Quantitative Stable Isotope Tracing of Water Uptake in Cynanchum sibiricum during Its Growth Period in Arid Areas of Northwest China

Round 1

Reviewer 1 Report

I have thoroughly reviewed the  manuscript and found the topic as interesting. But there are many major and minor shortcomings which must be addressed before making the final decision. 
1- language quality is poor. authors have used large sentences, which make it difficult to understand. Moreover, there are also many grammatical mistakes. Therefore, it is advised to improve the language quality of the manuscript. 
2- Abstract section is too general. I could not found the problem, why this study was conducted. briefly explain methodology also. 
3- In introduction section, authors have reviewed the importance of water uptake and isotope quantitative tracing of water uptake, which has been well documented (as per author statement). But the importance of  Cynanchum sibiricum has not been discussed and why this species was chosen, have not been justified. Problem has not been well presented and justified. Authors must present and justify the problem here. 
4- Sampling methods and data collection procedure is not clear? it is not clear how traceable elements were used? where water with traceable O2 was used? this section needs more clarification.  Moreover, data collection procedure is also not clear. 
5- Research design is not presented well 
6- quality if figures is poor and most of the figures are not readable. improve the quality of figure, especially text presented on the figures. 
7- Tables and figures should be self-explanatory. give detailed caption of all the figures and tables. 
8- Conclusion seems a summary. It is be concrete, comprehensive, and a single paragraph 
9- Most of the references used are old. authors are suggested to include recent relevant literature to strengthen the hypothesis and to justify the results. 

Author Response

Dear reviewer,

Thank you very much for your valuable comments. I have studied them carefully and made point-to-point responses.

1- I have used one of the MDPI English editing services to improve the language quality of the manuscript (ID: English-42923) and then I checked the manuscript throughout. 

2 3- These two comments might be rather similar and I reply them together. The general scientific problem to be addressed of present research is arid vegetation roots water uptake, of which the significance on soil-vegetation-atmosphere eco-hydrological processes have been pointed out in Abstract and Instruction sections, respectively. Arid vegetation species with various functional types often develop different water use patterns, and Cynanchum sibiricum was chosen as the object as a typical represent of desert symbiotic twining rattan plant, which has been less concerned than tree and shrub species. Beside, another important characteristic of the paper is eliminating the significant short-term effect of pulse precipitation events on root water uptake. Relevant contents and further explanation have been presented. Comments on stable water methods also have been included and the detailed description has been presented in a following special section. Thus, I haven't worked out a proper method for the modification at this point. 

4 5- The overall research design is examining the relative uptake to various water sources (soil waters up to depth of 70 cm as well as rainfall) in three different relatively long time interval to a precipitation event. The field movements were conducted at three time points, respectively. Specific contents have been presented at 2.2 section. Isotopic data all were collected by sampling in the field and instrument measurement. Sampling and measurement procedure for various types also have been introduced at 2.2 section. About the isotope-based method used in current research, it has been presented at 2.3 section. 

6- I have redesigned the figures (Fig. 1, Fig. 3 and Fig. 4) and made some modifications on theme, improving the presentation and readability. Some adjustments also have been made to Table 1. 

7- I have made some necessary supplements in the legends of Fig. 2 and Fig. 3. 

8- I have made relevant modifications and this section has been composed to a single paragraph. 

9- In current manuscript, more than half of the references are from 2017 onwards and only four are before 2010 (mostly 2007/2008). Within a given time, we may not be able to consult and include most recent literature properly. 

The above is the current modified version. If necessary, I’d like to undertake further revision.

Reviewer 2 Report

This study examines the water uptake of Cynanchum sibiricum grown in arid areas of NW China by the use of hydrogen and oxygen stable isotope technology in order to. Even though much work has been done recently in this thematic area, the paper adds new information concerning the availability of water and its transportation mechanisms in tissues of specific plant grown in desert soils.

The presentation of the results is quite good, however the paper needs improvement.

I find the article useful from the agronomic point of view and I suggest that the manuscript should be accepted by MDPI-Water after making the suggested corrections concerning the Experimental Design and the Conclusions.

Experimental design

Symbiotic experiments should be made in order to examine the differential responses of Cynanchum grown alone or combined with other plant species e.g. Nitraria and Reed, and their interaction.

Conclusions

In this session the authors should limit themselves only to the conclusions raised by their results, e.g. lines 183-187, page 5 and lines 234-243, pages 7 and 8. Symbiotic speculations are better to be avoided or referred in the Discussion.

Author Response

Dear reviewer,

Thank you very much for your valuable comments. I have studied them carefully and made point-to-point responses. 

Experimental design

The Cynanchum sibiricum samples taken in present field campaign, in our impression, all from individuals combined with other plant species. The Cynanchum grown alone in the field, seem to be rarely seen. In future scientific efforts, we would pay more attention to this and Symbiotic experiments.

Conclusions

Expression related to symbiotic speculations has been deleted. 

The above is the current modified version. If necessary, I’d like to undertake further revision.

Round 2

Reviewer 1 Report

The authors have improved the manuscript. it can be accepted after minor revision. Following points need attentions.

1- Authors have satisfactoraly addressed the comments, but captions of the figure and tables can be further improved. In rule, figures and tables should be self-explanatory, and should contain captions with a brief explanation, and also explanation of the abbreviations used. 

2- conclusion is nice, but its format needs improvement. delete first sentence, as everyone know that it is a conclusion section. moreover, write in a paragraph format instead of giving number of conclusion. 

3-also add if there is any limitation of the study. 

Author Response

Dear reviewer,

 

Thank you very much for your valuable comments.

 

1- I have improved the captions of the figure and tables (marked up using the

“Track Changes” function, Figure 1-4 and Table 1).

 

2- I have deleted the first sentence and numbers of conclusions.

 

3- At the end of main text (In future research…), we have implied possible limitations of the study and given future directions of related scientific efforts.

 

I’m ready to undertake further revision.

Reviewer 2 Report

The paper can be accepted in the present form since the suggested changes concerning symbiotic peculations have been inserted in the revised text.

Author Response

Dear Reviewer,

 

Thank you very much for your valuable comments, appreciation and great help!

 

Blessing.