Quantitative Assessment of the Effect of Agency-Led Prescribed Burns and Cultural Burns on Soil Properties in Southeastern Australia

Round 1

Reviewer 1 Report

Dear Authors,

Thanks for your submission to Fire.

It was a pleasure reviewing your manuscript and I think it covers such an important and understudied aspect of fire's effect on the landscape. Please see my review comments attached.

Kind regards and Happy Holidays

Reviewer35

Comments for author File: Comments.pdf

Author Response

We are thanking the reviewer for their supportive comments.

Reviewer 2 Report

The manuscript is excellent. Interesting topic, standard sequence of chapters and subchapters, correct analysis and logical conclusions.

I only have a few recommendations.

I recommend increasing the number of cited references (in accordance with the journal's standards).

I also recommend the use of Latin (scientific) names along with common names when listing tree species (subchapter 2.1).

Reference 34 (Discussion, page 13) is not clearly cited, which should be corrected.

Author Response

We would like to thank the Reviewer for their comments. We have endeavoured to cited as many references as relevant for the study. Latin names of tree species have been added. Reference 34 has been fixed.

Reviewer 3 Report

Quantitative assessment of the effect of agency-led prescribed burns and cultural burns on soil properties in southeastern Australia

Murramarang Country, Jessica Davis, Jack Simmons, Shane Snelson, Victor Channell, Katharine Haynes, Nicholas Deutscher, Leanne Brook and Anthony Dosseto

Summary

This is an interesting, straight forward manuscript, but the authors' conclusions are limited by the spatial sampling (one site only).  However, it has relevance to proposed increases in prescribed burning across Australia, North America, and Europe, so might be read more widely than perhaps the authors are intending? As such, the authors should consider a number of edits and improvements. 

Major comments:

Lead author is incorrect. This is a location, not an author. Shouldn’t the “Ulladulla Local Aboriginal Land Council” be in the acknowledgments?

Table 1 contains data from most of the Figures, so it is redundant. What would help readers is to expand Table 1 to include all of the statistics for the Figures, including sample sizes, F values, Tukey HSD levels, and P values. Also, please include more information on the Pierson’s product moment correlations (n, F value, etc.).

Authors discuss a number of possible explanations why differences are observed in the Discussion section, but do not really consider the effects of burning to potential changes in vegetation structure, species composition or litter quality, which may affect some of the measured soil properties.  For example, differences in soil moisture levels could be due to differences in leaf area among sites, and not only to the fact that soils with higher OM actually hold more water (although this is a one-time winter sampling, so growing season patterns may differ). For soil N, are there any N-fixing species that are encouraged by long-term, repeated burning, especially Indigenous burning patterns?

In this short manuscript, it would be interesting to include a table with comparisons to other ecosystems where prescribed fires have been conducted. Certainly, examples exist in the literature of other areas of Australia and North America that are estimating soil effects of Agency (management-scale) burns, so it would be interesting to cite a few.  There may also be sufficient information on indigenous burning practices, from the western USA.  This (possibly supplemental) table comparing these results to others would make this a stronger manuscript. Are the patterns the authors report supported by other research?  They do cite some of these studies already in the Discussion section. 

Citations for chemical methods and Statistics are sound. There have been a lot of high quality quantitative and isotopic studies from this group. 

Legends and axis labels on all of the Figures are too small to read.  Please use a larger font for all. In Figures 2 and 3, the authors identify the red dots as mean values, but are the error bars SD or SE? These should be identified. What, exactly, are the box plots?  It would also be helpful to identify significant differences with letters or symbols. 

Figure 5a is a result of this study, and should be moved to the Results section. Figure 5b should be in the Discussion section. It seems like the C and N measurements could also be compared to other literature values, as mentioned above. 

Specific comments (these should be by line number, but unfortunately these were not included by the authors).

There are many definitions of “soil health” in the literature, but “functionality of the surrounding environment” sounds vague. Perhaps tie soil health to “ecosystem functioning”? The term “ecosystem health” is used later in the manuscript. 

It would be helpful to describe the fire and prescribed burn history of the Indigenous vs. the Agency burn sites in greater detail. No doubt these soil differences did not originate from only one burn. 

It seems that this small study is not really providing a “comprehensive understanding” of soil effects with Indigenous burning practices, so this might be reworded to “begin to understand” or equivalent.

Authors should use scientific names with authorities on first use for the vegetation description.  Also, please reword some of these sentences as they are redundant when describing vegetation types at the sites. 

Discussion

Are Indigenous burns really cooler that Agency burns?  Are ignition patterns and fire behavior patterns different, or are they conducted at different times of the year?  The authors focus on the most recent fires, but it seems that long term effects of repeated burning would also affect both vegetation and soil properties, and this should be mentioned. 

It is interesting that soil in the Indigenous burn plot has a higher N content, but again could this also be due to N fixation and not only lower burn temperatures.  It seems that the C/N ratio contrasts with this pattern. 

The authors consider root inputs, but partially burned litter layer and forest floor material would also be incorporated (or leach) into the upper soil layers. 

Is there any evidence for clay particle “protection” of OM in these soils? 

It is unclear how the authors have demonstrated how Indigenous or Agency prescribed burning has affected “ecosystem health” if they have not tied these to ecosystem functioning. 

The format of the references is incorrect, and should include the coauthors, if any. 

Author Response

We would like to thank the Reviewer for their constructive comments.

The lead author is as per request from the Indigenous authors and collaborators of this study. For Australian Indigenous communities, Country is the holder of knowledge and as such, they have requested for Murramarang Country to be listed as an author. This is in agreement with practices encountered in other journals, for example here: https://journals.sagepub.com/doi/abs/10.1177/1474474014539248.

Ulladulla Local Aboriginal Land Council is one of the affiliations of some of the authors, thus it does not need to be listed in the Acknowledgments.

Sample size, F values and p values have been added to Table 1. We are unclear about the query regarding the Pearson’s product-moment of correlation (we assume this is what the reviewer meant by ‘Pierson’), as it does not have a F value.

The reviewer makes valuable comments regarding the effect of vegetation structure. However, since leaf area and other aspects of vegetation structure were not measured, it would be speculative to include this in the Discussion.

There were no N-fixing species observed at the site.

The suggestion of comparison to other ecosystems where prescribed burning has been conducted is valuable. The focus here is on cultural burning, and unfortunately there is very little literature on the topic (as reported in the Discussion), which prevents scope for a comparison.

We are thankful for the positive comments regarding the quality of our analytical work.

All figures have been re-drafted to include bigger labels. Note they may still look small in the manuscript but are provided as high-resolution separate files for the journal. Error bars are not shown in boxplots. What the reviewer might refer to error bars are whiskers, representing 1.5 x the interquartile range. The box is the interquartile range. We have added symbols to indicate significance on all boxplots.

We feel that Figure 5a illustrates the Discussion so we would prefer if it stayed in this section.

The term ‘functionality of the environment’ is used in the literature in relation to the definition of ‘soil health’, e.g. Arias, M.E., et al., Soil health -- a new challenge for microbiologists and chemists. International microbiology : the official journal of the Spanish Society for Microbiology, 2005. 8 1: p. 13-21.

The fire history of the study area is presented in the Study Area section. There were only one prescribed and one cultural burns, which is why this site was chosen.

“comprehensive understanding” was changed to “begin to understand”.

Scientific names of plant species are given in the revised manuscript.

Indigenous-led burns are cooler than agency-led burns. Indigenous burning techniques are often refer as ‘cool burning techniques’ in the literature (e.g. Skiba, R. (2020). Usage of Cool Burning as a Contributor to Bushfire Mitigation. Natural Resources , 11, 307-316. https://doi.org/10.4236//nr.2020.118018). At our study site, the Indigenous-led burn produced smoke but no flame, while the agency-led burn was performed using drip torches and produced waist- to shoulder-high flames. Repeated burning did not occur at the study site.

While N fixation could explain higher N content, there was no observation of N-fixing species where the Indigenous-led burn was performed.

We are unclear about what the reviewer means by clay particle “protection” of organic matter. Clay aggregates around organic matter? There is no evidence at the site this takes place.

The format of the references follows the format instructed by the journal.

Reviewer 4 Report

The authors assessed the effects of two fire management strategies, agency-led prescribed burning and cultural burning, on soil properties in Australia. They demonstrated that both methods have a positive impact on soil moisture, with agency-led prescribed burning exerting a slightly stronger influence. Furthermore, both techniques led to a reduction in soil bulk density and an increase in organic matter content, with cultural burning displaying a more pronounced effect. The study highlighted that cultural burning can be the more efficient approach, particularly in terms of reducing soil bulk density, which is a critical factor for nutrient availability and microbial activity, as well as enhancing carbon and nitrogen storage. While the concept covered in the study is not entirely novel, it allows for a clear differentiation between the effects of agency-led prescribed burning and cultural burning. Below, I provide some comments on the manuscript in the hope that they will be beneficial to the authors.

Detailed comments

# The author assesses the impact of two fire management techniques, but less review about two methods about these methods in the introduction, particularly regarding the effects of cultural burns. Have no paper to discuss the effect of cultural burning? I suggest adding more literature review about the processes of these two fire management techniques in the introduction part.

# The statistical method is clear, but it is not present in the figures. For example, in the figure 2, figure 3, and figure 4, only the data distribution is displayed without any accompanying statistical information. I suggest incorporating statistical results in the figures, such as asterisks (*) or letters (a, b, c). Additionally, some result not show in any figures and tables. Please carefully check it.

Some detail

#The manuscript lacks line numbers. I just copied the original sentence to offer some advice.

#Introducation part

“Furthermore, little is known about the effect of cultural burns.” Should add reference to discuss this point because of no reference to cited and supported.

# Material and methods

In the statistical analysis part, please point out which R packages and functions you used.

# Results

“Conversely, clay content decreases from NB soils to ILB to ALB soils, with significant difference (P < 0.001) between each group; Figure 2C).” change “;” to “(”

“Water repellency is very variable in NB and ILB soils, with water drop penetration times (WDPT) ranging from 4 to 2050 seconds (s) for NB soils, and from 5 to 1618 s for ILB soils (Figure 2D).” “Water repellency” not show in the figure 2D. The figure 2D is log time. Please carefully check it.

“Soil organic matter is significantly higher for the sites that experienced either the agency-led or the Indigenous-led burns, compared to the “non-burnt” sites (Figure 3C).” Please maintain the same format because the previous sentence also uses abbreviations. Change 'agency-led' and 'Indigenous-led' to 'ALB' and 'NB.

“In combining data for all fire treatments, soil bulk density show a significant negative correlation with soil organic matter (r(99) = -0.70, P < 0.001). Similarly, C concentrations show a significant positive correlation with soil organic matter (r(72) = 0.59, P < 0.001), as do N concentrations to a lesser extent (r(72) = 0.47, P < 0.001).” There is no indication of which table and figure you cited. Please carefully check it.

In the results and discussion part, I suggest to add subtitles. 

Minor editing of English language required

Author Response

We would like to thank the Reviewer for their constructive comments.

There is very little literature on the effect of cultural burning on soil properties, all references that could be found are cited in the manuscript.

We have added symbols to indicate significance on all boxplots. We are unclear what the Reviewer means by ‘some result not show in any figures and tables’.

We are unable to add a reference illustrating that little is known about the effect of cultural burns on soil properties, exactly because there is so little to no literature on the topic.

R packages have been added to the manuscript. In addition, the script used for statistical analysis and figure drafting is available upon request.

“;” has been changed to “(”

Figure 2D shows the water penetration time, which is used to estimate water repellency.

We feel it is more appropriate to not use abbreviations here (“for the sites that experienced either the agency-led or the Indigenous-led burns, compared to the “non-burnt” sites”) as this would be awkward otherwise (“for the sites that experienced either the AL or the ILBs, compared to the NB sites”).

Figure citations have been added, where relevant.

We would prefer to not add subheadings to the Results and Discussion, as there would be very short sub-sections otherwise.