Review History


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Summary

  • The initial submission of this article was received on November 13th, 2012 and was peer-reviewed by 2 reviewers and the Academic Editor.
  • The Academic Editor made their initial decision on January 14th, 2013.
  • The first revision was submitted on January 21st, 2013 and was reviewed by the Academic Editor.
  • The article was Accepted by the Academic Editor on January 28th, 2013.

Version 0.2 (accepted)

· · Academic Editor

Accept

I appreciate your careful attention to the suggestions from the reviewers, and am grateful that two of the reviewers provided such detailed and constructive comments. The paper is much improved.

However, as I read through your "track-changes" copy I noticed a number of careless typographical errors. There are probably others that I did not notice.

Please carefully proof-read the final version that you submit for publication, correcting all the errors I noticed, as well as any similar problems that I didn't notice (I was not proof-reading, just scanning).

The following line numbers are from the track-changes copy, but the one that I checked (line 217) was also in the pdf (line 228). Presumably you can locate the others.

217 flowers NOT flowerd (damn querty)
490 delete "at least"
507 word missing - decline and ????
543 word missing 4-5 [years?]

Version 0.1 (original submission)

· · Academic Editor

Minor Revisions

While one of the reviewers was not very enthused about the novelty of your results, it is quality, not novelty, that is the main criterion for PeerJ. The other reviewer makes a number of very good suggestions about how the manuscript can be improved. In particular, I expect you to include more background and comparison with the impacts of other major tree diseases that have affected the forests of the Northeast. I also believe you can tighten up the prose and remove some unnecessary description and duplication as suggested by the reviewer.

Reviewer 1 ·

Basic reporting

Only one comment: Since rationale for paper rests on understanding consequences of loss, specifically, of foundation species, it seems to me that there should be some recognition of the relatively large literature on consequences of loss of American beech due to disease. There are published studies that address at least some of the questions posed here about community/ecosystem effects, and this is in the same/similar ecosystem. There's also some work on ecosystem/structural consequences of loss of American elm in wetland forests in same region.

Experimental design

Generally sound in design, but a few things to note (these are detailed in notes for authors)

Biggest conceptual/structural issue: 'Hypotheses' given as motivating the study are not mechanistic hypotheses, but predictions that are given without explaining the mechanistic reasoning behind them. It would be better to present hypotheses as functional relationships/mechanisms suspected to be at work, and then to derive these predictions from them as means of testing hypotheses....

Methods:
- there are issues around interpreting effects of logging as due to hemlock removal when other trees were removed as well (see comment line 289 and elsewhere).
- Need to clarify issue in comment on L 251 re estimation of aboveground NPP; the conclusion as stated in lines 520-521 does not follow for me; the 'sharp pulse' can't be read as reflecting an increase in aboveground PP as implied by this language; it's break-down of accumulated pool of canopy structural biomass...

Validity of the findings

My only issues here concern presentation: Results section are unnecessarily 'prosey' repeating details in text that are obvious in tables/figures and not important in emphasizing main points, telling story. Discussion tends to repeat details from Results unnecessarily. But also does good job of synthesis and putting things in context of literature...

Comments for the author

These line-by-line comments complement and elaborate on the general points above. I also note that I think the whole paper tends to be a bit more discursive than need be, and migth be shortened to make for a more compact 'read' without loss of substance.

l23: "remains an open question whether particular species with particular characteristics will disproportionately change how ecosystems function" It remains an important question, but it would be appropriate to recognize that community/system consequences of loss of specific species HAVE been addressed for some cases -- maybe most relevant here, a number of studies on consequences of loss of beech due to beech-bark disease -- another late-successional 'foundation species' in similar forests... Quite a few papers over last 30 years...
(Odd that beech not mentioned in next paragraph, since it's closer parallel in many ways than the cases mentioned)

l38: extra "and"

l98: 'a' rather than 'an'

l96-103: This sentence needs reworking -- probably breaking up into two or more sentences, maybe a little expansion (especially as it lays out basic conceptual structure). Currently diagrams as 'experiment compares and contrasts rates.... to two mechanisms...', which isn't quite right.

l105: 'following' rather than 'caused by'? attribution of causality needs to follow design that justifies it...

l107: "the hypotheses": These are predictions, but don't really spell out reasoning. I'd prefer to see 'hypotheses' stated in terms of processes or causal relationships being focused on, and these kinds of pattern predictions stated as testable predictions of those hypotheses... WHY are these expectations reasonable?

L118: this prediction is more far-reaching and less obviously reasonable than first three. Convergence with hardwood controls seems to requrie several assumptions that aren't really addressed here.

L177-178: The rationale for cutting of hardwoods and white pine is not clear, since experiment is directed at detecting effects of removal of hemlock? -- ah, I see from subsequent paragraph that it's intended to mimic a salvage operation. Okay, but that means predictions given in intro have to be in terms of more complex differences between treatments -- not just whether hemlock is felled or dies standing, but whether other stuff is killed/removed or not...

L210: Grasses and sedges to genus only: This is too bad, since sedges can constitute a good chunk of the herbaceous diversity in such forests...

l251: litterfall as index of ANPP: This seems okay EXCEPT for one important issue; does it include disintegrating twig/branch material from girdled trees on the girdled plots? That would NOT be appropriate as a component of current ANPP -- would lead to overestimation of post-treatment ANPP for a few years as canopy structure breaks up!

l288-90: Back to question about cutting pine and hardwoods; in the logged plot, doesn't difference represent MORE than contribution of hemlock (i.e., that of other trees cut)?

l300-301: Yes, but that heterotrophic respiration is likely to be enhanced by breakdown of roots of killed trees in experimental plots?

l343-344: 'increased abruptly.. remained stable' This is not visually evident for both logged plots; one instance COULD be interpreted this way; the other looks pretty gradual to me with increase continuing in the last sample interval

l410-424: This is an example of over-description; I'd suggest reducing amount of verbal retelling of what's clear from tables/figures -- especially when there's no meaningful pattern relative to hypotheses/predictions...

l448-449: It might be possible to draw some something from literature on response to beech bark disease mortality on this front...

l522; this 'pulse' should be interpreted as related to increased ANPP as implied by the foregoing sentence; it's a transient loss fo a biomass reservoir and that should be clearly distinguished...

FIGURE 2: There needs to be an in-graph legend matching treatment to color.

Reviewer 2 ·

Basic reporting

So, let me think about this. If I logged a stand and removed big trees, what would I expect? Let's see - decreased basal area, decreased cover, more CWD on the ground from felling the trees, less litterfall (because there are fewer big trees), lower soil C and N flux because of decreased litter input but slowly recovering as the canopy closed and litterfall recovered. And if I girdled trees but left them standing? Smaller changes in the above properties.

This is what this experiment demonstrated.

So what new things have we learned?

Experimental design

The experimental design was fine. I just don't think that the results teach us anything new.

Validity of the findings

See comments in other boxes.

Comments for the author

This experiment was obviously a lot of work and well-executed, but I don't find any of the results to be all that surprising. If you wanted to examine specifically what the loss of hemlock did compared to the loss of other "foundation species", the experiment should have been repeated removing another species with very different potential effects on the ecosystem, such as sugar maple. But that would have been a massive experiment.

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