Disentangling the Interspecific and Intraspecific Variation in Functional Traits of Desert Plant Communities under Different Moisture Gradients

Round 1

Reviewer 1 Report

Overall statement: In this study was investigated plant functional trait variation under different water gradients and its relationship to soil physicochemical factors in the (semi)desert vegetation. This study is valuable because there are few studies to determine the intra- and interspecific proportions of plant traits in such an extreme production site. Therefore, it can be considered as a gap filler. However, the study has several shortcomings. Most of the problems are in the Materials and Methods chapter. This does not show exactly how the sample was taken. The test method and material are not clearly described for this reason, the study becomes unrepeatable and incomparable. In addition, the amount of data collected does not indicate whether they are sufficient for statistical analyses. In the Discussion chapter, there is little actual comparison with other research results. However, the analysis presented suggest that this is a valuable study and useful scientific knowledge can be gained after the corrections.

My main suggestions for improvement are:

Title:

The title needs to be improved because it does not include an examination of the association with abiotic factors and the fact that a comparison of two moisture gradients has been investigated.

Abstract:

In the abstract, the correlations of soil parameters with moisture gradient are overemphasized, and the results of plant properties are underemphasized.  Keywords: Keywords should not be the same as the words in the title, this will improve the number of search results.  

Introduction:

The wording should be more careful in some places such as citations 2, 3, and 26. In citation 26: According to the authors, the connection is not so direct because there is no reaction to what the plant does not recognize.

Soil is not a key environmental factor, but a medium (plants can be grown in aquaculture), some soil properties may be factors. A more relevant example should be found instead of Arabidopsis thaliana.

In the literature (6, 22), the type of vegetation examined must be indicated.

I lack from the literature the effect of inter- and intraspecific competition on plant properties along the moisture gradient. This can be omitted: „explore the environmental adaptation strategies of desert plants, so as to provide a scientific basis for the management and protection of desert plant diversity.”, because it has not been investigated.

 

Materials and Methods:

The chapter needs to be rewrited thoroughly. I suggest a summary table for both soil and vegetation data in the appendix. 2.1.Overview of the experimental area: Instead of the coordinates of the nature conservation area, the coordinates of the sampling transects should be indicated. The sampling points need to be defined more precisely. The list of climatic parameters and soil types is sketchy, we do not get more precise knowledge about abiotic conditions. In particular, the reference to soil types is important as these were sampled. What type of saline soil occurs here? The presentation of plant associations is also very incomplete. The list of main plant genera and species does not show the vegetation. We do not know how the vegetation changes along the transect. “The influence of the flora of Central Asia and Mongolia on the vegetation is obvious” (this sentence is unnecessary). The last sentences of the chapter should be moved to the appropriate place:”The Aqikesu River is located on the east side of the lake area and supplies water to Ebinur Lake (to the beginning of the chapter). The soil water,salt, and nutrient content decrease from the Aqikesu River bank to the Kumtag Desert; this is not the case for the soil pH (to the beginning of the chapter).” .

2.2. Sample collection:

When, how many times, where (coordinates), in what arrangement, contacting and / or non-contacting quadrats were sampled? This description is missing. “We selected a total of 60 quadrats and conducted community investigation; plant trait collection; and soil water, salt, and nutrient sampling in each.” This is not clear, it needs to be clarified.

 

2.2.1.Collection of soil samples:

„We selected  soil sampling points  in the standard quadrat using  the diagonal sampling method and extracted 3 portions of 0-10 cm soil (3 replicates) for each quadrat.” The description of the sampling should be clarified: when, by what means and methods the sample was taken. Did you create an average or individual sample? Why was only the topsoil sampled? It has been written that there may also be buried saline strata. If trees and shrubs were examined, their roots do not collect soil moisture from the top 10cm of the soil! Were soil moisture measurements performed on the site? How? From what depth? What is the relationship between soil sampling and vegetation sampling site? In such a habitat, the soil properties under and between the plants can differ significantly. How was this taken into account? What relationship was expected between the actual moisture content (drying at 115 ° C) and the plant properties? Was the 500g soil sample also taken from the top 10cm?  

2.2.2. Collection of soil samples:

The title of this chapter is incorrect because it refer to the collection of plant samples.  „We investigated and recorded the characteristics of the trees in each 30 × 30 m quadrat. We selected two 5 × 5 m quadrats along the diagonal to investigate shrub characteristics and three 1 × 1 m quadrats on both diagonals of the tree quadrats to investigate herb characteristics.” The description of the sampling is not clear, should be clarified. What considerations were taken into account in the selection of the 5 × 5 m and 1 × 1 m quadrats? What considerations were taken into account in the selection of plant leaves?  To what extent did the measured leaves represent the individual or species in the square? „We dried and crushed the plant leaf samples at 75 °C.” After this, what happened to the plant leaf samples?  The remainder of this chapter deals with the processing of soil samples, which should be transferred to the previous chapter. The description of the measurement methods is schematic, the literature reference is missing. What soil pH was measured and by what means?

 2.2.3.Data processing and analysis:

The creation of the two gradients is not clear. It is unclear, whether the spatial sample order in the field was maintained or not, or groups were formed based only on the currently measured moisture content? Does this mean that a gradient belongs to a category? This needs to be clarified. What does "aquatic and saline environment" mean? How were data of different dimensions (pH; total N) weighted for joint analysis?  

3. Results and Analysis:

 A diagram should be made to prove that these are indeed moisture gradients. What do low and high humidity mean? The whole study is based on this experimental designed for abiotic background, so its existence must be confirmed. The use of the term of moisture gradient should be reconsidered in the manuscript.

 When evaluating Figure 1, it cannot be stated that LW and LT were higher if the difference was not significant.

 It is didactically problematic that the order of the functional properties shown in Figure 1, Table 1, and Table 1 analysis is different. The meaning of a and b should be clarified in the explanation of Table 1.

 It is confusing that plant properties are either abbreviated or listed. Figure 2 is not visible well, its quality needs to be improved. To what extent did the measured leaves represent the individual or species in the quadrat?  Figure 4 has so little information content that it could be omitted. The Discussion chapter is rather an introduction it contains little discussion, it is slightly related to own results. Therefore, this section requires significant rewriting. In particular, chapter 4.1, but the situation is similar in chapter 4.2. (Zhao et al.) and in the case of articles 57, 58, 59, 18.  It should be worded more finely, because the studied soil parameters, such as total nitrogen and phosphorus, represent unavailable nutrient content. In addition, the results include effects of clonality and biotic competition that could not be distinguished.

 The main soil types should be discussed in the Materials and Methods section.

  It should be considered that the importance of abiotic factors may vary and the richness of the flora may also play an important role (in the case of article 53).

Author Response

Dear Editor and Reviewers:

Thank you for your letter and for the reviewers’ comments concerning our manuscript “Interspecific and intraspecific variation in functional traits of desert plant communities based on moisture gradients” (ID: forests-1761033). Those comments are all valuable and very helpful for revising and improving our paper, as well as the important guiding significance to our researches. We have studied comments carefully and have made correction point by point which we hope meet with approval. Revised portion are marked in red in the manuscript.Please see the attachment.

Author Response File: Author Response.docx

Reviewer 2 Report

The manuscript “Interspecific and intraspecific variation in functional traits of desert plant communities based on moisture gradients” deals with the community weighted means (CWM) of plant functional traits, measured under different moisture levels. The intraspecific variability of traits and its influence on CWMs is often ignored, but recently get more attention of ecologists. Therefore, concerning this study, I have some questions to the methods and analysis.

Materials and Methods

“The main plant genera are Poplaraceae, Chenopodiaceae, Tamarixaceae, and Gramineae.” – these are families, not genera. Gramineae should be called Poaceae.

“Halostachyscaspica” – insert space Halostachys caspica

“Nitraria sibirica Pall” – this species is only one, there the author of taxon is shown. You should add the authors to all the species at the first mention or cite the source of Latin names.

“and three 1 × 1 m quadrats on both diagonals of the tree quadrats” – which three quadrats do you mean? Make it clear, as three quadrats were not mentioned before.

“2.2.2. Collection of soil samples” – Collection of plant samples?

“We dried and crushed the plant leaf samples at 75 °C.” – Why did you dry plant samples? After you describe the analysis of soil. May be, soil samples?

“We classified the soil moisture gradients based on the soil moisture measured in the field and in the laboratory, dividing the 60 quadrats into two gradients, high moisture and low moisture,” – Report, what were values of moisture in the two parts of gradient. Did they differ significantly from each other? So, here or in the results I’d like to see more extensive description of moisture gradient. Also, “Soil moisture gradients” – in you study there is only one gradient, but you have separated it in two levels, low and high. So, I think it would be more correct to use “moisture level” instead “moisture gradient” through the text.

CWMs: How did you calculated relative abundance of plant species, based on the measured characteristics? Did you accounted only numbers of individuals, or incorporated plant height and crown width? What does mean abundance for trees? Is it cover or something else, or abundance by Braun-Blanquet?

“redundancy degree analysis (RDA)” – specify, what were response variables, and what were explanation variables.

 

Results

Figure 1: Why in the Y-axis CWMs are in g/kg? They should be in the measured units. I think, you should not put all the pairs of bars on the same diagram.

“between the two water and salt environments” – doesn’t the manuscript deal only with moisture gradient?

Figure 2: Why all soil factors are also in g/kg? pH in not expressed in this units. Also, the values, measured in different units, should not be in the same diagram.

What are arrows in the graphs? Are they standard errors or deviations? Write it in the figure legend. Because, if they are errors, the differences do not seem significant.

“** extremely significant differences” – What does mean “extremely”? Report p value (<0.01 or <0.001).

“the intraspecific variation in plant functional traits was more substantial under low moisture and high moisture conditions” – unclear, under what conditions it was higher.

Table 1. Add the replication number to the capture. If I understood from the methods, “interspecific variation” means CWMf, and “intraspecific variation” means CWMi (=CWM–CWMf). In this case, you should add measurement units to the row names.

 

Figure 4. Is it possible to make sizes of circles proportional to their variation?

In the results or discussion I also recommend to add some descriptions of vegetation to make clear to the reader, how moisture gradients are different in dominant species abundance, how do dominant species differ in their traits, and which species contribute more into intraspecific variability. Also, in some traits, intraspecific variability do not always follows interspecific variability.

Comments for author File: Comments.docx

Author Response

Dear Editor and Reviewers:

Thank you for your letter and for the reviewers’ comments concerning our manuscript “Interspecific and intraspecific variation in functional traits of desert plant communities based on moisture gradients” (ID: forests-1761033). Those comments are all valuable and very helpful for revising and improving our paper, as well as the important guiding significance to our researches. We have studied comments carefully and have made correction point by point which we hope meet with approval. Revised portion are marked in red in the manuscript.Please see the attachment.

Author Response File: Author Response.docx

Reviewer 3 Report

Comments for the Author:

 

Review on” Interspecific and intraspecific variation in functional traits of desert plant communities based on moisture gradients” provide us with results of inter- and intraspecific variation in plant functional traits on desert plant communities. Generally, I think that the topic of the paper is very interesting and brings new original data for this topic.  I recommend a major revision.

 

 

Further comments:

 

Keywords:

Delete keywords that are already in the title. It's a duplication.

 

Methods:

At the subtitle “Overview of experimental area“ I miss the picture of the area and marked sampling belt and sampling point.

Subtitle 2.2.1 and 2.2.2 are the same.

Subtitle 2.2.2 please write in more scientific way. Most of the sentences author start with we. Write the facts in the order of data processing. The same it is with subtitle 2.2.3

 

In subtitle 2.2.3 in sentence “…we calculated the community functional traits..” What it is and how you calculated Community functional trait? In this chapter author sometimes write CWM, than CWM_F than CWM_I   - it is not clear explant how you get this indexes and what they mean.

 

In general: Before I do not get all of this information, I cannot clear read superfluous chapters. Furthermore in abstract and conclusion author write about plant functional traits and nothing about CWM indexes.  

 

Figure:

Figure 1: Missing what the abbreviations on the x-axis mean. In y-axes it will be more transparent if it is written only CWM.

Author Response

Dear  Reviewer:

Thank you for your letter and for the reviewers’ comments concerning our manuscript “Interspecific and intraspecific variation in functional traits of desert plant communities based on moisture gradients” (ID: forests-1761033). Those comments are all valuable and very helpful for revising and improving our paper, as well as the important guiding significance to our researches. We have studied comments carefully and have made correction point by point which we hope meet with approval. Revised portion are marked in red in the manuscript.Please see the attachment.

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

 

Revision of the corrected article

You can see that the manuscript has improved, but I think there is still a lot of room for improvement. However, several of the problems complained of have not been corrected by the authors.

The data reported in the manuscript were analyzed based on two moisture gradient categories, so I asked for proof of moisture gradients. In the improved Materials and methods section, in the table 2 the two mean and standard deviation data do not prove the presence of a moisture gradient. This is not shown in Figure 3 either.

It also turned out that several months elapsed between the moisture measurements: „During the peak period of plant growth from June to August 2018, within the determined standard quadrat”.

The measured actual soil moisture content can change significantly during this time. Thus, these measurement results cannot be compared. However, the moisture gradient category was determined on this basis. It remains unclear how the two current soil moisture measurement methods (field and laboratory) were used in combination to determine the two “moisture gradient categories”.

This needs to be clarified because until then we cannot be sure that the two soil moisture groups were properly formed.

My suggestion is as follows: Classify the soil moisture data along the transect according to their location. So you will get a group closer and farther to the river. It can be assumed that the groundwater and humidity decrease as you move away from the river, if this is supported by the topography and the soil. This may reduce the error due to the time lag of the current moisture measurement, so the formation of the two groups may be more justified.

Several of the criticized problems in the review were not addressed by the authors (these were not corrected or answered or were not justified).

e.g: 1. Soil is not a key environmental factor; 2. I suggest a summary table for both soil and vegetation data in the appendix. 3. We do not know how the vegetation changes along the transect. 4. In the literature (6, 22), the type of vegetation examined must be indicated. 5. „We selected a total of 60 quadrats and conducted community investigation; plant trait collection; and soil water, salt, and nutrient sampling in each. „ This is not clear, it needs to be clarified. What do you mean by that?: „conducted community investigation”; Such study was not performed. Do you mean other types of tests? 6. „What relationship was expected between the actual moisture content (drying at 115 ° C) and the plant properties?” This method measures total water content, but only part of it can be absorbed by plants. 7. What type soil pH was measured and by what means? (there are several methods; What is the type of instrument?) 8. How were data of different dimensions (pH; total N) weighted for joint analysis? 

Such a presentation of vegetation is still inadequate: „A variety of habitat types in the study area gave birth to a wealth of desert plant community types. There are rich salt-tolerant and drought-tolerant plants, as well as sandy, mesophyte, hygrophyte and aquatic plants. There are more woody plants and herbaceous plants.”

Why not present at least one vegetation profile with the soils below? It would make sense to list soil types in parallel with the transect.

The full length of the transect (3600m) is shown in the figure but omitted from the text. Please include in the article the specification of the soil test measurements, it's not enough to just answer. We still do not know by what means the soil sample was taken.

The next part should be formed into a discussion, I referred to this in the previous review:

„Lichstein and Berg et al. argued that intraspecific trait variation considerably impacts community structure factors such as species relative fitness, niche breadth, and competition intensity [45-47]. Changes to leaf-related traits (leaf length, leaf width, leaf area, etc.) reflect the nutrient-use strategies of plants adapting to changes in soil factors; these traits can elucidate the growth strategies and resource-use abilities of plants. Surya K. Maharjan and others have shown that plants can save water by limiting cell division and growth to reduce leaf length, leaf area, and specific leaf area, thus minimizing transpiration in the area of soil moisture deficiency [48]. Reich P.B. also proved that plants with lower leaf area ratios can more effectively adapt to resource-poor and arid environments [49].”

„The variation in plant functional traits, i.e., changes to a plant’s appearance and internal structure, is an adaptation response of plants to their environment [51”

It was not a request to add more to the discussion, but to compare your own results with other literature!

For example, this section is still not related to your own results:

„Zhao et al. found that soil factors explained 18.4% and 40.7% of inter- and intraspecific variations, respectively, when studying leaf morphology and chemical traits in a mountainous broad-leaved forest in Sichuan [53]. Soil organic carbon and total nitrogen had the most considerable influence on the interspecific and intraspecific variations of community-level specific leaf area, and soil pH and total nitrogen most strongly affected the inter- and intraspecific variation in plant functional traits under different water gradients. For example, under high water content, the intraspecific variation in plant height (r = 0.42), leaf length (r = 0.37), and leaf width (r = 0.55) significantly positively correlated with soil total nitrogen.”

Author Response

Dear Reviewer:

Thank you for your letter and for the reviewers’ comments concerning our manuscript “Disentangling the Interspecific and intraspecific variation in functional traits of desert plant communities under different moisture gradients” (ID: forests-1761033). Those comments are all valuable and very helpful for revising and improving our paper, as well as the important guiding significance to our researches. We have studied comments carefully and have made correction point by point which we hope meet with approval. Revised portion are marked in red in the manuscript. Please see the attachment.

Author Response File: Author Response.docx

Reviewer 2 Report

There are few comments for the authors.

2.2.3.

«and three 1 × 1 m quadrats on both diagonals of the tree quadrats to investigate herb characteristics.» – How were three quadrats were located along two diagonals? Were it in total 6 quadrats?

 

2.3.1.

“According to the field and indoor measured soil moisture, the 60 quadrats into two gradients,” – we separated the 60 quadrats…

Table 2: Number of plots in the capture. Also the minimum and maximum values should likely be shown.

 

4.1.

“The variability of herbaceous plants is greater than that of woody plants and community level.” – at community level?

“There is a common phenomenon in this study area : Haloxylon ammodendron grows well in the area with high soil water content, and its important value in the community is high,” – Latin should be italic. Importance value?

«that intraspecific variation contributed more to intraspecific variation” – to interspecific variation?

Author Response

Dear Reviewer:

Thank you for your letter and for the reviewers’ comments concerning our manuscript “Disentangling the Interspecific and intraspecific variation in functional traits of desert plant communities under different moisture gradients” (ID: forests-1761033). Those comments are all valuable and very helpful for revising and improving our paper, as well as the important guiding significance to our researches. We have studied comments carefully and have made correction point by point which we hope meet with approval. Revised portion are marked in red in the manuscript. Please see the attachment.

Author Response File: Author Response.docx