Spatio-Temporal Characteristics of Ice–Snow Freezing and Its Impact on Subtropical Forest Fires in China

Round 1

Reviewer 1 Report

 

Forest fires are influenced by various factors, and studying these influencing factors is of significant importance for controlling and preventing forest fires. This ms explores the impact of snow and ice cover in a certain region of China on forest fires using remote sensing data and spatial analysis methods, providing valuable guidance for forest management in this area. The ms is well-structured with a coherent logical flow, and the descriptions of data and methods are comprehensive. However, there are still some issues that the author needs to address.

1 The introduction requires further summarization and clarification by the authors. The current content is too broad, lacking a concise summary of the research on the impact of Ice-snow freezing on forest fires. The author's primary focus is the study of this impact, and the current introduction appears to deviate from this central theme.

2 The data description in the article is overly simplistic. It is essential for the author to provide detailed information about the sources of data, such as DEM (Digital Elevation Model) and Landsat imagery, as well as the sensors used for data collection.

3 The method used to validate the extracted fire information and the data sources employed for this validation process should be added by the authors.

4 It would be beneficial to separate the discussion section from the results section as the current structure appears somewhat disorganized.

5 The quality of all figures in the manuscript needs to be improved, with a particular emphasis on increasing the font size.

 

 

Author Response

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Author Response File: Author Response.docx

Reviewer 2 Report

Figure 1 shows the subtropical region in China, which is challenging to get for the global audience. Put an inset map to show where the study region has been picked in China. Besides, it is unclear how the forest and non-forest areas have been delineated, whether any vegetation indices have been used or from any other source it has been acquired. 

Mention which landcover data and DEM of 30-m resolution have been used. 

Authors must explain why EVI has been used instead of NDVI with proper support of literature. 

In Figure 10, B and D can be modified. Identifying which province has recorded higher or lower fire records is very difficult. It would be better if the authors found 3-4 major fire-affected provinces and showed line graphs for them, and for the rest of the provinces, put similar graphs into the supplementary. 

In lines 384-385, the authors mentioned, "Guizhou province had a significant increase in the number of forest fire hotspots due to the increasing in forest-damaged areas." I think the argument should be vice versa. 

There must be a composite graph showing month-wise temperature, humidity, precipitation and fire counts over the study area and then describe how the prevailing weather conditions in different months impact the intra-annual pattern of fire occurrence. The weather pattern and fire occurrence relation, as described in the article, is insufficient. 

Line 397, "In winter, the dry climate makes the air less humid, which creates favourable conditions for forest fires to occur". February in the Northern Hemisphere is in the winter season. I am curious how the lower temperature in winter favours the fire. Are the authors suggesting that air temperature has a minimal role and humidity has a major significance in fire occurrences over this region?  

The correlations shown in Figures 11 and 12 depict very low association. I wonder if these correlations are significant at 95% confidence intervals. With such a low association, how is the impact of ice-snow freezing conditions relevant to fire occurrence? There could be a lag-effect relation between ice-snow freezing conditions and fire occurrence. There also could be rapid soil drydowns to trigger the fire. These factors are not considered. 

Without carrying out statistical tests, the authors must not mention that "forest fires have shown a significant downward trend since 2008."

Mention the unit in Figures 7A, 7B, 8, 11 and 12. 

The topic is interesting, and the description of data processing is also good enough, but the current situation of problem investigation methods is inadequate. The discussion must be improved. Why the association is low, whether it is influencing the fire or some confounding variables, is essential; such discussion is required. 

Do some Grammatical checks. Improve the writing in the result and discussion sections. 

Author Response

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Author Response File: Author Response.docx

Reviewer 3 Report

Title

Spatio -Temporal Characteristics of Ice-snow Freezing and Its Impact on Subtropical Forest Fires in China

Summary

The article tries to relate ice-snow freezing with forest fires. Their main objectives were the following ideas. First to analyse the freezing changes in subtropical China, second to analyse the spatio-temporal distribution patterns of forest fires and third to explorer the responsive region and time of forest fires to ice-snow damage. They got their objectives using MODIS images, vegetation index and historical precipitation and snow-freezing days data. Their results showed that the whole study area shows a spatial distribution pattern of cold weather in the north and warm weather in the south. Forest fire distribution patterns during 2001 -2019 exhibited that Hunan province had the highest incidence of forest fires in subtropical China. By other hand, the Moran’s Index showed a decreasing state, indicating a decrease in the spatial clustering of forest fires in the study area. They infer that this data may be related to the significant reduction in the forest-damage areas by fires after 2009. Also, they found a positive correlation (0.25 and 0.32) between the forest damage area caused by fire and its precipitation during ice-snow freezing period in most provinces. Finally, they conclude that during the period of 2001-2019 the ice-snow freezing of forest vegetation was more serious in Hunan, Jianxi, Hubei and Anhui provinces. Heavy ice-snow freezing can increase combustibles and have a greater impact on forest fire behaviour in February and March.

Article’s impression:

I think the idea could be good to understand ice-snow freezing impacts in forest environments using remote sensing data. However, I consider that the article needs important improvements with the purpose to give to any reader their idea. For example, they need to state their objectives in a clear way. Also, they need to support their findings with other works. For example, they found small or very weak correlations (less than 0.35) and other images report corelations of 0.12, 0.01 etc, which give to any reader that the variables have not a real correlation and suggests that there is another variable that could relate forest fire distribution. For example, it is well known that higher temperatures and dry season cause many forest fires in other places worldwide. Their conclusion must match with their objectives. Also explain in their methods the indices that they used and explain why these indices could help to understand this phenomenon.

My recommendation is:

Revise the article to amend major corrections

General corrections

State in a clear way your objectives.

Please, improve your conclusion. Please give a general conclusion rather than bullet points.

Please, support your discussion with other works that relate the same variables.

Author Response

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Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

The authors answered all my concerns, it is recommended to publish.

Author Response

Thank you to the reviewers for their recommendations and recognition. 

Reviewer 2 Report

I appreciate the authors' efforts in the revision. 

Author Response

Thanks for your advice.  We have thoroughly read the entire paper, correcting grammatical errors and addressing any descriptions that lack clarity or coherence. Furthermore, we have reorganized the conclusion section where we provide some general conclusions that match our research objectives.

Reviewer 3 Report

Title

Spatio -Temporal Characteristics of Ice-snow Freezing and Its Impact on Subtropical Forest Fires in China

Summary

The article tries to relate ice-snow freezing with forest fires. Their main objectives were the following ideas. First to analyse the freezing changes in subtropical China, second to analyse the spatio-temporal distribution patterns of forest fires and third to explorer the responsive region and time of forest fires to ice-snow damage. They got their objectives using MODIS images, vegetation index and historical precipitation and snow-freezing days data. Their results showed that the whole study area shows a spatial distribution pattern of cold weather in the north and warm weather in the south. Forest fire distribution patterns during 2001 -2019 exhibited that Hunan province had the highest incidence of forest fires in subtropical China. By other hand, the Moran’s Index showed a decreasing state, indicating a decrease in the spatial clustering of forest fires in the study area. They infer that this data may be related to the significant reduction in the forest-damage areas by fires after 2009. Also, they found a positive correlation (0.25 and 0.32) between the forest damage area caused by fire and its precipitation during ice-snow freezing period in most provinces. Finally, they conclude that during the period of 2001-2019 the ice-snow freezing of forest vegetation was more serious in Hunan, Jianxi, Hubei and Anhui provinces. Heavy ice-snow freezing can increase combustibles and have a greater impact on forest fire behaviour in February and March.

Article’s impression:

I have read the first version and this second one. I can see some little improvements in the results and discussion section. However, they did not consider some important points. First, they did not state their objectives in a clear way. They only change the colour of the sentence to highlight the objective that they wrote the first time. Second, they did not improve their conclusion section. I suggested to write a general conclusion rather than show a conclusion with several bullet points.

My recommendation is:

Revise the article to amend major corrections

General corrections

I said my changes in the article’s impression.

No comments

Author Response

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Author Response File: Author Response.docx