Relationship of Oedaleus decorus asiaticus Densities with Soil Moisture and Land Surface Temperature in Inner Mongolia, China

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

• This study has limited scope . Means It only considers SM and LST, without discussing other important ecological factors like vegetation, predators etc
• While relationships are established, the study does not prove that SM and LST directly cause changes in decorus density.
• The study is focused on Inner Mongolia, and its applicability to other regions is uncertain.
• This is a good study with valuable insights, but it could be improved by considering additional ecological factors, testing alternative models, and discussing the broader applicability of its findings.
• Were there any limitations in the dataset, such as missing values or inconsistencies in data collection?
• What might be the ecological explanation for the negative correlation between S8 and O. decorus density? Include that too.
• Why does O. decorus density increase with S9 but decline sharply beyond 0.29 m³/m³? Give reasons in the manuscript.
• Enhance Figure 1. Distribution of O.decorus survey sites from 2018 to 2020, by adding more features like latitude and longitude coordinates to improve geographic accuracy and help readers precisely locate the study area.
• Were there any seasonal variations in the impact of LST and SM on O. decorus density?
• Did you observe any spatial patterns in the distribution of O. decorus based on SM and LST?
• Can the GAM model be generalized to other regions beyond Inner Mongolia?
• In Table 2. Monthly Soil moisture and land surface temperature, it is better to tell the year too rather than saying the surveyed year.
• Include some management strategies could be derived from these findings to control O. decorus outbreaks?
• Could remote sensing be used to improve real-time monitoring and early warning systems for O. decorus outbreaks?
• How might climate change impact the relationship between LST, SM, and O. decorus densities in the future?
• Even though the abstract is well written, the conclusion can be more decisive. it can be improved and expanded by indicating the critical aspects of this analysis and how it can be improved in the future (eventhough you indicated in recommendations).
• The reference you provided appears to have a duplication in the serial number. For example, if this is listed as reference [1], and there is another entry also labeled 1. , that would indicate a duplication of the serial number.
•  

Author Response

Response to Reviewer 1 Comments

Thank you very much for your comments and suggestions. We have studied your suggestions carefully and made the following changes. We hope our responses will satisfy you.

 

Comments 1: This study has limited scope. Means It only considers SM and LST, without discussing other important ecological factors like vegetation, predators etc

Response 1: Thank you for your comments. Grasshopper infestation is a complex phenomenon. Therefore, to accurately monitor and predict the dynamic changes in O. decorus density, we will establish comprehensive models that integrate additional datasets, including remote sensing, meteorological, and geographic information, in future studies. However, in this paper, we primarily explored the relationship between O. decorus density and SM/LST. Other environmental factors, such as vegetation and predators, were not considered.

Comments 2: While relationships are established, the study does not prove that SM and LST directly cause changes in decorus density.

Response 2: Thank you for your suggestion. In this study, we established the GAM model and analyzed how SM and LST affect the O. decorus density. The results indicated that S8, S9, L10, L3, L5, and L6 significantly influenced the density of O. decorus (p < 0.05) (Table 3). Consequently, these findings confirm that the density of O. decorus is associated with SM and LST. However, further investigation is required to determine whether SM and LST directly affect the density of O. decorus.

Comments 3: The study is focused on Inner Mongolia, and its applicability to other regions is uncertain.

Response 3: Thank you for your comments. Our study primarily focuses on the pests of O. decorus and all fieldwork is conducted in Inner Mongolia. The purpose of this study is to understand the potential relationship between SM/LST and O. decorus density. Therefore, its applicability in other regions remains uncertain, which is a limitation of this paper that requires further verification. However, this study focuses solely on one insect. According to previous research, the ecological and environmental conditions in which the same species of grassland locusts thrive are generally consistent. Therefore, we believe that the results of this study can also be applied to other areas.

Comments 4: This is a good study with valuable insights, but it could be improved by considering additional ecological factors, testing alternative models, and discussing the broader applicability of its findings.

Response 4: Thank you for your suggestions and for affirming this article. As you know, our research mainly addresses the question of how SM/LST influence O. decorus density. In the upcoming study, we will further examine the effects of various environmental factors on the spatial distribution of grasshopper populations. Thank you for your suggestions again.

Comments 5: Were there any limitations in the dataset, such as missing values or inconsistencies in data collection?

Response 5: Thank you for your comment. There are no limitations or error messages in the dataset because it was cleaned and filtered prior to use.

Comments 6: What might be the ecological explanation for the negative correlation between S8 and O. decorus density? Include that too.

Response 6: Thank you for your suggestions. The negative correlation between S8 and O. decorus density may be explained by soil water content exceeding the species' optimal range, which reduces spawning or prevents oviposition. Because grasshoppers require a suitable soil environment for spawning.

Comments 7: Why does O. decorus density increase with S9 but decline sharply beyond 0.29 m³/m³? Give reasons in the manuscript.

Response 7: This is a good suggestion. We give a reason in the discussion section of the manuscript. “This indicates that abundant SM has adverse impacts on O. decorus occurrence. SM in early autumn can impact egg preservation, thereby avoiding water loss from eggs and increasing the survival of eggs during overwintering [44]. Higher water content in the soil during the egg stage could favor natural enemies, such as parasites, fungi, and bacteria, of O. decorus. This could indirectly affect the eggs, resulting in decreased survival or reproduction rates [15,29].” Thank you for your suggestion again.

Comments 8: Enhance Figure 1. Distribution of O.decorus survey sites from 2018 to 2020, by adding more features like latitude and longitude coordinates to improve geographic accuracy and help readers precisely locate the study area.

Response 8: This is a good comment. We add the latitude and longitude in Figure 1.

Comments 9: Were there any seasonal variations in the impact of LST and SM on O. decorus density?

Response 9: Thank you for your comments. There are significant seasonal variations in the impact of LST and SM on the density of O. decorus. In August and September, SM is a primary factor influencing the selection of oviposition sites. Meanwhile, LST primarily affects the eggs overwintering and incubation of eggs.

Comments 10: Did you observe any spatial patterns in the distribution of O. decorus based on SM and LST?

Response 10: Thank you for your suggestions. As we know, grasshopper infestation is a complex process affected by other factors such as vegetation conditions, climatic factors, geographic and geomorphic conditions, and grasshopper abundance. Therefore, it is necessary to establish comprehensive models that integrate a wider range of source datasets, including vegetation, soil, meteorological, and geographic conditions. Therefore, this study mainly explored the impact of SM and LST on O. decorus density. We did not analyze the spatial distribution of O. decorus.

Comments 11: An the GAM model be generalized to other regions beyond Inner Mongolia?

Response 11: Thank you for your question. According to previous research, the ecological and environmental conditions that support the same species of grassland locusts are generally consistent. Therefore, we believe that the findings of this study can also be applied to other regions.

Comments 12: In Table 2. Monthly Soil moisture and land surface temperature, it is better to tell the year too rather than saying the surveyed year.

Response 12: Thank you for your suggestions. This is a good idea. We have changed the Table 2.

Table 2. Monthly Soil moisture and land surface temperature.

Month	Soil moisture	Land surface temperature
July of the year preceding theyear	S7	L7
August of the year preceding the year	S8	L8
September of the year preceding the year	S9	L9
October of the year preceding the year	S10	L10
November of the year preceding the year	S11	L11
December of the year preceding the year	S12	L12
January of the year	S1	L1
February of the year	S2	L2
March of the year	S3	L3
April of the year	S4	L4
May of the year	S5	L5
June of the year	S6	L6

 

Comments 13: Include some management strategies could be derived from these findings to control O. decorus outbreaks?

Response 13: Thank you for your comment. Our results confirm that SM and LST are considerably correlated with O. decorus population density, especially SM in August, which can be used to predict and monitor the dynamic distribution of O. decorus density.

Comments 14: Could remote sensing be used to improve real-time monitoring and early warning systems for O. decorus outbreaks?

Response 14: Yes, I believe that remote sensing can be used to improve real-time monitoring and early warning systems for O. decorus outbreaks.

Comments 15: How might climate change impact the relationship between LST, SM, and O. decorus densities in the future?

Response 15: Thank you for your suggestions. With the increasing temperatures across the globe, warmer winters are becoming more common. This trend promotes a higher survival rate of eggs and enhances the reproductive capabilities of grasshoppers in the next generation, leading to an increased risk of grasshopper plague outbreaks

Comments 16: Even though the abstract is well written, the conclusion can be more decisive. it can be improved and expanded by indicating the critical aspects of this analysis and how it can be improved in the future (eventhough you indicated in recommendations).

Response 16: Thank you for your suggestions and for affirming this article. We have revised the conclusions of this paper as follows: “This study developed a GAM using six environmental factors (S8, S9, L10, L3, L5, and L6) as input parameters. These six factors accounted for 82.4% of the variance in O. decorus density at the logarithmic scale, indicating the model’s potential to predict O. decorus population density. Interestingly, there were considerable seasonal variations in the effects of LST and SM on the density of O. decorus. In August and September, SM showed a strong correlation with O. decorus density. It has emerged as a key factor influencing the selection of oviposition sites and serves as a vital indicator for predicting and monitoring O. decorus occurrences. Meanwhile, LST primarily impacted the overwintering and incubation of O. decorus eggs. The most considerable LST factor with strong predictive capability for O. decorus population density was L10, followed by L6, L3, and L5. Our study has identified the key factors of SM/LST that determine the density of O. decorus. All findings could provide valuable insights for monitoring and predicting future outbreaks of O. decorus. While our research was based on only three years of fieldwork (2018–2020), future studies could address data limitations by enriching the field survey data of O. decorus. Additionally, we could establish comprehensive models that integrate various environmental factors, such as vegetation, soil, climate, and topographical conditions, to predict and monitor the outbreak of O. decorus.”

Comments 17: The reference you provided appears to have a duplication in the serial number. For example, if this is listed as reference [1], and there is another entry also labeled 1. , that would indicate a duplication of the serial number.

Thank you for your comments. We have reviewed all references.

Once again, we thank you for your comments and suggestions. We greatly appreciate these valuable comments and suggestions which have helped us improve the manuscript and helped me learn a lot. Thank you!

 

Reviewer 2 Report

Comments and Suggestions for Authors

This paper clearly presents new data and findings on the relationships between grasshopper abundance and influencing environmental factors (soil moisture and land surface temperature), observed in the natural environment.

The presentation is thorough, clear and sound. It provides valuable results, relevant for improved prediction of grasshopper pest risk, and is of interest to a wide audience.

There are two very minor corrections that I noted:

1. Page 2, last paragraph, delete duplication of "egg laying".
2. Page 11, Conclusion - should this read "(L10)", not (S10)?

   "sites with elevated LST (S10) during early winter of the previous year."

 

Author Response

Response to Reviewer 2 Comments

Thank you very much for your comments and suggestions. We have studied your suggestions carefully and made the following changes. We hope our responses will satisfy you.

Comments 1: This paper clearly presents new data and findings on the relationships between grasshopper abundance and influencing environmental factors (soil moisture and land surface temperature), observed in the natural environment.

The presentation is thorough, clear and sound. It provides valuable results, relevant for improved prediction of grasshopper pest risk, and is of interest to a wide audience.

Response 1: Thank you for your comments and for affirming this article.

Comments 2: Page 2, last paragraph, delete duplication of "egg laying".

Response 2: Thank you for your suggestions. We have deleted duplication of "egg laying".

Comments 2: Page 11, Conclusion - should this read "(L10)", not (S10)? "sites with elevated LST (S10) during early winter of the previous year."

Response 2: This is a good suggestion. We have changed it and revised the conclusions of this paper as follows: “This study developed a GAM using six environmental factors (S8, S9, L10, L3, L5, and L6) as input parameters. These six factors accounted for 82.4% of the variance in O. decorus density at the logarithmic scale, indicating the model’s potential to predict O. decorus population density. Interestingly, there were considerable seasonal variations in the effects of LST and SM on the density of O. decorus. In August and September, SM showed a strong correlation with O. decorus density. It has emerged as a key factor influencing the selection of oviposition sites and serves as a vital indicator for predicting and monitoring O. decorus occurrences. Meanwhile, LST primarily impacted the overwintering and incubation of O. decorus eggs. The most considerable LST factor with strong predictive capability for O. decorus population density was L10, followed by L6, L3, and L5. Our study has identified the key factors of SM/LST that determine the density of O. decorus. All findings could provide valuable insights for monitoring and predicting future outbreaks of O. decorus. While our research was based on only three years of fieldwork (2018–2020), future studies could address data limitations by enriching the field survey data of O. decorus. Additionally, we could establish comprehensive models that integrate various environmental factors, such as vegetation, soil, climate, and topographical conditions, to predict and monitor the outbreak of O. decorus.”

Once again, we thank you for your comments and affirming this study.

Reviewer 3 Report

Comments and Suggestions for Authors

I have reviewed this paper for a different journal previously. I appreciate the authors work revising the Introduction and some of the Methods in this paper. The paper is easier to evaluate, but the methods that the authors employ and their interpretation of the results are not yet clear.

 

For example, statement of application of six variables in the GAM (last sentence of the Methods) is made before the justification for excluding the other variables (first line of the Results).

 

In the first line of the Results, it would be easier to read and comprehend if these were organized somehow. For example, start with S1 and state S1 with S2, S11, and S12; S2 with S3, S11, and S12; S3 with S11 and S12; S9 with S10, L5, L7, and L9; S11 with S12; L1 with L12; L2 with L12; L5 with L9; and L9 with L10. Then state the last sentence of the Results 'Due to collinearity of the other variables, we applied S8, S9, L3, L5, L6, and L10 as input parameters to build GAM. However note that you should also include a single collinear variable, such as S1, to represent the suite of variables that it is collinear with (i.e., S1 with S2, S11, and S12). Otherwise you're really missing soil moisture during the winter months altogether. Then you can also include S3 because it is not collinear with S1. Also note that by the standards you have set, S9 and L5 should not both be in the GAM analysis, because they are collinear. You can also include L1, L2, L4, and L11 in the GAM.

 

Figure 2 legend needs to be corrected. The plotted correlations are not between any two parameters, but between a parameter of L and any parameter of S or vice versa.  In addition, could the authors explain what the relative sizes of the circles indicate?

 

In the section ‘Relationship between O. decorus Densities and Daily SM’, the raincloud plots are nice but they are difficult to interpret because there are no accompanying statistical tests of differences among the density levels. Although the medians and ranges are visible in the raw data and box plots, how can we tell if one box plot differs significantly from the next? For example, line 293 'Moreover, SM content varied significantly between lower grasshopper density (<30 grasshoppers/m2) and higher grasshopper density (>30 per m2). How do the authors know that this relationship is significant?

 

As I requested in a previous review, can the author explain further how these plots work? There are 22 sites in the 0, 8 per m2 category but only 5 sites in the 90, 150 category. Yet the number of data points is the same. So the soil moisture data must be for each day of the month (as mentioned in the Figure legend), which can not be temporally independent if a weather event lasts more than one day. In addition, shouldn't there be soil moisture data for each of the 22 sites (e.g. 22x31 data points for August for the 0 to 8 density class)?

 

In general, the authors need to make very clear what they did and what they can conclude. Links between results from Fig 3, 4 and 5 should be made explicit. There are many caveats with this study, not least of which are the spatial and temporal autocorrelation among survey sites and years, the differences in spatial areas surveyed among years, the few numbers of years surveyed, and other factors that can bias the data analyses. These caveats need to be expressed as sources of error in the Discussion.

 

Minor comments

Abstract and throughout: Put a space between O. and decorus and italicize the species name.

Second paragraph of Introduction: Are you sure ‘extremely low temperatures trigger egg laying’? That seems counter-intuitive.

Correct typos in Title for Reference 2.

Table 1 Separate the number of survey sites into separate columns for each year

Discussion

In general, the Discussion is simply a repetition of the Results and does not interpret the findings, indicate what is novel about the study, review the sources of error and other caveats, or compare and contrast the results with previous findings. Because of the problems with lack of spatial and temporal independence of the data in the analyses, the authors have to be very clear that their analyses and conclusions are limited by that fact.

‘Therefore, we can conclude that O. decorus densities are significantly correlated with SM in the oviposition period, as well as with LST and SM during the early overwintering period [21,30].’  Conclusion based on 3 years of data. That's an important caveat.

‘However, when L6 is greater than 36.8 °C, the opposite effect is observed. When L6 is higher than 39.8 °C, LST no longer remains the decisive factor.’ This description of the effect of L6 is very confusing. The increase in density with L6 is based on a single point. What does it mean that it’s no longer the ‘decisive factor’ when L6 is greater than 39.8 C?

‘Similar results were obtained from the response of diverse O. decorus densities to daily SM and LST’ Can the authors explain how the results from the daily SM and LST values were similar to the trends of hopper density with the mean SM and LST values?

‘vegetation type, vegetation coverage, geographic and geomorphic conditions, and grasshopper abundance’  It’s not clear what you mean by abundance. Do you mean 'grasshopper abundances in previous years' or 'abundances in nearby sites'?

Author Response

Thank you very much for your comments and suggestions. We have studied your suggestions carefully and made the following changes. We hope our responses will satisfy you.

Comments 1: I have reviewed this paper for a different journal previously. I appreciate the authors work revising the Introduction and some of the Methods in this paper. The paper is easier to evaluate, but the methods that the authors employ and their interpretation of the results are not yet clear. For example, statement of application of six variables in the GAM (last sentence of the Methods) is made before the justification for excluding the other variables (first line of the Results).

Response 1: Thank you for your suggestion. We have removed the last sentence of Methods and checked for similar problems.

Comments 2: In the first line of the Results, it would be easier to read and comprehend if these were organized somehow. For example, start with S1 and state S1 with S2, S11, and S12; S2 with S3, S11, and S12; S3 with S11 and S12; S9 with S10, L5, L7, and L9; S11 with S12; L1 with L12; L2 with L12; L5 with L9; and L9 with L10. Then state the last sentence of the Results 'Due to collinearity of the other variables, we applied S8, S9, L3, L5, L6, and L10 as input parameters to build GAM. However note that you should also include a single collinear variable, such as S1, to represent the suite of variables that it is collinear with (i.e., S1 with S2, S11, and S12). Otherwise you're really missing soil moisture during the winter months altogether. Then you can also include S3 because it is not collinear with S1. Also note that by the standards you have set, S9 and L5 should not both be in the GAM analysis, because they are collinear. You can also include L1, L2, L4, and L11 in the GAM.

Response 2: Thank you for your idea. We have revised the statement to read “For example, S1 is correlated with S2, S11, and S12; S2 is correlated with S3, S11, and S12; S3 is correlated with S11 and S12; S9 is correlated with L5, L7, L9, and S10; S11 is correlated with S12; L1 is correlated with L12; L2 is correlated with L12; and L9 is correlated with L5 and L10.”

Besides, we constructed multiple GAMs including a single environmental factor and multiple environmental factors as input parameters. We found that the GAM constructed using S8, S9, L3, L5, L6, and L10 exhibited the GCV score, indicating that it is the most optimal model. That is the primary reason why other environmental factors were not included.

Comments 3: Figure 2 legend needs to be corrected. The plotted correlations are not between any two parameters, but between a parameter of L and any parameter of S or vice versa.  In addition, could the authors explain what the relative sizes of the circles indicate?

Response 3: Thank you for your suggestion. We have made the following changes to Figure 2:

Figure 2. Pearson correlation analysis between any two parameters. (Notes: Histograms along the diagonal indicates environmental factors. Scatter plots show the relationships between any two factors on the diagonal where the x-axis and y-axis are the variate of environmental factors above or below, and left and right, respectively. The numbers above the diagonal indicate the correlation coefficient and significance level. *: P<0.05, **: P<0.01, and ***: P<0.001.)

Comments 4: In the section ‘Relationship between O. decorus Densities and Daily SM’, the raincloud plots are nice but they are difficult to interpret because there are no accompanying statistical tests of differences among the density levels. Although the medians and ranges are visible in the raw data and box plots, how can we tell if one box plot differs significantly from the next? For example, line 293 'Moreover, SM content varied significantly between lower grasshopper density (<30 grasshoppers/m2) and higher grasshopper density (>30 per m2). How do the authors know that this relationship is significant?

Response 4: Thank you very much for your all comments and suggestions. In academic writing, the adjective “significant” should be used for statistical descriptions and references. Just like you said. There are no accompanying statistical tests of differences among the density levels. Therefore, we have transformed ‘significant’ into ‘considerable’. Thank you for your again. Additionally, similar problems were modified.

Comments 5: As I requested in a previous review, can the author explain further how these plots work? There are 22 sites in the 0, 8 per m2 category but only 5 sites in the 90, 150 category. Yet the number of data points is the same. So the soil moisture data must be for each day of the month (as mentioned in the Figure legend), which can not be temporally independent if a weather event lasts more than one day. In addition, shouldn't there be soil moisture data for each of the 22 sites (e.g. 22x31 data points for August for the 0 to 8 density class)?

Response 5: Thank you for your suggestions. In sections 3.4.1 and 3.4.2, the average daily SM and LST at various density levels of O. decorus were calculated, which is why the number of data points remains consistent.

Comments 6: In general, the authors need to make very clear what they did and what they can conclude. Links between results from Fig 3, 4 and 5 should be made explicit. There are many caveats with this study, not least of which are the spatial and temporal autocorrelation among survey sites and years, the differences in spatial areas surveyed among years, the few numbers of years surveyed, and other factors that can bias the data analyses. These caveats need to be expressed as sources of error in the Discussion.

Response 6: Thank you very much for your all comments and suggestions. We provided an analysis of the results presented in Sections 3.3 (Figure 3) and 3.4 (Figures 4 and 5) in the discussion section.

Comments 7: Abstract and throughout: Put a space between O. and decorus and italicize the species name.

Response 7: Thank you for your suggestions. We have added a space between O. and decorus and italicize the specie name.

Comments 8: Second paragraph of Introduction: Are you sure ‘extremely low temperatures trigger egg laying’? That seems counter-intuitive.

Response 8: Thank you for your comment. This is a mistake on my part. We added "not" after "can". The full sentence is as follows: “Grasshoppers tend to prefer warmer areas for spawning, while extremely low temperatures can not trigger egg laying.”

Comments 9: Correct typos in Title for Reference 2.

Response 9: Thank you for your suggestion. We have corrected reference 2.

Comments 10: Table 1 Separate the number of survey sites into separate columns for each year

Response 10: Thank you for your suggestion. We separated the number of survey sites into separate columns for each year.

Table 1. O. decorus nymphs/m² and their density levels.

Species density/m2	Number of survey sites			Cumulative survey sites
	2018	2019	2020
[0,8)	9	9	4	22
[8,15)	23	1	2	26
[15,22)	0	1	19	20
[22,30)	10	2	0	12
[30,45)	7	1	2	10
[45,60)	1	3	5	9
[60,90)	0	2	1	3
[90,150)	0	5	0	5

 

Comments 11: Discussion

In general, the Discussion is simply a repetition of the Results and does not interpret the findings, indicate what is novel about the study, review the sources of error and other caveats, or compare and contrast the results with previous findings. Because of the problems with lack of spatial and temporal independence of the data in the analyses, the authors have to be very clear that their analyses and conclusions are limited by that fact.

‘Therefore, we can conclude that O. decorus densities are significantly correlated with SM in the oviposition period, as well as with LST and SM during the early overwintering period [21,30].’  Conclusion based on 3 years of data. That's an important caveat.

‘However, when L6 is greater than 36.8 °C, the opposite effect is observed. When L6 is higher than 39.8 °C, LST no longer remains the decisive factor.’ This description of the effect of L6 is very confusing. The increase in density with L6 is based on a single point. What does it mean that it’s no longer the ‘decisive factor’ when L6 is greater than 39.8 C?

‘Similar results were obtained from the response of diverse O. decorus densities to daily SM and LST’ Can the authors explain how the results from the daily SM and LST values were similar to the trends of hopper density with the mean SM and LST values?

‘vegetation type, vegetation coverage, geographic and geomorphic conditions, and grasshopper abundance’  It’s not clear what you mean by abundance. Do you mean 'grasshopper abundances in previous years' or 'abundances in nearby sites'?

Response 10: Thank you for your comments and suggestions. Based on your ideas, we are rewriting the discussion section.

“4.1. Role of Environmental Factors in GAM

Grasshoppers are ectothermic insects that directly rely on suitable conditions for oviposition, overwintering, incubation, and development [30,40]. Climate factors, especially precipitation and temperature, are the major determinants of grasshopper occurrence [9,41]. Changes in precipitation and temperature significantly influence SM content, which in turn affects grasshopper abundance [22,42]. In this study, SM and LST datasets were applied as environmental factors to analyze and discuss their effects on different O. decorus density levels. All factors showed significant association (p < 0.05) with O. decorus populations in the model (Table 3). The factor with the largest contribution was L8 with an F-value of 27.422. This confirms that SM content in the previous summer directly affects the spatial distribution of O. decorus population density [15].

4.2. Influence of Environmental Factors on O. decorus Density

The grasshopper plague outbreak is a complex process influenced by various environmental factors, including vegetation, soil, precipitation, temperature, and terrain conditions [43]. SM and LST are particularly key factors that directly or indirectly affect the selection of oviposition sites, the survival of eggs, and the reproduction rates in subsequent generations [7,44]. However, there is death of research focusing on the relationship between SM/LST and O. decorus density. In this study, we have identified the key factors of SM/LST that determine the density of O. decorus. Interestingly, there are considerable seasonal variations in the effects of LST and SM on the density of O. decorus. In August and September, SM is a primary factor influencing the selection of oviposition sites. Meanwhile, LST primarily affects the eggs overwintering and incubation of eggs.

We analyzed the relationship between the density of O. decorus and six primary environmental factors on a monthly basis using GAM in section 3.3. S8 is a key factor determining the selection of spawning sites and the number of eggs laid by O. decorus. The higher the SM content in August of the previous year, the lower the density of O. decorus (Figure 3a). The negative correlation between S8 and O. decorus density may be explained by water content in the soil beyond the species’ optimal range, which reduces the spawning or prevents oviposition [17]. Because grasshoppers require a suitable soil environment for laying their eggs [45]. Another vital factor of SM influencing O. decorus density is S9. The number of O. decorus shows a fluctuating increase with the increase of S9. However, we can find that O. decorus density rapidly declined when S9 greater than 0.29 m3/m3. As with other grasshoppers around the world, O. decorus density begins to rapidly decline when SM exceeds a certain threshold [46]. This indicates that abundant SM has adverse impacts on O. decorus occurrence. SM in early autumn can impact egg preservation, thereby avoiding water loss from eggs and increasing the survival of eggs during overwintering [44]. Higher water content in the soil during the egg stage could favor natural enemies, such as parasites, fungi, and bacteria, of O. decorus. This could indirectly affect the eggs, resulting in decreased survival or reproduction rates [15,29].

Another prior-year factor significantly affecting O. decorus density is LST (L10) in October. Under low temperature conditions (L10 < 19 °C), the increase of temperature promotes the increase of O. decorus population. However, this growth trend of grasshopper density gradually slows down when L10 exceeds 19 °C. This result indicates that higher temperatures in early winter, specifically in October, can enhance the overwintering rate of grasshopper eggs. Previous studies have also found that the mean temperatures of the coldest quarter influence the distribution of grasshoppers [22,47]. With the increasing temperatures across the globe, warmer winters are becoming more common. This trend promotes a higher survival rate of eggs and enhances the reproductive capabilities of grasshoppers in the next generation, leading to an increased risk of grasshopper plague outbreaks [48].

In spring, LST is the main environmental factor affecting the density of O. decorus. LST exhibits a negative correlation with O. decorus density in March. It can be inferred from this result that higher temperatures in March may pre-incubate the eggs. However, late spring often experiences cold spells in Inner Mongolia. This phenomenon may lead to the termination of egg development or the death of nymphs of O. decorus. Interestingly, as the LST rises in May, O. decorus density first increases and then decreases or levels off. L6 is another crucial variable directly influencing the incubation of O. decorus, exhibiting a considerably non-linear relationship with O. decorus density. These results suggest that O. decorus density is greatly correlated with the changes of LST. And many studies confirmed that higher temperatures and drought in early summer can increase the population density of O. decorus [49,50]. These results verify that the eggs of O. decorus require specific soil conditions, and higher temperature could lead to soil desiccation, thus reducing the survivability of eggs.

To gain a deeper understanding of the relationship between the population density levels of O. decorus and six environmental factors, the average daily SM and LST at different density levels of O. decorus were calculated in section 3.4. Nevertheless, comparing the response of grasshoppers at low-density levels (< 30 nymphs/m2) and high-density levels (≥ 30 nymphs/m2) to SM content in Figure 4a, the values of L8 and L9 are lower at low-density levels than at high density levels. Up to 30 nymphs/m2, an increase of SM content would reduce the grasshopper population. Beyond this, an increase in SM would promote the density growth of O. decorus. Therefore, the O. decorus population density of 30 nymphs/m2 is believed to be a very important inflection point. Accordingly, sites with relatively high SM levels are suggested to have abundant food, which would attract a large number of adult O. decorus to lay eggs [51]. It may be worth analyzing and discussing this inflection point to further clarify the influence of SM content on grasshopper population.

4.3. Recommendations for O. decorus Prediction and Monitoring

The results confirm that SM and LST are considerably correlated with O. decorus population density, especially SM in August, which can be used to predict and monitor the dynamic distribution of O. decorus density. Nevertheless, grasshopper infestation is a complex process affected by other factors such as vegetation conditions, climatic factors, geographic and geomorphic conditions, and grasshopper abundance [14,24,50]. Therefore, in order to accurately monitor and predict dynamic changes in O. decorus density, comprehensive models should be established by integrating more source datasets, including vegetation, soil, meteorological, and geographic conditions. Furthermore, utilizing remote sensing data, big data, and artificial intelligence to predict outbreak areas and enhance real-time monitoring capabilities will become a primary method [52].

Unfortunately, our study, which is based on 3 years of monitoring (2018–2020), observed considerable correlations between the densities of O. decorus and SM/LST. While our findings are valid within the study period, the 3-year timeframe does not adequately capture fluctuations, such as droughts or heatwaves, that could alter the relationship between SM and LST. Therefore, longer-term studies are necessary to assess the robustness of these patterns under climate variability in future research.”

 

Once again, we thank you for all your comments and suggestions. We greatly appreciate these valuable comments and suggestions which have helped us improve the manuscript and helped me learn a lot. Thank you!

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

Plagiarism is too.much.

Author Response

Dear reviewer:

We sincerely appreciate your feedback regarding the similarity issue. Upon checking, we found that the high similarity score partially stems from our preprint version. We apologize for not clarifying this during the submission process. But we confirm that this paper has not been officially published in other magazines.
Thank you for your.
We guarantee that the final manuscript meets the journal’s originality standards. Should the reviewer identify any remaining concerns, we are happy to make further revisions.

Reviewer 3 Report

Comments and Suggestions for Authors

For the Authors:

Thank you to the authors for the rapid turnaround and addressing my comments. I think the authors have done a nice job of addressing them, and provided suitable explanations when they did not. I have the following comments on this draft.

 

1. 66 ‘not trigger egg laying’ is awkward. What about ‘inhibit egg laying’

 

Figure 2 legend   Please explain the numbers above and below the plots, and to the left and right. Is that what you mean by 'variates'? Typically the x-axis would be left and right, and the y-axis above and below, but you have written the opposite: ‘where the x-axis and y-axis are the variates of environmental factors above or 194 below, and left and right, respectively.’ Please check that your statement is accurate.

 

1. 321 Change ‘is death of research’ to ‘a dearth of research’

 

9. 333 The phrase beginning with Because is not a complete sentence. I believe the phrase is meant to be a part of the sentence that follows. If so, rewrite it as ‘Because grasshoppers require a suitable soil environment for laying their eggs [45], another vital factor of SM influencing O. decorus density was S9.’

 

1. 378-379 I’m not sure what the authors mean to say here, but the sentence might be better stated 'Further investigation of this inflection point to clarify the influence of SM content on grasshopper populations is warranted.'

 

1. 381 I think here the word 'significantly' is better than 'considerably' in this sentence.

 

Reference list. The numbers are repeated. Once as ‘1.’ and then again in brackets [1]. This should be fixed to fit the format of the journal.

 

1. 466 Reference [20] is incomplete. Is it a Master’s thesis? Please complete the reference.

 

Author Response

Thank you very much for your comments and suggestions. We have studied your suggestions carefully and made the following changes. We hope our responses will satisfy you.

 

Comments 1: 66 ‘not trigger egg laying’ is awkward. What about ‘inhibit egg laying’

Response 1: Thank you for your comment. This is a good suggestion We have change ‘not trigger egg laying’ as ‘inhibit egg laying’.

Comments 2: Figure 2 legend   Please explain the numbers above and below the plots, and to the left and right. Is that what you mean by 'variates'? Typically the x-axis would be left and right, and the y-axis above and below, but you have written the opposite: ‘where the x-axis and y-axis are the variates of environmental factors above or 194 below, and left and right, respectively.’ Please check that your statement is accurate.

Response 2: We appreciate the reviewer’s careful reading. We have revised the figure caption to: Histograms along the diagonal indicate the distribution of individual environmental factors. Scatter plots below the diagonal show the relationships between pairs of factors, with the x-axis (left to right) representing the variable of the factor on the left and the y-axis (top to bottom) representing the variable of the factor below. The numbers above the diagonal indicate the Pearson correlation coefficient and significance levels (*: P < 0.05, **: P < 0.01, ***: P < 0.001

Comments 3: 321 Change ‘is death of research’ to ‘a dearth of research’

Response 3: Thank you for your suggestions. The sentence has been revised to "a dearth of research" as suggested. We appreciate the reviewer’s attention to detail.

Comments 4: 333 The phrase beginning with Because is not a complete sentence. I believe the phrase is meant to be a part of the sentence that follows. If so, rewrite it as ‘Because grasshoppers require a suitable soil environment for laying their eggs [45], another vital factor of SM influencing O. decorus density was S9.’

Response 3: We thank the reviewer for pointing out this grammatical error. As suggested, we have merged the “Because grasshoppers require a suitable soil environment for laying their eggs, another vital factor of SM influencing O. decorus density is S9.”

Comments 4: 378-379 I’m not sure what the authors mean to say here, but the sentence might be better stated 'Further investigation of this inflection point to clarify the influence of SM content on grasshopper populations is warranted.'

Response 4: We sincerely appreciate your constructive suggestion. We have revised the sentence according to your recommendation to more clearly express the need for further investigation of this inflection point. The modified text now reads: Further investigation into this inflection point is warranted to clarify the influence of SM content on grasshopper populations.

Comments 5: 381 I think here the word 'significantly' is better than 'considerably' in this sentence.

Response 5: Thank you for your suggestions. We have changed 'considerably' to ‘significantly’.

Comments 6: Reference list. The numbers are repeated. Once as ‘1.’ and then again in brackets [1]. This should be fixed to fit the format of the journal.

Response 6: Thank you for catching this formatting issue. We have now standardized all references in the list to follow the journal's required citation style, removing the duplicate numbering. The reference section has been thoroughly checked to ensure full consistency with the journal guidelines.

Comments 7: 466 Reference [20] is incomplete. Is it a Master’s thesis? Please complete the reference.

Response 7: Thank you for your suggestions. This is a Master’s thesis.

Once again, we thank you for your affirmants and suggestions. We greatly appreciate these valuable comments and suggestions which have helped us improve the manuscript and helped me learn a lot. Thank you!