Remote Sensing Phenology of the Brazilian Caatinga and Its Environmental Drivers

Round 1

Reviewer 1 Report

This study was based on the two objectives: (i) estimate phenological parameters using an Enhanced Vegetation Index (EVI) time-series over 20 years (2000-2019), and (ii) characterize the relationship between phenologic dynamics and environmental drivers. The TIMESAT software was used to determine four phenological parameters: Start Of Season (SOS), End Of Season (EOS), Length Of Season (LOS), and Amplitude (AMPL). Relationships between phenologic dynamics and environmental drivers (air temperature, precipitation, soil moisture, and water deficit) were defined by boxplots and Pearson's correlation coefficient. The paper has several good ideas and has a good potentiality, However, there are some problems in the data, content, structure, conclusion and international significance. It needs to be overhauled before it can be considered for acceptance.

• Using the TIMSET software to fit phonological changes in the study area, the accuracy of extracted phonological features met the requirements. As we know, the study area has the rich species composition, the change of EVI value was also complicated. In addition, the author used the TIMESAT software , a seasonality parameter per year was chosen, representing a phenological cycle with a start and end level of 20%, no reason given.
• The lag effect of environmental factors on vegetation phenology was not considered.
• The cross-influence of environment factors was not analyzed. I suggested the authors join this part of the study, which will make the results more interesting.

Author Response

Thank you very much for the positive feedback and useful suggestions. We agree with your point of view and the three suggestions to improve our methodology and analysis of results. 1- We chose to use 20% of the EVI amplitude due to this parameterization's efficiency in the works for dry seasonal forests and other land covers Doussoulin-Guzmán et al., 2022; Streher et al., 2017; Diem et al., 2016. 2 - We included a step to analyse the lag period between vegetation dynamics and environmental drivers. Pearson's correlation is fundamental to selecting lags for each environmental driver. 3 - We followed your suggestion to include cross-influence, and this analysis allowed a more clear definition of the behavior of each environmental driver.

Doussoulin-Guzmán, M.-A., Pérez-Porras, F.-J., Triviño-Tarradas, P., Ríos-Mesa, A.-F., García-Ferrer Porras, A., & Mesas-Carrascosa, F.-J. (2022). Grassland Phenology Response to Climate Conditions in Biobio, Chile from 2001 to 2020. Remote Sensing, 14(3), 475. https://doi.org/10.3390/rs14030475.

Streher, A. S., Sobreiro, J. F. F., Morellato, L. P. C., & Silva, T. S. F. (2017). Land Surface Phenology in the Tropics: The Role of Climate and Topography in a Snow-Free Mountain. Ecosystems, 20(8), 1436–1453. https://doi.org/10.1007/s10021-017-0123-2.

Diem, P., Pimple, U., Sitthi, A., Varnakovida, P., Tanaka, K., Pungkul, S., … Chidthaisong, A. (2018). Shifts in Growing Season of Tropical Deciduous Forests as Driven by El Niño and La Niña during 2001–2016. Forests, 9(8), 448. https://doi.org/10.3390/f9080448.

 

Reviewer 2 Report

Title: Remote Sensing Phenology of the Brazilian Caatinga and Its Environmental Drivers

Authors: R. Medeiros, J. Andrade, D. Ramos, M. Moura, A. Pérez-Marin, C. Santos, B. Silva, J. Cunha

The exploration of phenology is very important since it allows one to detect changes in the biosphere that occur under the influence of natural and anthropogenic factors affecting the environmental conditions. The peer-reviewed paper, in my opinion, is quite relevant, since the authors have set themselves quite complex, but at the same time very important and timely problems, namely: (a) to assess four phenological parameters by analysing 20-yr time-series of the Enhanced Vegetation Index (EVI), and (b) to characterize the relation between dynamics of phonological parameters and environmental drivers. The authors, in my opinion, successfully solved the problems set. The paper is also of practical importance, since the results obtained can be used to compare future changes in the Caating phenology caused by natural or anthropogenic causes.

However, I cannot recommend this version of the article for publication, since it needs to be updated. Since the readers of the Remote Sensing journal are specialists from many branches of science, some of the specific terms used in the text of the article (e.g. "Phenology”, “Neotropics”) should be defined. Then abbreviation “LSP” (line 82) also should be defined.

In their studies, the authors use the results of satellite measurements. At the same time, nothing is said which satellites supply this information, what is the accuracy of the satellite data? What methods, in addition to those considered in the article, can be used to solve the main problem of the study? Some justification of the approaches and methods used by the authors is required. Justification of the chosen environmental parameters is also required. Why only these parameters were chosen?

The authors claim that results obtained can be useful in the context of climate change. However, they do not say anything about how climate change will affect the environmental parameters in the geographical region under consideration.

Questions are also caused by the use of linear regression to approximate the dependencies between the EVI and environmental parameters. If you look, for example, at the figures 7 and 8, you can see an extremely large scatter of data relative to the regression line.

References must be adopted in accordance with MDPI requirements (numbering in brackets […]).

Line 51 not “dependended” but “dependent”.

Delete dots before “MATERIAL AND METHODS” (line 128), “RESULTS” (line 238)

 

Author Response

The exploration of phenology is very important since it allows one to detect changes in the biosphere that occur under the influence of natural and anthropogenic factors affecting the environmental conditions. The peer-reviewed paper, in my opinion, is quite relevant, since the authors have set themselves quite complex, but at the same time very important and timely problems, namely: (a) to assess four phenological parameters by analysing 20-yr time-series
of the Enhanced Vegetation Index (EVI), and (b) to characterize the relation between dynamics of phonological parameters and environmental drivers. The authors, in my opinion, successfully solved the problems set. The paper is also of practical importance, since the results obtained can be used to compare future changes in the Caatinga phenology caused by natural or anthropogenic causes.

However, I cannot recommend this version of the article for publication, since it needs to be updated. Since the readers of the Remote Sensing journal are specialists from many branches of science, some of the specific terms used in the text of the article (e.g. "Phenology”, “Neotropics”) should be defined.

Answer: Done.

Then abbreviation “LSP” (line 82) also should be defined.

Answer: Done.

In their studies, the authors use the results of satellite measurements. At the same time, nothing is said which satellites supply this information, what is the accuracy of the satellite data? What methods, in addition to those considered in the article, can be used to solve the main problem of the study? Some justification of the approaches and methods used by the authors is required.

Answer: We understand the reviewer and believe that some of these important issues are already addressed directly or indirectly in our manuscript. Near-surface phenology (phenocams) would be the alternative methodological path to this manuscript's proposed methodological approach, but to avoid confounding the reader, we chose not to include comments on methodological options. Thus, we made it more evident that the purpose of this manuscript is to work with data exclusively obtained remotely, as in most of the LSP studies. Therefore, the main information required in this study is a time series of vegetation index, which several remote sensors can get. As the choice depends a lot on the specificity of each
environment, we chose to present the main studies that deal with the theme.

Justification of the chosen environmental parameters is also required. Why only these parameters were chosen?

Answer: We chose these parameters because they are the main environmental drivers for the leafing patterns of plants from seasonally dry tropical ecosystems. We have now included the justification for its choice in the introduction (Lines 73-76).

The authors claim that results obtained can be useful in the context of climate change. However, they do not say anything about how climate change will affect the environmental parameters in the geographical region under consideration.

Answer: We agree with the reviewer on the importance of highlighting how climate change will affect the cues for phenology in the geographical region of study. We have now included in the introduction (Lines 76-87) statements regarding the forecast on the increases in the air temperature presented in the recent IPCC 2O22 and how it may affect the distribution of rainfall in the Northeast Region of Brazil.

Questions are also caused by the use of linear regression to approximate the dependencies between the EVI and environmental parameters. If you look, for example, at the figures 7 and 8, you can see an extremely large scatter of data relative to the regression line.

Answer: We agreed with the reviewer and included partial correlation analysis, as we have already commented to the editor and reviewer #1.

References must be adopted in accordance with MDPI requirements (numbering in brackets […]).

Answer: Done.

Line 51 not “dependended” but “dependent”.

Answer: Done.

Delete dots before “MATERIAL AND METHODS” (line 128), “RESULTS” (line 238)

Answer: Done.

Reviewer 3 Report

This is a very competent manuscript.  It is well written and presented.  There is a clear statement of intent and a logical flow and organization to the text.  The tables and figures are professional and informative.  There is an extensive set of appropriate references

The topic of phenology and the use of remote sensing to document and monitor phenology is a topic of importance and will be of interest to other scientists.  The availability of an extensive archive of spaceborne remote sensing data at frequent temporal intervals allows this type of analysis.  The authors of this study examined 20 years of data for three sites using established research methods.  Multiple sites is an important research procedure.  This effort may provide a model for similar studies in other locations including as the authors note how phenology is changing over time.

As in almost all manuscripts, there are editorial suggestions for consideration by the authors, several of which follow:

1. Line 31, dependended?
2. There is no apparent order in multiple citations. Typically by year or alphabetically.  Of course, importance would not have an obvious order but is not common.
3. It is a changing trend in scientific text but use of pronouns (we, our, us) are not comfortable for all members of the scientific community.
4. It seems inconsistent but perhaps journal policy to have author names in upper case in citations. There also seems to be inconsistencies in using et al. in references.  There appear to be some citations where et al. is not needed, typically up to three authors are listed but that is a specific journal policy.
5. Line 59, LPS, correct?
6. Line 111, Cerrado, Albertaon et al. Correct?
7. Lines 128 and 238, correct heading spacing.
8. Line 152, coordinates are.
9. Line 166, 3 and 7 m?
10. Line 187, BSh.
11. Line 193, meters (m)?
12. Line 361, VEIGA?
13. The font and spacing of the references does not seem appropriate. There is some inconsistency in the format of the references with article titles being in both upper and lower case for example.

As stated, this is an excellent manuscript and an appropriate topic and approach for the special issue of this journal.

Author Response

This is a very competent manuscript. It is well written and presented. There is a clear
statement of intent and a logical flow and organization to the text. The tables and figures are professional and informative. There is an extensive set of appropriate references.

The topic of phenology and the use of remote sensing to document and monitor phenology is a topic of importance and will be of interest to other scientists. The availability of an extensive archive of spaceborne remote sensing data at frequent temporal intervals allows this type of analysis. The authors of this study examined 20 years of data for three sites using established research methods. Multiple sites is an important research procedure. This effort may provide a model for similar studies in other locations including as the authors note how phenology is changing over time.

As in almost all manuscripts, there are editorial suggestions for consideration by the authors, several of which follow:
1. Line 31, dependended?

Answer: We substitute by dependent.
2. There is no apparent order in multiple citations. Typically by year or alphabetically. Of course, importance would not have an obvious order but is not common.
Answer: In the Remote Sensing order, citations should define the latest version, shown only by number order.
3. It is a changing trend in scientific text but use of pronouns (we, our, us) are not
comfortable for all members of the scientific community.
Answer: We agreed with the reviewer and adjusted the manuscript's text to remove personal pronouns.

4. It seems inconsistent but perhaps journal policy to have author names in upper case in citations. There also seems to be inconsistencies in using et al. in references. There appear to be some citations where et al. is not needed, typically up to three authors are listed but that is a specific journal policy.
Answer: In the publication version, the citations are identified by numbers of order. There is no formation defined for the version submitted.

5. Line 59, LPS, correct?
Answer: It is not correct, and it should be Land Surface Phenology (LSP).
6. Line 111, Cerrado, Albertaon et al. Correct?
Answer: We adjusted the sentence, and the correct form is Alberton. We verified all text to ensure correct orthography.
7. Lines 128 and 238, correct heading spacing.
Answer: Yes. We adjusted all heading spacings.

8. Line 152, coordinates are.
Answer: Done.
9. Line 166, 3 and 7 m?
Answer: Yes. We standardised the presentation of numbers.
10. Line 187, BSh.
Answer: Yes.
11. Line 193, meters (m)?
Answer: We removed (m).
12. Line 361, VEIGA?
Answer: Yes. We set it to upper letters.

13. The font and spacing of the references does not seem appropriate. There is
some inconsistency in the format of the references with article titles being in both upper and lower case for example.
Answer: We thank the reviewer for identifying several adjustments in the text. The whole text was reviewed.
As stated, this is an excellent manuscript and an appropriate topic and approach for the special issue of this journal.

Round 2

Reviewer 1 Report

This paper can be seen that the author has made serious revised and can reach the acceptance level. 

Author Response

thank you

Reviewer 2 Report

Have no comments.

Author Response

thank you