The making of a megafire: Study explores why some wildfires grow fast and furious

The making of a megafire: Study explores why some wildfires grow fast and furious

The making of a megafire: Study explores why some wildfires grow fast and furious

August 22, 2022
RENO, Nev.

Megafires
Fire Ecology
Fire Detection

Above: A view of the Las Conchas Fire, which burned more than 150,000 acres in New Mexico in 2011. The fire was among those analyzed as part of this study.

Photo courtesy of the National Interagency Fire Center.

Reposted from https://www.fs.usda.gov/pnw/news-releases/making-megafire-study-explores-why-some-wildfires-grow-fast-and-furious

Some wildfires grow much larger and a lot faster than others to become megafires. But why? As their name suggests, megafires are wildfires of extreme size with great destructive potential, which can make them especially challenging to manage. As megafires become more frequent in the Western United States, better wildfire prediction is needed to protect lives, property, and resources.

A recent study led by the USDA Forest Service’s Pacific Northwest Research Station explores why some fires turn into megafires by analyzing the effects of daily weather conditions. The findings can help fire managers anticipate which fires are likely to grow most rapidly and become megafires.

“Ours is the first study to systematically and quantitatively compare daily weather conditions with daily fire growth using multiple fires across the country,” said Brian Potter, research meteorologist at the station’s Pacific Wildland Fire Sciences Laboratory in Seattle, Wash. Along with Daniel McEvoy, researcher with the Desert Research Institute, Potter analyzed 40 fires that burned in California, the Great Basin, the Rockies, the Northwest, and the Southwest between 2002 and 2017.

The two researchers looked at a particular kind of megafire, which they called “fires of unusual size” or FOUS. These fires were 90,000 acres or larger and grew an additional 22,000 acres or more after at least one blowup, or growth, event. The scientists then compared these unusually large wildfires with smaller wildfires from the same general area. For each fire, they looked at the effects of prevailing dryness and daily weather conditions.

The scientists were surprised to find that the daily weather during these types of fires was, if anything, less extreme than during the smaller fires in their study sample. The FOUS tended to develop after two to four weeks of drier weather, which appears to prime them to grow much more when strong, dry winds occur.

More information:

  • The largest wildfires developed because they responded to one- or two-day, high-wind events and preceding dryness more strongly than the other wildfires.
  • It was how the wildfires responded to weather, not the weather itself, that appeared to differentiate the largest fires from other fires.
  • The study’s findings suggest that when the previous couple of weeks have been dry, fire managers may need to be more aware than usual of infrequent high-wind days, even when overall conditions are mild.

Potter, Brian E.; McEvoy, Daniel. 2021. Weather factors associated with extremely large fires and fire growth days. Earth Interactions. 25(1): 160-176.

Nevada Receives National Science Foundation Research Award for $20 Million

Nevada Receives National Science Foundation Research Award for $20 Million

drone in wildfire

May 17, 2022
LAS VEGAS

Fire Science
Wildland Fire Research
Workforce Development 

Nevada Receives National Science Foundation Research Award for $20 Million

To increase capacity for wildland fire research, education, and workforce development

The Nevada System of Higher Education (NSHE) has been awarded $20 million over a period of five years for the Harnessing the Data Revolution for Fire Science (HDRFS) project. This project is funded through the National Science Foundation Established Program to Stimulate Competitive Research (NSF EPSCoR); whose mission is to enhance research competitiveness of targeted jurisdictions (states, territories, commonwealth) by strengthening STEM capacity and capability. 

The overarching goal of the RII Track-1: Harnessing the Data Revolution for Fire Science (HDRFS) project is to increase the capacity of Nevada for wildland fire research, education, and workforce development and to demonstrate this increased capacity through technology-enhanced fire science in the regionally important sagebrush ecosystem. 

This system-wide partnership involves the three research institutions, the Desert Research Institute (DRI), the University of Nevada, Las Vegas (UNLV), and the University of Nevada, Reno (UNR). Further involvement includes faculty and students from NSHE undergraduate institutions.  

“NSF continues to serve as an essential partner in supporting the critical work of the NSHE EPSCoR,” said NSHE Board of Regents Chair Cathy McAdoo. “As our region currently faces extreme fire and water challenges, we appreciate this investment in Fire Science research and workforce development; giving NSHE institutions (DRI, UNLV, UNR) more capacity to solve our most pressing environmental issues.”  

This project will inform and improve land and fire management by providing scaling of fire effects and impacts from smaller to larger fires in four fire science areas: Ecology; Hydrology between fire events; Fire Processes; and Fire Emissions and their Atmospheric Aging during fire events. This will be achieved through strategic investments in expertise, facilities, Cyberinfrastructure Innovations, and Education and Workforce Development creating end-to-end pipelines for research and STEM advancements. 

“This project will generate and harness large amounts of data from diverse sensor platforms to accurately model landscapes and wildland fires from plot to watershed scales,” said Frederick Harris, Nevada NSF EPSCoR Project Director. “We will study how fires impact the societal needs outlined in the Nevada Science and Technology Plan.” 

In addition, NSHE researchers will study potential new areas of economic development for Nevada, emphasizing new opportunities for workforce development, diversity, hiring new faculty, and providing more scholarship opportunities for undergraduate and graduate students in STEM fields.  

“This NSF award funds critical fire science research, which continues to be a priority for Nevada,” said DRI President Kumud Acharya. “DRI has expertise in wildland fire research, and we look forward to working with our fellow NSHE institutions on this important project.” 

The award will enhance Nevada’s capabilities in wildland fire science, UAS, data acquisition, processing, and modeling, and rapid deployment, while strengthening Nevada’s network of external collaborators and stakeholders, who already include the major fire and land management agencies in the Great Basin and Western United States. 

“This marks an important investment for Nevada and the West,” said UNR President Brian Sandoval. “This National Science Foundation EPSCoR-supported project takes a comprehensive, collaborative approach. It will enhance the capacity of Nevada’s public research institutions to further tackle an issue of utmost importance and will do so by further deploying technology and cyberinfrastructure, and further building on the expertise and capabilities of our researchers and faculty.” 

“By joining forces, UNR, DRI, and UNLV are poised to reveal the power of cooperation in Nevada when it comes to addressing challenges important to the state and beyond its borders,” said UNLV President Keith Whitfield. “This research will advance our fundamental understanding of wildfires as it strengthens the capacity of our campuses to engage with each other and with Nevada’s students and citizens in addressing today’s complex challenges. This is but one example of how research works for Nevada.” 

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About NSHE

The Nevada System of Higher Education, comprised of two doctoral-granting research universities, a state college, four comprehensive community colleges, and one environmental research institute, serves the educational and job training needs of Nevada. NSHE provides educational opportunities to more than 100,000 students and is governed by the Nevada Board of Regents. The System includes the University of Nevada, Las Vegas, the University of Nevada, Reno, Nevada State College, Desert Research Institute, the College of Southern Nevada, Great Basin College, Truckee Meadows Community College, and Western Nevada College. For more information regarding NSHE please visit: https://nshe.nevada.edu/ 

About the Nevada System Sponsored Programs and EPSCoR

The mission of the Nevada System Sponsored Programs and EPSCoR is to promote collaboration and multidisciplinary learning among NSHE institutions, and to enable alignment of efforts with the needs of the state to increase research and STEM competitiveness. The goal is to create new opportunities in the State of Nevada for workforce development and promote the development of Science, Technology, Engineering and Mathematics (STEM) disciplines for the state. For more information regarding Nevada EPSCoR please visit: https://epscorspo.nevada.edu/ 

About DRI

The Desert Research Institute (DRI) is a recognized world leader in basic and applied environmental research. Committed to scientific excellence and integrity, DRI faculty, students who work alongside them, and staff have developed scientific knowledge and innovative technologies in research projects around the globe. Since 1959, DRI’s research has advanced scientific knowledge on topics ranging from humans’ impact on the environment to the environment’s impact on humans. DRI’s impactful science and inspiring solutions support Nevada’s diverse economy, provide science-based educational opportunities, and inform policymakers, business leaders, and community members. With campuses in Las Vegas and Reno, DRI serves as the non-profit research arm of the Nevada System of Higher Education. For more information, please visit www.dri.edu.

New NV Energy Foundation Grant Will Support Wildfire Preparedness in Nevada

New NV Energy Foundation Grant Will Support Wildfire Preparedness in Nevada

burning wildfire

March 30, 2022
RENO, NEV.

Wildfire Preparedness
Weather-Fire-Smoke Model
Fire Mitigation

New NV Energy Foundation Grant Will Support Wildfire Preparedness in Nevada

Funding will boost development of DRI‘s advanced weather-fire-smoke model

Check Presentation NV Energy Foundation

Representatives from NV Energy and DRI gathered Wednesday, March 30, 2022 at the DRI campus to announce a new grant that will provide $150,000 to support the development of a Weather and Research Forecast advanced modeling tool. 

Credit: DRI. 

Reno, Nev. (March 30, 2022) – As the climate warms, wildfires in the Sierra Nevada are happening at unprecedented sizes and intensities, threatening communities and resources throughout Nevada and California. For fire managers trying to understand and predict fire behavior, access to accurate information for decision-making has never been more important.

A generous grant from the NV Energy Foundation will provide $150,000 to support DRI’s development of a Weather and Research Forecast advanced modeling tool that simulates weather, fire, and smoke for firefighting and prescribed fire operations. Forecasts and simulations produced by this model will be available to NV Energy’s fire mitigation team, and other professionals from the prescribed fire and air quality communities in Nevada and California through the work of the California and Nevada Smoke and Air Committee (CANSAC).

“We are committed to protecting our customers and the environment from the increasing risks of natural disasters, which include wildfires,” said Doug Cannon, NV Energy president and chief executive officer. “The NV Energy Foundation is proud to support DRI in the development of this technology that will help firefighters better assess fire risk and keep our communities safe.”

Funds from the new NV Energy Foundation grant will be used to expand the current high-performance computer system that is used by CANSAC. The system will provide an interface where users such as prescribed fire managers can conduct simulations of fire spread and smoke behavior.

Caldor Fire Simulation

Screenshot of a simulation of the Caldor Fire created with the weather-fire-smoke model. Green lines indicate wind direction, red and yellow area indicates fire perimeter, and gray cloud represents smoke.  

Credit: Adam Kochanski/San Jose State University and Tim Brown/DRI. 

The model will allow for risk assessment of specific locations by modeling different burn scenarios, help meteorologists identify small-scale wind flows that could have adverse effects on fire spread and behavior, and provide critical air quality forecasts for wildfires or burn day decisions. Simulations can be run for near future forecasting (a few days out) or longer-term scenario modeling for projects that might occur a year or more into the future.

“This tool will be useful to wildfire fighting operations as well as for prescribed fire planning, which is essential to getting some of our fire-adapted ecosystems back into balance,” said Tim Brown, Ph.D., director of DRI’s Western Regional Climate Center. “By supporting the development of this tool, the NV Energy Foundation is providing a great resource to fire managers in Nevada and California and helping to ensure the safety of firefighters and communities across these two states.”

“With this generous grant, the NV Energy Foundation will play a key role in developing new technology that will be used to solve real-world problems in fire mitigation and fire safety,” said DRI President Kumud Acharya, Ph.D. “This project is an amazing example of how community organizations like NV Energy can partner with DRI scientists to develop solutions to the problems that face our society and environment.”

This project is supported by additional funds from the State of Nevada’s Capacity Building Program and DRI internal funding.

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About DRI

The Desert Research Institute (DRI) is a recognized world leader in basic and applied environmental research. Committed to scientific excellence and integrity, DRI faculty, students who work alongside them, and staff have developed scientific knowledge and innovative technologies in research projects around the globe. Since 1959, DRI’s research has advanced scientific knowledge on topics ranging from humans’ impact on the environment to the environment’s impact on humans. DRI’s impactful science and inspiring solutions support Nevada’s diverse economy, provide science-based educational opportunities, and inform policymakers, business leaders, and community members. With campuses in Las Vegas and Reno, DRI serves as the non-profit research arm of the Nevada System of Higher Education. For more information, please visit www.dri.edu.

About the DRI Foundation

The DRI Foundation serves to cultivate private philanthropic giving in support of the mission and vision of the Desert Research Institute. Since 1982, DRI Foundation trustees have worked with DRI benefactors to support applied environmental research to maximize the Institute’s impact on improving people’s lives throughout Nevada, the nation, and the world. 

About the NV Energy Foundation

NV Energy maintains the NV Energy Foundation, a 501c3, to support its philanthropic efforts. Through direct grants, scholarships and employee grant programs, the NV Energy Foundation actively supports improvements in the quality of life in NV Energy’s service territories. Information about the NV Energy Foundation is available at nvenergy.com/foundation.

Meet Dennis Hallema, Ph.D.

Meet Dennis Hallema, Ph.D.

Meet Dennis Hallema, Ph.D.

MARCH 24, 2021
LAS VEGAS, NEV.
Data Modeling
Hydrology
Wildfires
Above: Dennis Hallema of DRI studies natural catastrophe impacts, such as the longer-term impacts that wildfires have on flood risk after a fire has passed. The hillside shown here burned in California’s Loyalton Fire during August 2020.
Credit: Kelsey Fitzgerald.

Dennis Hallema, Ph.D., is an assistant research professor of hydrology with the Division of Hydrologic Sciences at DRI in Las Vegas. He specializes in data modeling and natural catastrophe research. Dennis is originally from the Netherlands and holds B.S. and M.S. degrees in Earth Sciences from Utrecht University in the Netherlands, and a Ph.D. in Continental hydrology and society from Montpellier SupAgro in France. A new addition to the DRI community, Dennis started working for DRI remotely from North Carolina in November 2021 and relocated to Las Vegas in March.

dennis hallema
Dennis Hallema, Ph.D.
Credit: Dennis Hallema.
DRI: Can you tell us a little bit about your background and what brought you to DRI? 

Hallema: I started at DRI in November of last year, so I am still fairly new here. If you had to describe me with two keywords, it would be hydrology and wildfires. I specialize in consulting on natural hazard impacts – not so much the natural hazards themselves, but the longer-term impacts that they have on things like flood risks. My methods are AI (artificial intelligence) focused – so, machine learning. When I applied for this job at DRI, there was really a need for a person who could do research on all of these aspects combined – a person that crossed the bridge between traditional hydrologic modeling and who could also apply newer methods like AI.

My background is in hydrologic modeling and fire science. I first did this work for the USDA Forest Service, where I was a research fellow with the Oak Ridge Institute for Science and Education (ORISE). That was my first big fellowship. I did that job for a few years, and that’s where I really became an expert in wildfire impacts on hydrology. Before that, I worked in Quebec City, Canada, on different jobs in hydrologic modeling of snowy landscapes, so I have experience doing snow modeling as well.

DRI: What are some of the ways that wildfires impact hydrology? Can you give us an example?

Hallema: I have studied this across the whole entire country looking at various regions where fires have an impact on runoff. The higher up you go in mountainous areas, you see very profound impacts. We can divide the impacts into primary perils and secondary perils. In the case of a wildfire, primary perils are the immediate damage. People lose their property, there are health impacts, there can be loss of life.

Secondary perils are what come later, after the fire has passed – the indirect effects that occur from the fire. In many cases, secondary perils are related to hillslope stability. You may remember the mudslides of California a few years ago. The hillslope becomes unstable because the wildfire can remove a large part of the vegetation canopy.  After the fire, when the first rainfall event occurs, the soil can often still absorb that. But when the second rain shower comes, and there’s nothing to retain or protect the soil, in case of very severe wildfires, the soil becomes saturated and essentially creates a sliding plane, and that’s when you get mudslides.

 

dennis hallema
Above: Dennis Hallema is an assistant research professor of hydrology with DRI in Las Vegas. In his free time, he enjoys spending time outdoors.
Credit: Dennis Hallema.
DRI: You recently published new research on wildfire risks to watersheds in Canada. Can you tell us about that?

Hallema: The paper was a review of the mechanisms that are responsible for wildfire impacts on water security and water resources across Canada. We mapped out where data are available, and what types of data are available, as far as wildfire occurrence, severity, streamflow data, and streamflow impacts. Data is often collected with publicly funded projects, so the ideal outcome would be that data should be accessible to other users later on. But this isn’t always the case.

One principle that we advocate for in this paper that I also want to promote in Nevada is the FAIR data principle. That stands for Findability, Accessibility, Interoperability, and Reuse of digital assets. Obstacles to that are data scarcity and data fragmentation. Data scarcity means that there is little data available, and data fragmentation means that the data exist, but they are stored in many different locations. There is a lot of opportunity to improve the depth of data collection and quality of datasets and improve and reduce the fragmentation of data.

DRI: Can you tell us about a project you’re working on here at DRI?

Hallema: I’m working on a project that is sponsored by the United States Army Corps of Engineers (USACE), and one thing that we’re exploring is the effect of rain on snow. This happens in landscapes in northern Nevada when temperatures are around the freezing point, and you get an interesting dynamic of snowmelt and snowfall. My research is really focused on how likely this is to generate a flood, such as a 50-year flood, or a 100-year flood. The way I’m approaching the problem is by looking at the interactions between rain, snow, and rain-on-snow events. I’m researching how these interactions at the land surface really affect the runoff that is generated, how that affects the probability of a flood occurring, and when during the season you see this elevated flood risk. That’s one thing I’m working towards – and in general also providing consulting for institutions like USACE for implementing machine learning and remote sensing technologies into natural hazards impact models, wildfire data modeling, water risk models, and such.

DRI: What do you like to do outside of work?

Hallema: I like to spend a lot of time outdoors. I like to travel, I speak a few languages. I’m lucky that the things I do for work are things that I really enjoy doing. Being outside, collecting data, and doing cool computer stuff when I get back to the office, that’s the fun of my job.

New study identifies atmospheric conditions that precede wildfires in the Southwest

New study identifies atmospheric conditions that precede wildfires in the Southwest

Reno, Nev. (January 3, 2018): To protect communities in arid landscapes from devastating wildfires, preparation is key. New research from the Desert Research Institute (DRI) in Reno may aid in the prevention of large fires by helping meteorologists and fire managers in the Southwestern U.S. to forecast periods of likely wildfire activity.

Each summer, from June through September, a weather pattern called the North American monsoon brings thunderstorms to the Southwestern U.S., with lightning that often sparks wildfires.

The new study, which published in the International Journal of Climatology, examined twenty common weather patterns that occur during the North American monsoon season, and identified relationships between certain weather patterns and times of increased fire activity.

One of the most problematic weather patterns, the team learned, was when dry and windy conditions gave way to lightning storms in May and June – a time when fuels tended to be at their driest and monsoon rains had not yet soaked the region with added moisture. When lightning storms were followed by another hot, dry, windy period, increased fire activity was even more likely.

“A lot of fire meteorologists know from experience that this is how things happen, but our study actually quantified it and showed how the patterns unfold,” said lead author Nick Nauslar, Ph.D., who completed this research while working as a graduate student at DRI under Tim Brown, Ph.D. “No one had ever really looked at large fire occurrence in the Southwest and how it related to atmospheric patterns.”

To identify problematic weather patterns, Nauslar and his team looked at monsoon season weather data collected from April through September over the 18-year period from 1995-2013. They then classified wildfire activity over the same period into days or events that were considered “busy” by fire managers in their study area, and used an analysis technique called Self-Organizing Maps to detect relationships between the two datasets.

In addition to identifying relationships between specific weather patterns and fire activity, their analysis also looked for patterns in wildfire occurrence and fire size throughout the season. Analysis of more than 84,000 wildfires showed that although July was the month that the most wildfires occurred, wildfires that occurred during the month of June (prior to the arrival of much monsoonal moisture) were more likely to develop into large fires. In July and August, when the heaviest monsoonal precipitation typically occurs, the percentage of fires that developed into large fires decreased.

“Our goal with this study was to provide fire weather meteorologists in the region with information to help inform fire forecasts, and I think we were able to identify some important patterns,” said Brown, Director of the Western Regional Climate Center at DRI.

Nauslar, who is now employed as a mesoscale assistant and fire weather forecaster for the National Oceanic and Atmospheric Administration (NOAA) Storm Prediction Center in Norman, Oklahoma, hopes that the findings of this study will help fire managers in the Southwest to proactively identify periods when wildfires are more likely to occur, and to allocate firefighting resources accordingly.

“I think a lot of what we learned confirms forecaster experience about the types of atmospheric patterns that are problematic with regard to wildfire occurrence in the Southwest,” Nauslar said. “I hope that people in operations can really use this information, and help refine it and build upon it.

Other DRI scientists who contributed to this research included Benjamin Hatchett, Ph.D., Michael Kaplan, Ph.D., and John Mejia, Ph.D. The full study, titled “Impact of the North American monsoon on wildfire activity in the southwest United States,” is available online from the International Journal of Climatology: https://rmets.onlinelibrary.wiley.com/doi/abs/10.1002/joc.5899

 

The Desert Research Institute (DRI) is a recognized world leader in basic and applied interdisciplinary research. Committed to scientific excellence and integrity, DRI faculty, students, and staff have developed scientific knowledge and innovative technologies in research projects around the globe. Since 1959, DRI’s research has advanced scientific knowledge, supported Nevada’s diversifying economy, provided science-based educational opportunities, and informed policy makers, business leaders, and community members. With campuses in Reno and Las Vegas, DRI serves as the non-profit research arm of the Nevada System of Higher Education. Learn more at www.dri.edu, and connect with us on social media on FacebookInstagram and Twitter. 

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Low-severity wildfires impact soils more than previously believed

Low-severity wildfires impact soils more than previously believed

Above: In semi-arid ecosystems such as the Humboldt-Toiyabe National Forest near Las Vegas, which burned as part of the Carpenter 1 fire during July and August 2013, fuel is limited and fires tend to be short lived and low in peak temperature. New research shows that these fires are more harmful to soils than they initially appear. This photo was taken on January 6, 2015 – approximately 18 months after the wildfire. Credit: Teamrat Ghezzehei, UCM.


New research shows negative effects of fire on soil structure and organic matter

Las Vegas, NV (August 28, 2018): Low-severity wildland fires and prescribed burns have long been presumed by scientists and resource managers to be harmless to soils, but this may not be the case, new research shows.

According to two new studies by a team from the University of California, Merced (UCM) and the Desert Research Institute (DRI), low-severity burns – in which fire moves quickly and soil temperature does not exceed 250oC (482oF) – cause damage to soil structure and organic matter in ways that are not immediately apparent after a fire.

“When you have a high-severity fire, you burn off the organic matter from the soil and the impact is immediate,” said Teamrat Ghezzehei, Ph.D., principal investigator of the two studies and Associate Professor of Environmental Soil Physics at UCM. “In a low-severity fire, the organic matter doesn’t burn off, and there is no visible destruction right away. But the burning weakens the soil structure, and unless you come back at a later time and carefully look at the soil, you wouldn’t notice the damage.”

DRI researcher Markus Berli, Ph.D., Associate Research Professor of Environmental Science, became interested in studying this phenomenon while visiting a burned area near Ely, Nev. in 2009, where he made the unexpected observation that a prescribed, low-severity fire had resulted in soil structure damage in the burned area. He and several colleagues from DRI conducted a follow-up study on another controlled burn in the area, and found that soil structure that appeared to be fine immediately after a fire but deteriorated over the weeks and months that followed. Berli then teamed up with Ghezzehei and a team from UCM that included graduate student Mathew Jian, and Associate Professor Asmeret Asefaw Berhe, Ph.D., to further investigate.

Researcher examines soils in a burned area near Las Vegas.

Researcher Markus Berli from the Desert Research Institute examines the soils at a burned area in the Humboldt-Toiyabe National Forest near Las Vegas on January 6, 2015, approximately 18 months after the area burned in the Carpenter 1 fire of 2013. Credit: Teamrat Ghezzehei, UCM.

Soil consists of large and small mineral particles (gravel, sand, silt, and clay) which are bound together by organic matter, water and other materials to form aggregates. When soil aggregates are exposed to severe fires, the organic matter burns, altering the physical structure of the soil and increasing the risk of erosion in burned areas. In low-severity burn areas where organic matter doesn’t experience significant losses, the team wondered if the soil structure was being degraded by another process, such as by the boiling of water held within soil aggregates?

In a study published in AGU Geophysical Research Letters in May 2018, the UCM-DRI team investigated this question, using soil samples from an unburned forest area in Mariposa County, Calif. and from unburned shrubland in Clark County, Nev. to analyze the impacts of low-severity fires on soil structure. They heated soil aggregates to temperatures that simulated the conditions of a low-severity fire (175oC/347oF) over a 15-minute period, then looked for changes in the soil’s internal pore pressure and tensile strength (the force required to pull the aggregate apart).

During the experiment, they observed that pore pressure within the soil aggregates rose to a peak as water boiled and vaporized, then dropped as the bonds in the soil aggregates broke and vapor escaped. Tensile strength measurements showed that the wetter soil aggregates had been weakened more than drier soil samples during this process.

“Our results show that the heat produced by low-severity fires is actually enough to do damage to soil structure, and that the damage is worse if the soils are wet,” Berli explained. “This is important information for resource managers because it implies that prescribed burns and other fires that occur during wetter times of year may be more harmful to soils than fires that occur during dry times.”Next, the research team wondered what the impact of this structural degradation was on the organic matter that the soil structure normally protects. Soil organic matter consists primarily of microbes and decomposing plant tissue, and contributes to the overall stability and water-holding capacity of soils.

In a second study that was published in Frontiers in Environmental Science in late July, the UCM-DRI research team conducted simulated burn experiments to weaken the structure of the soil aggregates, and tested the soils for changes in quality and quantity of several types of organic matter over a 70-day period.

They found that heating of soils led to the release of organic carbon into the atmosphere as CO2 during the weeks and months after the fire, and again found that the highest levels of degradation occurred in soils that were moist. This loss of organic carbon is important for several reasons, Ghezzehei explained.

“The loss of organic matter from soil to the atmosphere directly contributes to climate change, because that carbon is released as CO2,” Ghezzehei said. “Organic matter that is lost due to fires is also the most important reserve of nutrients for soil micro-organisms, and it is the glue that holds soil aggregates together. Once you lose the structure, there are a lot of other things that happen. For example, infiltration becomes slower, you get more runoff, you have erosion.”

Researcher collects soil samples in burned area near Las Vegas.

Researcher Rose Shillito from DRI collects soil samples in a burned area in the Humboldt-Toiyabe National Forest near Las Vegas on January 6, 2015, approximately 18 months after the area burned in the Carpenter 1 fire of 2013. Credit: Teamrat Ghezzehei, UCM.

Although the research team’s findings showed several detrimental effects of fire on soils, low-severity wildfires and prescribed burns are known to benefit ecosystems in other ways — recycling nutrients back into the soil and getting rid of overgrown vegetation, for example. It is not yet clear whether the negative impacts on soil associated with these low-severity fires outweigh the positives, Berli says, but the team hopes that their research results will help to inform land managers as they manage wildfires and plan prescribed burns.

“There is very little fuel in arid and semi-arid areas, and thus fires tend to be short lived and relatively low in peak temperature,” Ghezzehei said. “In contrast to the hot fires and that burn for days and weeks that we see in the news, these seem to be benign and we usually treat them as such. Our work shows that low-severity fires are not as harmless as they may appear.”

The study, “Soil Structural Degradation During Low‐Severity Burns,” was published on May 31, 2018 in the journal AGU Geophysical Research Letters and is available here: https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2018GL078053.

The study, “Vulnerability of Physically Protected Soil Organic Carbon to Loss Under Low Severity Fires,” was published July 19, 2018 in the journal Frontiers in Environmental Science, and is available here: https://www.frontiersin.org/articles/10.3389/fenvs.2018.00066/full.

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The Desert Research Institute (DRI) is a recognized world leader in basic and applied interdisciplinary research. Committed to scientific excellence and integrity, DRI faculty, students, and staff have developed scientific knowledge and innovative technologies in research projects around the globe. Since 1959, DRI’s research has advanced scientific knowledge, supported Nevada’s diversifying economy, provided science-based educational opportunities, and informed policy makers, business leaders, and community members. With campuses in Reno and Las Vegas, DRI serves as the non-profit research arm of the Nevada System of Higher Education. For more information, please visit  www.dri.edu.