Drought Impact on Eco-Physiological Responses and Growth Performance of Healthy and Declining Pinus sylvestris L. Trees Growing in a Dry Area of Southern Poland

Round 1

Reviewer 1 Report

The paper “Drought impact on eco-physiological responses and growth performance of healthy and declining Pinus sylvestris. L trees growing in a dry area of Southern Poland” contributes to the study of tree sensitivity to drought at the local scale. The authors performed an extensive comparative analysis of healthy and declining trees surviving drought growing in the same bounded area.

In research articles, abstracts should provide a brief overview of the work. I strongly encourage authors to rewrite the abstract using the journal's suggested structure, emphasizing the main conclusions or interpretations.

The introduction provides a good overview of the background information and the relevant literature. The authors have made a considerable effort to provide comprehensive information about the issues being studied. All obtained results are detailed in the discussion with supporting references to similar studies.

My main concern is that I do not see sufficient novelty in this paper. We know quite a lot (and it is well highlighted in the manuscript) about the effect of drought on a variety of conifers.  And this work only confirms the conclusions made earlier. Perhaps the authors should concentrate on the uniqueness of the study and emphasize this clearly in the discussion. This would make the work more attractive to the Forests reader.

Specific comments

Ln 157-159: Not sure if the sentence belongs to this section. It could be replaced in the "Acknowledgements" or "Author Contributions".

Ln 166: Please correct to "RStudio" and add a link to the mentioned package.

Ln 294: Сheck the significance level. The expression p>0.05 does not make sense in this format.

Fig 1: You should mention all the colors on the plot, even if it seems obvious. Please convert all axis captions to the same case.
You use different terms “mean” and “average” in the plot and in the caption. I would recommend a unified term.

Fig 3: Why are maximum rather than average temperatures considered in this case?

Fig 5c: Negative coefficients of determination do not exist. Check the correctness of the specified value R².

Author Response

Revision of the manuscript entitled: Drought impact on eco-physiological responses and growth performance of healthy and declining Pinus sylvestris. L trees growing in a dry area of Southern Poland

First, we would like to thank the Editor and Reviewers for their careful reading of the manuscript and constructive remarks. We have taken the comments on board to improve and clarify the manuscript and we believe the quality of the revised paper has been significantly improved.

Please find below a detailed point-by-point response to all comments.

1. Please replace or remove refs from Forests during revision.

Done

2. 
   Please check and reduce self-citation during revision.

      Done

Academic Editor Comments

• For the SPEI the time window of the aggregation before August must be explained.  ?

We specified in line 173, that we were using SPEI3.

• 
  The reference 60 is not relevant.

We removed reference 60, We have added a more appropriate citation: McCarroll, D.; Loader, N. J. Stable isotopes in tree rings. Quaternary Science Reviews 2004, 23 (7-8), 771-801, Conference Paper. DOI: 10.1016/j.quascirev.2003.06.017 Scopus.

• 
  The sharp rise in intrinsic WUE is surprising. It needs to be carefully justified.

 We have added lines in Discussion addressing this issue (lines 420-424).

• 
  A description of the phenology of the secondary growth of Pinus sylvestris L. would be useful. 

We have added a paragraph about Pinus sylvestris L. growth phenology in 2.1 subsection.

Rev 1

The paper “Drought impact on eco-physiological responses and growth performance of healthy and declining Pinus sylvestris. L trees growing in a dry area of Southern Poland” contributes to the study of tree sensitivity to drought at the local scale. The authors performed an extensive comparative analysis of healthy and declining trees surviving drought growing in the same bounded area.

In research articles, abstracts should provide a brief overview of the work. I strongly encourage authors to rewrite the abstract using the journal's suggested structure, emphasizing the main conclusions or interpretations. 

We have rewritten the abstract using the suggested structure.

The introduction provides a good overview of the background information and the relevant literature. The authors have made a considerable effort to provide comprehensive information about the issues being studied. All obtained results are detailed in the discussion with supporting references to similar studies.

My main concern is that I do not see sufficient novelty in this paper. We know quite a lot (and it is well highlighted in the manuscript) about the effect of drought on a variety of conifers.  And this work only confirms the conclusions made earlier.

Perhaps the authors should concentrate on the uniqueness of the study and emphasize this clearly in the discussion. This would make the work more attractive to the Forests reader.

In the Discussion and conclusion section, we have included sentences emphasizing the distinctiveness of this study and its importance for forest management strategies at local and regional scale.

Specific comments

Ln 157-159: Not sure if the sentence belongs to this section. It could be replaced in the "Acknowledgements" or "Author Contributions".

We removed the sentence.

Ln 166: Please correct to "RStudio" and add a link to the mentioned package.

 Done

Ln 294: Сheck the significance level. The expression p>0.05 does not make sense in this format. We have checked the significance levels and corrected to p<0.05.

Fig 1: You should mention all the colors on the plot, even if it seems obvious. Please convert all axis captions to the same case. You use different terms “mean” and “average” in the plot and in the caption. I would recommend a unified term.

 Done

Fig 3: Why are maximum rather than average temperatures considered in this case?

Both graphs (for average and maximum temperature) are similar, but the average temperature graph shows greater similarity to δ¹³C trends over the last 10 years of analysis. Therefore, we replaced the Figure 3b, as now it presents average temperatures instead of maximum temperatures.

Fig 5c: Negative coefficients of determination do not exist. Check the correctness of the specified value R².

 Done

Reviewer 2 Report

The authors have contributed nice research on the tree growth-drought relationships using both ring width and C stable isotopes of tree rings in southern Poland. The design and flow of the manuscript is sound and easy to follow. The comparison between healthy and declining trees in terms of growth and physiological processes hold the meanings for drought-related forest dynamics and would be of interest to a wide audience and fit in the scope of the journal. Nonetheless, below concerns remain for the authors to resolve before acceptable for publish.

Major point:

The trend of the δ¹³C is problematic because of the dilution effects from the burst in the CO2 in the atmosphere as the burning of fossil energy. We should adjust and detrend the raw series according to the pre-industrial revolution conditions.

Specific points:

L25-26: It is not surprising that the iWUE increased for both occasions here and should be removed or replaced by more important concluding sentence here.

L416: “tree specimen”?

L421-425: Please be more specific on the conclusions. Not just something like “different”, instead, “different how”?

Fig. 1: It’s quite misleading to see the mark of the weather station. It should not be a tower because, in general, the weather data are collected near the surface of the ground.

Table 1: Headline, you have two spaces between the two words in the last column.

L169-170: Here, you should clarify if your cores had reached the pith. If not, how did you deal with that?

Minor editing is needed.

Author Response

REV 2

The authors have contributed nice research on the tree growth-drought relationships using both ring width and C stable isotopes of tree rings in southern Poland. The design and flow of the manuscript is sound and easy to follow. The comparison between healthy and declining trees in terms of growth and physiological processes hold the meanings for drought-related forest dynamics and would be of interest to a wide audience and fit in the scope of the journal. Nonetheless, below concerns remain for the authors to resolve before acceptable for publish.

Major point:

The trend of the δ¹³C is problematic because of the dilution effects from the burst in the CO2 in the atmosphere as the burning of fossil energy. We should adjust and detrend the raw series according to the pre-industrial revolution conditions.

The raw series were adjusted and detrended according to McCarroll, D. and Loader, N. J., 2004, to remove antropoghenic trend. As it was not written clear enough, we highlited it in 2.5 subsection (lines 226-230).

Specific points:

L25-26: It is not surprising that the iWUE increased for both occasions here and should be removed or replaced by more important concluding sentence here.

 Done

L416: “tree specimen”?

Done

L421-425: Please be more specific on the conclusions. Not just something like “different”, instead, “different how”?

We have improved Conclusion section, to make it more specific.

Fig. 1: It’s quite misleading to see the mark of the weather station. It should not be a tower because, in general, the weather data are collected near the surface of the ground.

 We have modified Fig. 1, to make it more readable.

Table 1: Headline, you have two spaces between the two words in the last column.

 Done

L169-170: Here, you should clarify if your cores had reached the pith. If not, how did you deal with that?

We had reached the pith, so we add this information in the text.

Comments on the Quality of English Language

Minor editing is needed.

We revised the English.

Reviewer 3 Report

Dear Authors,

Thank you for this comprehensive and insightful research paper. It has very clear objective, methodological approaches, rather extended discussion, but not appropriate conclusion sections. Overall, a valuable and high value work has been done, but anyhow I have a few comments:

 1) I think it the paper would benefit if the term "drought" would be defined and clarified in the context of this study.  

2) The site location map should be improved and show the location of sampled trees, both healthy and declining ones. It could be also a schema incorporated with the map. The importance of site topography. also is highlighted by lines 338-340. 

3)Why 5 sampling trees were chosen? Only on the base of referenced similar studies or some other factors also were taken into account. If it is based only on references from other studies, than statement needed to describe that site conditions are so similar, that selected number of samples are enough?

4)Figure 5 label should be rephrased to make it clearer

5)I suggest shifting some lines, e.g. 341-348 or 398-409 from discussion section to "Introduction", as they mostly are part of literature analyses. 

6) Conclusion section should be improved, as it is not completely expressed the huge amount of work, analyses and results.

Author Response

REV 3

Dear Authors,

Thank you for this comprehensive and insightful research paper. It has very clear objective, methodological approaches, rather extended discussion, but not appropriate conclusion sections. Overall, a valuable and high value work has been done, but anyhow I have a few comments:

• I think it the paper would benefit if the term "drought" would be defined and clarified in the context of this study.  

As in literature several different definitions of drought exist, we added a reference to a review paper discussing this topic. Furtherly we clarified that for the aims and scope of this paper we considered as droughty years the ones where the SPEI value was below 1.5; following Shekhar, A. and Shapiro, C. A. 2019.

2)The site location map should be improved and show the location of sampled trees, both healthy and declining ones. It could be also a schema incorporated with the map. The importance of site topography. also is highlighted by lines 338-340. 

We have modified Fig. 1, to illustrate better our sampling site

3)Why 5 sampling trees were chosen? Only on the base of referenced similar studies or some other factors also were taken into account. If it is based only on references from other studies, than statement needed to describe that site conditions are so similar, that selected number of samples are enough?

The previous sentence was poorly worded. We changed it to: “Previous research confirms the effectiveness of using this number of trees in similar analyses ^59-60”, to show that a relatively small number of the studied trees was also used by other researchers.

4)Figure 5 label should be rephrased to make it clearer

 Done

5)I suggest shifting some lines, e.g. 341-348 or 398-409 from discussion section to "Introduction", as they mostly are part of literature analyses. 

We have shifted lines 398-409 to the second to last paragraph of Introduction, as it suited there better.

6) Conclusion section should be improved, as it is not completely expressed the huge amount of work, analyses and results.

We have improved Conclusion section, to make it more specific.

Round 2

Reviewer 2 Report

I can see my concerns well resolved in current version of the manuscript and suggest acceptance as it is.

Author Response

First, we would like to thank the Editor and the reviewers for their careful reading of the manuscript and all the suggestions. We have taken the comments on board to improve and clarify the manuscript and we believe the quality of the revised paper has been improved.

Please find below a detailed point-by-point response to all comments.

Academic Editor Comments

• For the SPEI the time window of the aggregation before August must be explained. I'm still trying to find which backward windows (1, 2, 3, 6 months or more?) you've used for the August SPEI. I suggest you reread Vicente-Serrano's works.

We specified in lines 174-175, that we were using SPEI-3, with a 3-month backwards accumulation window, further called “SPEI” for simplicity.

• 
  The reference 60 is not relevant. I've reread reference 60 in vain. It only concerns water isotopes.

The Editor's first comment referred to the citation from Robertson et at. ⁶⁰ (according to the previous numbering) in line 223. After the first correction, we removed this reference as it was incorrect. Instead, in line 223 we refered to McCarroll, D.; Loader, N.J. ⁶⁶ (according to the new numbering), which is appropriate for the data used. Robertson et al. is no longer cited in our manuscript.

• 
  The sharp rise in intrinsic WUE is surprising. It needs to be carefully justified.

In lines 409-422 we referred to the sharp rise in iWUE. In the explanation, we cited research that also showed a significant increase in iWUE for the same tree species. Additionally, we referred to the papers in which researchers showed iWUE magnitudes similar to ours.