Retention Forestry Supports Bird Diversity in Managed, Temperate Hardwood Floodplain Forests

Round  1

Reviewer 1 Report

In the manuscript “Retention forestry supports bird diversity in managed, temperate hardwood floodplain forests” the authors address the importance of retained legacy oak trees for forest bird communities 18-22 years after clear-cutting. The study questions are relevant for practices of bird conservation and are likely to also have implications for other taxa associated with old trees in managed forest landscapes. Specifically, the paper highlights the dependence of cavity-nesting bird species on the presence of legacy trees. The structure of the manuscript is reasonably well organized and the language is mostly correct with some exceptions.

However, there are some major issues which need to be addressed in this manuscript. The most important issue is that analyses are not well motivated or explained, and are in my opinion not adequate considering the sample size and structure of the data. Data was collected over a period of four years, however, different study plots were surveyed in different years which makes direct comparisons between these inappropriate. I believe that the main findings of the study are still reliable, but the analyses need to be improved. Below I provide my recommendations for revision.

Abstract:

General comment: Even though the language is easy to understand, there are misspellings and other minor syntax issues throughout the text. I have only commented in detail on the abstract, but the authors need to work through the rest of the text, or employ an English editing service. Also, use of words like “obviously” is not appropriate in scientific writing.

Line 19: Replace “tool of” with “tools for”

Line 20: Insert “of” in “conservation of biodiversity”

Line 21: Insert “s” in “forest structures”

Line 22: Choose only one of “provides” or “maintains”

Line 24-25: This sentence implies that your study is long-term and provides a landscape perspective, which is does not, so I suggest you rephrase it. The study (even though done over a couple of years) does not evaluate the effect of time, but it evaluates long-term consequences (18-22 years after clear-cutting).

Line 28: Remove “clearly”, it is not good scientific language. Just say what the results showed.

Line 29-30: Remove this sentence, it only repeats what you have just said in the sentence before.

Line 30: “These results…” What do you mean by “portable”? “Applicable” maybe?

Line 32: Insert “s” in “keystone structures”

Lines 32-35: Shorten and rephrase. This sentence again repeats the same conclusion which has already been mentioned before. Suggestion: Legacy oak trees in this habitat type are keystone structures for bird diversity. Retention approach focused on these trees is potentially an important conservation tool for preserving forest bird diversity and other associated species in temperate hardwood forests managed by clear-cutting.

Introduction:

General: Introduction gives a good overview of the topic, but it can be shortened and made more focused on the specific research questions, now it is like a literature review citing every single study in the field.

Line 44-47: Rephrase without “obvious”. Something like “The main difference between clear-cutting and natural disturbances in forests is that the biological legacies left by…”

Line 48: Remove “On the other hand”

Line 55 and 58: Use “retention forestry”, not “retain forestry”

Lines 58-61: Merge this paragraph with the one above.

Line 62 (and in other places throughout the manuscript): Remove phrases like “as stated in review”, “mentioned in study”, and similar. Just say what the studies have shown, with the reference at the end of the sentence.

Line 62-76: Shorten this paragraph to make it more clear and focused. Basically, what you need to say is that time since clear-cutting can have a major impact on bird communities, because the retained trees will provide suitable structures throughout young successional stages. No need to talk much about landscape-scale research, because your study does not address that.

Line 85: Insert “and” after “clear-cutting”

Methods:

General: The survey method is detailed and thorough, but the timing of surveys is unfortunate, because the data from surveys done on different years cannot be directly compared.

 Line 112: Replace “seriously” with “considerably”

Line 103-121: Shorten to a concise summary of relevant facts for your specific study – age of the oak trees and management type applied is relevant, reasons for retaining trees in the past is less relevant. Specifically, text in lines 113-121 can be summarized in 1-2 sentences.

Line 119: In order to use “On the other hand” you first need to use “on the one hand”

Data analysis:

Line 151: How was the bird density calculated precisely? For each species? Per survey year? All years combined? These details need to be specified.

Line 151-151: This is not enough information, you need to describe what these dominance values tell and why they were calculated. “In order to …..we calculated dominance values based on (method)…”. These values were not analysed in any way as far as I see? So even more important to tell what the point was.

Line 152-153: Again, how was the data used to calculate these in respect to survey year and surveyed plots?

Line 154-162: This section is really not adequate or well described. First – what was your sample size, i.e. what data constituted a single sample? One plot in one survey year? In this case the samples are not independent and “year” needs to be accounted for in the analysis. Or each plot summed for the three years? In this case your sample size is too low to do any meaningful statistical analysis. Why did you use proportion of species and not the number of species (or territories) observed? Using a t-test is not appropriate in either case, but can be more justified for number of species actually (because Poisson distribution approaches a normal distribution at mean values above 5-10).

I will outline a suggestion for analyses which may address the study questions more adequately. The analyses should be based on data from one plot in one year as single sample, that way you will have 18 samples to work with. The analyses need to include survey year and presence/absence of ILOT as fixed explanatory factors. As response variables you can use number of species or/and number of territories, and even the density or dominance values. Assuming normal distribution may be fine for all of these, but needs to be checked accordingly. Also, you could repeat the analysis for each of the bird nesting guilds separately, then you would clearly see if the difference is significant for cavity- and hole-nesters, but not for others.

Results:

General: Currently, most of the results are just descriptive data. It is fine to show the general patterns this way, but you cannot say that some values were higher than others or differences were found between plots without actually analyzing the data.

Line 167: replace “obvious” with “evident” perhaps and “best” with “largest”

Line 170: Where are the calculated values for Jaccard index presented?

Lines 190-202: Still not clear to me what the sample size is in these analyses, see other comments above. And what are the values presented in the table 2? There are no comparisons within ILOT /no ILOT plots, there might as well be differences between these, what will your results tell then? So you have not showed that plots with ILOT are different from plots without ILOT as a group, which is absolutely necessary in order to generalize the importance of ILOT, as you do in this paper.

Discussion:

General: There are some good points made in the discussion, however, it should be more clear which conclusions are based on the results of analyses and which are just interpretations/speculations of the authors. Similar to introduction, there is a lot of literature-reviewing, which can be shortened.

In order for the discussion to be more focused, I suggest the authors identify a list of their main findings ad then discuss each of these in relation to existing literature and conservation implications. Now there is some discussion on species diversity and guild structure (can be further developed), but no mention of the community composition, density or dominance. What was the point in calculating these then? Implications for bird population density and whether the legacy trees contribute enough to maintain viable population sizes of different species could be something to discuss, for example.

Line 206-207: The hypothesis cannot be validates by the method you have used – see previous comments on the methods/results.

Line 216-222: Shorten to 1-2 sentences, only mention the most relevant studies.

Lines 223-227: I don´t see how this relates to your findings, remove. You have already explained the definition of legacy trees in this study in the introduction/methods section where it is appropriate.

Line 228: Replace “taken” with “obtained”.

Lines 228-234: Again, this is background information, nothing to do with interpretation of your study results, remove.

Line 242: Remove “fortunately”

Lines 241-244: Relevance to study results not clear, remove. The rest of the paragraph is relevant (lines145-253), but the logic is not completely developed at the end.

Lines 254-256: This is your main finding and should be the starting point of discussion, not a short mention in the middle.

References:

A standard research paper typically has about 35-50 references, this paper has 93! Excessive and unnecessary use of references only wastes journal space, you need to include citations of relevant literature where necessary, not all literature in the field.

Author Response

Dear Reviewer,

we are very grateful for your time and valuable comments to our manuscript. We corrected the former manuscript following your recommendations. We believe that we accepted all of your recommendations and advices. In detail, see please to attached Cover letter with list of our responses to your comments.

Best regards, Ivo Machar (corresponding author)

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments on ms forests-453408

There are problems in the statistical analyses presented. You have two treatments (1 with ILOT and 1 without ILOT) in the comparison. Both have 3 area repeats. Because of low N you have used one-tailed t-tests instead of two-tailed tests. This is problematic first because you use proportions in the comparisons, the assumptions of the t-test are not fulfilled. I think that instead of the t-test you should use the non-parametric Mann-Whitney U-test in comparisons. 

Second I would like to see that you average the results (density and species number) with SD or SE values per the treatment (N = 3 and 3) in species level and then count the grand means for density and species number. These results should be presented in the Table.   

After that it could be possible to make the t-test for the density using the grand means calculated from different species densities.

The Table 2 is unclear. Are the values t-test values?  If you make 9 comparisons you should use the Bonferroni correction.

Page 8 lines 270-272. is this (81) correct reference?

Author Response

Dear Reviewer,

we are very grateful for your time and valuable comments to our manuscript. We corrected the former manuscript following your recommendations. We believe that we accepted all of your recommendations and advices. In detail, see please to attached Cover letter with list of our responses to your comments.

Best regards, Ivo Machar (corresponding author)

Author Response File: Author Response.pdf

Round  2

Reviewer 1 Report

I have read the revised version of the manuscript "Retention forestry  supports bird diversity in managed, temperate hardwood floodplain forests" and I think the authors have made significant improvements. The main issue - statistical anlysis - has been addressed to the authors best ability, I believe, and is definitely more appropriate for the data now. The manuscript also reads better now when excessive text and references have been removed.

I have no additional coments.

Author Response

Dear Reviewer,

many thanks again for your valuable comments to the manuscript. Please, see to our response to both of Reviewers in attached file.

Best regards, Ivo Machar (corresponding author)

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments on reviewed Ms forests-453408

The MS has now considerable improved. I have only minor comments.

It seems that the bird communities in the sites without ILOT basically consist of open and semi-open habitat species. The authors should also shortly discuss about that topic. What habitat characteristics determine the species community in the sites without ILOT?

Please, use the term Mann-Whitney -U test consistently through the paper.  The term Wilcoxon test is confusing.

Author Response

Dear Reviewer,

many thanks again for your valuable comments to the manuscript. Please, see to our response to both of Reviewers in attached file.

Best regards, Ivo Machar (corresponding author)

Author Response File: Author Response.pdf