Response of Vegetation Productivity to Greening and Drought in the Loess Plateau Based on VIs and SIF
Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsThe study was focused on monitoring of vegetation response to drought threat over Chinese Loess Plateau. This study could be important for all regions damaged by drought, especially for regions with eolian sediments. Despite of gains from remote sensing data and advance statistical analysis, the study is loaded by defects in Introduction as well as in description of methods used.
Define all abbreviations in the first occurrence of the each (sub)chapter. Consequently, explain all abbreviations of captures for all figures.
The Introduction should to be formulated on the basis of theoretical knowledge without any regional specification. First introductory sentense needs explanation, how does greenhouse effect enhance drought? What is effect of greenhousing to evaporation, when the study use information, for example, about evapotranspiration?
The introduction shoud contain knowledge about evaporation effects on climate change through vapor content in atmosphere or through cloud formation and/or more frequent storms.
Consider if mentions about Loess Plateau should to be presented on the Material section as description of the area inverstigated, or if you could generalize characteristics of the LP as relict of eolian sedimentation endangered due to desertification at working thesis of the Introduction.
The information about Grain for Green Project is not belonging to Introdution, because it was mentioned in Material and method section.
Specific comments:
Line 131: 6.4*105 km2 needs „5“ by upper index. Additionally, what about mean altitude and dominant altitudinal range?
Line 140: „ecological environment“ is a mishmash. Use only „environment“.
Line 143: Replace term „ecological security“ by „environmental security“.
Line 152: Please, specify (per cent) proportion of particular types of the landuse showed in the Figure 2.
Line 159: What is abbreviation GOSIF??? Explain here.
Line 161: What is OCO-2SIF? Explain, please.
Line 221: The information about Mann-Kendall test should to be improved through abbreviation „(M-K)“.
Lines 236-237: R2 means determination coeffient, not correlation coefficient.
Lines 346-365: What do „kNDVI:GPP“, „NIRv:GPP“ or „SIF:GPP“ mean? This abbreviations were not defined in methods. Please, specify them. Also, what do they mean? Is it ratio? Or, can they present formula of linear correlation? If yes, the correlation formula has usual form as y = a.x+b, e.g. kNDVI=a.GPP+b.
Lines 460-493: „Su et al.“, „Zhang et al.“ or „Zhu et al.“ were not written as tolerable citations. Please, improve them according to instruction for authors.
Comments on the Quality of English LanguageThe English editing is quite enough. Please, correct a few details about ecological conditions as "ecological environment" etc. The readibility would be also improved through better explanation of frequent abbreviations.
Additionally, reduce repetitive information between Introdution and methods.
Author Response
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Author Response File: 
Author Response.pdf
Reviewer 2 Report
Comments and Suggestions for AuthorsThe article deals with an interesting subject that has raised the concern of scientific community the last years. Particularly, it investigates the response of vegetation productivity to greening and drought. However, some major revisions are necessary prior to its publication in the journal. The main points need to be revised are the followings:
Line 39. Help the reader follow the text and understand the need/challenge of the topic you choose. It is mandatory to add comments about drought and how the Centre for Research on the Epidemiology of Disasters (CRED) place drought among the other natural disaster as depicted in their report (https://cred.be/sites/default/files/2021_EMDAT_report.pdf).
Line 40. Also give an official definition of drought as described by the World Meteorological Organization (WMO) https://wmo.int/about-us/world-meteorological-day/wmd-2020/drought and its classification (http://www.wamis.org/agm/pubs/brochures/WMO1006e.pdf).
Line 91. I think that “drought environment” must change to “arid environments.”
Line 270. It is very important to state and discuss that the different time scales of SPEI (1-month, 3- month, 6-month, and 12-month etc.) represent different aspects of drought (agriculture, hydrologic etc.) and as found in recent scholars at shorter time scales (SPEI3 and SPI6), there was an increase in the frequency of drought events, accompanied by a decrease in their duration. This implied that these shorter time scales exhibited recurrent climatological phenomena for drought. In contrast, longer time scales (SPEI12 and SPEI24) experienced less frequent drought episodes, but with longer durations (https://doi.org/10.3390/hydrology10080167, https://doi.org/10.3390/rs15184362). The aforementioned articles are in line with your outputs and strengthen the soundness of the research as similar findings are also stated by other researchers in common research. This could also be included in discussion part in line 508.
Line 315. It would be interesting to conduct a bivariate choropleth map to demonstrate drought magnitude summarizing SPEI and SSMI indices.
Line 340. Please increase the labels in axis-y.
Author Response
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Author Response File: Author Response.pdf
Reviewer 3 Report
Comments and Suggestions for AuthorsComments for author File: Comments.pdf
Comments and Suggestions for Authors
Review of Manuscript ID= forests-2820275
The paper is concerned about the vegetation response of vegetation productivity to greening and drought condition in the Loess Plateau based on vegetation indices (VIs) and solar-induced chlorophyll fluorescence (SIF) in China. The manuscript is well prepared, it is also vital to conduct such a study in the area where greenery activities has been carried out for so long to restore the degraded land. Improving the overall English language of the manuscript could highly increase the quality of the manuscript. Furthermore, based on the general comment, I do have some minor concerns that has to be clarify.
1. The abstract part should stand alone that readers regardless of their expert be able to read and understand it comfortably so that abbreviation are not allowed so please explain abbreviation when you use write them for the first time , for example three vegetation indices 16 (NDVI, NIRV, and kNDVI).
2. Introduction part line 35, 36. Please refresh the following sentence “With the continuous emission of anthropogenic CO2, the global greenhouse effect is becoming more and more significant, and the frequency and intensity of drought are also increasing”. Like “The continuous emission of anthropogenic global greenhouse like CO2 is becoming high that results in the increase of drought frequency and intensity of drought”
3. Next, line “Drought is one of the most prevalent natural disasters in the world, and has the most severe and widespread impacts on terrestrial ecosystem GPP of all climate extremes.”
I think it is enough say it as “Drought is one of the most prevalent natural disasters in the world, and has the most severe and widespread impacts on terrestrial ecosystem GPP.” What do you mean “of all climate extremes” do you mean of all climate type? Otherwise, “of all climate extremes” drought itself is a climate extreme. Therefore, it does not make sense
4. Authors should explain Abbreviation when they write it for the first time like “MODIS-GPP” line 69.
5. Introduction part Line 103, last paragraph “ cover types on the Loess Plateau were investigated, as well as he relationship between” please correct “he” as the.
6. In figure 11. How come the NDVI value range from -2 to 2? The normal NDVI value ranges from 1 to -1, How about the remaining VIs values vary? How does that value ranges?
7. In figure 12, why is the correlation between Vis small in evergreen forest and high in either grassland for forest?
8. Based on “Figure 7. Trend changes in aridity indices, VIs, SIF, and GPP from 2001-2020; significance distributions of SPEI, SSMI, GPP, NDVI, NIRV, kNDVI, and SIF, respectively, from a-g” . We can notice that SIF show extremely significant increase for entire China, while VIs indicates no significant increase, so which index we can rely on. Which one to truth or take it as the best if they have this much discrepancy?
9. Is all the satellite data verified with the observed data of the study area?
10. Why the authors preferred to use these satellite data sources while there are other many source of data? Like SPOT, Landsat over MODIS
11. In “Figure 12. Correlation of GPP anomalies with VIs and SIF anomalies. Sv, Gl, Cl, Fsg, Df and Ef are sparse vegetation, grassland, cultivated land, forest shrub, deciduous forest and evergreen forest, respectively.” Why is the correlation in Df and Ef is quite low? How is the uncertainty?
Author Response
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Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
Comments and Suggestions for AuthorsThank you for acceptance of all recommendations. The study is now close to be prepared for publication. Please, check only all chemical abbreviations (e.g. in line 45) as well as add one specific citation on the WMO report (line 57).
Author Response
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Author Response File: Author Response.pdf
Reviewer 2 Report
Comments and Suggestions for AuthorsThe article can be published in the current form
Author Response
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