Collaborative Changes between Soil Fauna and Urbanization Gradients in Guangzhou’s Remnant Forests

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The authors explore the characteristics of soil animal communities in residual evergreen broad-leaved forests under different urbanization gradients in Guangzhou and their intrinsic response to environmental changes. A systematic analysis of soil animal communities was conducted using various diversity indices such as Shannon Wiener index, Simpson index, etc. Overall, the manuscript is well written and easy to understand. The reviewer would like to recommend the minor revision before it can be acceptable for the publication. The authors are advised to consider following comments in the revision.

1, Proof reading of the revised manuscript is strongly recommended.

2, The authors should highlight the novelty in the revised manuscript.

3, Figure 1: More explanations should be provided for the gradient lines, decrease or increase from the inside to the outside? What is the increasement?

4, Figures 3-1 to 3-4, it seems that the box-plot is adopted in this study, the authors should explain why some boxes are tall while the others are small. The authors should provide more explanation.

5, Figures 3-5 and 3-6, what is physical meaning the different sizes and different colors of ellipses in those figures?

Comments on the Quality of English Language

Minor Revision may be required. 

Author Response

We sincerely thank the editor and all reviewers for your valuable feedback that we have used to improve the quality of our manuscript. The reviewer comments and suggestions are laid out below in italicized font and specific concerns have been numbered. Our response is given in normal font and changes/additions to the manuscript are presented in the highlight text.

1, Proof reading of the revised manuscript is strongly recommended.

Thank you for the suggestion. We have arranged for thorough proofreading of the revised manuscript to ensure clarity and accuracy.

2, The authors should highlight the novelty in the revised manuscript.

Thank you for pointing that out. In the revised manuscript, we have emphasized the novelty of our study by highlighting several key aspects. Firstly, our research addresses a significant gap in understanding how urbanization affects both the physical and chemical properties of soil in remnant forests, as well as the responses of soil fauna to these environmental changes. We have utilized a unique urbanization gradient approach to explore these effects, which distinguishes our study from existing research that primarily focuses on soil pollutants and physicochemical properties. Furthermore, our findings support the “moderate disturbance hypothesis,” offering new insights into how moderate urbanization may impact soil fauna diversity. By identifying soil organic matter (SOM) and specific pollutants (Pb and Zn) as critical factors influencing soil fauna, our study provides a novel perspective on the interactions between urbanization and soil ecosystems. This approach not only advances the current understanding of soil fauna dynamics in urbanized environments but also informs future research directions. We hope these clarifications underscore the innovative aspects of our work.

3, Figure 1: More explanations should be provided for the gradient lines, decrease or increase from the inside to the outside? What is the increasement?

Thank you for your insightful comments and suggestions for improvement. We have taken your advice into consideration and have enhanced Figure 1 with additional annotations to clarify the gradient lines. The gradient lines are demarcated with Liwan District as the focal point, extending in an eastward direction (R₁=10 km, R₂=20 km, R₃=30 km), respectively, representing high to low levels of urbanization: urban, suburban, and exurban areas. Such a division aligns with the progression of urban development in Guangzhou. Population density, building density, and land use intensity decrease progressively from the urban to the exurban areas. We appreciate the opportunity to improve the presentation of our research and thank you for your guidance.

4, Figures 3-1 to 3-4, it seems that the box-plot is adopted in this study, the authors should explain why some boxes are tall while the others are small. The authors should provide more explanation.

Thank you for your insightful feedback on the boxplots presented in our study. For Figures 3-1 to 3-4, the height of the boxplots reflects the dispersion of the data. Specifically, a higher box indicates greater dispersion within the middle 50 % of the data range, meaning there is more variation; conversely, a shorter box indicates less dispersion, meaning the data fluctuate less within the middle 50 % of the range. We appreciate the opportunity to improve the presentation of our research.

5, Figures 3-5 and 3-6, what is physical meaning the different sizes and different colors of ellipses in those figures?

Thank you for your careful review of our figures. ①Figure 3-5 illustrates the correlation analysis between soil fauna community diversity indices. In this figure, the size of the ellipses represents the strength of the correlation, with larger ellipses indicating stronger correlations. The colors of the ellipses denote the direction of the correlation; for example, red indicates a positive correlation. To enhance clarity, a detailed note explaining the sizes and colors of the ellipses has been added below in Figure 3-5. ②Figure 3-6 shows the correlation coefficients between soil fauna diversity and soil physicochemical properties. Here, the size of the ellipses reflects the absolute value of the correlation coefficient, while the color represents the sign of the correlation. To simplify data interpretation, Figure 3-6 has been converted to a table format, which clearly lists the correlation coefficients and their respective signs. Thank you once again for your attention to our work and your valuable comments. Your feedback has been instrumental in helping us enhance the clarity and effectiveness of our figures.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

Dear authors

This study is very interesting and contains valuable information, but in some sections I found it difficult to understand. I suggest adding a couple of tables with statistical information. And in de discussion section highlight the implications of each result.

The information provided in the introduction section is very interesting and very easy to understand.

1). The title contains many words, I suggest modifying it

2). Lines 116-113. Authors provide important methodological information; however, it makes reading complicated. I suggest first to describe the structure of the study, and then describe each area of ​​study (3 zones, 21 plots, 7 plots per area), and describe the characteristics of each area.

3). In the section 2.2. I suggest to include a figure to show the structure of the samples within the plots

4). I suggest to include one table with the means found with the LSD Analysis.

5).  Line 220. Please describe graphs B and C

6). Table 3-1. What is the spatial reference of the values? Are they the total number of individuals considering the 7 sampling sites per zone or are they per hectare?, Please provide this information

7). Figures 3.5 and 3.6 are not much illustrative, it could be easier to understand whether correlation coefficients and their level of significance are provided in a table. Please consider this suggestion

8). Lines 384 and 385.  “moderate urbanization positively contributes to enhancing soil 384 fauna community richness”.  This statement seems to be controversial. It would be interesting to know which groups show expansion and which ones show reduction according to the study zones

9). I suggest to include at least one conclusion according to the results shown in the figure 3-4 A B.

10). Improve the discussion section, highlight the implications of each result: metals, diversity, correlations and multivariate analysis.

11). In the discussion section. contrast the results of this study with results from others

 

03th 08 2024

Comments for author File: Comments.pdf

Author Response

We sincerely thank the editor and all reviewers for your valuable feedback that we have used to improve the quality of our manuscript. The reviewer comments and suggestions are laid out below in italicized font and specific concerns have been numbered. Our response is given in normal font and changes/additions to the manuscript are given in the highlighted text.

1). The title contains many words, I suggest modifying it

We agree that a more concise title would better capture the essence of our study. We have revised the title to “Collaborative Changes Between Soil Fauna and Urbanization Gradients in Guangzhou’s Remnant Forests”. We believe this revised title effectively reflects the focus of our research while being more succinct. Thank you for your suggestion.

2). Lines 116-113. Authors provide important methodological information; however, it makes reading complicated. I suggest first to describe the structure of the study, and then describe each area of study (3 zones, 21 plots, 7 plots per area), and describe the characteristics of each area.

We thank the reviewer for pointing out this potential confound. We have revised the methodology section to improve clarity and readability as Lines 115-133. We hope this revised description enhances the readability of the methodology section and addresses your concerns.

3). In the section 2.2. I suggest to include a figure to show the structure of the samples within the plots

We think this is an excellent suggestion. We have included a diagram (Fig. 2-2) to illustrate the structure of the samples within the plots. The revised section 2.2 now reads as Line 138-148. We hope this revision meets your expectations.

4). I suggest to include one table with the means found with the LSD Analysis.

Thank you for the suggestion. We include a table summarizing the means and results of the LSD analysis in the Appendix A section of the revised manuscript to provide a clearer comparison and support our findings.

5). Line 220. Please describe graphs B and C

We sincerely appreciate the valuable comments. We have checked this part carefully and added the descriptions of graphs B and C. Line 222-224 “In terms of soil nutrients (Fig.3-1 B, C), similar to the changing pattern of soil pH, urban areas demonstrate markedly higher nutrient levels than the suburban and exurban areas (P <0.05)”. We hope the correction will meet with approval.

6). Table 3-1. What is the spatial reference of the values? Are they the total number of individuals considering the 7 sampling sites per zone or are they per hectare?, Please provide this information.

Sorry for the confusion caused. To clarify the spatial reference of the values, we have revised the table to explicitly reflect the intended meaning. We have replaced ambiguous terms such as “Sum” with more precise descriptions, including “Sum by group” and “Sum by gradient”. Additionally, we have added the following note below the table for further clarity: “Note: Sum by gradient represents the total number of soil fauna individuals collected from the seven sampling sites per gradient; Sum by group represents the total number of individuals for each soil fauna group across all sampling sites.”. We hope this revision addresses your concern.

7). Figures 3.5 and 3.6 are not much illustrative, it could be easier to understand whether correlation coefficients and their level of significance are provided in a table. Please consider this suggestion.

Thank you for this valuable comment.

①Figure 3-5 illustrates the correlation analysis between soil fauna community diversity indices. In this figure, the size of the ellipses represents the strength of the correlation, with larger ellipses indicating stronger correlations. The colors of the ellipses denote the direction of the correlation; for example, red indicates a positive correlation. To enhance clarity, a detailed note explaining the sizes and colors of the ellipses has been added below in Figure 3-5.

②Figure 3-6 shows the correlation coefficients between soil fauna diversity and soil physicochemical properties. Here, the size of the ellipses reflects the absolute value of the correlation coefficient, while the color represents the sign of the correlation. To simplify data interpretation, Figure 3-6 has been converted to a table format, which clearly lists the correlation coefficients and their respective signs.

Thank you once again for your attention to our work and your valuable comments. Your feedback has been instrumental in helping us enhance the clarity and effectiveness of our figures.

8). Lines 384 and 385. “moderate urbanization positively contributes to enhancing soil 384 fauna community richness”. This statement seems to be controversial. It would be interesting to know which groups show expansion and which ones show reduction according to the study zones

Since we did not express it clearly, we are sorry for your misunderstanding. Firstly, the urban, suburban, and exurban gradients represent levels of urbanization from high to low. This gradient classification is based on the urban development processes and environmental factors specific to Guangzhou, as detailed in Line 115-123 of the manuscript. Moreover, the Shannon diversity index (H’) and Pielou’s evenness index (J) of soil fauna in suburban areas are significantly higher than those in the urban and exurban areas with lesser human disturbance. Furthermore, the Simpson dominance index (C) is markedly lower in suburban areas, signifying greater soil fauna richness than in urban and exurban areas. These results suggest that moderate urbanization can enhance soil fauna diversity, making it richer and more evenly distributed, while reducing the dominance of a few species. This pattern aligns with previous studies of Fu, Yu, and Ferris, which also observed that moderate human disturbance can create conditions favorable to diverse soil fauna communities.

Additionally, we acknowledge the importance of understanding which groups show expansion and which show reduction. Based on the statistical results, we preliminarily found that soil fauna groups such as Diplopoda, Microdrile oligochaetes, Symphyla, Isopoda, and Uropygi exhibit a “low-high-low” variation trend with increasing levels of urbanization. Your question is quite insightful and cutting-edge, and we will pay close attention to the research in this field in the future.

9). I suggest to include at least one conclusion according to the results shown in the figure 3-4 A B.

Thank you for your suggestion. We have revised the manuscript to include a conclusion based on the results shown in Figures 3-4 A and B. The updated text is as Line284-291 “In Fig. 3-4 A and B, there are no significant differences in the number of individuals and groups of soil fauna in the remnant forests with different urbanization gradients. Although urban areas display the highest count of individual soil fauna, they exhibit the lowest number of soil fauna groups. This reduction in environmental heterogeneity, alongside habitat fragmentation and heightened environmental stress in urban remnant forests due to prolonged human interference, may lead to the decline of specific soil animal groups. Simultaneously, species with enhanced adaptability demonstrate an increased prevalence, consistent with the findings presented in Table 3-1.”. We hope this addresses your suggestion adequately.

10). Improve the discussion section, highlight the implications of each result: metals, diversity, correlations and multivariate analysis.

Thank you for your insightful comments and suggestions for improving our manuscript. We have tried our best to improve the manuscript and made some changes to the manuscript. These changes will not influence the content and framework of the paper.

①Metals: We elaborated on the significant effects of heavy metals on soil fauna communities, particularly Pb. Pb was found to be positively correlated with the Simpson dominance index and negatively correlated with the Shannon diversity index and Pielou's evenness index. This suggests that Pb pollution reduces soil fauna diversity and simplifies community structure. We compared Pb’s effects with other metals like Zn, Cu, and Cd, discussing the unique mechanisms by which Pb impacts soil fauna.

②Changes in Diversity: We discussed the relationship between urbanization and soil fauna diversity. Urban areas showed significantly lower diversity indices compared to suburban and exurban areas, indicating that urbanization negatively affects soil fauna diversity, while moderate urbanization can enhance community richness. We addressed how these findings align or contrast with existing literature.

③ correlations and multivariate analysis: We discussed the varying responses of soil fauna to different heavy metals, with a particular focus on Pb and Zn. Additionally, we explained how multivariate analysis reveals complex relationships between soil fauna and environmental factors and how these findings contribute to understanding the ecological consequences of soil pollution. Thank you again for your constructive comments.

11). In the discussion section. contrast the results of this study with results from others

Thank you for your feedback. We have indeed contrasted our results with those from other studies in the discussion section. Specifically, we compared our findings on the impacts of urbanization and heavy metal pollution on soil fauna with the results of Lovei, Fu, Yu, and Ferris, highlighting where our findings align or differ. We detailed how our study’s observations on the positive effects of moderate urbanization and the differential responses of soil fauna to heavy metals compare with the existing literature. We appreciate for Editor's warm work earnestly and hope that the correction will meet with approval.

Author Response File: Author Response.pdf