Soil Water Dynamics Under Different Land Uses in Loess Hilly Region in China by Stable Isotopic Tracing

Round 1

Reviewer 1 Report

Soil water dynamics under different land uses in loess hilly region in China by stable isotopic tracing Kang Du, Beiying Zhang,*and LinjuanLi1

Abstract:

The Abstract is well-written. The Authors fully describe the problem being addressed and summarize the methodology used in the research study. The researchers effectively used isotope composition to arrive at an understanding of the ground-surface “water balance” under different land use types.

A couple of minor suggestions: I prefer if the Authors avoid using personal pronouns such as “we”, in technical writing. Also, should the words, “soil water” be hyphenated?

Introduction

A well-written Introduction along with a thorough and focused literature review.

Materials and Methods

Components are: the Study area, sampling methods, water content measurement, stable isotope composition measurements, calculation of water supply (supply is mis-spelled in text), and statistical analysis.

Results

Results are presented under: Stable isotopic composition of soil water in different land use types, and vertical distribution characteristics of stable isotopes in soil-water. Figures 4 and 5 illustrate well, the extensive nature of the research study. However, I personally prefer to see the use of “grid-lines”, when technical data is presented.

Discussion

The analysis and explanation of the soil measurements is clearly presented. I would note that I think the last Figure is wrongly numbered. It is presented as Figure 4 but I believe that it should be Figure 7. Once again my personal preference would be to have grid-lines shown on the last Figure.

The presentation of the Discussion section is under the headings: Soil-water movement and transformation, and influence of land use type on soil-water dynamics. The discussion is sufficient and well-focused.

Conclusions

The Authors have been successful in providing information supporting the initial Objectives of the paper. The have provided confirmation of ground surface water balance as it pertains to woodland, grassland, shrubland and cropland types of surface vegetation. The identification of the importance of matrix flow and preferential flow during infiltration is impressive.

The manuscript is brief and to the point. It is an excellent manuscript and I recommend its publication with only a few minor changes, at the Authors discretion.

Authors contributions: Covered

Funding: Acknowledged

Acknowledgements: Good but one name, X.X. missing!

Conflict of Interest:   None

References

40 references (thorough)

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Reviewer 2 Report

The manuscript entitled “Soil water dynamics under different land uses in loess hilly region in China by stable isotopic tracing” (Reference number Water-10060336) authored by K. Du, B. Zhang and L. Li describes the results from a field survey in which stable isotopes were used for assessing soil water dynamics under four different land uses (cropland, shrubland, grassland and woodland) in an arid region of China. The authors concluded that the difference evaporation rate was the main driver for the differences in soil water dynamics under the studied land uses. The manuscript fits well within the scope of Water.

However, the manuscript cannot be accepted for publication in its present form because it presents several flaws that need to be corrected. Methods are not clearly described and some details need to be included in this section. The experimental design and sample collection seems to be not correct, as the authors collected soil from several sites but rainfall from just one site, quite far away from the woodland sampling site, so the discussion and conclusions need to take this into account. The statistical analysis has not been clearly stated in the Materials and Methods section and it has not been clearly presented in the Results section. Discussion is weak and needs improvements. Moreover, some conclusions are exaggerated with regard to the results obtained. I detected some references missing.

Finally, English needs a thorough revision all over the manuscript.

Therefore, I recommend a comprehensive major revision of this manuscript because it does not meet the high-quality standards for being published in Water.

 

Specific comments to the authors:

 

Abstract:

Line 12: Why “obviously”?

Lines 13-14: Please, check English in this sentence and re-phrase it.

Line 18: “was” instead of “were”.

Lines 18-20: This sentence does not make sense since you present a rank order and not a ratio.

Lines 23-24: This sentence does not make sense. What do you mean by “better”? Better than what?

 

Keywords:

Please, avoid the use of words that already appear in the title.

 

Introduction:

Line 28: I would remove “As part of the water cycle”.

Line 29: Why only in arid regions?

Line 29: Include “only” after “originates”.

Line 30: Remove “only” before “in most”.

Lines 30-31: What do you mean by “precipitation mixed soil water”?

Line 34: There are other works in other areas that explain the effect of land use on soil water dynamics (Mestas-Valero et al., 2012; Zheng et al., 2016).

Line 45: “Stable isotopes have been widely employed” instead of “Many scholars use stable isotopes”.

Line 55: “depended” instead of “depend”. I would remove “in addition to soil water”.

Lines 56-58: Again, Mestas-Valero et al. (2012) and Zheng et al. (2016) can be cited here.

Lines 58-59: “Research on soil moisture in the Loess Plateau of China has been conducted” instead of “In research on soil moisture in the Loess Plateau of China, many studies have been conducted”.

Line 63: The objective of the study, and its relevance, must be clearly stated at the end of the Introduction section.

 

Materials and Methods:

This section requires improvements and clarifications.

Moreover, the equations should have one number and not two: “(1)” instead of “(1) (1)”. Please, correct this for all the equations.

Line 66: “mountain testing ground”, what do you mean?

Line 73: “between July and September” instead of “in months of July-September”.

Line 74: What do you mean by “The vegetation zoning”?

Line 76: “serious soil and water loss affected by human activities”, this construction is strange. Please, modify to “affected by soil and water loss due to human activities”.

Lines 80-81: This is confusing and can lead to misunderstandings. Please, re-phrase.

Figure 1: The caption is incomplete. What do the symbols for groundwater and precipitation mean?

Lines 88-89: This sentence can be removed because this information has been given in the previous sub-section.

Line 92: Remove “station”.

Lines 95-97: Why these different number of samples for precipitation and groundwater? According to figure 1, precipitation samples were collected close to three of the soil sampling sites, but far from the other one, why? Similarly, groundwater samples were collected rather far from the soil sampling sites. These facts need to be justified in the text as they can affect the results and the relationships obtained.

Line 99-101: Why did you store samples refrigerated and not frozen? This needs citations. Maybe, Mirás-Avalos et al. (2015).

Line 104: Why only for 12h? The usual method is for 24h.

Line 105: “weight” instead of “quantity”.

Line 106: “weight” instead of “mass”.

Line 111: “CAS & MWR” have not been defined.

Line 115: “D/H” has not been defined.

Line 117: “supply” instead of “supploy”.

Line 120: After the citations, use a dot and separate the sentence in two.

Line 122: Include “is” before “as follows”.

Lines 123-125: This is unclear. If A, B and C are precipitation, soil water and groundwater, respectively. Why do V_A and V_B are the amounts of precipitation and soil water? What are the units for A and for V_A?

Line 125: What do you mean by “recharge proportion”?

Lines 127-129: This needs a comprehensive re-writing because it is not explanatory. How was the significance analysis performed? Which test? What graph?

 

Results:

This section mixes results and discussion, and even introduction. Authors should only describe the results in this section, otherwise they should merge the Results and the Discussion sections.

Lines 133-134: These mean values do not appear in Table 1.

Line 135: Remove “obviously”.

Lines 137-138: Remove “followed by soil water”.

Lines 138-139: Simplify this sentence to “Groundwater is more stable, with standard deviations of dD and d¹⁸O of 6.32 ‰ and 1.13 ‰, respectively”.

Table 1: Re-phrase the title to “Stable isotopic composition of soil water from four different land uses, precipitation and groundwater”. Why “Cropland” is in bold letters?

Line 141: Why is this obvious and what are those characteristics?

Lines 142-143: Re-phrase, not clear.

Lines 144-145: Remove, this is repeated.

Figure 2: Re-phrase the caption for this figure because it does not make sense and it is not explanatory.

Line 149: The first sentence can be removed.

Lines 150-151: Move “was observed” to after “stable isotopes”. Include “layer” after “shallow”.

Line 151: “deepest” instead of “deep”.

Line 153: “layer” instead of “level”.

Line 154: Include “the” before “four land”.

Line 156: “layer” instead of “area”.

Lines 158-163: These are neither results nor discussion. I would remove it. Otherwise, English must be checked and re-phrased.

Line 164: “in shrubland” instead of “of shrubland”.

Lines 165-167: Check English or remove, since these are not results.

Lines 169-171: Messy and confusing.

Line 174: What do you mean by “to be stable low”?

Lines 174-181: Apart from the fact that English needs improvements, these are not results, but discussion.

Figure 3: In the Y-axis, what do you mean by “variation”? What about the statistical analysis for comparison? The caption is not explanatory.

 

Discussion:

This section mixes discussion with results. As I mentioned before, authors should either separate both sections or merge them, but not present them as they did in this manuscript.

Line 193: “in the form of matrix”, what do you mean?

Line 194: “local atmospheric precipitation line”, what do you mean?

Lines 195-196: These are results, not discussion.

Lines 199-202: Unclear and confusing. Please, re-phrase it.

Lines 202-209: These are results, but not discussion.

Table 2: Include “under different land uses” at the end of the title.

Lines 215-220: This is an introduction but not a discussion.

Line 228: How do you know this? You only collected rainfall samples on one site, while soil samples were collected on four different sites.

Line 229: Are you sure about this?

Lines 231-234: Check English. This sentence does not make sense.

Lines 235-236: These are results, but not discussion.

Line 237: “were larger and faster”, what do you mean?

Lines 238-240: Apart that this is confusing, your results may indicate or suggest this, but they did not prove it.

Line 242: Do you mean that water evaporated from the woodland but not from the other land uses?

Lines 243-245: Check English and re-phrase.

Line 246: This is figure 7 and not figure 4. I do not see much difference in these relationships among the different land uses.

 

Conclusions:

This section is a mere repetition (almost word by word) of results and discussion.

Line 250: The first sentence can be removed.

Line 251: “followed this rank order” instead of “was as follows”.

Line 254: Remove “type”.

Lines 261-264: What? Are you telling us that woodland is bad for agricultural production?

You should comment not only on land use type, but also on vegetation cover. This alters evaporation rates, as well as water infiltration in the soil and the velocity of rainfall when reaching the soil. Which one of the land use types presented a lower surface of soil covered by vegetation?

 

References:

Edit the references according to journal guidelines (check bold and italics in years, abbreviated journal titles, etc.)

Lines 312-313: Include the volume number and the page numbers.

Lines 348-349: Include the volume number and the page numbers.

 

Some references that can be useful:

Mestas-Valero, R.M. et al. Estimation of the daily water consumption by maize under Atlantic climatic conditions (A Coruña, NW Spain) using frequency domain reflectometry – a case study. Nat. Hazards Earth Syst. Sci. 2012, 12, 709-714; doi: 10.5194/nhess-12-709-2012

Mirás-Avalos, J.M. et al. Temporal oscillation and losses of three carbon forms in a microcatchment of NW Spain. Comm. Soil Sci. Plant Anal. 2015, 46(sup1), 296-308; doi: 10.1080/00103624.2014.989049

Zheng, W. et al. Improving yield and water use efficiency of apple trees through intercrop-mulch of crown vetch (Coronilla varia L.) combined with different fertilizer treatments in the Loess Plateau. Span. J. Agric. Res. 2016, 14(4), e1207; doi: 10.5424/sjar/2016144-9575

 

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Round 2

Reviewer 2 Report

The revised version of the manuscript entitled “Soil water dynamics under different land uses in loess hilly region in China by stable isotopic tracing” (Reference number Water-10060336-v2) authored by K. Du, B. Zhang and L. Li represents a considerable improvement from the original submission. The authors have considered all my comments and suggestions, as well as those from another reviewer, and performed modifications in the text according to them. Moreover, the authors have answered my concerns rather satisfactorily.

I appreciate the efforts made by the authors for improving their manuscript and congratulate them on their work.

Therefore, I recommend a minor revision of this manuscript prior to be accepted for publication in Water.

 

Specific comments to the authors:

Abstract:

Line 13: “showed” instead of “show”.

Line 25: “can recharge the soil water better than precipitation on woodland”. I suggest avoiding the use of “better” in scientific articles. Therefore, I suggest re-phrasing to “can recharge more soil water than on woodland”.

 

Introduction:

Line 42: What is “D”? I think that there is a mistake and should be delta “d”. Please, correct if necessary.

Line 63: “investigated” instead of “studied”.

 

Materials and Methods:

Lines 88-90: Please, re-phrase the caption for figure 1 to: “Location of the study area and the sampling sites: Precipitation (p), Groundwater (g1, g2, g3) and soil (s1, cropland; s2, grassland; s3, shrubland; s4, woodland)”.

Line 92: “taken with” instead of “taken by”.

Lines 98-100: This sentence needs re-phrasing. I suggest: “The distance between sampling sites was less than 1000 m and, therefore, we considered that all sampling sites were subjected to the same precipitation regime and received the same rainfall amount”.

Lines 102-103: What do you mean by “various”? If you refer to groundwater samples, you can remove “various”.

Line 136: “layer”, do you mean soil depth?

 

Results:

Line 145: Include “the fact that” before “the water vapor source”.

Lines 151-152: “clearly decreased (p < 0.05) over time” instead of “have obvious decreasing characteristics (p < 0.05) with temporal variation”.

Line 156: Remove “The” before “temporal” and include “over the current study” at the end of the sentence.

Line 163: “land uses” instead of “land use types”.

Line 170: “due to” instead of “which is because”.

Lines 171-172: Remove “the middle layer and the deeper layer were less”.

Line 176: “persistently at low values” instead of “persistent low value”.

Line 178: “under the four land uses considered in the current study” should be added at the end of the caption.

Figure 5: What is the date of the measurements shown in these graphs? Please, indicate it in the caption.

Line 190: Include “this rank order” after “follows”.

 

Discussion:

Lines 217-218: I suggest re-phrasing this sentence to “Therefore, groundwater is recharged by a mixture of precipitation and soil water rich in heavy isotopes [7]”.

Line 238: “are considered to be the same” instead of “are the same”.

Lines 245-247: Indicate if these values are averages for all depths in the soil profile and if they refer to the whole study period or to a given date.

Line 248: Remove “that” after “proves”.

Lines 253-255: Re-phrase to “In contrast, the degree of evaporation and fractionation of soil water in woodlands was high, the amounts of water received through small precipitation events evaporated rapidly and did not infiltrate in the soil”.

Line 257: “Relationships” instead of “Relationship”.

 

Conclusions:

Lines 267-269: Re-phrase to “However, the degree of evaporation and fractionation of soil water in woodlands was high and small precipitation events were not able to infiltrate and recharge deep soil layers”.

Line 269: “Moreover” instead of “Meanwhile”.

Line 271: Re-phrase to “Consequently, only heavy precipitation events could recharge soil water in woodlands”.

 

References:

Line 305: “Coronilla varia” should be in italics.

Line 354: The title of this journal is “Natural Hazards and Earth System Sciences”.

 

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Round 3

Reviewer 2 Report

The second revised version of the manuscript entitled “Soil water dynamics under different land uses in loess hilly region in China by stable isotopic tracing” (Reference number Water-10060336-v3) authored by K. Du, B. Zhang and L. Li represents an improvement from the previous version. The authors have considered all my comments and suggestions, and performed modifications in the text according to them.

I appreciate the efforts made by the authors for improving their manuscript and congratulate them on their work.

Therefore, I recommend the acceptance of this manuscript in its present form for publication in Water.