Comparison of Different Methods to Estimate Canopy Water Storage Capacity of Two Shrubs in the Semi-Arid Loess Plateau of China
Round 1
Reviewer 1 Report
Review, about the manuscript by Hu Caihong, Zhang Xueli, Ding Xinmin, Yan Denghua and Jian Shengqi, entitled "Study on canopy water storage capacity of two shrubs in the 2 semiarid Loess Plateau of China" The MSis professionally good, the experiments and descriptions are completely good. There is no methodological error in it. The number of cases examined is also adequate, the statistical analysis is good and the final result is also significant, globally as well. I fully accept the results, their explanation, the results of the statistical analysis, the professional part, but the use of English language must be improved, thoroughly. I found many mispellings, mistakes in vocabulary, lack of concordance of subject and statement, these needs to be revised carefully.
Author Response
Thank you very much.We had professionally polished the manuscript in English. https://www.mdpi.com/authors/english
Reviewer 2 Report
I have attached a WORD version of the manuscript with track changes and comments to help improve it. My main comments/suggestions are listed below.
11. I suggest that the authors have the manuscript reviewed by a native English speaker to improve readability. There are many words or phrases used that are not clear to the reader what is meant.
22. I have suggested the authors consider referring to methods used in the title of the manuscript. That is an important part of the study.
33. There are several vague statements. In the introduction for example: “Shrub interception losses in arid and semi-arid regions with little rainfall may play a more important role in their ecosystems….” But there is no detail on why this is. Is because storge capacity is a greater proportion of total rainfall? Or that the ecosystems are water limited? Please include some detail.
44. Climate for the location is quoted in annual figures only – and provide the reader with no insight into the seasonal or monthly climate of this semi arid (and presumably water-limited) location.
55. Methods used in the study are not always described fully or in sufficient detail. For example, it is not clear how the study plots were selected within the plantations. Also, it is not clear for how long simulated rainfall was applied at a given rainfall intensity. It is also not clear if the canopy was allowed to dry between simulated rainfall events.
66. There is reference to 10 x 10m plots, but then later, plots of 100 x 100 m are mentioned without any detail on how or why they were selected.
77. There is no information provided on how leaves were scanned for the scale-up method.
88. Vague statements are made eg: “… under wet conditions, the canopy did not affect the total water storage” What is meant by ‘wet conditions’ and what aspect of the canopy does not affect it?
99. Line 286. I am not sure why evapotranspiration was calculated. I would have thought you would be interested in evaporation only (and not transpiration).
110. Line 289: I’d expect ET to represent a much greater proportion (than 10%) of rainfall in a semi-arid environment.
111. The discussion section is faily light, and does not provide much insight into the results – why the results are the way they are, nor does the discussion provide the level of detail in relating/comparing this study to others.
112. In some cases the text repeats data shown in tables or figures, that decrease readability. I have made suggestions via track changes.
Comments for author File: 
Comments.docx
Author Response
- I suggest that the authors have the manuscript reviewed by a native English speaker to improve readability. There are many words or phrases used that are not clear to the reader what is meant.
A: Thank you very much.We had professionally polished the manuscript in English. https://www.mdpi.com/authors/english
- I have suggested the authors consider referring to methods used in the title of the manuscript. That is an important part of the study.
A: Thank you very much. We had revised the title according to the comments. “Comparison of different methods to estimate canopy water storage capacity of two shrubs in the semiarid Loess Plateau of China”
- There are several vague statements. In the introduction for example: “Shrub interception losses in arid and semi-arid regions with little rainfall may play a more important role in their ecosystems….” But there is no detail on why this is. Is because storge capacity is a greater proportion of total rainfall? Or that the ecosystems are water limited? Please include some detail.
A: We had revised the sentences as follow “Shrub interception losses in arid and semi-arid regions with little rainfall may play a more important role in their ecosystems, because the ecosystems are water limited, but their water storage capacity rarely has been reported”
- Climate for the location is quoted in annual figures only – and provide the reader with no insight into the seasonal or monthly climate of this semi arid (and presumably water-limited) location.
A: We had revised lines 87-92 as follow “This region belongs to the semi-arid-climate zone in the middle temperate zone, with an average annual temperature of 6.3°C, extreme maximum temperature is 34.3℃, and the lowest temperature is -27.1℃. An average annual precipitation of 427 mm, precipitation in July, August and September accounts for 58% of the annual precipitation, and mostly in the form of heavy rain, easy to form soil erosion. An monthly sunshine duration of 200 h, and an average monthly evaporation of 125.8 mm. Vegetation in the catchment belongs to the arid-zone forest grassland belt.”
- Methods used in the study are not always described fully or in sufficient detail. For example, (1)it is not clear how the study plots were selected within the plantations. (2)Also, it is not clear for how long simulated rainfall was applied at a given rainfall intensity. (3) It is also not clear if the canopy was allowed to dry between simulated rainfall events.
A: (1) We revised lines104-109 as follow “Table 1 provided basic information on the C. korshinskii and H. rhamnoides plots. The results showed that significant differences were observed among the shrub species for all the biometric characters examined except basic diameter-twig. We selected three plots with size 10 × 10 m for C. korshinskii and H. rhamnoides, respectively in the experimental plantation (100 × 100 m) based on the averaged measured results of Table 1”
- We had revised lines 246-257 as follow “We assumed that the amount of water stored in the shrub canopy would increase with an increase in rainfall intensity. Therefore, the canopy under wet conditions, did not affect the total water stored in each test stage with the consecutive higher rainfall intensity, i.e., the canopy storage water is the sum of the water intercepted by the canopy from a dry state to a wet state. Each simulated rainfall treatment started with the lowest intensity (1.04 mm h-1) until the weight reached a stable state. We then turned off the simulator for 5 minutes to facilitate the escape of excess water from the plant. The aim was not to return to initial dry conditions, rather to allow excess water to leave the plant. The rainfall intensity was then increased to 1.68 mm h-1, and so on until 10.25 mm h-1were reached. When the weight increase of vegetation specimens retained steady-state storage at the last rainfall of 10.25 mm h-1, the rainfall simulator was immediately turned off. At the same time, two ventilators were turned on, all doors and windows opened to enable quick specimen drying for subsequent biometric variable determination.”
- No need to be completely dry, no gravity water.
- There is reference to 10 x 10m plots, but then later, plots of 100 x 100 m are mentioned without any detail on how or why they were selected.
A: The selection of 100*100 m sample plot is to determine the average canopy characteristics of the vegetation of the plantation and provide a basis for the selection of a small sample plot (10*10m).
- There is no information provided on how leaves were scanned for the scale-up method.
A: We had revised line 182 as follow “We lay the leaves flat on the scanning equipment, avoid overlap and imported the scanned images into ArcGIS 10.5”
- Vague statements are made eg: “… under wet conditions, the canopy did not affect the total water storage” What is meant by ‘wet conditions’ and what aspect of the canopy does not affect it?
A: We had revised lines 246-257 as follow “We assumed that the amount of water stored in the shrub canopy would increase with an increase in rainfall intensity. Therefore, the canopy under wet conditions, did not affect the total water stored in each test stage with the consecutive higher rainfall intensity, i.e., the canopy storage water is the sum of the water intercepted by the canopy from a dry state to a wet state. Each simulated rainfall treatment started with the lowest intensity (1.04 mm h-1) until the weight reached a stable state. We then turned off the simulator for 5 minutes to facilitate the escape of excess water from the plant. The aim was not to return to initial dry conditions, rather to allow excess water to leave the plant. The rainfall intensity was then increased to 1.68 mm h-1, and so on until 10.25 mm h-1 were reached. When the weight increase of vegetation specimens retained steady-state storage at the last rainfall of 10.25 mm h-1, the rainfall simulator was immediately turned off. At the same time, two ventilators were turned on, all doors and windows opened to enable quick specimen drying for subsequent biometric variable determination.”
- Line 286. I am not sure why evapotranspiration was calculated. I would have thought you would be interested in evaporation only (and not transpiration).
A: Sorry to make you confused, this is a mistake in our expression, here is the amount of evaporation during rainfall. We had revised them in the manuscript.
- Line 289: I’d expect ET to represent a much greater proportion (than 10%) of rainfall in a semi-arid environment.
A: Here is the amount of evaporation during rainfall.
- The discussion section is faily light, and does not provide much insight into the results – why the results are the way they are, nor does the discussion provide the level of detail in relating/comparing this study to others.
A: We had added two paragraphs in section 4.2 as follow:
As for the research on canopy water storage capacity, some researchers said that the water absorbed by tree trunks should not be considered [28], while others believed that in arid and semi-arid regions, the water absorbed by tree trunks could reach about 16% of the water retained by canopy [29]. The canopy water storage capacity calculated by scale-up method in this study is the maximum canopy water storage capacity under ideal conditions, but the actual canopy water storage capacity cannot reach the maximum water storage capacity in many cases. The actual canopy water storage capacity is mainly affected by stand status, and rainfall characteristics will also affect the canopy water storage capacity. For example, in the case of short duration of heavy rainfall, it is difficult to achieve the maximum canopy water storage capacity. Therefore, the actual canopy water storage status should be considered in the application of scale-up results. Pereira regression analysis method mainly utilizes observation data of precipitation outside the forest and throughfall. The observation error of throughfall is large, observation equipment and the arrangement of observation points will affect the measurement of throughfall. Rainfall events considered by Pereira regression analysis method need to meet canopy saturation. Gash et al. [20] described the process of canopy interception as canopy unsaturation--canopy saturation--stemflow generation, and comprehensively considered rainfall characteristics outside the forest and maximum water storage capacity of trunks during observation. The maximum canopy water storage capacity obtained by Pereira regression analysis method is between that obtained by scale-up method and simulated rainfall method. It can be considered that the canopy water storage capacity obtained by Pereira regression analysis method is reasonable.
According to the regression analysis method, each precipitation event may not have caused the canopy to achieve the canopy water storage capacity. Generally, the leaves and branches of the canopy easily reached the maximum canopy water storage capacity, whereas the tree trunks needed to reach the maximum canopy water storage capacity under the heavy rainfall events. Therefore, the water storage capacity of the canopy estimated by the regression analysis method better reflected the canopy water storage capacity in the actual precipitation process. The simulation rainfall method could overcome the shortcomings of regression analysis method and the scale-up method.
- In some cases the text repeats data shown in tables or figures, that decrease readability. I have made suggestions via track changes.
A: We had revised section 3.4 as follow “Figure 7 shows an exponential regression relationship between water storage per leaf area, branch and trunk surface area (expressed in equivalent water depth), and simulated rainfall intensity (1.04, 1.68, 2.25, 3.58, 4.38, 6.75, 9.37, and 10.25 mm h−1). We found that in each simulated rainfall intensity, H. rhamnoides could intercept more water per trunk surface area than C. korshinskii, per branch surface area and leaf area; and C. korshinskii could store more water than H. rhamnoides. The canopy water storage capacity was 0.63 mm and 0.59 mm for C. korshinskii and H. rhamnoides, respectively. Canopy water storage showed an increasing trend with an increase in rainfall intensity in both C. korshinskii and H. rhamnoides”
Author Response File: Author Response.docx
Reviewer 3 Report
This manuscript reports on the analysis of the canopy storage capacity of two shrups in the semiarid area of the Loess Plateau of China. The results are important from the point of view of water management of vegetated areas. However, I have couple of suggestions to be considered by the Authors:
(1) Line 57/58: Please include more clear explanation about the Pereira regression analysis.
(2) Line 73: Please add explanation, why do You deal with the C. korshinskii and H. 73 rhamnoides, why it is importand for the China territory?
(3) Line 83: Does the catchment or Loess hills have an area of 2.98 km2??
(4) Line 85-86: These given numbers for precipitation and evaporation are strange. Please give a source of them. If precipitation is 427mm/y, evaporation cannot be 1510mm/y... Or You mean potential evaporation or reference evapotranspiration. I suggest to pay attention and to differentiate between evaporation and potential evaporation/reference evapotranspiration, and to correct the text to make it clear.
(5) Line 97: What is meant by "large areas"?
(6) Line 122: How was it secured that the weather station was placed in an area without an influence of scrub?
(7) Line 152: please correct this sentence
(8) Line 172: Please explain and describe what kind of and how the procedure was conducted in the ArcGIS
(9) Line 179-180: is this equation introduced first by You?? It would be nice that You mention, who was applying it before You. The same with equation no.3
(10) Line 198: Please refer to my comment No. 4., and correct the terms in the whole text, paying attention to the difference between evaporation (actual) and potential evaporation/reference evapotranspiration. Is transpiration during the rainfall period active or not?
(11) Line 198/199: "The following formula was obtained by Penman-Monteith equation:... please connect this sentence with former one. It is not clear for what purpose You are using this formula; Please explain how equation (7) is used and for what.
(12) Line 245: please correct, not clear sentence
(13) Line 249: "...general liner model", please correct
(14) Line 261: "...annual rainfall was 363.2 mm...) Please explain why it is so different from the number You have given in the line 85 (427 mm). Has the"rainfall" the same meaning as "precipitation" ?
(12) Line 286-288: as former suggestion: please be clear what kind of physical variable do You estimate by Penman-Monteith formula?
(13) Line 294: The hyphotheses should be formulated in the introduction, not here...
(14) Line 324-325: please consider if the term "trend" is appriopriate here
(15) Line 333: Please explain the meaning of S
(16) Table 4: Please explain "df"
(17) Table 5: what do you mean by the "hydrologic parameters"?
(18) Line 249: Is the"projected area" is different from the LAI?
Author Response
(1) Line 57/58: Please include more clear explanation about the Pereira regression analysis.
A: We had revised the sentences as follow: The Pereira regression analysis method considers the effect of evaporation rate on the maximum canopy water storage capacity of canopy during canopy interception. The maximum water storage capacity of forest canopy was calculated based on the linear relationship between canopy penetrating rainfall and precipitation outside the forest, and the mean evaporation and mean rainfall intensity after canopy saturation.
(2) Line 73: Please add explanation, why do You deal with the C. korshinskii and H. rhamnoides, why it is importand for the China territory?
A: We had added the sentences as follow: C. korshinskii and H. rhamnoides are the main shrub species for afforestation in Loess Plateau, China.
(3) Line 83: Does the catchment or Loess hills have an area of 2.98 km2??
A：We had revised the sentence as follow “The Anjiagou catchment has an area of 2.98 km2, which is surrounded by loess hills with altitude ranges from 1900 to 2250 m” .
(4) Line 85-86: These given numbers for precipitation and evaporation are strange. Please give a source of them. If precipitation is 427mm/y, evaporation cannot be 1510mm/y... Or You mean potential evaporation or reference evapotranspiration. I suggest to pay attention and to differentiate between evaporation and potential evaporation/reference evapotranspiration, and to correct the text to make it clear.
A: We had revised the sentences as follow: The Anjiagou catchment has an area of 2.98 km2, which is surrounded by loess hills with altitude ranges from 1900 to 2250 m. This region belongs to the semi-arid-climate zone in the middle temperate zone, with an average annual temperature of 6.3°C, extreme maximum temperature is 34.3℃, and the lowest temperature is -27.1℃. An average annual precipitation of 427 mm, precipitation in July, August and September accounts for 58% of the annual precipitation, and mostly in the form of heavy rain, easy to form soil erosion. An monthly sunshine duration of 200 h, and an average monthly water surface evaporation of 125.8 mm.
(5) Line 97: What is meant by "large areas"?
A: We had deleted the sentence.
(6) Line 122: How was it secured that the weather station was placed in an area without an influence of scrub?
A: Not every part of the region has plantations, which are distributed in blocks with a certain distance between them.These distances are generally bare.Install a weather station at this location, not affected by vegetation.
(7) Line 152: please correct this sentence
A: We had revised the sentence as follow: we measured throughfall and stemflow immediately after each rainfall event.
(8) Line 172: Please explain and describe what kind of and how the procedure was conducted in the ArcGIS
A: We had revised the sentence as follow: We lay the leaves flat on the scanning equipment, avoid overlap and imported the scanned images into ArcGIS 10.5 to obtain the pixel value range of the leaf, count the number of pixel of the leaf, and compare with the pixel value of the picture. Establish the model and batch process to obtain the leaf surface area.
(9) Line 179-180: is this equation introduced first by You?? It would be nice that You mention, who was applying it before You. The same with equation no.3
A: We had added the sentence as follow: Peng et al. (2011) [27] used following method to calculate canopy water storage capacity.
(10) Line 198: Please refer to my comment No. 4., and correct the terms in the whole text, paying attention to the difference between evaporation (actual) and potential evaporation/reference evapotranspiration. Is transpiration during the rainfall period active or not?
A: Thank you. The evaporation calculated in this paper is the amount of canopy interception evaporation during rainfall. We had revised evapotranspiration to evaporation.
(11) Line 198/199: "The following formula was obtained by Penman-Monteith equation:... please connect this sentence with former one. It is not clear for what purpose You are using this formula; Please explain how equation (7) is used and for what.
A: We used equation (7) to calculate E (evaporation). We had revised the sentence as follow: where R is rainfall intensity (mm/h) and E is the evaporation of saturated canopy (mm), which was obtained by Penman-Monteith equation:
(12) Line 245: please correct, not clear sentence
A: We had revised the sentence as follow: When P < 0.05, significant differences were attributable to the shrub types.
(13) Line 249: "...general liner model", please correct
A：We had revised the sentence as follow: Two-way ANOVA was used to test the main and interaction effects of shrub species and biological parameters on water storage capacities.
(14) Line 261: "...annual rainfall was 363.2 mm...) Please explain why it is so different from the number You have given in the line 85 (427 mm). Has the"rainfall" the same meaning as "precipitation" ?
A: line 85 (427 mm) is the precipitation (rainfall+snow); line 261 is the rainfall from May to September. We had revised the sentence as follow: The average annual rainfall (from May to September, 201-2018) was 363.2 mm.
(12) Line 286-288: as former suggestion: please be clear what kind of physical variable do You estimate by Penman-Monteith formula?
A: Thank you very much. We had revised evapotranspiration to evaporation.
(13) Line 294: The hyphotheses should be formulated in the introduction, not here...
A: We had deleted the sentence.
(14) Line 324-325: please consider if the term "trend" is appriopriate here
A: We had revised “trend” to “characteristics”.
(15) Line 333: Please explain the meaning of S
A: S, absolute water store capacity. We have added them to the manuscript.
(16) Table 4: Please explain "df"
A: df, degree of freedom. We have added them in Table 4.
(17) Table 5: what do you mean by the "hydrologic parameters"?
A: We had deleted the sentence in caption of Table 5.
（18）Line 249: Is the"projected area" is different from the LAI?
A: “projected area” is different from “LAI”. projected area is the area surrounded by the contour of the shadow. LAI, leaf area index, the ratio of total plant leaf area to land area.
Author Response File: Author Response.docx
