The Stable Isotopic Composition of Different Water Bodies at the Soil–Plant–Atmosphere Continuum (SPAC) of the Western Loess Plateau, China

Round 1

Reviewer 1 Report

Review of the manuscript water-563137

The Stable Isotopic Signal of Different Water Bodies at the Soil-Plant-Atmosphere Continuum (SPAC) of the Western Loess Plateau, China

by Cunwei Che, Mingjun Zhang *et al.

submitted to WATER

 

The authors present some interesting results on stable isotope composition, d²H and d¹⁸O, of waters in plants, precipitation, river and soil waters, and their interrelations. The topic is interesting and certainly suitable for publication in journal WATER.

The number of samples is quite large and the statistics is well applied to obtain relevant conclusions. Of course, it would be better if the whole year were taken for sampling, not just the period April – October. I understand that this period has been chosen because it is a plant growing season (line 62), but relations between precipitation and soil water would be interesting also during the rest of the year.

I wonder whether data on precipitation (35 pairs of data, April – October 2016) are the same samples presented in paper M. Du et al, WATER 2019, 11, 1441, Stable Isotope Ratios in Tap Water of a Riverside City in a Semi-Arid Climate: An Application to Water Source Determination. If this is true, that I suggest mentioning this in the paper.  If the data are the same, I am confused with slightly different LMWL equations.

Line 162 of this ms.     δ²H = (7.10 ± 0.34) δ¹⁸O + (5.50 ± 1.90), R2 = 0.92, n = 35

Du et al. 2019              δ²H = (7.08 ± 0.34) δ¹⁸O + (5.12 ± 1.90), r2 = 0.93, n = 35,

As well as slightly different latitude and longitude values.

The same question (are these the same data?) is valid also for the river water samples at the Zhongshan bridge.

The paper is well written and well organized, conclusions are justified, so I have no great problems with the ms, and my recommendation is minor revision before final accepting

However, I think that the authors may improve the work. I give some comments related to the line numbers of the submitted manuscript version.

Comments:

·                     Line 16 - Abstract – I would suggest using ”interrelations” instead of “interrelationships” – also later on several places “relationship” replace with “relation” – if  needed, consult with an English-speaking expert,

·                     Line 27 – replace “are” with “is” – Understanding … is

·                     Line 25 – phrase “The coefficient of determination of the correlation between…2 is unclear to me. I would suggest deleting “of determination” to have “The coefficient of the correlation between…”, which is a standard phrase. (It is valid also for lines 27 and 296)

·                     Line 30 – if possible, include d²H and d¹⁸O into keywords

·         Line 77 – could you add the type of the climate according to Köppen–Geiger climate classification system?

·         Line 88 – replace “water style” with “water type” – also in figure caption to Figure 5

·         Line 96 – “and the like” – does it mean that for some of the plants their species were determined, and for some (“the like”) not?

·         Line 99 – what does it men “the samples are guaranteed to be ...”? Who did this and how? For such a statement I would like to have some justification.

·         Line 124 – replace “has between performed” with “has been performed”

·         Lines 134 and 141 – add equation numbers, please

·         Lines 135 and 142 – where with lower case letter w

·         Captions to Figure 2 and Figure 3 – should explain what are panels a, b, c

·         In Figure 2 xylem water from all three plant types are shown as one group and the leaf water for all three types of plants (both collected at all 4 locations) as another group, while in Figure 3 both the xylem water and leaf water are distinguished by the type of plants, again at all four sampling locations. Figure 5 distinguishes xylem water of different plants and different locations. It is correctly understood? If yes, i would like to see similar explanation in the text to clarify presentations to the reader.

·         For all figures 2-6 – please, take care that symbols and unit should be written as
δ¹⁸O (‰) (no space between d and ¹⁸O or ²H, but with a space before (‰), similarly SWC (%) with a space before (%), depth (cm)

·         Line 232 – replace “what’s more” with “Moreover”

·         Line 241 – an awkward sentence. Whom or what does the water follow?  I would suggest skipping the first part of the sentence, and just add the short sentence “The water from the deep soil layers is the most depleted isotopically.” To the end of line 240.

·         This conclusion is corroborated with the data presented in Figure 4 for locations a, b and d. The lowest δ¹⁸O values at the bottom are about -10 ± 2 ‰. However, at location c, the δ¹⁸O values at 100 cm are between -6 and -7 ‰, while in the middle layer they are up to -8 ‰. So, in my opinion, location 3 is an exception, and I would like to see some comment here. 

·         Line 255 – replace “concluded” with “found” or “determined”

·         Line 258 – replace “in every” with “at each”

·         Line 290 – Figure 6 does not show relation between the precipitation amount and its δ¹⁸O values. The equations in lines 291, 293 – 295, are calculated, but not shown in Figure 6 or any other. And they do not need to be shown, since it is obvious that there is no correlation between the P and δ¹⁸O, or between δ¹⁸O in precipitation and those in soil water

·         Line 296 - coefficient of determination???

·         Line 295 – delete “from” or rewrite the sentence   

·         Line 314, caption to Figure 6 – this figure does not represent a relation between precipitation (amount) and δ¹⁸O values in different soil layers, but it represents monthly values of precipitation amount (left scale) and δ¹⁸O values of precipitation and water from different soil layers (right scale) (take care about axis descriptions!). I suppose that the soil water δ¹⁸O values are average values for all 4 locations?  

·         Line 320 – 322 – I do not think that repetition of all water lines is necessary here, pointing out differences in slopes and intercepts would do

·         Line 332 – replace “priority” with “primarily2

·         Lines 390-391 – this reference seems to be incomplete – what is this? A thesis? A book? A report?

·         Line 394 – what is [J]?

·         Add Du et al, 2019, Water 11, 1441, if the same data for precipitation and river water are used

·         Line 427 – prof. A A Argiriou is the coauthor of the paper, so I do not see the point of acknowledging his contribution – it seems that his valuable advice was valuable enough to be a coauthor of the manuscript.

Comments for author File: Comments.pdf

Author Response

We are very grateful to the reviewer's constructive comments and thoughtful suggestions for us. Based on these comments, we have made careful revision on the manuscript. The changes made to the text are highlighted in red so that reviewer may be easily identified. Please see the attachment of the revised manuscript.

 

Author Response File: Author Response.doc

Reviewer 2 Report

I have reviewed the manuscript entitled "The Stable Isotopic Signal of Different Water Bodies at the Soil-Plant-Atmosphere Continuum (SPAC) of the Western Loess Plateau, China" by Che et al. 

The authors provide a considerable number of isotopic measurements of plants waters, soil waters and river/rainfall waters. While the dataset looks interesting, some interpretations made by the authors are not convincing and the statistical treatment of the data is not suitable. Also, I am concern about the plant water results and potential spectrocopic interferences. This is not addressed in the manuscript. 

In my opinion, the structure of the manuscript is wrong. There is no difference between the results section and the discussion section. Please, find attached an annotated version of the manuscript with some comments that I hope the authors find useful. 

Comments for author File: Comments.pdf

Author Response

We are very grateful to the reviewer's constructive comments and thoughtful suggestions for us. Based on these comments, we have made careful revision on the manuscript. The changes made to the text are highlighted in red so that reviewer may be easily identified.

In our study, we used LWIA- Spectral Contamination Identifier (LWIA-SCI) software to do spectral contamination for the measured plants water data. Moreover, we reconstructed the structure between the results section and the discussion section. Please see the attachment of the revised manuscript.

 

Author Response File: Author Response.doc

Round 2

Reviewer 2 Report

I have reviewed the revised manuscript "The Stable Isotopic Composition of Different Water Bodies at the Soil-Plant-Atmosphere Continuum (SPAC) of the Western Loess Plateau, China". 

The authors have addressed many issues of the previous manuscript and now it reads much better. I still see a lot of data interpretations and discussion in the results section that I think should be moved to the discussion section (e.g. "it is necessary to discuss the mechanism between precipitation and soil water of
different depths" in discussion section 3.4...). Indeed, the results section is 5.5 pages long and the discussion section is only 1, what does not make much sense. I think papers benefit from well defined results and discussion sections. 

Also, find attached an annotated version of the manuscript with some minor comments. 

Comments for author File: Comments.pdf

Author Response

Dear expert:

We are very grateful to the editors and expert's constructive comments and thoughtful suggestions. In the latest revised manuscript, we have made revised to our results and discussion section, and response the question in annotated. The protocols are described in the attachment.

Author Response File: Author Response.doc