Interspecific Growth Reductions Caused by Wild Ungulates on Tree Seedlings and Their Implications for Temperate Quercus-Fagus Forests

Round 1

Reviewer 1 Report

This work has left me with many questions. I was surprised by the formulation of the research question and the general concept of the study. I was even more surprised by the authors' detachment from the broader context of the issue, which I will describe in detail below:

1. It is unclear which kind of forests the authors studied - primeval or secondary. If the study concerns secondary forests, it is normal to expect that they would pass through several natural succession stages until they become primeval forests. Do the authors seek to fix the forest succession at their present stage? If so, why? Is it because they believe that forests at the current succession stage are more resilient to climate change? This is not the case, as I will explain below. Are there other reasons, such as biodiversity? However, the authors' efforts will not change global tree biodiversity, but may destroy the west European subspecies of red deer, which is already going through a genetic bottleneck (Valerius Geist, 1998).
2. Forest ecosystems in the middle latitudes of Europe will change differently under climate change, with more diseases affecting autochthonous species and more invasive species outcompeting local species. Removing deer species from forest ecosystems may make this change more dramatic and catastrophic because deer, unlike other ruminants, are ecologically opportunistic and can easily switch to new plant species, thus ensuring a certain ecological resilience for the entire ecosystem. To forecast the ecological consequences of each wildlife management decision, a careful and in-depth study of each factor involved in the ecosystem evolution is needed. This work cannot be done solely by hunting associations.
3. The European ruminant species community is already significantly depleted, with Bos primigenius extinct, Bison bonassus and Alces alces absent from Western Europe, and the remaining two species, Cervus elaphus and Capreolus capreolus, unable to occupy the entire spectrum of unfilled ecological niche of large herbivores. The European subspecies of red deer (Cervus elaphus elaphus) already suffers from population fragmentation, isolation, bottleneck, inbreeding selective hunting, and uncontrolled hybridization with other forms of red deer. The situation with roe deer is not any better. As I can see, the authors of this study are not familiar with all aspects of the problem.
4. The most probable consequence of the authors' proposed solution is an increase in the forest composition of birch, rowan, etc., and a decrease in Quercus. There are some examples of such secondary forests with modified (and impoverished) species composition.

This work may be published as a case study demonstrating how deer can influence the survivorship and recruitment of saplings, but I do not recommend publishing the paper in its present form. Firstly, in my opinion, the data are too limited and the conclusions too superficial to make this kind of recommendation. Secondly, maintaining forests at their current succession stage does not protect them from climate change or from invasive species that may occur as a consequence of climate change. The recommendation to reduce the deer population is too simplistic and has no clear scientific support. Therefore, the paper cannot be published in its present form.

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Reviewer 2 Report

This study revealed the effects of ungulates on understory vegetation such as vegetation cover, seedling height growth, seedling density, based on data from many fenced and unfenced plots. The Introduction provides a good review of the effects of ungulates based on many literatures. In fact, many studies have reported the effect of ungulates on forest vegetation and regeneration. The hypotheses (L83-87) were not specific for the presented data and analyses. Adaptation to climate change and succession dynamics were not examined but only discussed from the results. Therefore, the findings of this study were not clear, although a wide range of effects were discussed. The results described the in this study did not seem necessary for most part of discussion. The authors need to present more specific hypotheses that can be examined with the data and analyses. Introduction and Discussion should focus on these points.

 

Table 1 is incorrect.

 

Italics must be used for the genus and species when using Latin names of organisms. The authority for a Latin name is usually given at least when it is first mentioned, but it must not be italic. Latin names in the figures does not need the authority.

 

Use consistent styles (italic, subscript, etc.) for abbreviations, equations, units (e.g., EAI, m^-2, km²).

 

The first two paragraphs of the Results were not related to the results (Tables or Figures). If these were the summary or the results, these paragraphs were not necessary, and these should be mentioned in each subsection. Some types of cover were recorded in this study, and I could not identify which cover ‘vegetation cover’ (L202) mean.

 

Replace ‘pvalue’, ‘p-val’, ‘p-value’ with ‘P’.

 

I could not find Fig. 5B and 5C (L417).

Author Response

The authors thank you for the comments and questions.

We considered the main comments appropriate, but had an interrogation concerning the advised option. Other remarks were fully integrated to the manuscript. We chose one possible solution, but are open to move parts of the results to supplementary materials on request. 

Please find the detailed responses in joint file. Studies cited in the paper are referenced using the numbering of the manuscript and within brackets []. Lines numbers in our answer are the numbers of the final version ("no mark" must be chosen in track change options of the new version of the manuscript).

Hoping this new version of the manuscript and our answers satisfy the requests adequately. 

Author Response File: Author Response.docx

Reviewer 3 Report

This manuscript has so many low-level errors that it is difficult to focus on its quality. I hope that the authors will take their submissions seriously.

 

Lines 1-3 The title is even wrong, such an error is outrageous.

Lines 99-103 Latin names should be italicized and initials should be capitalized. Please check yourself for similar errors elsewhere.

Lines 111-115 Please optimise the layout of the table, it looks awful now.

Lines 226-229 Are there no standard errors in these data?

Line 258 Is the manuscript not finished yet?

Lines 262-263 Spp. does not require italics.

Author Response

Please, find our detailed response in attached document. 

Author Response File: Author Response.docx

Reviewer 4 Report

The quality of English needs for some revision. For instance, the present variant of the title sounds not well understandable. In both abstract and the text, there are other problems. The authors should conduct the revision of the language quality.

The abstract is quite well written. However, I recommend to use only Latin names for the organisms, by avoiding common names.
The list of key words should be revised. Please, do not use words and sentences, which are present in the title.

The section Introduction is also written well and clearly. The authors overviewed the studied problem, and highlighted the main aspects reviewed in the paper. The authors stated the aim and research tasks of the paper. It is well done in comparison with other studies.

Materials and Methods section should also be revised. English needs to be improved. Some references are present in the form of "Author(s), Year" instead of the number in quadrate brackets (for instance, [89]). It should be corrected. 
In Fig. 1, please, italicize all Latin names, and the first letter should be capitalized in them. 
All names of the organisms (not only here, but in the whole text) should be Latin, not common. Latin names should be italized in the whole text.
However, the Data analysis subsection is written clearly. Well done.

In general, the section Results is well written.
However, some problems are presented. For instance, see line 258. The text fragment is marked in yellow.
In addition, in captions of figures, see * : P< 0.05 ; ** : 0.05 < P< 0.01 ; *** : P< 0.001. But what is about p-values, which are between 0.01 and 0.001? This designation of p-value does not take into account such values. In addition, please, consider that "P< 0.05" and "0.05 < P< 0.01" are the same. In other words, "P< 0.05" includes values, which are "0.05 < P< 0.01" and values, which are "P< 0.001"  Please, revise these designations.

Discussion should also be revised.
For instance, lines 330-334 represent the obtained results by repeating them. Please, place all results in the section Results. In Discussion, you should leave only discussing and explaining the obtained results.
Please, revise other parts of this section by avoiding the irrelevant fragments. Other parts of the sections are well-written. A wide range of relevant references was used for discussing the results. My compliments!

The section Conclusion is relatively well written. I think that it is well done.

Therefore, just minor corrections are needed. 

Author Response

Please, find our detailed response in attached document. 

Author Response File: Author Response.docx

Reviewer 5 Report

The main comments/suggestions on this article are as follows:

1. In this study, 734 pairs of plots were monitored for 5 years. Is it possible to quantify the effects of ungulates on seedling growth, density, and herbaceous cover, and is it possible to quantify the positive or negative effects of ungulates on forest regeneration succession through available data combined with mathematical models?

2. When conducting the field survey, could you get the data of ungulates? could the relationship between the density of ungulates and the effect on seedling growth be analyzed?

3. On the subsection 2.2, except the plots distributedin the oak and beech, and spruce and Douglas fir where the else 38 plots located in? 507 and 189 in not 734.

4. On the subsection 3.5, how the environmental factors of temperature, atmospheric humidity and light intensity were obtained. These should be describedin the data collection. Please add.

5.The title of the discussion still needs to be determined. For example, On the subsection 4.3.1, a large part of the discussion deals with the issue of light conditions, and the title only reflects the relationship between seedling height and ungulates browsing. The title should correspond to the content.

6.The details of the figures and table in the article need to be revised and have been annotated in the text.

7.Article layout problems, the left margin is too wide. It’s not very beautiful. If the journal requirements, please ignore this.

Author Response

Please, find our detailed response in attached document.

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

I appreciate the efforts of the authors to give answers to my remark but, unfortunately, this is not enough. The entire concept of the article is chaotic and the conclusions are not scientific at all. I was very brief in my previous reviewing and now I understand that it is necessary to explain in details why the article is bad and cannot be published.

The authors made a long-term observations how cervids may influence the deer saplings survival and recruitment and how influence a secondary forest ecological succession. There is nothing new here, but of course this kind of studies have to be done because their represent the basic material for further analytical studies of forest ecological successions.

However, the entire concept of the article and far reaching conclusions that are not supported by scientific arguments are just catastrophic. The authors noted already signs of climate change impact over the forests: they recorded an increased rate of diseases of threes. And immediately propose to diminish drastically (below the carrying capacity) the number of deer populations. I DO NOT SEE ANY RELATIONSHIP BETWEEN TREE DISEASES AND NUMBER OF CERVID POPULATIONS. Those are not deer who disperse the tree diseases and those are not deer who are responsible for the climate change provoking tree diseases. Please, be serious, you are submitting an article to a scientific journal and as a reviewer I am embraced by the weak methodological and theoretical basis of this study.

You say that Cervus elaphus is a least endangered species. May be, if compared to eastern lowland gorilla. But the populations of European red deer are already perturbed by population fragmentations, inbreeding, genetic pollution, and selective hunting, as I already wrote in my previous reviewing. But authors just reject the problem, showing and infantile and irresponsible attitude. Did you made simulations of deer population survivorship (at local and continental scale) as a consequence of you recommendation to reduce the population size below the carrying capacity level? I am sure that you did not. There is a very good population survivorship simulation tool VORTEX that I recommend, so, at least theoretically, you will be aware about the consequences of you recommendations.

You say that the populations of deer became too big. Which are criteria? We are scientists, not children, we need clear methodological criteria and exact data. May be the biomass of herbivores is too high if compared to the primary ecological production of the forests under study? Did you made such estimations? This is an important methodological and factual basis of this kind of research that is just missing in your study. Your vague recommendation (“below carrying capacity”) is unacceptable and opens the way to all kinds of abuses and misuses.

Now about the biodiversity and natural ecological forest succession. Your conclusion is that it is necessary to diminish the number of populations below the carrying capacity that will stop the natural ecological succession and thus will increase the tree diversity and will increase the resilience of north European forests to climate change. This is just ab absurd idea that has no any scientific support.

Firstly, if you need an artificially increased species diversity of tree plants, better to create a botanical garden and enjoy its species diversity. Your attempt to create an artificial resistant to climate change forest is just a utopia and has nothing to do with science.

Secondly, the paleontological record of this part of Europe shows that during the warmer periods of Pleistocene, the dominant biomes were marshy wet forests, no any sign of aridisation. The authors are not aware about possible consequences of climate change and their proposed scenario of climate change consequences is just a science fiction.

 

Thirdly, nothing can safe forests of middle Europe forests from climate change, even if you will exterminate all herbivore animals. I suggest to concentrate your efforts on the changes that naturally develop in the forests under the climate change, to monitor the trees that are most affected by diseases, to monitor the new invasive species, and to make records of changes in sapling developments and recruiting under the conditions of climate change. This is the knowledge that has a real scientific, economic, and social-political value.

Finally, I do not understand why you mention wild boar in your study, since it is not a ruminant herbivore (rather an omnivore). I strongly suspect that this paper is aimed to give a pseudoscientific support for political decisions to increase quotas for hunting. I am a scientist and as a reviewer I do not like to be manipulated, not to be associated with this kind of manipulating articles. Therefore I confirm my decision that this paper should be rejected, since it does not correspond to the scientific standards of the journal and may cause reputational damage to the journal.

Author Response

No response addressed. 

Author Response File: Author Response.pdf

Reviewer 2 Report

The manuscript has improved, but there are some sentences where the revision was not sufficient (e.g., L258, L314).

Author Response

Please, find our detailed response in attached document. 

Author Response File: Author Response.docx

Reviewer 3 Report

The authors have revised the manuscript extensively.

 

The traditional view is that herbivores directly inhibit plant growth, but one recent study found that isopods stimulate fungal activity while feeding on fungi (Chen, Y. et al. J. Fungi 2022. https://doi.org/10.3390/jof8040348). This is an interesting result. Does a similar phenomenon exist in ungulates? Perhaps you could try to discuss it.

Author Response

We acknowledge the reviewer for his suggestion to discuss potential positive effects of ungulates browsing on tree seedling growth.

We add a citation of a recent study that documented positive impact of moderate browsing on the seedlings of some species in introduction (L71-72). This further promote the fenced-unfenced design and the observation of seedling growth rather than browsing rates observations when study aim to understand consequences on tree recruitment.

Potential positive impacts of ungulates on vegetation growth were discussed at section 4.2 (lines 304-313).

Some typos were corrected.