Terrestrial Bryophyte and Lichen Responses to Canopy Opening in Pine-Moss-Lichen Forests

Round 1

Reviewer 1 Report

Reviewer comments for manuscript  forests-440855

Brief summary 

This paper aimed at assessing the long term impact of different levels of timber harvesting on the understory communities of bryophytes, lichens and vascular plants. They show that the studied treatments did not change the understory communities of all species groups compared to controlled plots but there was a limited positive effect on reindeer lichens. The data is very interesting as long terms studies are rare in ecology.

 

Broad comments 

I think the data presented in this study is worth publishing and is of interest for the scope of this journal. However I would have liked to have seen more of the previous data collected throughout the study directly after treatment and in 2005 to assess the rapidity and directionality of change over time. Why were these data not included in this paper?. From my understanding the post treatment data was published (4) but the 2005 (37) data was only in a thesis? I think having the whole story would greatly add to this paper. I had lots of issues with the results section. I often had trouble understanding the statements and finding support for the statements in the figures or tables (see specific comments bellow). Not having access to the supplementary material also hindered my ability to judge the results appropriately.

I struggled with first few paragraph of the discussion which almost seemed to only summarise results but it quickly got much better and ended with a nice section that seemed more supported by the actual findings in this paper. I think this study could be published after some improvement especially in the result section and early parts of the discussion

 

Specific comments 

 

Line 79: There seems to be missing a word at the end of this sentence. Important in determining? species composition

Line 115-116: This hypothesis would be hard to test with only 2 sampling periods, no? Would need to have a few different sampling time after treatments to see a decrease followed by an increase. I realized while reading the methods that you did in fact have multiple sampling time post disturbance. Maybe make this more obvious in the introduction ex: 1) In line 103-105 explicitly says that that Mooneyhan-McClelland also sample vegetation data 2) on Line 109: In the present study we used previously collected data (1997-1998 and 2005) as well as data collected in 2016 …

Line 118- repetition of the: 4) the the

Line 156-158: Why was debris resulting from harvesting removed from the plots? Was this done as part of the treatment on the entire site or just in the plots? Doesn’t this debris occur normally following these treatments in most of the stand? Why exclude them only from the plots measured? Is the information found in these plots comparable to the rest of the stands if woody debris was only removed in the plots?

Line 158: Maybe explain why disturbances from logging equipement were restricted outside plots. Was it because the goal of this study was to assess the impact of canopy opening on vegetation and not mechanical soil disturbance or compaction. But in reality in addition to the findings in these study, these thinning treatments would also have an additional effect on understory communities by adding soil disturbances into the mix. Maybe comment on this in the discussion

Line 173-174: These seem pretty crude why not use the braun-blanquet method or event estimate percent cover to 10 or at least 25% intervals. There is a big difference between 50 and 100%. When assessing change over time this would have been more useful no?

Line 175-185 and 189-193: The font seems larger?

 

Line 206 : What exactly is included in ground layer attributes? Are feather mosses and lichens part of this group of attributes. Is this equivalent to surface features? Explain better what is included in ground layer vs  above ground vegetation

Line 217 The absence of difference in young pine individuals (what size exactly did you consider young pine?) was for which sampling year 2005, 2018 or both?

Line 218-219: not sure you can have an absence of difference or a decrease in canopy cover yet have a significant result?

Line 222: Would have been nice to have the supplementary material to complete this review? Why was this included with the submitted manuscript?

Line 223: Not convinced about this statement the difference in species richness are pretty slim and the intervals overlap quite a bit. Why not refer to species richness instead of alpha abundance?

Line 224-227: Were these ratios averages across all plots from controls and treatments? This should be stated explicitly and std deviation or stand error should also be presented for these values as you did in Table 2.

Line230-231 Why does the sum of the treatment and control plot not arrive at 97 (72+27 =99???)

Line 235-236Title of table two is not explicit enough. What is alpha abundance (species richness?). It might just be a formatting issues

Line 241-244: This statement seems in direct contradiction with the one on line 222-224 which stated: The number of species in treatment plots was higher for all species groups  ? please explain why and explain your results more clearly.

Line 248-250: I’m not sure I understand why you say When all species are considered together and then present results by groups (bryophytes, lichens, vascular). This is confusing, I assume what you mean is the total abundance of bryophytes decreased, total abundance of lichens.

Line 267: Figure 1A-D. Although there is nothing wrong with this I found it odd not to have the axis scales and x and y ordination on the plots. Could have also just added the species vector instead of having 4 different figures.

Line 281-286: For reindeer lichens and other lichens why say that there is a difference but not say higher or less as you did on line 277 for feather moss?

Line 302: If DWM is important for bryophytes and lichen why did you removed them from the plots in this study??? Shouldn’t you put a reference for this statement I’m sure there are plenty available.

Line 309-309: This is not supported by your statement on line  241-243. Also I don’t recall seeing any frequency results being presented in the results so how can you state this here?

Line 311: You mention see also ref 4. Does this means you find similar results as this study? Maybe state that explicitely.

Line 317-319: Would be interesting to expand on the successional dynamics of lichens in these type of forest. How much time does it take for their abundance to increase in these type of forest? Lichen are not know to have rapid growth and dispersal, no? Shouldn’t it take them a lot more time to achieve higher increases. Would have been nice to discuss and elaborate a bit more on these questions

Line 321-322: I’m not sure about your statement where overall species richness was substantially higher in treatments plots. Maybe this is in the appendix but I do not see this results in the version of the manuscript that was submitted?

Line 342: what is the reason according to you that explain the lack of pine seedling?  Lack of seed source, to harsh dry conditions due to canopy opening? Maybe the removal of all the woody debris removed potential cones from releasing their seeds?

Line 351: Hard to say it was a central cluster without the ordination axis show on the graph

 

Line 365 to 387:I really liked this paragraph and think your statement are both supported by your finding and the existing literature!

 

Finaly my first PhD chapter looked at what drove the understory vegetation in mature lodgepole pine forest and could be of interest to the authors. Here is the reference for their information

Gendreau-Berthiaume, B., S. E. Macdonald, J. J. Stadt, and R. J. Hnatiuk. 2015. How dynamic are understory communities and the processes structuring them in mature conifer forests? Ecosphere 6(2):27. http://dx.doi.org/10.1890/ES14-00308.1

 

Author Response

Replies to reviewer 1

 

L 79. Sentence remedied

 

L 115-116.  Although we specifically do not present hypotheses, we do make predictions.  These predictions are specifically based on responses of vegetation after 19 years of canopy opening.  Yes, we did have a sampling in 2005 but this was a separate study that used somewhat different sampling methods so we cannot make statistical comparisons.  However, I added a sentence or two about the results from this sampling that may make this clearer.

 

L 156-158 and L 158.  I have tried to justify these actions to make it clear that the study was not one of logging mechanical damage, but was restricted to effects of canopy opening.  Note however that after logging and during the 19 years post-harvest DWM increased two-fold mainly from tree fall resulting from wind damage in the open stand.

 

L 173-174’. Braun-Blanquet has a scale of x and then 1-5, really not that different from our 1-4 scale that we have used extensively in our peatland studies.  Our scale is somewhat less complicated than the B-B scale, but is designed for bryophytes and lichens, concentrating on the lower abundance levels that are important for ground layer species where only a few species reach dominance greater than 50%.  Note that the ordinations are based on these values, but that the over-plots (bubbles) use perimeter abundance from the feather mosses and lichens.  The scale is based on that used in Scandinavia where we follow their view that the top value is any cover over 50% and means the species is ‘abundant’ in the plot.  It is also interesting that among the bryophytes and lichens in our plots in this study, almost no species was recorded with a value of ‘4’.

 

L175 etc.  The font in my copy is all the same.  Must be a computer glitch

 

L 207.  Now clarified on line 217.  Yes, the functional groups are included.

 

L 217 clarified in line 194.

 

L218-219.  Now clarified on line 241.

 

L 222.  We included the supplementary material in our submission!

 

L 223.  I have clarified that the statement here is for gamma diversity and it is in fact greater in treatment plots.  

 

L 224-227.  Gamma diversity has no variation, is is the total number of species in a set of plots, whereas alpha diversity does have variance - it is the number of species averaged over all the plots in a set.  Since gamma has no variance in my opinion, the ratios calculated from this number can’t have variance either. Thus I have not changed this.

 

L 230-231.  Sorry, I can’t add, corrected and added to methods.

 

L235-236.  I explain this above - I have added a little explanation to the methods and these are referred to in the figure legend.

 

L241-244.  The difference is that first it is gamma diversity (landscape - increase) and second in alpha (plots- stays the same). Thus individual plots with relatively similar number of species are individually different (high beta) yielding an increase in landscape diversity.  This is discussed in the discussion section under species diversity.

 

L248-272.  I have clarified now on lines 272-274.

 

Figs 1A-D. I guess I really like how the ‘bubbles’ show the variation in various abundance’s, so that why we used these instead of species vectors which for me, hide the variation.

 

 

L281-286.  I rephrased this, you are correct to point this out.

 

L 302.  We didn’t remove DWM except for the that resulting form the logging (as we state in the methods).  Also I added material about the post-harvest changes in DWM.

 

Line 309.  Although I have deleted the ‘frequency’ statement, it seems to me if alpha diversity is higher, then it follows that species frequency must also be higher.  But I admit we decided not to include our ‘occurrence’ data so it is deleted.

 

Line 311. Clarified.

 

L 317-319.  Indeed, lichen long-term succession is interesting.  I am I unaware of any really long-term study with real data that examines this.  There are lots of suggestions based on observations and for sure lichens do not response quickly.  But I think our concluding remarks address this as best we can by introducing the idea that lichens for the first 2- years or so at inhibited by the presence of soils with high organic matter.  I think we have done what we can with our data on this.

 

L 321-322.  I think this is a matter of being clear on the three types of diversity measures we used.  From Table 2 it is really clear that gamma (what I call here ‘overall, is greater in treatments.  I have tried to make this clearer.  It is further discussed on line 358 and following lines.

 

L 342.  Good point - I have added comments in the results L 244-247.

 

L 351. Changed from ‘central’ to ‘one’ and we quantified the axes in the ordination, but note that in Primer, the outputs have no quantification.

 

L 365-387.  Thank you.

 

Your publication - we have referenced this and it was very useful.

 

 

 

 

 

 

 

Author Response File: Author Response.docx

Reviewer 2 Report

The paper describes an experiment where the canopy was open through variable stand removal. It goes on to indicate the effect this treatment has had on the understory vegetation in particular lichen and mosses after 19 years. The paper is well written and the authors gave a solid and strong explanation of the observations. This paper can enlighten other researchers and land managers that are seeking to increase the biodiversity. It can serve as well for forest managers in the case they want to conduct some harvest while maintaining the functional diversity of the site.  However, I have a few reservations that can be found here.

 

Major:

First, in my understanding from the paper feather moss is a shade tolerant species. If that is the case, then the hypothesis of expecting its persistence or its increase on the site after the opening of the canopy is not warrant.

Second, the statistical analysis the authors conducted could be improved. They failed to rigorously. For some variables they combined all the treatments and compared them with the control. This approach may mask valuable information because the data from different treatment does not guaranty a same distribution (multi modal). I suggest that they perform a comparison from the control to the treatment and among treatments as well. This may change the story.

 

Minor concerns:

 

L46: you are missing an adjective after “… few environmental…” or it should be rephrased

L74-76: It would be great to expand on how bryophytes and lichens react to the forest disturbance. Just limiting yourself to that statement is not helpful to the reader and does not make your argument strong either

I like very much how you expand on showing discrepancy in results from different researchers. However, it would be interesting to outline the conditions in which each experiment was conducted. For instance, you highlight a study conducted in finland. It would be great to provide the time frame. How long after the variable retention logging, the experiment was conducted. It may explain the discrepancies. Give more details on the research

L93-109: I suggest reformatting the paragraph and moving it to material and methods. It is more a description of the materials than the formulation of the problematic

 

L140: It is better to replace the table by a map. The study area is an area and giving coordinates of a single point does not help

 

L185-198 The authors are mixing in the document different font size. Is there any reason for this mixture? Otherwise I recommend a uniform font size in the whole document

 

L210: I suggest that the authors perform ANOVA or Kruskal-Wallis tests since it will allow them to see the difference if any between treatments that are variable thinning and the control. They can then perform a  post –hoc test, if necessary, to see which treatment are significantly different from others. The approach they have adopted only allows to compare the treatment to the control. The information whether 40% or 60% thinning, to instance, has a different effect is sound.

 

L221-228: The authors aggregated all the treatment and compared them with the control. I suspect that because this aggregation leads to increase in variability (data from different canopy removal must be multimodal) that lead to non-significant student tests. I recommend that the author split the data and perform tests that allow to compare the control with other treatment as well as the treatment among each other.

 

Figure 1A-D: could you increase the resolution and the size of the annotations on the plot. It is hard to read. The caption of the figure has some problems as well. There is spacing missing between some words and there are other extraneous spacing in some words.

 

L279: replace then by than in “Most treatment plots…”

 

Author Response

 

Replies to Reviewer 2

 

First concern about shade-tolerance.  I have modified the statement on line 120 to make this clear.  We expected that as the canopy increased in cover the mosses would recover - but unfortunately in these old pine forests the canopy did not change and the moss did not recover.

 

Second concern on the statistics: As we discuss in the results, the thinning treatments at the stand level had extremely varying results at the plot level, or put another way, the thinning treatments were 1) highly variable, and 2) the thinning by volume did not produce meaningful canopy removal at the plot level.  We discussed this on lines 218-224.  I now add the ANOVA results for this showing that the canopy cover removal treatments were not significantly different from one another nor were the responses of the feather mosses and reindeer lichens.  It is also in these lines where we show that the canopy cover and tree recruitment have not changed over the 19 years.  In fact, with no recruitment and blowdown in the opened stand the canopy has opened more after 19 years.

 

L46 (really 52 in my copy). Thank you, this is changed.

 

L74-76.  I have added a comment, but the following lines give the results from a number of studies on reactions to disturbance.

 

Lines 90 -95 - I have added a sentence that makes it clear that all of these studies were done relatively soon after disturbance in contrast to ours.

 

Map concern:  I have added a google map showing the locations to the supplementary material.

 

The font sizes are all the same in my copy.

 

L210.  See above for comment - We have added some stats here to demonstrate that the treatment removals were not consistent at the plot levels.  This is why we chose to examine effects of canopy cover reduction, rather than the treatments by volume.  By the way we make the point later on that maybe stand level specific thinning does not have similar results at the plot level.  

 

L221-228.  See comments above.  We address this with the ANOVA’s that we added.

 

Figures 1A-D>. The resolution will be better when we submit the final jpeg’s (these are pdf’s in the review copy).  We have remedied the size of the fonts to make the figures clearer.

 

279.  Done.

 

Round 2

Reviewer 1 Report

Your response to my concerns where well adressed and this paper is now ready to be published. I would have liked to see the Appendix before signing but I trust the editor to validate them before the final OK on the paper

I attached my responses to your responses as well as a few minor things to change

Best regards

Comments for author File: Comments.pdf

Author Response

Responses to reviewer 1

 

I believe I addressed all of the comments.

 

L 173-174:  I added a sentence as the reviewer suggested.

 

L 222:  Our map shows the location of the three sites as referenced in the sentence.  Showing the stands within the sites would not add to the information.  I like the addition of the map - nice suggestion.

 

L 224-227:  I define beta as we use it again.

 

L 281-286:  Done.

 

Other comments:

 

There is a figure (2) in the supplementary material showing drawing of the plot design.

 

Line 250:  Thank you!!  the ‘not’ should not be there.

 

Yes, there is an appendix with all species listed that we recorded.