Growth Rate and Leaf Functional Traits of Four Broad-Leaved Species Underplanted in Chinese Fir Plantations with Different Tree Density Levels
, Xiangqing Ma 1,3, Pengfei Wu 1,3 and Ming Li 1,3,*Round 1
Reviewer 1 Report
General comments
I have read the manuscript (Forest -15566695). Entitle: Growth rate and Leaf functional traits of four broad-leaved species underplanted in Chinese fir plantations with different stand density levels written by Rui Xu et. al., for publication of forest MDPI. In this study, the author investigates thinning treatment in an 11-year-old Chinese fir plantation and then underplants four broad-leaved species and analyzed the growth and leaf functional traits of those species as well as those traits are correlated with the stand characteristics. The author found that the growth characteristics and the root collar diameter of those species were significantly different among the stand level. On the other hand, the author also found that the leaf functional traits are also significantly different among the species in the sense of the leaf mass per unit area. The author found a good correlation between the growth characters and leaf functional traits showed that some leaf functional traits possibly predict diameter growth between the height growth.
The overall research is well conducted, and research is obvious application potential for the maximum forest productivity and light availability due to thinning as well as the availability of the light for the plant growth and development/ In this sense, the manuscript is much valuable. However, I found some points especially the flow of the text is not smooth and sometimes I found the shallow writing and lack of potential references, and lack of connection of story in different paragraphs especially in the introduction and discussion sections. In discussion, the author should be deal with the physiological traits in-depth and those should relate to the biological perspectives. I found the lack of potential and appropriate references to support the findings. The author should provide enough examples and further references to support their finding in the sense of morphology and physiological traits. Some of the references I mention below that help to improve this manuscript quality better than before. Overall after I evaluate this manuscript, I request the author for the “MAJOR REVISION” and, I request to authors for revision according to the rules of the journal and correct the bibliography.
Major suggestions
1) Abstract Issue: The author wrote the important finding in their abstract, but the text seems confusing. The author is unable to mention the ranking of the species based on the major traits of morphological and physiological responses under different thinning densities. Moreover, the Author should more clarify Line no. 33-34 where the author should clarify the correlation analysis between the growth characteristics and specific traits of physiological traits. The message is hidden here. Moreover, the author should focus the traits specific (morphological and leaf functional) with species-specific. The whole of the abstract should slightly change the tone of the presentation and should present the most important finding. Please remember that the abstract should more logical, short, concise, and informative. Your abstract should reflect your study and major findings while shortly observed by readers. Please make the necessary corrections and cross-check the word limit of your abstract.
2) Introduction: The author will describe the starting of the introduction with good background and well include the subject matter of climate change issue, precipitation issue, air temperature prediction in the near future which is appreciated. The overall introduction is well written however author should more focus and reference the literature which describes the morphological and physiological traits with sufficient examples. Please see Line no. 67-71. Here the author should give the information about the traits those traits describe the physiological and biochemical perspectives and connect to the plant biological perspective to better perform. Please refer and cite these two more articles further clearance and increase the strength of your introduction 1) https://doi.org/10.1016/j.scienta.2017.12.006 (Comparison of physiological and anatomical characteristics...) 2) https://doi.org/10.1016/j.scienta.2013.05.036 .Please mention that “physiological performance specially Pn and Gs increased due to the leaf thickness and increase the Chlorophyll content because those help to capture the better light and higher amount of light due to Chl. then higher possibility of Pn because of conversation of light energy change into the chemical energy”. The author should refer to such types of literature that describe the plant physiological traits and those connected to plant biology.
3) Ultimate goal and research hypothesis: The author should further improve the research hypothesis and objective in the last paragraph in the introduction (Line from 89-108). Furthermore, the author should present the add the goal of the study alone with the objective of the study. Accordingly, the author presents the hypothesis based on the main practical application of the study about and why study morphological and physiological traits in the different thinning densities. The author’s hypothesis should be clear here. The research objective obviously will be the selection of the species but to select the species what are the selection criteria of the species under the different density author should mention this objective in that direction. Overall, the last paragraph is satisfactory, but it needs to more information by conciseness and adding supplementary information related to the selection criteria of the species. Therefore, according to the main approach of the research author include and rephrase the research objective and somewhat the hypothesis and goal of the study. The hypothesis should be very clear in the introduction sections because, without appropriate literature, questions, or hypotheses in the introduction section the entire objective of the manuscript is unclear.
4) Discussion section (Ln. 288): Overall the discussion section included all the possible traits and their interpretation. In this research, the author found the possible correlation analyses between growth characters and leaf functional traits predict diameter growth better than height growth. Which is the main finding for further proof of the correlation aspects. It is very true that identifying the growth of the plant root collar diameter is a better indicator than the plant height. The author should cite these below literature in the discussion section in the text in relation to the “correlation aspect” clearly mention the information. The root diameter is the best indicator for the selection of the species and their resistance to the environmental stress condition. For this subject, the author gives references to these two potential kinds of literature because this article well describes the importance of root collar diameter/stem diameter for the selection of the species under the two different thinking density. (1) https://doi.org/10.1016/j.scitotenv.2021.146466 Title: Evaluation of morphological, physiological, and biochemical … (2) https://doi.org/10.1038/s42003-018-0256-7.
5) Conclusion section (Line no. 391): Please improve the conclusion section, which should be in good glow with include all necessary components of the study and does not repeat the result section. Conclusions should be present the future insight of the research based on your current finding and the strength of your results for the future research guideline.
The conclusion for me comes off as repetitive of the abstract or a summary of the results section. I would love to read striking points and take-home messages that will linger in the readers’ minds. What is the novelty, how does the study elucidate some questions along this field, and the contributions the paper may offer to the scientific community?
6) Reference: (Line no. 416): lease double-check the citations, their style, spell check, and other grammatical errors. moreover, I request to authors for revision throughout the manuscript according to the journal rules.
Good Luck !
Author Response
Responses to Reviewer #1
General comments
I have read the manuscript (Forest -15566695). Entitle: Growth rate and Leaf functional traits of four broad-leaved species underplanted in Chinese fir plantations with different stand density levels written by Rui Xu et. al., for publication of forest MDPI. In this study, the author investigates thinning treatment in an 11-year-old Chinese fir plantation and then underplants four broad-leaved species and analyzed the growth and leaf functional traits of those species as well as those traits are correlated with the stand characteristics. The author found that the growth characteristics and the root collar diameter of those species were significantly different among the stand level. On the other hand, the author also found that the leaf functional traits are also significantly different among the species in the sense of the leaf mass per unit area. The author found a good correlation between the growth characters and leaf functional traits showed that some leaf functional traits possibly predict diameter growth between the height growth.
Response: Thank you for the compliment!
The overall research is well conducted, and research is obvious application potential for the maximum forest productivity and light availability due to thinning as well as the availability of the light for the plant growth and development/ In this sense, the manuscript is much valuable. However, I found some points especially the flow of the text is not smooth and sometimes I found the shallow writing and lack of potential references, and lack of connection of story in different paragraphs especially in the introduction and discussion sections. In discussion, the author should be deal with the physiological traits in-depth and those should relate to the biological perspectives. I found the lack of potential and appropriate references to support the findings. The author should provide enough examples and further references to support their finding in the sense of morphology and physiological traits. Some of the references I mention below that help to improve this manuscript quality better than before. Overall after I evaluate this manuscript, I request the author for the “MAJOR REVISION” and, I request to authors for revision according to the rules of the journal and correct the bibliography.
Response: Thank you very much for your constructive comments. We addressed the concerns you raised.
Major suggestions
1) Abstract Issue: The author wrote the important finding in their abstract, but the text seems confusing. The author is unable to mention the ranking of the species based on the major traits of morphological and physiological responses under different thinning densities. Moreover, the Author should more clarify Line no. 33-34 where the author should clarify the correlation analysis between the growth characteristics and specific traits of physiological traits. The message is hidden here. Moreover, the author should focus the traits specific (morphological and leaf functional) with species-specific. The whole of the abstract should slightly change the tone of the presentation and should present the most important finding. Please remember that the abstract should more logical, short, concise, and informative. Your abstract should reflect your study and major findings while shortly observed by readers. Please make the necessary corrections and cross-check the word limit of your abstract.
Response: We revised the abstract taking into account the valuable comments made by the reviewer (see the new abstract).
2) Introduction: The author will describe the starting of the introduction with good background and well include the subject matter of climate change issue, precipitation issue, air temperature prediction in the near future which is appreciated. The overall introduction is well written however author should more focus and reference the literature which describes the morphological and physiological traits with sufficient examples. Please see Line no. 67-71. Here the author should give the information about the traits those traits describe the physiological and biochemical perspectives and connect to the plant biological perspective to better perform. Please refer and cite these two more articles further clearance and increase the strength of your introduction 1) https://doi.org/10.1016/j.scienta.2017.12.006 (Comparison of physiological and anatomical characteristics...) 2) https://doi.org/10.1016/j.scienta.2013.05.036 .Please mention that “physiological performance specially Pn and Gs increased due to the leaf thickness and increase the Chlorophyll content because those help to capture the better light and higher amount of light due to Chl. then higher possibility of Pn because of conversation of light energy change into the chemical energy”. The author should refer to such types of literature that describe the plant physiological traits and those connected to plant biology.
Response: Thank you for the valuable suggestion! Comments suggested by the reviewer are sufficiently addressed in the introduction section (see L81-84)
3) Ultimate goal and research hypothesis: The author should further improve the research hypothesis and objective in the last paragraph in the introduction (Line from 89-108). Furthermore, the author should present the add the goal of the study alone with the objective of the study. Accordingly, the author presents the hypothesis based on the main practical application of the study about and why study morphological and physiological traits in the different thinning densities. The author’s hypothesis should be clear here. The research objective obviously will be the selection of the species but to select the species what are the selection criteria of the species under the different density author should mention this objective in that direction. Overall, the last paragraph is satisfactory, but it needs to more information by conciseness and adding supplementary information related to the selection criteria of the species. Therefore, according to the main approach of the research author include and rephrase the research objective and somewhat the hypothesis and goal of the study. The hypothesis should be very clear in the introduction sections because, without appropriate literature, questions, or hypotheses in the introduction section the entire objective of the manuscript is unclear.
Response: Thank you for the constructive comments! We revised the hypothesis and provide specific objectives of the study at the end of the introduction section (see L114-118 and L126-131).
4) Discussion section (Ln. 288): Overall the discussion section included all the possible traits and their interpretation. In this research, the author found the possible correlation analyses between growth characters and leaf functional traits predict diameter growth better than height growth. Which is the main finding for further proof of the correlation aspects. It is very true that identifying the growth of the plant root collar diameter is a better indicator than the plant height. The author should cite these below literature in the discussion section in the text in relation to the “correlation aspect” clearly mention the information. The root diameter is the best indicator for the selection of the species and their resistance to the environmental stress condition. For this subject, the author gives references to these two potential kinds of literature because this article well describes the importance of root collar diameter/stem diameter for the selection of the species under the two different thinking density. (1) https://doi.org/10.1016/j.scitotenv.2021.146466 Title: Evaluation of morphological, physiological, and biochemical … (2) https://doi.org/10.1038/s42003-018-0256-7.
Response: Thank you for the valuable suggestions, which are addressed in the discussion section of the revised manuscript (see L424-429 and L432-433).
5) Conclusion section (Line no. 391): Please improve the conclusion section, which should be in good glow with include all necessary components of the study and does not repeat the result section. Conclusions should be present the future insight of the research based on your current finding and the strength of your results for the future research guideline. The conclusion for me comes off as repetitive of the abstract or a summary of the results section. I would love to read striking points and take-home messages that will linger in the readers’ minds. What is the novelty, how does the study elucidate some questions along this field, and the contributions the paper may offer to the scientific community?
Response: Thank you for the valuable suggestion. We have now modified the conclusion part as per the suggestion of the reviewer (see L438-453).
6) Reference: (Line no. 416): lease double-check the citations, their style, spell check, and other grammatical errors. moreover, I request to authors for revision throughout the manuscript according to the journal rules.
Response: We have carefully checked the reference list and corrected all errors (see the revised reference list).
Author Response File: 
Author Response.docx
Reviewer 2 Report
The principle problem with this analysis is that it ignores the well-known effects of shade on leaf morphology and on seedling dimensions Many of the results can simply be ascribed to differences between sun and shade leaves, which is both a function of quantity and quality of light. Shade leaves are thinner, have higher specific leaf areas, and may have more N per gram due to higher concentration of chlorophyll. It is also well known that seedling height is responsive to light up to a point. These various anatomical and morphological traits have been associated with broad categories of shade tolerance. These connections need to be made in the introduction and in the discussion.
Line 51: Thinning does not in general increase the productivity, or more suitably, production. Productivity is a property of the site.
Line 56: What is virtuous cycle?
Line 59: More details are needed. Which models, and what downsides of monocultures. Just citing a reference is insufficient.
Line 63: What are you restoring? What was the original species composition?
Line 100: What support do you have that these traits have any functional value for these species? Have these traits been measured for these species in other studies?
Line 122: Traditionally trees/ha not plants
Line 125: What are the silvics of four underplanted species?
Line 154: What instrument was used to measure canopy properties?
Line 156: Do you mean simply gap fraction?
Line 178: What is DCA?
Line 254: Use tree density. Stand density is similar to growing stock or basal area per hectare.
Line 313: “flakes”?
Line 329 to end of paragraph. Any data on how these traits have reacted to shade from other studies?
Line 391: Conclusions section – Seems that the only reliable conclusion is that shade limits seedling growth, which is already well known.
Author Response
Responses to Reviewer #2
The principle problem with this analysis is that it ignores the well-known effects of shade on leaf morphology and on seedling dimensions. Many of the results can simply be ascribed to differences between sun and shade leaves, which is both a function of quantity and quality of light. Shade leaves are thinner, have higher specific leaf areas, and may have more N per gram due to higher concentration of chlorophyll. It is also well known that seedling height is responsive to light up to a point. These various anatomical and morphological traits have been associated with broad categories of shade tolerance. These connections need to be made in the introduction and in the discussion.
Response: Thank you for the suggestion. We addressed this concern in the introduction and discussion sections (see L86-106; L338-344 and L362-370).
Line 51: Thinning does not in general increase the productivity, or more suitably, production. Productivity is a property of the site.
Response: Thank you for the comment. We have now change productivity by production (see L52).
Line 56: What is virtuous cycle?
Response: thank you for pointing our error. We mean the vicious cycle of artificial forest establishment. We corrected this sentence in the revised version (see L58).
Line 59: More details are needed. Which models, and what downsides of monocultures. Just citing a reference is insufficient.
Response: we refer to mixed-species planting model, which we mentioned in the preceding sentences. We added some of the downsides of monocultures in the revised manuscript (see L60-62).
Line 63: What are you restoring? What was the original species composition?
Response: We are aiming to restore conifer-broadleaved mixed-species forest by converting pure monoculture of Chinese fir by planting appropriate broad-leaved species. We clarified this issue in the revised manuscript (see L67-68)
Line 100: What support do you have that these traits have any functional value for these species? Have these traits been measured for these species in other studies?
Response: several studies have shown that leaf functional traits are good predictors of growth and associated with light availability and enhanced photosynthesis rate. However we do not know if any of these functional traits can be used to predict growth of these species as there are no studies that demonstrate this. In fact, this study is the first to use leaf functional traits of these species to evaluate growth performance. We revised the functional values of leaf traits in the revised version (see L81-106).
Line 122: Traditionally trees/ha not plants
Response: Thank you for the suggestion. We have now changed plants to trees throughout the manuscript
Line 125: What are the silvics of four underplanted species?
Response: the species have some degree of shade tolerance, which we mentioned in L162
Line 154: What instrument was used to measure canopy properties?
Response. We used LAI-2200C canopy analyzer (LI-COR Biosciences Ltd, Cambridge, UK) for measuring leaf area index. We added this sentence in the revised version (see L176-177)
Line 156: Do you mean simply gap fraction?
Response: No, we measured the leaf area index and non-intercepted scattering using LI-COR
Line 178: What is DCA?
Response: DCA stands for Detrended Canonical Analysis. We have now written in full in the revised version (see L197).
Line 254: Use tree density. Stand density is similar to growing stock or basal area per hectare.
Response: Thank you for the suggestion. We changed stand density with tree density throughout the manuscript.
Line 313: “flakes”?
Response: Sorry for the error. We delete the word in the revised version (see L346).
Line 329 to end of paragraph. Any data on how these traits have reacted to shade from other studies?
Response: We added an additional explanation in relation to shade-tolerance based on previous studies (see 338-344 and L362-370).
Line 391: Conclusions section – Seems that the only reliable conclusion is that shade limits seedling growth, which is already well known.
Response: Our aim is to identify suitable species for under planting using different tree density. Therefore, the conclusion based on our findings are not limited to “shade limits seedling growth”. We revised the conclusion to lift out important implications of the study (see L438-453)
Author Response File: Author Response.docx
Round 2
Reviewer 1 Report
Dear Author
I have read the revised manuscript (Forest-1556695). Entitle: Growth rate and Leaf functional traits of four broad-leaved species underplanted in Chinese fir plantations with different stand density levels for publication of Forest MDPI. This is the second submission made by the author. The author addressed all the questions and suggestions that I raised the issue in the review of the original manuscript. I satisfy the author’s revisions throughout the paper. Especially author improved the introduction and discussion section very well inflow. The abstract issue is also solved by the author. Now, this manuscript improved the flow of writing, which was comparatively shallow in the original version but in this revised copy author addressed all the quarries and suggestions very well. Before accepting this manuscript, I wish to request the author for the manuscript check by the native English, especially the author should be sure of the accuracy of English grammar or spell check and sentences structures. I request this manuscript is currently in “Minor Revision”. This manuscript has not found the technical issue but is only pending for the English. Thank you.
Author Response
Responses to reviewer #1
I have read the revised manuscript (Forest-1556695). Entitle: Growth rate and Leaf functional traits of four broad-leaved species underplanted in Chinese fir plantations with different stand density levels for publication of Forest MDPI. This is the second submission made by the author. The author addressed all the questions and suggestions that I raised the issue in the review of the original manuscript. I satisfy the author’s revisions throughout the paper. Especially author improved the introduction and discussion section very well inflow. The abstract issue is also solved by the author. Now, this manuscript improved the flow of writing, which was comparatively shallow in the original version but in this revised copy author addressed all the quarries and suggestions very well. Before accepting this manuscript, I wish to request the author for the manuscript check by the native English, especially the author should be sure of the accuracy of English grammar or spell check and sentences structures. I request this manuscript is currently in “Minor Revision”. This manuscript has not found the technical issue but is only pending for the English. Thank you.
Response: Thank you very much for the compliment! The language is thoroughly checked by Native English speaking colleague.
Author Response File: Author Response.docx
Reviewer 2 Report
There are still serious problems with this manuscript. It is clear that the authors have not conducted the research into shading effects on leaf anatomy. It also appears that the authors have misrepresented the literature they cite in support of some of their arguments nor have they critically reviewed the literature in relation to their study. Any basic woody physiology textbook will list the differences between sun and shade leaves. For instance, in The Physiology of Woody Plants by Kozlowski and Pallardy (1997) states that leaves grown in shade are thinner, have greater specific leaf area, and have lower chlorophyll content per unit leaf area. Even the newly added reference (no. 25) states that leaves grown in the lower light levels have higher specific leaf areas than leaves grown in higher light levels. The authors on line 87 state just the opposite. Other traits are just transformations of other traits such as leaf density and leaf mass per unit area. Are these traits are or are just adaptations? I would suggest that the range of modifications of these attributes are the traits not the values after adaptation.
I noticed that stand density was still used in a large portion of the manuscript. Stand density is a measure of competition or growing stock. Table 3 need units.
Author Response
Responses to reviewer #2
There are still serious problems with this manuscript. It is clear that the authors have not conducted the research into shading effects on leaf anatomy. It also appears that the authors have misrepresented the literature they cite in support of some of their arguments nor have they critically reviewed the literature in relation to their study. Any basic woody physiology textbook will list the differences between sun and shade leaves. For instance, in The Physiology of Woody Plants by Kozlowski and Pallardy (1997) states that leaves grown in shade are thinner, have greater specific leaf area, and have lower chlorophyll content per unit leaf area. Even the newly added reference (no. 25) states that leaves grown in the lower light levels have higher specific leaf areas than leaves grown in higher light levels. The authors on line 87 state just the opposite. Other traits are just transformations of other traits such as leaf density and leaf mass per unit area. Are these traits are or are just adaptations? I would suggest that the range of modifications of these attributes are the traits not the values after adaptation.
Response; Thank you for pointing out the error that we made. We have now checked the reference and corrected “….low SLA into high SLA”. As to other traits, studies have shown their adaptive values, such as tolerance to herbivory by species with high leaf tissue density (Li et al., 2020). Leaf mass per unit area has also been shown to be associated with shading; i.e. reduction in leaf mass per unit area with increasing shading (Rosati et al. 2000). Thus, leaf mass per unit area is considered a species-specific estimate of long-term light conditions. In addition, high leaf mass per area was found to be associated with root collar diameter growth under drought condition (Bhusal et al. 2021). In fact, our thinning experiment creates differences in light availability (extent of shading); thus it is implicit that the study involved different degree of shading.
I noticed that stand density was still used in a large portion of the manuscript. Stand density is a measure of competition or growing stock. Table 3 need units.
Response: We thoroughly checked the manuscript and corrected it. We also provided the units in Table 3.
Author Response File: Author Response.docx
