The Multiple Perspective Response of Vegetation to Drought on the Qinghai-Tibetan Plateau

Round 1

Reviewer 1 Report

Manuscript, entitled (The multiple perspective response of vegetation to drought on the Qinghai-Tibetan Plateau) reported that Drought has significant temporal effects on vegetation in grassland areas of the QTP during the growing seasons, which reach their peak in July andAugust. The 0-1 month and 3-month time scales were the optimal lagged and accumulated time during the growing season, respectively. The stability of vegetation response to drought showed significant spatial heterogeneity and varied with eco-geographical regions and vegetation types. Generally, forest areas showed high resistance and resilience, followed by crop and grassland areas. There are several shortcomings that should be included in order to enhance the final manuscript for the readers.

Abstract

·         Line 21. Please do not use pronouns in scientific writing such as (We) in all

·         The abstract is more description and does not support by digital results.

·         What is conclusion of the abstract?

Introduction

·         The introduction lack of the previous studies which related to this subject. There are several studies can be used to supported this point.

·         What is new in your work that makes a difference in the body of knowledge?

·         What has been done that goes beyond the existing research?

Materials and methods, Results and Discussions are well presented     ·         The resolutions of the figures should be improved.

·         Please, write the practical applications of your work in a separate section, before the conclusions and provide your good perspectives?

Conclusions

·         Please write about the limitations of this work in details in conclusion section?

Author Response

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Reviewer 2 Report

Dear Editor and Authors,

I have thoroughly reviewed the paper entitled “The multiple perspective response of vegetation to drought on the Qinghai-Tibetan Plateau” by Zhu et al. The paper examines the response of different vegetation types to drought in the highly sensitive and ecologically important area of the Q-T plateau. The authors investigated a variety of indexes and their temporal variations to access the response, resilience, and resistance of vegetation to drought. The paper’s topic and the methodology employed by the authors are within the scope of the Journal. The presentation is of high quality. The paper is well-written and structured. The graphs are appropriate and clearly demonstrate the differences in the different sub-regions of the Plateau. The introduction and the results sections are adequate and I really enjoyed reading the discussion section. The analysis of resilience and resistance of different vegetation types in association with Thornthwaite’s aridity index is an excellent idea with very interesting findings and I recommend to the authors extend it and make it the base for a future work.

I am glad to recommend the acceptance of the paper in its current form.

Author Response

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Reviewer 3 Report

The research “The multiple perspective response of vegetation to drought on the Qinghai-Tibetan Plateau” presented a space-time analysis to evaluate drought events in the Qinghai-Tibetan Plateau and what the behavior of the vegetation through the NDVI and SPEI indices. The research brought important results regarding the differences in the ecoregions and its pattern of changes in relation to the climate. The research is well structured and adequate between bibliographic review, methodology and results; The discussions brought analysis that adequately complemented the results. In view of these observations, I believe that the article is suitable for the theme of the journal, with some points being suggested below, that could be inserted in the methodology to facilitate the understanding of some stages.

L86. Specify the satellites used in the central objective.

L111-115. What images were used? What spatial and temporal resolution of the final product? What source of data acquisition?

L123-131 and Figure 1. The text referring to the sources in figure 1 should be moved to the topic: study area.

Topic 3.1. How was the drought frequency calculated (annual, monthly, etc)? Enter this information to make the drought frequency results easier to read.

 

 

Author Response

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Reviewer 4 Report

The paper titled The multiple perspective response of vegetation to drought on the Qinghai-Tibetan Plateau is interesting and within the scope of the Journal. It is well-organized and clear in most parts. In my comments, I have indicated some parts the authors could modify to increase clarity and improve the discussion.

Line 138. Insert in this line the citation to the SPEI calculation proposed in 2014.

Lines 153-154. What do you mean by annual SPEI12? Is it the average of the twelve SPEI12 monthly values ​​that fall in a given year? Please clarify.

Line 156. I suppose the pixel size depends on the input layers (climate and land cover). Can you specify the size?

Figure 2. Please add the unit of measure to drought duration in figure 2 (b)

Section 2.3.3. If you provide the ranges (domain) for the resistance and resilience values, you help in reading and interpreting the results

Line 221-224. This way of presenting the result seems to me to be a bit confusing. From the sentences “Figure 3 shows that the overall vegetation on the QTP presented a time-lag response to drought”, and the following one “About 10.91% of the vegetation had a significant time-lag to drought in May”, it seems that you always find better correlations adopting a time-lags between NDVI and SPEI. But this is not the case when i in equation (2) is 0. I suggest revising the sentences removing the reference to the time-lag and referring only to the correlation of the 1-month SPEI. In commenting Figure 3, point out that there is a strong spatial variability and that it is not always significant, even considering the maximum correlation among four different time-lags.

Figure 4. I believe (indeed I hope) that the reference to the SPEI time scale in the legend (fig. 4e) is wrong because, from the caption, it seems clear to me that the 4 colours are not SPEI time scales but the values ​​of i (eq.2 and eq.3) of the time-lag to obtain the best correlation in each pixel and month of the growing season. But the SPEI in figure 4 should always be the 1-month scale, as in figure 3. Isn't it? Furthermore, explain better how you obtain the Fig. 4e. I suppose that you averaged all the pixels belonging to the same crop type….

Line 241-246. To avoid confusion in reading the results, do not use the term “time scale” for both the number of months of the time-lag and for the SPEI time scale. You got confused too (see...fig 4e)

Figure 6f. As for fig. 4f, briefly explain how you obtain the information by crop type.

Line 269-270. Be careful in commenting on this result. From a physiological point of view, it makes little sense that forests respond to drought with shorter accumulated months than steppes or meadows. I believe that the result of fig. 6f makes sense and can be discussed only if the correlation (fig. 5f) is significant. And for forests, I don't think it is.

As highlighted by some authors (e.g., Vergni et al., 2021; Byun and Wilhite, 1999),  one of the shortcomings of traditional standardized indices (like SPI and SPEI) is that they do not take into account how stress is distributed over the period. For example, you could obtain the same SPEI3 both in the case in which all the rain of the period (for example, 100 mm) is concentrated in a single day of the 3-month period, and in the case in which it is distributed more evenly (for example 11 mm every 10 days). But obviously, the impact on vegetation would be very different. Do you think this could affect the correlation of the analysis you made? (in particular, that presented in fig. 5, 6). I suggest you consider this in your discussion.

 

References

Byun, H.-R., Wilhite, D.A. Objective quantification of drought severity and duration ( (1999) Journal of Climate, 12 (9), pp. 2747-275

 

Vergni et al. 2021. Effectiveness of the new standardized deficit distance index and other  meteorological indices in the assessment of agricultural drought impacts in central Italy, Journal of Hydrology, Volume 603, Part B, 2021,126986.

Author Response

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