Lack of Cascading Effects of Eurasian Lynx Predation on Roe Deer to Soil and Plant Nutrients

Round 1

Reviewer 1 Report

(Same comments as given to editors.)

Review:

The authors compared soil and plant nutrient characteristics 0, 0.5, 2, and 20 m away from lynx-killed deer carcasses, about 2 years after the deer were killed. The season during which the deer were killed (winter / summer) was included as an additional explanatory factor in their analysis. The particular kill site was also included as a random factor in the models, presumably to account of geographic differences in soil type or other environmental factors. The parameters analyzed from both soil and plant samples included C:N ratio, N, NH4+, NO3−, P, PO4−, Ca, K, Mg and Na. No significant effects of kill season or distance from the kill were found for any of the measured parameters. The lack of significant effects contrasted with the authors’ initial hypotheses. The authors thoughtfully discussed the possible reasons for the lack of carcass effects in their study, including the small size of the deer carcasses, consumption of soft tissues by mobile predators and scavengers, and the long time elapsed since death. They also remarked on methodological and environmental differences between theirs and other similar studies that might help explain the contrasting results, and they cautioned against generalizing conclusions about predator effects across ecosystems without accounting for regional differences.  

The manuscript is concise and well written, with results that make a modest but valuable contribution to our understanding of indirect effects of predators on ecosystems, and how those effects vary with context. I think that is should be accepted for publication, pending clarification of some minor issues raised below-

The current title is misleading, because no effects of predation on soil and plant nutrients were actually observed. A title that simply states the results of the study would be more appropriate. E.g., “No effect of lynx-killed deer carcasses on soil and vegetation nutrient parameters after two years”

Lines 36 and 37- Not all large carnivores have ungulate prey; cf. sharks. Perhaps you should specify that you’re referring to large terrestrial carnivores.

Line 90- Specify the range of dates included in “summer” and “winter,” respectively, and how these relate to the “decomposition season” you reference later.

Line parallel to contour of landscape is appropriate, though downhill influence might be underestimated. I.e., there could be a “plume” of nutrient influence downhill of the carcass. Have other studies looked at effects of slope on nutrient transport through forest environment? Were slopes steep at any of your sites?

Lines 114-121: Include more detailed information on sample processing and analysis procedures, or references to the protocols used. Different ways of processing solid materials- drying, grinding, acidification, etc., can affect results. Enough information should be included or referenced for readers to be able to replicate your study accurately.

I think that the statistical analysis section would be more clear if the basic statistical approach (type and structure of models used, and number of models compared) was fully described before getting into the details of how the response variables were transformed. What are the three parameters in the minimal models where K = 3, and can you explain more clearly how site was included as a random factor? Was time since kill included as a factor in any of the analyses? You mention that the range of times since kill was 20-29 months. Could time since kill have confounded your interpretation of the effect of season of kill?

Author Response

Please see attachment.

Author Response File: Author Response.docx

Reviewer 2 Report

Review of Diversity 915595

 

Dear Authors,

 

This is a very interesting, small study that I highly enjoyed learning about.

 

The question and design are both straightforward and novel, with broad interest and appeal. The analysis is simple and adequately done to answer the question. The manuscript is well organized and written. All-and-all, a nice contribution. Well done. Thank you for doing this work.

 

My comments are few and rather minor. Mostly they are aimed at polishing the presentation and main points of the work as I see them. One more substantive comment, however, is the need to clarify how carcass sites were relocated so precisely 20-29 months after the kill. This is key information for the study that needs to be included if the reader is to believe your design and results.

 

Please find below my detailed comments.

 

Good luck revising your manuscript.

 

Detailed Comments:

 

Line 2: Perhaps the title needs revised given that you did not detect any cascading effects.

 

Line 17: missing a comma after “flexuosa”

 

Line 50: Should “large herbivores” be included here?

 

Line 52: Change to “below-ground”

 

Line 57: Suggest deleting “large” here and throughout. Many would not consider Lynx lynx a large carnivore in the sense bears, tigers, and lions are, for example.

 

Lines 56-58: This long sentence is awkward. Please rephrase. In the process be specific about the aim of the work, then another sentence or two about the design and study system.

 

Lines 59-65: Its great you have this predictions. These sentences however would more work better as text than a numbered list. More importantly, it would be helpful to the reader if you provided context/rationale for your predictions by drawing from the available literature other examples.

 

Line 68: Replace “kilometers” with “km”

 

Lines 84-87: I believe that all of the information in these sentences would be better suited for the Acknowledgements.

 

Line 90: Some elaboration on relocating the 18 carcass sites is warranted here. Specifically, how did you find the exact spot (within 1 m) of where the carcass was? This is key because if locating the site 20-29 months later you were off by, say, 10 m it could influence significantly the findings. Please clarify this in detail at this juncture.

 

Line 102: missing a comma after “flexuosa”

 

Line 104: Any chance you have a photo of one of these sites where the carcass killed much of the vegetation that could be included? I believe that would be most helpful to the naïve reader.

 

Line 109: Delete “in the Netherlands”

 

Line 130: Replace “a linear mixed model approach [35]” with “ a generalized linear mixed model (GLMM) framework [35]”

 

Liine 176: in the Introduction you did not discuss “hypotheses” – you discussed “predictions”. Please be consistent.

 

Line 177: I believe you need to provide scientific name for muskox, bison and kangaroo here.

 

Line 186: Again, a photo of what is typically left of a lynx-killed roe deer, would be most helpful here.

 

Line 189: There are several different key points in this short paragraph. Please elaborate on them and separate them so that they are not lost to the reader. The second point (Lines 192-195), I believe, is a major comment resulting from this work and should not be lost – I’d put it in the Abstract and Introduction as well. Maybe the concluding paragraph too.

 

Line 191: delete “real”

 

Lines 203 and 205: Remove scientific names of American bison and kangaroos as they should be at line 177 instead.

 

Line 211: Thank you for proactively addressing sample size (and early the time lapse). As for sample size, I think 18 is good, although the summer sample is small (n = 6).

 

 

Author Response

Please see attachment.

Author Response File: Author Response.docx