Review Reports - Distinct Impact of Drought on Radial Growth at Different Heights and Parts of Populus euphratica in the Oasis at the Hinterland of the Taklimakan Desert

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The study is quite interesting and with a high novelty. I have been working in tree resistance to drought and it is the first time I read a paper dissecting the different parts of a tree in the way is here done. I do not consider the paper as excellent at all, although deserving publication, because I miss some physiological evidences of the "broke its arm" mechanism. I smean some measurements of the water status of the different tree parts. Nevertheless, and in spite of this fact, I find some an interesting new approach here that may be considered for publication.

What I encourage to be improved is the overall quality of the presentation and graphs. The present form lacks quality in a high extend.

Author Response

Dear Sir/Madam,

Thank you so much for your kind encouragement on our manuscript entitled “Distinct impact of drought on radial growth at different heights and parts of Populus euphratica in oasis at the hinterland of the Taklimakan desert” (Forests-2692177) and sending us the review on our manuscript.

We greatly appreciate reviewer for your valuable comments and constructive suggestions. We have carefully addressed these points in our revised manuscript and a point-to-point response to the comments has been detailed in our Cover Letter, in which the comments are written in italics followed by our responses in regular text. In addition, the changes or revision were marked with red text in new version of the manuscript.

Now, we are resubmitting the latest vision of our manuscript to you.

Best wishes,

Anwar Abdureyim

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

The paper represents a study of drought resilience of one widely spread poplar species to drought at the level of individual tree compartments. This is an interesting topic, as usually studies are concentrated on the whole tree behavior. However, the paper needs to be considerably improved. In particular, there are contradicting statements (e.g., if groundwater level is suitable for these trees or not), which may be a simple technical mistakes, but they lead to the wrong understanding of the paper. The mechanistic explanation of the observed data is also weak.

· The physiological activity of apical branches relatively to lateral branches can be explained by the lower photosynthesis of last ones because of shading. This should be mentioned in Introduction and/or Discussion.

· What was trees age?

· Could you detect sapwood depth from your cores?

· ALL Figures must be sharpened.

· Map subfigures at Figure 1 should be also marked by letters and mentioned in the legend. It would be good either to decrease the scale of upper left map i8n order to show the location within the whole China or add one more map with the position of Taklamakan within China. In the legend it must be described, what means colors in the right map.

· Figure 2. X-axis caption is unclear. Do you mean “CUMULATED number of branches”? Per one tree of for all three trees? First order branches or all branches? In any case the final number of 25 does not correspond to any option from Table 1.

· It would be good to mention the time resolution of Palmer index (1 month?) and maybe to explain how it is defined. If mean precipitation is 10 mm and potential evaporation rate 2480 mm, how it can be that ca. half of years had no drought at all (PDSI>-1, Fig.3)?

· Groundwater depth and SWC were mentioned in the Results, but not in Methods.

· On Fig. 5a max. annual precipitation is ~4.5 mm (with mean 2.3 mm, line 268) but on Fig. 5b mean precipitation only in July was 9 mm. How it can be?

· At Fig. 7a min sample size is 1, whereas you measured 3 trees from 2 sides. How it can be? 2 trees in 1961 did not reach yet 1.3m and one core in 3^rd tree was damaged?

· According to Fig. 3 the moisture conditions strongly and continuously improved in the area. So, the decline of growth in the recent years (2010-19) hardly can be explained by drought (what is stated in 4.3), especially taking into account the groundwater is accessible for trees in the area. Maybe the decline of growth can be explained simply by natural aging of trees?

· Concerning the difference in growth of different tree compartments, it makes sense to mention pipe model theory (the recent review of it is, e.g., in Lehnbach et al., 2018, https://academic.oup.com/aob/article/121/5/773/4820933).

· New sapwood growth is compensating the conversion of inner sapwood into non-conductive heartwood, and the apparent diameter growth is a result of these two processes. This can be discussed when analyzing the resulting TRW dynamics

Other comments are in the attachment

Comments for author File: Comments.pdf

Comments on the Quality of English Language

Sometimes the authors used "was" instead of "were". Some contradicting statements can be caused by wrong choice of words (see in the attachment)

Author Response

Dear Sir/Madam,

Now, we are resubmitting the latest vision of our manuscript to you.

Best wishes,

Anwar Abdureyim

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

Abdureyim with co-authors studied the Distinct impact of drought on radial growth at different heights and parts of Populus euphratica in oasis at the hinterland of the Taklimakan desert. The study is relevant, well structured, the used methods are adequate. The obtained results have a scientific value and will be of interest to readers.

However, some minor revision (including text editing, presented figures quality improvement, see attached file with my comments) is required before.

Some places that require attention:

Figure 1. Must be improved. Replace photo with a better image quality.

Figure 2. Change "branchs" to "branches".

Figure 11. In legend, Add information about meanings of different letters on the tops of columns.

Try to improve the presentation quality of all figures.

References. Check if all references formatted according to the Journal requirements.

Best regards

Comments for author File: Comments.pdf

Author Response

Dear Sir/Madam,

Now, we are resubmitting the latest vision of our manuscript to you.

Best wishes,

Anwar Abdureyim

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

Comments and Suggestions for Authors

The authors considerably improved the manuscript. However, some questions remained.

· In the caption of Fig 1(a) it would be good to mention, what mean colors of the map.

· If you drilled soil until water table, did you compare groundwater depth in your sample site and in the permanent well?

· [9] On Fig. 5a max. annual precipitation is ~4.5 mm (with mean 2.3 mm, line 268) but on Fig. 5b mean precipitation only in July was 9 mm. How it can be?

[Response] Thank you for your question. We reconfirmed the relevant data. Figure 5a shows the interannual data for temperature and precipitation. Figure 5b shows the monthly average data for the period 1961-2021.

It remained unclear how annual maximum precipitation can be ~2 times lower then mean precipitation in one month only.

· [7] It would be good to mention the time resolution of Palmer index (1 month?) and maybe to explain how it is defined. If mean precipitation is 10 mm and potential evaporation rate 2480 mm, how it can be that ca. half of years had no drought at all (PDSI>-1, Fig.3)?

[Response] As you suggested, We provide a temporal resolution of 1 month for the PDSI in 2.3.The PDSI is a drought index based on water supply and demand, and is drought when local water supply exceeds demand and wet otherwise. The Kriya River is the only source of water for the oasis, so years of high-water supply and demand (periods of abundance) may result in a PDSI > -1.

So, Palmer Index takes into account river water level or groundwater depth and then its value variation depends mainly on it? You must clarify it.

“…and is drought when local water supply exceeds demand and wet otherwise.” – it is the opposite: “…and is drought when local water demand exceeds supply and wet otherwise.”

Comments on the Quality of English Language

No comments

Author Response

Dear Sir/Madam,

Now, we are resubmitting the latest vision of our manuscript to you.

Best wishes,

Anwar Abdureyim

Comments:

[1] In the caption of Fig 1(a) it would be good to mention, what mean colors of the map.

[Response] Thank you for your comment. We have added the relevant information to the title of Figure 1.

Figure 1. Location of the study sites. (a) Daliyaboyi Oasis, (b) First tree, (c) Second tree, (d) third tree. In Figure 1a, the purple circle is a nearby groundwater level observation well; the red circle is a sampling site; and the light blue horizontal line is the stream channel.

[2] If you drilled soil until water table, did you compare groundwater depth in your sample site and in the permanent well?

[Response] Thank you for your comment.

Soil samples are augered until water comes out (soil is very wet). Soil moisture content refers to data at a certain point in time on a certain day, whereas depth to groundwater data are averaged over several times of the year, so comparisons with soil moisture content are not very meaningful. Soil water content and groundwater depth data are equivalent to background data. They are useful for determining the actual conditions of the moisture environment in Populus euphratica habitats.

[3] On Fig. 5a max. annual precipitation is ~4.5 mm (with mean 2.3 mm, line 268) but on Fig. 5b mean precipitation only in July was 9 mm. How it can be? It remained unclear how annual maximum precipitation can be ~2 times lower then mean precipitation in one month only.

[Response] Thank you for your question. We have given a response to your question.

Precipitation data in Figure 5a average January through December precipitation over the 1961-2021 period; Figure 5b is the multi-year average precipitation for each month of each year 1961-2021. Precipitation in the arid region is concentrated in July, and Figure 5a includes low precipitation in winter and high precipitation in summer, and the number of months with low precipitation is greater than the number of months with high precipitation, thus yielding a small average. Figure 5a is a multi-year monthly average of precipitation, so the month in which precipitation is concentrated in the arid zone (July) shows a relatively high level of precipitation. This is different from the humid zone or the coastal zone.

[4] It would be good to mention the time resolution of Palmer index (1 month?) and maybe to explain how it is defined. If mean precipitation is 10 mm and potential evaporation rate 2480 mm, how it can be that ca. half of years had no drought at all (PDSI>-1, Fig.3)? So, Palmer Index takes into account river water level or groundwater depth and then its value variation depends mainly on it? You must clarify it.

[Response] Thank you for your question. We gave some explanations to your questions.

The Palmer Drought Indicator contains not only the concept of water balance, which takes into account the conditions of precipitation, evaporation, runoff and soil water content, but also water supply and demand, with good spatial and temporal comparability. In desert regions, runoff affects groundwater and soil water content, and has a significant impact on evaporation. This set of relationships ultimately affects the PDSI; however, the most obvious change in desert areas is the change in water vapor supply and demand, which in turn leads to changes in evaporation, soil water content, etc. Thus, the arid zone PDSI further illustrates the relationship between water vapor supply and demand. Therefore, it can be regarded as a key factor influencing vegetation growth. In particular, the effect of drought on the growth of Populus euphratica is more obvious under the condition that the moisture condition can satisfy the normal growth of Populus euphratica.