Effects of Wildland Fuel Composition on Fire Intensity

Round 1

Reviewer 1 Report

This study evaluated flammability differences between oak and maple litter. It used laboratory assessments to quantify flammability parameters under controlled conditions and found that oak litter was associated with higher flame temperature and longer combustion time. The authors concluded that shifts in species composition would affect the flammability of mixed-oak forests, leading to less intense fires. The study is interesting, and the results are potentially useful to better understand and manage mixed-oak forests. However, I found some issues that will need to be addressed before I can recommend this manuscript for publication.

The authors seem to use the terms ‘heat’ and ‘temperature’ interchangeably, but those represent two fundamentally different concepts. Heat is not measured in °C. What the authors measured here is temperature. Please remove the terms ‘heat’ and ‘heat of combustion’ from Methods, Results, and Discussion when talking about the results of this study (i.e., not general literature).

I find the first aim listed at the end of the Introduction (LINE 72) misleading. The authors hypothesize that “maple will have lower fuel flammability than oak due to the differences in the chemical and physical properties of litter”. Yet, no chemical nor physical leaf properties are quantitatively examined in this study. I recommend removing this aim and focus on the other two.

The Methods describe data collection in 94 sites, but only 30 samples were processed. Does that mean that leaves of the target species were manually pulled out from the litter samples, put together regardless of prevenance, and subsequently separated in samples of equal weight? If so, this should be explained in more detail. It would also be good to show in Fig. 1 which sites contained oak litter and which maple litter (unless all 94 sites contained both, in that case this should be stated). Also, was water content recorded for maple and oak leaves, or were they separated after drying the litter samples? If data on water content is available, it would be good to report it.

The ‘Fuel collection’ section lists a series of parameters (e.g., grasses, twigs, dead wood debris) collected in the field for which Results are never presented. Remove that part if not relevant to this study.

Fuel depth is reported to be approx. 10cm. Is this value purely due to laboratory logistics, or does it represent typical fuel depth in oak forests?

In the Results, some flammability parameters (e.g., T at 0cm) were reported to be significantly different between maple and oak. Please report the p value of these contrasts.

In the Discussion, results reported as significant (e.g., T at 0cm) are lumped together with non-significant contrasts (e.g., T at 10cm) and given the same weight (LINE 245). Additionally, while the Results do show that correlations at 0.40 and 0.45 are significant (although only at a 0.05 level), it seems a stretch to describe them as strong correlations (LINE 247).

LINES 237-240. I would move this description to the Methods.

The authors argue that the temperature at 10cm represents greater heat radiation and, as such, oak litter has greater potential to pre-heat unburnt fuel compared with maple (LINES 253-256). Yet, in this study temperature at 10cm was not significantly different between oak and maple. Please remove this statement.

Leaf curling is discussed as potential explanation for the minor differences in flame height. Yet, both litter depth and weight are reported to be similar for all samples (10 cm and 20 g, respectively). Without quantitative data to support these statements, I would limit the inference on the effect of leaf characteristics on flame height, as the results of this study show very minimal, non-significant differences between maple and oak.

LINE 320. Change ‘revealed’ to ‘suggests’.

Figures are clear and easy to read. Please include figure lettering (e.g., Fig. 4A) when referring to them in text.

Overall, the manuscript is well written, but please fix some minor grammar issues throughout. Additionally, avoid copying and pasting exactly the same sentence in the Abstract (LINES 6-7) and Introduction (LINES 25-27).

Author Response

Please check the attachment. 

 

Author Response File: Author Response.pdf

Reviewer 2 Report

I applaud the authors for putting together an excellent paper in an area of importance in eastern US forests.

I have just a few comments.  They will be referenced by the line number of the manuscript.

Line 52 - does there need to be a reference number after McDaniel?

Figure 1 - is a figure of the study area critical to the manuscript?  It's interesting to see the plot layout, but the figure provides very little information.

Table 1 - is it needed?  Is defination correct?

Is Figure 4 needed, given the information in Table 2?

What is the difference between Figure 2 and Figure 6? 

Lins 283-288 - is the discussion of nutrients and erosion transport critical?  This was not the focus of the study.

There are some inconsistencies in the Reference section.

 

 

 

 

 

Author Response

Please check the attachment. 

 

Author Response File: Author Response.pdf

Reviewer 3 Report

The paper studied the effects of wildland fuel composition on fire intensity. In total, it is just like a experiment report, lacking enough deep analysis. My comments are as follows:

1. If fire intensity is studied, then heat release rate is a key paramerter to be added.

2. if wildland fuel composition is paid attention, then these component, such as leaf litter, grasses, twigs, dead wood debris, bark debris, should be further statistic in detail.

3. What's the relationship between composition between fire intensity? Deep quantitative analysis is needed.

Author Response

Please check the attachment. 

 

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

I am happy with the revisions made by the authors and recommend the manuscript for publication in its current form.

Reviewer 3 Report

Accept