Mapping Maize Cultivated Area Combining MODIS EVI Time Series and the Spatial Variations of Phenology over Huanghuaihai Plain
Round 1
Reviewer 1 Report
The revision has been made regarding the file applsci-737739-peer-review-v1.pdf.
Thank you for giving me the opportunity to review the manuscript:
Manuscript ID: applsci-737739
Type of manuscript: Article
Title: Mapping maize cultivated area combining MODIS EVI time series and the spatial variations of phenology over Huanghuaihai Plain
General comments:
The paper is well structured and written clear for a not specialized reader.
The manuscript studies the phenology of summer maize cultivation on the Huanghuaihai Plain using images of the MODIS sensor.
Apart addition to the local interest in analyzing the temporal shift of summer maize calendars, their spatial distribution in the different regions is also studied so the subject of the study is interesting.
Great efforts by the authors!.
Please consider few observations and suggestions:
It is recommended that authors follow the rules described in the applied sciences specification guide for the paper figures (https://www.mdpi.com/journal/applsci/instructions#authorship)
Encourage authors to share the research data by uploading to cloud repositories giving free access to use to other researches
Abstract. In the abstract Huanghuaihai is mentioned but it is not located in region or country.
- The abstract contains more than 200 words. See "instructions for authors" of the journal ( https://www.mdpi.com/journal/applsci/instructions).
Section 2.1. Study area and reference área.
- It is recommended to authors the figures be located after their citation in the text
- For the not specialized reader, the location of the Huanghuaihai Plain is unknown, so it is recommended to redo figure 1 of the study área
- Where is the Ruzhou City (figure 1)?
Section 2.2.3. Land use data
- The link http://www.globallandcover.com/ does not work
Section 2.2.4. Phenological and meteorological data
- It is recommended to authors the tables be located after their citation in the text
- It is recommended to authors to cite in the Figure 1 the agro-climatic stations as mentioned in the text: "The location of agro-meteorological stations is shown in Figure 1, and the phenological information is listed in Table 1 "
Section 2.2.5. Statistical data
- The use of MODIS sensor images (2012) such as Landsat (2012), the statistics collected of production on summer maize (2013) and phenology observation data (2007-2012) are not updated. Why this selection of dates? Couldn't the study be done with more current data?. Why the study has not been extended beyond 2012?
Section 3.1. Method of maize area identification in the reference área
Line 4. error in the term “phonological”: “By surveying the phonological characteristics…”.
Section 4.2.1. Estimation of summer maize phenology
Line 126. It is recommended to authors the figures be located after their citation in the text (figure 6).
Section 4.3.1. The MAD between standard summer maize EVI and actual MODIS EVI
Line 172. It is recommended to authors the figures be located after their citation in the text (figure 8). Error in the cite of figure 7: “The MAD map of the study area is shown in Figure 8…”
Section 4.3.2. Extraction results of summer maize in Huanghuaihai Plain
Line 183. Error in “Huanghuaihai Plian”
Section 4.3.3. Verification of the extracted summer maize area in Huanghuaihai Plain
Line 217. The cite to figure 9 is not found in the text
Section 4.3.4. Extraction results in different years
- The cite of figure 10 and the cite to table 8 are not found in the text
Conclusion:
The data and analysis fully support the claims. The principal sentences described in the paper are appreciated and allow the description on new advanced techniques for mapping summer maize cultivated area over a large scale.
Encourage authors to share the research data by uploading to cloud repositories giving free access to use to other researches
It is recommended that authors follow the rules described in the applied sciences specification guide for the paper figures (https://www.mdpi.com/journal/applsci/instructions#authorship)
Kind regards,
Author Response
Point 1: It is recommended that authors follow the rules described in the applied sciences specification guide for the paper figures (https://www.mdpi.com/journal/applsci/instructions #authorship)
Response 1: According to the requirements of the author's guide in this journal, revise the picture again.
Point 2: Abstract. In the abstract Huanghuaihai is mentioned but it is not located in region or country.The abstract contains more than 200 words. See "instructions for authors" of the journal ( https://www.mdpi.com/journal/applsci/instructions).
Response 2: The abstract has been modified to be less than 200 words.
Point 3: Section 2.1. Study area and reference área.
It is recommended to authors the figures be located after their citation in the text
For the not specialized reader, the location of the Huanghuaihai Plain is unknown, so it is recommended to redo figure 1 of the study área. Where is the Ruzhou City (figure 1)?.
Response 3: Figure 1 has been modified and shown in the manuscript.
Point 4: Section 2.2.3. Land use data
The link http://www.globallandcover.com/ does not work
Response 4: The right link is (Globeland30, http://www.globallandcover.com/GLC30Download/index.aspx).
Point 5: Section 2.2.5. Statistical data
The use of MODIS sensor images (2012) such as Landsat (2012), the statistics collected of production on summer maize (2013) and phenology observation data (2007-2012) are not updated. Why this selection of dates? Couldn't the study be done with more current data?. Why the study has not been extended beyond 2012?. In the abstract Huanghuaihai is mentioned but it is not located in region or country.
Response 5: Because the phenological data of crops from 2013 to 2019 are incomplete, it is not easy to study. The phenological data before 2012 is complete, so it has not been extended beyond 2012.
Point 6: Issues with typos and improper location of figures
Response 6: Issues with typos and improper location of figures have been corrected in the article.
Author Response File: 
Author Response.docx
Reviewer 2 Report
Comments to author:
Since the line number starts from figure 2 on the present document, the following comments are according to the line number:
In line 64, delete 5.
In Line 131, delete the extra space between the and maturation
In Line 133, rephrase the sentence “Summer generally high temperature” to make grammatically correct.
In line 172, change figure 8 to figure 7
In line 174, change One to On
In line 182, change Figure8 to Figure 8
In line 183, add space between “andsouthern”
In line 188, change where to which
In the section of Results and Discussion, very limited discussion is made on comparing the present study with previous study (Line 231 to 215 and Table7). Additional discussion is required to compare the significance of present with previous work been done on mapping crop area using various remote sensing tools and approaches.
Author Response
Point 1: Spelling and grammar errors.
Response 1: Spelling and grammar errors have been corrected in manuscript.
Point 2: In the section of Results and Discussion, very limited discussion is made on comparing the present study with previous study (Line 231 to 215 and Table7). Additional discussion is required to compare the significance of present with previous work been done on mapping crop area using various remote sensing tools and approaches.
Response 2: The article is further discussed and table 7 is described in detail as follows:
” Verification results of extracted summer maize areas through the approach in this study were compared with those of previous studies in Huanghuaihai Plain, , which the specific information was shown in Table 6. Liu Jun et al employed the method of integration of statistical analyses and remote sensing classification technique to extract summer maize cultivation areas in Huanghuaihai Plain from 2001 to 2010, comparing statistical data with estimated data, R2 ranged from 0.4977 to 0.6993 at city level. Validation results of extracted summer maize areas through combination of phenological differences and MODIS EVI time series curve showed that R2 reached 0.82 at city level, which was higher than those of extractions by Liu Jun et al at city level. Wang Hongying et al. extracted cultivation areas of summer maize in Huanghuaihai Plain through multi-temporal remote sensing images and phenological information without considering phenological changes of summer maize, and the results showed that R2 was 0.57, which was lower than those in this study at city level. When using multi temporal MODIS EVI time series curve to extract summer maize cultivation areas in Huanghuaihai Plain, extraction results with considerations of effects of latitude factor (Wang Xueting) and those of various environmental factors on phenology of Summer Maize were compared. Results showed that R2 of the two was equal at city level, both of which were 0.82. However, R2 of the latter was significantly higher than that of the former at city level. Provincial average accuracy of summer maize is 90.85% through consideration of effects of latitude factors on summer maize phenology, while provincial average accuracy is 92.63% through the method in this study. Compared with the previous researches that used the multi-temporal remote sensing images to map the summer maize area, the extraction accuracy was significantly improved in the current research”
Author Response File: Author Response.docx
Reviewer 3 Report
This research reached the sufficient accuracy of maize field mapping in China by the combination of Landsat, MODIS images and agricultural statics with phenological point of views.Focus on the EVI fluctuation and its precise analysis is interesting investigation and applicable even to other crops in other area. I got the positive feeling with such well-structured scenario. Just I expect the improvement for more clear distinguish of maize field from other crops such as peanut and cotton. I just worry about the phenology of these crops in the reference area and other area than reference area.
If the other crops has similar EVI fluctuation pattern but delayed or advanced, the similarity gives the error of maize field identification. The following is just my assumption, if peanut has similar pattern but advanced in the reference area, in addition, the phenology of peanut is uniform all over the study area, the peanut field in southern part will be identified as maize field.. I gave too much assumption, so that my worry should be flash by showing the EVI pattern of the other crops.
The difference from the other crops have to be discussed not only with figure 3. I expect EVI time series curve of the other crops, including the value of EVI.
your detail revision is required in the following points
- Page3 Figure 1. indication og blue and black line that trace the boundary of the city and province is not clear. Clear indication is expected
- Page8 lineNo.64 "5. Based on ETM+" => omit "5."
- Page8 lineNo.64 and later "hkm^2" is this unit common? hectare is common, if SI unit is used in this journal, ha is available in my understanding.
- page9 Figure 4 add "from ETM+"
- page10 lineNo.98 thirty-two Why not 32?
- page10 lineNo.113 multi-regression analysis was conducted with the data from 32 met.stations has already explained in the above line, linNo.98-99. compact them.
- page10 lineNo.113 I suspect the multicollinearity between the met and geographic parameters. I guess( x1 x4), (x2 x3 X5) have correlations .
- page12 lineNo.5 after "the difference in the", excess space
- page13 lineNo.174 One the contrary=>On the contrary
- page15 Figure 9 No need fitting lines
- page16 Figure 10 No need fitting lines
Author Response
Point 1: If the other crops has similar EVI fluctuation pattern but delayed or advanced, the similarity gives the error of maize field identification. The following is just my assumption, if peanut has similar pattern but advanced in the reference area, in addition, the phenology of peanut is uniform all over the study area, the peanut field in southern part will be identified as maize field.. I gave too much assumption, so that my worry should be flash by showing the EVI pattern of the other crops. The difference from the other crops have to be discussed not only with figure 3. I expect EVI time series curve of the other crops, including the value of EVI.
Response 1: It is a relatively mature technology to map different crops by using time series vegetation indexs (VIs) curve at present. The main purpose in this study is to improve the accuracy of extracting crops by combining MODIS EVI time series and the spatial variations of phenology. In my opinion, it is not necessary to show the EVI curve of other crops in this article.After reading my explanation, if you feel that there is still a problem with my opinion, I hope you can write to me. I will revise it.
Ms.Wang: e-mail: [email protected]
Point 2: page10 lineNo.113 I suspect the multicollinearity between the met and geographic parameters. I guess( X1 X4), (X2 X3 X5) have correlations .
Response 2: We introduced the advantages of stepwise regression analysis method. Stepwise regression analysis can not only establish “optimal” regression observations, but also overcome the multicollinearity to a certain extent..
Point 3: Detailed errors
Response 3: Detailed errors have been corrected in manuscript..
Author Response File: Author Response.docx
Reviewer 4 Report
Thanks very much authors for the research work. I have a few recommendations to enhance the quality and readability of the manuscript.
- I would like to see a detailed graph representing the output of table 3.
- I am okay with all other datasets, tables, graphs and results. However, the English language of the manuscript needs a thorough check. For example, line no. 241-243, this sentence requires a rewrite. Similarly, please scrutinize the entire manuscript as well.
Author Response
Point 1: I would like to see a detailed graph representing the output of table 3.
Response 1:We showed detailed graph representing the output of table 3 in manuscript.
Point 2: I am okay with all other datasets, tables, graphs and results. However, the English language of the manuscript needs a thorough check. For example, line no. 241-243, this sentence requires a rewrite. Similarly, please scrutinize the entire manuscript as well.
Response 2: I have revised the grammar problems in the article.For example, line no. 241-243, what I have revised is as follows: Simulated phenology of summer maize was acted as a parameter to obtain a standard EVI time series curve of summer maize. An MAD map was calculated through comparison between time series images of standard summer maize EVI and the actual MODIS-EVI. Appropriate thresholds were set in five different provinces to map spatial distributions of summer maize in the study area.
Author Response File: Author Response.docx
Round 2
Reviewer 4 Report
Dear Authors, I am okay with the changes made. Thank You.
Author Response
对审稿人评论的回复
点1： 3.2。多元线性逐步回归。这是我对您的手稿最大的关注之一。实施了哪些工具？请提供整个程序和结果的证据
回应1：本文使用MATLAB中的逐步回归工具包，构建了夏季玉米物候与环境因素之间的线性方程。具体数据和代码将被上传
要点2： 在图7中，作者报告R指的是什么？R2？图7标题提供了误导性信息。似乎是散点图模拟了doy（现象阶段）和观察到的doy（现象阶段），对吗？请澄清。
响应2： R表示相关系数，已在本文中进行了说明。图7的标题已更改为：“ 2012年黄淮海平原夏季玉米实际物候与模拟夏季玉米物候与环境因素的相关性”
要点3 ： 在研究区域验证标准夏玉米EVI时间序列曲线。“在研究区域中随机选择了十个县”……如何？请提供完整的分析，参考和描述。
回应3 ：在文章中已对其进行了进一步说明，并进行了以下修改。
“在研究区域中随机选择了十个县，以验证标准的夏玉米EVI时间序列曲线。根据3.1节中的方法，分别通过Landsat-7 ETM +图像绘制了10个经过验证的地区的夏玉米的种植面积。利用Landsat提取的玉米分布区域对MODIS EVI时间图像进行遮罩，通过计算获得了10个经过验证的区域的夏玉米实际MODIS EVI时间序列值。通过公式（15），将夏玉米的实际MODIS EVI时间序列值与夏玉米的标准EVI时间序列值进行了比较。”
要点4 ： 一般而言，作者应更好地展现其方法的潜力（利弊）和独创性，包括与使用相似性（适用于不同作物）或不同技术和工具的进一步研究进行比较
应对4 ： 为了更好地突出其方法的潜力（利弊）和独创性，我们进一步改进了手稿的介绍。在下一篇文章中，将通过与使用相似（适用于不同农作物）或不同技术和工具的进一步研究进行比较，来进一步说明这一点。
要点5 ： 据我所知，在这份手稿中，可靠的作物表面估计方法又迈出了新的一步-从本地到区域-因此，请给它提供更多的证据回应5 ：在4.3.3中中，基于Landsat ETM +图像利用30m空间分辨率，获得了2012年六个地区夏玉米的分布区域，并与MODIS数据提取结果进行了比较。
要点6： 文章中的一些小问题需要纠正。
回应6 ：手稿中的一些错误（例如，表格格式问题，拼写错误，语言描述不正确等）已得到纠正。
Author Response File: Author Response.docx
