Mountain Taiga in a Warming Climate: Contrast of Siberian Pine Growth along an Elevation Gradient

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

General comments

While the manuscript describes a detailed examination of how a tree species is responding to a changing climate over time, it has a number of issues that need to be addressed.  There are two major concerns.  The first is that the study did not examine the health of the trees examined.  It did examine whether trees died, but has little to say about the rate of mortality.  To do that the process of mortality would have to be followed over time.  What was examined was cumulative mortality over some undetermined period of time.  This is of use, but not nearly as insightful as actually following trees as they die.  Second, the authors need to be more careful about describing relationships.  Given the nature of the work, these are correlational.  They certainly suggest some causes, but they certainly do no prove them (which is fine).  But the authors do need to be more careful about what they found and what they studied. 

Throughout the manuscript there are odd word choices and concepts.  I have tried to indicate many of them below, but the manuscript needs to be reviewed in detail to eliminate as many of these problems as possible. 

Specific comments (line)

2 should this be “a warming climate”?  Isn’t the point the temperature is warming?

14 given that health is an ambiguous term and not referred to in the subsequent text I suggest it be deleted.  A better word would be survival as the abstract mentions mortality. 

23 “on the growth” should be “in growth”

26 I am not sure “depending” makes sense.  One could say was influenced or controlled by a variable or given the observation nature of the work more correctly the response is correlated with a variable.

29 shouldn’t winds be possessive?  That is wind’s?

31 a future contraction? Or has it already been occurring?  It is not clear as written.

37 A more general initial paragraph might be helpful in setting the context for this introduction. 

56 related?

73-74 It would be helpful if this is more fully explained.  I gather the issue is that if the different parts of SP range are associated with different environmental limitations, then the response to a warming climate may not be uniform.

76 does health status mean alive versus dead?  Or was the actual health of trees evaluated?  If so, how? In which sense?

77 shouldn’t this be “are” as it is referring to belts?

85 Why exactly?

95 it should read “The study area”

133 Given mortality is a process, it needs to be followed over time.  Since the study did not do this, it difficult to see how mortality could be determined.  The abundance of dead trees could certainly be determined with a one-time measure.  Is this what was done?

179 Is the “those” needed?

224 Do the authors mean “after this point in time” by the word “then”?

230 this seems to contradict the text that follows.  Does this effect pertain to a particular time period?

235 The text in the figures is fuzzy?  Can this be improved?

287 it should be “tree mortality” or “mortality of trees” but not “trees mortality”

305 “failed” is not the correct concept or word. 

316 “partial”?

327 “dependence” is the wrong concept.

335 “should based not” is extremely awkward.  Do the authors mean: “should not be based”?

336 “but on”?

 

  

Comments on the Quality of English Language

See extensive comments in review.

Author Response

Response to the Academic Editor and Reviewers

Authors sincerely thanks Academic Editor for the advices that strongly help us to revise MS.

Significant changes in MS highlighted by red fonts.

 

 

Response to the Academic Editor

Our response

• I see that you made several improvements to your manuscript, congratulations.
  However, your first version says that you used  "linear Pearson’s correlations" and the new version says you used "Spearman correlation"..., but, Figure 4 in both versions shows exactly the same correlation values..., is that correct?
  
  

Our response Sorry. Just a “technical errata”. Figures with true "linear Pearson’s correlations" embedded to MS.

2) I think your Conclusions section can still be improved.

Our response

Agree. Edited version: 1. The consequences of climate warming differed within different elevation belts. In the treeline ecotone, the tree’s growth was continuously increasing since the warming onset in the 1970-s, whereas in the lowlands, initial growth increase switched to a growth drop since the beginning of 2000-s with consequent partial mortality of Siberian pine forest. In the highlands, the tree’s growth was increasing until the end of 1980-s with the following-on growth fluctuations. 

2. The growth index control by air temperature and moisture variables included two phases. Firstly (from warming onset until the beginning of 2000-s), tree GI was positively correlated with elevated temperature, whereas correlations between precipitation and soil moisture were negative. During the second phase (since ca. 2000), negative correlations between GI and moisture variables switched to positive ones. The GI correlations with air temperature switched from positive to insignificant (with the exception of the beginning of the growth period).
3. The wind’s influence on the GI dramatically changed due to a continuous decrease in wind’s speed throughout the all study period. Thus, the significant negative influence of winds on the trees’ growth within all elevation belts turned to insignificant after the year 2000.
4. Within the lowlands, warming-driven water stress in combination with bark-borers’ attacks led to the tree mortality, which suggests the retraction of the Siberian pine range in the lowlands of the Siberian Mountains. The projected drought increase will likely lead to the substitution of Siberian pine with drought-tolerant species.
5. Forest afforestation within the areas of Siberian pine mortality should not be based on the planting of Siberian pine but on tolerant species such as larch (Larix sibirica) and Scots pine (Pinus sylvestris).

Response to the Reviewer 1
General comments

While the manuscript describes a detailed examination of how a tree species is responding to a changing climate over time, it has a number of issues that need to be addressed.  There are two major concerns.  

• The first is that the study did not examine the health of the trees examined.  It did examine whether trees died, but has little to say about the rate of mortality.  To do that the process of mortality would have to be followed over time.  What was examined was cumulative mortality over some undetermined period of time.  This is of use, but not nearly as insightful as actually following trees as they die.  
• Second, the authors need to be more careful about describing relationships.  Given the nature of the work, these are correlational.  They certainly suggest some causes, but they certainly do no prove them (which is fine).  But the authors do need to be more careful about what they found and what they studied. 

Our response

• The abundance of dead trees was determined within each TS.  Please see also our response to line 133 note.

 

(2). Correlations does not equivalent of the “causal relationship.“  In edited MS we are more careful in that issue. 

Our response Surely we agree with that. Yes, we corrected text,

Throughout the manuscript there are odd word choices and concepts.  I have tried to indicate many of them below, but the manuscript needs to be reviewed in detail to eliminate as many of these problems as possible. 

Our response

Agree. In hundred percent. We did our best to eliminate errors throughout in MS. Thank you for advices how to improve text language and text clarity.  

Specific comments (line)

2 should this be “a warming climate”?  Isn’t the point the temperature is warming?

Our response

Yes, the warming means that air temperature is increasing.

14 given that health is an ambiguous term and not referred to in the subsequent text I suggest it be deleted.  A better word would be survival as the abstract mentions mortality. 

Agree. “Survival” is really better term.

23 “on the growth” should be “in growth”

Our response

Agree.

26 I am not sure “depending” makes sense.  One could say was influenced or controlled by a variable or given the observation nature of the work more correctly the response is correlated with a variable.

Our response

“Controlled” is a great term.

29 shouldn’t winds be possessive?  That is wind’s?

Corrected.

Our response

31 a future contraction? Or has it already been occurring?  It is not clear as written.

Our response

Thank you. Correction: The continuous decrease in tree growth and increased mortality indicating an occurring  contraction of the Siberian pine range within the lowlands belt in southern Siberia.

37 A more general initial paragraph might be helpful in setting the context for this introduction. 

Our response

Agree. Current climate change leads to both different positive and negative consequences in the Siberian taiga. Warming together with droughts caused an increase in fire frequency and area burned (mostly in larch-dominant communities growing in the zone of permafrost) and increase in pest-outbreaks frequency with consequent conifer species mortality as well as potential changes of tree species range within its southern margins [1–3]. Alongside that, an increase in the growth of tree species has been observed, and northward and uphill migration of conifer species (Siberian pine, Pinus sibirica Du Tour, Larix spp.) was documented, as well as a general increase in gross and net primary productivity within the Siberian forests and forest-tundra zones [4–6].       

56 related?

Our response

Corrected.

73-74 It would be helpful if this is more fully explained.  I gather the issue is that if the different parts of SP range are associated with different environmental limitations, then the response to a warming climate may not be uniform.

Our response

Thank you. The Siberian pine grows both on plains and on mountains. The range of this species spreads from the Mongolian forest-steppes to the northern latitudes. The SP is a less cold-resistant tree in comparison with larch (Larix sibirica, L. gmelinii). However, it can be found beyond the Polar Circle. In the mountains, the SP, fir, and spruce form the so-called “black belt” in the mountains (within elevations of 400–2,400 m). The SP, together with Larix sp. and fir, form the treeline ecotone in the mountains. Within the ecotone, SP is often found in mat and prostrate (krummholz) forms due to limitation by temperature and wind [27]. The upper elevation limit for SP is up to 2,400+ m. Because that species is moisture-sensitive and intolerant to low air humidity, it preferably occupies high-moisture areas (with precipitation up to 1000+ mm/year), but can survive in areas with lower (about 500 mm/year) precipitation. Due to relatively humid conditions in the habitat of Siberian pine, these forest burns less often in comparison with larch-dominant communities, although in the years of extreme drought burned areas may exceed a million ha [28]. Thus, different parts of the SP range, including different elevation belts in the mountains, are associated with different environmental limitations, and then the response of SP growth and survival to a warming climate may not be uniform.

76 does health status mean alive versus dead?  Or was the actual health of trees evaluated?  If so, how? In which sense?

Our response

Corrected sentence:  These changes may lead to a contrasting influence on Siberian pine growth and survival within different parts of the SP’s range, which are including different elevational belts in the mountains.

77 shouldn’t this be “are” as it is referring to belts?

Our response

Yes. Corrected.

85 Why exactly?

Our response

The paragraphs were revised.  “GI dependence on the eco-climate variables (air temperature, precipitation, soil moisture, air drought indexes and vapor pressure deficit, wind speed). We consider growth index dynamics as a proxy of tree vigor, as well as a predictor of potential decline and mortality of trees. We hypothesize that the response of SP growth and survival to changing climate are significantly different along the elevation gradient. We suggest that warming may switch limitation of trees growth by temperature to the limitation by moisture.

We aim to answer the following questions:

1. How does SP growth respond to changes in thermal and moisture regimes along the elevation gradient?
2. Does warming switch limitation of trees growth by temperature to limitation by moisture?
3. Does the survival of SP differ within different elevation belts? “

95 it should read “The study area”

Our response

Thanks.

133 Given mortality is a process, it needs to be followed over time.  Since the study did not do this, it difficult to see how mortality could be determined.  The abundance of dead trees could certainly be determined with a one-time measure.  Is this what was done?

Our response

Thank you. Corrected fragment: We randomly sampled wood cores at the DBH level by the Pressler borer. Cores of at least 20 trees were sampled around the centerpoint of each TS within an area of about 0.5 ha. For TS located on slopes, cores were taken within the ±10 m elevation range around the centerpoint of TS. The abundance of dead trees was determined within each TS.  

 

179 Is the “those” needed?

Our response

Corrected.

224 Do the authors mean “after this point in time” by the word “then”?

Our response

Thank you. Corrected.

230 this seems to contradict the text that follows.  Does this effect pertain to a particular time period?

Our response

Yes. Corrected: Wind adverse influence was observed within all elevational belts until the end of 1990^th (Figures 4e–6e). Meanwhile, because of the persistent decrease in the wind speed (Figure 2f), winds influence on growth has become insignificant in 2000-s (Figures 4e–6e).

235 The text in the figures is fuzzy?  Can this be improved?

Our response

We checked the text clarity. In original .doc text  is fine. Possibly, “fuzzy” caused by compression of original figures to .pdf. 

287 it should be “tree mortality” or “mortality of trees” but not “trees mortality”

Our response

Thank you.

305 “failed” is not the correct concept or word. 

Our response

Agree. Corrected: Since the tipping point in 2008, the “decliner’s” dependence on soil moisture became insignificant, whereas the “survivor’s” growth was still moisture-controlled (R² = 0.38).

316 “partial”?

Our response

Yes. Corrected

327 “dependence” is the wrong concept.

Our response

Yes, wrong. Corrected: Within all elevational belts, the trees’ growth switched from control by the air temperature to control by the moisture variables

335 “should based not” is extremely awkward.  Do the authors mean: “should not be based”?

Our response

Yes, aweful.  Corrected: Forest afforestation within the areas of Siberian pine mortality should not be based on the planting of Siberian pine but on tolerant species such as larch and Scots pine.   

336 “but on”?

Our response

Corrected.

Response to the Reviewer 2

This paper focus on a growth of Siberian pine (SP, Pinus sibirica) radial growth within the treeline ecotone. The main work is limited to experimental datasets, with no deeper theoretical insights and no development of the dependencies between growth variable and other explanatory variables.  The methodology presented here is well known from previous publications and is limited to the insights of an 'experienced forester'.

 Our response

General comments:

1. The abstract and introduction does not emphasize the novelty of the work and its contribution to the field of tree’s radial growth.

Our response

1. Thank you. An Abstract and Introduction revised.

Novelty:

The consequences of climate warming differed within different elevation belts. In the treeline ecotone, the tree’s growth was continuously increasing since the warming onset in the 1970-s, whereas in the lowlands, initial growth increase switched to a growth drop since the beginning of 2000-s with consequent partial mortality of Siberian pine forest. In the highlands, the tree’s growth was increasing until the end of 1980-s with the following-on growth fluctuations. 

The growth index control by air temperature and moisture variables included two phases. Firstly (from warming onset until the beginning of 2000-s), tree GI was positively correlated with elevated temperature, whereas correlations between precipitation and soil moisture were negative. During the second phase (since ca. 2000), negative correlations between GI and moisture variables switched to positive ones. The GI correlations with air temperature switched from positive to insignificant (with the exception of the beginning of the growth period).

The wind’s influence on the GI dramatically changed due to a continuous decrease in wind’s speed throughout the all study period. Thus, the significant negative influence of winds on the trees’ growth within all elevation belts turned to insignificant after the year 2000. 

Within the lowlands, warming-driven water stress in combination with bark-borers’ attacks led to the tree mortality, which suggests the retraction of the Siberian pine range in the lowlands of the Siberian Mountains.

 Forest afforestation within the areas of Siberian pine mortality should not be based on the planting of Siberian pine but on tolerant species such as larch (Larix sibirica) and Scots pine (Pinus sylvestris).   

 

2. References are mainly the work of the authors. Lack of overview and comparison of more modern methods.

Our response

We delete a couple of references to our papers. In fact, still few studies on that problem in Siberia.

We updated the list of papers which considered a broad view on the problem.

1. Hammond, W. M.; Williams, A. P.; Abatzoglou, J. T.; Adams H. D.; Klein T.; López R.; … Allen C. D. Global field observations of tree die-off reveal hotter-drought fingerprint for Earth’s forests. Commun. 2022, 13, 1761. https://doi.org/10.1038/s41467-022-29289-2
2. Kharuk, V. I.; Petrov, I. A.; Krivobokov, L. V.; Golyukov, A. S.; Dvinskaya, M. L.; Im S. T.; Shushpanov A. S.; Smith K. T. Larch response to warming in northern Siberia. Environ. Change 2023, 23, 17. https://doi.org/10.1007/s10113-022-02016-9
3. Rao, M. P.; Davi, N. K.; Magney, T. S.; Nachin, B.; Suran, B.; Varuolo-Clarke, A. M.; … Griffin, K. L. Approaching a thermal tipping point in the Eurasian boreal forest at its southern margin.  Earth Environ.2023, 4, 247. https://doi.org/10.1038/s43247-023-00910-6
4. Maher, C.; Hewitt, R. E.; Sullivan, P. F. Sufficient conditions for rapid range expansion of a boreal conifer. Nature 2022, 608, 546–551. https://doi.org/10.1038/s41586-022-05093-2
5. Watts, J.; Farina, M.; Kimball, J.; Schiferl, L.; Liu, Z.; Arndt, K.; … Oechel, W. Carbon uptake in Eurasian boreal forests dominates the high‐latitude net ecosystem carbon budget. Chan. Biol. 2023, 29(7), 1870–1889. https://doi.org/10.1111/gcb.16553
6. Anderegg, W. R. L.; Wu, C.; Acil, N.; Carvalhais, N.; Pugh, T. A. M.; Sadler, J. P.; Seidl, R. A climate risk analysis of Earth’s forests in the 21st century. Science 2022, 377(6610), 1099–1103. https://doi.org/10.1126/science.abp9723
7. The results do not support conclusions 1 and 2 (see Figure 3)..

Our response

Consider Fig. 3 as well as Fig, 4-5 and conclusions.

“The results do not support conclusions 1 and 2 (see Figure 3)”.

Disagree.

The consequences of climate warming differed within different elevation belts. In the treeline ecotone, the tree’s growth was continuously increasing since the warming onset in the 1970-s, whereas in the lowlands, initial growth increase switched to a growth drop since the beginning of 2000-s with consequent partial mortality of Siberian pine forest. In the highlands, the tree’s growth was increasing until the end of 1980-s with the following-on growth fluctuations. 

2. The growth index control by air temperature and moisture variables included two phases. Firstly (from warming onset until the beginning of 2000-s), tree GI was positively correlated with elevated temperature, whereas correlations between precipitation and soil moisture were negative. During the second phase (since ca. 2000), negative correlations between GI and moisture variables switched to positive ones. The GI correlations with air temperature switched from positive to insignificant (with the exception of the beginning of the growth period).
3. The wind’s influence on the GI dramatically changed due to a continuous decrease in wind’s speed throughout the all study period. Thus, the significant negative influence of winds on the trees’ growth within all elevation belts turned to insignificant after the year 2000.
4. Within the lowlands, warming-driven water stress in combination with bark-borers’ attacks led to the tree mortality, which suggests the retraction of the Siberian pine range in the lowlands of the Siberian Mountains. The projected drought increase will likely lead to the substitution of Siberian pine with drought-tolerant species.

 

Specific comments:

Line 76: ... growth ... Unclear, needs clarification.

Our response

Clarification: growth index (GI)

 Lines 83-84: The hypothesis was not confirmed.

Our response

Hypothesis clarification. “We hypothesize that the response of SP growth and survival to changing climate are significantly different along the elevational gradient. We suggest that warming may switch limitation of trees growth by temperature to the limitation by moisture”.

Results obtained (summarized in Conclusions) supported that hypothesis.

 

Lines 87, 90: Isn't question 3 covered by question 1?

Our response

1. Thank you. Revised text: How does SP growth respond to changes in thermal and moisture regimes along the elevation gradient?
2. Does warming switch limitation of trees growth by temperature to limitation by moisture?
3. Does the survival of SP differ within different elevational belts?

 

Line 97: ...  northward on about 300 km... Doesn't a distance of 300 km affect temperature, soil moisture etc.?

We checked climate variables along the norward direction of the Mountains. Yes, there are some variance. For example, difference in the air temperature less then 1 degree C.  Meanwhile, in the work we are analyzing elevational climate gradients, which is, as known, steeper. In addition, Siberian pine can be found on the distance less then 300 km (i.e., ca. 250 km) along the Kuznets Ridge, although that is not main issue).     

Our response

Line 161: … a negative exponential or negative linear… Drop the word 'negative' as it refers to the correlation coefficient.

Our response

Disagree. …”a negative exponential or negative linear”… is a generally accepted terms (e.g.,  Speer 2010).

 

Line 162: … age trend… Probably, radial increment trend.

Our response

Edited version: “age-related growth trend”.

Line 164: … R_t is the tree ring width in mm; G_t is the age trend...  Explain: R_t (probably – measured, G_t - ?).

Our response

Thank you. Corrected text: R_t is the tree ring width measured in mm.

G_t is a value of age-related growth trend (in mm), calculated in ARSTAN program by standard dendrochronological techniques and presented by a negative exponential or negative linear trendline. Age-related growth trend curve calculated for each individual tree-ring chronologies by standard dendrochronological technique.

Line 176: Fig 2. Why is the coefficient of determination used instead of the correlation coefficient?

Our response

There no any correlations on the Fig. 2. There only dynamics of eco-climate variables. And trends of those variables. Although formally correlations can be considered with years.

  Line 177: Edit point (e).

Thanks. Corrected: “Air temperature (a) and June VPD (e) are increasing, whereas summer precipitation (b)”.

Line 182: … significantly increasing… What could this mean?

Our response

1. The corrected sentence is “Air temperature and VPD (June) have been increasing since the warming onset in the 1970s, whereas summer precipitation and soil moisture have been decreasing since ca. 2000 year (Figures 2a, b, d).”

Our response

Line 186: … correlation of trees growth with PDSI...  Explain: What could this mean?

Our response

Thank you. We corrected that sentence. “As data analysis showed (section 3.3), VPD is a more informative variable in comparison with sc-PDSI and SPEI

Line 193: … tree growth within all elevation belts was increasing…. What could this mean?

Our response

Thank you. Corrected sentence “Since the warming onset, tree’s growth index has been increasing within all elevational belts. i.e., lowlands, highlands and treeline ecotone”.

 Line 194: … strong positive trend… What could this mean?

Our response

Thank you. Corrected sentence Within the treeline ecotone, Siberian pine growth indicated increasing trend throughout all time interval since 1970s (Figure 3a).

Line 200: … increasing growth rates...  Explain: What could this mean?

Our response

Corrected; i.e., trees with decreasing and increasing growth trends.

Line 203: … significant trends…. What could this mean?

Our response

Thank you. Corrected text: The growth index (GI) of the “decliners” cohort has been decreasing since 2000, whereas no negative trends of “survivors” GI was not observed (Figure 3c).

Line 306: … still moisture-dependent (R2=0.38)...  Explain: What could this mean?

Our response

Thank you. Corrected text: Since the tipping point in 2008, the “decliner’s” correlations with soil moisture became insignificant, whereas the “survivor’s” growth was controlled by moisture (R² = 0.38).

Our response

The article is written in English, but the meaning of words and concepts is open to interpretation. Therefore, the article must be carefully edited.

Our response

Totally agree. We did our best to improve our “Siberian version” of English.

 

Authors sincerely thanks Academic Editor and Reviewers for the valuable advices and constructive criticism that really help to improve our MS.

 

Sincerely,

1. Kharuk,

on behalf of authors

Response to the Academic Editor and Reviewers

Authors sincerely thanks Academic Editor for the advices that strongly help us to revise MS.

Significant changes in MS highlighted by red fonts.

 

 

Response to the Academic Editor

Our response

• I see that you made several improvements to your manuscript, congratulations.
  However, your first version says that you used  "linear Pearson’s correlations" and the new version says you used "Spearman correlation"..., but, Figure 4 in both versions shows exactly the same correlation values..., is that correct?
  
  

Our response Sorry. Just a “technical errata”. Figures with true "linear Pearson’s correlations" embedded to MS.

2) I think your Conclusions section can still be improved.

Our response

Agree. Edited version: 1. The consequences of climate warming differed within different elevation belts. In the treeline ecotone, the tree’s growth was continuously increasing since the warming onset in the 1970-s, whereas in the lowlands, initial growth increase switched to a growth drop since the beginning of 2000-s with consequent partial mortality of Siberian pine forest. In the highlands, the tree’s growth was increasing until the end of 1980-s with the following-on growth fluctuations. 

2. The growth index control by air temperature and moisture variables included two phases. Firstly (from warming onset until the beginning of 2000-s), tree GI was positively correlated with elevated temperature, whereas correlations between precipitation and soil moisture were negative. During the second phase (since ca. 2000), negative correlations between GI and moisture variables switched to positive ones. The GI correlations with air temperature switched from positive to insignificant (with the exception of the beginning of the growth period).
3. The wind’s influence on the GI dramatically changed due to a continuous decrease in wind’s speed throughout the all study period. Thus, the significant negative influence of winds on the trees’ growth within all elevation belts turned to insignificant after the year 2000.
4. Within the lowlands, warming-driven water stress in combination with bark-borers’ attacks led to the tree mortality, which suggests the retraction of the Siberian pine range in the lowlands of the Siberian Mountains. The projected drought increase will likely lead to the substitution of Siberian pine with drought-tolerant species.
5. Forest afforestation within the areas of Siberian pine mortality should not be based on the planting of Siberian pine but on tolerant species such as larch (Larix sibirica) and Scots pine (Pinus sylvestris).

Response to the Reviewer 1
General comments

While the manuscript describes a detailed examination of how a tree species is responding to a changing climate over time, it has a number of issues that need to be addressed.  There are two major concerns.  

• The first is that the study did not examine the health of the trees examined.  It did examine whether trees died, but has little to say about the rate of mortality.  To do that the process of mortality would have to be followed over time.  What was examined was cumulative mortality over some undetermined period of time.  This is of use, but not nearly as insightful as actually following trees as they die.  
• Second, the authors need to be more careful about describing relationships.  Given the nature of the work, these are correlational.  They certainly suggest some causes, but they certainly do no prove them (which is fine).  But the authors do need to be more careful about what they found and what they studied. 

Our response

• The abundance of dead trees was determined within each TS.  Please see also our response to line 133 note.

 

(2). Correlations does not equivalent of the “causal relationship.“  In edited MS we are more careful in that issue. 

Our response Surely we agree with that. Yes, we corrected text,

Throughout the manuscript there are odd word choices and concepts.  I have tried to indicate many of them below, but the manuscript needs to be reviewed in detail to eliminate as many of these problems as possible. 

Our response

Agree. In hundred percent. We did our best to eliminate errors throughout in MS. Thank you for advices how to improve text language and text clarity.  

Specific comments (line)

2 should this be “a warming climate”?  Isn’t the point the temperature is warming?

Our response

Yes, the warming means that air temperature is increasing.

14 given that health is an ambiguous term and not referred to in the subsequent text I suggest it be deleted.  A better word would be survival as the abstract mentions mortality. 

Agree. “Survival” is really better term.

23 “on the growth” should be “in growth”

Our response

Agree.

26 I am not sure “depending” makes sense.  One could say was influenced or controlled by a variable or given the observation nature of the work more correctly the response is correlated with a variable.

Our response

“Controlled” is a great term.

29 shouldn’t winds be possessive?  That is wind’s?

Corrected.

Our response

31 a future contraction? Or has it already been occurring?  It is not clear as written.

Our response

Thank you. Correction: The continuous decrease in tree growth and increased mortality indicating an occurring  contraction of the Siberian pine range within the lowlands belt in southern Siberia.

37 A more general initial paragraph might be helpful in setting the context for this introduction. 

Our response

Agree. Current climate change leads to both different positive and negative consequences in the Siberian taiga. Warming together with droughts caused an increase in fire frequency and area burned (mostly in larch-dominant communities growing in the zone of permafrost) and increase in pest-outbreaks frequency with consequent conifer species mortality as well as potential changes of tree species range within its southern margins [1–3]. Alongside that, an increase in the growth of tree species has been observed, and northward and uphill migration of conifer species (Siberian pine, Pinus sibirica Du Tour, Larix spp.) was documented, as well as a general increase in gross and net primary productivity within the Siberian forests and forest-tundra zones [4–6].       

56 related?

Our response

Corrected.

73-74 It would be helpful if this is more fully explained.  I gather the issue is that if the different parts of SP range are associated with different environmental limitations, then the response to a warming climate may not be uniform.

Our response

Thank you. The Siberian pine grows both on plains and on mountains. The range of this species spreads from the Mongolian forest-steppes to the northern latitudes. The SP is a less cold-resistant tree in comparison with larch (Larix sibirica, L. gmelinii). However, it can be found beyond the Polar Circle. In the mountains, the SP, fir, and spruce form the so-called “black belt” in the mountains (within elevations of 400–2,400 m). The SP, together with Larix sp. and fir, form the treeline ecotone in the mountains. Within the ecotone, SP is often found in mat and prostrate (krummholz) forms due to limitation by temperature and wind [27]. The upper elevation limit for SP is up to 2,400+ m. Because that species is moisture-sensitive and intolerant to low air humidity, it preferably occupies high-moisture areas (with precipitation up to 1000+ mm/year), but can survive in areas with lower (about 500 mm/year) precipitation. Due to relatively humid conditions in the habitat of Siberian pine, these forest burns less often in comparison with larch-dominant communities, although in the years of extreme drought burned areas may exceed a million ha [28]. Thus, different parts of the SP range, including different elevation belts in the mountains, are associated with different environmental limitations, and then the response of SP growth and survival to a warming climate may not be uniform.

76 does health status mean alive versus dead?  Or was the actual health of trees evaluated?  If so, how? In which sense?

Our response

Corrected sentence:  These changes may lead to a contrasting influence on Siberian pine growth and survival within different parts of the SP’s range, which are including different elevational belts in the mountains.

77 shouldn’t this be “are” as it is referring to belts?

Our response

Yes. Corrected.

85 Why exactly?

Our response

The paragraphs were revised.  “GI dependence on the eco-climate variables (air temperature, precipitation, soil moisture, air drought indexes and vapor pressure deficit, wind speed). We consider growth index dynamics as a proxy of tree vigor, as well as a predictor of potential decline and mortality of trees. We hypothesize that the response of SP growth and survival to changing climate are significantly different along the elevation gradient. We suggest that warming may switch limitation of trees growth by temperature to the limitation by moisture.

We aim to answer the following questions:

1. How does SP growth respond to changes in thermal and moisture regimes along the elevation gradient?
2. Does warming switch limitation of trees growth by temperature to limitation by moisture?
3. Does the survival of SP differ within different elevation belts? “

95 it should read “The study area”

Our response

Thanks.

133 Given mortality is a process, it needs to be followed over time.  Since the study did not do this, it difficult to see how mortality could be determined.  The abundance of dead trees could certainly be determined with a one-time measure.  Is this what was done?

Our response

Thank you. Corrected fragment: We randomly sampled wood cores at the DBH level by the Pressler borer. Cores of at least 20 trees were sampled around the centerpoint of each TS within an area of about 0.5 ha. For TS located on slopes, cores were taken within the ±10 m elevation range around the centerpoint of TS. The abundance of dead trees was determined within each TS.  

 

179 Is the “those” needed?

Our response

Corrected.

224 Do the authors mean “after this point in time” by the word “then”?

Our response

Thank you. Corrected.

230 this seems to contradict the text that follows.  Does this effect pertain to a particular time period?

Our response

Yes. Corrected: Wind adverse influence was observed within all elevational belts until the end of 1990^th (Figures 4e–6e). Meanwhile, because of the persistent decrease in the wind speed (Figure 2f), winds influence on growth has become insignificant in 2000-s (Figures 4e–6e).

235 The text in the figures is fuzzy?  Can this be improved?

Our response

We checked the text clarity. In original .doc text  is fine. Possibly, “fuzzy” caused by compression of original figures to .pdf. 

287 it should be “tree mortality” or “mortality of trees” but not “trees mortality”

Our response

Thank you.

305 “failed” is not the correct concept or word. 

Our response

Agree. Corrected: Since the tipping point in 2008, the “decliner’s” dependence on soil moisture became insignificant, whereas the “survivor’s” growth was still moisture-controlled (R² = 0.38).

316 “partial”?

Our response

Yes. Corrected

327 “dependence” is the wrong concept.

Our response

Yes, wrong. Corrected: Within all elevational belts, the trees’ growth switched from control by the air temperature to control by the moisture variables

335 “should based not” is extremely awkward.  Do the authors mean: “should not be based”?

Our response

Yes, aweful.  Corrected: Forest afforestation within the areas of Siberian pine mortality should not be based on the planting of Siberian pine but on tolerant species such as larch and Scots pine.   

336 “but on”?

Our response

Corrected.

Response to the Reviewer 2

This paper focus on a growth of Siberian pine (SP, Pinus sibirica) radial growth within the treeline ecotone. The main work is limited to experimental datasets, with no deeper theoretical insights and no development of the dependencies between growth variable and other explanatory variables.  The methodology presented here is well known from previous publications and is limited to the insights of an 'experienced forester'.

 Our response

General comments:

1. The abstract and introduction does not emphasize the novelty of the work and its contribution to the field of tree’s radial growth.

Our response

1. Thank you. An Abstract and Introduction revised.

Novelty:

The consequences of climate warming differed within different elevation belts. In the treeline ecotone, the tree’s growth was continuously increasing since the warming onset in the 1970-s, whereas in the lowlands, initial growth increase switched to a growth drop since the beginning of 2000-s with consequent partial mortality of Siberian pine forest. In the highlands, the tree’s growth was increasing until the end of 1980-s with the following-on growth fluctuations. 

The growth index control by air temperature and moisture variables included two phases. Firstly (from warming onset until the beginning of 2000-s), tree GI was positively correlated with elevated temperature, whereas correlations between precipitation and soil moisture were negative. During the second phase (since ca. 2000), negative correlations between GI and moisture variables switched to positive ones. The GI correlations with air temperature switched from positive to insignificant (with the exception of the beginning of the growth period).

The wind’s influence on the GI dramatically changed due to a continuous decrease in wind’s speed throughout the all study period. Thus, the significant negative influence of winds on the trees’ growth within all elevation belts turned to insignificant after the year 2000. 

Within the lowlands, warming-driven water stress in combination with bark-borers’ attacks led to the tree mortality, which suggests the retraction of the Siberian pine range in the lowlands of the Siberian Mountains.

 Forest afforestation within the areas of Siberian pine mortality should not be based on the planting of Siberian pine but on tolerant species such as larch (Larix sibirica) and Scots pine (Pinus sylvestris).   

 

2. References are mainly the work of the authors. Lack of overview and comparison of more modern methods.

Our response

We delete a couple of references to our papers. In fact, still few studies on that problem in Siberia.

We updated the list of papers which considered a broad view on the problem.

1. Hammond, W. M.; Williams, A. P.; Abatzoglou, J. T.; Adams H. D.; Klein T.; López R.; … Allen C. D. Global field observations of tree die-off reveal hotter-drought fingerprint for Earth’s forests. Commun. 2022, 13, 1761. https://doi.org/10.1038/s41467-022-29289-2
2. Kharuk, V. I.; Petrov, I. A.; Krivobokov, L. V.; Golyukov, A. S.; Dvinskaya, M. L.; Im S. T.; Shushpanov A. S.; Smith K. T. Larch response to warming in northern Siberia. Environ. Change 2023, 23, 17. https://doi.org/10.1007/s10113-022-02016-9
3. Rao, M. P.; Davi, N. K.; Magney, T. S.; Nachin, B.; Suran, B.; Varuolo-Clarke, A. M.; … Griffin, K. L. Approaching a thermal tipping point in the Eurasian boreal forest at its southern margin.  Earth Environ.2023, 4, 247. https://doi.org/10.1038/s43247-023-00910-6
4. Maher, C.; Hewitt, R. E.; Sullivan, P. F. Sufficient conditions for rapid range expansion of a boreal conifer. Nature 2022, 608, 546–551. https://doi.org/10.1038/s41586-022-05093-2
5. Watts, J.; Farina, M.; Kimball, J.; Schiferl, L.; Liu, Z.; Arndt, K.; … Oechel, W. Carbon uptake in Eurasian boreal forests dominates the high‐latitude net ecosystem carbon budget. Chan. Biol. 2023, 29(7), 1870–1889. https://doi.org/10.1111/gcb.16553
6. Anderegg, W. R. L.; Wu, C.; Acil, N.; Carvalhais, N.; Pugh, T. A. M.; Sadler, J. P.; Seidl, R. A climate risk analysis of Earth’s forests in the 21st century. Science 2022, 377(6610), 1099–1103. https://doi.org/10.1126/science.abp9723
7. The results do not support conclusions 1 and 2 (see Figure 3)..

Our response

Consider Fig. 3 as well as Fig, 4-5 and conclusions.

“The results do not support conclusions 1 and 2 (see Figure 3)”.

Disagree.

The consequences of climate warming differed within different elevation belts. In the treeline ecotone, the tree’s growth was continuously increasing since the warming onset in the 1970-s, whereas in the lowlands, initial growth increase switched to a growth drop since the beginning of 2000-s with consequent partial mortality of Siberian pine forest. In the highlands, the tree’s growth was increasing until the end of 1980-s with the following-on growth fluctuations. 

2. The growth index control by air temperature and moisture variables included two phases. Firstly (from warming onset until the beginning of 2000-s), tree GI was positively correlated with elevated temperature, whereas correlations between precipitation and soil moisture were negative. During the second phase (since ca. 2000), negative correlations between GI and moisture variables switched to positive ones. The GI correlations with air temperature switched from positive to insignificant (with the exception of the beginning of the growth period).
3. The wind’s influence on the GI dramatically changed due to a continuous decrease in wind’s speed throughout the all study period. Thus, the significant negative influence of winds on the trees’ growth within all elevation belts turned to insignificant after the year 2000.
4. Within the lowlands, warming-driven water stress in combination with bark-borers’ attacks led to the tree mortality, which suggests the retraction of the Siberian pine range in the lowlands of the Siberian Mountains. The projected drought increase will likely lead to the substitution of Siberian pine with drought-tolerant species.

 

Specific comments:

Line 76: ... growth ... Unclear, needs clarification.

Our response

Clarification: growth index (GI)

 Lines 83-84: The hypothesis was not confirmed.

Our response

Hypothesis clarification. “We hypothesize that the response of SP growth and survival to changing climate are significantly different along the elevational gradient. We suggest that warming may switch limitation of trees growth by temperature to the limitation by moisture”.

Results obtained (summarized in Conclusions) supported that hypothesis.

 

Lines 87, 90: Isn't question 3 covered by question 1?

Our response

1. Thank you. Revised text: How does SP growth respond to changes in thermal and moisture regimes along the elevation gradient?
2. Does warming switch limitation of trees growth by temperature to limitation by moisture?
3. Does the survival of SP differ within different elevational belts?

 

Line 97: ...  northward on about 300 km... Doesn't a distance of 300 km affect temperature, soil moisture etc.?

We checked climate variables along the norward direction of the Mountains. Yes, there are some variance. For example, difference in the air temperature less then 1 degree C.  Meanwhile, in the work we are analyzing elevational climate gradients, which is, as known, steeper. In addition, Siberian pine can be found on the distance less then 300 km (i.e., ca. 250 km) along the Kuznets Ridge, although that is not main issue).     

Our response

Line 161: … a negative exponential or negative linear… Drop the word 'negative' as it refers to the correlation coefficient.

Our response

Disagree. …”a negative exponential or negative linear”… is a generally accepted terms (e.g.,  Speer 2010).

 

Line 162: … age trend… Probably, radial increment trend.

Our response

Edited version: “age-related growth trend”.

Line 164: … R_t is the tree ring width in mm; G_t is the age trend...  Explain: R_t (probably – measured, G_t - ?).

Our response

Thank you. Corrected text: R_t is the tree ring width measured in mm.

G_t is a value of age-related growth trend (in mm), calculated in ARSTAN program by standard dendrochronological techniques and presented by a negative exponential or negative linear trendline. Age-related growth trend curve calculated for each individual tree-ring chronologies by standard dendrochronological technique.

Line 176: Fig 2. Why is the coefficient of determination used instead of the correlation coefficient?

Our response

There no any correlations on the Fig. 2. There only dynamics of eco-climate variables. And trends of those variables. Although formally correlations can be considered with years.

  Line 177: Edit point (e).

Thanks. Corrected: “Air temperature (a) and June VPD (e) are increasing, whereas summer precipitation (b)”.

Line 182: … significantly increasing… What could this mean?

Our response

1. The corrected sentence is “Air temperature and VPD (June) have been increasing since the warming onset in the 1970s, whereas summer precipitation and soil moisture have been decreasing since ca. 2000 year (Figures 2a, b, d).”

Our response

Line 186: … correlation of trees growth with PDSI...  Explain: What could this mean?

Our response

Thank you. We corrected that sentence. “As data analysis showed (section 3.3), VPD is a more informative variable in comparison with sc-PDSI and SPEI

Line 193: … tree growth within all elevation belts was increasing…. What could this mean?

Our response

Thank you. Corrected sentence “Since the warming onset, tree’s growth index has been increasing within all elevational belts. i.e., lowlands, highlands and treeline ecotone”.

 Line 194: … strong positive trend… What could this mean?

Our response

Thank you. Corrected sentence Within the treeline ecotone, Siberian pine growth indicated increasing trend throughout all time interval since 1970s (Figure 3a).

Line 200: … increasing growth rates...  Explain: What could this mean?

Our response

Corrected; i.e., trees with decreasing and increasing growth trends.

Line 203: … significant trends…. What could this mean?

Our response

Thank you. Corrected text: The growth index (GI) of the “decliners” cohort has been decreasing since 2000, whereas no negative trends of “survivors” GI was not observed (Figure 3c).

Line 306: … still moisture-dependent (R2=0.38)...  Explain: What could this mean?

Our response

Thank you. Corrected text: Since the tipping point in 2008, the “decliner’s” correlations with soil moisture became insignificant, whereas the “survivor’s” growth was controlled by moisture (R² = 0.38).

Our response

The article is written in English, but the meaning of words and concepts is open to interpretation. Therefore, the article must be carefully edited.

Our response

Totally agree. We did our best to improve our “Siberian version” of English.

 

Authors sincerely thanks Academic Editor and Reviewers for the valuable advices and constructive criticism that really help to improve our MS.

 

Sincerely,

1. Kharuk,

on behalf of authors

Response to the Academic Editor and Reviewers

Authors sincerely thanks Academic Editor for the advices that strongly help us to revise MS.

Significant changes in MS highlighted by red fonts.

 

 

Response to the Academic Editor

Our response

• I see that you made several improvements to your manuscript, congratulations.
  However, your first version says that you used  "linear Pearson’s correlations" and the new version says you used "Spearman correlation"..., but, Figure 4 in both versions shows exactly the same correlation values..., is that correct?
  
  

Our response Sorry. Just a “technical errata”. Figures with true "linear Pearson’s correlations" embedded to MS.

2) I think your Conclusions section can still be improved.

Our response

Agree. Edited version: 1. The consequences of climate warming differed within different elevation belts. In the treeline ecotone, the tree’s growth was continuously increasing since the warming onset in the 1970-s, whereas in the lowlands, initial growth increase switched to a growth drop since the beginning of 2000-s with consequent partial mortality of Siberian pine forest. In the highlands, the tree’s growth was increasing until the end of 1980-s with the following-on growth fluctuations. 

2. The growth index control by air temperature and moisture variables included two phases. Firstly (from warming onset until the beginning of 2000-s), tree GI was positively correlated with elevated temperature, whereas correlations between precipitation and soil moisture were negative. During the second phase (since ca. 2000), negative correlations between GI and moisture variables switched to positive ones. The GI correlations with air temperature switched from positive to insignificant (with the exception of the beginning of the growth period).
3. The wind’s influence on the GI dramatically changed due to a continuous decrease in wind’s speed throughout the all study period. Thus, the significant negative influence of winds on the trees’ growth within all elevation belts turned to insignificant after the year 2000.
4. Within the lowlands, warming-driven water stress in combination with bark-borers’ attacks led to the tree mortality, which suggests the retraction of the Siberian pine range in the lowlands of the Siberian Mountains. The projected drought increase will likely lead to the substitution of Siberian pine with drought-tolerant species.
5. Forest afforestation within the areas of Siberian pine mortality should not be based on the planting of Siberian pine but on tolerant species such as larch (Larix sibirica) and Scots pine (Pinus sylvestris).

Response to the Reviewer 1
General comments

While the manuscript describes a detailed examination of how a tree species is responding to a changing climate over time, it has a number of issues that need to be addressed.  There are two major concerns.  

• The first is that the study did not examine the health of the trees examined.  It did examine whether trees died, but has little to say about the rate of mortality.  To do that the process of mortality would have to be followed over time.  What was examined was cumulative mortality over some undetermined period of time.  This is of use, but not nearly as insightful as actually following trees as they die.  
• Second, the authors need to be more careful about describing relationships.  Given the nature of the work, these are correlational.  They certainly suggest some causes, but they certainly do no prove them (which is fine).  But the authors do need to be more careful about what they found and what they studied. 

Our response

• The abundance of dead trees was determined within each TS.  Please see also our response to line 133 note.

 

(2). Correlations does not equivalent of the “causal relationship.“  In edited MS we are more careful in that issue. 

Our response Surely we agree with that. Yes, we corrected text,

Throughout the manuscript there are odd word choices and concepts.  I have tried to indicate many of them below, but the manuscript needs to be reviewed in detail to eliminate as many of these problems as possible. 

Our response

Agree. In hundred percent. We did our best to eliminate errors throughout in MS. Thank you for advices how to improve text language and text clarity.  

Specific comments (line)

2 should this be “a warming climate”?  Isn’t the point the temperature is warming?

Our response

Yes, the warming means that air temperature is increasing.

14 given that health is an ambiguous term and not referred to in the subsequent text I suggest it be deleted.  A better word would be survival as the abstract mentions mortality. 

Agree. “Survival” is really better term.

23 “on the growth” should be “in growth”

Our response

Agree.

26 I am not sure “depending” makes sense.  One could say was influenced or controlled by a variable or given the observation nature of the work more correctly the response is correlated with a variable.

Our response

“Controlled” is a great term.

29 shouldn’t winds be possessive?  That is wind’s?

Corrected.

Our response

31 a future contraction? Or has it already been occurring?  It is not clear as written.

Our response

Thank you. Correction: The continuous decrease in tree growth and increased mortality indicating an occurring  contraction of the Siberian pine range within the lowlands belt in southern Siberia.

37 A more general initial paragraph might be helpful in setting the context for this introduction. 

Our response

Agree. Current climate change leads to both different positive and negative consequences in the Siberian taiga. Warming together with droughts caused an increase in fire frequency and area burned (mostly in larch-dominant communities growing in the zone of permafrost) and increase in pest-outbreaks frequency with consequent conifer species mortality as well as potential changes of tree species range within its southern margins [1–3]. Alongside that, an increase in the growth of tree species has been observed, and northward and uphill migration of conifer species (Siberian pine, Pinus sibirica Du Tour, Larix spp.) was documented, as well as a general increase in gross and net primary productivity within the Siberian forests and forest-tundra zones [4–6].       

56 related?

Our response

Corrected.

73-74 It would be helpful if this is more fully explained.  I gather the issue is that if the different parts of SP range are associated with different environmental limitations, then the response to a warming climate may not be uniform.

Our response

Thank you. The Siberian pine grows both on plains and on mountains. The range of this species spreads from the Mongolian forest-steppes to the northern latitudes. The SP is a less cold-resistant tree in comparison with larch (Larix sibirica, L. gmelinii). However, it can be found beyond the Polar Circle. In the mountains, the SP, fir, and spruce form the so-called “black belt” in the mountains (within elevations of 400–2,400 m). The SP, together with Larix sp. and fir, form the treeline ecotone in the mountains. Within the ecotone, SP is often found in mat and prostrate (krummholz) forms due to limitation by temperature and wind [27]. The upper elevation limit for SP is up to 2,400+ m. Because that species is moisture-sensitive and intolerant to low air humidity, it preferably occupies high-moisture areas (with precipitation up to 1000+ mm/year), but can survive in areas with lower (about 500 mm/year) precipitation. Due to relatively humid conditions in the habitat of Siberian pine, these forest burns less often in comparison with larch-dominant communities, although in the years of extreme drought burned areas may exceed a million ha [28]. Thus, different parts of the SP range, including different elevation belts in the mountains, are associated with different environmental limitations, and then the response of SP growth and survival to a warming climate may not be uniform.

76 does health status mean alive versus dead?  Or was the actual health of trees evaluated?  If so, how? In which sense?

Our response

Corrected sentence:  These changes may lead to a contrasting influence on Siberian pine growth and survival within different parts of the SP’s range, which are including different elevational belts in the mountains.

77 shouldn’t this be “are” as it is referring to belts?

Our response

Yes. Corrected.

85 Why exactly?

Our response

The paragraphs were revised.  “GI dependence on the eco-climate variables (air temperature, precipitation, soil moisture, air drought indexes and vapor pressure deficit, wind speed). We consider growth index dynamics as a proxy of tree vigor, as well as a predictor of potential decline and mortality of trees. We hypothesize that the response of SP growth and survival to changing climate are significantly different along the elevation gradient. We suggest that warming may switch limitation of trees growth by temperature to the limitation by moisture.

We aim to answer the following questions:

1. How does SP growth respond to changes in thermal and moisture regimes along the elevation gradient?
2. Does warming switch limitation of trees growth by temperature to limitation by moisture?
3. Does the survival of SP differ within different elevation belts? “

95 it should read “The study area”

Our response

Thanks.

133 Given mortality is a process, it needs to be followed over time.  Since the study did not do this, it difficult to see how mortality could be determined.  The abundance of dead trees could certainly be determined with a one-time measure.  Is this what was done?

Our response

Thank you. Corrected fragment: We randomly sampled wood cores at the DBH level by the Pressler borer. Cores of at least 20 trees were sampled around the centerpoint of each TS within an area of about 0.5 ha. For TS located on slopes, cores were taken within the ±10 m elevation range around the centerpoint of TS. The abundance of dead trees was determined within each TS.  

 

179 Is the “those” needed?

Our response

Corrected.

224 Do the authors mean “after this point in time” by the word “then”?

Our response

Thank you. Corrected.

230 this seems to contradict the text that follows.  Does this effect pertain to a particular time period?

Our response

Yes. Corrected: Wind adverse influence was observed within all elevational belts until the end of 1990^th (Figures 4e–6e). Meanwhile, because of the persistent decrease in the wind speed (Figure 2f), winds influence on growth has become insignificant in 2000-s (Figures 4e–6e).

235 The text in the figures is fuzzy?  Can this be improved?

Our response

We checked the text clarity. In original .doc text  is fine. Possibly, “fuzzy” caused by compression of original figures to .pdf. 

287 it should be “tree mortality” or “mortality of trees” but not “trees mortality”

Our response

Thank you.

305 “failed” is not the correct concept or word. 

Our response

Agree. Corrected: Since the tipping point in 2008, the “decliner’s” dependence on soil moisture became insignificant, whereas the “survivor’s” growth was still moisture-controlled (R² = 0.38).

316 “partial”?

Our response

Yes. Corrected

327 “dependence” is the wrong concept.

Our response

Yes, wrong. Corrected: Within all elevational belts, the trees’ growth switched from control by the air temperature to control by the moisture variables

335 “should based not” is extremely awkward.  Do the authors mean: “should not be based”?

Our response

Yes, aweful.  Corrected: Forest afforestation within the areas of Siberian pine mortality should not be based on the planting of Siberian pine but on tolerant species such as larch and Scots pine.   

336 “but on”?

Our response

Corrected.

Response to the Reviewer 2

This paper focus on a growth of Siberian pine (SP, Pinus sibirica) radial growth within the treeline ecotone. The main work is limited to experimental datasets, with no deeper theoretical insights and no development of the dependencies between growth variable and other explanatory variables.  The methodology presented here is well known from previous publications and is limited to the insights of an 'experienced forester'.

 Our response

General comments:

1. The abstract and introduction does not emphasize the novelty of the work and its contribution to the field of tree’s radial growth.

Our response

1. Thank you. An Abstract and Introduction revised.

Novelty:

The consequences of climate warming differed within different elevation belts. In the treeline ecotone, the tree’s growth was continuously increasing since the warming onset in the 1970-s, whereas in the lowlands, initial growth increase switched to a growth drop since the beginning of 2000-s with consequent partial mortality of Siberian pine forest. In the highlands, the tree’s growth was increasing until the end of 1980-s with the following-on growth fluctuations. 

The growth index control by air temperature and moisture variables included two phases. Firstly (from warming onset until the beginning of 2000-s), tree GI was positively correlated with elevated temperature, whereas correlations between precipitation and soil moisture were negative. During the second phase (since ca. 2000), negative correlations between GI and moisture variables switched to positive ones. The GI correlations with air temperature switched from positive to insignificant (with the exception of the beginning of the growth period).

The wind’s influence on the GI dramatically changed due to a continuous decrease in wind’s speed throughout the all study period. Thus, the significant negative influence of winds on the trees’ growth within all elevation belts turned to insignificant after the year 2000. 

Within the lowlands, warming-driven water stress in combination with bark-borers’ attacks led to the tree mortality, which suggests the retraction of the Siberian pine range in the lowlands of the Siberian Mountains.

 Forest afforestation within the areas of Siberian pine mortality should not be based on the planting of Siberian pine but on tolerant species such as larch (Larix sibirica) and Scots pine (Pinus sylvestris).   

 

2. References are mainly the work of the authors. Lack of overview and comparison of more modern methods.

Our response

We delete a couple of references to our papers. In fact, still few studies on that problem in Siberia.

We updated the list of papers which considered a broad view on the problem.

1. Hammond, W. M.; Williams, A. P.; Abatzoglou, J. T.; Adams H. D.; Klein T.; López R.; … Allen C. D. Global field observations of tree die-off reveal hotter-drought fingerprint for Earth’s forests. Commun. 2022, 13, 1761. https://doi.org/10.1038/s41467-022-29289-2
2. Kharuk, V. I.; Petrov, I. A.; Krivobokov, L. V.; Golyukov, A. S.; Dvinskaya, M. L.; Im S. T.; Shushpanov A. S.; Smith K. T. Larch response to warming in northern Siberia. Environ. Change 2023, 23, 17. https://doi.org/10.1007/s10113-022-02016-9
3. Rao, M. P.; Davi, N. K.; Magney, T. S.; Nachin, B.; Suran, B.; Varuolo-Clarke, A. M.; … Griffin, K. L. Approaching a thermal tipping point in the Eurasian boreal forest at its southern margin.  Earth Environ.2023, 4, 247. https://doi.org/10.1038/s43247-023-00910-6
4. Maher, C.; Hewitt, R. E.; Sullivan, P. F. Sufficient conditions for rapid range expansion of a boreal conifer. Nature 2022, 608, 546–551. https://doi.org/10.1038/s41586-022-05093-2
5. Watts, J.; Farina, M.; Kimball, J.; Schiferl, L.; Liu, Z.; Arndt, K.; … Oechel, W. Carbon uptake in Eurasian boreal forests dominates the high‐latitude net ecosystem carbon budget. Chan. Biol. 2023, 29(7), 1870–1889. https://doi.org/10.1111/gcb.16553
6. Anderegg, W. R. L.; Wu, C.; Acil, N.; Carvalhais, N.; Pugh, T. A. M.; Sadler, J. P.; Seidl, R. A climate risk analysis of Earth’s forests in the 21st century. Science 2022, 377(6610), 1099–1103. https://doi.org/10.1126/science.abp9723
7. The results do not support conclusions 1 and 2 (see Figure 3)..

Our response

Consider Fig. 3 as well as Fig, 4-5 and conclusions.

“The results do not support conclusions 1 and 2 (see Figure 3)”.

Disagree.

The consequences of climate warming differed within different elevation belts. In the treeline ecotone, the tree’s growth was continuously increasing since the warming onset in the 1970-s, whereas in the lowlands, initial growth increase switched to a growth drop since the beginning of 2000-s with consequent partial mortality of Siberian pine forest. In the highlands, the tree’s growth was increasing until the end of 1980-s with the following-on growth fluctuations. 

2. The growth index control by air temperature and moisture variables included two phases. Firstly (from warming onset until the beginning of 2000-s), tree GI was positively correlated with elevated temperature, whereas correlations between precipitation and soil moisture were negative. During the second phase (since ca. 2000), negative correlations between GI and moisture variables switched to positive ones. The GI correlations with air temperature switched from positive to insignificant (with the exception of the beginning of the growth period).
3. The wind’s influence on the GI dramatically changed due to a continuous decrease in wind’s speed throughout the all study period. Thus, the significant negative influence of winds on the trees’ growth within all elevation belts turned to insignificant after the year 2000.
4. Within the lowlands, warming-driven water stress in combination with bark-borers’ attacks led to the tree mortality, which suggests the retraction of the Siberian pine range in the lowlands of the Siberian Mountains. The projected drought increase will likely lead to the substitution of Siberian pine with drought-tolerant species.

 

Specific comments:

Line 76: ... growth ... Unclear, needs clarification.

Our response

Clarification: growth index (GI)

 Lines 83-84: The hypothesis was not confirmed.

Our response

Hypothesis clarification. “We hypothesize that the response of SP growth and survival to changing climate are significantly different along the elevational gradient. We suggest that warming may switch limitation of trees growth by temperature to the limitation by moisture”.

Results obtained (summarized in Conclusions) supported that hypothesis.

 

Lines 87, 90: Isn't question 3 covered by question 1?

Our response

1. Thank you. Revised text: How does SP growth respond to changes in thermal and moisture regimes along the elevation gradient?
2. Does warming switch limitation of trees growth by temperature to limitation by moisture?
3. Does the survival of SP differ within different elevational belts?

 

Line 97: ...  northward on about 300 km... Doesn't a distance of 300 km affect temperature, soil moisture etc.?

We checked climate variables along the norward direction of the Mountains. Yes, there are some variance. For example, difference in the air temperature less then 1 degree C.  Meanwhile, in the work we are analyzing elevational climate gradients, which is, as known, steeper. In addition, Siberian pine can be found on the distance less then 300 km (i.e., ca. 250 km) along the Kuznets Ridge, although that is not main issue).     

Our response

Line 161: … a negative exponential or negative linear… Drop the word 'negative' as it refers to the correlation coefficient.

Our response

Disagree. …”a negative exponential or negative linear”… is a generally accepted terms (e.g.,  Speer 2010).

 

Line 162: … age trend… Probably, radial increment trend.

Our response

Edited version: “age-related growth trend”.

Line 164: … R_t is the tree ring width in mm; G_t is the age trend...  Explain: R_t (probably – measured, G_t - ?).

Our response

Thank you. Corrected text: R_t is the tree ring width measured in mm.

G_t is a value of age-related growth trend (in mm), calculated in ARSTAN program by standard dendrochronological techniques and presented by a negative exponential or negative linear trendline. Age-related growth trend curve calculated for each individual tree-ring chronologies by standard dendrochronological technique.

Line 176: Fig 2. Why is the coefficient of determination used instead of the correlation coefficient?

Our response

There no any correlations on the Fig. 2. There only dynamics of eco-climate variables. And trends of those variables. Although formally correlations can be considered with years.

  Line 177: Edit point (e).

Thanks. Corrected: “Air temperature (a) and June VPD (e) are increasing, whereas summer precipitation (b)”.

Line 182: … significantly increasing… What could this mean?

Our response

1. The corrected sentence is “Air temperature and VPD (June) have been increasing since the warming onset in the 1970s, whereas summer precipitation and soil moisture have been decreasing since ca. 2000 year (Figures 2a, b, d).”

Our response

Line 186: … correlation of trees growth with PDSI...  Explain: What could this mean?

Our response

Thank you. We corrected that sentence. “As data analysis showed (section 3.3), VPD is a more informative variable in comparison with sc-PDSI and SPEI

Line 193: … tree growth within all elevation belts was increasing…. What could this mean?

Our response

Thank you. Corrected sentence “Since the warming onset, tree’s growth index has been increasing within all elevational belts. i.e., lowlands, highlands and treeline ecotone”.

 Line 194: … strong positive trend… What could this mean?

Our response

Thank you. Corrected sentence Within the treeline ecotone, Siberian pine growth indicated increasing trend throughout all time interval since 1970s (Figure 3a).

Line 200: … increasing growth rates...  Explain: What could this mean?

Our response

Corrected; i.e., trees with decreasing and increasing growth trends.

Line 203: … significant trends…. What could this mean?

Our response

Thank you. Corrected text: The growth index (GI) of the “decliners” cohort has been decreasing since 2000, whereas no negative trends of “survivors” GI was not observed (Figure 3c).

Line 306: … still moisture-dependent (R2=0.38)...  Explain: What could this mean?

Our response

Thank you. Corrected text: Since the tipping point in 2008, the “decliner’s” correlations with soil moisture became insignificant, whereas the “survivor’s” growth was controlled by moisture (R² = 0.38).

Our response

The article is written in English, but the meaning of words and concepts is open to interpretation. Therefore, the article must be carefully edited.

Our response

Totally agree. We did our best to improve our “Siberian version” of English.

 

Authors sincerely thanks Academic Editor and Reviewers for the valuable advices and constructive criticism that really help to improve our MS.

 

Sincerely,

1. Kharuk,

on behalf of authors

 

Reviewer 2 Report

Comments and Suggestions for Authors

Review of manuscript

Mountain Taiga in Warm Climate: Contrast of Siberian Pine Growth along an Elevation Gradient

by Viacheslav I. Kharuk et al.

 

This paper focus on a growth of Siberian pine (SP, Pinus sibirica) radial growth within the treeline ecotone. The main work is limited to experimental datasets, with no deeper theoretical insights and no development of the dependencies between growth variable and other explanatory variables.  The methodology presented here is well known from previous publications and is limited to the insights of an 'experienced forester'.

 

General comments:

1.      The abstract and introduction does not emphasize the novelty of the work and its contribution to the field of tree’s radial growth.

2.      References are mainly the work of the authors. Lack of overview and comparison of more modern methods.

3.      The results do not support conclusions 1 and 2 (see Figure 3)..

 

Specific comments:

Line 76: ... growth ... Unclear, needs clarification.

Lines 83-84: The hypothesis was not confirmed.

Lines 87, 90: Isn't question 3 covered by question 1?

Line 97: ...  northward on about 300 km... Doesn't a distance of 300 km affect temperature, soil moisture etc.?

Line 161: … a negative exponential or negative linear… Drop the word 'negative' as it refers to the correlation coefficient.

Line 162: … age trend… Probably, radial increment trend.

Line 164: … R_t is the tree ring width in mm; G_t is the age trend...  Explain: R_t (probably – measured, G_t - ?).

Line 176: Fig 2. Why is the coefficient of determination used instead of the correlation coefficient?

 

Line 177: Edit point (e).

Line 182: … significantly increasing… What could this mean?

 

Line 186: … correlation of trees growth with PDSI...  Explain: What could this mean?

Line 193: … tree growth within all elevation belts was increasing…. What could this mean?

Line 194: … strong positive trend… What could this mean?

Line 200: … increasing growth rates...  Explain: What could this mean?

Line 203: … significant trends…. What could this mean?

Line 306: … still moisture-dependent (R2=0.38)...  Explain: What could this mean?

The article is written in English, but the meaning of words and concepts is open to interpretation. Therefore, the article must be carefully edited.

Comments on the Quality of English Language

The article is written in English, but the meaning of words and concepts is open to interpretation. Therefore, the article must be carefully edited.

Author Response

Response to the Academic Editor and Reviewers

Authors sincerely thanks Academic Editor for the advices that strongly help us to revise MS.

Significant changes in MS highlighted by red fonts.

 

 

Response to the Academic Editor

Our response

• I see that you made several improvements to your manuscript, congratulations.
  However, your first version says that you used  "linear Pearson’s correlations" and the new version says you used "Spearman correlation"..., but, Figure 4 in both versions shows exactly the same correlation values..., is that correct?
  
  

Our response Sorry. Just a “technical errata”. Figures with true "linear Pearson’s correlations" embedded to MS.

2) I think your Conclusions section can still be improved.

Our response

Agree. Edited version: 1. The consequences of climate warming differed within different elevation belts. In the treeline ecotone, the tree’s growth was continuously increasing since the warming onset in the 1970-s, whereas in the lowlands, initial growth increase switched to a growth drop since the beginning of 2000-s with consequent partial mortality of Siberian pine forest. In the highlands, the tree’s growth was increasing until the end of 1980-s with the following-on growth fluctuations. 

2. The growth index control by air temperature and moisture variables included two phases. Firstly (from warming onset until the beginning of 2000-s), tree GI was positively correlated with elevated temperature, whereas correlations between precipitation and soil moisture were negative. During the second phase (since ca. 2000), negative correlations between GI and moisture variables switched to positive ones. The GI correlations with air temperature switched from positive to insignificant (with the exception of the beginning of the growth period).
3. The wind’s influence on the GI dramatically changed due to a continuous decrease in wind’s speed throughout the all study period. Thus, the significant negative influence of winds on the trees’ growth within all elevation belts turned to insignificant after the year 2000.
4. Within the lowlands, warming-driven water stress in combination with bark-borers’ attacks led to the tree mortality, which suggests the retraction of the Siberian pine range in the lowlands of the Siberian Mountains. The projected drought increase will likely lead to the substitution of Siberian pine with drought-tolerant species.
5. Forest afforestation within the areas of Siberian pine mortality should not be based on the planting of Siberian pine but on tolerant species such as larch (Larix sibirica) and Scots pine (Pinus sylvestris).

Response to the Reviewer 1
General comments

While the manuscript describes a detailed examination of how a tree species is responding to a changing climate over time, it has a number of issues that need to be addressed.  There are two major concerns.  

• The first is that the study did not examine the health of the trees examined.  It did examine whether trees died, but has little to say about the rate of mortality.  To do that the process of mortality would have to be followed over time.  What was examined was cumulative mortality over some undetermined period of time.  This is of use, but not nearly as insightful as actually following trees as they die.  
• Second, the authors need to be more careful about describing relationships.  Given the nature of the work, these are correlational.  They certainly suggest some causes, but they certainly do no prove them (which is fine).  But the authors do need to be more careful about what they found and what they studied. 

Our response

• The abundance of dead trees was determined within each TS.  Please see also our response to line 133 note.

 

(2). Correlations does not equivalent of the “causal relationship.“  In edited MS we are more careful in that issue. 

Our response Surely we agree with that. Yes, we corrected text,

Throughout the manuscript there are odd word choices and concepts.  I have tried to indicate many of them below, but the manuscript needs to be reviewed in detail to eliminate as many of these problems as possible. 

Our response

Agree. In hundred percent. We did our best to eliminate errors throughout in MS. Thank you for advices how to improve text language and text clarity.  

Specific comments (line)

2 should this be “a warming climate”?  Isn’t the point the temperature is warming?

Our response

Yes, the warming means that air temperature is increasing.

14 given that health is an ambiguous term and not referred to in the subsequent text I suggest it be deleted.  A better word would be survival as the abstract mentions mortality. 

Agree. “Survival” is really better term.

23 “on the growth” should be “in growth”

Our response

Agree.

26 I am not sure “depending” makes sense.  One could say was influenced or controlled by a variable or given the observation nature of the work more correctly the response is correlated with a variable.

Our response

“Controlled” is a great term.

29 shouldn’t winds be possessive?  That is wind’s?

Corrected.

Our response

31 a future contraction? Or has it already been occurring?  It is not clear as written.

Our response

Thank you. Correction: The continuous decrease in tree growth and increased mortality indicating an occurring  contraction of the Siberian pine range within the lowlands belt in southern Siberia.

37 A more general initial paragraph might be helpful in setting the context for this introduction. 

Our response

Agree. Current climate change leads to both different positive and negative consequences in the Siberian taiga. Warming together with droughts caused an increase in fire frequency and area burned (mostly in larch-dominant communities growing in the zone of permafrost) and increase in pest-outbreaks frequency with consequent conifer species mortality as well as potential changes of tree species range within its southern margins [1–3]. Alongside that, an increase in the growth of tree species has been observed, and northward and uphill migration of conifer species (Siberian pine, Pinus sibirica Du Tour, Larix spp.) was documented, as well as a general increase in gross and net primary productivity within the Siberian forests and forest-tundra zones [4–6].       

56 related?

Our response

Corrected.

73-74 It would be helpful if this is more fully explained.  I gather the issue is that if the different parts of SP range are associated with different environmental limitations, then the response to a warming climate may not be uniform.

Our response

Thank you. The Siberian pine grows both on plains and on mountains. The range of this species spreads from the Mongolian forest-steppes to the northern latitudes. The SP is a less cold-resistant tree in comparison with larch (Larix sibirica, L. gmelinii). However, it can be found beyond the Polar Circle. In the mountains, the SP, fir, and spruce form the so-called “black belt” in the mountains (within elevations of 400–2,400 m). The SP, together with Larix sp. and fir, form the treeline ecotone in the mountains. Within the ecotone, SP is often found in mat and prostrate (krummholz) forms due to limitation by temperature and wind [27]. The upper elevation limit for SP is up to 2,400+ m. Because that species is moisture-sensitive and intolerant to low air humidity, it preferably occupies high-moisture areas (with precipitation up to 1000+ mm/year), but can survive in areas with lower (about 500 mm/year) precipitation. Due to relatively humid conditions in the habitat of Siberian pine, these forest burns less often in comparison with larch-dominant communities, although in the years of extreme drought burned areas may exceed a million ha [28]. Thus, different parts of the SP range, including different elevation belts in the mountains, are associated with different environmental limitations, and then the response of SP growth and survival to a warming climate may not be uniform.

76 does health status mean alive versus dead?  Or was the actual health of trees evaluated?  If so, how? In which sense?

Our response

Corrected sentence:  These changes may lead to a contrasting influence on Siberian pine growth and survival within different parts of the SP’s range, which are including different elevational belts in the mountains.

77 shouldn’t this be “are” as it is referring to belts?

Our response

Yes. Corrected.

85 Why exactly?

Our response

The paragraphs were revised.  “GI dependence on the eco-climate variables (air temperature, precipitation, soil moisture, air drought indexes and vapor pressure deficit, wind speed). We consider growth index dynamics as a proxy of tree vigor, as well as a predictor of potential decline and mortality of trees. We hypothesize that the response of SP growth and survival to changing climate are significantly different along the elevation gradient. We suggest that warming may switch limitation of trees growth by temperature to the limitation by moisture.

We aim to answer the following questions:

1. How does SP growth respond to changes in thermal and moisture regimes along the elevation gradient?
2. Does warming switch limitation of trees growth by temperature to limitation by moisture?
3. Does the survival of SP differ within different elevation belts? “

95 it should read “The study area”

Our response

Thanks.

133 Given mortality is a process, it needs to be followed over time.  Since the study did not do this, it difficult to see how mortality could be determined.  The abundance of dead trees could certainly be determined with a one-time measure.  Is this what was done?

Our response

Thank you. Corrected fragment: We randomly sampled wood cores at the DBH level by the Pressler borer. Cores of at least 20 trees were sampled around the centerpoint of each TS within an area of about 0.5 ha. For TS located on slopes, cores were taken within the ±10 m elevation range around the centerpoint of TS. The abundance of dead trees was determined within each TS.  

 

179 Is the “those” needed?

Our response

Corrected.

224 Do the authors mean “after this point in time” by the word “then”?

Our response

Thank you. Corrected.

230 this seems to contradict the text that follows.  Does this effect pertain to a particular time period?

Our response

Yes. Corrected: Wind adverse influence was observed within all elevational belts until the end of 1990^th (Figures 4e–6e). Meanwhile, because of the persistent decrease in the wind speed (Figure 2f), winds influence on growth has become insignificant in 2000-s (Figures 4e–6e).

235 The text in the figures is fuzzy?  Can this be improved?

Our response

We checked the text clarity. In original .doc text  is fine. Possibly, “fuzzy” caused by compression of original figures to .pdf. 

287 it should be “tree mortality” or “mortality of trees” but not “trees mortality”

Our response

Thank you.

305 “failed” is not the correct concept or word. 

Our response

Agree. Corrected: Since the tipping point in 2008, the “decliner’s” dependence on soil moisture became insignificant, whereas the “survivor’s” growth was still moisture-controlled (R² = 0.38).

316 “partial”?

Our response

Yes. Corrected

327 “dependence” is the wrong concept.

Our response

Yes, wrong. Corrected: Within all elevational belts, the trees’ growth switched from control by the air temperature to control by the moisture variables

335 “should based not” is extremely awkward.  Do the authors mean: “should not be based”?

Our response

Yes, aweful.  Corrected: Forest afforestation within the areas of Siberian pine mortality should not be based on the planting of Siberian pine but on tolerant species such as larch and Scots pine.   

336 “but on”?

Our response

Corrected.

Response to the Reviewer 2

This paper focus on a growth of Siberian pine (SP, Pinus sibirica) radial growth within the treeline ecotone. The main work is limited to experimental datasets, with no deeper theoretical insights and no development of the dependencies between growth variable and other explanatory variables.  The methodology presented here is well known from previous publications and is limited to the insights of an 'experienced forester'.

 Our response

General comments:

1. The abstract and introduction does not emphasize the novelty of the work and its contribution to the field of tree’s radial growth.

Our response

1. Thank you. An Abstract and Introduction revised.

Novelty:

The consequences of climate warming differed within different elevation belts. In the treeline ecotone, the tree’s growth was continuously increasing since the warming onset in the 1970-s, whereas in the lowlands, initial growth increase switched to a growth drop since the beginning of 2000-s with consequent partial mortality of Siberian pine forest. In the highlands, the tree’s growth was increasing until the end of 1980-s with the following-on growth fluctuations. 

The growth index control by air temperature and moisture variables included two phases. Firstly (from warming onset until the beginning of 2000-s), tree GI was positively correlated with elevated temperature, whereas correlations between precipitation and soil moisture were negative. During the second phase (since ca. 2000), negative correlations between GI and moisture variables switched to positive ones. The GI correlations with air temperature switched from positive to insignificant (with the exception of the beginning of the growth period).

The wind’s influence on the GI dramatically changed due to a continuous decrease in wind’s speed throughout the all study period. Thus, the significant negative influence of winds on the trees’ growth within all elevation belts turned to insignificant after the year 2000. 

Within the lowlands, warming-driven water stress in combination with bark-borers’ attacks led to the tree mortality, which suggests the retraction of the Siberian pine range in the lowlands of the Siberian Mountains.

 Forest afforestation within the areas of Siberian pine mortality should not be based on the planting of Siberian pine but on tolerant species such as larch (Larix sibirica) and Scots pine (Pinus sylvestris).   

 

2. References are mainly the work of the authors. Lack of overview and comparison of more modern methods.

Our response

We delete a couple of references to our papers. In fact, still few studies on that problem in Siberia.

We updated the list of papers which considered a broad view on the problem.

1. Hammond, W. M.; Williams, A. P.; Abatzoglou, J. T.; Adams H. D.; Klein T.; López R.; … Allen C. D. Global field observations of tree die-off reveal hotter-drought fingerprint for Earth’s forests. Commun. 2022, 13, 1761. https://doi.org/10.1038/s41467-022-29289-2
2. Kharuk, V. I.; Petrov, I. A.; Krivobokov, L. V.; Golyukov, A. S.; Dvinskaya, M. L.; Im S. T.; Shushpanov A. S.; Smith K. T. Larch response to warming in northern Siberia. Environ. Change 2023, 23, 17. https://doi.org/10.1007/s10113-022-02016-9
3. Rao, M. P.; Davi, N. K.; Magney, T. S.; Nachin, B.; Suran, B.; Varuolo-Clarke, A. M.; … Griffin, K. L. Approaching a thermal tipping point in the Eurasian boreal forest at its southern margin.  Earth Environ.2023, 4, 247. https://doi.org/10.1038/s43247-023-00910-6
4. Maher, C.; Hewitt, R. E.; Sullivan, P. F. Sufficient conditions for rapid range expansion of a boreal conifer. Nature 2022, 608, 546–551. https://doi.org/10.1038/s41586-022-05093-2
5. Watts, J.; Farina, M.; Kimball, J.; Schiferl, L.; Liu, Z.; Arndt, K.; … Oechel, W. Carbon uptake in Eurasian boreal forests dominates the high‐latitude net ecosystem carbon budget. Chan. Biol. 2023, 29(7), 1870–1889. https://doi.org/10.1111/gcb.16553
6. Anderegg, W. R. L.; Wu, C.; Acil, N.; Carvalhais, N.; Pugh, T. A. M.; Sadler, J. P.; Seidl, R. A climate risk analysis of Earth’s forests in the 21st century. Science 2022, 377(6610), 1099–1103. https://doi.org/10.1126/science.abp9723
7. The results do not support conclusions 1 and 2 (see Figure 3)..

Our response

Consider Fig. 3 as well as Fig, 4-5 and conclusions.

“The results do not support conclusions 1 and 2 (see Figure 3)”.

Disagree.

The consequences of climate warming differed within different elevation belts. In the treeline ecotone, the tree’s growth was continuously increasing since the warming onset in the 1970-s, whereas in the lowlands, initial growth increase switched to a growth drop since the beginning of 2000-s with consequent partial mortality of Siberian pine forest. In the highlands, the tree’s growth was increasing until the end of 1980-s with the following-on growth fluctuations. 

2. The growth index control by air temperature and moisture variables included two phases. Firstly (from warming onset until the beginning of 2000-s), tree GI was positively correlated with elevated temperature, whereas correlations between precipitation and soil moisture were negative. During the second phase (since ca. 2000), negative correlations between GI and moisture variables switched to positive ones. The GI correlations with air temperature switched from positive to insignificant (with the exception of the beginning of the growth period).
3. The wind’s influence on the GI dramatically changed due to a continuous decrease in wind’s speed throughout the all study period. Thus, the significant negative influence of winds on the trees’ growth within all elevation belts turned to insignificant after the year 2000.
4. Within the lowlands, warming-driven water stress in combination with bark-borers’ attacks led to the tree mortality, which suggests the retraction of the Siberian pine range in the lowlands of the Siberian Mountains. The projected drought increase will likely lead to the substitution of Siberian pine with drought-tolerant species.

 

Specific comments:

Line 76: ... growth ... Unclear, needs clarification.

Our response

Clarification: growth index (GI)

 Lines 83-84: The hypothesis was not confirmed.

Our response

Hypothesis clarification. “We hypothesize that the response of SP growth and survival to changing climate are significantly different along the elevational gradient. We suggest that warming may switch limitation of trees growth by temperature to the limitation by moisture”.

Results obtained (summarized in Conclusions) supported that hypothesis.

 

Lines 87, 90: Isn't question 3 covered by question 1?

Our response

1. Thank you. Revised text: How does SP growth respond to changes in thermal and moisture regimes along the elevation gradient?
2. Does warming switch limitation of trees growth by temperature to limitation by moisture?
3. Does the survival of SP differ within different elevational belts?

 

Line 97: ...  northward on about 300 km... Doesn't a distance of 300 km affect temperature, soil moisture etc.?

We checked climate variables along the norward direction of the Mountains. Yes, there are some variance. For example, difference in the air temperature less then 1 degree C.  Meanwhile, in the work we are analyzing elevational climate gradients, which is, as known, steeper. In addition, Siberian pine can be found on the distance less then 300 km (i.e., ca. 250 km) along the Kuznets Ridge, although that is not main issue).     

Our response

Line 161: … a negative exponential or negative linear… Drop the word 'negative' as it refers to the correlation coefficient.

Our response

Disagree. …”a negative exponential or negative linear”… is a generally accepted terms (e.g.,  Speer 2010).

 

Line 162: … age trend… Probably, radial increment trend.

Our response

Edited version: “age-related growth trend”.

Line 164: … R_t is the tree ring width in mm; G_t is the age trend...  Explain: R_t (probably – measured, G_t - ?).

Our response

Thank you. Corrected text: R_t is the tree ring width measured in mm.

G_t is a value of age-related growth trend (in mm), calculated in ARSTAN program by standard dendrochronological techniques and presented by a negative exponential or negative linear trendline. Age-related growth trend curve calculated for each individual tree-ring chronologies by standard dendrochronological technique.

Line 176: Fig 2. Why is the coefficient of determination used instead of the correlation coefficient?

Our response

There no any correlations on the Fig. 2. There only dynamics of eco-climate variables. And trends of those variables. Although formally correlations can be considered with years.

  Line 177: Edit point (e).

Thanks. Corrected: “Air temperature (a) and June VPD (e) are increasing, whereas summer precipitation (b)”.

Line 182: … significantly increasing… What could this mean?

Our response

1. The corrected sentence is “Air temperature and VPD (June) have been increasing since the warming onset in the 1970s, whereas summer precipitation and soil moisture have been decreasing since ca. 2000 year (Figures 2a, b, d).”

Our response

Line 186: … correlation of trees growth with PDSI...  Explain: What could this mean?

Our response

Thank you. We corrected that sentence. “As data analysis showed (section 3.3), VPD is a more informative variable in comparison with sc-PDSI and SPEI

Line 193: … tree growth within all elevation belts was increasing…. What could this mean?

Our response

Thank you. Corrected sentence “Since the warming onset, tree’s growth index has been increasing within all elevational belts. i.e., lowlands, highlands and treeline ecotone”.

 Line 194: … strong positive trend… What could this mean?

Our response

Thank you. Corrected sentence Within the treeline ecotone, Siberian pine growth indicated increasing trend throughout all time interval since 1970s (Figure 3a).

Line 200: … increasing growth rates...  Explain: What could this mean?

Our response

Corrected; i.e., trees with decreasing and increasing growth trends.

Line 203: … significant trends…. What could this mean?

Our response

Thank you. Corrected text: The growth index (GI) of the “decliners” cohort has been decreasing since 2000, whereas no negative trends of “survivors” GI was not observed (Figure 3c).

Line 306: … still moisture-dependent (R2=0.38)...  Explain: What could this mean?

Our response

Thank you. Corrected text: Since the tipping point in 2008, the “decliner’s” correlations with soil moisture became insignificant, whereas the “survivor’s” growth was controlled by moisture (R² = 0.38).

Our response

The article is written in English, but the meaning of words and concepts is open to interpretation. Therefore, the article must be carefully edited.

Our response

Totally agree. We did our best to improve our “Siberian version” of English.

 

Authors sincerely thanks Academic Editor and Reviewers for the valuable advices and constructive criticism that really help to improve our MS.

 

Sincerely,

1. Kharuk,

on behalf of authors

 

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

General comments

The authors have incorporated most if not all my suggestions in their revision.  I believe the manuscript has been significantly improved. There remain just a few additional revisions to consider as specified below.

Specific comments (line)

27 By “until begin” do the authors mean “by the beginning”?

36 species can be tolerant to many things.  Is the main concern drought tolerance? It would help if this could be made clearer.

42 I don’t think “different” is needed. 

59 “the part of “dark-needle conifers” taiga forests” would read better as “the “dark-needle conifers” part of the taiga forests”

98 It should be “these forests burn” instead of “these forest burns”. 

341 “all” is not needed.  Throughout implies all.

386 The authors might consider this revision “replanting of Siberian pine but on planting drought tolerant species such as larch”.  Also all Latin names should be in italics here and throughout the manuscript.

 

 

 

Comments on the Quality of English Language

I have made specific suggestions on the comments to authors. 

Author Response

Response to Reviewer 1

General comments

The authors have incorporated most if not all my suggestions in their revision.  I believe the manuscript has been significantly improved. There remain just a few additional revisions to consider as specified below.

Our Response

Thank you.

Specific comments (line)

27 By “until begin” do the authors mean “by the beginning”?

36 species can be tolerant to many things.  Is the main concern drought tolerance? It would help if this could be made clearer.

42 I don’t think “different” is needed. 

59 “the part of “dark-needle conifers” taiga forests” would read better as “the “dark-needle conifers” part of the taiga forests”

Our Response

Outstanding!

98 It should be “these forests burn” instead of “these forest burns”. 

341 “all” is not needed.  Throughout implies all.

386 The authors might consider this revision “replanting of Siberian pine but on planting drought tolerant species such as larch”.  Also all Latin names should be in italics here and throughout the manuscript.

Our Response

Thank you.

All suggested edits accepted.

 

Authors sincerely thanks the Reviewer for advices and constructive criticism that strongly help us since the beginning until very end of the MS revision.

Reviewer 2 Report

Comments and Suggestions for Authors

Manuscript title:  Mountain Taiga in a Warming Climate: Contrast of Siberian Pine Growth along an Elevation Gradient

The authors answered all the questions. The paper can be accepted.

Comments on the Quality of English Language

The article is written in plain English.

Author Response

Reviewer 2 notes:

The authors answered all the questions. The paper can be accepted.

Comments on the Quality of English Language

The article is written in plain English.

Response to Reviewer 2

Authors sincerely thanks Reviewer for advices that strongly help us since the beginning until very end of MS revision.

Kind regards,

V. Kharuk