The Effect of Fire on Multiple Tree Species in the Eastern Deciduous Forest

Round 1

Reviewer 1 Report

The article is interesting, but in my opinion it requires a more detailed discussion and reference to other research. My comments and suggestions are described in the comments of the PDF document.

Comments for author File: Comments.pdf

Author Response

Reviewer 1

The article is interesting, but in my opinion it requires a more detailed discussion and reference to other research. My comments and suggestions are described in the comments of the PDF document.

We made the editorial corrections that were suggested in the pdf.

Line 208: Comment on the fire history data from the refuge.

We used the official Big Oaks National Wildlife Refuge fire prescription records and checked those against historical maps of the fires that were drawn by Jefferson Proving Grounds.

What year was this map?

This was the sector map given to us in 2006 when we started this research and was used to organize our sampling throughout this work.

What databases were used to verify fires? Were fire brigade bases used? Comparing the databases would allow you to verify the laboratory results and determine whether each fire was recorded on a tree trunk. Perhaps some fires were not recorded by the emergency services. Perhaps it would be possible to check databases from the last 20 years.

We collected fire burn maps and spreadsheets from the Big Oaks National Wildlife Refuge and they also provided information from some hand-drawn fire perimeter maps from the Army when the property was the Jefferson Proving Grounds. These records went back to 1997 from the US Fish and Wildlife Service Fire Management Information System.

We Included the following sentence in the methods “We used US Fish and Wildlife Service databases of fire events that extended back to 1997 to select sites and compare known fires to our fire scar events. The fires ranged from 9 – 1,014 ha (24 – 2508 acres).”.

In material in not information about the characteristics of the fires. Were they large fires? Is anything known about their surfaces? Such information, especially about the latest fires, should be available in the databases of the administration managing the areas or in the fire brigade database, if it took part in extinguishing the fires?

The fires ranged from 24-2508 acres and we included this information in the previous comment and edit to our methods.

Perhaps at this point we should refer to other studies that examined the survival of tree species after fires? Controlled fires were carried out in California. Wasn't the plant survival tested after these activities? Have similar analyzes related to plant survival after fires been performed in other countries?

I wanted to keep the review of resprouting after fire to the genera in the Eastern Deciduous Forest because plant response to fire is very species and genera specific. I was able to find a few references that talk about resprouting of these hardwood genera, but most of the focus on fire adaptation is on Pinus and Quercus. The ability of the many other species to survive and resprout after fire is an important question and more work needs to be done in this area. I included this paragraph in the discussion.

“Nuttle et al. [29] found that fire on its own on study sites in West Virginia did not increase tree diversity or density but did change these parameters when combined with gaps and deer browse. Fire combined with deer browsing caused the greatest increase in relative abundance in maple trees [29]. Arthur et al. [30] report that many of the hardwood genera resprout after fire including Acer, Carya, Castanea, Cornus, Fagus, Liquidambar, Liriodendron, Nyssa, and Ulmus. Matlack [31] argues that fire studies have over-reported the occurrence of fire in the eastern United States because of targeted sampling, although our work support’s Arthur et al.’s [30] findings that most of the hardwood genera that we sampled resprouted after fires.”

It is also worth considering whether if trees survive after a fire, what impact does it have on their physiology and health?

We included the following sentence in the discussion.

“We found similar induced responses in all of the hardwood species that Smith and Sutherland ^[15] found in their research, suggesting that these genera can survive fires, protect themselves from fungus that enters the tree, and can thrive under these conditions.”

Also, we included the following sentence in the conclusions.

“Many of the genera that we sampled (Fagus, Liriodendron, and Liquidambar) were scared more than 100 years ago and were surviving at the time of sampling, suggesting that these trees can be injured by fire and still live long lives.”

Were solutions other than a controlled fire considered? Cutting trees, mowing vegetation - these are activities that, depending on legal requirements, can be carried out at other times of the year. Such solutions are carried out in protected areas in different countries.

These techniques are also being used at the Big Oaks National Wildlife Refuge and we included the following sentence to note this.

“Cutting of individual trees was also being used to remove regeneration and maintain open grasslands on the property in some cases.”

In the discussion, I propose to point out examples of protected areas where controlled fires help protect habitats.

I provided a short review of protected areas in the eastern United States that were using controlled fire and a short review of the literature related to fire history in the eastern US and its management implications.

“Many national public lands have fire management plans and use prescribed fire to maintain habitats and enhance plant diversity such as the following: Great Smoky Mountains National Park, Shawnee National Forest, Congaree National Park, Cuyahoga Valley National Park, and the Hoosier National Forest. Fire has been demonstrated as a useful tool in the Eastern Deciduous Forest that helps to maintain some forest types. Lafon et al. [33] demonstrate through dendropyrochronology that fire occurred every few years on many landscapes of the central Appalachians prior to the fire-exclusion period and that vegetation is currently adjusting to this period of lower fire occurrence.”

Reviewer 2 Report

This study examines the fidelity of fire scaring in multiple tree species. Fire history is reconstructed by tree scars. Some questions need to be answered:

1. What’s the purpose of this work? Or what’s the application of this work?

2. The differentiation criteria for fire scar and injury (Page 4 Line 141) are suggested to be given clearly.

3. How to determine the fire burning season in the past according to the position of the scar within the annual ring? (Page 5)

4. How to determine the time of a fire based on fire scar and injury? (Fig. 3)

5. Various trees were introduced in the paper. So, the fire history is determined by one or several of them?

Author Response

Reviewer 2

This study examines the fidelity of fire scaring in multiple tree species. Fire history is reconstructed by tree scars. Some questions need to be answered:

1. What’s the purpose of this work? Or what’s the application of this work?

In the abstract, we state “This study examines the fidelity of fire scaring in multiple tree species in the Big Oaks National Wildlife Refuge in Indiana located in the Central Hardwood Region of the Eastern Deciduous Forest.”

We have included a few sentences in the introduction to clearly state our purpose and applications. “In this paper, we strive to demonstrate the ability to record fire of a large variety of hardwood trees species. It is important for future management efforts to understand how these species deal with fire and how they record fire and survive fires in these forests.”

2. The differentiation criteria for fire scar and injury (Page 4 Line 141) are suggested to be given clearly.

We describe the difference between a fire scare and an injury the following way. We have not found any better way to describe the difference and these are the criteria that we followed to describe them differently would not properly represent the work that was done.

“Scars were assigned as being fire scars rather than injuries based on the following criteria: the scar results from cambial mortality rather than mechanical damage that may remove rings before the scar formed, the event caused enough damage for wound wood to form after the injury, and the injury may be repeated around the circumference of the cross section. If these criteria were not clear (with the third criteria of repetition around the circumference not being mandatory) then the wound was identified as an injury.”

Fire scars result from the outside of the tree being heated to a high enough temperature that it causes cambial death. This is differentiated from an abrasion effect of a tree falling against another tree or an animal chewing or rubbing against the bark and causing an injury through abrasion. With low-intensity fires and thick bark trees, the trees can take on multiple small scars in the same year where the fissures in the bark resulted in thinner bark and therefore more cambial damage. This results in multiple scars occurring around the circumference of the tree in the same year which is not likely to happen through other sources of injury.

2. How to determine the fire burning season in the past according to the position of the scar within the annual ring? (Page 5)

I included the following sentence.

Fire scars were assigned to a season based on the portion of the ring that had been produced at the time of the fire.

This is the longer description that was used to describe the specific location of the fire scar that related to the season of fire.

“Leaf-out occurs in April, and early earlywood scars occur in early spring (approximately from May to early June); middle earlywood scars are likely to occur in June; late earlywood scars occur in July; and latewood scars occur in August. The growing season for each species varies widely, and even individual tree species vary in their growing season from year to year making these broad estimates at best for the timing of fire seasonality. Dormant season fires occur when the trees are not actively depositing secondary growth on the stem from the end of the growing season in autumn until the beginning of the growing season the following spring. Because the main prescribed fire season in this area is March and April, we are assigning dormant season fires to this time period (it is possible that dormant season fires in the past could have occurred in October to November as well, but we did not see any evidence of that). Undetermined scars are ones where the season could not be determined because of rotten wood or damage from wood-boring insects.”

3. How to determine the time of a fire based on fire scar and injury? (Fig. 3)

The date of the fire scar or injury is based on cross dating the rings which is the basis for dendrochronology and this paper.

This sentence is from the methods that describes how we dated the scars.

“We used skeleton plots, a visual dating technique, to date each individual sample and built master chronologies for each species on the site [21,22]. These master chronologies were then used to help date other samples in that same species from subsequent sites. After the samples were dated, the fire scar and injury dates were noted for each sample, and the scars were photographed.”

5. Various trees were introduced in the paper. So, the fire history is determined by one or several of them?

The fire history (as shown in Figure 3) is a culmination of all of the fire scar dates from the Big Oaks National Wildlife Refuge and includes fire scar dates from all 14 species of the 15 that we sampled (only one species did not show any fire scars). So all species of trees are represented and they are stated in Figure 3.

Reviewer 3 Report

The version of the manuscript that I received contained a number of comments in the margins, perhaps made by previous reviewers? Although distracting, this is not a big problem but am I working from the proper draft? Well, I’ll go with it.

The manuscript makes a good case that eastern deciduous trees that are not regarded as especially fire-tolerant still may record fire occurrence in a dateable tree-ring record. If the above is a primary finding, it should be stated simply and clearly. I don’t think I see that in the text.

I see no reference to fire intensity or severity here. I should think that many of these incidents in Indiana are due to low-intensity surface fires. Is that true? I ask because at some level of low intensity, fire exposure would injure thin-barked red maple and produce a fire scar yet not even be recorded in the tree-rings of thick-barked individual oak. Is that true? My concern is that the scale of severity is likely quite different than for the better-studied western and southern conifer species.

I believe that the manuscript could be shortened and “readability” improved by adopting more simple language. I identify a few of the many opportunities for such improvement in line comments, below.

The grammar is correct, although the choices of usage are at times odd. I've noted a few examples in my line comments.

Author Response

Reviewer 3

The version of the manuscript that I received contained a number of comments in the margins, perhaps made by previous reviewers? Although distracting, this is not a big problem but am I working from the proper draft? Well, I’ll go with it.

The manuscript makes a good case that eastern deciduous trees that are not regarded as especially fire-tolerant still may record fire occurrence in a dateable tree-ring record. If the above is a primary finding, it should be stated simply and clearly. I don’t think I see that in the text.

This is the final sentence of the abstract. “Fourteen of the 15 species that we sampled preserved fire scars suggesting that the diverse suite of species in the Eastern Deciduous forest is a viable sampling pool for examining fire history across this forest type.”

I see no reference to fire intensity or severity here. I should think that many of these incidents in Indiana are due to low-intensity surface fires. Is that true? I ask because at some level of low intensity, fire exposure would injure thin-barked red maple and produce a fire scar yet not even be recorded in the tree-rings of thick-barked individual oak. Is that true? My concern is that the scale of severity is likely quite different than for the better-studied western and southern conifer species.

Fire severity of intensity is classically difficult to assess with dendrochronology. We have a binary indicator (the presence of absence of a fire scar). Dendropyrochronology studies tend not to discuss severity or intensity very much so that we don’t give the false impression that we are able to determine severity. You are correct that some of these species may record lower intensity fires than some of the fires in the west in pine forests, but either way, we can determine that the fire was ecologically effective because it left some indication of its passing.

I believe that the manuscript could be shortened and “readability” improved by adopting more simple language. I identify a few of the many opportunities for such improvement in line comments, below.

Round 2

Reviewer 1 Report

I think, that article in present form is interesting and important for description regions.