Climate Change Affects Crop Production Potential in Semi-Arid Regions: A Case Study in Dingxi, Northwest China, in Recent 30 Years

Round 1

Reviewer 1 Report

General comment:

This work deals with climate change's impacts on crop productivity potential in Dingxi which can be of interest to the readers of the journal. There are however some ways to go. The various manuscript sections must be improved as well as the English language. Some specific comments can be seen below:

Specific comments

Abstract

• Abstract: Are the results presented due only to climate factors? what is the contribution of agricultural practices such as irrigation, fertilizers, etc?

Introduction

• Introduction: The research gap in the work is not clearly indicated. The literature review must be revisited to identify the gap that this work intended to fill.

Materials and Methods:

• Materials and Methods: details need to be provided about the computation of the trend values provided in the results section
• Establishment of index system of agricultural ecosystem adaptability: A justification for the positivity or negativity of the indexes should be provided. Why are some indexes considered positive while others are considered negative?

Results

• 89^oC, 26.61 mm and 35.45 mm: What do these correspond to and how were the values computed? is it the slope that corresponds to change per unit of time? If yes, it is advised to use the Sen slope estimator for this purpose. The authors may consider may be the percentage change.
• The annual CPP affected by climate factors showed increase trends, with 1.07-, 1.05- and 1.10-fold increases affected by temperature: The same question applied to this. How are these values computed? What is their meaning? What does an increase of 1.07-fold in CPP due to the increase in Temperature mean?
• 3. Correlation of Standard CPP with Climate Factors: Please, authors should not only display the results without explanation. For instance, what is the understanding of the significant correlation between CPP and precipitation?
• There was a positive correlation of standard CPP with mean minimum temperature (r = 0.0917), mean maximum temperature (r = 0.0673): Why is the need of indicating these correlations? there is obviously no correlation between temperature (min or max) and the CPP.
• …. significant correlation (Figure 3B, C, D and F): Indicate the significance level considered at each time.
• … temperature (r =－2174) and mean solar radiation (r =－ 0.3336) (Figure 3A and E): Are these correlations significant? If not, no need to show them.
• Figure 3: This figure is not really needed as it does not display really the correlation but rather a scatter plot of two variables. The correlations are already indicated in the text above. The same applied to many other figures.
• … correlation ranked 0.4728 (potato), 0.3112 (Chinese herbal medicines), 0.2575 (vegetables), 0.1710 (corn) and 0.1055 (wheat) (Figure 4A, B, C, D and E): The significance of the correlation must be tested. Either there is a significant correlation or there is no correlation. The values of the correlation are not the most important but their significance. The correlation between the mean yield and the standard CPP seems very weak (0.2655, which is likely not significant), this makes the applied method for determining CPP questionable. The potential for crop productivity may not depend only on climatic conditions but also on agriculture practices and management.
• … vegetables showed a 8.91-, 2.33-, 8.73- and 3.10-fold increase, respectively: The same question as previously indicated for calculation of these values and their meaning.

Discussion

• Discussion: The discussion should take into account the limitation of the applied method and the obtained results and what they (results) can be used for.
• temperature and high altitude [14, 29]: Why this is considered an extreme event?

Conclusions:

The conclusion must be revisited considering a standard structure such as:

• recall the objective of the study
• summary of the work
• the implication of the results
• advantages and limitations of the study
• Way forward or perspectives.

 

Author Response

Abstract:

Are the results presented due only to climate factors? what is the contribution of agricultural practices such as irrigation, fertilizers, etc?

Thanks for your rigorous reviewing. In this study, the contribution of agricultural practices such as irrigation, fertilizers, etc has been shown in the Materials and Methods “The agricultural production factor contained positive indexes including: cultivated land per capita, irrigated area, total power of agricultural machinery, and grain economy ratio; and population density was selected as negative index. The agricultural economy factor contained positive indexes including: proportion of agriculture, forestry, animal husbandry and fishery in GDP, per capita GDP and per capita net income of farmers; and negative indexes including: average use of chemical fertilizer and usage of plastic film.” (Page 3, lines 124-130)

And the contributions have been described in the Results “3.6. Change of Agricultural Ecosystem Adaptability”. (Page 9, lines 205-217)

Introduction:

The research gap in the work is not clearly indicated. The literature review must be revisited to identify the gap that this work intended to fill.

Thanks for your suggestion as well as the Reviewer 3 comments, a hypothesis of current study has provided in the text: “---which may be affected by the climate change. Thus, it is of great necessity to find out the most important climatic factors restricting the increase of CPP in the arid and semi-arid regions to increase the CPP in Dingxi region”. (Page 2, lines 67-69)

Materials and Methods:

Details need to be provided about the computation of the trend values provided in the results section.    Establishment of index system of agricultural ecosystem adaptability: A justification for the positivity or negativity of the indexes should be provided. Why are some indexes considered positive while others are considered negative?

Thanks for your suggestion, the Figure 6 has been re-constructed to show the change trend of agricultural ecosystem adaptability. (Page 9, Figure 6).

Results:

1. 0.89^oC, 26.61 mm and 35.45 mm: What do these correspond to and how were the values computed? is it the slope that corresponds to change per unit of time? If yes, it is advised to use the Sen slope estimator for this purpose. The authors may consider may be the percentage change.

Indeed, the method of Sen slope may be a good way to estimate the change of temperature, precipitation and evapotranspiration, while it might be not direct as the specific values.

In this study, in order to the specific change for the annual mean temperature, precipitation and evapotranspiration in recent 30 years from 1989 to 2019, the mean values in the initial ten years (1989 to 1998) compared with the latest ten years (2010 to 2019) were conducted.

2. The annual CPP affected by climate factors showed increase trends, with 1.07-, 1.05- and 1.10-fold increases affected by temperature: The same question applied to this. How are these values computed? What is their meaning? What does an increase of 1.07-fold in CPP due to the increase in Temperature mean?

Firstly, the change of CPP affected by temperature, precipitation and evapotranspiration was calculated in the initial ten years (1989 to 1998) compared with the latest ten years (2010 to 2019). Secondly, the change of CPP show the CPP affected by the temperature, precipitation and evapotranspiration in recent 30 years from 1989 to 2019. Thirdly, the increase of 1.07-fold in CPP is related to the increase of mean temperature, and the specific methods have been provided in the Material and Methods: “Estimation of crop production potential (CPP)” . (Pages 2-3, lines 85-97).

3. Correlation of Standard CPP with Climate Factors: Please, authors should not only display the results without explanation. For instance, what is the understanding of the significant correlation between CPP and precipitation?

There was a positive correlation of standard CPP with mean minimum temperature (r = 0.0917), mean maximum temperature (r = 0.0673): Why is the need of indicating these correlations? there is obviously no correlation between temperature (min or max) and the CPP.

---significant correlation (Figure 3B, C, D and F): Indicate the significance level considered at each time.

---temperature (r =－2174) and mean solar radiation (r =－0.3336) (Figure 3A and E): Are these correlations significant? If not, no need to show them.

Figure 3: This figure is not really needed as it does not display really the correlation but rather a scatter plot of two variables. The correlations are already indicated in the text above. The same applied to many other figures.

---correlation ranked 0.4728 (potato), 0.3112 (Chinese herbal medicines), 0.2575 (vegetables), 0.1710 (corn) and 0.1055 (wheat) (Figure 4A, B, C, D and E): The significance of the correlation must be tested. Either there is a significant correlation or there is no correlation. The values of the correlation are not the most important but their significance. The correlation between the mean yield and the standard CPP seems very weak (0.2655, which is likely not significant), this makes the applied method for determining CPP questionable. The potential for crop productivity may not depend only on climatic conditions but also on agriculture practices and management.

---vegetables showed a 8.91-, 2.33-, 8.73- and 3.10-fold increase, respectively: The same question as previously indicated for calculation of these values and their meaning.

Thanks for your kind reviewing. In this study, in order to show the contribution of climate factors to the CPP, the correlation of standard CPP with climate factors was analyzed by SPSS 22.0 with P < 0.05 level as the basis for a significance. Herein, the higher value of correlation coefficient (r) indicates the more significant correlation between standard CPP with climate factors and actual crops yield. The significance depends on not only the r value but also reaches the P < 0.05 level.

According to your and other reviewer’s comments, the description has been added in the text: “The correlation of standard CPP with climate factors and actual crops yield was analyzed by SPSS 22.0 with 2-tailed test of significance used and P < 0.05 level as the basis for a significance. Herein, the higher value of correlation coefficient (r) indicates the more significant correlation between standard CPP with climate factors and actual crops yield, as well as the changes of cultivation area and agricultural ecosystem adaptability with different planting years.” (Pages 3, lines 111-117).

Discussion:

The discussion should take into account the limitation of the applied method and the obtained results and what they (results) can be used for. “temperature and high altitude [14, 29]: Why this is considered an extreme event?”

In this study, the typical Miami and Thornthwaite Memorial models were applied, their superiorities have been provided in the text: “The Miami and Thornthwaite Memorial models, typical statistical relation-based models, not only can predict the impact of climate on the CPP by establishing the correlation between climate factors and crops production, but also are simple in form and easy to perform [25]. Currently, the two models have been widely used in different regions [26, 27]”. (Page 2, lines 87-91)

Additionally, the description about the “temperature and high altitude [14, 29]” just stated the natural environmental factors, which are affecting the agricultural production in northwest China. As mentioned in the Background: “Dingxi region (34^o26'-35o35′N, 103^o52′-105^o13′E) is located in the central parts of Gansu province and at the intersection of the Loess Plateau and high-altitude West Qinling Mountains”, the Dingxi region faces the low temperature and high altitude.

Conclusions:

The conclusion must be revisited considering a standard structure such as: recall the objective of the study, summary of the work, the implication of the results, advantages and limitations of the study,     way forward or perspectives.

According to your comments, the Conclusion has been re-written: “From the above investigations into the change of climate factors, CPP and planting systems in semi-arid Dingxi region in recent 30 years, we found that the climate change significantly affected climate factor, crops yield, planting systems and agricultural eco-system adaptability in Dingxi region. The precipitation played a more important role in improving CPP than other climate factors. The increases of cultivation area and yield of potato and Chinese herbal medicines play greater contributions to the standard CPP than that of corn and wheat in the semi-arid Dingxi region. These findings will provide scientific and technological support for the agricultural production in the arid and semi-arid regions of northwest China.” (Pages 10-11; lines 295-303)

Author Response File: Author Response.pdf

Reviewer 2 Report

The research is local, which in my opinion does not detract from its validity. The literature review is done correctly with the latest citations from the last 20 years. The research methodology is clear to me. I have a question whether statistical methods were used, and if so, which ones and why exactly these? The results are presented clearly. I have doubts about the R2 coefficient in fig. 3-5 - what does it mean? What does he contribute to the research and its results? What is this unit kg / mh2? From the SI system? Fig 6 - can particular years be connected with lines? This is the trend? Discussion to analyze and reformat the conclusions. Working on the language - native speaker. 

Author Response

The research is local, which in my opinion does not detract from its validity. The literature review is done correctly with the latest citations from the last 20 years. The research methodology is clear to me.

1> I have a question whether statistical methods were used, and if so, which ones and why exactly these?

In this study, the CPP was estimated by using the Miami and Thornthwaite Memorial models. In order to highlight their superiorities, some references have cited accordingly in the text: “The Miami and Thornthwaite Memorial models, typical statistical relation-based models, not only can predict the impact of climate on the CPP by establishing the correlation between climate factors and crops production, but also are simple in form and easy to perform [25]. Currently, the two models have been widely used in different regions [26, 27]”. (Page 2, lines 87-91)

The results are presented clearly. I have doubts about the R2 coefficient in fig. 3-5 - what does it mean? What does he contribute to the research and its results?

In this study, the R² (r) indicates the correlation of standard CPP with climate factors (Fig. 3) and actual crops yield (Fig. 4). The higher value of R² indicates the more significant correlation. In order to clearly show the R² (r), the description has been added in the text: “Herein, the higher value of correlation coefficient (r) indicates the more significant correlation between standard CPP with climate factors and actual crops yield, as well as the changes of cultivation area and agricultural ecosystem adaptability with different planting years” (Page 3, lines 114-117).

Meanwhile, the description of contributions has added in the text: “These findings indicate that mean precipitation and actual evapotranspiration significantly contributes to the increase of the standard CPP in the semi-arid Dingxi region.” (Page 5, lines 161-163); and “which indicates that the yields of potato and Chinese herbal medicines play greater contributions to the standard CPP than that of corn and wheat in the semi-arid Dingxi region.” (Page 6, lines 178-180).

What is this unit kg/hm²? From the SI system?

In this study, the unit “hm2” is the same as “ha”. In order to make the readers easy to understand, the “ha” has replaced the “hm2” throughout the text.

Fig 6 - can particular years be connected with lines? This is the trend?

Indeed, this is the trend of changes in agricultural ecosystem adaptability including: agricultural environment factor, agricultural production and development factor, agricultural economic benefit factor, and composite index. In order to show the changes with the years extended, the regression analysis was conducted and a new figure has been provided. (Page 9, lines 215-216)

Discussion to analyze and reformat the conclusions.

According to your comments, the Discussion and Conclusion have been reformatted. (Pages 10-11; lines 254-560, 272-276; 295-303)

Working on the language - native speaker.

According to your comments, the English language has been carefully checked throughout the text.

Author Response File: Author Response.pdf

Reviewer 3 Report

The manuscript entitled; “Climate Change Affects Crop Production Potential in Semi-arid Regions: a Case Study in Dingxi, Northwest China in Recent 30 Years” by Jia et al. describes about the role of different environmental factor to affect the yield of five important crops of Dinxi area over the past 30 years. The manuscript is well written however, I have following comments which must be incorporated.

Abstract

Please indicate a clear a clear or concrete objective of current study

Line 12 and 51, please change the word “locate” with “located”

Line 21, please insert respectively after vegetables

Introduction

Line 63, what is “hm2”

Please indicate a concrete hypothesis of current study

Materials and Methods

Line 93 and, what is “dominated”? I can understand these two sentences

Results

Figures quality is poor please increase resolution

Please indicate standard error bars on figure 1, 2 and 5

Please indicate the p-value along with r value for figure 3

Discussion

The grain yield of wheat is decreased in comparison to other crops. Is this not due to decreasing area of the wheat? Please explain the reason with proper discussion.

Author Response

Abstract:

Please indicate a clear or concrete objective of current study

According to your comments, a concrete objective of this study has been added in the Abstract: “In order to find out the most important climatic factors restricting the increase of CPP in the arid and semi-arid regions, the change of climate factors, CPP and their correlation as well as planting systems were analyzed based on the representative semi-arid location Dingxi of Gansu province from 1989 to 2019.” (Page 1, lines 12-15)

Line 12 and 51, please change the word “locate” with “located”

The word “locate” has revised to “located”. (Page 1, lines 12; Page 2, lines 52)

Line 21, please insert respectively after vegetables

The word “respectively” has inserted after the word vegetables. (Page 1, line 21)

Introduction:

Line 63, what is “hm2”

In this study, the unit “hm2” is the same as “ha”. In order to make the readers easy to understand, the “ha” has replaced the “hm2” throughout the text.

Please indicate a concrete hypothesis of current study

Thanks for your suggestion, a hypothesis of current study has provided in the text: “---which may be affected by the climate change. Thus, it is of great necessity to find out the most important climatic factors restricting the increase of CPP in the arid and semi-arid regions to increase the CPP in Dingxi region”. (Page 2, lines 67-69)

Materials and Methods:

Line 93 and, what is “dominated”? I can understand these two sentences

In order to make the readers easy to understand, the “dominated” has changed into “determined”. (Page 3, lines 97 and 103)

Results:

Figures quality is poor please increase resolution

According to your comments, the resolution of Figures in the text has increased up to 300 dpi. Sometimes, the resolution will be decreased during the transfer from the Word to PDF.

Please indicate standard error bars on figure 1, 2 and 5

Thanks for your suggestion, the standard error bars have added in the Figures 1, 2 and 5. (Page 4, Figure 1; Page 5, Figure 2; Page 8, Figure 5)

Please indicate the p-value along with r value for figure 3

According to your comments, the “p<0.05” has added in the title of Figures 3, 4 and 5. (Pages 6-8)  

Discussion:

The grain yield of wheat is decreased in comparison to other crops. Is this not due to decreasing area of the wheat? Please explain the reason with proper discussion.

According to your comments, the explanation has been added in the text: “Several researches reported that most of climate factors especially in increased temperatures have a yield-reducing effect on wheat [11, 46]; Researches on wheat cultivation in Gansu province found that the decrease of cultivation area was restricted not only by climate change especially in drought but also the low economic benefits [49, 50]”. (Page 10, lines 272-276)

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Dear authors,

Thanks for submitting the updated version of your manuscript. After reading through, I found that most of the concerns raised about the paper have not been seriously considered. Taking them into account may have improved substantially the quality of the manuscript. 

Author Response

Dear Reviewer,

Thanks very much for your kind work and comments. We are very sorry for not meeting your standards, even though we have tried our best to revise the mansucript.

Firstly, according to your and reviewer 3 comments, in order to fill the research gap in the work (your comments) or  a concrete hypothesis of current study (reviewer 3 comments), some sentences about "what has done and what is missing in Dingxi city" have been added in the end of the Introduction section.

Secondly, the numbers of correlation that was observed to be not significant have been deleted in Figure 3 and Figure 4; meanwhile, the "P<0.05" has added in the Figure 3 and Figure 5.

Finally, the English language has been pre-edited by the MDPI English editing service.

Best regards,

Mengfei Li

 

Reviewer 3 Report

Dear Jia et al.

Many thanks for incorporating the suggested changes in the manuscript entitled; “Climate Change Affects Crop Production Potential in Semi-arid Regions: a Case Study in Dingxi, Northwest China in Recent 30 Years”.

However, following two comments are yet to be answered

Abstract

Please indicate a clear a clear objective of current study

Introduction

Please indicate a concrete hypothesis of current study

Author Response

Dear Reviewer,

Thanks very much for your suggestion. We have tried our best to address each comment. Attachments below with our responses are shown in bold. Revised parts are marked up using the "Track Changes" function.

Abstract: Please indicate a clear a clear objective of current study.

In the Abstract section, more descriptions about the clear objective of current study: "---and planting systems---" and "--- of northwest China---" as well as "and the precipitation played a more important role in improving CPP than other climate factors" have been added.

Introduction: Please indicate a concrete hypothesis of current study

In the Introduction section, a concrete hypothesis of current study has been indicated: "In order to increase the CPP in Dingxi region, some researchers reported that the grassland agricultural production mode in Dingxi region was more effective and suitable than the traditional cultivated land agricultural production mode, because the former can provide products, conserve soil, regulate climate, sequestrate carbon and product oxygen [21]; other researchers reported that the crops of Chinese herbal medicines, potato and flowers have more comparative advantage than other crops in Dingxi region [22]. To date, the CPP afftected by the climate change in the arid and semi-arid regions of northwest China, especially in the semi-arid Dingxi region of Gansu province, has not been yet studied."

Thanks again for your comments.

Best regards,

Mengfei Li

 

Round 3

Reviewer 1 Report

The manuscript has been substantially improved .