suggest introduce in the title: Part 2: XXXX, and delete some redundant paragraphs, including reference to publish paper.

R: Thank you for the suggestion. Unfortunately, since the other article is already published, and the title does not include "Part I", it will not be possible to present the two articles as two parts of a single article.

In any case, if the Editors feel that this change can be made, we are more than willing to make the necessary changes to the two manuscripts.

-Moreover, authors should explain more detailed information about the use of Sentinel data, due to some band use to determine NDWI is only at 20x20m grid. This aspect must be incorporated and clarified previous to final publication.

R: This is a very valid suggestion, thank you. The manuscript was corrected accordingly.

NDVI (bands B4 and B8; grid - 10 m x 10 m)

NDWI (bands B8A and B11; grid 20 m x 20 m).

-In general, manuscript is well structured and written, except that the introduction is too long. In addition, in the section of methods, an aspect must be clarified regarding the methods of analysis used (pasture determinations), as well as what images have been used? In this last aspect, the authors could include a supplementary table in which to show all the dates that have been studied to obtain satellite images, indicating the percentage of cloudiness that has led to discard them.

R: One reference to “Official Methods of Analysis” was introduced in the manuscript. Table 3 indicates the days of the year (DOY) where the NDWI and NDVI indexes were captured. The sentence “Only the images without presence of clouds were used in the analysis” was introduced in the manuscript.

-The revised manuscript is attached, which includes comments that the authors must respond and modify prior to the final acceptance of the work.

R: Thank you very much for your comments, suggestions and corrections.
Responses to the Reviewer 1 annotations in PDF (peer-review-3347040.v2.pdf):

-These words: montado and dehesa must be between ' '.

R: Accepted.

- Should include study years and number of days with Satellite images in the abstract.

R: The reviewer’s suggestion was accepted (study years and number of days with images were included in the abstract).

-You need define it, first time (PMC, Tir, PQDI).

R: The reviewer’s suggestion was accepted.

-Delete. It is include in Title. (Keywords: NDWI)

R: Accepted.

-Changes by SMC.

R: Accepted.

-Not defined previously. Define it (CP, NDF).

R: The reviewer’s suggestion was accepted.

-Authors should explain which bands from Sentinel-2 were used. Accepted.

R: Accepted, bands were included:

NDVI (bands B4 and B8; grid - 10 m x 10 m)

NDWI (bands B8A and B11; grid 20 m x 20 m).

-These sentences are incoherents, check it.

R: These sentences were checked and corrected. Thank you.

-Include here the study years.

R: The reviewer’s suggestion was accepted (between September 2015 and June 2018).

-(Originally Figure 2; now Figure 3)

Axis Y refer to temperature, not to Daily mean temperature. Modify it.

Review colour in legends.

R: The “Y” values presented are the 24 hour average of air temperature measured every 15 minutes. Thus, the hourly fluctuations of the temperature during the day have been smoothed out, and only the average daily value used in the graph. Thus these values are actually daily mean temperatures.

-(Originally Figure 3)

Delete it. It is not relevant here.

R: The reviewer’s suggestion was accepted.

-You must refer to solar time, to avoid difference conditions between summer and Winter. (9 a.m.)

R: Authors not understand this question. The referee wants the time for each image pass? Authors used an index (NDWI) calculated with a ratio between two spectral bands and with the same theoretical limits interval in the summer time and in the winter time. Both bands are affected by the same conditions independently of the time of the year.

-(Originally Figure 4)

Delete it. It is not relevant here.

R: The reviewer’s suggestion was accepted.

-How many samples have you got?

12 points x 3 years x 4 samples date per year = 108 samples in total

R: 12 points x 4 sample dates in 2016 (March, April, May and June) = 48 samples (2016)

12 points x 5 sample dates in 2017 and 2018 (February, March, April, May and June) = 120 samples (2017 and 2018).

The text “In total, 168 pasture samples were collected (48 in 2016, 60 in 2017 and 60 in 2018)” was introduced.

-A reference of method is necessary here, or an explanation about it.

R: One reference to “Official Methods of Analysis” was introduced in the manuscript.

-These bands are referred to 20x20m. Please clarify it.

https://sentinel.esa.int/web/sentinel/user-guides/sentinel-2-msi/resolutions/spatial

R: The reviewer’s suggestion was accepted.

-What percentage of Clouds was used?

R: Only the images without presence of clouds were used in the analysis. This sentence was introduced in the manuscript.

-(Originally Figure 5; now Figure 1)

This figure must be introduced in first paragraph of Section 2.

R: The reviewer’s suggestion was accepted.

-These sentences are not necessary here. First expose results, then discuss.

R: The reviewer’s suggestion was accepted.

-Check decimal separator and thousands (Table 2)

R: Table 2 was checked and corrected. Thank you.

-Check format to Months: Italic or not (Table 2)

R: Not italic. The format was corrected. Thank you.

-(Originally Figure 7; now Figure 5)

Check format

The Figure was checked. Thank you.

You need explain what is the meaning of error bar (Originally Figures 7, 10 and 12; now Figures 5, 8 and 10)

The error bars have been removed from the figures.

This figure (Originally Figure 7b; now Figure 5b) is not cited in the manuscript. Delete it or introduce in the manuscript.

It was erroneously quoted as Figure 8b (lines 381 and 390) In the text, but it is Figure 7b (now Figure 5b). The text was corrected. Thank you.

-(Originally Figure 8; now Figure 6)

Delete this text. Number is not visible. Check it.

R: Figure was checked. Thank you.

-Figure 7, not 8.

The reviewer is right. The text was corrected. Thank you.

-Idem previous comment.

The reviewer is right. The text was corrected. Thank you.

-Delete it. (Lines 394-397).

R: Accepted.

-Check format (Originally Figure 9; now Figure 7- Equation)

R: The authors did not understand this question. It seems that the format is correct.

-You need add a comment in relation to dispersion to positive values of NDWI. What had happened?

R: Authors not understand this question.

-(Originally Figure 12; now Figure 10)

What values had you used? Monthly average or central date per month? It is necessary an explanation about it.

R: Were used average monthly values. The text was clarified accordingly.

-What parameters?

R: The text was clarified. The parameters (NDWI, PMC and PQDI) were incorporate.

-(Originally Figure 15)

-This figure should moved to Graphical abstract, if it is possible, or as figure to appear in relation to manuscript. 

R: Suggestion accepted. This figure has been converted to Graphic abstract.

- (References)

There are two references here (lines 561-563)? Review it, and re-number if it is necessary.

R: The error was corrected. Thank you.

Author Response File: Author Response.pdf

Reviewer 2 Report

The authors had performed a large number of experiments during three years of research. They had found that satellite-derived normalized difference water index can be used for managing   agronomic practices.

A lot of abbreviations are used in the abstract and introduction. This is the reason why the introduction is quite unclear. For example, the abbreviations CP and NDF (line 110) are explained only on line 245.   

It is not clear if authors used moisture content wet basis or moisture content dry basis. It has to be explained. On line 71, author also mentioned volumetric soil moisture. The use of the term “humidity” (line 61) is incorrect in this case, because this term is used for gases e.g. for air.

The text on the lines from 204 to 230 is the same as on the lines 175 – 178 and 182 – 204.

Manuscript contains formal errors (highlighted in the text).

Line 2 – it is unusual to put an unexplained abbreviation in the title.

Lines 168, 170, 172, 173, 237, 242, 363, … – between value and physical unit have to be a free space.

Line 242 – the word “weight” is commonly used, but according to my opinion correct will be “mass”.

Lines 21, 242, 253, 260, 263, 279, in Table 1, 287, 290, 305, 308, 312, 313, 441, 442, 443, 445,452, 453, 464, …  – symbol for quantities in the text should be in italics.

Lines 23, 24, 109, 159, 181, 265, 287, 305, 314, 324, 328, 335, 385, 416, 430, 439, 480, 482, 496, and in the Tables – around the signs =; -; <;>; x; ± have to be free spaces.

Comments for author File: Comments.pdf

Author Response

Special Issue "Water Management Using Drones and Satellites in Agriculture"

Water-389820

___________________________________________________

Reviewer 2- Comments and Suggestions for Authors

R: Thank you very much for your comments, suggestions and corrections.

The authors had performed a large number of experiments during three years of research. They had found that satellite-derived normalized difference water index can be used for managing   agronomic practices.

-A lot of abbreviations are used in the abstract and introduction. This is the reason why the introduction is quite unclear. For example, the abbreviations CP and NDF (line 110) are explained only on line 245.   

R: The reviewer is correct. All abbreviations are now explained when they are first presented.

-It is not clear if authors used moisture content wet basis or moisture content dry basis. It has to be explained. On line 71, author also mentioned volumetric soil moisture.

R: The TDR measures soil volumetric content. Thus, the value is the volume of water in a given volume of soil, given in percentage. Therefore, it is based on the total bulk volume of the soil, and thus it is not relevant to indicate if it is wet or dry basis, since the bulk volume is not affected.

-The use of the term “humidity” (line 61) is incorrect in this case, because this term is used for gases e.g. for air.

R: The reviewer is right and the term was changed accordingly.

- The text on the lines from 204 to 230 is the same as on the lines 175 – 178 and 182 – 204.

R: The text was corrected. Thank you.

Manuscript contains formal errors

(highlighted in the text: annotations in PDF -peer-review-3348705.v2.pdf)

R: The suggestion was accepted. The text was checked according to the reviewer’s suggestions.

-Line 2 – it is unusual to put an unexplained abbreviation in the title.

R: The reviewer is right and the title was changed accordingly.

- Lines 168, 170, 172, 173, 237, 242, 363, … – between value and physical unit have to be a free space.

R: The suggestion was accepted. The text was checked accordingly.

-Line 242 – the word “weight” is commonly used, but according to my opinion correct will be “mass”.

R: The reviewer is right (term “mass” is now used instead of “weight”).

-Lines 21, 242, 253, 260, 263, 279, in Table 1, 287, 290, 305, 308, 312, 313, 441, 442, 443, 445,452, 453, 464, …  – symbol for quantities in the text should be in italics.

R: The suggestion was accepted. The text was checked accordingly.

-Lines 23, 24, 109, 159, 181, 265, 287, 305, 314, 324, 328, 335, 385, 416, 430, 439, 480, 482, 496, and in the Tables – around the signs =; -; <;>; x; ± have to be free spaces.

R: The suggestion was accepted. The text was checked accordingly.
 

Author Response File: Author Response.pdf

Reviewer 3 Report


The introduction explained clearly the background, the literature review is more concentrated on the existing methods to evaluate soil moisture, vegetation state... it gives information on the advantages and inconvenience of the methods. I feel that a paragraph synthesizing a literature review of what is done in the Mediterranean pasture (or sparse crops, or tree and shrubs systems or heterogeneous systems...) is an important addition. Also, providing the value of the study and indicating the gaps and need is essential. Finally, after the objective, a specific statement providing the structure of the paper will be helpful.

The materials and methods part is globally well explained. I suggest to add the overall observations date in the end of this part to complete the information in figure 5.

Results and discussion, I suggest that the authors rewrite this section, by first presenting the findings, then explaining results and finally discuss the results.  

it is important to compare the dates of measurements of water content and rainfall events. 

it is important to compare the pasture surface temperature with the air temperature. 

Same informations are presented in table 2 and figure 7 regarding biomass and PGDI, I suggest that all parameters of table 2 will be presented as figure. 

it is difficult for the lecture to compare figure 7 with figure 8 as suggested in lines 332-334.  It is easier for the lecture to compare two figures when they are superposed or at least have the same scale and nomenclature for x-axis (dates in this case). 

I suggest that table 3 will be presented as figure

For the title, it is important to show that it is an agro-sylvo-pastoral system

Minor revision:

line 83: replace lead to draught by lead to drought 

line 175 : figure 2 shows the average thermo-pluviometric diagram ; I suggest to replace average by daily replace 

lines 204 to 230 must be deleted,  is a repetition of the previous paragraphs 

lines 274-278: General issues, not to be invoked here in the result part.


Author Response

Special Issue "Water Management Using Drones and Satellites in Agriculture"

Water-389820

___________________________________________________

Reviewer 3- Comments and Suggestions for Authors
R: Thank you very much for your comments, suggestions and corrections.

The introduction explained clearly the background, the literature review is more concentrated on the existing methods to evaluate soil moisture, vegetation state... it gives information on the advantages and inconvenience of the methods.

-I feel that a paragraph synthesizing a literature review of what is done in the Mediterranean pasture (or sparse crops, or tree and shrubs systems or heterogeneous systems...) is an important addition. Also, providing the value of the study and indicating the gaps and need is essential. Finally, after the objective, a specific statement providing the structure of the paper will be helpful. 

R: Thank you for the valuable suggestions. The first part of the introduction was changed to include more information on what is done in Mediterranean pasture. Regarding “…the value of the study, gaps and needs”, this is elaborated in the conclusions of the manuscript. The structure of the paper was previously defined by the journal.

-The materials and methods part is globally well explained. I suggest to add the overall observations date in the end of this part to complete the information in figure 5.

R: The suggestion was accepted: the overall observations date (September 2015 – June 2018) was included in the Material and Methods section.

-Results and discussion, I suggest that the authors rewrite this section, by first presenting the findings, then explaining results and finally discuss the results. 

R: This comment is in agreement within the suggestions of reviewer 1 and 2 to remove the generalist paragraphs that precede the presentation of results ("... first expose results, then discuss.") which were considered unnecessary. The suggestion was accepted and these paragraphs were removed.

-It is important to compare the dates of measurements of water content and rainfall events. 

-It is important to compare the pasture surface temperature with the air temperature. 

R: These two proposals from reviewer 3 will be interesting for an article that the authors are preparing to analyze the behavior of two relevant variables in pasture productivity in “montado” ecosystem: soil moisture content and pasture surface temperature (and how they reflects rainfall events, but also: sun exposure, air temperature, relief, proximity to trees, etc.). However, we believe that this proposal goes beyond the scope of this article (“…to evaluate NDWI based on Sentinel-2 imagery as a tool for monitoring pasture seasonal dynamics and inter-annual variability in a Mediterranean agro-silvo-pastoral system”) which is related to the application of PA tools to monitor the variability, rather than the origin of this variability.

-Same informations are presented in table 2 and figure 7 regarding biomass and PDQI, I suggest that all parameters of table 2 will be presented as figure. 

Table 2 presents five parameters: Biomass, PMC, CP, NDF and PQDI. Biomass and PQDI are presented in Figure 7 (now Figure 5). PMC is presented in Figure 12 (now Figure 10). The authors decided not to place the CP and NDF parameters in graphic form because the PQDI integrates both (PQDI=NDF/CP). These parameters are strongly correlated with NDVI, a topic addressed in the paper already published in this Special Issue of the Water journal (“Monitoring Seasonal Pasture Quality Degradation in the Mediterranean Montado Ecosystem: Proximal versus Remote Sensing”).

-It is difficult for the lecture to compare figure 7 with figure 8 as suggested in lines 332-334.  It is easier for the lecture to compare two figures when they are superposed or at least have the same scale and nomenclature for x-axis (dates in this case).  

R: With this reference in the text (“As expected in dryland pastures, this evolution reflects the effect of rainfall distribution (Figure 8, (a) and (b)).”) the intention is not for the readers to compare and directly overlap of the two figures (now Figures 5 and 6), but to be able to carry out and overall interpretation of both. To perform this objective, the following text was included in the manuscript: “It is evident that the most productive spring (2016) was one in which rainfall was evenly distributed in autumn, winter and spring (2015/2016).”

-I suggest that table 3 will be presented as figure.

Table 3 presents two parameters: NDVI and NDWI.

As this paper is focused on the NDWI, this parameter, obtained between January 2017 and June 2018, is presented in Figure 10 (now Figure 8, with Tir and SMC). NDWI obtained in the spring of 2016, 2017 and 2018 is presented in Figure 12 (now Figure 10, with PMC).

NDVI is presented only in Table 3 because this was the topic addressed in a paper already published in this Special Issue of the Water journal (“Monitoring Seasonal Pasture Quality Degradation in the Mediterranean Montado Ecosystem: Proximal versus Remote Sensing”).

Nevertheless, the relationship between NDVI/NDWI is presented (now Figure 7).

-For the title, it is important to show that it is an agro-sylvo-pastoral system

R: Accepted. The title was changed accordingly.

“Evaluation of Normalized Difference Water Index as a tool for monitoring pasture seasonal and inter-annual variability in a Mediterranean agro-silvo-pastoral system

-Minor revision: 

 line 83: replace lead to draught by lead to drought 

R: Accepted.

-line 175 : “Figure 2 shows the average thermo-pluviometric diagram…” ; I suggest to replace average by daily 

R: Accepted.

-lines 204 to 230 must be deleted, is a repetition of the previous paragraphs 

R: The reviewer is right. The text was deleted. Thank you.

-lines 274-278: General issues, not to be invoked here in the result part

R: The reviewer is right. The text was deleted. Thank you.


Author Response File: Author Response.pdf

Round  2

Reviewer 3 Report

Thank you for taking into account the main remarks.

 Best regards

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