Timescale Effects of Radial Growth Responses of Two Dominant Coniferous Trees on Climate Change in the Eastern Qilian Mountains
Round 1
Reviewer 1 Report
Review of:
Time-scale effects of radial growth responses of two dominant coniferous trees on climate change in the eastern Qilian Mountains Chang-Liang Qi1, 2 , Liang Jiao1,2* , Ru-Hong Xue1, 2 , Da-Shi Du1, 2 and Xuan Wu1, 2
Overall:
The study is designed to test differences in climate/radial growth relationships when using daily, pentad, dekad, and monthly data. Basically, which of these measures provides the most accurate information when we ask the question: what aspect of climate is causing trees to grow? They analyze two different species, one that grows in more open canopy, southern exposure and the other that grows in more closed-canopy environments. I like that aspect of the study. The main conclusions of the study are that, for these two species in this particular area, the decadal-level data provide the best information. While I think that is a useful conclusion and of value to the literature and readers of Forests, the study needs some fine-tuning. The authors make some conclusions that are not really supported by their statistical analyses. For example, at one point they argue that a 0.01 difference in an r-value shows that dekad-level data are superior to monthly. What I see are findings that show, when you use finer-level climate data, you can tease out finer temporal scaling. For example, within a given month that recorded above-normal precipitation, it is likely that one or two events would have driven the findings of a wet month, and the dekad-level (or pentad or daily) will show these time periods better. However, what the authors show in their findings is not really surprising – pentads track days, dekads track days, and months track days when we aggregate. I think, perhaps, the importance of this type of work is not simply showing that finer temporal scaling can be important when discussing climate/growth relationships. I think that is an obvious conclusion borne out by their analyses. What I would like to see is a deeper dive into the data. What exactly are the strong correlation dekads capturing in this region? Are they capturing short-duration meteorological events like a heatwave, a strong mid-latitude wave cyclone, big snowfall events, etc.. The authors should also consider using a measurement that captures the combined impact of temperature and precipitation on growth (i.e., something related to evapotranspiration).
The graphics are nicely done. The writing needs improvement. Many of the sentences are awkward and sometimes they are grammatically incorrect. The writing needs to be more succinct – it gets repetitive in places.
Specific comments follow. Since there were no line numbers on the PDF, I grouped the specific comments by page number.
Specifics:
Page 1:
on the spatial and temporal scales -- drop “the”
On the one hand, in humid regions, warmer temperatures can promote radial growth by accelerating the onset of lignogenesis or increasing photosynthetic rates (Lindner et al. 2010, Rossi et al. 2014). On the other hand,
Suggest: In humid regions, …. . Alternatively, …
Page 2:
As a result of global warming, tree growth decrease and death have become more common, particularly in semiarid and arid regions
This is not always the case in semiarid regions. There is considerable literature dealing with the effects of atmospheric CO2 enrichment, which has resulted in increased radial growth of various semiarid tree species. This needs to at least be recognized by the authors in this introduction.
For example, from: 2013. P. T. Soulé and P. A. Knapp. “Radial Growth Rates of Two Co-occurring Coniferous Trees in the Northern Rockies during the Past Century. Journal of Arid Environments. V. 94: 87-95.
They state: “Both conifers experience increased radial growth post-1950. We conclude that increases in standardized radial growth rates are unlikely climatically-driven. Other potential vectors of radial growth change, such as atmospheric CO2 enrichment, have affected these co-occurring species on a largely equal basis and positively.”
Other potential references related to CO2 enrichment are mentioned in this article in the sentence:
Elevated atmospheric CO2 can have a positive effect on radial growth rates of naturally-occurring trees in semiarid environments (Graybill, 1987; Graybill and Idso, 1993; Hättenschwiler et al., 1997; Knapp and Soulé, 2011; Knapp et al., 2001a, 2001b; LaMarche et al., 1984; Martínez-Vilalta et al., 2008; Soulé and Knapp, 2006), thus providing a possible nonclimatic explanation for the increased growth.
greatsignificance in fully understanding on the spatial and temporal responses
change to: great significance in fully understanding the spatial and temporal responses
and certain climatic indications ---- do you mean “indicators”?
Tree-rings(Zhang et al. 2012), on the other hand, --- I think you should not use this language “on the other hand”. If needed, it can be replaced with “alternatively” (thus more succinct writing).
Also, I’m not sure if this is a formatting issue, but here and in other places we are missing spaces between works (Tree-rings(Zhang …)
Page 3:
The study area is in Tulu Trench Forest Park (36° 40′–36° 44′ N, 102° 36′–102° 45′ E) in the eastern Qilian Mountains (Fig 2). It has a typical temperate continental monsoon climate, with a hot and rainy summer and long cold winter (Fig. 1). – In this sentence you have Fig. 1 and Fig 2 confused (need to start with F1 and then mention F2)
runoff, dry and wet, -- dry and wet what? I assume dry and wet periods
Additionally, most of these studies were carried out in the western and central Qilian Mountains (Gou et al. 2005, Liu et al. 2007), and were few were performed in the eastern Qilian Mountains (Liang et al. 2009, Yang et al. 2013, Deng et al. 2013). Furthermore, the response patterns and mechanisms of radial growth under climate change are still not clear for different timescales and species. Therefore
My preference is to use words like “additionally, furthermore, therefore” sparingly. Here we have three sentences in a row starting with these words.
the following were necessary -- this is awkward phrasing. I’d prefer active voice. For example:
To determine the timescale effects of patterns in radial growth responses in two dominant coniferous trees under climate change in the eastern Qilian Mountains, we: 1) Analyzed …, and 2) compared
Page 4
For all of your multipanel figures, you need to label the panels as A, B, C, D and then include detailed descriptions of what is shown in each panel in the figure legend.
Page 5
, a growth cone -- I’ve never heard the instrument called a “growth cone” before. It is typically called an increment borer
contained the strong climate signals - I think you mean the “strongest” climate signals
Page 8
considerably negatively correlative -- this is awkward phrasing – what exactly are you trying to say here? Perhaps weakly negatively related?
In general, I view correlation as the tool used to identify the presence or absence of relationships, so my preference is to write accordingly (e.g., I used Pearson correlation to determine the strength of the relationship between X and Y. Variable X had a significant (p <0.05) negative relationship with Y. etc.
Figure 4. Response of radial growth of trees to monthly values of climatic factors. --- In this figure legend you need to mention what the blue shading on the figure represents. I assume it shows the boundary between statistically significant and non-significant relationships, but this needs to be explicitly stated. Same comment for Figures 5, 6, and 7
Page 11.
There is an in depth relationship between regional climate and also the radial growth of trees.
Need a hyphen (in-depth) and delete also. But, what does “in-depth” mean here? This is a statement that really doesn’t need to be stated. This is pretty common knowledge that tree growth is related to climate, so I’m not sure of the reason for stating it in this paragraph.
This study found that temperature is one in all the key factors limiting the radial growth of trees within the study area, which they increased significantly with 0.428℃/10a (Fig. 3).
This sentence is just a mess. It is grammatically incorrect (run-on sentence). How about:
Temperature is one of the key factors limiting the radial growth of trees within the study area.
which they increased significantly with 0.428℃/10a (Fig. 3). – I have no idea what the second part of this sentence is trying to say.
Page 12:
We found a significant positive correlation between
Here and elsewhere, again my preference is to state “We found a significant positive relationship between ….” To me, correlation is a statistical tool used to determine the strength and significance of a relationship, just like ANOVA would be used to determine significant differences among multiple groups, or s-mode PCA might be used to determine geographic groupings. All tools used for a purpose.
There was no correlation between radial growth and total precipitation at the monthly scale, but there was a negative correlation with precipitation on the daily, pentad and dekad scales (Fig 4-7)
This is awkward. Of course you have correlations, Fig 3 shows correlations for each month. I think what you are trying to say is that you don’t have many significant relationships between radial growth and precipitation when the data are aggregated to a monthly scale. I think since this is the crux of this study, you need to be exceedingly careful with your wording here. Also, I think Fig 3 does show significant relationships for Pinus tabuliformis in months C2 and C10, so this statement is not even correct.
Meanwhile, the correlation coefficients were higher between the radial growth of the two trees and the precipitation and temperature (mean minimum, mean maximum and mean temperature) at the daily, pentad, dekad and monthly scales.
What is this sentence trying to say? Perhaps that relationships were stronger using daily data compared to pentads, pentads to dekads, dekads to monthly aggregates? It is not clear to me.
coefficients between the tree ring data and climate factors exhibited certain similar characteristics at the four timescales (Fig.4-7). This is mainly due to the fact that the main controlling climatic factors affecting tree growth at the four timescales had similar onset/end dates.
Is this really an unexpected finding? Pentads, Dekads, and Monthly are just aggregates of daily data, so it makes sense there are similar findings.
The above points indicate that the responses we have a tendency to measure of tree rings to climate at the four timescales are credible
This is an awkward sentence.
Furthermore, these findings suggest that tree radial growth provides additional climate information on daily and dekad timescales
Here the first sentence of a new paragraph starts with “Furthermore”. A new paragraph suggests a new thought or topic, so you can’t start a new paragraph with a connector phrase like “Furthermore”. I think this is still part of the prior paragraph.
Each week, microcores are collected from five uniform P. tabuliformis trees. (Wilson et al. 2002), Cell division in the dendritic zones of trees in North China began in the third week of May, according to research.
???? on this sentence. It sounds like Methods to me (microcores are collected), then turns into a run-on sentence with the comma after the Wilson reference. Why is Cell capitalized? Was the comma supposed to be a period? According to research? – We need a specific reference to research. Please re-think and rewrite this sentence for clarity.
In addition, the most correlation coefficients --- delete “the”
From this sentence, again, this result is not surprising.
have also been wide utilized -- you mean “have been widely used”
In an effort to better comprehend the dekad scale's superiority, we discovered that the greatest correlation coefficient between radial growth of trees and temperature in the 17-25th dekad period (0.766) was larger than the monthly value for the same time (0.758).
I think this sentence really contradicts what you are trying to say. You are arguing that Dekad-level data are superior to monthly data for showing the strength and significance of climate-growth relationships. Yet, we get an r-value of 0.76 for monthly, and 0.77 for deakad-level data! Are you really trying to argue that an increase of 0.01 in your correlation coefficient is statistically meaningful? I hope not! There are statistical tests that allow for the comparison of r-values (i.e., is r-value X significantly different than r-value Y). 0.1 is a trivial increase and, perhaps, you should think about re-tooling your conclusions to state that when we aggregate the climate data, we get the same basic findings. The utility of the daily, pentad, and dekad analyses, to me, is that is shows the potential importance of short-duration meteorological events for radial tree growth. For example, in my work, I’ve looked at the relationship between radial tree growth and precipitation delivered from landfalling tropical cyclones. When you extract that specific element from the climate record (i.e., precipitation from tropical cyclones) and correlate it with tree growth, you get a much stronger relationship than when you use the aggregated monthly climatic data (which includes all forms of precipitation). It might be useful to delve into your data and see what was happening, meteorologically, when the strongest decadal relationships were found. Thus, was it a heatwave or heavy precipitation event, or something else?
Page 14
Radial tree growth varies greatly between environments or species (Fonti and Jansen, 2012). This may be due to the highest temperature occurring between June and August. High temperatures lead to the closure of tree stomata, reductions in CO2 absorption, and the weakening of photosynthesis. In addition, a high temperature leads to the intense evaporation of soil water, and environmental drought inhibits the physiological activities of tree cambium cells, which is not conducive to the radial growth of trees (Tian et al. 2017, Wang et al. 2018).
The highest temps in the southern hemisphere are not between June and August. Then, many species respond positively to increasing temperature, so I don’t know where this paragraph is heading – the statements are just too general and don’t reflect the geographic and environmental variability of climate/radial growth relationships around the world.
The available water could hardly meet the needs of plants due to the high temperatures and drought that occurred in the growing season in the northwest inland area of China, leading to severe drought stress in the radial growth of P. tabuliformis in the study area. T
I don’t see how you can reach this specific conclusion from your limited analyses. You correlated temperature and precipitation to growth. You didn’t even use a simple metric like the Palmer Drought Severity Index, that might actually show this (i.e., the PDSI attempts to factor in evapotranspiration rates, albeit in a rather cursory way).
will cause declines in tree growth, tree mortality, and community degradation (Jiao et al. 2019).
As written, this sentence is illogical. It suggests a decline in tree mortality and degradation. It needs to be rewritten for clarity.
Author Response
Thank you very much for your careful reading. We have tried our best to revise the manuscript according to your comments. We have added data analysis and explanation in Introduction, Results and Discussion. In addition, the monthly standardized precipitation - transpiration index (SPEI) is a better drought index, which does not ignore the influence of temperature, wind and other climatic factors. Therefore, we also calculated the Pearson correlation coefficient between annual ring width chronology and monthly SPEI of the two species, further confirming that drought is the main limiting factor for radial growth of the two species. We also added details to the charts to make them more representative of the results. We added references and research results, improved the language description, revised the manuscript, and improved the quality of the paper.
Author Response File: 
Author Response.docx
Reviewer 2 Report
It is an interesting paper.
The result section can be improved by making it concise; and only significant results can be presented in figures.
Some improvements by editing such as connecting words, references, brackets letter font etc. can be improved.
Author Response
Thank you very much for your careful reading. We have tried our best to revise the manuscript according to your comments. We have added data analysis and explanation in Introduction, Results and Discussion. In addition, the monthly standardized precipitation - transpiration index (SPEI) is a better drought index, which does not ignore the influence of temperature, wind and other climatic factors. Therefore, we also calculated the Pearson correlation coefficient between annual ring width chronology and monthly SPEI of the two species, further confirming that drought is the main limiting factor for radial growth of the two species. We also added details to the charts to make them more representative of the results. We added references and research results, improved the language description, revised the manuscript, and improved the quality of the paper.
Author Response File: Author Response.docx
Round 2
Reviewer 1 Report
I provided detailed suggestions for revising the manuscript in my initial review. The authors have replied to all of my suggestions and made numerous changes to the manuscript based on my suggestions. I like the addition of a drought index -- that strengthens the results.
While I appreciate the detailed replies to my suggestions for revisions, I don't understand why some of the tables and figures the authors included in the author's response were not incorporated into the revised manuscript. I absolutely think they should incorporate the "Table 1" in the revisions file into the revised manuscript. It succinctly shows one of their main conclusions, that the dekadal aggregation of data has the strongest relationship with radial growth.
I don't fully understand what the authors were trying to demonstrate in the responses file with the multiple graphics showing moving interval correlation and/or if this adds or detracts from their study. However, these findings appear to show changing climate responses through time, which is a point worthy of discussion.
While improved, there are still numerous technical problems with the writing.
A couple of examples:
"We analyzed the correlation between the radial growth of trees and SPEI. The study
found that the radial...."
The first sentence is written in active voice, the second in passive voice. My preference is to choose one or the other and use it consistently.
"Since tree growth has similar start/end dates."
This is an incomplete sentence
Author Response
Based on detailed suggestions from the editor and the first reviewer, we did our best to revise the manuscript. We have added data analysis and interpretation in the Results and Discussion sections, and added figures and tables to better represent the research Results. At the same time, we improved the language description, revised the manuscript and improved the quality of the article.
Author Response File: Author Response.docx
