Drought Changes the Trade-Off Strategy of Root and Arbuscular Mycorrhizal Fungi Growth in a Subtropical Chinese Fir Plantation
, Cong Cao 1, Xiaojie Li 1, Xiaoling Xiong 1, Weisheng Lin 1,3,*, Zhijie Yang 1,2, Guangshui Chen 1,2, Yusheng Yang 1,2,3 and Jinsheng Xie 1,2
Round 1
Reviewer 1 Report
The manuscript entitled "Drought Changes the Trade-off strategy of Root and Arbuscular Mycorrhizal Fungi Growth in a Subtropical Chinese Fir Plantation" shows the impacts of drought stress on Chinese fir in the presence of AMF. The topic is relevant, and the subject is very interesting. The authors did a lot of work. The manuscript has the potential to be accepted. However, there is still some major issues need to be addressed before the paper could be accepted as follows:
Comments
Lines 34-35: I would suggest changing the keywords.
Lines 71-73: Rephrase this sentence.
Line 155: Add a reference https://doi.org/10.1016/j.envpol.2022.120356
Lines 176: Add a reference https://doi.org/10.1007/s42729-021-00727-2
Lines 177-183: The authors should give more details.
Lines 179, 183: Follow the journal's reference writing instructions.
In the results, authors should add one sentence at the end of each paragraph to conclude the whole paragraph to make it easy for the reader.
Figure 3: What is CT and PE, please provide the full name in the figure caption.
Figure 5b: Spore 20 g-1 soil.
Lines 315-317: not clear.
Lines 338-339: How???
Kind Regards.
Author Response
Reviewer #1: The manuscript entitled "Drought Changes the Trade-off strategy of Root and Arbuscular Mycorrhizal Fungi Growth in a Subtropical Chinese Fir Plantation" shows the impacts of drought stress on Chinese fir in the presence of AMF. The topic is relevant, and the subject is very interesting. The authors did a lot of work. The manuscript has the potential to be accepted. However, there is still some major issues need to be addressed before the paper could be accepted as follows:
Response: We appreciate the reviewer’s positive comments and constructive suggestions on our manuscript. We have made great corrections and revisions according to the reviewer’s suggestion. We believe the revised manuscript could meet the request for publication in Forests journal.
Lines 34-35: I would suggest changing the keywords.
Response: Done. We have changed the keywords.
Lines 71-73: Rephrase this sentence.
Response: Done, please see Line 76-79.
Line 155: Add a reference https://doi.org/10.1016/j.envpol.2022.120356
Response: Done, please see Line 171.
Lines 176: Add a reference https://doi.org/10.1007/s42729-021-00727-2
Response: Done, please see Line 192.
Lines 177-183: The authors should give more details.
Response: Done, please see Line 194-222.
Lines 179, 183: Follow the journal's reference writing instructions.
Response: Done, please see Line 217,222.
In the results, authors should add one sentence at the end of each paragraph to conclude the whole paragraph to make it easy for the reader.
Response: Agree. We have done this according to reviewer’s suggestion.
Figure 3: What is CT and PE, please provide the full name in the figure caption.
Response: Done, please see figure captions.
Figure 5b: Spore 20 g-1 soil.
Response: Done, please see figure 5b.
Lines 315-317: not clear.
Response: Apologizes for our unclear writing. We have rewritten this sentence. Please see line 360-362.
Lines 338-339: How???
Response: Because AMF is an aerobic fungus which is has high sensitivity to water conditions changes.
Reviewer 2 Report
The manuscript by Dong et al described the research that study the effects of drought on trade-off strategy of root and AMF in Chinese Fir plantation. Data were collected from both winter and summer to give a better view of the result. The interpretation of data is very clear and make sense. Manuscripts is well written with a clear structure. Overall, this is a decent paper that merit the publication. I do not have further comment.
Author Response
Reviewer #2:
The manuscript by Dong et al described the research that study the effects of drought on trade-off strategy of root and AMF in Chinese Fir plantation. Data were collected from both winter and summer to give a better view of the result. The interpretation of data is very clear and make sense. Manuscripts is well written with a clear structure. Overall, this is a decent paper that merit the publication. I do not have further comment.
Response: We appreciate the reviewer’s positive comments and suggestions.
Reviewer 3 Report
Dong et al. present an interesting study regarding the effects of precipitation exclusion and seasonality on root characteristics of Chinese fir (Cunninghamia lanceolata), along with associated arbuscular mycorrhizal (AM) fungal characteristics, such as hyphal densities, AM fungal infection of C. lanceolata roots, spore densities, and glomalin production. I believe this data is timely in the face of current anthropogenic climate changes, though there are several concerns I would like to see addressed before this paper can be accepted for publication. My overall concern has to do with the massive amount of data collected and presented. While more data is often a positive, it can be to the extent of losing focus of the key points and take-aways of the experimental results. As written, there is clearly a relationship between the roots and the AM fungal dynamics, though they are not unified or connected in any clear way. This is especially true in the results. There are far too many figures, some of which could likely be formatted into tables, or included as supplemental information. My second major concern is the lack of research motivation/justification in the Introduction. Specifically, I find myself wondering why this work is important, and how it fills current knowledge gaps or improves upon previous work. Clarification and simplification in these areas should make for a much cleaner manuscript.
Introduction
Overall, the introduction does a good job highlighting previous literature in the field, serving as relevant background information to the study being presented. However, I find myself searching for further justification serving as the motivation driving research. This is briefly stated in L 88-91, though this section only references AM fungal colonization/infection. What current knowledge gaps are being addressed through the measurements of root characteristics, glomalin production, and the other variables measured? You should re-visit these thoughts at the end of the introduction, while also emphasizing what you hope this research will contribute as far as our broader understandings of the field or system.
L 41-43 Introduce arbuscular mycorrhizal fungi prior to the sentence beginning in L 43. As written, the mention of mycorrhizal fungi is very sudden. Perhaps this can be alleviated through phrasing, such as, “One such plant-microbial interaction is the plant-mycorrhizal symbiosis.” Then follow with the sentence currently in L43-45.
L 67-68 Does “underground” need to be specified here? All previous information and references have discussed implications for belowground root systems (as opposed to the much rarer aerial roots).
L 69-71 “Grow better” is rather subjective and requires a comparison. Please specify (i.e., improved biomass production, fitness, etc.).
L 92-93 Delete “areas” and change “accounts” to singular form.
L 94 “plays”, instead of “playing”.
L 95-97 This sentence is difficult to follow. How does drought frequently lead to extreme climates? Climate is often defined as weather patterns of 30+ years.
L 97-98 Is C. lanceolata well known for its drought tolerance/resistance? This reads as such but is preceded by a sentence implying drought is dramatically reducing productivity of C. lanceolata plantations. The two seem to contradict one another.
L 101-102 Consider re-wording; this is a very anthropomorphized view.
L 101-103 Please give reasoning, preferably citations, giving reason to your hypotheses.
Materials and Methods
L 115-117 As written, it reads as if this refers to only the year of the experiment. Please clarify that this represents annual precipitation averages.
L 118-119 Check the wording at the end of the sentence. I recommend changing to “clear-cut and burned” or “Castanopsis kawakamii was removed by clear-cutting and burning.”
L 117 Is “red soil” a scientific soil classification? Typically, soils of particular regions are classified by standardized taxonomy or soil series. This would provide readers with further insight into parent material, minerals, fertility, etc.
L 139 Check spacing for “top10cm”.
L 144 What other indices are being referred to here?
L 192-193 Please include proper citation of the R package that performs the random forest analysis.
L 193 “indices”, instead of “indexes”
Results, Figures, and Tables
Overall, there are far too many figures. It makes it unclear as to what the major take-aways are from this experiment. I strongly suggest re-visiting the results, clearly defining which components are the most critical to the overall ecological/biological story you are attempting to convey. From here, place the most important information into figures, and non-significant results (or those that are secondary to key findings) into tables. This will greatly improve the flow and clarity of the manuscript.
Figure 2 Please indicate in the legend which color represents which treatment. This will improve clarity and readability.
Figure 3 If no significant differences were detected, consider placing in a table.
Figure 4-6 Be sure to indicate in the legend at what p-value levels significance was assessed at (ex. P ≤ 0.05).
Figure 8 Without understanding what a random forest model is or does, it is difficult to understand the graphic as shown. This analysis does seem to produce results redundant to those that have already been displayed in previous figures; however, if the authors decide to move forward with this figure and include it in subsequent manuscript drafts, please include information regarding the meaning the x-axis, and what it means when values are above or below zero.
Table 2 In the table legend, please indicate the meaning of bold and italicized fonts. I understand that it likely reflects significance and marginal significance, respectively, but this should be clear from reading the legend.
L 227-229 Check spacing at the beginning of the sentence.
Discussion
L 332-334 Through what mechanism(s) or pathway(s) do you suggest C. lanceolata increases AM fungal characteristics? Are the trees or the fungi the drivers of the measured AM fungal traits?
Conclusions
The conclusions should incorporate broader-scale implications for this research, outside of the scope of just C. lanceolata plantations. What does this mean for broader plant-microbial interactions under future climate change scenarios?
Author Response
Reviewer #3:
Dong et al. present an interesting study regarding the effects of precipitation exclusion and seasonality on root characteristics of Chinese fir (Cunninghamia lanceolata), along with associated arbuscular mycorrhizal (AM) fungal characteristics, such as hyphal densities, AM fungal infection of C. lanceolata roots, spore densities, and glomalin production. I believe this data is timely in the face of current anthropogenic climate changes, though there are several concerns I would like to see addressed before this paper can be accepted for publication. My overall concern has to do with the massive amount of data collected and presented. While more data is often a positive, it can be to the extent of losing focus of the key points and take-aways of the experimental results. As written, there is clearly a relationship between the roots and the AM fungal dynamics, though they are not unified or connected in any clear way. This is especially true in the results. There are far too many figures, some of which could likely be formatted into tables, or included as supplemental information. My second major concern is the lack of research motivation/justification in the Introduction. Specifically, I find myself wondering why this work is important, and how it fills current knowledge gaps or improves upon previous work. Clarification and simplification in these areas should make for a much cleaner manuscript.
Response: We appreciate the reviewer’s comments and suggestions. We've tried to turn images that don't have significant differences into tables. And we supplement the motivation and meaning of the research, please see Line 97-102.
For the reviewer’s concerns about our study filling the knowledge gaps, to the best of our knowledge, we think it is quite unclear how tree species will respond to future drought events like seasonal drought or interannual drought. Especially, our studied tree species Chinese fir is widely distributed in southern China. There are more than 32% of plantation forests are dominated by coniferous species such as Chinese fir (Cunninghamia lanceolata) in China which plays an important role in forestry production and as a carbon sink. Therefore, it is important to address how Chinese fir will respond to drought. We urgently to know whether Chinese fir can adapt to drought events in ways like changing the strategy of carbon investment to root or AMF.
Introduction
Overall, the introduction does a good job highlighting previous literature in the field, serving as relevant background information to the study being presented. However, I find myself searching for further justification serving as the motivation driving research. This is briefly stated in L 88-91, though this section only references AM fungal colonization/infection. What current knowledge gaps are being addressed through the measurements of root characteristics, glomalin production, and the other variables measured? You should re-visit these thoughts at the end of the introduction, while also emphasizing what you hope this research will contribute as far as our broader understandings of the field or system.
Response: Agree. In the last paragraph of the introduction, we re-express the significance and necessity of the study. Please see Line 99-103.
L 41-43 Introduce arbuscular mycorrhizal fungi prior to the sentence beginning in L 43. As written, the mention of mycorrhizal fungi is very sudden. Perhaps this can be alleviated through phrasing, such as, “One such plant-microbial interaction is the plant-mycorrhizal symbiosis.” Then follow with the sentence currently in L43-45.
Response: Agree. We reintroduced AMF in L43-48. Arbuscular mycorrhizal fungi (AMF) is a fungus that can form a mutually-beneficial relationship with the roots of approximately 80% of terrestrial vascular plants, significantly improving plant nutrient uptake and resistance to several abiotic stress factors.” before introducing nutrient uptake pathways in plants.
L 67-68 Does “underground” need to be specified here? All previous information and references have discussed implications for belowground root systems (as opposed to the much rarer aerial roots).
Response: Agree. We've deleted it, the whole study is underground roots and not aerial roots.
L 69-71 “Grow better” is rather subjective and requires a comparison. Please specify (i.e., improved biomass production, fitness, etc.).
Response: Agree. We've rewritten this as “Many studies have shown that plant mycorrhizal symbiosis is one of the most effective ways to withstand stress, causing improvement in plant growth.”
L 92-93 Delete “areas” and change “accounts” to singular form.
Response: Done, please see Line 102.
L 94 “plays”, instead of “playing”.
Response: Done, please see Line 104.
L 95-97 This sentence is difficult to follow. How does drought frequently lead to extreme climates? Climate is often defined as weather patterns of 30+ years.
Response: Apologizes for our unclear presentation. We would like to say the occurrence of extreme rainfall events and changes in rainfall distribution patterns have frequently led to extreme climates like drought in subtropics. We have corrected this. Please see L107-109.
L 97-98 Is C. lanceolata well known for its drought tolerance/resistance? This reads as such but is preceded by a sentence implying drought is dramatically reducing productivity of C. lanceolata plantations. The two seem to contradict one another.
Response: How roots regulate ecosystem productivity is one of the "bottlenecks" and most uncertain factors in forest ecosystem research. It is not clear whether subsurface allocation also increases fine root or AMF abundance or if one is preferred over the other. C. lanceolata plays an important role in subtropical forest ecosystems in China. However, there are few studies on how Chinese fir respond to drought stress.
L 101-102 Consider re-wording; this is a very anthropomorphized view.
Response: Done. We have tried to re-wording this hypothesis according to the reviewer’s suggestion.
L 101-103 Please give reasoning, preferably citations, giving reason to your hypotheses.
Response: Agree. We've added references for hypothesis 1 and reasons for hypothesis 2.
Materials and Methods
L 115-117 As written, it reads as if this refers to only the year of the experiment. Please clarify that this represents annual precipitation averages.
Response: Done.
L 118-119 Check the wording at the end of the sentence. I recommend changing to “clear-cut and burned” or “Castanopsis kawakamii was removed by clear-cutting and burning.”
Response: Done. Please see Line 134.
L 117 Is “red soil” a scientific soil classification? Typically, soils of particular regions are classified by standardized taxonomy or soil series. This would provide readers with further insight into parent material, minerals, fertility, etc.
Response: Done. The soil is classified as red soil derived from crystalline granite in Chinese soil classification, equivalent to Oxisol in the USDA Soil Taxonomy.
L 139 Check spacing for “top10cm”.
Response: Done. Please see Line 154.
L 144 What other indices are being referred to here?
Response: The other indices are moisture, pH, DON, AP, MBP, NH4+-N, NO3--N
L 192-193 Please include proper citation of the R package that performs the random forest analysis.
Response: Done.
L 193 “indices”, instead of “indexes”
Response: Done. Please see Line 232.
Results, Figures, and Tables
Overall, there are far too many figures. It makes it unclear as to what the major take-aways are from this experiment. I strongly suggest re-visiting the results, clearly defining which components are the most critical to the overall ecological/biological story you are attempting to convey. From here, place the most important information into figures, and non-significant results (or those that are secondary to key findings) into tables. This will greatly improve the flow and clarity of the manuscript.
Response: We appreciate the reviewer’s comments and suggestions. We have reorganized some of the results into table.
Figure 2 Please indicate in the legend which color represents which treatment. This will improve clarity and readability.
Response: Done. Please see Figure 2.
Figure 3 If no significant differences were detected, consider placing in a table.
Response: Agree. We have changed the picture to a table.
Figure 4-6 Be sure to indicate in the legend at what p-value levels significance was assessed at (ex. P ≤ 0.05).
Response: Thanks for the reviewer’s kind suggestion. We have checked throughout.
Figure 8 Without understanding what a random forest model is or does, it is difficult to understand the graphic as shown. This analysis does seem to produce results redundant to those that have already been displayed in previous figures; however, if the authors decide to move forward with this figure and include it in subsequent manuscript drafts, please include information regarding the meaning the x-axis, and what it means when values are above or below zero.
Response: Thanks for the reviewer’s comments. We have made carefully thought about it. We have decided to remove this figure 8. Actually, it is similar to the Fig. 7 and Fig. 9.
Table 2 In the table legend, please indicate the meaning of bold and italicized fonts. I understand that it likely reflects significance and marginal significance, respectively, but this should be clear from reading the legend.
Response: Done. Bold type means significance.
L 227-229 Check spacing at the beginning of the sentence.
Response: Done. Please see Line 268.
L 332-334 Through what mechanism(s) or pathway(s) do you suggest C. lanceolata increases AM fungal characteristics? Are the trees or the fungi the drivers of the measured AM fungal traits?
Response: The hyphal network formed by the AM fungal enhances the access of roots to a large soil surface area, causing improvement in plant growth. Under drought conditions, trees can adapt to environmental stress by investing in carbon sources in their roots or mycorrhizal fungi, which help them obtain nutrients and water.
Conclusions
The conclusions should incorporate broader-scale implications for this research, outside of the scope of just C. lanceolata plantations. What does this mean for broader plant-microbial interactions under future climate change scenarios?
Response: Thanks for the reviewer’s comments. We have rephrased our conclusions. Please see Line 418-426. Because Chinese fir accounts for 32% of the plantation forests in southern China, which should have great representation and could be incorporated into broader-scale implications.
Reviewer 4 Report
In this study, authors have studied the consequences of precipitation manipulation on plant root, AMF and soil. The study is interesting and I enjoyed reading. Thank you very much. While I appreciate authors efforts for investigating different important variables in the field level, there were quite a few points should be carefully addressed. Fundamentally, the experimental set up affects at least three players in context, plant, AMF and soil. It should be clearly addressed if there was plant really showed drought stress if authors want to address in title if the study can tell facts about plant drought responding strategy. Also throughout the manuscript, authors have over-interpreted some results. Postulations should be differentiated from result interpretation. I think overall study is meaningful and interesting, but there are many points to be improved with additional analyses as well as checking for interpretation.
Abstract
Overall, I felt abstract is bit hard to understand. I would recommend to improve it.
L25-26 It is difficult to understand what is the difference between hyphae density and infection rate. This should be clearly addressed before this statement. Otherwise, it is hard to understand.
L28-29 It is hard to understand the meaning of this result for the general context. Authors should explain why this was measured and what is the meaning.
L30-33 I am not sure authors can really claim this based on their results. The supports are rather to be weak to claim that. I think main conclusion should be reframed.
Introduction
L41-43 community composition of plants… above and below ground -> It is hard to understand the meaning of sentence. Are you talking that there are below ground plant community?
L43-46 The logic for linking arbuscular mycorrhiza and drought is weak, what is the context for introducing arbuscular mycorrhiza here? Since the main focus of manuscript is about this, should be addressed in better way.
L95-97 I would recommend authors to introduce more about the drought effect on their main model system (Chinese fir). Although it is the main, the description of drought stress or damage is bit simple.
L101-102 I don’t think authors have really measured carbon. Hypothesis should be carefully addressed and it should be matching with what author really measured and interpret. Assuming that putting more carbon will result in increase of AMF infection or growth is bit naïve. As AMF also can store the carbon as vesicle with lower infection rate or growth. It is hard to be directly interpreted.
Materials and Methods
One of the most important fact is that author’s hypotheses are about drought, but actual application was 50% precipitation control. I think it is better to provide some information about how much drought it can actually make with the treatment. For example, if the plant really showed drought response or not. Because if the precipitation is already more than enough for the plant (as different species requires different water amount for thriving), then the experimental setup that author is simply comparing over-watered vs normal or normal vs normal, not normal vs drought as authors intended. Also provide some information about the system with previous studies (or literatures).
Figure1 legend is not fully explaining panel A
L137 Two years of drought.. -> I am not sure the description is carefully addressed. Please rephrase the sentence for reflecting the experiment.
L178 Please describe the measurement of hyphal density to be soil hyphal density to avoid confusion
Results
The term exclusion is misleading. I think authors have used this term for entire manuscript, even in materials and methods (description related with plot design and figure 1). What authors actually did was not complete blocking of precipitation. The term should be changed for appropriate alternatives. Precipitation control or reduced precipitation (by 50%).
L224 Furthermore, there were significant interactions between season and treatment (P=0.048; Table 2), indicating that precipitation exclusion reduced the seasonal difference in root diameter. -> This is already explained by previous sentence that there is interaction effect. Authors can simply say the interaction effect was confirmed. Otherwise, it is just a redundant description.
L280-281 I think what authors did was revealing correlation, not the causality testing. It is hard to say one factor “affected” the other factor in this case. The interpretation for this and throughout discussion should be re-phrased.
Discussion
It is important to provide the support that there was “drought” taken place, as that is a base for whole interpretation. It will be nice to show the data that plants have experienced drought stress.
L333-334 The interpretation is bit inappropriate as authors cannot know if the phenomenon was caused by plant or fungi. Consequently, the following interpretation about strategy is also carefully addressed. Currently, many sentences in the manuscript are bit exaggerated or over-interpreting the results. Authors should check throughout manuscript that what can be addressed, and in which degree they can say or “postulate”.
L351-352 The soil characteristic is associated with AMF, but could this be linked with drought treatment in the study? It is hard to understand if the soil characteristic analyses to compare control vs treatment was conducted or not in this study. Simply, there would be at least three players in the context, Soil, plant, and AMF. I think the study still could not answer for the causality or strategy of plant for drought. Authors should first compare the treatment effect on soil characteristics to really discuss some changes.
Conclusion
L360 This improved the Chinese fir roots’ ability to absorb… -> Authors cannot say “improved” as there was no support for that. Should be noted as “might have improved, or postulated to be improved”.
L362 Also this interpretation is bit misleading. Since authors cannot know if the decision maker of the observation was plant or AMF or soil, it is hard to simply conclude there is “a change in investment”. During my review of manuscript, I could see many cases of this over-interpretation. Authors should just say what can be told by the correlation analyses. There is no causality can be called, except for the very direction comparison of variables between treatment and control.
L364 Chinese fir will -> Chinese fir might
L366 mycorrhizae will increase -> mycorrhizae might increase
L367 Drought will enhance -> We postulate that drought might enhance
Author Response
Reviewer #4
In this study, authors have studied the consequences of precipitation manipulation on plant root, AMF and soil. The study is interesting and I enjoyed reading. Thank you very much. While I appreciate authors efforts for investigating different important variables in the field level, there were quite a few points should be carefully addressed. Fundamentally, the experimental set up affects at least three players in context, plant, AMF and soil. It should be clearly addressed if there was plant really showed drought stress if authors want to address in title if the study can tell facts about plant drought responding strategy. Also throughout the manuscript, authors have over-interpreted some results. Postulations should be differentiated from result interpretation. I think overall study is meaningful and interesting, but there are many points to be improved with additional analyses as well as checking for interpretation.
Response: We appreciate the reviewer’s positive suggestions and helpful comments on our work. We have made great revisions and toned down some conclusions based on our data according to the reviewer’s comments. We believe the revised manuscript could meet the request for publication in Forests journal.
Abstract
Overall, I felt abstract is bit hard to understand. I would recommend to improve it.
Response: Apologizes for our unclear writing. We have reworded part of the abstract.
L25-26 It is difficult to understand what is the difference between hyphae density and infection rate. This should be clearly addressed before this statement. Otherwise, it is hard to understand.
Response: The infection rate is an important indicator of the close symbiosis between AMF and plants. AMF can expand the absorption area and accessibility through hyphae, and enhance the occupation of soil. These are two different properties of AMF.
L28-29 It is hard to understand the meaning of this result for the general context. Authors should explain why this was measured and what is the meaning.
Response: We would like to know what is the key factor affecting AMF composition, and thus we did a random forest analyses (we removed this in revised version) and redundancy analyses.
L30-33 I am not sure authors can really claim this based on their results. The supports are rather to be weak to claim that. I think main conclusion should be reframed.
Response: We have reframed our main conclusion in the abstract.
Introduction
L41-43 community composition of plants… above and below ground -> It is hard to understand the meaning of sentence. Are you talking that there are below ground plant community?
Response: Agree. We’ve rephrased this sentence as” Drought affects not only the growth and community composition of aboveground plants, but also the underground parts of plants and the diversity and community composition of microorganisms.”
L43-46 The logic for linking arbuscular mycorrhiza and drought is weak, what is the context for introducing arbuscular mycorrhiza here? Since the main focus of manuscript is about this, should be addressed in better way.
Response: Agree. We rewrote the phrase by adding additional sentence to make a better logic. Please see Line 45-48.
L95-97 I would recommend authors to introduce more about the drought effect on their main model system (Chinese fir). Although it is the main, the description of drought stress or damage is bit simple.
Response: Done. We have added the specific effects of drought on Chinese fir. Please see Line 101-114.
L101-102 I don’t think authors have really measured carbon. Hypothesis should be carefully addressed and it should be matching with what author really measured and interpret. Assuming that putting more carbon will result in increase of AMF infection or growth is bit naïve. As AMF also can store the carbon as vesicle with lower infection rate or growth. It is hard to be directly interpreted.
Response: We appreciate the reviewer’s helpful notes and suggestions. We have reworded our hypothesis.
Materials and Methods
One of the most important fact is that author’s hypotheses are about drought, but actual application was 50% precipitation control. I think it is better to provide some information about how much drought it can actually make with the treatment. For example, if the plant really showed drought response or not. Because if the precipitation is already more than enough for the plant (as different species requires different water amount for thriving), then the experimental setup that author is simply comparing over-watered vs normal or normal vs normal, not normal vs drought as authors intended. Also provide some information about the system with previous studies (or literatures).
Response: We appreciate the reviewer’s helpful suggestions. Yes, previous studies have shown that rainfall in our study area is declining and there are also strong seasonal droughts. The 50% reduction in rainfall that we used to predict drought is a relatively extreme case, but it actually happens during the drier dry season – seasonal drought. So, our study is not only looking at drought on an interannual scale but also on a seasonal scale. Chinese fir has a high-water requirement, the more adequate water, the better the Chinese fir grows. Therefore, this tree species is usually widely spread in subtropical China which have a humid climate.
Anyway, we have added some information to support our study as the reviewer’s suggestion. We think the revised version must be very solid. Please see Line 134-145.
Figure1 legend is not fully explaining panel A
Response: Since this article only selects precipitation reduction (P) and control (CT) treatments in the experiment for comparison, we did not introduce the other treatments in this work.
L137 Two years of drought.. -> I am not sure the description is carefully addressed. Please rephrase the sentence for reflecting the experiment.
Response: Done. We’ve rephrased this sentence as “After two years of precipitation exclusion experiments.”
L178 Please describe the measurement of hyphal density to be soil hyphal density to avoid confusion
Response: Done, we have added some information for introduce both, please see Line 188-217.
Results
The term exclusion is misleading. I think authors have used this term for entire manuscript, even in materials and methods (description related with plot design and figure 1). What authors actually did was not complete blocking of precipitation. The term should be changed for appropriate alternatives. Precipitation control or reduced precipitation (by 50%).
Response: Thanks for the reviewer’s suggestions. We used PR (precipitation reduction) instead of PE according to Fig. 1a throughout the manuscript.
L224 Furthermore, there were significant interactions between season and treatment (P=0.048; Table 2), indicating that precipitation exclusion reduced the seasonal difference in root diameter. -> This is already explained by previous sentence that there is interaction effect. Authors can simply say the interaction effect was confirmed. Otherwise, it is just a redundant description.
Response: Agree. We’ve rephrased this sentence as” Furthermore, the multi-factor analysis also confirmed a significant interaction between seasons and treatments (P=0.048; Table 2).”
L280-281 I think what authors did was revealing correlation, not the causality testing. It is hard to say one factor “affected” the other factor in this case. The interpretation for this and throughout discussion should be re-phrased.
Response: Agree. We’ve changed " affected " to "related".
Discussion
It is important to provide the support that there was “drought” taken place, as that is a base for whole interpretation. It will be nice to show the data that plants have experienced drought stress.
Response: Agree. It has been clearly evidenced that annual precipitation is declining during the long-term period in the tropical and subtropical region and thus amplify the seasonal drought effect in our study area (Zhou et al., 2011).
Zhou, G., Wei, X., Liu, S., et al. 2011. Quantifying the hydrological responses to climate change in an intact forested small watershed in Southern China. Global Change Biology, 17, 3736–3746
L333-334 The interpretation is bit inappropriate as authors cannot know if the phenomenon was caused by plant or fungi. Consequently, the following interpretation about strategy is also carefully addressed. Currently, many sentences in the manuscript are bit exaggerated or over-interpreting the results. Authors should check throughout manuscript that what can be addressed, and in which degree they can say or “postulate”.
Response: Thanks for the reviewer’s suggestions. We have toned down this interpretation. We agreed with the reviewer’s suggestion to use the postulate here.
L351-352 The soil characteristic is associated with AMF, but could this be linked with drought treatment in the study? It is hard to understand if the soil characteristic analyses to compare control vs treatment was conducted or not in this study. Simply, there would be at least three players in the context, Soil, plant, and AMF. I think the study still could not answer for the causality or strategy of plant for drought. Authors should first compare the treatment effect on soil characteristics to really discuss some changes.
Response: We totally agreed with the reviewer’s concerns. We tried to compare the treatment effect on soil properties and just saw the season effect on DOC, but there is a significant or marginal significant treatment effect on N availability (DON and NH4+). Anyway, we have toned down our writing.
Conclusion
L360 This improved the Chinese fir roots’ ability to absorb… -> Authors cannot say “improved” as there was no support for that. Should be noted as “might have improved, or postulated to be improved”.
Response: Done. Please see Line 402.
L362 Also this interpretation is bit misleading. Since authors cannot know if the decision maker of the observation was plant or AMF or soil, it is hard to simply conclude there is “a change in investment”. During my review of manuscript, I could see many cases of this over-interpretation. Authors should just say what can be told by the correlation analyses. There is no causality can be called, except for the very direction comparison of variables between treatment and control.
Response: Agree. The direction comparison must be the best way to make solid conclusions. We have toned down our wording here, like added “may”.
L364 Chinese fir will -> Chinese fir might
Response: Done. Please see Line 407.
L366 mycorrhizae will increase -> mycorrhizae might increase
Response: Done. Please see Line 408.
L367 Drought will enhance -> We postulate that drought might enhance
Response: Done.
Round 2
Reviewer 1 Report
The authors have addressed my comments, many thanks for their contribution
Reviewer 3 Report
Thank you to the authors for providing the revised manuscript and incorporating the suggested revisions. This has resulted in a much more concise, clear manuscript. However, there are several areas where revisions have been made in accordance with those suggested by reviewers, but the sentence structure and phrasing make comprehension difficult. I recommend very minor revisions, with specific examples below:
L 103 Restructure introductory sentence as follows: “With changing climates, plant root-soil-
microorganism interactions become increasingly important, especially considering rhizosphere processes and biogeochemical cycles.”
L 114-116 Make its own sentence, replacing the colon with a period, and capitalizing “under” to begin new sentence.
L 214-235 Thank you for providing this information, but please write in past tense to remain consistent with previous methods. For instance, in L 214, perhaps begin the sentence like such: “Five grams of air-dried soil were added to 800 mL of clean water and stirred thoroughly in order to disperse mycelia”. Similarly, “stack” should be written as, “Then, 20- and 400-mesh sieves were stacked.” As written, it sounds more like a written protocol, rather than procedures that were conducted past tense. Similar language should be used throughout this small section. Otherwise, thank you for the inclusion of this information.
Reviewer 4 Report
My previous comments were adequately addressed. Thank you for the revision.
