The Radial Growth of Schrenk Spruce (Picea schrenkiana Fisch. et Mey.) Records the Hydroclimatic Changes in the Chu River Basin over the Past 175 Years

Round 1

Reviewer 1 Report

See attached file

Comments for author File: Comments.docx

Author Response

The introduction is very well written, but the English in much of this paper is awkward, making it hard to read and understand.

Response: Thanks for your constructive suggestions. The English writing also has been checked by a native speaker carefully and the Certification is in attachment.

 

A major concern is that the whole paper is constructed around a sample of only 21 trees. This is a very small number. Furthermore, the authors chose trees that were growing on shallow soils, ‘under the harshest conditions’ – why? I would have thought that the greater range of ring widths of trees growing under better conditions would have revealed broader ranges and thus more information about climate. In light of the authors’ intention to reveal past climatic conditions for the Chu river, it would have seemed important to sample many more trees (on the order of 100), and trees that were geographically dispersed along the course of the river, rather than occurring in only one place (although I can see the usefulness of their proximity to sources of other climate data).

Response: Thanks for your constructive suggestions. In the sampling process, we strictly follow the norms and standards of dendroclimatology (Fritts, 1976; Speer, 2010). Dendroclimatology requires a minimum sample depth is 30 cores from 15 trees. We believe that 41 cores of 21 trees can represent the radial growth of a wide range of trees. We generally chose the trees that the radial growth is restricted by the climate. Generally speaking, trees with larger slopes, thinner soil layers, less competition and less interference are considered to have fewer non-climatic factors, that is to say, climate is the main limiting factor for the growth of these trees.

We have further revised the ambiguity and inappropriateness in this part. The revised as follow,

We collected tree-ring samples on the southwestern of the Zailiy Alatau Range in northern Kyrgyzstan. The sampling site was located near the Chong Kemin River (76°23′E, 42°48′N, elevation 2,400 m, designated the “CKM” group).  41 increment cores were collected from 21 trees in virgin forest. The pure Schrenk spruce (Picea schrenkiana Fisch. et Mey.) forests present plaque in the shady slopes of mountains. We chose the trees which radial growth is limited by the climate. The trees with no injury and disease were sampled in order to minimize the signal of non-climatic effects on tree growth.

References:

Fritts HC, 1976. Tree rings and climate. Academic Press, Inc. (London), Ltd., New York.

Speer JH, 2010. Fundamentals of Tree-ring Research. The University of Arizona. Press, Tucson.

 

A second concern is that the subject of the paper is not really forests, it is climate. A very few trees are being used to reveal past climates. There were too many quite specialized terms and indices that would surely be easily understood by climate scientists, but not necessarily by readers of this journal. These terms are not defined.

Methods are not adequately described: what is ‘n’ in each of the correlations? How many years of tree rings were compared in each case with how many years of precipitation data or of temperature data? How did these correlations vary for temperature and precipitation? It’s not the chronology, but the ring width I would expect to correlate with climatic data. And how does the river flow data fit in?

Response: Thanks for your constructive suggestions. The “Forests” is an international and cross-disciplinary scholarly journal of forestry and forest ecology. Its subject areas include “forest ecology, climate change impacts, adaptation and mitigation in forests”. The special issue is "Forest Hydrology and Watershed" and focus on interactions between forests and climate hydrology at the watershed level. Our research focuses on understanding long-term climate change based on boreal coniferous trees. Therefore, we believe that our research results are drop into the journal scope and the special issue. Most conifers on the mountains are used for dendroclimatology in the world. The terms used in this study are the most basic for dendroclimatology, and there is no need to specify them in the paper.

We have further revised and made correction according to the reviewer’s comments.

 

Also, I question the significance of the correlations presented. Is an R2 of 39.5 considered strong? This reveals that just over a third of the variation in ring width/tree growth is predicted by the climatic data. Is this considered a strong enough correlation that tree rings can be used to reconstruct past precipitation? This should be given context in terms of other similar dendro-climatic studies.

Response: Dendroclimatology studies suggest that the variance explanations (R²) are considered to be available for reconstruction at around 36. So our reconstruction is credible.

 

Specific comments, line by line:

Line 50: tree rings are not a proxy for past climate change, their growth rates reflect past climate conditions – they are indirect indicators of weather patterns in the past

Thanks for your constructive suggestions. We have made correction according to the reviewer’s comments.

 

Line 88 – what does “present plaque” mean?

Thanks for your constructive suggestions. We have made correction according to the reviewer’s comments.

 

Line 90 – what does “under a canopy density of 0.6” mean. Were these subcanopy trees growing below other trees? or were these the canopy densities of the sampled trees?

Thanks for your constructive suggestions. We have made correction according to the reviewer’s comments.

 

Line 109 – “long time” – is this supposed to be “long term”?

Thanks for your constructive suggestions. We have made correction according to the reviewer’s comments.

 

110 – ‘degree’ not ‘degrees’

Thanks for your constructive suggestions. We have made correction according to the reviewer’s comments.

 

157 – what is “model skill”? model fit?

Thanks for your constructive suggestions. We have made correction according to the reviewer’s comments.

 

170 – define drying periods and wetting periods

Thanks for your constructive suggestions. We have made correction according to the reviewer’s comments.

 

177 – discussion is awkward and hard to follow. Should reference other studies that have used tree rings to reconstruct past climates

Thanks for your constructive suggestions. We have made correction according to the reviewer’s comments.

 

Figure 2 – what is ‘sample depth’? What is ‘tree ring index’? Need to define

I don't think it needs to be explained here because these are the basic concepts in dendroclimatology.

 

Figure 3 – use letters to indicate months, not numbers

Thanks for your constructive suggestions. We have made correction according to the reviewer’s comments.

 

Figure 6 – need to clearly label each of the 4 nested figures and clearly indicate what each shows

Thanks for your constructive suggestions. We have made correction according to the reviewer’s comments. At the same time, we also revised the same problem in figure 4.

 

Figure 9 – need to clearly label nested figures A and B

Thanks for your constructive suggestions. We have made correction according to the reviewer’s comments.

 

Reviewer 2 Report

There is no clear aim in the Introduction. The authors write what was done.

Figure 5- please provide the authors of the reconstruction presented on the graph.

Lines 199-203 and Figure 6- it should be presented in the Results.

Figures 7-9- it should be presented in the Results

The discussion is too technical and it is rather the extended Results section. I recommend significantly update the Discussion.

Conclusions section are just simply a summary of the paper. It has to be rewritten

Author Response

There is no clear aim in the Introduction. The authors write what was done. 

Response: Thanks for your constructive suggestions. We have rewritten it.

 

Figure 5- please provide the authors of the reconstruction presented on the graph.

Response: Thanks for your constructive suggestions. We have added the authors and references on the graph

Lines 199-203 and Figure 6- it should be presented in the Results.

Response: Thanks for your constructive suggestions. We have made correction according to the reviewer’s comments.

 

Figures 7-9- it should be presented in the Results

Response: Thanks for your constructive suggestions. We have made correction according to the reviewer’s comments.

 

The discussion is too technical and it is rather the extended Results section. I recommend significantly update the Discussion. 

Response: Thanks for your constructive suggestions. We have made some extend and some part were rewritten. 

Conclusions section are just simply a summary of the paper. It has to be rewritten

Response: Thanks for your constructive suggestions. The Conclusions were rewritten.

Reviewer 3 Report

 

Abstract: The abstract is very well written, concise, and very effective for its purpose. I suggest the authors to put in context their findings so as to show the novelty of the study and/or draw some suggestions on the implications of the findings to the current scientific base. Furthermore, I am familiar with the precipitation/drought indices, however, as the journal is a journal for Forests with a broad scope, I doubt many of the readers will understand the relevance or purpose of these indices. The authors could state very briefly what these indices are used for.

Introduction: The introduction should be expanded. The current introduction does not provide justified grounds for the need and novelty of this study (finding something for a particular region does not justify novelty). I suggest the authors to construct and lay out some proper research hypothesis. Why is this study needed? How will this study improve the current scientific understanding? These are some essential points need to be addressed in the introduction. The statement in line 42 is vague. Please clarify briefly why it is especially sensitive.  

Materials and Methods: It is unclear to me what kind of trees and how many were sampled (lines 87-91). What is scientific basis for selecting trees growing only in the harshest conditions (line 89)? Biologically speaking, there would be a huge variation due to stress in these conditions. One would rather expect that trees were selected randomly from any conditions along the river. I have not read the discussion yet, however, authors should consider in the discussion this point. The results/findings could be irrelevant to non-stressed trees, i.e. trees that are growing in non harsh conditions. I do not see also any information as to the sample size of trees and the experimental design, e.g. what was the tree-to-tree distance, where they subplots, etc (lines 85-102), information which is very important. Please state the recording interval of the meteorological data (lines 105-125). SPEI, and other indices used in the study should be properly explained (lines 105-125) by giving the most basic information otherwise most of the readers will have no idea what they really are. The methodology for correlation analyses is not explained in sufficient detail. What data were used? All the values? Averaged monthly values resulting from 24-hour data? How the data were processed and what data were finally used for the analyses? Please explain.

Conclusions: here and elsewhere, please be careful about your interpretations. Your study does not provide any scientific basis to support responses of trees to these environmental fluctuations. What your study support is association but not responses. Again, I have read the entire manuscript and do not see anywhere obvious scientific novelty at large (apart from regional relevance). Please focus on how your study advances the current scientific understanding. You can add some discussion about how your findings can contribute towards future research.

Acknowledgements: how did authors know the reviewers and editor would provide constructive comments and suggestions that improve the quality of the paper before the paper is being reviewed? Such acknowledgements are inappropriate in my opinion. This is the “duty” of the editors and reviewers.

Author Response

Abstract: The abstract is very well written, concise, and very effective for its purpose. I suggest the authors to put in context their findings so as to show the novelty of the study and/or draw some suggestions on the implications of the findings to the current scientific base. Furthermore, I am familiar with the precipitation/drought indices, however, as the journal is a journal for Forests with a broad scope, I doubt many of the readers will understand the relevance or purpose of these indices. The authors could state very briefly what these indices are used for.

Response: Thanks for your positive comments and constructive suggestions.

We have added the result of the consistent between discharge and SPEI, we also added the significance of this study in the abstract.

In addition, we added the purpose of the SPEI in data and methods.

Introduction: The introduction should be expanded. The current introduction does not provide justified grounds for the need and novelty of this study (finding something for a particular region does not justify novelty). I suggest the authors to construct and lay out some proper research hypothesis. Why is this study needed? How will this study improve the current scientific understanding? These are some essential points need to be addressed in the introduction. The statement in line 42 is vague. Please clarify briefly why it is especially sensitive.  

Response: Thanks for your positive comments and constructive suggestions. The introduction was rewritten.

 

Materials and Methods: It is unclear to me what kind of trees and how many were sampled (lines 87-91).

We have added the details and highlighted them in red.

41 increment cores were collected from 21 trees in virgin forest. The pure Schrenk spruce (Picea schrenkiana Fisch. et Mey.) forests present plaque in the shady slopes of mountains.

 

What is scientific basis for selecting trees growing only in the harshest conditions (line 89)? Biologically speaking, there would be a huge variation due to stress in these conditions. One would rather expect that trees were selected randomly from any conditions along the river. I have not read the discussion yet, however, authors should consider in the discussion this point. The results/findings could be irrelevant to non-stressed trees, i.e. trees that are growing in non harsh conditions. I do not see also any information as to the sample size of trees and the experimental design, e.g. what was the tree-to-tree distance, where they subplots, etc (lines 85-102), information which is very important. Please state the recording interval of the meteorological data (lines 105-125). SPEI, and other indices used in the study should be properly explained (lines 105-125) by giving the most basic information otherwise most of the readers will have no idea what they really are. The methodology for correlation analyses is not explained in sufficient detail. What data were used? All the values? Averaged monthly values resulting from 24-hour data? How the data were processed and what data were finally used for the analyses? Please explain.

Response: In the sampling process, we strictly follow the norms and standards of dendroclimatology (Fritts, 1976; Speer, 2010). We generally chose the trees that the radial growth is restricted by the climate. Generally speaking, trees with larger slopes, thinner soil layers, less competition and less interference are considered to have fewer non-climatic factors, that is to say, climate is the main limiting factor for the growth of these trees. In the study of dendroclimatology, samples are generally not collected by using the method of designing a sample square, and flat land (which may be disturbed by human or with better site conditions) and near river bank (which may be disturbed by rivers) are generally not selected.

All the climate and hydrological data we use are monthly data.

We have further revised the ambiguity and inappropriateness in this part.

References:

Fritts HC, 1976. Tree rings and climate. Academic Press, Inc. (London), Ltd., New York.

Speer JH, 2010. Fundamentals of Tree-ring Research. The University of Arizona. Press, Tucson.

 

Conclusions: here and elsewhere, please be careful about your interpretations. Your study does not provide any scientific basis to support responses of trees to these environmental fluctuations. What your study support is association but not responses. Again, I have read the entire manuscript and do not see anywhere obvious scientific novelty at large (apart from regional relevance). Please focus on how your study advances the current scientific understanding. You can add some discussion about how your findings can contribute towards future research.

Response: Thanks for your constructive suggestions. We have rewritten it.

 

Acknowledgements: how did authors know the reviewers and editor would provide constructive comments and suggestions that improve the quality of the paper before the paper is being reviewed? Such acknowledgements are inappropriate in my opinion. This is the “duty” of the editors and reviewers.

Response: Thanks for your constructive suggestions. We have made correction according to the reviewer’s comments.

Round 2

Reviewer 1 Report

It was helpful to know this article was for a special issue on climate.

The manuscript has been greatly improved. A few relatively minor problems with English language remain to be addressed (see below). Also, the description of sampling methods has been reduced too much. It would be important to add some of the material that was deleted, along with the phrase used in the author's response to reviewers.

Line 33: associated with westerly what? A word is missing here.

Line 89: do not start a sentence with numerals.  Write out “Forty-one”

Line 90: what does “present plaque” mean? I am familiar with the term “plaque” only in relation to dentistry. I questioned this in an earlier review and the author said he/they had addressed this concern, but the term reappears, with no definition or explanation. I can find no dictionary meaning related to trees or forests.

Line 91: delete “the”. Explain how you determined that the tree growth was most affected by climate. You said in your response to critiques of an earlier version that you had selected trees growing on shallow soils because these were most likely to reveal the effects of climate. You need to say that in the text of the methods section.

Line 109: monthly what? A word missing here

Line 111: a verb missing here

Line 141: do you mean the dominant climatic factor for tree growth, or something else?

Line 148: you must mean “transformation”, not “transform”

Line 173: add “the” before “1970s”

Line 203: add “of” before “the”

Line 206:  add “is” before “supplied”

Line 234: “growing season”, not “grow season”

Author Response

It was helpful to know this article was for a special issue on climate.

The manuscript has been greatly improved. A few relatively minor problems with English language remain to be addressed (see below). Also, the description of sampling methods has been reduced too much. It would be important to add some of the material that was deleted, along with the phrase used in the author's response to reviewers.

Response: Thanks for your positive comments and constructive suggestions.

 

Line 33: associated with westerly what? A word is missing here.

Response: Thanks for your constructive suggestions. We have made correction according to the editor’s comments

 

Line 89: do not start a sentence with numerals.  Write out “Forty-one”

Response: Thanks for your constructive suggestions. We have made correction according to the editor’s comments

 

Line 90: what does “present plaque” mean? I am familiar with the term “plaque” only in relation to dentistry. I questioned this in an earlier review and the author said he/they had addressed this concern, but the term reappears, with no definition or explanation. I can find no dictionary meaning related to trees or forests.

Response: Thanks for your constructive suggestions. We have made correction according to the editor’s comments

 

Line 91: delete “the”. Explain how you determined that the tree growth was most affected by climate. You said in your response to critiques of an earlier version that you had selected trees growing on shallow soils because these were most likely to reveal the effects of climate. You need to say that in the text of the methods section.

Response: Thanks for your constructive suggestions. We have made correction according to the editor’s comments. We added the detailed description in the text as follow.We chose trees with larger slopes, thinner soil layers, less competition and less interference, which radial growth is limited by the climate. The trees with no injury and disease were sampled in order to minimize the signal of non-climatic effects on tree growth.

 

Line 109: monthly what? A word missing here

Response: Thanks for your constructive suggestions. We have made correction according to the editor’s comments

 

Line 111: a verb missing here

Response: Thanks for your constructive suggestions. We have made correction according to the editor’s comments

 

Line 141: do you mean the dominant climatic factor for tree growth, or something else?

Response: Thanks for your constructive suggestions. We have made correction according to the editor’s comments

 

Line 148: you must mean “transformation”, not “transform”

Response: Thanks for your constructive suggestions. We have made correction according to the editor’s comments

 

Line 173: add “the” before “1970s”

Response: Thanks for your constructive suggestions. We have made correction according to the editor’s comments

 

Line 203: add “of” before “the”

Response: Thanks for your constructive suggestions. We have made correction according to the editor’s comments

 

Line 206:  add “is” before “supplied”

Response: Thanks for your constructive suggestions. We have made correction according to the editor’s comments

Line 234: “growing season”, not “grow season”

Response: Thanks for your constructive suggestions. We have made correction according to the editor’s comments

Reviewer 2 Report

After the incorporation my previous remarks I have no furtehr comments

Author Response

After the incorporation my previous remarks I have no furtehr comments

 

Response: Thanks for your positive comments.

Reviewer 3 Report

The new additions are very helpful for interpreting the results and permitting reproducibility of the study, I have no further comments.

Author Response

The new additions are very helpful for interpreting the results and permitting reproducibility of the study, I have no further comments 

Response: Thanks for your positive comments.