Estimating Leymus chinensis Loss Caused by Oedaleus decorus asiaticus Using an Unmanned Aerial Vehicle (UAV)
and Ning Wang 1,2,3,*Round 1
Reviewer 1 Report
Introduction
Lines 1, 2. Please rewrite sentence:
Grasshoppers play an important roles in grassland ecosystems, playing a significance role in nutrient cycling and energy flow of the ecosystem.
Line 54. Oedaleus decorus (Germar).
Note that Oedaleus decorus asiaticus Bey-Bienko is now a synonymy of Oedaleus decorus (Germar).
Authors must be consistent in naming the grasshopper throughout the manuscript: sometimes they use Oedaleus decorus asiaticus, others Oedaleus asiaticus, and sometimes Oedaleus decorus…
Also, note that you provide a first time the full species name and author (s) in the Introduction and subsequently you may use O. decorus only.
Please use nymph, nymphs, nympal, instead of larvae, larval, etc., throughout the manuscript.
Additional comments on manuscript
Results
From Line 10 to 21, is there any statistical analyses to support these data and significant differences?
3.2. Variation characteristics of vegetation indices attributable to Oedaleus asiaticus
From Lines 9 to 21, can you provide a statistical analysis to support the variation and significant differences?
Discussion, improve last paragraph, comments on manuscript.
Comments for author File: 
Comments.pdf
The article needs proofreading by an English Proof Reading Service
Author Response
Response to Reviewer 1 Comments
Thank you very much for your comments and suggestions. Your useful feedback has helped us to improve our paper substantially. We hope our responses address your concerns.
Point 1: Please rewrite sentence:”Grasshoppers play an important roles in grassland ecosystems, playing a significance role in nutrient cycling and energy flow of the ecosystem.”
Response 1: Grasshoppers play an important role in grassland ecosystems as well as in nutrient cycling and the energy flow of the ecosystem
Point 2: Line 54. Oedaleus decorus (Germar). Note that Oedaleus decorus asiaticus Bey-Bienko is now a synonymy of Oedaleus decorus (Germar). Authors must be consistent in naming the grasshopper throughout the manuscript: sometimes they use Oedaleus decorus asiaticus, others Oedaleus asiaticus, and sometimes Oedaleus decorus…
Also, note that you provide a first time the full species name and author (s) in the Introduction and subsequently you may use O. decorus only.
Response 2: We consisted the grasshopper name as Oedaleus decorus asiaticus Bey-Bienko. After the first full species name was provided, O. decorus was used for Oedaleus decorus asiaticus Bey-Bienko.
Point 3: Please use nymph, nymphs, nympal, instead of larvae, larval, etc., throughout the manuscript.
Response 3: Thank you very much for your good suggestion. We replaced larvae with nymphs or nymphal.
Point 4: From Line 10 to 21, is there any statistical analyses to support these data and significant differences?
Response 4: As can be seen from Figure 4, these vegetation indices vary widely.
Point 5: Discussion, improve last paragraph, comments on manuscript.
Response 6: Yes we have improve the last paragraph.
Once again we thank you for your all comments and suggests and we hope you will find our revision satisfactory for publication in Remote Sensing.
Author Response File: 
Author Response.doc
Reviewer 2 Report
Du et al. present a paper focusing on the capability of UAV-based multi-spectral data for estimating plant loss caused by Oedaleus asiaticus in different growth stages. The authors demonstrates the potential of spectral vegetation indices and several models for the detection of Oedaleus asiaticus damage. Field experiments are very interesting, however, there are a number of questions in this analysis, some key issues need to be clarified.
In this study, eight density levels were designed, comprising 0, 8, 15, 22, 30, 45, 60, and 90 Oedaleus asiaticus nymphs/m2 with three replicates per level. In Figure 1C, the density levels gradually increases from left to right. Is Leymus chinensis evenly distributed? Would it be better for Oedaleus asiaticus cages with different density levels to be randomly distributed.
Is there a standard basis for the author to set different density levels (0, 8, 15, 22, 30, 45, 60, and 90 nymphs/m2)? Or do you set it yourself? What is the general density in real grasslands?
In Figure 1, please add clear photos of the cage so that readers can see the specific situation of the Leymus chinensis and Oedaleus asiaticus in the cage clearly.
I am curious about how many Oedaleus asiaticus escape during the process of removing all the cages, collecting UAV images, and then moving back the cages?
The author wrote in the article that the number will be counted, and if any nymphs die or escape, they will be added to the corresponding cages. What is the inspection frequency? Every day?
My biggest concern though is the description of results and discussion. The author only provided a brief description without in-depth analysis. The author compared the differences in vegetation indices between different experimental groups. For detail, it is unreasonable for the author to directly describe the significant differences between different experimental groups without conducting an analysis of variance.
In Figure 5, please add standard error in each histogram.
The author listed the calculation formula for LVIs in the article, but I did not see any analysis of the results related to LVIs in the subsequent results.
According to the equation of nymph density and RVI in the second instar larval stage, low nymph density (less than 60 nymphs/m2 ) would promote the growth of Leymus chinensis. I don't quite understand how the author acquire this conclusion? Is the growth of Leymus chinensis with low nymph density (less than 60 nymphs/m2) significantly higher than that with low nymph density (0 nymphs/m2)? I am not very familiar with Leymus chinensis. Is it in the growing season From June 19 to July 12？
From June 28 to July 3, in cages with a density level of 30 nymphs/m2 , even negative growth was observed. Has the author considered the reasons for such a result? Will there be large difference or outlier in the group due to too few duplicates？
“Locusta migratoria manilensis, Calliptamus abbreviates, Oedaleus decorus asiaticus, etc” in the reference were not italics. The author needs to check whether the Latin names in the paper are all italicized.
The authors do have the right data for an interesting paper, but my suggestion is a re-analysis and reframing of the results. According to the change of vegetation index with nymph density (0 nymphs/m2) as a reference, the author can detrend the time series of spectral index of other treatment groups to obtain the true change value of vegetation index, which is conducive to the result analysis.
Author Response
Response to Reviewer 2 Comments
Thank you very much for your comments and suggestions. Your useful feedback has helped us to improve our paper substantially. We hope our responses address your concerns.
Point 1: In this study, eight density levels were designed, comprising 0, 8, 15, 22, 30, 45, 60, and 90 Oedaleus asiaticus nymphs/m2 with three replicates per level. In Figure 1C, the density levels gradually increases from left to right. Is Leymus chinensis evenly distributed? Would it be better for Oedaleus asiaticus cages with different density levels to be randomly distributed.
Response 1: Yes, we selected an area where the Leymus chinensis is evently distributed. According to 9 vegetation indices derived from muti-spectral images on June 19, there was little difference among the cages.
Point 2: Is there a standard basis for the author to set different density levels (0, 8, 15, 22, 30, 45, 60, and 90 nymphs/m2)? Or do you set it yourself? What is the general density in real grasslands?
Response 2: We did set different density levels (0, 8, 15, 22, 30, 45, 60, and 90 nymphs/m2) refer of the paper “Estimating reed loss caused by Locusta migratoria manilensis using UAVbased hyperspectral data” and “Monitoring Locusta migratoria manilensis damage using ground level hyperspectral data ”. In addition, we also considered the control density. In General, when the density of O.decorus was greater than 15 nymphs/m2, the grassland protectors began to contral.
Point 3: In Figure 1, please add clear photos of the cage so that readers can see the specific situation of the Leymus chinensis and Oedaleus asiaticus in the cage clearly.
Response 3: We are very sorry for this question. In this study, the UAV equiped with MS600pro camera was used to take the date. Unfortunately, we did not collect any clear photos for each cage. But we took work photos during the study.
Point 4: I am curious about how many Oedaleus asiaticus escape during the process of removing all the cages, collecting UAV images, and then moving back the cages?
Response 4: This is an interesting question. We did capture the Oedaleus asiaticus in each cage before this process. Only a few Oedaleus asiaticus escaped.
Point 5: The author wrote in the article that the number will be counted, and if any nymphs die or escape, they will be added to the corresponding cages. What is the inspection frequency? Every day?
Response 5: Twice a day.
Point 6: In Figure 5, please add standard error in each histogram.
Response 6: Yes, we added standard error in each histogram.
Point 7: The author listed the calculation formula for LVIs in the article, but I did not see any analysis of the results related to LVIs in the subsequent results.
Response 7: The formula of LVIs was used in the section “3.3. Relationship between the loss component of Leymus chinensis and the density level of O.decorus”. And the related relevant were analyzed.
Point 8: According to the equation of nymph density and RVI in the second instar larval stage, low nymph density (less than 60 nymphs/m2 ) would promote the growth of Leymus chinensis. I don't quite understand how the author acquire this conclusion? Is the growth of Leymus chinensis with low nymph density (less than 60 nymphs/m2) significantly higher than that with low nymph density (0 nymphs/m2)? I am not very familiar with Leymus chinensis. Is it in the growing season From June 19 to July 12？
Response 8: The curve characteristic of equation of nymph density and RVI in the second larval stage exhibit that vegetation index (RVI) increased with the increase of the nymphs number (nymph density ≥ 30 nymphs/m2). while the nymph density exceeded 60 nymphs/m2, RVI showed a negative growth.
In the northern hemisphere,vegetation grows from June 19 to July 12.
Point 9: From June 28 to July 3, in cages with a density level of 30 nymphs/m2 , even negative growth was observed. Has the author considered the reasons for such a result? Will there be large difference or outlier in the group due to too few duplicates？
Response 9: During this periods from June 28 to July 3, the growth rate of vegetation index become slower. In cages with a density level of 30 nymphs/m2 , even negative growth was observed. We suspected that nymphs in cages with a density of 30 nymphs/m2 were more active and eat more. However, we could not analysis in detail because further experiments are needed.
Point 10: “Locusta migratoria manilensis, Calliptamus abbreviates, Oedaleus decorus asiaticus, etc” in the reference were not italics. The author needs to check whether the Latin names in the paper are all italicized.
Response 10: Yes, we did check the Latin names in the paper.
Point 11: The authors do have the right data for an interesting paper, but my suggestion is a re-analysis and reframing of the results. According to the change of vegetation index with nymph density (0 nymphs/m2) as a reference, the author can detrend the time series of spectral index of other treatment groups to obtain the true change value of vegetation index, which is conducive to the result analysis.
Response 11: This is a good idea. We had attempted to detrend the time series of spectral index, but the results is not satisfactory.
Once again we thank you for your all comments and suggests and we hope you will find our revision satisfactory for publication in Remote Sensing.
Author Response File: Author Response.doc
Reviewer 3 Report
Very interesting the paper, we have the following considerations:
Page 2, replace Oedaleus decorus asiaticus (B.-Bienko) with Oedaleus decorus asiaticus (Bey Bienko, 1941) (Orthoptera: Acrididae).
Page 3,
Replace
“The UAV system in the study comprised Matrice 300 RTK drone and MS600 Pro cam-era for spectral data collection (Figure 2). The Matrice 300 RTK drone was developed by Da-Jiang innovation Science and Technology Company in China. Matrice 300 RTK drone is a quadrocopter equipped with a GPS and Inertial Measurement Unit (IMU), with a flight time of more than 35 min when equipped with the MS600 Pro camera. The MS600 Pro camera is a multi-spectral sensor developed by Yusense Information Technology and Equipment Incorporated in China. This camera contains 6 spectral bands including red, green, blue, red-edge1, near-infrared, and red-edge2 wavebands. In this study, the camera was used to collect spectral data within the cage at difference growth stages with various density levels of Oedaleus asiaticus.”
With
“The UAV system in the study comprised Matrice 300 RTK drone (Da-Jiang innovation Science and Technology Company, Shenzhen, Guangdong, China) and MS600 Pro camera (Yusense Information Technology and Equipment Incorporated Company, Qingdao, Shandong, China) for spectral data collection (Figure 2). Matrice 300 RTK drone is a quadrocopter equipped with a GPS and Inertial Measurement Unit (IMU), with a flight time of more than 35 min when equipped with the MS600 Pro camera. The MS600 Pro camera is a multi-spectral and contains 6 spectral bands including red, green, blue, red-edge1, near-infrared, and red-edge2 wavebands. In this study, the camera was used to collect spectral data within the cage at difference growth stages with various density levels of Oedaleus asiaticus.”
Figure 2, As a suggestion, the figure 2 could be deleted and the bands described in the text as follows: Blue (450 nm center, 35 nm bandwidth), etc.
Figura 3, The figure could be complemented with the approximate period, in days, for each growth stag.
Page 5, To correct http://mapupdate.yusense.com.cn:9092)
3.1. Response of plant vegetation indices to Oedaleus asiaticus invasions,
In this item, the analysis carried out in which significant differences were found could be better explained (perhaps a table could be used to complement Figure 4)
Figure 5, The figure can be enlarged for better viewing.
Table 2, The table is broken without proper identification. Improve layout.
4. Discussion,
In this item it is mentioned that there was no significant difference in biomass. Have these results been presented? Was the biomass evaluated? Or was it estimated from vegetation indices? In this case, what was the procedure for this estimate?
5. Conclusions, It is consistent with the proposed objectives.
Author Response
Response to Reviewer 3 Comments
Thank you very much for your comments and suggestions. Your useful feedback has helped us to improve our paper substantially. We hope our responses address your concerns.
Point 1: Page 2, replace Oedaleus decorus asiaticus (B.-Bienko) with Oedaleus decorus asiaticus (Bey Bienko, 1941) (Orthoptera: Acrididae).
Response 1: Thank you very much for your good suggestion. We had replaced Oedaleus decorus asiaticus (B.-Bienko) with Oedaleus decorus asiaticus (Bey Bienko, 1941)
Point 2: Page 3,Replace“The UAV system in the study comprised Matrice 300 RTK drone and MS600 Pro cam-era for spectral data collection (Figure 2). The Matrice 300 RTK drone was developed by Da-Jiang innovation Science and Technology Company in China. Matrice 300 RTK drone is a quadrocopter equipped with a GPS and Inertial Measurement Unit (IMU), with a flight time of more than 35 min when equipped with the MS600 Pro camera. The MS600 Pro camera is a multi-spectral sensor developed by Yusense Information Technology and Equipment Incorporated in China. This camera contains 6 spectral bands including red, green, blue, red-edge1, near-infrared, and red-edge2 wavebands. In this study, the camera was used to collect spectral data within the cage at difference growth stages with various density levels of Oedaleus asiaticus.”
With
“The UAV system in the study comprised Matrice 300 RTK drone (Da-Jiang innovation Science and Technology Company, Shenzhen, Guangdong, China) and MS600 Pro camera (Yusense Information Technology and Equipment Incorporated Company, Qingdao, Shandong, China) for spectral data collection (Figure 2). Matrice 300 RTK drone is a quadrocopter equipped with a GPS and Inertial Measurement Unit (IMU), with a flight time of more than 35 min when equipped with the MS600 Pro camera. The MS600 Pro camera is a multi-spectral and contains 6 spectral bands including red, green, blue, red-edge1, near-infrared, and red-edge2 wavebands. In this study, the camera was used to collect spectral data within the cage at difference growth stages with various density levels of Oedaleus asiaticus.”
Response 2: Thank you very much for your all comments and suggestions. We had replaced.
Point 3: Figure 2, As a suggestion, the figure 2 could be deleted and the bands described in the text as follows: Blue (450 nm center, 35 nm bandwidth), etc.
Response 3: Thank you very much for your good suggestion. But we think figure 2 can be preserved. It exhibited the process of taken data by UAV. We had replaced “wavelength” with “central wavelength”.
Point 4: Page 5, To correct http://mapupdate.yusense.com.cn:9092)
Response 4: We had checked out the link of “http://mapupdate.yusense.com.cn:9092”. Under this page, we can download Yusense Map software.
Point 5: Figure 5, The figure can be enlarged for better viewing.
Response 5: Yes, we had redrawn the Figure 5.
Point 6: Table 2, The table is broken without proper identification. Improve layout.
Response 6: We rearranged Table 2.
Point 7: In this item it is mentioned that there was no significant difference in biomass. Have these results been presented? Was the biomass evaluated? Or was it estimated from vegetation indices? In this case, what was the procedure for this estimate?
Response 7: Sorry editor, we did not estimate any biomass. “In this item it is mentioned that there was no significant difference in biomass” is a mistake. And we replaced biomiss with VIs.
Once again we thank you for your all comments and suggests and we hope you will find our revision satisfactory for publication in Remote Sensing.
Author Response File: Author Response.doc
Round 2
Reviewer 2 Report
The manuscript entitled “Estimating Leymus chinensis loss caused by Oedaleus decorus asiaticus using unmanned aerial vehicles (UAV)” submitted to Remote sensing. I agreed that this method useful to estimate Leymus chinensis loss caused by Oedaleus decorus asiaticus. The authors have made a lot of efforts to supplement most of the questions. However, I’d like to make several questions about the data analysis.
In the section 3.3 “The growth rate of NDVI became slower than that in the last stage. In cages with a density level of 30 nymphs/m2 , even negative growth was observed. ”
In Figure 5, I checked several times and found a density level of 22 nymphs/m2
showed negative growth, rather than density level of 30 nymphs/m2. Please confirm again. Similarly, please confirm “From June 28 to July 3 (third instar nymphs larvae), most of the cages showed an increasing trend in GCVI, which was lower than before. Only cages with a density level of 30 nymphs/m2 showed negative growth.” in the section 3.3.
The author missed an question from the previous review “The author compared the differences in vegetation indices between different experimental groups. For detail, it is unreasonable for the author to directly describe the significant differences between different experimental groups without conducting an analysis of variance.” Here, I still suggest that the author conduct an analysis of variance between different density levels, and added the results in Figure 5. It better reflects the differences in feeding ability of different density level at different instar nymphal stage.
Author Response
Response to Reviewer 2 Comments
Thank you very much for your comments and suggestions. Your useful feedback has helped us to improve our paper substantially. We hope our responses address your concerns.
Point 1: In the section 3.2 “The growth rate of NDVI became slower than that in the last stage. In cages with a density level of 30 nymphs/m2 , even negative growth was observed. ”
In Figure 5, I checked several times and found a density level of 22 nymphs/m2
showed negative growth, rather than density level of 30 nymphs/m2. Please confirm again. Similarly, please confirm “From June 28 to July 3 (third instar nymphs larvae), most of the cages showed an increasing trend in GCVI, which was lower than before. Only cages with a density level of 30 nymphs/m2 showed negative growth.” in the section 3.3.
Response 1: Thank you very much for your question. We replaced 30 nymphs/m2 with 22 nymphs/m2.
Point 2: The author missed an question from the previous review “The author compared the differences in vegetation indices between different experimental groups. For detail, it is unreasonable for the author to directly describe the significant differences between different experimental groups without conducting an analysis of variance.” Here, I still suggest that the author conduct an analysis of variance between different density levels, and added the results in Figure 5. It better reflects the differences in feeding ability of different density level at different instar nymphal stage.
Response 2: Dear reviewer, thank you very much for your good idea. We know this is a good suggestion. And we attempted to conduct an analysis of variance when we processed those data. But the significance is not obvious. So we could not conduct this analysis and not add the results in Figure 5. Fortunately, the average data exhibited a great difference between difference experimental groups. We are very sorry for not being able to conduct ANOVA.
Once again we thank you for your all comments and suggests and we hope you will find our revision satisfactory for publication in Remote Sensing.
Author Response File: Author Response.doc
