Comprehensive Evaluation of Ecological Functional Traits and Screening of Key Indicators of Leymus chinensis Germplasm Resources from Northern China and Mongolia
Jerry Volesky
Round 1
Reviewer 1 Report
Dear Authors,
I really apreciate all your research work, as well as the way you managed to present your findings.
As I recommended, the paper can be published after minor corrections, such as:
1. Mention that LC is the abbreviation for Leymus chinensis.
2. „The concentration of CO2 in the 43 atmosphere will reach 417.2 ppm in 2022” (lines 43-44) - but the article is going to be published in 2023.
3. Please explain SSP - line 48.
4. Mention the measurement units for the analyzed indexes, at least in „Materials and Methods”.
5. Formulas 9-11 (lines 353-358) are written different than the others - please use the same style.
6. Also, I consider that the Abstract, Results and Conclusions can be improved with minimum effort - some concrete findings in Abstract and Conclusions and 1-2 additional graphs in Results.
As I said, the manuscript shows hard work and perseverence, so you have all my support for publishing the paper.
Best regards and good luck!
Author Response
Please see the attachment.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
Dear Authors,
General comments
This manuscript describes the need of identifying Leymus chinensis germplasm materials that are better suited to enhance ecological functional traits in grasslands. For that, 42 germplasm materials from Northern China and Mongolia were evaluated with particular interest of the multi-dimensional indexes of drought tolerance, rhizosphere expansion and soil improving ability. Considering the importance of this grass species in Eurasia, this seems to be a particularly relevant topic.
The materials and methods section missed information about how the experimental design was conducted and therefore, I feel unable to further evaluate this manuscript. In this regard, there are two indexes used in the manuscript that I was unable to retrieve, these are the drought tolerance from Li Y. 2019.04. and rhizome expansion from Li X. 2021.06. Since these two indexes are key to your manuscript and it seems that your study might have be based on the results of the two master thesis you cited, I suggest you to consider inviting Li Y. and Li X. to participate in this manuscript and as needed, further develop the materials and methods section.
The results presented about the principal component analysis may need revision and more details (see specific comments below). For example, there is no interpretation of the meaning of each principal component, which is usually one of the most important information obtained in such analysis. Such interpretation might be added to the discussion, however, the results section needs to highlight these findings. Similarly, there is no interpretation of what each cluster means. Furthermore, in the comprehensive evaluation for all traits, and for each of the individual multi-dimensional indexes, it is unclear why a larger comprehensive score is necessarily a better germplasm material. It does not seems correct assuming that the increase of any given trait would mean an improvement in all three indexes, on the contrary, some traits might represent a trade-off, for example, larger leaf size and number might be a disadvantage for the water use efficiency of the plant and therefore lead to a less drought tolerance material. This seems to be incorrect and otherwise, it needs to be clearly explained and justified.
The manuscript discussed very few of all the results presented and rather than compare your results with previous findings, it lists findings from other works lacking a more scientific discussion. I suggest to further develop this section. All in all, without the M&M details, the interpretation of results and a more comprehensive discussion, the reached conclusions can be questioned.
M&M.
Unfortunately, it is not explicitly said what you have done to evaluate these germplasm materials. Section 2.1 describes the origin of the plant material. However, there is no place explaining how measurements were conducted: did you plant all 42 materials in pots or was it a field experiment? When and where was conducted the planting? How many plants were planted and how many were measured per each material? How many repetitions were done? What methodology was followed to perform the measurements? Did you measured all materials in the same location and year? Etc., etc.
Right after the ‘2.1 Experimental materials’ you need to have a section that provides all details mentioned above please. Then, I suggest you to move onto listing (i) the traits measured (section 2.2) specifying the methodology used to do so, (ii) the three indexes calculated, drought resistance, rhizosphere expansion ability and soil improving ability, and then, describe the statistical analyses with respective references.
Please, note that your current section 2.3 Research method should be revised or removed from its place because as it is, it only describes how the multi-dimensional indexes where calculated but do not describe how the comprehensive evaluation was done. So I recommend to create sections 2.2.4 and 2.2.5 for these respective indexes and to add the actual equations. In this section, it seems relevant to explain (and provide the corresponding references) the research method applied to carry out the ‘comprehensive evaluation’.
You claimed measuring ‘soil improving ability’ of the different germplasm materials, but there is no reference on how this was actually evaluated. Instead, you have section 2.2.3 that lists a number of properties related to soil fertility but this does not necessarily mean a soil improvement in itself (this probably would be better understood if you explain the conditions in which plants were grown). Also, it is unclear over which period of time the soil improvement was assessed. Furthermore, it is no clear how you compared the ability of improving soil among different germplasm materials, as measuring the nitrogen, phosphorous and potassium content and availability in itself does not really give a fair comparison of comparing how one specific germplasm material improve the soil condition. I think this will be clarified once you better describe how was the experimental design and the conditions of measurements. Finally, I wonder whether or no you calculated a soil improving index and if no, why not considering the other two multi-dimensional indexes.
Specific comments
Title: I suggest to specify that plant resources where collected in northern China and Mongolia. Please, consider the edit the title to: Comprehensive evaluation of ecological functional traits and screening of key indicators of Leymus chinensis germplasm resources from Northern China and Mongolia.
Keywords: Please, avoid repeating words that were already included in the title. I recommend deleting Leymus chinensis, ecological function and comprehensive evaluation. Instead, you may consider to add: drought tolerance, rhizome space expansion (or rhizosphere expansion) and, soil improvement ability.
Abstract:
Ln20-22. Please, consider revising either of these sentences because the first sentence refers to longitude and latitude, while the second sentence refers to longitude and altitude. Thus, it isn’t clear the correlation between latitude and altitude. “There is a significant positive correlation between the F value and longitude, while the F value is significantly negatively correlated with latitude. Therefore, L. chinensis germplasm from high longitude and low altitude may exhibit (or exhibited) better comprehensive performance.”
Introduction
Ln30. Please revise this sentence to either “The world’s grassland biome…’ or “The world’s grasslands…”.
Ln32-34. Please, revise this sentence, I think the degradation observed using remote sensing technology should be referred to the 21st Century (from 2000 onward) as per your citations instead of the 20th Century (1900 onward).
Ln44. Please, use either ‘has reached…’ or ‘ was estimated to reach…’ as appropriate.
Ln43-45. Please, use one single sentence. “The concentration of CO2 in the atmosphere is estimated to reach 417.2 ppm in 2022, which is more than 50% higher than before industrialization (about 278 ppm) [13] and, it is expected to double by 2050 [14,15].”
Ln64-65. I suggest to delete this sentence. Otherwise, you need to specify what was more serious than what. For example, “This phenomenon shows that the problem of grassland degradation in China has become more serious in recent years compared to previous assessment.”. But still does not make sense and you need to provide a reference.
Ln69-72. Please, provide a few more reference to support this statement that refers to “Chinese scholars” meaning several authors while the reference provided is only focused in the Gansu province.
Ln84. Please, consider adding the author’s name of the species “Leymus chinensis (Trin.) Tzvelev” and at least a common name such as ‘Sheepgrass’.
Please, consider to include the book (https://link.springer.com/book/10.1007/978-981-13-8633-6) as it seems to be a comprehensive description of Leymus chinensis research in China and the world. Chapter 2 of the book seems to be particularly important regarding germplasm diversity and might be a good source for you to compare the new insights presented in your manuscript with previous work.
Ln98. Please, revise this sentence as ‘special weapon’ does not seem to be appropriate. You may use ‘L. chinensis uses its horizontal rhizomes...to farther explore the soil and reach water and nutrient sources [REFERENCE?].
Materials and Methods
Ln121. Please, add ‘different regions in Northern China and Mongolia (Fig. 1).’ and delete the sentence Ln122-123 as it seems to be out of place here.
Ln124-125. Please, replace ‘species’ with ‘germplasm materials’. I believe you studied several germplasm materials (also known as accessions) of Leymus chinensis. If you included any other species, you need to state so.
Ln133-136. Are all these traits indicators of drought tolerance? If so, please do state that in your sentence. However, I am not sure about this, these characteristics seems to be plant functional traits that some might be related to drought tolerance, productivity and plant growth strategy. You need to justify this and provide the corresponding reference.
Ln138. Please, revise this sentence and consider the following correction. ‘According to the results presented by Bai [47], the principal component 1 was comprised by the following traits: the extended area (EA), extended distance (ED), accumulated extended distance (AED), number of rhizome extension directions (NED), and maximum one-direction extended distance (MED). This axis with the largest [ecological functional trait variation?] represented...[add the interpretation of the axis resulting from Bai’s analysis]. Therefore, we used these traits as indicators to represent the spatial expansion ability of L. chinensis.’
Ln144-147. Please, add reference or explain why you selected these indexes. Hay yield seems out of place within the ‘soil improvement’ traits.
Ln149-154. Please, provide an accessible link to reference [46] and [48].
Results
Ln171-174. It seems that the drought resistance index and the rhizome expansion index were not used in the principal component analysis but the traits that are used to calculate them. If so, please, revise this sentence because it suggest that these two indexes were included in the analysis.
Ln178. As you do not really point out any relevant information of Table 2 but just mentioned what the traits’ loadings were and what the percentage contribution of variation was for each principal component, I suggest you to place table 2 in supplementary materials. Thus, Fig. 1 will be your first and most relevant result presented. Alternatively, you could leave this table in the main manuscript and highlight the most important traits (for example using bold numbers for the highest scores) in each principal component. Then, you can refer your results to this table. When presenting the results of principal components, you need to consider both, the loading values and the direction representing the trait, so that you account for possible correlations and trade-offs between traits. That is why, the diagram of Fig. 1 can be better describing the PCA results than Table 2.
Ln194-196. These two sentences seem to be only partially correct and need to be revised. For example, for PC1, there are two groups of traits that have the highest contributions, these are ED, AID, NED, EA and MED and, OM, AN and TN, which are all fairly correlated in this axis towards the positive site of it. Furthermore, MDA, with a much lower contribution, is fully aligned with this PC1 axis. On the other hand, for PC2, the largest contributions are from RFW, OM, AP, AN and TN towards the positive end and from MED, EA, ED AED, NED and LN towards the negative end. Thus, OM, TN AN on the one hand and NED, AED, ED, EA and MED on the other, are all traits that contributed importantly to the variation explained by PC1 and PC2.
Ln196-198. I suggest to include a figure of the two-dimensional coordinates for PC3 and PC4.
Section 3.1.2. It is unclear why the higher F number necessarily means a better comprehensive evaluation of ecological functional traits (Ln241-242). This statement needs to be justified. From my understanding, the increase on any given traits does not meant that it will be better from an ecological functional viewpoint. For example, larger number of leaves, of larger size and with higher photosynthetic capacity might allow more productive plants, but may be a disadvantage for plants dealing with drought stress and/or under intensive and frequent grazing. Since this has not be justified or explained in M&M, the ranking of L. chinensis materials based on the F values seems to be arbitrary to me.
Ln258-265. I suggest adding a diagram of the clusters only in the two-dimensional coordinates for PC1 and PC2, similar to Fig.1 but without the variables. And you also need to comment on the difference between clusters. From Fig. 1, one can depict that there is a lot of overlapping between clusters. For example, cluster 2 enclosed the other three clusters, and there seems to be almost full overlap between cluster 1 and 3. This needs to be pointed out in your results and further discussed later in the discussion section.
Ln291-295. I think it is important to mention that SPAD could be dismissed from the regression model as you would still obtain 0.94 accuracy. Moreover, disregarding SPAD and MDA from the model would yield a relatively high predicting accuracy (0.90) and simplify the model significantly.
Ln298-301. These sentences seems to be part of the discussion and not a result.
Section 3.4.1. Did you performed another PCA for the traits related to rhizome space expansion? I wonder why not. This seems to be missing in this section.
Tables 3, 8, 9, 11. I do not see much value in presenting in the manuscript the principal component factor scores for each principal component, but rather to present the comprehensive score and the corresponding ranking. I suggest to merge all these tables in one single table that lists the 42 germplasm materials, and provides the comprehensive scores and its associated rankings for all ecological functional traits (Table 3) and multi-dimensional indexes (i.e., drought resistance [Table 8], rhizosphere expansion [Table 9] and soil improvement ability [Table 11]). Then, you should move the complete tables to supplementary material. Another reason to do such condensed table is that it will be easier to visualize the ranking of each germplasm material for all 4 ‘indexes’ together.
Dear authors,
the quality of the English is very good from my understanding.
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Reviewer 3 Report
Review of the manuscript Agronomy-2423653
The development of biogeocenotic principles and methods of ecological restoration of degraded pasture ecosystems is an important task of biological and agricultural sciences.
Despite the relevance and importance of the problem under study, I have a number of comments and recommendations for the manuscript.
1. For what period of studies are the data presented?
2. The methodological part of the manuscript is not properly presented. The authors listed a large number of parameters that they had studied, but the authors did not provide a brief methodology for determining them. This Section needs to be supplemented.
3. There are a lot of huge Tables in the "Results" section, this makes it difficult to read the text. I propose to place some of these Tables in Supplementary Materials.
4. I think Sections 3.1.1.; 3.1.2. and 3.3. should be merged. From the first two Sections, it is not clear what main parameters of L. chinensis were selected by the authors for breeding when selecting genotypes. What is the probability that eight indicators of PH, LN, NT, SPAD, MDA, SDW, MED and OM can be concentrated in 1 genotype? Sections 3.4.1. and 3.4.2. should be combined.
5. Lines 181-188 duplicate the information provided in Section 2. Materials and Methods.
6. Most of Section 4.1. contains well-known information. This Section should be edited. The authors should add information about the results of a comprehensive assessment to identify selective traits for the culture under study.
7. Lines 432-439 duplicate information from the "Results" section. Authors should improve Section 4.2. «Relationship between geographical factors of original habitat and comprehensive evaluation of ecological functional»
8. Section 4.3. Why did not the authors present the results of other scientific reports on «Screening of key indicators for comprehensive evaluation of ecological functional traits of L. chinensis germplasm» and did not compare them with their research results?
9. Section 5. Conclusions. Lines 474-475. The correlation coefficient of 0.326 and -0.434 is a weak correlation of features. Many researchers do not use such values to interpret the data and do not take such values into account. This Section should be refined.
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Reviewer 4 Report
This study evaluated 42 L. chinensis germplasms collected from different regions.
Line 59 -62 Sentence is choppy and needs rewording.
Line 64 – 65 Is phenomenon the correct word in this sentence?
The data analysis procedures of using PCA of various plant characteristics and indexes is appropriate for this type of work.
Other than the locations of the different germplasms evaluated, some details are lacking with respect to the local conditions, plant selection, soils, or growing conditions.
The analysis procedures did successfully identify 4 germplasms that have good potential in new breeding programs.
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Round 2
Reviewer 3 Report
Thanks to the authors for the answers to my questions. The authors have significantly improved the manuscript, taking into account my comments. I think that the manuscript can be accepted for publication by the publisher