Different-Sized Vessels of Quercus variabilis Blume Respond Diversely to Six-Year Canopy and Understory N Addition in a Warm-Temperate Transitional Zone

Round 1

Reviewer 1 Report

Dear Authors,

I carefully read your interesting manuscript.

General part

The Introduction is exhaustive presenting previous research on tree growth responses and variation of traits related to changing environment conditions, and the effect of simulated N deposition applied to the soil or on the canopy. Authors introduced the problem with well selected references. The aim of the research is well pointed out. Materials And Methods chapter is well presented. The methods sufficiently documented to allow replication studies.  Some information should be given on the threshold selected for dividing the growth ring in three parts. How the authors chosen them, should be specified. The statistical methods are valid and correctly applied. Results chapter is well organized and figures and tables useful to better understand data. The supplementary data in my opinion should be cited in this section, avoiding citation in Discussion. The quality of the figures and tables is satisfactory. In Discussion chapter, authors well discussed the findings and make the reader easily know other research on the area, linking the previous results to their ones. They should avoid the citation of figures and supplementary data in discussion section. Conclusion are based on the findings and may open new study perspectives.

Reference list covers the relevant literature adequately and in an unbiased manner.

Specific remarks

Line 166 This is tautological. Please report the definition.

Check typos.

Lines 175-176 Please explain why you selected these 3 thresholds for dividing the ring width.

 

Supplementary materials

Table S1: Adding height could be interesting for readers to better understand results.

Figure S3. Please, give the definition of each group because the figures need to be self-explaining.

Please check the note.

Comments for author File: Comments.pdf

Author Response

Comments and Suggestions for Authors

Dear Authors,

I carefully read your interesting manuscript.

General part

The Introduction is exhaustive presenting previous research on tree growth responses and variation of traits related to changing environment conditions, and the effect of simulated N deposition applied to the soil or on the canopy. Authors introduced the problem with well selected references. The aim of the research is well pointed out. Materials And Methods chapter is well presented. The methods sufficiently documented to allow replication studies.  Some information should be given on the threshold selected for dividing the growth ring in three parts. How the authors chosen them, should be specified. The statistical methods are valid and correctly applied. Results chapter is well organized and figures and tables useful to better understand data. The supplementary data in my opinion should be cited in this section, avoiding citation in Discussion. The quality of the figures and tables is satisfactory. In Discussion chapter, authors well discussed the findings and make the reader easily know other research on the area, linking the previous results to their ones. They should avoid the citation of figures and supplementary data in discussion section. Conclusion are based on the findings and may open new study perspectives.

Reference list covers the relevant literature adequately and in an unbiased manner.

Responses: Thanks for your suggestions and comments. As you suggested, more information is added to the revised manuscript to explain why the vessels along tree-ring were divided into three parts (lines 178-186). The supplementary data was cited in results, and only Figure S4 was cited in two sentences in discussion where I suppose necessary (Line 361, 443). Details of revisions were listed as follows and in the revised manuscript. In the revised manuscript with revision tracks, revised sentences were marked with yellow highlight.

Specific remarks

Q1：Line 166 This is tautological. Please report the definition. Check typos.

Response: As reviewer suggested, π was defined and the typos of the unit was corrected (line 171-172).

Revised sentence: “where π is the ratio of the circumference of a circle to its diameter (π=3.14), ρ is the density of water at 20 °C (998.2 kg m⁻³)”

Q2: Lines 175-176 Please explain why you selected these 3 thresholds for dividing the ring width.

Response: Detailed explanation was added to the section of materials and methods in revised manuscript (Line178-186).

Revised sentences: “Based on GAM-modelled curves of vessel size along the tree-rings, vessel size in all treatments sharply decreased from the start of the tree-ring, i.e. the 0th % of the tree-ring, to the 30th % of the tree-ring, followed by a slow decrease from 30th % to 100th % along the tree-ring (Supplementary Figure. S3). Meanwhile, in order to have a comparable un-derstanding of the first 3/10 and last 3/10 vessels along tree-ring, the vessels be-tween70th %-100th % along tree-ring was also selected for our analysis. Therefore, the vessels in each tree ring were divided into three groups, which were group I (i.e. 0th %-30th % along tree-ring), group II (i.e. 30th %-70th % along tree-ring) and group III (i.e. 70th %-100th % along tree-ring).”

 

 Q3: Please explain EDF, figure should be self-understanding.

Response: As suggested, EDF was explained at the figure note in the revised manuscript (line 231-232).

Revised sentence: “EDF, the effective degrees of freedom (edf) estimated from generalized additive models.”

Supplementary materials

Q4: Table S1: Adding height could be interesting for readers to better understand results.

Response: As reviewer suggested, tree height was added to the supplementary table.

Revised table:

Table S1 Tree Height and diameter at breast height (DBH) of the selected Quercus variabilis Blume for measurements of radial growth and vessel related indexes.

Treatment	DBH (cm)	Height
Control	33.2 (7.5)a	18.7 (2.7)a
CN	34 (8.4)a	18.5 (3.1)a
UN	38.7 (6.2)a	20.85 (3.5)a

 

Q4: Figure S3. Please, give the definition of each group because the figures need to be self-explaining. Please check the note.

Response: thanks for reviewer’s suggestion, new panel labels and definition of each group were added to this figure to make the information easier to read.

Figure S4. Vessel density of each group (i.e. group I, II, and III) in Q. variabilis under Control, canopy N addition (CN) and understory N addition (UN) treatment during 2013-2018.

Note: density of vessels (number/mm2) = number of vessels of groups/the detected xylem area of each year in each tree. Group I is the vessels located between the start, i.e. 0th %, to 30th % of the tree-ring, group II is the 30–70% of the tree-ring and group III is the 70–100% of the tree-ring.

 

Author Response File: Author Response.docx

Reviewer 2 Report

The review of the manuscript titled “Different sized vessels of Quercus variabilis Blume respond diversely to six-year canopy and understory N addition in a warm-temperate transitional zone " by Shaokang Zhang, Biyun Yu, Peng Zhou, Jianguo Huang, Shenglei Fu, Wei Zhang.

The manuscript by Jianguo Huang (corresponding author) and others aimed at determining the effect of a steady increase in N deposition on vessel-related characteristics of Quercus variabilis, one of the most important temperate deciduous tree species in eastern Asia. This work characterizes tree response to canopy and understory N additional deposition in the range of vessel-related traits. The experiment was conducted from 2013 to 2018. The results of the experiment are well described however, it contains several deficiencies that require attention and should be corrected.

Introduction and Methods
The Introduction and Materials and Methods sections of the manuscript are written accurately. The first section of the manuscript shows the actual state of knowledge in the subject of the manuscript. For the most part, the biological material, a study site, and experimental design are described precisely. However, the climatic condition on the experimental plots is described too generally (Line 115-117). From the point of view of the rest of the manuscript, i.e., the Results and Discussion sections, the Materials, and Methods section should be supplemented with a more precise description of climatic conditions. In the current version, the Authors presented only general information, which interpreting results difficult (see commentary in the Results and the Discussion part of the review).

Results
The authors found that there was an interaction between the vessel characteristics and the year of the study (Line 277-280). It can be assumed that this is related to the climatic conditions of a given year. In the description of the experimental plot, the authors give only the average temperature and average precipitation for 60 years. There is a lack of presentation of the distribution of climatic characteristics in the period of sample collection from 2013 to 2018. In my opinion Materials and Methods section should be completed with a graph of temperature and precipitation during the sampling period (2013-2018). Perhaps then it will be possible to identify the climatic factor affecting the vascular characteristics of the studied trees. In addition, the presentation of such data, especially precipitation, will perhaps allow a more accurate analysis of the effect of precipitation on soil water potential and an analysis of its effect in the case of soil nitrogen fertilization.

Discussion
Regarding the vessel-related traits of group II, the authors show the influence of CN treatment. They show that young leaves create carbon compounds for the whole tree (lines 371-373). I remark that very young leaves often do not generate enough assimilates to ensure their growth. This needs to be explained more precisely. The present description is insufficient and too general.
As with group II, the authors find an effect of year on plant response. Also in this case it is advisable to describe more precisely the environmental conditions on the research plot, which may enable better interpretation of the results.  

Author Response

Comments and Suggestions for Authors

The review of the manuscript titled “Different sized vessels of Quercus variabilis Blume respond diversely to six-year canopy and understory N addition in a warm-temperate transitional zone " by Shaokang Zhang, Biyun Yu, Peng Zhou, Jianguo Huang, Shenglei Fu, Wei Zhang.

The manuscript by Jianguo Huang (corresponding author) and others aimed at determining the effect of a steady increase in N deposition on vessel-related characteristics of Quercus variabilis, one of the most important temperate deciduous tree species in eastern Asia. This work characterizes tree response to canopy and understory N additional deposition in the range of vessel-related traits. The experiment was conducted from 2013 to 2018. The results of the experiment are well described however, it contains several deficiencies that require attention and should be corrected.

General response: Thanks for reviewer’s constructive suggestions and comments. We have made revisions on the manuscript, especially on result and discussion, to furtherly improve the whole texts. In the revised manuscript with revision tracks, revised sentences were marked with yellow highlight.

Introduction and Methods
The Introduction and Materials and Methods sections of the manuscript are written accurately. The first section of the manuscript shows the actual state of knowledge in the subject of the manuscript. For the most part, the biological material, a study site, and experimental design are described precisely. However, the climatic condition on the experimental plots is described too generally (Line 115-117). From the point of view of the rest of the manuscript, i.e., the Results and Discussion sections, the Materials, and Methods section should be supplemented with a more precise description of climatic conditions. In the current version, the Authors presented only general information, which interpreting results difficult (see commentary in the Results and the Discussion part of the review).

Response: as reviewer suggested, a figure of temperature and precipitation during the sampling period (2013-2018) was provided in the section of materials and methods. Meanwhile, a more detailed description of the climatic condition was added (line 118-124).

Figure 1. Annual mean temperature and total precipitation of the study site during the detected year (2013-2018).

 

Results
The authors found that there was an interaction between the vessel characteristics and the year of the study (Line 277-280). It can be assumed that this is related to the climatic conditions of a given year. In the description of the experimental plot, the authors give only the average temperature and average precipitation for 60 years. There is a lack of presentation of the distribution of climatic characteristics in the period of sample collection from 2013 to 2018. In my opinion Materials and Methods section should be completed with a graph of temperature and precipitation during the sampling period (2013-2018). Perhaps then it will be possible to identify the climatic factor affecting the vascular characteristics of the studied trees. In addition, the presentation of such data, especially precipitation, will perhaps allow a more accurate analysis of the effect of precipitation on soil water potential and an analysis of its effect in the case of soil nitrogen fertilization.

Response: as reviewer suggested before, a figure of temperature and precipitation during the sampling period (2013-2018) and a corresponding description was also added to the section of materials and methods (line 118-124).

We agree with reviewer that analysis on other climatic or environmental factors might allow more comprehensive understanding on vascular characteristics. However, in this study, we mainly focus on effect of N addition, the influence of other environmental factors was not related to the aim of this study. Thus, in data analysis, these climatic factors were properly considered and treated and were all included into the factor of “year” in our analysis. However, as suggested, we also add some discussion on this point in the discussion section (line 384-387).

 

Discussion
Regarding the vessel-related traits of group II, the authors show the influence of CN treatment. They show that young leaves create carbon compounds for the whole tree (lines 371-373). I remark that very young leaves often do not generate enough assimilates to ensure their growth. This needs to be explained more precisely. The present description is insufficient and too general.
As with group II, the authors find an effect of year on plant response. Also in this case it is advisable to describe more precisely the environmental conditions on the research plot, which may enable better interpretation of the results.  

Response: as reviewer suggested, discussion about effects of young leaves and environmental conditions was revised to make the explanation more precisely (line375-378).

In our results, effect of year or the interaction between year and treatment was not significant for vessel of group II. However, for vessels of group III, interaction effect between treatment and year was significant. In term of this result, more information about environmental conditions of the study site and corresponding discussion was added to make a better interpretation on the results.

Author Response File: Author Response.docx

Round 2

Reviewer 2 Report

The manuscript has been significantly revised. The authors have added a figure with mean temperature and precipitation and clarified aspects that were requested by providing missing information or revising the previous version of the manuscript. The Results and Discussion sections have been supplemented with relevant passages.


I think I can now recommend this manuscript for publication in Forestry