Shading Effects on the Growth and Physiology of Endangered Hopea hainanensis Merr. & Chun Seedlings

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

Dear authors, congratulations for your work.

The research, despite not being completely innovative or original considering the applied concepts and methodologies that have already been applied to other species, presents relevant results for an endangered specie (Hopea hainanensis). For this reason, the results may help in the definition of strategies for conservation and/or reforestation.

The experimental design methodology is clear and was well planed and easy to follow in the paper.

The results are clear and the conclusions derived from these results.

Please note that one of the main issues here is the literature review. Many papers found for this species are not in english and this limits, for non chinese reviewers, the comparison with other results. Examples: file:///C:/Users/joanaap/Downloads/Habitat%20characteristics%20and%20its%20effects%20on%20seedling%20abundance%20of%20Hopea%20hainanensis,%20a%20Wild%20Plant%20with%20Extremely%20Small%20Populations.pdf or http://www.ivypub.org/BF/cn/paperinfo/59879.shtml

 

Some comments to this version of the manuscript.

A) please revise and update key words. They are in part a repetition of the title. Avoid that. I suggest you add some related to the most relevant and differentiating parameters you found in your results.

B) Methods. I find section 2.3 a bit short. Please add more detail on the methods, reasoning for them and software used.

C) The last paragraph in the discussion section needs revision since the end part is some how separated from the rest.

D) please make a final EN revision.

Congratulations

Author Response

Response to Reviewer 1 Comments

Comment 1: Please note that one of the main issues here is the literature review. Many papers found for this species are not in english and this limits, for non chinese reviewers, the comparison with other results.

Response 1:  we sincerely appreciate your insightful critique regarding the accessibility of non-English literature. To enhance global comparability, we have integrated some key English-language studies on shade adaptation. For details, please refer to the Introduction and the Discussion.

Comment 2: please revise and update key words. They are in part a repetition of the title. Avoid that. I suggest you add some related to the most relevant and differentiating parameters you found in your results.

Response 2: We sincerely thank the reviewer for the valuable suggestion. We agree that the original keywords were partially redundant with the title and lacked specificity regarding key findings. Following the reviewer’s advice to highlight the most relevant and differentiating parameters from our results, we have completely revised the keywords to: shading; growth; gas exchange; leaf pigments; biomass accumulation; adaptation.

Comment 3: Methods. I find section 2.3 a bit short. Please add more detail on the methods, reasoning for them and software used.

Response 3: We thank the reviewer for highlighting the need for greater methodological clarity. In the revised manuscript, we have expanded Section 2.3 to include:

Lines 210-222: The experimental data were analyzed using Microsoft Excel 2019 software. Analysis of variance (ANOVA) was employed to statistically assess the overall impact of shading on 21 key parameters—encompassing growth indices (plant height increment, stem diameter increment, and dry weights of various organs), leaf morphological indices (e.g., leaf length, leaf width), and photosynthetic parameters (e.g., net photosynthetic rate, stomatal conductance). The original data were log-transformed to satisfy the normality and homoscedasticity assumptions of ANOVA. The means of 21 key parameters were compared via Duncan’s new multiple range method, ith statistical significance defined at p < 0.05. All statistical analyses were conducted using SPSS 26.0 (IBM). Seedling shade tolerance was comprehensively evaluated using a principal component analysis (PCA). Results were visualized in OriginPro 2021b (OriginLab) with standard formatting; error bars represent standard errors (SEs). All tabular and graphical data presentations illustrate the mean ± SE.

Comment 4: The last paragraph in the discussion section needs revision since the end part is some how separated from the rest.

Response 4: We thank the reviewer for this insightful observation. We have restructured the final paragraph as follows:

Lines 403-426: Plant shade stress tolerance emerges from integrated growth-physiology trade-offs, necessitating multivariate assessments of plant shade responses [1]. Here, a principal component analysis revealed a consistent hierarchy in H. hainanensis seedling performance across shading treatments: T0 (full light) > T1 (30% shading) > T2 (60%) > T3 (90%). Physiological suppression became significant when shading caused more than a 30% reduction in irradiance—a critical threshold aligning with the species’ photoadaptive capacity and optimal shade ranges for C. hystrix (60%) and Q. ilex (40–70%) [10,22]. In the tropical rainforest understory, dense canopy layers typically permit < 2% light transmission [39], suggesting chronic light limitation as a primary constraint to natural regeneration in H. hainanensis. Notably, light requirements for this species increase ontogenetically, demanding dynamic cultivation protocols that mirror natural regeneration niches [38]. To resolve this light-limitation bottleneck, We propose a light-gradient acclimation cultivation strategy: Initial cultivation under 30% shading optimizes stem elongation; subsequent developmental phases progressively increase irradiance to stimulate radial growth; ultimately transitioning seedlings to full sunlight during maturation. While acknowledging study limitations—particularly the simplified nursery environment omitting natural biotic interactions (e.g., competition, herbivory) and abiotic heterogeneity (e.g., soil moisture gradients), alongside the focus on short-term (one-year) seedling responses—these findings provide mechanistic insights into photoadaptive thresholds. Future research should: (1) validate cultivation protocols in field settings incorporating edaphic and biotic variables; (2) quantify long-term photoinhibition dynamics under sustained shade regimes; and (3) integrate transcriptomic analyses to elucidate molecular drivers of observed ontogenetic shifts in light adaptation.

Comment 5: please make a final EN revision.

Response 5: We sincerely appreciate the reviewer’s guidance on language refinement. We have conducted a comprehensive English revision of the entire manuscript.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

The article “Shading effects on the growth and physiology of endangered Hopea hainanensis seedlings” is interesting and well-written. In this article, determine optimal light conditions for H. hainanensis seedling growth and examined seedling biomass allocation, morphology, and photosynthetic efficiency under four shading treatments (0%, 30%, 60%, and 90% irradiance reduction) throughout the year. They observed significant differences (p < 0.05) in seedling growth and photosynthetic parameters across treatments and found that as shading increased, seedling height, leaf area, leaf length, leaf width, the light saturation point, and the specific leaf area all initially increased, peaked at 30% shading, and then decreased. Further, the results of multivariate analysis, shading levels of 0%-30% were determined to be optimal for H. hainanensis seedling cultivation, with moderate shading (30%) enhancing photomorphogenic responses while maintaining photosynthetic efficiency. The purpose of this study is clear, the data is reasonable and feasible, and comprehensive. The analysis method of the article is sound. And the discussion content is in detail and sufficient. Thus, the manuscript needs major revisions.

 

Comments and suggestions about manuscript

Title

The title is good.

Abstract

• Line 15-37: According to journal (Forests) policy, the abstract should not exceed 200 words; your abstract is more than 250 words. So please rewrite the precise and short Abstract to meet the journal’s requirements and for easy understanding of readers.
• Kick-start the abstract by highlighting the importance of reported work. Briefly discuss the methods used and then discuss key results.
• Line 38-39: Keywords must be rewritten and arranged alphabetically to enhance the visibility of your article. Please remove the word (Hopea hainanensis;) from the keywords because you have already used this word in the title, and add more suitable word.

 

Introduction

Please rewrite the Introduction considering these questions:

• What will benefit the scientific community/society of your study?
• What is the significance of your research?
• Why did you choose the Hopea hainanensis? Is there some specific reason? If yes, then explain.
• The literature and the data introduced in the Introduction section should finally be compared with the obtained results for discussion.
• Line 121-126: Researchers and scientists encourage hypothesis-driven research. What is the hypothesis of your research? I strongly recommend you add your research hypotheses at the end of the introduction.

 

Materials and Methods

Materials and Methods section need to improve.

• I strongly recommend to add the study area map.
• Please add a schematic diagram to enhance your Article's visibility and easy understanding.
• Line 129-136: Please provide reference.

Results

Line 288-304: Please add the picture of PCA (PC1 and PC2 components) to clarify the first two principal components together explained 95.74% of the total variance.

Discussion and Conclusions

Overall, both sections are fine. However, in discussion or conclusion sections, the limitation of this study may need to be added.

References

References section is fine.

Hopefully, these suggestions will help you to improve your Article.

Good luck.

Author Response

Response to Reviewer 2 Comments

Comment 1: Line 15-37: According to journal (Forests) policy, the abstract should not exceed 200 words; your abstract is more than 250 words. So please rewrite the precise and short Abstract to meet the journal’s requirements and for easy understanding of readers. .

Response 1: We thank the reviewer for this critical guidance. We have comprehensively revised the abstract to strictly comply with the 200-word limit (current: 199 words) while preserving all key scientific contributions. The revised summary is as follows.

Line 15-33: To determine optimal light conditions for Hopea hainanensis seedling growth, this study examined growth and physiological parameters under four shading treatments (0%, 30%, 60%, and 90% irradiance reduction) over 12 months. Shading significantly affects the growth adaptability of seedlings. As shading increased, height, leaf traits (area, length, width) and light saturation point all initially increased, peaked at 30% shading, and then decreased. Conversely, basal diameter, leaf thickness, the maximum net photosynthetic rate, net photosynthetic rate, photosynthetic quantum efficiency, transpiration rate, and stomatal conductance progressively declined as shading increased. Biomass accumulation (in stems and roots), dark respiration rate and light compensation point, exhibited a U-shaped response to shading, being minimized under low or moderate shading. All shading treatments significantly reduced biomass and photosynthetic performance compared to controls. Multivariate analysis identified 0%-30% shading as optimal for cultivation, with 30% shading enhancing photomorphogenic responses while maintaining photosynthetic efficiency. The study findings suggest a novel seedling cultivation protocol for nursery use, in which initial establishment occurs under 30% shading to maximize vertical elongation, followed by the progressive reduction of shading to stimulate radial growth and optimal biomass partitioning. This approach mimics natural canopy gap dynamics, effectively mimicking natural regeneration in tropical rainforest ecosystems.

Comment 2: Line 38-39: Keywords must be rewritten and arranged alphabetically to enhance the visibility of your article. Please remove the word (Hopea hainanensis;) from the keywords because you have already used this word in the title, and add more suitable word.

Response 2:  We sincerely thank the reviewer for careful reading. we have completely revised the keywords to: shading; growth; gas exchange; leaf pigments; biomass accumulation; adaptation.

Comment 3: Please rewrite the Introduction considering these questions: What will benefit the scientific community/society of your study? What is the significance of your research? Why did you choose the Hopea hainanensis? Is there some specific reason? If yes, then explain. The literature and the data introduced in the Introduction section should finally be compared with the obtained results for discussion.

Line 121-126: Researchers and scientists encourage hypothesis-driven research. What is the hypothesis of your research? I strongly recommend you add your research hypotheses at the end of the introduction.

Response 3:  We deeply appreciate the reviewer’s constructive guidance. The Introduction has been comprehensively restructured to address all concerns.

Line 38-138:  can be found in the revised version of the thesis.

Comment 4: I strongly recommend to add the study area map.

Please add a schematic diagram to enhance your Article's visibility and easy understanding.

Response 4:  We have added the study area map (Figure 1.).

Comment 5: Line 129-136: Please provide reference.

Response 5:  We have added references, see Line 149 for details.

Comment 6: Line 288-304: Please add the picture of PCA (PC1 and PC2 components) to clarify the first two principal components together explained 95.74% of the total variance.

Response 6:   We sincerely appreciate this valuable suggestion. As requested, we have added Figure 5 and 6 to Section 3.4.2 of the Results. The revised text now references Figure 6 and 7 in Lines 319-321 and 322-329.

Comment 7: Overall, both sections are fine. However, in discussion or conclusion sections, the limitation of this study may need to be added.

Response 7:   We sincerely appreciate this valuable suggestion. As requested, we have added the limitation of this study in Lines 419-426.

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

The article "Shading effects on the growth and physiology of endangered Hopea hainanensis seedlings" is written clearly and logically. The authors analyzed a large array of data and made interesting conclusions that have undoubted practical value. However, to improve the perception of information by readers, I would like to recommend the authors to make the following corrections to the text.

1. The authors should add the relevance and novelty of the study to the Abstract (1-2 sentences). The sentence on lines 18-19 should be deleted, since it does not carry a significant semantic load, and the significance level (p < 0.05) is sufficient to indicate in the Materials and Methods. At the moment, the results of the study in the Abstract are presented in sufficient detail; if the authors could present them more briefly, this would significantly improve this section.
2. In the text, when describing the results obtained (lines 204, 206, 223 and others), specific numerical data should not be written - they are already presented in the diagrams. It is necessary to indicate by how many % / how many times the studied parameter changed after the stress impact. It is also not necessary to indicate the % of changes to hundredths of a share - the measurement accuracy and the significance level do not allow this. It is better to round all percentages of changes to whole numbers, and if authors have to compare two statistically indistinguishable groups, then indicate the range (10-20%, 20-40%, etc.). Only the observed trends of changes and their significance are important - hundredths of a percent are not important in this case.
3. The authors should carefully check the entire description of the obtained results, since it often does not quite correspond to the presented diagrams. Thus, on lines 203-204, the authors write that "The SHI exhibited a unimodal response to shading, being highest in T1 (78.53 cm) and lowest in T3 (30.60 cm)". However, it is clear from Figure 1a that T0 and T1 do not differ statistically (a similar situation is for T2 and T3). Accordingly, it should be written that shading T1 did not lead to changes in SHI, while shading T2 and T3 reduced this parameter by about 30-40%.

Line 209. The authors indicate that "SDW and RDW showed parabolic trends". However, if we take into account the differences indicated in Figures 1c and 1e, then we get not a parabolic change, but a "monotonically" decrease (as for BDI), since points T2 and T3 do not differ statistically.

A similar situation is on line 250. The authors write that "the LSP showed a unimodal pattern, peaking in T1 (1543.33 µmol/m²/s), then declining to 926.67 µmol/m²/s under heavy shading (T3)". However, Figure 3g notes that T0, T1 and T2 do not differ statistically, so it cannot be said that LSP peaks in T1. Only a decrease in LSP at T3 can be discussed.

Thus, the authors should check the description of all results to align them with the diagrams and statistical analysis. It should be noted that only statistically significant differences should be described.

4. The authors provide a description of the results in the Discussion, but do not provide the numbers of the figures in which they are presented. This complicates the perception of information by readers. For example, at the end of the sentence, on the line 313 ("Meanwhile, the basal diameter increment and total biomass (of stems, leaves, and roots) progressively declined with the shading intensity, with a 54.3% reduction in total biomass observed under heavy shading (T3) as compared to full-light controls.") – " (Figure 1)" can be added. Similarly, on the lines 320, 329, etc. The Discussion should also avoid mentioning specific numerical data (e.g., as on line 309) or % changes (as on line 312). The description of the obtained results was given in the previous section, and thus there is duplication of the text. When discussing the results and comparing them with the literature, one should talk about the general observed trends, an increase or decrease in the parameter under discussion.

Minor comments.

1. Line 56. After the words "photosystem II" the abbreviated version (PSII) should be indicated, since the authors use it further in the text.
2. Line 203 and similar cases - p < 0.05. The significance level should be indicated once in section 2.3 Data Statistics and Analysis.

Comments for author File: Comments.pdf

Author Response

Response to Reviewer 3 Comments

 

 

Comment 1: The authors should add the relevance and novelty of the study to the Abstract (1-2 sentences). The sentence on lines 18-19 should be deleted, since it does not carry a significant semantic load, and the significance level (p < 0.05) is sufficient to indicate in the Materials and Methods. At the moment, the results of the study in the Abstract are presented in sufficient detail; if the authors could present them more briefly, this would significantly improve this section.

Response 1: We sincerely appreciate this valuable suggestion. We have made revisions, as detailed in the abstract (Lines 15-33).

Comment 2: In the text, when describing the results obtained (lines 204, 206, 223 and others), specific numerical data should not be written - they are already presented in the diagrams. It is necessary to indicate by how many % / how many times the studied parameter changed after the stress impact. It is also not necessary to indicate the % of changes to hundredths of a share - the measurement accuracy and the significance level do not allow this. It is better to round all percentages of changes to whole numbers, and if authors have to compare two statistically indistinguishable groups, then indicate the range (10-20%, 20-40%, etc.). Only the observed trends of changes and their significance are important - hundredths of a percent are not important in this case.

Response 2: We appreciate the reviewer's meticulous guidance on results presentation. All specific numerical values have been removed from the text, percentage changes rounded to whole numbers, and trends emphasized. Absolute measurements (e.g., μmol/m²/s) are now exclusively in figures, with textual focus on relative changes and statistical patterns . Please refer to the revised version of the paper for details(3. Results).

Comment 3: The authors should carefully check the entire description of the obtained results, since it often does not quite correspond to the presented diagrams. Thus, on lines 203-204, the authors write that "The SHI exhibited a unimodal response to shading, being highest in T1 (78.53 cm) and lowest in T3 (30.60 cm)". However, it is clear from Figure 1a that T0 and T1 do not differ statistically (a similar situation is for T2 and T3). Accordingly, it should be written that shading T1 did not lead to changes in SHI, while shading T2 and T3 reduced this parameter by about 30-40%.Line 209. The authors indicate that "SDW and RDW showed parabolic trends". However, if we take into account the differences indicated in Figures 1c and 1e, then we get not a parabolic change, but a "monotonically" decrease (as for BDI), since points T2 and T3 do not differ statistically.

Response 3: Thank you for highlighting the critical discrepancy in SHI interpretation. We confirm that statistical non-differentiation between T0-T1 and T2-T3 groups in Figure 1a necessitates revised text. The description now strictly aligns with statistical groupings, removing "unimodal response" and "highest" claims where insignificant differences exist. All other parameter descriptions maintain congruence with their respective figures.

Line 225-234: Shading treatments induced significant morphological differentiation in H. hainanensis seedlings. The SHI showed no significant change under light shading (T1) compared to full-light controls (T0), whereas moderate (T2) and heavy shading (T3) reduced SHI by approximately 35% and 42% respectively(Figure. 2a). The BDI decreased progressively with shading intensity, showing marked reductions across all shaded treatments (Figure. 2b). Biomass partitioning revealed organ-specific responses: SDW and RDW exhibited a U-shaped response to shading (maxima at T0), while LDW and TDW declined continuously with shading intensity (Figure. 2c-f). Notably, the TDW was 35% lower in T3 than T0. All shading treatments showed reduced biomass accumulation relative to the control.

Comment 4: A similar situation is on line 250. The authors write that "the LSP showed a unimodal pattern, peaking in T1 (1543.33 µmol/m²/s), then declining to 926.67 µmol/m²/s under heavy shading (T3)". However, Figure 3g notes that T0, T1 and T2 do not differ statistically, so it cannot be said that LSP peaks in T1. Only a decrease in LSP at T3 can be discussed.

Response 4: We sincerely appreciate your rigorous scrutiny of statistical alignment. The description of LSP response has been revised to strictly reflect Figure 3g's statistical groupings (T0-T2 insignificant differences). All claims about unimodal patterns or T1 peaks have been removed, with focus restricted to the significant reduction at T3. Other photosynthetic parameter descriptions remain unchanged as they align with their respective figures.

Line 262-271: Shading treatments significantly altered photosynthetic efficiency in H. hainanensis seedlings. Key photosynthetic parameters progressively declined as shading increased. For example, compared to the control, Pn decreased by 24% (T1), 40% (T2), and 62% (T3), while AQY declined by 25%-86%, Gs by 53%-90%, Pmax by 31%-70%, and Tr by 22%-78% (Figure. 4a,b,c,e,i). In contrast, Ci monotonically increased with shading intensity (by 20%-48%) (Figure. 4d). Both LCP and RD showed nonlinear responses to shading; the LCP achieved minimum and maximum values in T1 and T3, respectively, whereas RD showed the defferent pattern, being highest in T0 and lowest in T2 (Figure. 4f, h). Notably, the LSP showed no significant differences among T0-T2 treatments but declined markedly in T3 (Figure. 4g).

Comment 5: Thus, the authors should check the description of all results to align them with the diagrams and statistical analysis. It should be noted that only statistically significant differences should be described.

Response 5: We sincerely appreciate the reviewer's rigorous guidance. We have systematically re-examined all result descriptions to ensure strict alignment with statistical groupings in the figures.

Comment : The authors provide a description of the results in the Discussion, but do not provide the numbers of the figures in which they are presented. This complicates the perception of information by readers. For example, at the end of the sentence, on the line 313 ("Meanwhile, the6 basal diameter increment and total biomass (of stems, leaves, and roots) progressively declined with the shading intensity, with a 54.3% reduction in total biomass observed under heavy shading (T3) as compared to full-light controls.") – " (Figure 1)" can be added. Similarly, on the lines 320, 329, etc. The Discussion should also avoid mentioning specific numerical data (e.g., as on line 309) or % changes (as on line 312). The description of the obtained results was given in the previous section, and thus there is duplication of the text. When discussing the results and comparing them with the literature, one should talk about the general observed trends, an increase or decrease in the parameter under discussion.

Response 6: We sincerely appreciate your guidance on enhancing discussion clarity. We have:

(1) Deleted all specific numerical data (measurements, percentages); (2) Added figure references for all result descriptions; (3) Replaced quantitative statements with qualitative trends; (4) Eliminated text duplication with Results section.

Line 332-397: 

Comment 7: Line 56. After the words 'photosystem II' the abbreviated version (PSII) should be indicated.

Response 7: We have added the abbreviation "(PSII)" after the first occurrence of "photosystem II" in the Introduction (Line 54). All subsequent uses now employ the standardized abbreviation "PSII" for consistency.

 

Comment 8: Line 203 and similar cases - p < 0.05. The significance level should be indicated once in section 2.3.

Response 8: The significance level notation (p < 0.05) has been removed from all Results section statements (including Line 203) and is now exclusively stated in Section 2.3 (Data Statistics and Analysis). Global verification confirms no residual p-value annotations exist outside the methods section.

 

 

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

Comments and Suggestions for Authors

Thanks to the authors for critically addressing my concerns. I am satisfied with the current version. 

Author Response

Response to Reviewer #2
Dear Reviewer,

We are deeply grateful for your generous feedback and meticulous guidance throughout the review process. Your insightful critiques were invaluable in strengthening the scientific rigor and clarity of our manuscript. We are honored that the revised version now meets your approval, and we sincerely appreciate your time and expertise in advancing this work.

Should any minor refinements arise during production, we remain fully committed to addressing them promptly. Thank you again for your vital contribution to shaping this research.

With utmost respect,
Mengwen Zhang
On behalf of all authors

Reviewer 3 Report

Comments and Suggestions for Authors

I am sincerely grateful to the authors for their work on correcting the manuscript of the article. I have no more serious comments - the authors took into account all my wishes and revised the text.
Small comments. I ask the authors to pay attention to the following lines:
280 - "different" instead of "defferent",
422 - there are probably typos, or part of the corrected sentence was accidentally deleted,
441 - "we" instead of "We".

Author Response

Response to Reviewer 3 Comments

Thank you for your gracious feedback and meticulous proofreading! We sincerely appreciate your endorsement of our revisions and are pleased that the manuscript now meets your expectations. We have carefully addressed the minor typographical errors you highlighted:

Comment 1: 280 - "different" instead of "defferent",.

Response 1:  Thank you for catching this typo. We have corrected "defferent" to "different" in Line 280.

Revised Text:

"...showed the different pattern..."

Comment 2: 422 - there are probably typos, or part of the corrected sentence was accidentally deleted.

Response 2: We sincerely appreciate your vigilance. The perceived issue resulted from an accidental double period (..) at the end of the sentence during editing, not a deleted fragment. We have corrected this punctuation error to ensure clarity.

Revised Text (Corrected):

“......while Cunninghamia lanceolata (Lamb.) Hook. and M. chapensis exhibited peak SLA at 50–70% shading [20,29].”

“....consistent with PSII damage thresholds in Q. mongolica under 3% light [11].”

Comment 3:  "we" instead of "We".

Response 3: We appreciate this keen observation. "We" has been changed to lowercase "we" to align with mid-sentence syntax.

Revised Text:

"To resolve this light-limitation bottleneck, we propose a light-gradient acclimation cultivation strategy...":