I'm Dr. Monica Rother. My research focuses on fire ecology and fire history from tree rings. Ask me anything!

I am a student at NCSU taking FOR531. Since you mentioned forest recovery after burns, are you finding that forests recover quicker or slower than they used to with today's ongoing climate change issue?

Great question! Yes, there is some evidence that forests are recovering more slowly (or not at all) after fire. We see a lot of this research coming out of the western U.S. For example, for my dissertation work, my colleagues and I documented very limited tree regeneration after wildfires in ponderosa pine woodlands in the Colorado Front Range. I’ve also been involved in several larger studies (meta-analyses) that combine data from different areas to show that this problem isn’t isolated and is a major one across many western landscapes. This research has successfully shown that changes in climate are at least partly to blame - hotter, drier conditions after fire can make it much harder for tree seedlings to germinate and survive. Changes in fire severity (also related to climate change) can also create challenges for forest recovery. For example, ponderosa pine only disperses its seeds short distances, so if a large, severe fire kills all the mature pines in an area, recovery can be very slow.

I am Vanadeep Kaluvagunta, who is taking the Wildland Fire Science (FOR 531) at NC State University this spring 2023 semester. I lived in Los Angeles from 2019 to 2021. I always was puzzled about the unabated frequent occurrence of bush fires every year despite having the best firefighters and meticulous mechanisms in place. Is it only due to the prevalent dry conditions (Santa Ana winds, etc.) or they are deliberately ignited by miscreants?

Thanks for the question! Fire in California is very different from fire in the Southeastern U.S. (where I am based). It’s a combination of many factors that makes the wildfire situation so challenging out there. First, the climate (including the winds but also the hot, dry summers) is very conducive to fire. Second, the topography is complex and the mountainous landscapes also create a more challenging situation for controlling fire. And yes, human ignitions are a huge problem in California and across the globe - not just by ‘miscreants’ but also through accidental ignition related to vehicles, power lines, and other issues. Another thought is that we also have a ‘fire deficit’ in many landscapes - fires have been suppressed for decades or longer in many areas which creates a more flammable situation that is more vulnerable to burning at higher intensity. Finally, it’s also important to remember that fires are indeed natural in many Californian landscapes - so just because it’s a wildfire that may create challenges/hazards for people doesn’t mean it is totally unnatural and isn’t providing any ecological benefits.

Hi,

I am Amir, a PhD student whose research is focused on wildfires air quality impacts (I have started the research 2 weeks ago :D)

From the history of past fires, and comparing them to current status, is it possible to say that things are getting worse? (wildfire related)

That’s exciting that you have initiated a PhD on wildfire! Congrats! This is a tough question because it just depends on where you look! In longleaf pine ecosystems of the Southeast, for example, our tree-ring records show us that we need more fire on the landscape. We need to continue our prescribed burning and increase it in many areas. There are some locations where fire activity has changed in recent years, related to climate change and the history of fire exclusion (including fire suppression). In some places, fires are happening more frequently than historically, based on comparisons to the tree rings and other proxy records.

I had only planned to answer questions until 1:00PM ET but it's been so fun answering all of your great questions that I had to keep going! It is actually time to hop off of here for now, though. I might have time later to return to some questions that I missed.

Thank you to everyone that joined today, and for all your great questions about fire ecology, dendrochronology, and wildland fire! If this has sparked your curiosity, and you have more questions, visit my website, (https://sites.google.com/view/monicarother/home), the Southern Fire Exchange (https://southernfireexchange.org), or any of the Joint Fire Science Program supported nationwide Fire Science Exchange Networks (https://www.firescience.gov/JFSP\_exchanges.cfm).

Hi, I'm a USFS firefighter in the NWCG Rx-310 class right now, and as part of it, we have to send a scientist who has been involved in fire some interview questions to answer. Do you mind if I email you these questions?

Sure! You can get my email address from my website here: https://sites.google.com/view/monicarother/home

Hello professor! What was the most challenging real-time fire situation that you have faced? How did you mitigate that using your expertise in the subject?

I have a lot of experience with prescribed fire but no experience fighting wildfires! Of course the wildfire environment tends to be much more challenging and unpredictable. Fortunately for me, I haven’t experienced anything too sketchy/terrifying in my experience with prescribed fire. I have experienced spotting (on many burns!) where a bit of fire goes outside the boundaries of the prescribed fire. This is a bit nerve wracking but we are always prepared with water and tools (shovels, rakes, etc.) to put out these fires before they get out of hand. I have found that good communication and keeping calm are the two most important things to managing challenging situations like these - talk to the team, make a plan, and keep your head calm and collected! And make sure to be ready for changes in the weather/fire conditions!

Tell me about this study(I mean what did you actually learnt and what they teaches under this title) Does this subject related to global warming? How can I study this subject(if I wish sometime)

Tell me about this study(I mean what did you actually learnt and what they teaches under this title) Does this subject related to global warming? How can I study this subject(if I wish sometime)

We learn a lot from studying fire scars in tree rings. We are able to figure out the exact years and even season of past fires, going back through time. For example, in the Piedmont of North Carolina, we recently found that fires occurred every few years over previous centuries by studying the fire scars. If you’re interested in learning more, there are a lot of great general resources!

A great introductory text to tree-ring science is:

Speer, J. H. (2010). Fundamentals of tree-ring research. University of Arizona Press.

An excellent overview article that discusses using tree rings for fire history is available here (Falk et al., 2011 - Multi-scale controls of historical forest-fire regimes: new insights from fire-scar networks):

https://www.fs.usda.gov/research/treesearch/39310

Here’s another article on next steps for tree-ring based research on fire (Harley et al., 2018 - Advancing Dendrochronological Studies of Fire in the United States):

https://www.mdpi.com/2571-6255/1/1/11

A few nice online articles/resources include:

https://scied.ucar.edu/learning-zone/how-climate-works/tree-rings-and-climate

https://www.nytimes.com/2019/04/30/science/tree-rings-climate.html

https://ltrr.arizona.edu/about/treerings

Yes, it can be related to global warming. We can study the relationship between fire and climate in the past and then make some inferences about what might happen in the future. In some places, changing climate means that fires are more intense or larger.

Do forests that are more diverse in plant species regenerate from fire better than monoculture forests e.g. plantations?

Good question! As you are hinting to, a monoculture forest like a plantation isn’t going to have as much biodiversity in the understory as a more natural forest. In terms of how rapidly the ecosystem recovers following fire, it will depend on the species that were present within and adjacent to the site prior to the fire. If it’s longleaf pine tree, they will probably survive the fire. However, in more natural ecosystems, the longleaf would survive and the many understory plants (grasses, forbs, woody plants) would also survive and resprout after the burn. In pine plantations, site preparation treatments are often used to minimize vegetative that can compete with pines. These treatments tend to reduce understory diversity and cover (that’s kind of the point). Similarly, densely planted pine plantations tend to have little understory diversity due to a lack of sunlight available at the forest floor.

What's the oldest fire you have identified?

In terms of published studies, the oldest fires I have found so far are in the 1600s. However, we have work underway in Florida that shows fire activity in the 1500s! We are limited by how long the trees live. However, if we collect a very old stump that was cut down over a 100 years ago, we can get back further in time. In some places, with longer-lived tree species, fire history can go back beyond a millenia!

But does it mean that you should cut those old trees down to see the rings and check for fire marks?

In my own research, I do not sample live trees for fire history. Because fire scars can occur on any side of a tree, we generally need a full cross section (sometimes called a tree cookie) for the fire-history work. We focus on collecting these cross sections from snags (standing dead trees) and stumps. There is a tree-ring method of sampling live trees without them - a pencil thin core is extracted using a tool known as an increment borer. However, this method is not useful for fire history; it’s used in studies that examine things like tree age and climate-growth relationships. You can check out cool photographs of working with stumps and live trees on my research website:

https://sites.google.com/view/monicarother/photo-gallery

Since many tree species rely on fire for germination or to clear out competitors and encourage growth, do any of the pyrophytic plants express traits that encourage fire?

Yes! Many plants that have evolved with fire have traits that make them more flammable! For example, the long needles of longleaf pine are very flammable - their chemistry makes them more likely to ignite and burn. And the way they land on the understory creates a nice continuous layer of fuel that also allows oxygen to get in (a needed ingredient of fire). There are also fire-loving oaks that have flammability traits that encourage fire. The Mutch Hypothesis captures a lot of these ideas. We are still learning about the many fire traits that plants can have but we definitely see that our fire loving plants tend to encourage fire!

How do you study fire history from tree rings?

Tree-ring science (also called dendrochronology) is very useful for studying the fire history of a given area. The tree rings contain evidence of past fires in the form of fire scars. These fire scars form when the heat of a fire moves past the base of the tree and causes a small injury, but doesn’t kill the tree. Fire scars can be dated using tree-ring methods to find out the exact year and approximate season of past fires that occurred at the site over the life of the tree. An essential part of the research includes crossdating - a process of pattern matching that ensures that each tree ring is dated to its exact year of formation. In longleaf pine, we are finding fire-scar evidence that proves fires occurred historically every 1-4 years.

What has your research revealed in terms of the differences between natural fire regimes and modern prescribed fire regimes? Are fire practitioners burning enough and at the right time of year?

This question depends on where you look, but in many places, we aren’t yet getting enough fire on the ground! For example, fire history studies in longleaf pine across the Southeast are showing that fires occurred every 1-4 years. Although prescribed burn practitioners are burning at that frequency in some places, many other areas remain unburned, some for decades or longer! The fire scar information is generally telling us we need to grow our prescribed fire programs!

The seasonality piece is a hard one to answer. In some places, we see in the fire-scar record a lot of dormant season fires that were ignited by people. However, in other locations, we see a strong record of lightning fire. These fires tended to happen in early spring and summer. I generally think prescribed burn practitioners should aim to increase their growing season burning. However, I do understand that managers face many challenges to doing so and it’s definitely key that we get frequent fire on the ground, even if that means burning at times of year that are inconsistent with the lightning fire regime. So in short - more growing season fire but also keep up with the other burns!

There are many adverse health/climatic effects from prescribed burnings, isn't there any other way to do what fire does to the forests, without actually having to burn them?

Prescribed burning is extremely beneficial and there is no perfect replacement. The ecosystems we burn with prescribed fire evolved with fire and require frequent fire to maintain healthy conditions. Additionally, the prescribed fires can actually help protect people! First, the prescribed fires reduce fuels (living and dead plants) and decrease the likelihood of a much more dangerous, unplanned wildfire. Second, less smoke is produced by a prescribed fire than a wildfire and this smoke can be managed through strategic burning to minimize smoke to sensitive areas like surrounding communities. Alternatives to burning (like mowing down vegetation or using herbivores) can be beneficial in certain areas where prescribed fires aren’t feasible, but they do not perform the exact same roles as fire performs on the landscape.

Can you tell me why Targaryens dont burn in fire??

Daenerys Targaryen and her family members, much like the iconic longleaf pine of the Southeast and the ponderosa pine of the western US, likely have a thick outer bark that insulates them from low-intensity fires.

Can you fake tree rings?

I’m not sure about faking tree rings, but there have been studies that have intentionally created fire scars (damaged tree tissue caused by fire). These studies have looked to understand the mechanisms and conditions under which fire scars can be formed and thus under what circumstances trees record the occurrences of fire on the landscape.

Can you determine differences between historic wildfires and indigenous cultural burning in any way?

That’s a great question! With the understanding that in many places there is a fire deficit on the landscape, there is quite a bit of interest right now in cultural burning across the US / globe. Tree rings and fire scars don’t specifically provide information about how the fires were started, but inferences can be made in some cases. My work into understanding the seasonal aspects of fire scars can help to provide clues about the origins of fires. When we see fire scars that indicate the tree scarring occurred outside of typical wildfire season(s), we can often make assumptions that those fires were anthropogenic in origin. We consider burning by indigenous people to be an important part of the historical fire regime in many locations.

Generally, how many trees are needed to have a useful sample to conduct meaningful research in this area?

Yes, we do have some general rules in terms of the number of trees needed for a fire history study using tree rings. For each site, we tend to want at least 10-15 trees. However, there is some wiggle room there since it depends on whether the trees we sample have picked up on a lot of fire activity or not. Some trees are better than others at documenting the fires that occur around their bases. In some studies, I’ve seen 20-40 trees included per site.

How do wildfires influence soil quality in forests? What are the vital nutrients lost? What are the techniques you follow to rejuvenate them and approximately, how long does it take for the soils to bounce back on an average, especially after ground fires and surface fires?

Great question! As with many questions in ecology, it depends. The impact of fires on ecosystem soils tend to depend on the amount of soil heating that occurs, the amount and duration of vegetative cover lost, and the post-fire events that follow. Soils tend to be remarkably good insulators, and in many cases, elevated temperatures due to fire may only go a few inches underground. Because of that, low intensity fires often have minimal impacts on soils. On the other hand, high intensity fires or fires with heavy fuels concentrated on the surface and with long residence times, can have more significant impacts to the soils. In some cases directly volatilizing soil organic matter and soil nitrogen. As we see in more arid places in the western US, post-fire erosion can be a huge issue due to pre-fire heavy fuel loads and post-burn soil exposure due to delayed vegetative response. In the southeastern US, ecosystem vegetation can respond within days of a fire, protecting the soils from erosion. In more arid places, vegetation may not recover for months, leaving the soils exposed to erosion.

How much regional variation do you see if frequency / intensity of historic fire in different locations (e.g. Southeastern US, Rocky Mountains, California, etc) Would you be able to use this research to tailor prescribed fire recommendations to reduce risk and maximize beneficial effects of future prescribed fire programs?

We see a lot of variation in historical fire regimes in terms of the fire frequency and intensity. In some places, the fire history might show a fire frequency of every 1-5 years. In other landscapes, the natural fire regime might show fires occurring every 10-20 years. Longleaf pine ecosystems have the highest natural fire frequency. An important thing to remember with the fire scar research is that we can only use fire scars when fires are relatively low in intensity and the trees survive. Some forests in North America are meant to only burn at high severity very rarely (e.g., every century), but it’s much harder to use fire scars in these systems; only around the fire edges where some trees might have survived. If you’re interested in fire frequency in the US, check out the PC2FM model of predicted potential natural fire return intervals based on physical chemistry factors alone (https://oakfirescience.com/research-brief/predicting-fire-frequency-with-chemistry-and-climate/). It’s a fascinating model that uses only physical factors to predict how much fire our landscapes might sustain. This model doesn't even include anthropogenic ignitions, which we know are and have been truly significant in many landscapes!

Outside of the policy / attitudes towards the effective use of prescribed burning and forest management, what are biggest limitations to prescribing burning happening at scale in the US?

Good question! There are many people who are trying to understand how to significantly increase the pace and scale of prescribed burning in the US. The National Association of State Foresters publishes a regularly updated report on the use of prescribed fire across the US. In the 2021 report that was just recently published (https://www.stateforesters.org/wp-content/uploads/2023/01/2021-National-Rx-Fire-Use-Report\_FINAL.pdf) they identified nine impediments to the use of prescribed fire: capacity, weather, air quality / smoke management, resource/funding, public perceptions, liability/insurance, permitting/legal concerns, WUI/population growth and agency/landowner priorities. The report provides a bit more information about each of these categories, but it’s likely that limitations vary by region and locality.

Do you know of any new proactive methods that could prevent wildfires during the summer months?

Back burning has been helpful, but I think hydro gels (flame retardant) will be needed as a proactive method rather than reactive.

I was in Canberra during the 2020 bushfires and witnessed how modern firefighting methods are not viable against the types of fires we now have. Especially against a pyrocumulonimbus storm. These are becoming more frequent as our climate changes.

That’s a good question and I’m sorry you had to experience the 2020 fires in Canberra. I hope you and your family are ok. I’m not a wildland firefighter, but I’m aware that the truly catastrophic fires that some areas have experienced in recent years have outpaced fire management organizations and capacity. Unfortunately, studies and models suggest that with a continually warming climate and decades of successful fire suppression in many areas, wildfires will continue to threaten many communities. Prescribed fire, mechanical fuel reduction, and limiting flammable vegetation close to buildings in wildland urban interface areas can help reduce the frequency and intensity of wildfires.

Other efforts to increase community and homeowner resilience are going to be important. Research has shown that in many cases structures ignite from wind blown embers. There are many resources that provide recommendations for home hardening, another activity that can help reduce the impact of risks like that: https://wildfirerisk.org/reduce-risk/home-hardening/

I am an NCSU student in FOR 531. What is the most interesting/ unexpected data you have found from tree rings?

I'll copy my response from a similar question that was asked below!

Great question! I think a recent study that I completed with colleagues in the Red Hills Region of Florida and Georgia was especially fascinating. Most tree-ring based fire history studies show almost no fire activity in the 1900s and later. This is because of the “Smokey Bear Effect” - people stopped allowing fires to burn in the U.S. through direct fire suppression. There were also changes in fuels related to development (e.g., roads that disrupted fire spread) and cattle and sheep grazing that inhibited fire occurrence and spread in much of the U.S. What was interesting about the Red Hills study is that we found TONS of fire activity through the 1900s and up to the present day. The Red Hills have long been known as a region where the burning never stopped, but we provided hard evidence of this claim through the fire scars.

Here’s a link to that publication:

https://www.sciencedirect.com/science/article/pii/S0378112720311750

What would you consider the coolest piece of fire history you found out from tree rings?

(from the Southern Fire Exchange LinkedIn page)

Great question! I think a recent study that I completed with colleagues in the Red Hills Region of Florida and Georgia was especially fascinating. Most tree-ring based fire history studies show almost no fire activity in the 1900s and later. This is because of the “Smokey Bear Effect” - people stopped allowing fires to burn in the U.S. through direct fire suppression. There were also changes in fuels related to development (e.g., roads that disrupted fire spread) and cattle and sheep grazing that inhibited fire occurrence and spread in much of the U.S. What was interesting about the Red Hills study is that we found TONS of fire activity through the 1900s and up to the present day. The Red Hills have long been known as a region where the burning never stopped, but we provided hard evidence of this claim through the fire scars.

Here’s a link to that publication:

https://www.sciencedirect.com/science/article/pii/S0378112720311750

I’m interested in getting a PhD in fire ecology. Are there any potential researchers/mentors in this field whose work you’d recommend checking out? Thank you!

Absolutely! There are so many so I can’t be comprehensive in my answer, but here are some suggestions of researchers who work with PhD students!

• Rae Crandall, University of Florida
• Grant Harley, University of Idaho
• Scott Stephens, University of California Berkeley
• Don Falk, University of Arizona
• Rosemary Sherriff, Humboldt
• Max Moritz, UCSB
• Heather Alexander, Auburn University
• Mike Chamberlain, University of Georgia
• Marcus Lashley, University of Florida
• Mike Stambaugh, University of Missouri

I am a graduate student at NCSU pursuing a Master of Forestry. I am wondering if there is a systematic way of assessing fire severity following a wildfire event? For a project last semester I used FIA data to compare pre- and post-fire conditions, but this is only possible in areas that have already been sampled.

Good question! Fire severity is a great way of attempting to quantify the variable impacts of fire. From a remote sensing perspective (typically satellite), there are multiple techniques that have been developed to identify and map patterns of post-fire burn severity. Many of these techniques use multispectral satellite sensors. The normalized burn ratio (NBR) and its variations (dNBR) come to mind. There is even a national (US) archive of burn severity maps available for free online from the Monitoring Trends in Burn Severity (MTBS) project led by the USGS (https://www.mtbs.gov/). For assessing burn severity from the ground, you might consider looking into a technique called the Composite Burn Index (CBI). Link for more info here: https://burnseverity.cr.usgs.gov/products/cbi.

What's the earliest forest fire we have on record?

From the fire-scar perspective, the earliest evidence dates back over 200 million years ago! Check out this article about a fossilized chunk of wood with an obvious fire scar!

https://www.livescience.com/47316-oldest-forest-fire-scar-fossil.html

Which species of tree(s) do you use to conduct your research on fire ecology and tree ring research?
(from the Southern Fire Exchange LinkedIn page)

So far in my research, I have focused on two different pine species. First, in the Southeast, I have worked with longleaf pine (Pinus palustris). This species used to be widely distributed across the North American Coastal Plain, from eastern Texas up to southeastern Virginia. Longleaf pine and its associated ecosystems are fire maintained - they need very frequent fire (about every 1-4 years) to stay healthy! In the West, I have worked with ponderosa pine (Pinus ponderosa). Like longleaf, ponderosa is known to require frequent fire to maintain healthy forest composition and structure. I’m in love with these two fire-adapted pines!

Are there hardwood species in the south that are fire tolerant and live long enough to be useful in dendrochronology?

There are many hardwood species in the South that could be considered fire tolerant. Some of them are considered pyrophytic, meaning that they have flammable characteristics (flammable leaf litter) and adaptive strategies for protection or recovery from fire (thick bark, ability to resprout). There are some fire-scar studies in oaks! Mike Stambaugh comes to mind as one researcher who has done some fire-scar work in oaks - see: https://treerings.missouri.edu/publications/ That said, some oaks have challenging tree rings to work with or do not scar as frequently as some of the pines we use for this research.

Another tree-ring researcher here! Glad to see colleages over there. Where/what is the ecosystem or biome and region in which you found the highest fire recurrence??

The longleaf pine ecosystem, for sure! In North America, it is known to have the highest natural fire frequency. This is supported by the fire-scar record along with other lines of evidence like its high lightning activity and flammable vegetation type. Ponderosa pine also comes to mind, although fires in that ecosystem type weren’t quite as frequent and varied a lot with elevation.

Who is your funding source currently and how does your pathway to independence grant process work? I come from a molecular biology background and my K99/R00 was through the NIH

I am currently funded by various sources including the National Science Foundation and the North Carolina Collaboratory. I also sometimes go for small, internal awards (through my university) that support research. Additionally, I sometimes work with land management agencies to make agreements/contracts for work.

I’m not sure I understand your question in terms of what you mean by a pathway to independence…can you explain more?