Coupled Relationship between Soil Physicochemical Properties and Plant Diversity in the Process of Vegetation Restoration

Round 1

Reviewer 1 Report

The article should be revised by authors. The stated research aim is important and relevant; and the experimental design is adequately made to answer the stated questions. However, the description of results could be improved (please consider language check).

The methods section is lacking the explanation why was these two years were chosen.

line 13-15, different communities - different properties (sounds as an obvious fast, should be paraphased)

line 26-27 - word "important" was used twice, please paraphrase

line 30 "restore via litter decomposition" also should be paraphrased, because the microbial community does the decomposition, while plants provide the litter metarial

Line 40, reference 15 - please explain in more detail

line 49-50 reference is necessary

line 54-62 good points for the supporting the study aim

line 91, figure 1. please add a scale on the figure (coordinates are not very convenient) 

Line 105 please explain what is DBH

Line 113 no formula or definition for H and J indices

Line 145-148 the word "different" is used too much, please paraphrase. This is a common problem throughout the manuscript

Line 149-150 "while shrubs" - what was meant? maybe it should be the index for shrubs, but not shrubs?

Figure 3 please remove the lines between columns, in this design it's unclear if it is a soil profile or different plots

Line 195, 201 in my opinion, the term "soil fertility" is misused here, because it's not equal to the soil nutrient content.

line 214 how can be explained the NH4N outlier in RSL upper horizon?

Figure 5 takes three pages. I would recommend to split it to several figures with titles on every page

line 224-225 - seems that soil desertification is equal to the increase of sand content. That's not true

Line 281 the decrease of soil nutrients with depth is quite commonly observed, maybe here should be added more references

Line 333 is this reference mentioned in the literature list? 

line 334 "P generally restricts" it is not correct, will be better "P is a limiting factor of"
 Line 345-347 the sentence is unclear

line 355 maybe it's plant community diversity effect on SOM, not SOM on diversity?

Line 372 here should be "soil nutrient content"

Author Response

1. The article should be revised by authors. The stated research aim is important and relevant; and the experimental design is adequately made to answer the stated questions. However, the description of results could be improved (please consider language check).

Response: We appologize for the poor language in our manuscript, and we have repeatedly revised sentences and chapters to improve their readability. We have made improvements to the narrative in the results section, and the language of this manuscript was modified by an English editing service—American Journal Experts. We sincerely hope that there will be a substantial improvement in the language level

2. The methods section is lacking the explanation why was these two years were chosen.

Response: We set up a fixed sample plot in the Huoditang forest area in 2013, and conducted resource surveys and soil measurements every five years thereafter. In 2018, it was postponed to 2019 due to some force majeure. Therefore, we choose these two years.

3. Line 13-15, different communities - different properties (sounds as an obvious fast, should be paraphased).

Response: We have modified this sentence. Changed the original sentence “The analysis found that the species diversity and soil physicochemical properties were different among different forest communities” to “we determined that the correlations between plant diversity and soil physicochemical properties were discrete”.

4. Line 26-27 - word “important” was used twice, please paraphrase.

Response: We have modified this sentence. Changed the original sentence “soil properties, as important indicators, play an important role in the performance of soil functions” to “soil properties are important indicators that play key roles in the performance of soil functions”.

5. Line 30 "restore via litter decomposition" also should be paraphrased, because the microbial community does the decomposition, while plants provide the litter metarial

Response: We have revised this statement. Changed the original sentence “Plants can improve soil physicochemical properties and restore soil fertility through root activity and litter decomposition” to “Plants can improve soil physicochemical properties and restore soil fertility through root activity and provides the litter metarial for microbial decomposition”.

4. Line 40, reference 15 - please explain in more detail.

Response: We have revised this statement. Changed the original sentence “soil acidity and alkalinity affect plant diversity by affecting enzyme activity and then affect nutrient absorption by the root system” to “soil acidity and alkalinity affect plant diversity by changing soil enzyme activities and root nutrient absorption”.

5. Line 49-50 reference is necessary

Response: We have revised this statement. Changed the original sentence “The influential mechanism of soil factors is complex and easily disturbed by other environmental factors, and the existing studies lack consistent regularity” to “The influential mechanism of soil factors is complex, there are still many gaps in our knowledge about them”, and cited references here:

Wu, H.; Xiang, W.; Ouyang, S.; Forrester, D.I.; Zhou, B.; Chen, L. et al. Linkage between tree species richness and soil microbial diversity improves phosphorus bioavailability. Functional Ecology, 2019, 33, 1549–1560.

Lü, X.T.; Hu, Y.Y.; Wolf, A.A.; Han, X.G.; Le Bagousse‐Pinguet, Y. Species richness mediates within‐species nutrient resorption: Implications for the biodiversity–productivity relationship. Journal of Ecology, 2019, 107, 2346–2352.

6. Line 91, figure 1. please add a scale on the figure (coordinates are not very convenient).

Response: We added a scale on the Figure 1 to make it easier to read.

7. Line 105 please explain what is DBH.

Response: We explained DBH - DBH is the diameter of a tree 1.3 meters above the ground.

8. Line 113 no formula or definition for H and J indices.

Response: We are very sorry for this mistake and added the formulas for H and J.

9. Line 145-148 the word “different” is used too much, please paraphrase. This is a common problem throughout the manuscript.

Response: We have revised this statement and replaced it with other synonyms in the manuscript.

10. Line 149-150 “while shrubs” - what was meant? maybe it should be the index for shrubs, but not shrubs?

Response: We have modified this sentence. Changed the original sentence “Pielou index was significantly different in the three forest layers (p < 0.05), while shrubs were higher than trees and herbs in general” to “the richness index and the Pielou index of the other five forests was generally higher for shrubs than for trees and herbs”.

11. Figure 3 please remove the lines between columns, in this design it's unclear if it is a soil profile or different plots.

Response: We have made adjustments to the figure to make it more accurate.

12. Line 195, 201 in my opinion, the term “soil fertility” is misused here, because it's not equal to the soil nutrient content.

Response: We have modified this sentence. We changed the term “soil fertility” to “soil nutrient content”.

13. line 214 how can be explained the NH₄-N outlier in RSL upper horizon?

Response: This is the result of a combination of factors. First of all, the pH of the RCL community increased significantly from 2013 to 2019, which greatly contributed to the accumulation of NH₄-N in the soil. In addition, this may be related to the characteristics of the tree species. RCL is a broad-leaved tree species with high litter and high N content, which makes the NH₄-N content of the community soil accumulate. In addition, there may be interference from human activities.

14. Figure 5 takes three pages. I would recommend to split it to several figures with titles on every page.

Response: Your suggestion is very helpful. We split these figures into three parts with titles on every page.

15. line 224-225 - seems that soil desertification is equal to the increase of sand content. That's not true.

Response: We removed this sentence.

16. Line 281 the decrease of soil nutrients with depth is quite commonly observed, maybe here should be added more references

Response: We added references in this section.

Danise, T.; Innangi, M.; Curcio, E.; Fioretto, A. Covariation between Plant Biodiversity and Soil Systems in a European Beech Forest and a Black Pine Plantation: The Case of Mount Faito, (Campania, Southern Italy). Journal of Forestry Research, 2021, 33, 239–52.

17. Line 333 is this reference mentioned in the literature list?

Response: We cite here reference number 21 in the literature list and have been noted in the manuscript.

18. line 334 “P generally restricts” it is not correct, will be better “P is a limiting factor of”.

Response: We have modified this sentence. Changed the sentence “P generally restricts plant growth” to “P is usually considered a limiting factor of plant growth”.

19. Line 345-347 the sentence is unclear.

Response: We have deleted this statement.

20. line 355 maybe it's plant community diversity effect on SOM, not SOM on diversity?

Response: We change the statement here into “SOM was positively correlated with tree diversity”.

21. Line 372 here should be "soil nutrient content"

Response: We have modified this sentence. Changed the “soil nutrient” to “soil nutrient content”.

Thank you very much again for reviewing our manuscript and providing us with valuable suggestions and comments.

 

Reviewer 2 Report

General overview:

This paper developed a method to evaluate the redundancy analysis of soil physicochemical properties and diversity indexes of tree, shrub, and herb in retrieving soil physicochemical properties and four diversity indices. After a careful reading of the manuscript, I think this paper is well organized and written.

 

Constructive feedback on the Materials and Methods section:

The authors of the manuscript entitled "Coupled Relationship Between Soil Physicochemical Properties and Plant Diversity in Different Forest Communities" aim at evaluating the stepwise regression analysis for stepwise regression analysis. In general, the manuscript recorded a large spacious scale but more than three years of datasets are necessary to assess the efficiency of site selection and plant investigation for six forest communities.

The aim and method of this study are clear, but the new scientific points should be highlighted. In this study, there are no new methods of vegetation survey proposed by the authors. In what ways do you distinguish this study from others? Physicochemical properties of the soil layers were found to be correlated with plant diversity among forest communities. Have you checked the normality of species? Can you discern the differences in overall species diversity among forest communities? Would it be possible to distinguish it by using the non-normal distribution identification method?

 

Minor comments:

I have some concerns about this work. A significant amount of work needs to be done on the Abstract section. A lack of clarity exists in regards to the study's presentation and purpose or objectives. Please shorten and rephrase some paragraphs so that it's appropriate for the introduction. In addition, I would like to know more about how the species diversity index is applied. The Introduction section is unclear. Supported on the title there is no clear discussion associated with the decomposition of litter, plant absorption, and other factors. The manuscript presents the results from a study oriented to determine the physiological responses for example total microbial and fungal biomass, and rhizosphere microbial community structure. There is little information about soil functional forest community structure provided in the narrative of the study area. Several descriptions of how dominant species are being lost in the study area are missing from your narrative. Linkages between forest diversity and soil properties are relevant to interpreting the potential abstraction of the study areas. It would be helpful to include a map of all the study areas.

Some specific issues/suggestions:

The authors mention the field data collection was completed for some years. It’s suggested to identify the initial and final sampling dates for the RDA. Do the soil samples get collected automatically or are they grabbed? Why were the samples collected randomly; after or during precipitation events? Please clarify. How many samples were obtained per site? What is the size of the samplers (e.g. 1 dm3 or 1l)? Samples were immediately analyzed or some preservation was done before lab analyses were performed? Where were samples collected along with each forest community? Where the samples collected always at the same range of hours? Otherwise, how do the authors manage or evaluate the effects of sampling at different times during a day when evaluating soil properties (e.g. effect of temperature if collected in the afternoon in summer vs morning in another season; enzyme activity is different throughout seasons)?

 

Major Comments:

 

1. To determine the taxa, the authors used the RDA method. In the presentation of the results, it was assumed and corroborated that a high variance was found at soil layers. At least 70 percent of the variance should be explained by all axes. You may find that your multivariate analysis is not robust if you have small factors explaining plant diversity in the shrub layer. This needs to be better explained by the authors. What accounts for the low explained variance? The variance should be even higher than 80% to show strong linkage. It's a standard practice in many publications. Would you please give me an argument why it is necessary to maintain this data if you disagree?

2. A significant portion of the narrative is devoted to describing the physicochemical properties of soils. Authors are asked to reduce the number of details in their results section or summarize all the results in a table since the outcome is not described sufficiently in this section. The statistical analysis should include a statement as to whether the distribution of data is normal or not. It can be added late in the materials and methods section.

3. As the regression is introduced, it is reiterative of the invitation to elaborate on these results in the Methods section. Apparently, the descriptions are mixed with the calculated and normalized, possibly due to improper listing of the figures. Knowing the actual orientation of the manuscript, it lacks a cohesive description that will lead the reader into the identification of the problem and justification of the study. The proposed model is good enough to be used in other related studies. Unfortunately, the paper failed to tell us what the knowledge gap was or which scientific question they were tracking. Other than question-driven, this paper is more application-oriented. Therefore, I suggest revising the paper to make it more scientific.

4. It appears there is some confusion regarding the paragraph segment between lines dynamic changes in soil nutrients in different forest communities. There seems to be some confusion concerning the paragraph segment between lines dynamic changes in soil nutrients in forest communities. The reviewer wants to specify only as much as appears in the manuscript, but in a cited statement, the relationship of forest diversity, ecological role, and potential technological applications to environmental conditions is needed. Using your data, can we predict the permeability of soil air, water, and root growth resistance?

5. While the Discussion chapter is rich in information, it does not present the various results in an order that makes sense, nor does it give a proper sense of how to relate the estimation of global trends in broad-leaved tree species and degradation of vegetated ecosystems and ecosystem service. There is no obvious sequence in the narrative from previous statements. Authors should ensure that will construct a vulnerability in vegetation to physicochemical sorption and nutrient availability. Otherwise, soil nutrient content is misunderstood as an indicator of regional-scale ecosystem response to biomass and an indicator of the productivity of forest communities.

 

Summary of the paper:

A key aspect of this paper is that it provides evidence for implications for the management of degraded forest ecosystems. Thus, a large focus of your paper should be a description of the data that support or refute that point of view. In addition, you should inform the reader of the experimental techniques that were used to generate the data. The emphasis of a paper is interpreting the primary literature on the subject. Please shorten the conclusion. You need to read several original research articles on the same topic and make your own conclusions about the meanings of those papers.

 

Author Response

1. In general, the manuscript recorded a large spacious scale but more than three years of datasets are necessary to assess the efficiency of site selection and plant investigation for six forest communities.

Response: We set up a fixed sample plot in the Huoditang forest area in 2013, and conducted resource surveys and soil measurements every five years thereafter. In 2018, it was postponed to 2019 due to some force majeure. So far we have two years of data.

2. In this study, there are no new methods of vegetation survey proposed by the authors. In what ways do you distinguish this study from others? Physicochemical properties of the soil layers were found to be correlated with plant diversity among forest communities.

Response: In this study, the vegetation survey and soil measurement methods are the same as those of previous studies, but we discusses the relationship between plants and soil from various aspects and angles. We explored the correlations between soils at different depths and the diversity of trees, shrubs, and herbs, and constructed regression models of various diversity indexes and soil factors, It can be used to predict the diversity of trees, shrubs and herbs under different soil nutrient conditions, and then calculate the most suitable soil nutrient status of each forest community, which were rarely seen in previous studies. In addition, most of the previous studies have focused on natural forests or artificial forests. Our research object is natural secondary forests that have undergone natural recovery for decades after severe damage, which is of great significance for the restoration and management of degraded forest systems.

3. Have you checked the normality of species? Can you discern the differences in overall species diversity among forest communities? Would it be possible to distinguish it by using the non-normal distribution identification method?

Response: We have added a statement about the normal distribution test in the Methods section. Before the data analysis, we tested the normal distribution of the data by Kolmogorov-Smirnov test and found that the data was in line with the normal distribution. Therefore, non-normal distribution identification methods were not used for analysis. We quantified the plant diversity at different levels of each community through the diversity index. It's more granular and meaningful. Figure 2 shows the differences in the diversity of trees, shrubs and herbs in each community. The plant diversity of the community as a whole was not calculated.

4. I have some concerns about this work. A significant amount of work needs to be done on the Abstract

Response: There are many deficiencies in the abstract part of the previous manuscript, we have rewritten the abstract section based on the comments of the reviewers.

5. A lack of clarity exists in regards to the study's presentation and purpose or objectives. Please shorten and rephrase some paragraphs so that it's appropriate for the introduction.

Response: We revised the introduction and deleted some content, strengthened the statement of the research purpose. We aimed at explore the action mechanism of the plant-soil system of natural secondary forests in the process of vegetation restoration, evaluating the relationship between soil physiochemical properties and plant community composition. In order to provide scientific basis for forest management and species diversity protection of forest Ecosystem in the process of vegetation restoration

6. In addition, I would like to know more about how the species diversity index is applied.

Response: We added a description of the diversity index in the introduction section(line56-63).

7. Supported on the title there is no clear discussion associated with the decomposition of litter, plant absorption, and other factors. The manuscript presents the results from a study oriented to determine the physiological responses for example total microbial and fungal biomass, and rhizosphere microbial community structure. There is little information about soil functional forest community structure provided in the narrative of the study area.

Response: We changed the research title to the “coupling relationship between soil physicochemical properties and plant diversity in the process of vegetation restoration”, and mainly studied the changes in plant diversity and soil physicochemical properties of the community from 2013 to 2019, as well as their interrelationships. Other aspects such as litter and microorganisms are only used as auxiliary analysis and are not the focus of our research.

8. Several descriptions of how dominant species are being lost in the study area are missing from your narrative. Linkages between forest diversity and soil properties are relevant to interpreting the potential abstraction of the study areas. It would be helpful to include a map of all the study areas.

Response: Our main research goal is to analyze the changes of plant diversity in different years as a whole through the diversity index. Changes in dominant species and important values were not calculated and analyzed. We have added the introduction of community types to the map

9. The authors mention the field data collection was completed for some years. It’s suggested to identify the initial and final sampling dates for the RDA.

Response: Our RDA analysis is from 2013 to 2019. We prefer to understand the relationship between each soil factor and the diversity index through RDA, so we did not add the year distribution.

10. Do the soil samples get collected automatically or are they grabbed? Why were the samples collected randomly; after or during precipitation events? Please clarify. How many samples were obtained per site? What is the size of the samplers (e.g. 1 dm3 or 1l)? Samples were immediately analyzed or some preservation was done before lab analyses were performed? Where were samples collected along with each forest community? Where the samples collected always at the same range of hours? Otherwise, how do the authors manage or evaluate the effects of sampling at different times during a day when evaluating soil properties

Response: We have added a description of soil collection to the Methods section. Five sampling points were set for each tree site according to the five-point method to ensure that the obtained data could represent this plot. Manually sample the four soil layers at each sampling point with a 100cm³ ring knife, and take six ring knife soil samples from each sample point and layer. Three of them were used for the determination of soil bulk density and porosity, and the others were mixed in the same soil layer in a sampling bag and stored in the dark for subsequent laboratory determination of other physicochemical properties. The soil samples were collected in sunny weather in August of that year, from 10:00 am to 6:00 pm, in order to eliminate errors caused by different sampling times as much as possible.

11. To determine the taxa, the authors used the RDA method. In the presentation of the results, it was assumed and corroborated that a high variance was found at soil layers. At least 70 percent of the variance should be explained by all axes. You may find that your multivariate analysis is not robust if you have small factors explaining plant diversity in the shrub layer. This needs to be better explained by the authors. What accounts for the low explained variance? The variance should be even higher than 80% to show strong linkage. It's a standard practice in many publications. Would you please give me an argument why it is necessary to maintain this data if you disagree?

Response: We first screened soil factors through correlation analysis, and selected the factors with strong correlation with the plant diversity index for RDA analysis, which may lead to the explanation degree of some axes being lower than 70%, and we made changes. In addition, the correlation between deep soil and plant diversity is not strong, which is one of the reasons for the low explanatory power. The competition of shrubs and herbs for sunlight and living space can also mask the effects of soil factors on plant diversity.

12. A significant portion of the narrative is devoted to describing the physicochemical properties of soils. Authors are asked to reduce the number of details in their results section or summarize all the results in a table since the outcome is not described sufficiently in this section.

Response: We apologize for the verbose language in the previous text. We have revised the description in the Results section to make it more clear and concise.

13. The statistical analysis should include a statement as to whether the distribution of data is normal or not. It can be added late in the materials and methods section.

Response: We have added a statement on testing for normal distribution of data in the Methods section.

14. As the regression is introduced, it is reiterative of the invitation to elaborate on these results in the Methods section. Apparently, the descriptions are mixed with the calculated and normalized, possibly due to improper listing of the figures.

Response: Our regression model is built by stepwise regression. Model correlations for some diversity indices were too low and were removed.

15. Knowing the actual orientation of the manuscript, it lacks a cohesive description that will lead the reader into the identification of the problem and justification of the study.

Response: We have sorted out the sentence structure of the manuscript to make it more coherent and clear.

16. Unfortunately, the paper failed to tell us what the knowledge gap was or which scientific question they were tracking. Other than question-driven, this paper is more application-oriented. Therefore, I suggest revising the paper to make it more scientific.

Response: We have added a statement about the scientific question tracked by this study and its scientific value in the Introduction and Discussion section. We want to explore the action mechanism of the plant-soil system of natural secondary forests in the process of vegetation restoration, evaluating the relationship between soil physiochemical properties and plant community composition and function. In order to provide scientific basis for the management of the vegetation restoration process of forest ecosystem.

17. It appears there is some confusion regarding the paragraph segment between lines dynamic changes in soil nutrients in different forest communities. There seems to be some confusion concerning the paragraph segment between lines dynamic changes in soil nutrients in forest communities.

Response: We apologize for the confusion of language expressions and logical issues in previous manuscripts. We have adjusted the paragraph structure and language in the this sections to make them more coherent and logical.

18. The reviewer wants to specify only as much as appears in the manuscript, but in a cited statement, the relationship of forest diversity, ecological role, and potential technological applications to environmental conditions is needed.

Response: This is to illustrate that plant diversity is the result of a combination of factors. We have omitted some of these statements.

19. Using your data, can we predict the permeability of soil air, water, and root growth resistance?

Response: Through our research results, we can predict the diversity of trees, shrubs, and herbs under different nutrient conditions, and can also estimate soil nutrient conditions based on the community plant diversity index, which provide a reference for forest management.

20. While the Discussion chapter is rich in information, it does not present the various results in an order that makes sense, nor does it give a proper sense of how to relate the estimation of global trends in broad-leaved tree species and degradation of vegetated ecosystems and ecosystem service. There is no obvious sequence in the narrative from previous statements. Authors should ensure that will construct a vulnerability in vegetation to physicochemical sorption and nutrient availability. Otherwise, soil nutrient content is misunderstood as an indicator of regional-scale ecosystem response to biomass and an indicator of the productivity of forest communities.

Response: We have adjusted the paragraph structure of the Discussion section to make it more logical and, linked the results to species selection and management in the restoration of forest ecosystems. Physicochemical adsorption and nutrient availability are among the factors we discuss. We consider soil physicochemical properties to be one of the indicators of forest community productivity.

21. A key aspect of this paper is that it provides evidence for implications for the management of degraded forest ecosystems. Thus, a large focus of your paper should be a description of the data that support or refute that point of view. In addition, you should inform the reader of the experimental techniques that were used to generate the data.

Response: We discussed the research results combine with the content of degraded forest ecosystems to provide theoretical reference for vegetation restoration and management. In addition, we describe the experimental technique.

22. The emphasis of a paper is interpreting the primary literature on the subject. Please shorten the conclusion. You need to read several original research articles on the same topic and make your own conclusions about the meanings of those papers.

Response: We have condensed our conclusions and expressed our views in conjunction with other research.

 

Thank you very much again for reviewing our manuscript and providing us with valuable suggestions and comments.

 

Round 2

Reviewer 2 Report

A lot of effort has been put into improving the paper. You should re-edit the article for grammar, syntax, and readability.

Author Response

Response to Reviewer

A lot of effort has been put into improving the paper. You should re-edit the article for grammar, syntax, and readability.

Response: We apologize for the poor language problems in our manuscript. We have made repeated changes and deletions to phrases and paragraphs in the manuscript for a long time, which may have resulted in less fluent and poor readability in the text. In addition, due to the author's limited English skills, there may have been some grammatical and syntactic errors in the previous text that added to the bad experience of reading it for you.

To address these issues, we had the manuscript revised again by a professional retouching agency and also had the language corrected by native English speakers. For example, (1) we corrected tense errors in the text; (2) we revised the text for problems with crowns and singulars and plurals; (3) we substituted synonyms and restructured statements for more repetitive words and phrases; (4) we checked the text for improper use of punctuation and letter case. We sincerely hope that fluency and language levels have improved substantially.

Thank you very much again for reviewing our manuscript and providing us with valuable suggestions and comments!