CSR Ecological Strategies and Functional Traits of the Co-Existing Species along the Succession in the Tropical Lowland Rain Forest
Round 1
Reviewer 1 Report
This study investigated functional traits of different successional tree species in tropical lowland rain forests in China using the CSR triangle model.
I think the topic is interesting and suitable for Forests. In addition, the submitted manuscript was really well prepared and written. I think readers can easily follow the whole story. Here I suggest some very minor revisions.
line229-230, legends in Table2, the abbreviation of environmental factors should be spelled out in legends. I think self-explanatory is helpful for the reader.
That's all.
Author Response
Dear editor and reviewers:
Thank you for your constructive comments and suggestions. These comments are very helpful for improving this manuscript. We have done our best to revise this manuscript according to your suggestions, and we hope that this revised version will meet the requirements for publication in forests.
Comments from reviewer # 1:
Thank you very much for your comments of the manuscript. Your suggestion enables us to improve our work. Thank you again for your time and suggestions for the manuscript.
line229-230, legends in Table2, the abbreviation of environmental factors should be spelled out in legends. I think self-explanatory is helpful for the reader.
Response: Thanks for your suggestion. We have added full names of environmental factors here.
Reviewer 2 Report
This is an interesting study based on excellent study design, valuable data and appropriate analyses. The text is logical and well written. I have only few comments that could help to further increase the impact of this paper.
Abstract
L 10-12: I suggest slight changes of this sentence: “We measured key leaf traits and calculated scores for CSR ecological strategy for the co-existing species of 13 species in different succession of the tropical lowland rain forest.” to “We measured key leaf traits and calculated scores for CSR ecological strategy for 13 co-existing species in different stages of succession in tropical lowland rain forests.”
L 16-17: “The co-existing tree species’ strategy from …” should be “The co-existing tree species’ strategy shifts from …”
Introduction
Cited papers: 10, 11 are OK, However, I think citing here some more general (and earlier) literature sources (texbooks, reviews) for general knowledge about succession would be better.
L. 45., 51.: “aggregation” should be “assembly”
L 47-49: This sentence: “However, the successional co-existing tree species still exist in the community after different environmental screening, which reflects that they often have strong adaptability to survival and reproduction.” is not clear. Please reword.
L 58 “irregularly located environments” is not clear, Please, reword or explain.
Please, give a short summary (and add references) about the patterns of functional traits and CSR strategies found in previous studies in succession (for example, the basic trends of strategies described in Grime’s book (page 151 Fig. 42).
Material and Methods
L 112 “at least eight individuals for each species” (measured) is not clear. Eight individuals in each plots (8 x 8 in total)? Please, clarify. Please, consider intraspecific trait variability of species along successional gradients (For example: Chelli et al. 2022. Intra- and inter-specific leaf trait responses of understorey species to changes in forest maturity Forest Ecology and Management 506).
L 121: It would be useful (and probably well cited by other scientists) creating an appendix with mean trait values of species representative for the different successional stages (or you could publish these data separately).
Please, add a new table with the most important vegetation characteristics in each successional stages (density of trees, heights of canopy, vertical layers, structural complexity, total cover or biomass in each layer, and the number of species) and another summary of basic statistics of environmental data sampled and used in analyses (cf. Table 2) These data would be very important for understanding (and interpreting) the shifts in functional trait composition.
L 146-148: log transformation is often used for trait data to fit assumptions of normal distribution. Have you checked these aspects? What data transformations were used?
It is typical in succession that species composition changes: dominant and abundant species replace each other (species turnover). However, in this study the selected species persisted in all stages (Table 1.). Based on Table 1, it is correct to speak about “tree-species coexistence”. Still it needs further explanation. Were these species emergent (or dominant) components of forest canopy at all successional stages? Are these species representative for the whole community? (For example, was their summa cover more or equal 80% of total cover or biomass.) Why did you select this subset of the forest community? An obvious reason could be the investigation of intraspecific trait variability along the successional gradient (cf. Chelli et al 2022 Intra- and inter-specific leaf trait responses of understorey species to changes in forest maturity Forest Ecology and Management 506) However, I did not find here explicit reference about intraspecific patterns of traits among results.
Results
L 205: “while the circle represents the individual strategic value of a single species” Please, clarify. 13 species were studied. Therefore 13 circles should be present on ternary diagrams. However, the number of circles is larger.
Discussion
L 254-257: “As expected, species showed different strategies along the chronosequence, and even different individuals of species at the same succession stage are not the same. This suggests that within-species variation in CSR strategy is common [31].” This is a very interesting result and it would need better illustration by the data collected here and more detailed explanation.
L 269-281. This part could be explained in more efficiently and in more explicit way if you would reflect the stand structure and environmental data that are characteristic in each successional stage. You could use here the new summary table (I suggested for forest stand structure data and environmental data).
I miss from Discussion a comparison between trends of plant functional trait patterns between temperate and tropical forest succession and the related evaluation.
L 297-299. Not clear. What increasing R component means? (Ruderal trees are missing as you said in L 246-247.) Filtering by decreasing light availability and by increasing competition for nutrients do not represent an increasing selection for R strategy (at least not in my mind). Please, explain.
L 303 „These results are consistent with Grime 's prediction” I think NOT. Please, explain in details. In my reading (p 151 in Grime’s book) his prediction was an R -> C -> S trend in succession which is not consistent with the results in this paper (cf. Fig 2).
References
Please complete the following references:
L 352: 7.
L 365: 13.
L 435: 48.
Author Response
Dear editor and reviewers:
Thank you for your constructive comments and suggestions. These comments are very helpful for improving this manuscript. We have done our best to revise this manuscript according to your suggestions, and we hope that this revised version will meet the requirements for publication in forests.
Comments from reviewer # 2:
Abstract
1.L 10-12: I suggest slight changes of this sentence: “We measured key leaf traits and calculated scores for CSR ecological strategy for the co-existing species of 13 species in different succession of the tropical lowland rain forest.”to“We measured key leaf traits and calculated scores for CSR ecological strategy for 13 co-existing species in different stages of succession in tropical lowland rain forests.”
Response: Thank you for your constructive comment. We modified it according to your suggestion.
2.L 16-17: “The co-existing tree species’ strategy from …” should be “The co-existing tree species’ strategy shifts from …”
Response: Thanks for your checks. We added “shifts”.
Introduction
1.Cited papers: 10, 11 are OK, However, I think citing here some more general (and earlier) literature sources (texbooks, reviews) for general knowledge about succession would be better.
Response: Thanks for your suggestion. We added some more general literature sources for this study.
Ewel JJ, 1980. Tropical succession: manifold routes to maturity. Biotropica 12:2.
Norden N, Chazdon RL, Chao A, Jiang Y-H, Vílchez-Alvarado B, 2009. Resilience of tropical rain forests: tree community reassembly in secondary forests. Ecol Lett 12:385-394.
2.L. 45, 51 :“aggregation” should be “assembly”
Response: Thank you for your careful review of our manuscript. According to your opinion, we have revised “aggregation” into “assembly”.
3.L 47-49: This sentence: “However, the successional co-existing tree species still exist in the community after different environmental screening, which reflects that they often have strong adaptability to survival and reproduction.” is not clear. Please reword.
Response: We rewrite this sentence as follows “During the succession process, the species composition changes, but there are some co-existing species in each stage of succession. They are often highly adaptable to environmental changes, showing strong ability of survival and reproduction. Co-existing species in the succession process deserve our attention”.
4.L 58 “irregularly located environments” is not clear, please, reword or explain.
Response: We change the “irregularly located environments” to “variable environments”.
Please, give a short summary (and add references) about the patterns of functional traits and CSR strategies found in previous studies in succession (for example, the basic trends of strategies described in Grime’s book (page 151 Fig. 42).
Response: Thank you very much for your suggestion. We added a paragraph about the succession mode of ecological strategy. "In the process of ontogeny, leaves change greatly, including intraspecific variation and interspecific variation. Therefore, the CSR strategy of individual species and vegetation will have a significant change trend. The research shows that the CSR strategies evidence for species characteristic of primary success from scree vegetation to siliceous alpine grassland, terminating with alpine Nardus pasture, are evident：an initial shift from R- to S-selection. Grime thinks that the early stage of secondary succession is dominated by R-strategy, and S-strategy is the dominant in the later stage, while the importance of C- strategy is related to environmental productivity. Therefore, there are many patterns of community succession. The change pattern of vegetation CSR strategy and the relationship between its environment help to reflect the succession process and its driving force. "
Material and Methods
1.L 112 “at least eight individuals for each species” (measured) is not clear. Eight individuals in each plots (8 x 8 in total)? Please, clarify. Please, consider intraspecific trait variability of species along successional gradients (For example: Chelli et al. 2022. Intra- and inter-specific leaf trait responses of understorey species to changes in forest maturity Forest Ecology and Management 506).
Response: Thanks for your checks. In the four succession stages, 13 successional coexisting species were found. After data screening, we selected 8 individuals from 13 successional coexisting species in each succession stage for measurement.
L 121: It would be useful (and probably well cited by other scientists) creating an appendix with mean trait values of species representative for the different successional stages (or you could publish these data separately).
Response: Thank you very much for your suggestion. We have created Appendix with mean trait values of species representative for the different successional stages.
Please, add a new table with the most important vegetation characteristics in each successional stages (density of trees, heights of canopy, vertical layers, structural complexity, total cover or biomass in each layer, and the number of species) and another summary of basic statistics of environmental data sampled and used in analyses (cf. Table 2) These data would be very important for understanding (and interpreting) the shifts in functional trait composition.
Response: Thank you for your suggestion. For the convenience of understanding, we have added the data of leaf traits, ecological strategy values and corresponding environmental factors of this research object in Appendix. The community proportion of 13 common species in each succession stage are shown in Appendix.
L 146-148: log transformation is often used for trait data to fit assumptions of normal distribution. Have you checked these aspects? What data transformations were used?
Response: Thank you very much for your checks. We use log transformation to check the normality of the data. To allow for parametric statistical analyses, we log-transformed traits values before analysis.
It is typical in succession that species composition changes: dominant and abundant species replace each other (species turnover). However, in this study the selected species persisted in all stages (Table 1.). Based on Table 1, it is correct to speak about “tree-species coexistence”. Still it needs further explanation. Were these species emergent (or dominant) components of forest canopy at all successional stages? Are these species representative for the whole community? (For example, was their summa cover more or equal 80% of total cover or biomass.) Why did you select this subset of the forest community? An obvious reason could be the investigation of intraspecific trait variability along the successional gradient (cf. Chelli et al 2022 Intra- and inter-specific leaf trait responses of understorey species to changes in forest maturity Forest Ecology and Management 506) However, I did not find here explicit reference about intraspecific patterns of traits among results.
Response: In total, we encountered 383 species in this study, 120 species in 18-yr-old forests ;171 species in 30-yr-old forests ;195 species in 60-yr-old forests and 250 species in old growth forests. After data screening, 13 co-existing tree species were found. The Figure in Appendix shows the proportion of species of coexisting species and the proportion of individuals of co-existing species in the four succession stages. We found that the number of individuals of coexisting species was dominant in the community. Studying coexisting species is of great significance for us to understand the stability of species aggregation in succession. Our results also confirmed the variation of intraspecific traits, and we added the reference in this paper.
Results
1.L 205: “while the circle represents the individual strategic value of a single species” Please, clarify. 13 species were studied. Therefore 13 circles should be present on ternary diagrams. However, the number of circles is larger.
Response: Thank you for your careful examination. The square in the picture represents the average ecological strategy of each species, and the circle represents the ecological strategy of each individual. Each species has 8 individuals, totaling 104 circles. We have marked it in the text.
Discussion
1.L 254-257: “As expected, species showed different strategies along the chronosequence, and even different individuals of species at the same succession stage are not the same. This suggests that within-species variation in CSR strategy is common [31].” This is a very interesting result and it would need better illustration by the data collected here and more detailed explanation.
Response: We added more detailed explanation to describe this interesting result. “Species showed different strategies along the chrono sequence, and even different in-dividuals of species at the same succession stage are not the same (for example, Lasianthus hainanensis. showed S/CS, CS and CS/CSR strategy). The diversity of ecological strategies among species is conducive to maintaining biodiversity and ecosystem functions, and is the basis of species coexistence. The diversity of intra-species ecological strategies can enhance the adaptability of species to the environment and enhance the ability of species to survive and reproduce.”
2.L 269-281. This part could be explained in more efficiently and in more explicit way if you would reflect the stand structure and environmental data that are characteristic in each successional stage. You could use here the new summary table (I suggested for forest stand structure data and environmental data).
Response: Thank you for your constructive suggestions. We have added tables about environmental and plant functional traits and ecological strategy in Appendix, which will help to understand the results.
3.I miss from Discussion a comparison between trends of plant functional trait patterns between temperate and tropical forest succession and the related evaluation.
Response: Thank you for your opinion. That's a good idea. We will study the relationship between tropical and temperate zones in depth in our future work. This paper focuses on the study of tropical lowland rain forest.
4.L 297-299. Not clear. What increasing R component means? (Ruderal trees are missing as you said in L 246-247.) Filtering by decreasing light availability and by increasing competition for nutrients do not represent an increasing selection for R strategy (at least not in my mind). Please, explain.
Response: Thanks to your constructive suggestion, we revised our statement that “the weight of R increased in the late succession stage, which indicated that the plant ecological strategy had changed. In order to adapt and respond to environmental changes, plants have made more complicated trade-offs to maintain the most competitive position. ”
5.L 303 „These results are consistent with Grime 's prediction”I think NOT. Please, explain in details. In my reading (p 151 in Grime’s book) his prediction was an R -> C -> S trend in succession which is not consistent with the results in this paper (cf. Fig 2).
Response: Thank you very much for correcting our mistake. After checking, we corrected this mistake. “Our results do not support Grime's prediction of secondary succession ecological strategy. First of all, the R-strategy does not have a dominant position in the early stage of succession. The reason for this difference may be that the early succession in this study started from a secondary forest, while Grime’s early succession were from bare soil. In this study, we mainly focus on woody plants are generally considered to change between C and S selection. Secondly, in our research, the S-strategy is not dominant in the late succession stage, but there are more advantages of the C-strategy. Therefore, we speculate that with the succession, the forest has been well restored and the environmental productivity has been improved.”
