Unraveling Effect of Snow Cover on Spring Vegetation Phenology across Different Vegetation Types in Northeast China

Round 1

Reviewer 1 Report

In this study, the authors analyzed the SOS and its response to snow cover changes from 1982 to 2015 in Northeast China based on multiple satellite data products and climate datasets. The results showed that snow cover has a significant impact on SOS. A reduction in snow cover leads to an advancement of the SOS in forests, while an increase in snow cover results in an earlier SOS for grasslands and croplands. The snow cover changes affect the SOS of forests and rainfed croplands through the “temperature effect”, while they impact the SOS of grasslands through the “moisture effect”. These findings are very interesting with quite clear conclusions, which will attract reaearchers in relative study areas. I think the manuscript can be publishied after some minor issues are addressed.

Frist, there is no line numbers.

Second, there are some small mistakes, such as no superscript for “yr -1”.

Third, the results about Table 1 are a little hard to understand. I suggest to add the non-significant results. Otherwise, only a samll part of the pixels are significant (mostly less than 10%). I may be not sufficient to say "dominant".

Fourth, the organization of Discussion is a little confusing. I do not quite understand the logic differences of 4.1 and 4.2 for their titles. Furthermore, the reason why more snow lead to later SOS in mountain ares but earlier SOS in plain ares should be discuss more in details. Because this does not seem to be explained by "temperater effect" or "moisture effect" in the later part. 

I suggest the authors to double check and polish the English expressions to avoid misleading.

Author Response

Dear Editor and Reviewer,

Please find the attached document for your review.

Thank you for your time and consideration.

Sincerely,

Chong Ren

 

Author Response File: Author Response.docx

Reviewer 2 Report

The authors showed a comprehensive analysis and a nice design for exploring snow-vegetation-dynamics interactions. The methods are detailed, the results are well structured, and the discussion is strong. Apart from this, there are several minor concerns or comments needing the authors to clarify and make modifications. 

1.    abstract:   “However, snow cover indicators mainly exhibited negative correlations with the SOS of grasslands and..” change “with” to “in”

2.    introduction: “The start of the growing season (SOS) in China’s temperate ecosystems explores distinct spatial patterns across vegetation types” “explores”? to displays?

3.    Introduction “Snow cover also affects the optical reflectance, thus influencing…” Please make it clear: "The declining snow-cover makes the surface spectral reflectance rise (i.e., NDVI)". Adding detailed information will make your introduction more convincing.

4.    Introduction “within the high-latitude region of the country…” you indicate the latitudinal information of the northeast China region here, then the readers could have a direct recognition of this region.

5.    “Thus, the impact of snow cover changes in different vegetation types should attract more attention. ” you may delete this sentence, I believe you have already shown clear information about your topic in this paper.

6.    Figure 1. You may add one subfigure about the relative proportion of different crop types over this region. Basically, it will give some information about the dominant vegetation types there and also indicate the relative sample numbers when you do the statistical analysis in the other sections.

7.    Please add a reference (citation) to CCI LC.

8.    “Our emphasis was …” One concern is that when you only keep the pixels without land-cover-changes, how can you avoid these factors-induced impacts over the SoS? In other words, this could be another interesting point to explore the drivers of SOS trends in this area apart from the aforementioned climatic variables.

9.    “was not currently detectable in satellite” change to “challenge to detect with”

10. “ECMWF ERA-5 land dataset. ” add corresponding citation.

11. “NDVI values during the uncontaminated non-growing season.” You could change to the term “dormant periods. I highly recommend you cite “Reconstruction of a complete global time series of daily vegetation index trajectory from long-term AVHRR data", which provides the theory of background VI.

12. “threshold of the NDVIday is …”  NDVIday?

13. Discussion 4.2  “However, the effect of snow cover varies among forests, grasslands, and rainfed croplands, which is consistent with previous studies indicating that the response of vegetation phenology to changes in snow cover is influenced by the underlying surface conditions and different ecosystems” This sentence is too long, please rewrite it.

 

14. Discussion 4.3. “Apart from the influence of snow cover indicators and climate factors, human management might also play a contributing role in rainfed cropland, such as cultivar and sowing date” Please add [1] and [2]. [1] “Characterizing spatiotemporal patterns of crop phenology across North America during 2000–2016 using satellite imagery and agricultural survey data” [2] “Shen, Y., Zhang, X., Yang, Z., 2022. Mapping corn and soybean phenometrics at field scales over the United States Corn Belt by fusing time series of Landsat 8 and Sentinel-2 data with VIIRS data. ISPRS J. Photogramm. Remote Sens. 186, 55–69” 

Some minor modifications need to be done. the detail suggestions can be found in the comments. 

Author Response

Dear Editor and Reviewer,

Please find the attached document for your review.

Thank you for your time and consideration.

Sincerely,

Chong Ren

Author Response File: Author Response.docx

Reviewer 3 Report

"Unraveling snow cover effect on spring vegetation phenology across different vegetation types in Northeast China” I enjoyed reading this work. It is nicely written and has proper structure. This is an important paper that explores the impact of snow cover changes on the spring phenology of vegetation types. For this, remote sensing-derived products and correlation analysis are employed. Below, I have provided my comments to enhance the quality of the manuscript.

 

Comments and suggestions:

 

 Introduction:

- The introduction is well justified; however, it lacks reviewing previous studies or similar investigations at a local or regional level. I quickly looked at the 'Google scholar' and it seems that there are other studies. I suggest adding a new paragraph on available techniques and similar investigations, and then point out how this study is different from others.

Discussion

It is understandable that this study has focused on analyzing the SOS and its response to snow cover changes, but it would be useful to put this concept within the framework of the phenological characteristics of flowering species (i.e., the SOS) or plant communities and how this would influence ecological processes. In this context, a new paragraph highlighting the implications and benefits of the provided information is suggested.

 

 

 

Best wishes,

 

Comments for author File: Comments.pdf

Author Response

Dear Editor and Reviewer,

Please find the attached document for your review.

Thank you for your time and consideration.

Sincerely,

Chong Ren

Author Response File: Author Response.docx