Spatial and Temporal Evolution of Vegetation Water Consumption in Arid and Semi-Arid Areas against the Background of Returning Farmland to Forestland

Round 1

Reviewer 1 Report

1.     What is the knowledge gap and the innovation of this study? you should better explain this in the introduction.

2.     The discussion should be significantly improved before it was accepted. You have to compare your results with other studies and also explain the reasons of these results. Meanwhile, what is the implications of your findings?

3.     The conclusions were missing.

4.     It better to revise the manuscript with a native English speaker.

5.     You have to enlarge the font in the figures, to make sure it can be cleanly seen in a A4 page.

6.     Line 22 in page 1, there are some mistakes.

7.     Figure 7, 10^-8 m³ ?

 

8.     The water consumption was related to the land area, therefore it is better to use the unit of mm rather than m³ or m³/m².

Author Response

1.What is the knowledge gap and the innovation of this study? you should better explain this in the introduction.

Reply: Thank the reviewers for their comments, and the abstract has been checked and modified.

The modifications are as follows:Expanding ecological space is considered as an effective way to conserve water resources. Water conservation value of ecological space especially woodland, may be overestimated in arid and semi-arid areas. The innovation of this study is the analysis of water consumption in different land use types from a complete watershed scale, which can evaluate space management under the background of returning farmland to forests during the past 20 years, and provide suggestions for future space management in semi-arid areas.

 

2.The discussion should be significantly improved before it was accepted. You have to compare your results with other studies and also explain the reasons of these results. Meanwhile, what is the implications of your findings?

Reply: Thanks for the review's suggestions on modification, and the part discussed in the article has been checked and modified.

The modifications are as follows:Luo[36] has used the phreatic evaporation formula to estimate the ecological water demand of vegetation in the Yanhe River Basin. However, the research has used limited site data and single vegetation coefficient as the basic data without analyzing the annual vegetation water demand. The current study has conducted an in-depth investigation of the local dominant plant community species, vegetation growth period and vegetation distribution through field research. Thus, the results are authentic and credible, and can be used as a reference for the scientific allocation of water resources. The results of this study are consistent with the findings of many scholars in the arid and semi-arid regions of China, including: the water consumption of vegetation has exceeded the regional precipitation, aggravating the decline of the groundwater level [37-39].the water consumption of forest land has increased significantly, causing serious water deficit, especially in the initial and developmental stages [40-41].

 

3. The conclusions were missing.

Reply: Thank the reviewers for their comments on the draft, and the conclusion has been checked and revised.

The modifications are as follows:The results show that in arid and semi-arid areas, the sustainable development of ecological space needs to clarify the relationship between effective water resources and water consumption in regional ecological space.Based on the analysis of the water consumption of vegetation in Yanhe River basin in Shaanxi Province, it is found that the annual water consumption of vegetation in Yanhe River basin is on the rise from 2000 to 2020, indicating that the water resources in the study area have continued to decline in recent years, and ecological construction should be re examined in the future. Affected by the policy of returning farmland to forests, the forest land along the upper reaches of the river has increased excessively. The increasing trend of vegetation water consumption in the upstream is more obvious than that in the downstream.If conditions permit, the ecological space should be optimized and controlled. In the construction of regional ecological space, attention should be paid to spatial refinement governance and regional differentiation development. In Ansai and Baota areas, priority should be given to vegetation types with low water consumption after returning farmland to grassland to improve grassland coverage.This shows that policies in the upstream areas in the future should focus on farmland protection rather than expanding forest land. Grassland should be the first choice for restoring ecological space. In the future, it is very necessary to reduce water use in semi-arid areas.Although the water consumption of vegetation in Yanchang area fluctuates slightly, the proportion of forest land should be controlled.To sum up, it is very important to use low water consumption plants to continuously improve ecological construction to promote sustainable development in the future.

 

4. It better to revise the manuscript with a native English speaker.

Reply: Thanks for the suggestions of the reviewers. The full text has been read through, grammar and word errors in the text have been checked and corrected, and the blue font has been used to modify and highlight the text.

 

5.You have to enlarge the font in the figures, to make sure it can be cleanly seen in a A4 page.

Reply: Thanks for the suggestions of the reviewers. The fonts in the article have been adjusted. See the text for details.

 

6. Line 22 in page 1,there are some mistakes.

Reply: Thanks for the review suggestions of the reviewer, and the error part on the first page of the text has been checked and corrected.

The modifications are as follows:the current study quantitatively analyzes the spatial and temporal variation characteristics of water consumption of different vegetation growth stages in Yanhe River Basin by using the improved Penman formula. The results show that the water consumption of vegetation in Yanhe River Basin increases from0. 44km³ in 2000 to 0.68km³ in 2020, with an average annual water consumption of 0.537km³. The water consumption of vegetation showed obvious spatial heterogeneity, with the highest value in the central Baota area (1.094km³) following by western Ansai region (0.727km³), whereas the consumption in eastern Yanchang area is relatively low (0.483km³). In addition, the annual average water consumption is (0.381km³). The cultivated land consumes the most water (0.21km³), while the woodland consumes the least (0.072km³).

 

7.Figure 7, 10-8 m3 ?

Reply: Thanks for the review suggestions of the reviewers. Figure 7 has been checked and revised.

The modifications are as follows:The temporal and spatial changes of potential evapotranspiration in 2000, 2005, 2010, 2015 and 2020 in Yanhe River Basin are shown in Fig. 7. The potential evapotranspiration of the basin shows a trend of increasing from south to north and then decreasing to southeast. The maximum evapotranspiration (1283.41mm) is in Baota District, and the minimum evapotranspiration (620.566mm) is in Ansai district. Among them, the rising trends of Yanchang station, Zhidan station, Ansai station and Baota station all pass the 95% significance test. Baota station has the largest change rate of potential evapotranspiration, and Ansai station has the lowest change rate.

 

8.The water consumption was related to the land area, therefore it is better to use the unit of mm rather than m3 or m3/m2.

Reply: Thanks for the review's suggestions on modification. The units related to water consumption and land area in the text have been checked and replaced. See the text for specific modifications.

Reviewer 2 Report

Line4. "Yan WU 1 "：Improper use of superscript and subscript

The abstrct is too long and needs to be simplified. Key information needs to be further refined

p2-3  Study area : There are many mistakes in the use of units

Formulas used in the text should be numbered

Figure 1(c):  Latitude only, no longitude；There are two figure7 in the paper

There is no conclusion in the paper

The format of references is confused

Author Response

Line4. "Yan WU 1 ":Improper use of superscript and subscript

Reply: Thank the reviewers for their suggestions. This part has been checked and revised. It has been revised in the article.

 

The abstrct is too long and needs to be simplified. Key information needs to be further refined

Reply: Thank the reviewers for their comments, and the abstract has been checked and revised.

The summary is as follows:Abstract: The sustainable development in arid and semi-arid areas is largely constrained by water resources. Expanding ecological space is considered as an effective way to conserve water resources. Water conservation value of ecological space especially woodland, may be overestimated in arid and semi-arid areas. The innovation of this study is the analysis of water consumption in different land use types from a complete watershed scale, which can evaluate space management under the background of returning farmland to forests during the past 20 years, and provide suggestions for future space management in semi-arid areas.

 

p2-3  Study area : There are many mistakes in the use of units

Reply: Thanks for the comments of the review, the unit use in P2-3 has been checked and modified, and the specific modifications are detailed in the document.

 

Formulas used in the text should be numbered

Reply: Thanks for the review's suggestions on modification. The formula number used in the document has been checked and modified. See the document for details.

 

Figure 1(c):  Latitude only, no longitude;

Reply: Thanks for the review's suggestions on modification. Figure 1 (C) has been checked and modified. See the text for specific modifications.

 

There are two figure7 in the paper

Reply: Thanks for the review's suggestions on modification. Figure 7 has been checked and revised. See the text for specific modifications.

 

There is no conclusion in the paper

Reply: Thank the reviewers for their comments on the draft, and the conclusion has been checked and revised.

The conclusion is as follows:The results show that in arid and semi-arid areas, the sustainable development of ecological space needs to clarify the relationship between effective water resources and water consumption in regional ecological space.Based on the analysis of the water consumption of vegetation in Yanhe River basin in Shaanxi Province, it is found that the annual water consumption of vegetation in Yanhe River basin is on the rise from 2000 to 2020, indicating that the water resources in the study area have continued to decline in recent years, and ecological construction should be re examined in the future. Affected by the policy of returning farmland to forests, the forest land along the upper reaches of the river has increased excessively. The increasing trend of vegetation water consumption in the upstream is more obvious than that in the downstream.If conditions permit, the ecological space should be optimized and controlled. In the construction of regional ecological space, attention should be paid to spatial refinement governance and regional differentiation development. In Ansai and Baota areas, priority should be given to vegetation types with low water consumption after returning farmland to grassland to improve grassland coverage.This shows that policies in the upstream areas in the future should focus on farmland protection rather than expanding forest land. Grassland should be the first choice for restoring ecological space. In the future, it is very necessary to reduce water use in semi-arid areas.Although the water consumption of vegetation in Yanchang area fluctuates slightly, the proportion of forest land should be controlled.To sum up, it is very important to use low water consumption plants to continuously improve ecological construction to promote sustainable development in the future.

 

The format of references is confused

Reply: Thanks for the suggestions of the review, and the references in the text have been checked and revised.

The modifications are as follows:[3] Jiang Yongqing Review and Prospect of China's urbanization in the century [J] Qiusuo, 2001,11(01): 27-30

[4] Cao Zongping The disadvantages of the existing urbanization mode in the western region and the realistic choice preference [J] Contemporary economic research, 2011,13 (02): 60-64

[11] Peng Fei, he Xinlin, Liu Bing, et al Study on calculation method of ecological water demand of desert vegetation in arid area [J] Water saving irrigation, 2017,15 (12): 90-93

[24]Cheng S Y,Liu B Q．Current state and progress of research on ecological and environmental water requirements．Water Sciences and Engineering Technology,2005,11(6):39-41．

[30] Yang Xiaonan. Influence of multi-scale landscape pattern on runoff and sediment transport process in the Loess Plateau [D]. Yangling, Shaanxi: Northwest University of agriculture and forestry, 2019,34(21):74-81

[32] Wei Lemin Research on ecological water demand of natural vegetation in Shule River Basin Based on spatial optimization of ecological carrying capacity [D]. Lanzhou University, 2021,42(07):114-127

[38]Zhu Huiyi, Li Xiubin. Discussion on regional land use change index model [J]. Journal of geography, 2003 (5): 643-650

Reviewer 3 Report

Ms. Ref. No.: sustainability-1963132
Title: Spatial and temporal evolution of vegetation water consumption in arid and semi-arid areas under the background of returning farmland to forest

Authors: Ting Guo, Quanhua Hou, Yan Wu, Lingda Zhang

Recommendation: Major revision

General recommendation:

The study analyzed water consumption due to the change from agricultural lands to forestland in China. It is a topic of interest to researchers in related areas. However, the manuscript in its actual form should not be accepted. From the introduction, methodology and discussion must be improved because it only focused on local (China) papers, so it is necessary to reinforce with international research. Furthermore, there is no conclusion section essential to finalize the article. 

Specific comments:
1. In the abstract (line 18) and the entire document, the authors use x108 m³. Clarify why to use it.

2. Line 45. There is a missing point at the end of the line.

3. Line 66. Based on lowercase, and modify to Penman-Monteith.

4. In many parts of the document are lowercase letters that must be changed to uppercase letters. Please verify the entire document.

5. Line 106. The sentence is not clear. Please rewrite it.

6. Figure 1. Please add a figure with the location of the study area in China for international readers.

7. The methodology section generally is written in the past tense. Please verify and modify it.

8. Be consistent in the units of mm/day. Sometimes are in lowercase letters, other times in uppercase.

9. Figure 3 is missing, so verify the numbering of figures.

10. m-k trend analysis is not described in the methodology section.

11. Line 223. UF and UB curves are not defined in the methodology section.

12. Figure 5 is not described in the manuscript.

13. Section 3.2 have subsections with only one paragraph. Rewrite in an individual section.

14. Line 318. FIG 10 modify to Fig. 10

15. The discussion section is vague and written as bullets with no connection. Please rewrite this section because it should not be a summary. The authors explain that the change in land use to forest land represents an increase in water consumption. Hence should be interesting present options to reduce it. Furthermore, this section must be compared with international experiences to improve the manuscript.

16. There is no conclusion section. Please add it.

 

17. Include international references. 

Author Response

1. In the abstract (line 18) and the entire document, the authors use x108 m3. Clarify why to use it.

Reply: Thank you for the review's suggestions on modification.There are some problems in the use of the unit, which have been corrected in the article.

2. Line 45. There is a missing point at the end of the line.

Reply: Thank you for the review's suggestions on modification. This part of the text has been checked and revised. See the text for details of the modifications.

 

3. Line 66. Based on lowercase, and modify to Penman-Monteith.

Reply: Thanks for the comments of the reviewers. This part of the text has been checked and replaced.

 

 

4. In many parts of the document are lowercase letters that must be changed to uppercase letters. Please verify the entire document.

Reply: Thanks for the review's suggestions on modification. The full text has been checked and replaced. See the text for details of the modifications.

 

5. Line 106. The sentence is not clear. Please rewrite it.

Reply: Thank the reviewers for their comments on the draft. This part of the text has been checked and revised.

The modifications are as follows:In addition, the sediment concentration [31] value in the river is high. As a result, the utilization of water resources is relatively high, but the utilization rate is low. In addition, after farmland was converted to forest, the irrigation method was relatively backward, and the water consumption of vegetation increased, resulting in an extreme shortage of water resources.

 

6.Figure 1. Please add a figure with the location of the study area in China for international readers.

Reply: Thank the reviewers for their comments on the draft. the location of the study area in China has been added in figure 1.

7.The methodology section generally is written in the past tense. Please verify and modify it.

Reply: Thank the reviewers for their comments on the draft. The methodology section has been modifed in the past tense.

8. Be consistent in the units of mm/day. Sometimes are in lowercase letters, other times in uppercase.

Reply: Thanks for the review suggestions of the reviewers. The mm/day part in the text has been checked and replaced. See the text for the specific modifications.

 

9. Figure 3 is missing, so verify the numbering of figures.

Reply: Thanks for the review's suggestions on modification. Figure 3 has been checked and revised. See the text for details.

10. m-k trend analysis is not described in the methodology section.

Reply: Thanks for the review's suggestions on modification. The m-k trend analysis has been added.

The modifications are as follows:Mann-Kendall Statistical Test is used to analyze the change trend of potential evapotranspiration^[35]. In this study, the Mann-Kendal (M-K) trend test was applied to perform trend analysis and mutation test of the regional drought risk index. The M-K trend test is a non-parametric statistical test that has been recommended by WMO for long-term meteorological trend and mutation analysis^[36-37]. For the time series x with n as the sample size, the sequence  is constructed as follow：

                                                                          (13)

where                                                        (14)

In equation (14), the cumulative number of samples when  is the value of the ranking sequence . Assuming that the time series x is random and independent, the mean (3) and variance (4) of the  are calculated as follows:

                                                                (15)

                                (16)

 

11. Line 223. UF and UB curves are not defined in the methodology section.

 

Reply: Thanks for the review's suggestions on modification. The definition of UF and UB curves trend analysis has been added.

Then the following statistic  is defined as :     

                                                                                  (17)

where  is the standard normal distribution. Given a defined significance level α, the value of  could be found in the standard normal distribution table. If , there is a significant upward or downward trend in the time series.

The temporal order is reversed and the above process is repeated while making  to plot and analyze the  curve and  curve. When the  curve exceeds the critical line of a certain confidence interval, it indicates a significant changing trend in the time series. When the two curves intersect and the intersection are between the two critical lines, the corresponding time of intersection is the start of the mutation.

 

12. Figure 5 is not described in the manuscript.

Reply: Thanks for the comments of the reviewers. Figure 5 has been checked and revised.

The modifications are as follows:Figure 5 shows the monthly variation characteristics of the potential evapotranspiration in the river basin along the river. The monthly potential evapotranspiration in the river basin is unimodal, with a high value from May to August. Figure 6 shows the seasonal variation characteristics of potential evapotranspiration in the river basin along the river. The seasonal potential evapotranspiration is shown as follows: summer>spring>autumn>winter.

 

13.Section 3.2 have subsections with only one paragraph. Rewrite in an individual section.

Reply: Thanks for the modification suggestions of the review, and the explanatory text of the subsection in Section 3.2 is clear enough. If the content is added, it will make this paragraph very tedious. Therefore, this part will not be modified.

 

14. Line 318. FIG 10 modify to Fig. 10

Reply: Thank the reviewers for their comments on the draft. This part of the text has been checked and revised. See the text for details.

 

15. The discussion section is vague and written as bullets with no connection. Please rewrite this section because it should not be a summary. The authors explain that the change in land use to forest land represents an increase in water consumption. Hence should be interesting present options to reduce it. Furthermore, this section must be co

Reply: Thank the reviewers for their suggestions, and the discussion part has been checked and revised.

The modifications are as follows:Luo^[36] has used the phreatic evaporation formula to estimate the ecological water demand of vegetation in the Yanhe River Basin. However, the research has used limited site data and single vegetation coefficient as the basic data without analyzing the annual vegetation water demand. The current study has conducted an in-depth investigation of the local dominant plant community species, vegetation growth period and vegetation distribution through field research. Thus, the results are authentic and credible, and can be used as a reference for the scientific allocation of water resources. The results of this study are consistent with the findings of many scholars in the arid and semi-arid regions of China, including: the water consumption of vegetation has exceeded the regional precipitation, aggravating the decline of the groundwater level ^[37-39].the water consumption of forest land has increased significantly, causing serious water deficit, especially in the initial and developmental stages ^[40-41].The study found that the annual average water consumption of vegetation in the ecological space of Yanhe River Basin is 0.537 km³, with the most in the central Baota area (1.094 km³), followed by Ansai region in the West (0.727 km³), and the lowest in the eastern extension area (0.483 km³). In addition, the annual average water consumption is (0.381 km³).The water consumption of vegetation in Yanhe River Basin shows an upward trend, and the increased areas are mainly distributed in Baota District and Ansai district.The water consumption of different vegetation types is obviously different and decreases in the trend of forest land > irrigated forest land > sparse forest land > medium coverage grassland > cultivated land > low coverage grassland.Forest land, shrub land, high coverage grassland, medium coverage grassland and desert vegetation all show the trend of middle growth period > development period > late growth period > early growth period. The water consumption of all vegetation in the development period, initial stage and the late stage of growth has decreased, with woodland, open woodland and shrub decreasing the most, and grassland with medium and low coverage decreasing the least. In addition, the water consumption of arable land in the development period is relatively high.

Reviewer 4 Report

This manuscript is a nice contribution in understanding the water consumption of vegitation in arid region. The manuscript is well written and methodology is easy to follow. Based on the following suggestions this referee suggests to accept the manuscript after minor revisions.

1. The first five lines of Abstract section present information which is already well known authors should reduce this content.

2. The introduction section can be revised and it is suggested that authors should add few contributions from arid regions other than China this will make the manuscript useful for global researchers.

3. In figure 1 (c) authors should add the main source for land use maps.

4. Authors should add a flow chart of their methodology.

5. The discussion and conclusion section has a potential to be extended authors should review and revise this section.

Author Response

1.The first five lines of Abstract section present information which is already well known authors should reduce this content.

Reply: Thanks for the review's suggestions on modification, and the summary has been checked and revised.

The modifications are as follows:Abstract: The sustainable development in arid and semi-arid areas is largely constrained by water resources. Expanding ecological space is considered as an effective way to conserve water resources. Water conservation value of ecological space especially woodland, may be overestimated in arid and semi-arid areas. The innovation of this study is the analysis of water consumption in different land use types from a complete watershed scale, which can evaluate space management under the background of returning farmland to forests during the past 20 years, and provide suggestions for future space management in semi-arid areas.The research on the water consumption of vegetation plays an important role in the rational allocation of water resources in the basin. Based on the meteorological data and GIS technology, the current study quantitatively analyzes the spatial and temporal variation characteristics of water consumption of different vegetation growth stages in Yanhe River Basin by using the improved Penman formula. The results show that the water consumption of vegetation in Yanhe River Basin increases from 0.44km³ in 2000 to 0.68km³ in 2020, with an average annual water consumption of 0.537km³. The water consumption of vegetation showed obvious spatial heterogeneity, with the highest value in the central Baota area (1.094km³) following by western Ansai region (0.727km³), whereas the consumption in eastern Yanchang area is relatively low (0.483km³). In addition, the annual average water consumption is (0.381km³). The cultivated land consumes the most water (0.210km³), while the woodland consumes the least (0.72km³). The water consumption per unit area of forested land is the highest, reaching 190mm, and the water consumption of low coverage grassland is the lowest, only reaching 50mm. There are also great differences in the water consumption changes of different vegetation growth stages from 2000 to 2020, and the water consumption is the largest in the middle period of plant growth. Under the condition of low potential evaporation rate, vegetation distribution change is the main influencing factor of vegetation water consumption change in Yanhe River Basin. Through the establishment of the sustainable development path of ecological space with water as the core, the high-quality development of ecological environment in arid and semi-arid areas will be achieved.

 

2.The introduction section can be revised and it is suggested that authors should add few contributions from arid regions other than China this will make the manuscript useful for global researchers.

Reply: Thanks for the suggestions of the reviewers, and the introduction has been checked and revised.

The modifications are as follows:The increase in vegetation coverage plays an important role in driving the change of evapotranspiration ^[6]. In recent years, many scholars at home and abroad have explored the relationship between evapotranspiration and vegetation types and vegetation coverage changes. Allen^[7] describes three extensions of the evaporation calculation program, which are designed to improve the accuracy of applications when they guarantee additional complexity. Under the background of afforestation in dry areas, Lu ^[8] has studied the evapotranspiration of vegetation in dry areas of China based on seven evapotranspiration models, and proved that afforestation in dry areas of China would aggravate the decline of groundwater. Based on the principle of water balance, long Vicente Serrano^[9]  has analyzed the analysis of standardized evapotranspiration index (SPEI) and vegetation index worldwide, the vulnerability of arid and semi-arid areas is higher under the influence of vegetation.Based on penman Monteith (PM) formula combined with meteorology, hydrology, vegetation and land using the calculation method of large-scale vegetation water consumption based on remote sensing data, Jiang Tianliang^[10] has discussed the evolution rules of vegetation water consumption of 9 vegetation types and 17 ecological geographical zones in Northwest China and their response to meteorological drought. The results show that the water consumption in Northwest China is generally more in the southeast and less in the northwest. From 1990 to 2015, The area and total water consumption of all kinds of vegetation has increased, among which the total water consumption of the region has increased by 87.62 billion m³. Replacing NDVI with water consumption can better reflect the comprehensive impact of meteorological drought on vegetation. At present, the calculation methods of vegetation water consumption mainly include area quota method ^[11-13], phreatic evaporation method ^[14-18], plant evapotranspiration method ^[19-21], water balance method ^[22-23], biomass method ^[24-25], and calculation method based on remote sensing technology ^[26-29]. Because the research on vegetation water consumption in China is relatively insufficient, the method based on the potential evapotranspiration of vegetation and combined with the calculation method of soil moisture and plant area can be applied to the desert, grassland, forest and other ecosystems to approximate the ecological water demand of vegetation in the region with relatively complete basic data ^[2]. Vegetation protection in the basin is of great ecological and political significance. It is a prerequisite for rational allocation of water resources to ensure the normal growth of vegetation to clarify the spatial and temporal distribution of water consumption by vegetation in the basin. This paper uses the improved Penman formula method, with the support of meteorological data and GIS technology, to calculate the vegetation water consumption in 2000, 2005, 2010, 2015 and 2020 in the Yanhe River Basin on a grid scale, analyzes its spatial and temporal distribution and change, and discusses the impact of vegetation type and reference evapotranspiration on water consumption. It provides a more accurate and scientific reference for the study of green and sustainable development of the basin.

 

3.In figure 1 (c) authors should add the main source for land use maps.

Reply: Thanks for the revision suggestions of the review, and the source of the land use map in Figure 1 (C) has been supplemented and explained.

The modifications are as follows:c. land use map of Yanhe River Basin in 2020 cited from the resource and environment science data center of the Chinese Academy of Sciences

 

4.Authors should add a flow chart of their methodology.

Reply: Thank the reviewers for their comments on the draft. The method in the text has been supplemented and explained in the flow chart. See the text for specific modifications.

 

5.The discussion and conclusion section has a potential to be extended authors should review and revise this section.

 

Reply: Thanks for the review's suggestions on modification, and the discussion and conclusion in the text have been checked and revised.

The modifications are as follows:

4. Discussion

Luo^[36] has used the phreatic evaporation formula to estimate the ecological water demand of vegetation in the Yanhe River Basin. However, the research has used limited site data and single vegetation coefficient as the basic data without analyzing the annual vegetation water demand. The current study has conducted an in-depth investigation of the local dominant plant community species, vegetation growth period and vegetation distribution through field research. Thus, the results are authentic and credible, and can be used as a reference for the scientific allocation of water resources. The results of this study are consistent with the findings of many scholars in the arid and semi-arid regions of China, including: the water consumption of vegetation has exceeded the regional precipitation, aggravating the decline of the groundwater level ^[37-39].the water consumption of forest land has increased significantly, causing serious water deficit, especially in the initial and developmental stages ^[40-41].

The study found that the annual average water consumption of vegetation in the ecological space of Yanhe River Basin is 0.537 km³, with the most in the central Baota area (1.094 km³), followed by Ansai region in the West (0.727 km³), and the lowest in the eastern extension area (0.483 km³). In addition, the annual average water consumption is (0.381 km³).The water consumption of vegetation in Yanhe River Basin shows an upward trend, and the increased areas are mainly distributed in Baota District and Ansai district.The water consumption of different vegetation types is obviously different and decreases in the trend of forest land > irrigated forest land > sparse forest land > medium coverage grassland > cultivated land > low coverage grassland.Forest land, shrub land, high coverage grassland, medium coverage grassland and desert vegetation all show the trend of middle growth period > development period > late growth period > early growth period. The water consumption of all vegetation in the development period, initial stage and the late stage of growth has decreased, with woodland, open woodland and shrub decreasing the most, and grassland with medium and low coverage decreasing the least. In addition, the water consumption of arable land in the development period is relatively high.

5. 5. Conclusion

This study shows that in arid and semi-arid areas, the sustainable development of ecological space requires to figure out the relationship between available water resources and water consumption in regional ecological space.Based on the analysis of the water consumption of vegetation in Yanhe River basin in Shaanxi Province, it is found that the annual water consumption of vegetation in Yanhe River basin is on the rise from 2000 to 2020, indicating that the water resources in the study area have continued to decline in recent years, and ecological construction should be re examined in the future. Affected by the policy of returning farmland to forests, the forest land along the upper reaches of the river has increased excessively. The increasing trend of vegetation water consumption in the upstream is more obvious than that in the downstream.If conditions permit, the ecological space should be optimized and controlled. In the construction of regional ecological space, attention should be paid to spatial refinement governance and regional differentiation development. In Ansai and Baota areas, priority should be given to vegetation types with low water consumption after returning farmland to grassland to improve grassland coverage.This shows that policies in the upstream areas in the future should focus on farmland protection rather than expanding forest land. Grassland should be the first choice for restoring ecological space. In the future, it is very necessary to reduce water use in semi-arid areas.Although the water consumption of vegetation in Yanchang area fluctuates slightly, the proportion of forest land should be controlled.To sum up, it is very important to use low water consumption plants to continuously improve ecological construction to promote sustainable development in the future.

 

Round 2

Reviewer 1 Report

the manuscript was obviously improved now

Author Response

(x) English language and style are fine/minor spell check required 

reply ：Thank you ，I have made   English language spell check  as your suggestion .

the manuscript was obviously improved now

reply:  Thank you for your affirmation and encouragement .

Reviewer 2 Report

After modification, the quality of the article has been greatly improved. 

Modification comments：

1.It is recommended to simplify the summary again.

2.Appropriately expand the discussion section.

3.Further optimize the expression of the conclusion.

4.Figure 7 The content is inconsistent with the title (2018?, 2020?)

Author Response

After modification, the quality of the article has been greatly improved. 

Modification comments：

1. It is recommended to simplify the summary again.

Reply: Thank the reviewers for their comments, and the abstract has been checked and modified.

The modifications are as follows:The sustainable development in arid and semi-arid areas is largely constrained by water resources. Expanding ecological space is considered as an effective way to conserve water resources. The innovation of this study is the analysis of water consumption in different land use types from a complete watershed scale, which can evaluate space management under the background of returning farmland to forests during the past 20 years, and provide suggestions for future space management in semi-arid areas.Based on the meteorological data and GIS technology, the current study quantitatively analyzes the spatial and temporal variation characteristics of water consumption of different vegetation growth stages in Yanhe River Basin by using the improved Penman formula. The results show that the water consumption of vegetation in Yanhe River Basin increases from 0.44km³ in 2000 to 0.68km³ in 2020. The water consumption of vegetation showed obvious spatial heterogeneity, with the highest value in the central Baota area (1.094 × km³) following by western Ansai region (0.727km³), whereas the consumption in eastern Yanchang area is relatively low (0.483km³). In addition, the annual average water consumption is (0.381 km³). The cultivated land consumes the most water (0.21 km³), while the woodland consumes the least (0.072 km³). The water consumption per unit area of forested land is the highest, reaching 190 m, and the water consumption of low coverage grassland is the lowest, only reaching 50 m. Vegetation distribution change could be the main influencing factor of vegetation water consumption change in Yanhe River Basin. Through the establishment of the sustainable development path of ecological space with water as the core, the high-quality development of ecological environment in arid and semi-arid areas will be achieved.

2. Appropriately expand the discussion section.

Reply:  the discussion section are modified as follows:

Therefore, the significance of this study is stated as follows. It is necessary to think deeply about the sustainable development of ecological space and guide the regional ecological space development in a healthier, more harmonious, more stable and more sustainable way. Based on the actual demand raised from water shortage in arid and semi-arid areas, this study quantifies the increase in water consumption caused by ecological space changes and pays attention to the ecological space change and its impact on water resources under the guidance of policies. In addition, the calculation of water demand for ecological space reduces the impact of human subjective evaluation and improves the scientific and objective identification results of ecological space management to a certain extent. In the development process of arid and semi-arid areas, most of them face the problem that the construction of ecological space is not coordinated with the distribution of water resources. The temporal and spatial distribution of vegetation water consumption will directly determine the combination efficiency and construction mode of water resources and ecological space elements during the development. The section on ecological space management under the constraint of regional water resources can serve as a reference for the construction of ecological space in other arid and semi-arid regions.

Despite its significance, this study still has the following limitations. Although the spatial expression of vegetation water consumption in the Yanhe River basin has been realized on a spatial raster scale of 30m, more accurate vegetation water consumption research needs to be carried out at more scales considering the scale effect in landscape ecology research. Investigations about vegetation water consumption with higher spatial resolution can make up for the loss of local information in large-scale research, leading to a clearer understanding of vegetation water consumption. In addition, although existing research and experiences from experts have been considered, there are still some shortcomings when determining the vegetation coefficient. Under the condition of given data collection, future research can use more accurate data and scenario analysis to select the most appropriate one from different ecological spatial distribution scenarios.

3. Further optimize the expression of the conclusion.

Reply:  the conclusion has been checked and modified.

The modifications are as follows: 

This study shows that in arid and semi-arid areas, the sustainable development of ecological space requires to figure out the relationship between the available water resources and water consumption in the regional ecological space.Based on the analysis of the water consumption of vegetation in Yanhe River basin in Shaanxi Province, it is found that the annual water consumption of vegetation in Yanhe River basin is on the rise from 2000 to 2020, indicating that the water resources in the study area have continued to decline in recent years, and ecological construction should be re examined in the future. Affected by the policy of returning farmland to forests, the forest land along the upper reaches of the river has increased excessively. The increasing trend of vegetation water consumption in the upstream is more obvious than that in the downstream.If conditions permit, the optimization and control of ecological space should be carried out. It is necessary to pay attention to spatial fine governance and regional differential development in the construction of regional ecological space. In Ansai and Baota area, priority should be given to vegetation types with low water consumption after returning farmland to improve grassland coverage.This shows that policies in the upstream areas in the future should focus on farmland protection rather than expanding forest land. Grassland should be the first choice for restoring ecological space. In the future, it is very necessary to reduce water use in semi-arid areas. Although the water consumption of vegetation in Yanchang area fluctuates slightly, the proportion of forest land should be controlled.To sum up, the increase in vegetation water consumption indicates that the spatial distribution of vegetation types in the watershed ecological space is unreasonable. The policy of returning farmland to forests and the development of the region have led to a huge change in vegetation water consumption, and the increase in forest land is the main reason for the change trend of water consumption. Nowadays, the focus of regional ecological space planning has changed from the increase in vegetation coverage to the coordination between water resource carrying capacity and spatial planning, digging out the key elements of urban green space. This study has a certain reference value for other similar regions regarding planning and management, and ecological land delimitation, and can be widely used in the planning and management of ecological space in arid and semi-arid regions.

4.Figure 7 The content is inconsistent with the title (2018?, 2020?)

Reply:

The modifications are as follows:

（Please see the word file）

Author Response File: Author Response.pdf

Reviewer 3 Report

After the previous review, the manuscript has been improved, however, there are still some points to attend:

1. The abstract is too long, please reduce it.

2. The discussion section is very limited (only two paragraphs) 

Author Response

Reviewer3 ：

After the previous review, the manuscript has been improved, however, there are still some points to attend:

1. The abstract is too long, please reduce it.

Reply: Thank the reviewers for their comments, and the abstract has been checked and modified.

The modifications are as follows:The sustainable development in arid and semi-arid areas is largely constrained by water resources. Expanding ecological space is considered as an effective way to conserve water resources. The innovation of this study is the analysis of water consumption in different land use types from a complete watershed scale, which can evaluate space management under the background of returning farmland to forests during the past 20 years, and provide suggestions for future space management in semi-arid areas.Based on the meteorological data and GIS technology, the current study quantitatively analyzes the spatial and temporal variation characteristics of water consumption of different vegetation growth stages in Yanhe River Basin by using the improved Penman formula. The results show that the water consumption of vegetation in Yanhe River Basin increases from 0.44km³ in 2000 to 0.68km³ in 2020. The water consumption of vegetation showed obvious spatial heterogeneity, with the highest value in the central Baota area (1.094 × km³) following by western Ansai region (0.727km³), whereas the consumption in eastern Yanchang area is relatively low (0.483km³). In addition, the annual average water consumption is (0.381 km³). The cultivated land consumes the most water (0.21 km³), while the woodland consumes the least (0.072 km³). The water consumption per unit area of forested land is the highest, reaching 190 m, and the water consumption of low coverage grassland is the lowest, only reaching 50 m. Vegetation distribution change could be the main influencing factor of vegetation water consumption change in Yanhe River Basin. Through the establishment of the sustainable development path of ecological space with water as the core, the high-quality development of ecological environment in arid and semi-arid areas will be achieved.

2. The discussion section is very limited (only two paragraphs) 

Reply: discussion section has been checked and modified.

The new paragraphs are as follows:Therefore, the significance of this study is stated as follows. It is necessary to think deeply about the sustainable development of ecological space and guide the regional ecological space development in a healthier, more harmonious, more stable and more sustainable way. Based on the actual demand raised from water shortage in arid and semi-arid areas, this study quantifies the increase in water consumption caused by ecological space changes and pays attention to the ecological space change and its impact on water resources under the guidance of policies. In addition, the calculation of water demand for ecological space reduces the impact of human subjective evaluation and improves the scientific and objective identification results of ecological space management to a certain extent. In the development process of arid and semi-arid areas, most of them face the problem that the construction of ecological space is not coordinated with the distribution of water resources. The temporal and spatial distribution of vegetation water consumption will directly determine the combination efficiency and construction mode of water resources and ecological space elements during the development. The section on ecological space management under the constraint of regional water resources can serve as a reference for the construction of ecological space in other arid and semi-arid regions.

Despite its significance, this study still has the following limitations. Although the spatial expression of vegetation water consumption in the Yanhe River basin has been realized on a spatial raster scale of 30m, more accurate vegetation water consumption research needs to be carried out at more scales considering the scale effect in landscape ecology research. Investigations about vegetation water consumption with higher spatial resolution can make up for the loss of local information in large-scale research, leading to a clearer understanding of vegetation water consumption. In addition, although existing research and experiences from experts have been considered, there are still some shortcomings when determining the vegetation coefficient. Under the condition of given data collection, future research can use more accurate data and scenario analysis to select the most appropriate one from different ecological spatial distribution scenarios.