Promoting Optimal Habitat Availability by Maintaining Fine-Grained Burn Mosaics: A Modelling Study in an Australian Semi-Arid Temperate Woodland

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

This is a well written manuscript and covers an interesting subject.  It is worthy of publication after addressing a few clarity and methodological questions.  For clarity sake, the methods related to calculation of G and "optimal state" need elaboration because of their centrality.  Reference to another paper is not adequate in this instance.  Related to G and optimality, a number of points are raised in comments on the attached manuscript that should be clarified in the manuscript and potentially included in discussion.

Comments for author File: Comments.pdf

Comments on the Quality of English Language

A few minor edits required.  See attached comments on manuscript.

Author Response

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Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

This is an important and well-written manuscript, and represents an interesting approach to evaluating different fire regimes in terms of biodiversity conservation. There are, however, a few fundamental issues that were confusing to me, and my sense is that these issues would need to be addressed before the manuscript would be suitable for publication. Below I briefly describe the issues that I found confusing or insufficiently explained: 

 

1: The authors rely upon earlier modeling work by Kelly et al. (2015). However, I have questions and concerns about the validity of the Kelly et al. (2015) model. For example, Kelly et al. (2015) acknowledge that, for reptiles with a significant time-since-fire association, 4 of 11 species were associated with early-successional vegetation, their model assumed that the optimal scenario for reptiles would have 0% early-successional vegetation (see Fig. 2 of Kelly et al. 2015). This is simply not ecologically plausible and suggests some issues inherent in the model design, and the resulting values of G. 

 

2: The authors analyze two scenarios—one characterized by small fires and another characterized by large fires. However, fire regimes are rarely so simplistic. Typically (always?), there is a mix of small and large fires, with small fires being far more numerous and frequent, and large fires being far less numerous and infrequent, but often comprising a substantial portion of the total area burned in a given century within a particular area. The authors did not analyze such a scenario, but perhaps they should have done so.  

 

3: The large fire scenario resulted in larger habitat patch sizes. How was patch size addressed by the model? Was any ecological value assigned to larger patch sizes, at least for some of the species included in the model? If not, why not? 

 

 

Author Response

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Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

Comprehensive, clear modelling of spatial burning regimes aimed at optimising vertebrate diversity given very comprehensively described patterns of vertebrate occurrence and diversity in current mallee ecosystems.  I am not a modeler but have played with fire impacts on frogs using both experimental approaches and broad scale, landscape surveys.  This is a very clear modelling exercise that has its basis in an existing comprehensive survey of vertebrate fauna – particularly occurrene data for listed threatened species

The paper hints that the modelled burning patterns reflect historical, indigenous patch burning and that the known occurrence of vertebrate diversity is the product of those burning practices.  the burning practices suggested may maintain known, recent patterns of vertebrate occurrence but those patterns may not have maintained maximum possible, prehuman/pre-european vertebrate diversity.  I am reminded of a paper on vertebrate diversity in the fossil record in south western Australia that reports extensive vertebrate extinctions approximately coincident with human arrival: e.g., glaringly, in my memory, wombats & koalas and quite large shifts in dominant vegetation based on sediment profiles of  I think of pollen and/or leaf types: see Gavin J. Prideaux, Grant A. Gully , Aidan M. C. Couzens , Linda K. Ayliffe , Nathan R. Jankowski , Zenobia Jacob , Richard G. Roberts , John C. Hellstrom , Michael K. Gagan , and Lindsay M. Hatcher 2010. Timing and dynamics of Late Pleistocene mammal extinctions in PNAS. 107:22157–22162.

 A very sensible use of known data on a specific region that has been intensively surveyed for vertebrates. Mallee is an extensive vegetation type in south and south-eastern Australia.  Is there any reliable way these results might be extended into other mallee regions?  In its current form this result has particular value for an area where the fauna, particularly rare fauna, is already very well described based on extensive historic and current survey effort.  How well can it translate to new areas given “mallee” is widespread in South Australia and southern new South Wales?    Is there any way you can justify a translation to other regions given you do not/may not have a similar data base of occurrence of vertebrate species, particularly listed threatened species in those areas.

Author Response

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Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

Comments and Suggestions for Authors

I appreciate the responsiveness of the authors. However, I do not believe they adequately addressed my concerns about the problems with the model in Kelly et al. (2015) upon which they relied. In response to my concern, the authors noted that 2 of 11 study species that were associated with late successional vegetation were nearly restricted to such vegetation, whereas there were no strong relationships with early successional vegetation for the 4 of 11 study species that were more abundant in early successional areas. The authors used this argument to defend their conclusion, based on their model, that optimal diversity is found with 0% early successional vegetation. I do not find this argument persuasive. One of the early successional species was 1.5 times more abundant in early successional vegetation than mid-successional, and 5 times more abundant in early-successional than in late-successional. Another early successional species was nearly twice as abundant in early-successional than in mid-successional and nearly 10 times more abundant in early-successional than late-successional. These are not subtle differences; they are major differences that indicate strong habitat selection for early-successional vegetation, yet the model would have us believe that maximum diversity is achieved if there is 0% early successional vegetation on the landscape. I will not attempt to suggest here what the optimal percentage of early successional vegetation should/would be, but I do feel confident in saying that it would not be 0%, when 2 of 11 species are substantially more abundant in early successional vegetation. 

Author Response

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Author Response File: Author Response.pdf