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Peer-Review Record

Unveiling the Diversity of Tree Growth Patterns in Boreal Old-Growth Forests Reveals the Richness of Their Dynamics

Forests 2020, 11(3), 252; https://doi.org/10.3390/f11030252
Reviewer 1: Anonymous
Reviewer 2: Anonymous
Forests 2020, 11(3), 252; https://doi.org/10.3390/f11030252
Received: 22 January 2020 / Revised: 20 February 2020 / Accepted: 21 February 2020 / Published: 25 February 2020
(This article belongs to the Section Forest Ecology and Management)

Round 1

Reviewer 1 Report

The strengths of the paper are that the Methods and Results are clearly presented and easy to understand, and the Discussion is well organized around the study goals. The weaknesses are that the motivation for the study and the importance of the results are poorly explained. Most crucially, it is not clear what the novel contribution of the work is. Most of the results seem confirmatory of what is already known about forest succession and stand dynamics.

In the Introduction the authors need to fully describe the need for this study, especially since selective logging has already been promoted (and has support) as a method for maintaining old-growth forest diversity. Why specifically do we need to understand the radial growth patterns as opposed to say, old-growth forest structure?  

The Discussion’s implications for management are also not clear. Managers are already using selective cuts etc. to mimic old-growth structure. How does knowledge about the different growth patterns inform managers? See line comments below. Similarly, in the Conclusions the authors state “The radial growth patterns identified in this study could serve to develop forest dynamics models that provide a better description of fine-structural changes in boreal old-growth forests”.  It’s not clear why this is important.  Do managers need these models?  The authors assert that managers need to know their targets, but the link between specific radial growth patterns, management activities, and target outcomes is not clearly made, further muddying the importance of the study.

345—346 In reference to the successional model presented, the authors cite Oliver and Larson 1996 and seem familiar with forest succession literature. However they use a different terminology to describe the successional stages in their conceptual model. Unless there is a reason for this alternative, I suggest using the Oliver and Larson model or another common model for comparison throughout the paper because these models are very common in forestry. If the authors’ model stages are very different than existing models form the literature, then I suggest including a description of how they are different. For instance:

Cluster 1 “post-stand-replacing disturbance cohort”, how is this different from the O&L “stand initiation chort”.

Cluster 2  “old-growth transition” seems equivalent to O&L “stem exclusion”. How is this different?

Cluster 3 “True old-growth” seems equivalent to O&L “understory reinitiation”, following small to moderate disturbances, like gap-phase dynamics.  How is this different?

Cluster 4 “True old growth” equivalent to O&L “old-growth”. 

296 – 308 The authors suggest that growth patterns are often more complex than what they found. But the process used mean ring widths of each segment, essentially a smoothing of inter-annual variability. Their Methods acknowledge this smoothing but they don’t consider it as a factor in the Discussion. What about the other papers cited [43, 64, 65], are those patterns more complex because there was no smoothing?

337- 339 For Cluster 3 what is an example of a low severity disturbance in this system? A gap caused by a tree falling?

351-352 – a “consistent and original perspective”. The patterns are consistent with what we already know about forest succession. So what is the broader impact of this perspective? Succession dynamics are “highlighted” but it is not clear how examination of radial growth patterns has improved our understanding of old-growth dynamics.

364 “Alternative” to what? Doing nothing?

365-372 Why is this detail important?  This section points out that silvicultural treatments can help mimic old growth structure (which we already know), but it isn’t clear why managers might be seeking more “Cluster 3” or “Cluster 4” results. Please explain.

386-388 The growth patterns were relatively simple, and the conceptual model has only two types of “old-growth” (Clusters 3 & 4), so how can you say this supports a “wide-variety” of structures and disturbance histories”?

Author Response

Please see the attachment

Author Response File: Author Response.docx

Reviewer 2 Report

General comments

The manuscript entitled “Unveiling the diversity of tree growth patterns in boreal old-growth forests reveals the richness of their dynamics” focuses on identifying the main radial growth trends in old-growth forests and how they could help the developing silvicultural treatments that mimic the complex dynamics of old-growth forests. The study shows that the six identified growth patterns can be clustered into simple patterns which correspond to different successional stages of old-growth forests. I believe that the obtained results can be compared to similar studies of temperate and boreal forests in Europe for more effective silvicultural treatments. I find the manuscript interesting. Overall, the structure of the article is clear and the results are well explained. Regardless, I do not have any major critiques and I believe my suggestions could improve the paper.

 

Text comments

Line 64-66: I fully agree with this statement, but this is also true for Europe’s boreal forests, especially regarding the old-growth temperate forests. Adding a few references would give more scientific credibility to this claim.

Line 68: “...20th ...” – superscript

Line 112-127: It would be useful to have a figure showing how these 21 sample plots are located. It is also unclear what are the individual characteristics of the 21 sites – slopes; age; tree species diversity, etc. It is clear from simple math that 30 cores were not taken from each site as indicated. It is not possible to understand from what tree diameter the samples were taken, the note concerning coring of trees over 9 cm in diameter is very common. It is necessary to give at least a diameter structure of ach site, because stating in the introduction part that trees are harvested at over 70 years does not give a clear idea of the target diameters and hence the structure of the forest.

Line 130: What means are used to measure TRW?

Line 135: How did the tree ring series become 776 after line 126 stated that the samples were 756?

Line 137-138: Superscript for the markings of the percentiles.

Line 144-145: Segment separation is done based on the number of tree rings, not on the length of the cores (diameter of the disks), with the difference between the individual segments being maximum of one tree ring, right? In the line 147 the mean number of tree rings by segment was to 6.8 ± 2.5 rings, which means that the difference is not one ring. Thereof originate questions such as were light rings, missing rings, double rings, and narrow rings from old natural disturbances taken into account when measuring TRW and were they included in the conclusions drawn?

Line 148: Where I can see the Appendix S1?

Line 151: It would be in favor to indicate how this preliminary analysis was done

Line 155-164: Where could the characteristics of individual sites be found. It would be appropriate to list them in tabular form.

Line 165: I find the used statistical analysis to be especially felicitous.

Line 166-168: Incorporation of all tree rings series would camouflage the tree ring reaction and radial growth patterns of various tree species in different succession stages.

Line 201: Explain what means “n” in the brackets of the image in figure 1. Here a question arises: the sum of all trees is 737, in the text you mention once a number of 756 and another number of 776. Be sure to clear which is correct.

Line 207-210: These results confirm studies in Europe that representatives of Abies and Picea Genera are sensitive to changing conditions.

Line 212: “...5th ...” – superscript

Line 213-217: I find this statement very suitable.

Line 266: What does “n” in the title of table 3 mean, the same applies to figure 3.

Line 388-391: This ascertainment is exactly in place.

 

I sincerely hope that my comments and suggestions were useful and will assist the authors in the future improvement of the manuscript. Good luck!

Author Response

Please see the attachment

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

The authors have made substantial improvements to the manuscript that better relay the novel aspect and importance of their study. In particular the link between the identified cluster types and management has been made much stronger in the discussion. The edits have suitably addressed my major concerns and I commend the authors for their efforts.

Minor edits

Line 99 I suggest you highlight the methodological approach here, so the reader knows that you are using a newer technique. Something like, “Modern statistical approaches (e.g. machine learning algorithms like k-clustering) may greatly reduce subjectivity in the classification of ring patterns and therefore provide a better understanding of radial growth patterns in unmanaged boreal old-growth forests. An improved understanding of these patterns can help evaluate the similarity between the impacts from silvicultural treatments and natural disturbances

Line 103: recommend “static structural indicators” is fully explained. i.e. One-time measures of stand size or age structure.

Lines 395-405 – This should be its own paragraph because it is a major point explaining the novel aspect of the research. I suggest you are explicit in describing the advantage of the automated method with the older more subjective methods and indicators (e.g., Frelich, 2002; Lorimer & Frelich, 1989; Niukkanen & Kuuluvainen, 2011). I.e. it is less subjective, faster and other indicators are not needed.

Line 402 – As you said in your response to the reviewers, the method could be applied to a larger dendrochronological dataset. Why not mention that here?

 

 

Author Response

Please see the attachment

Author Response File: Author Response.docx

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