Climatic Warming Caused a Transition in Tree Growth Sensitivity from Temperature to Moisture Conditions: Evidence from Multi-Species Tree-Ring Data in the Southeastern Tibetan Plateau

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The paper “Climatic Warming Had Caused Transition of Tree Growth Sensitivity From Temperature to Moisture Condition: Evidence From Muti-species Tree-ring Data of Southeastern Tibetan  Plateau” focuses at the statistical analyses of ring width of four conifer species growing at high elevation of Tibetan Plateau. Using standard tree ring technique and simple statistical correlations of tree rings and meteorological data the authors show that “P. likiangensis has exhibited a significant upward growth trend in recent years, while the growth of P. yunnanensis, A. forrestii, and T. dumosa has remained relatively stable”.

The question of tree ring response to climate change is traditional for tree-ring analyses, but still of interest, especially for such high elevated remote areas as the Southeastern Tibetan  Plateau. In my opinion, the study under review have potentials to contribute to the discussion of this problem, but I see several substantial problems in this paper.

The main problem that I see here is a mechanistic approach. The authors are focused at the “correlations”, while the processes including important ecological aspects of the tree growth-climate change relationships remain mostly outside their attention.

The important details are lacking in the manuscript, such as detailed ecological description of four species that are analyzed. I did not find the description of the ecosystems – are they closed wood or open stands, what is their structure, composition, what is the role of these four species in the forests, where the sites are located, how different these conditions are within and between the sites etc. etc.

The author’s anticipation number 1 (“ tree growth within the same region will exhibit similar climate responses”) is either wrong (because different species may react in a different way to the climate change) or has to be formulated more clearly. The two other crucial statements (lines 76-80) are rather trivial.

The description of the study area is insufficient. We need more data on physical geography, botany, descriptions of sites as well as of general climate setting and dynamic.

We need more information on seasonal temperature and precipitation trends. Moreover, it does not make sense to compare the ring width with the annual parameters –monthly and seasonal characteristics are more relevant. 

“Muli meteorological station, situated at approximately 27.7° N and 100.9° E”, - what is the elevation of the met.station? Are the measurements homogenous? Is it representative for the whole range of elevations of the sites that are almost 1000 m by elevation away from each other (2849-3643 m asl)?

Most of the text is the description of various correlations between the ring width and climatic parameters that sometimes do not clarify the relationships, but, on the contrary, confuses the reader. For instance, it is often not clear whether the coefficients of correlations under discussion are statistically significant or not or what is the potential ecological meaning of such or such correlation. For instance, the correlations of ring width with precipitation in the fall when the ring formation is almost finished need deeper ecological explanations as well as a justification of correlation with annual temperature that includes dormant season.

The title is not correct: among 4 species only one – according to the conclusions of the authors - exhibited a significant upward growth trend in recent years, others did not. Moreover, according to the figure 3 the growth trend of Abies is similar to one of Pinus, so I would not be convinced by this main conclusion.  Looking at the fig. 4 it is clear that unlike three other species Pinus has a very low climate sensitivity and is probably not suitable at all for this analysis.  At least its growth should be compared with monthly or seasonal rather than annual meteoparameters.

I have more minor comments but I see a general problem with this paper: the problem that is announced in the title is not solved and it cannot be solved the way proposed by the authors if they limit themselves by statistical analyses of short and sometimes not adequate records.

 

Comments on the Quality of English Language

Moderate editing of English language required

Author Response

Reply to Reviewer #1

The paper “Climatic Warming Had Caused Transition of Tree Growth Sensitivity From Temperature to Moisture Condition: Evidence From Muti-species Tree-ring Data of Southeastern Tibetan  Plateau” focuses at the statistical analyses of ring width of four conifer species growing at high elevation of Tibetan Plateau. Using standard tree ring technique and simple statistical correlations of tree rings and meteorological data the authors show that “P. likiangensis has exhibited a significant upward growth trend in recent years, while the growth of P. yunnanensis, A. forrestii, and T. dumosa has remained relatively stable”.

The question of tree ring response to climate change is traditional for tree-ring analyses, but still of interest, especially for such high elevated remote areas as the Southeastern Tibetan  Plateau. In my opinion, the study under review have potentials to contribute to the discussion of this problem, but I see several substantial problems in this paper.

Comment

• The main problem that I see here is a mechanistic approach. The authors are focused at the “correlations”, while the processes including important ecological aspects of the tree growth-climate change relationships remain mostly outside their attention.

Reply: Comment accepted. Many thanks to the referee for those constructive suggestions. We used traditional methods including correlation analysis and moving correlation analysis to study the response of tree growth to climate change. According to the referee’s suggestions, we have added the related package of the tree growth-climate change relationships in the discussion. Please see lines 346-463 in the text.

• The important details are lacking in the manuscript, such as detailed ecological description of four species that are analyzed. I did not find the description of the ecosystems – are they closed wood or open stands, what is their structure, composition, what is the role of these four species in the forests, where the sites are located, how different these conditions are within and between the sites etc. etc.

Reply: Comment accepted. Many thanks to the referee for those constructive suggestions. In accordance with the referee’s suggestions, the "2.2 Tree Ring Sampling and Measurements" section has been expanded to include a description of the ecosystem where the samples were obtained. Please see lines 115-125 for this additional information.

• The author’s anticipation number 1 (“ tree growth within the same region will exhibit similar climate responses”) is either wrong (because different species may react in a different way to the climate change) or has to be formulated more clearly. The two other crucial statements (lines 76-80) are rather trivial.

Reply: Comment accepted. Many thanks to the referee for those constructive suggestions. We had adjusted the description of hypothesis 1 “different tree species have different responses to climatic conditions, but due to their close geographical location, they may have similar responses to some climatic conditions” in lines 67-69.

• The description of the study area is insufficient. We need more data on physical geography, botany, descriptions of sites as well as of general climate setting and dynamic.

Reply: Comment accepted. Many thanks to the referee for those constructive suggestions. We have added the relative description of the geographical location, topography, soil types, and climate characteristics of the study area in the "2.1 Study Area" section. Please see lines 72-95 in the text.

• We need more information on seasonal temperature and precipitation trends. Moreover, it does not make sense to compare the ring width with the annual parameters –monthly and seasonal characteristics are more relevant.

Reply: Comment accepted. Many thanks to the referee for those constructive suggestions. We have illustrated seasonal-scale variations in temperature, precipitation, relative humidity, and PDSI (Fig S1-Fig S4). Furthermore, we have made modifications to the analyses involving annual-scale aspects in the figures (Fig 5, Fig 6, Fig 7).

• “Muli meteorological station, situated at approximately 27.7° N and 100.9° E”, - what is the elevation of the met.station? Are the measurements homogenous? Is it representative for the whole range of elevations of the sites that are almost 1000 m by elevation away from each other (2849-3643 m asl)?

Reply: Comment accepted. Many thanks to the referee for those constructive suggestions. We have added the description of meteorological station “The station is situated at coordinates 27.56N latitude and, 101.16E longitude, and an elevation of 2424 meters above sea level” in the text. This is the nearest meteorological station to the sampling sites. We concurrently downloaded CRU meteorological data and observed a significant correlation between the meteorological station and CRU data. The meteorological station can be considered representative of the regional meteorological conditions.

• Most of the text is the description of various correlations between the ring width and climatic parameters that sometimes do not clarify the relationships, but, on the contrary, confuses the reader. For instance, it is often not clear whether the coefficients of correlations under discussion are statistically significant or not or what is the potential ecological meaning of such or such correlation. For instance, the correlations of ring width with precipitation in the fall when the ring formation is almost finished need deeper ecological explanations as well as a justification of correlation with annual temperature that includes dormant season.

Reply: Comment accepted. Many thanks to the referee for those constructive suggestions. we have optimized the descriptions in the discussion section of the paper. On one hand, we have employed more precise language to articulate the statistical significance of the findings. On the other hand, modifications have been made to enhance the ecological significance of tree species' responses to various climate phenomena in the discussion. Changes include refining the description of the impact mechanism of autumn precipitation on tree growth, and providing additional explanations for the influence of dormant period temperatures on tree growth. Please see lines 344-438 in the text.

• The title is not correct: among 4 species only one – according to the conclusions of the authors - exhibited a significant upward growth trend in recent years, others did not. Moreover, according to the figure 3 the growth trend of Abies is similar to one of Pinus, so I would not be convinced by this main conclusion.  Looking at the Fig4 it is clear that unlike three other species Pinus has a very low climate sensitivity and is probably not suitable at all for this analysis.  At least its growth should be compared with monthly or seasonal rather than annual meteoparameters.

Reply: Comment accepted. Many thanks to the referee for those constructive suggestions. We have enhanced the analysis of tree growth trends and the trends in temperature and relative humidity changes through a standardization method (Fig 8). The results are depicted in Figure 8. Through standardized analysis, we observed that the rising temperature affects tree growth, albeit with varying durations of impact on different tree species. Furthermore, it was noted that tree growth has been significantly influenced by moisture conditions in recent years (Fig 8). Finally, we reanalyzed the growth trend of different tree species (Fig 3). The results exhibited the growth trend of first rising and then decreasing in recent years according to the Fig 3.

• I have more minor comments but I see a general problem with this paper: the problem that is announced in the title is not solved and it cannot be solved the way proposed by the authors if they limit themselves by statistical analyses of short and sometimes not adequate records.

Reply: Comment accepted. Many thanks to the referee for those constructive suggestions. In this revision, new statistical calculations have been performed at locations such as Fig 3 and Fig 8. In the expression of the paper, especially in the results section, descriptors like "significant correlation (p<0.05), (p<0.01)" have been added. Moreover, in the revised article, all upward and downward trends in the discussion have a significance level of p<0.05 or below. The new trend or correlation descriptions now hold statistical significance. Please refer to Fig 3, Fig 8, as well as the results and discussion sections of the article.

 

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

Dear Authors,

Please find my comments in the attached file

Regards

Comments for author File: Comments.pdf

Author Response

Reply to Reviewer #1

Comment

• Please clarify your research problem.

Reply: Comment accepted. Many thanks to the referee for those constructive suggestions. We have revised the first paragraph of the introduction by eliminating irrelevant portions and aligning the content more closely with the focus of the study. Please see lines 33-41 in the text.

• What about different size trees, growing and different competition conditions?

Reply: Comment accepted. Many thanks to the referee for those constructive suggestions. In this study, the four tree species are the dominant species of the original natural forests, and can be relatively less affected by competition caused by other tree species. Our study primarily focuses on the impact of climate on the growth of different tree species. In the future, we will plan to further investigate the effects of competition on tree growth in this region.

• The sample size per tree is rather small.

Reply: Comment accepted. Many thanks to the referee for those constructive suggestions. In the text, the EPS for each tree species exceeds 0.85, indicating a sufficiently representative sample size.

• You tell nothing about the competitive situation of the trees. Did you take samples from the dominant trees? or from the smaller, already under shelter trees?

Reply: Comment accepted. Many thanks to the referee for those constructive suggestions. In this study, the four tree species are the dominant species of the original natural forests. We have added detailed information about the ecological environment in which the trees are located, including whether they are dominant tree species, in lines 115-125 of the "2.2. Tree Ring Sampling and Measurements" section.

• What was the distance of meteorological station to the place where trees grown?

Reply: Comment accepted. Many thanks to the referee for those constructive suggestions. We have elaborated on the distance between the meteorological station and the sampling sites, which ranges from 38 to 46.5 km. Please see line 151 in the text for further details and Fig 1.

• “ R programming language.”Reference needed

Reply: Comment accepted. Many thanks to the referee for those constructive suggestions. in this regard, we have verified the accurate description of the "R programming language" and made modifications to two relevant expressions in the article. Please see lines 139 and 180.

• you could improve your chronological characteristics analysis by adding some parameters: Chronology statistics of Scots pine provenances, glk—gleichläufigkeit, MS—mean sensitivity,rbt—the average pairwise correlation between series, EPS—expressed population signal; R—mean nter-series correlation, AR1—first-order autocorrelation

Reply: Comment accepted. Many thanks to the referee for those constructive suggestions. In the summary statistics table of the article (Table 1), we have added supplements for the previously lacking parameters and provided detailed expressions. For a thorough understanding, please see lines 183-192 in the article as well as Table 1.

• Please discuss the shortcommings of your analysis, for example small sample size and its representativity

Reply: Comment accepted. Many thanks to the referee for those constructive suggestions. We have addressed the shortcomings of the study in the final paragraph of the discussion. Please see lines 558-562 in the text.

• At the end of introductions, you presented three anticipations. Please give the conclusions to them here at this chapter.

Reply: Comment accepted. Many thanks to the referee for those constructive suggestions. In accordance with your insightful suggestions, the conclusion section of the paper has been revised. We have incorporated responses to the three hypotheses of the study at the beginning of the discussion. Please see lines 464-482 of the article.

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

The topic of the research work and manuscript is really interesting and provides new information. However there are some issues to be addressed towards its quality improvement before publication. In the abstract, write the whole scientific names of the species. I would propose to use less complicated phrases, mainly simple words towards the increase of detectability and readability. In line 39, please add as a reference referring to drought stress and the resultant hindering of tree growth in arid and semi-arid regions, the relevant study of https://doi.org/10.3390/f13060879 . In line 84-88, you refer to records and significant information though without providing a reference. In figure 4, all the respective info should be readable from one side of the page. In 107 line, uder which conditions were the cores left to air-dry, for how much time? In 108, you refer "once dried", what do you mean by that? How many trees trunks have been harvested and examined per species? In conclusions, you could add a brief sentence in order to highlight the practical meaning of this work and their respecitve results.

Comments on the Quality of English Language

Pay attention to the use of "'s", since it can not be used for non living/animate objects. Make a check in the whole text concerninig the specific issue. I would propose to change the active to passive voice, in order to avoid refering to "we ded this, we did that" in the methodology description.

Author Response

Reply to Reviewer #3

Comment

The topic of the research work and manuscript is really interesting and provides new information. However, there are some issues to be addressed towards its quality improvement before publication.

• In the abstract, write the whole scientific names of the species. I would propose to use less complicated phrases, mainly simple words towards the increase of detectability and readability.

Reply: Comment accepted. Many thanks to the referee for those constructive suggestions. We have revised the Latin names of tree species in the abstract by replacing them with Latin abbreviations. Please see lines 91-92 in the text.

• In line 39, please add as a reference referring to drought stress and the resultant hindering of tree growth in arid and semi-arid regions, the relevant study of https://doi.org/10.3390/f13060879 .

Reply: Comment accepted. Many thanks to the referee for those constructive suggestions. The introduction has been modified, and the discussion regarding the impact of drought on trees is now presented in the third paragraph of the introduction. Relevant literature is cited in the content spanning lines 138-140.

• In line 84-88, you refer to records and significant information though without providing a reference.

Reply: Comment accepted. Many thanks to the referee for those constructive suggestions. The content originally found in lines 84-88, now present in lines 101-104, is derived from the statistical analysis of the Muli meteorological station data in this study. Recognizing the need for clarity, we have modified the description of this section for better articulation.

• In figure 4, all the respective info should be readable from one side of the page.

Reply: Comment accepted. Many thanks to the referee for those constructive suggestions. We have made adjustments to address the side display issues in Fig 4 and Fig 5, removing unnecessary information on one side of the images. Additionally, explanatory notes have been added in the text. If you have any further concerns or need additional modifications, please feel free to let us know.

• In 107 line, which conditions were the cores left to air-dry, for how much time?In 108, you refer "once dried", what do you mean by that? How many trees trunks have been harvested and examined per species?

Reply: Comment accepted. Many thanks to the referee for those constructive suggestions. The cores were air-dried naturally in the laboratory for one month and subsequently polished. A total of 260 tree cores from 151 trees were utilized for the climate response analysis. The description "once dried" has been modified in lines 129-131 and 137-138 of the article.

• In conclusions, you could add a brief sentence in order to highlight the practical meaning of this work and their respective results.

Reply: Comment accepted. Many thanks to the referee for those constructive suggestions. In the conclusion section, we have provided a more concise and focused description, aligning the content more closely with the key themes. Please see lines 465-483 in the text.

• Pay attention to the use of "'s", since it can not be used for non living/animate objects. Make a check in the whole text concerninig the specific issue.

Reply: Comment accepted. Many thanks to the referee for those constructive suggestions. We have carefully examined and addressed grammar issues, specifically focusing on the usage of "s" in the article. Additionally, we have polished the overall writing.

• I would propose to change the active to passive voice, in order to avoid refering to "we added this, we did that" in the methodology description.

Reply: Comment accepted. Many thanks to the referee for those constructive suggestions. We have reviewed the instances of "we did..." and made the necessary modifications and replacements in the article, such as lines 17, 63, 126, 128, 161, 176, and 181.

Author Response File: Author Response.pdf

Round 2

Reviewer 3 Report

Comments and Suggestions for Authors

As I have checked the authors have implemented the proposed changes in the revised verion of manuscript towards the improvement of their work. Almost all the changes have been implemented and in my opinion, the manuscript is well-prepared and organized enough to be accepted for publication in this journal. 

Comments on the Quality of English Language

The use of English language is acceptable, it has been highly improved after the revision.