Researchers: hotter fires may heat underlying soil less than cooler fires

Researchers studying a 22-acre prescribed fire in Portugal have concluded that fires which burn hotter do not necessarily produce higher soil temperatures. Below is an excerpt from an American Geophysical Union press release.

When scientists torched an entire 22-acre watershed in Portugal in a recent experiment, their research yielded a counterintuitive result: Large, hot fires do not necessarily beget hot, scorched soil.

It’s well known that wildfires can leave surface soil burned and barren, which increases the risk of erosion and hinders a landscape’s ability to recover. But the scientists’ fiery test found that the hotter the fire—and the denser the vegetation feeding the flames—the less the underlying soil heated up, an inverse effect which runs contrary to previous studies and conventional wisdom.

Rather, the soil temperature was most affected by the fire’s speed, the direction of heat travel and the landscape’s initial moisture content. These new findings could help forest managers plan when and where to ignite small controlled burns to reduce dry vegetation and restore the ecosystem in at-risk areas, said Cathelijne Stoof, the soil and water scientist who led this study as part of her PhD research at Wageningen University in the Netherlands.

A report about the experiment by Stoof, who is now at Cornell University in Ithaca, New York, and her colleagueshas been accepted for publication by Geophysical Research Letters, a journal of the American Geophysical Union.

To some people this may be “counterintuitive”, but many firefighters know the residence time, or how much time high temperatures exist at a location, is very important in determining how much heat is transferred into the soil or the organic material that is not consumed by the fire.

On a related subject…

In two previous fire management jobs I had the opportunity to assist researchers who were measuring the temperature at which wildland fires burn. Obtaining this data is not the easiest thing in the world.

In southern California I helped place thermocouples, which can measure very high temperatures, on brushy hillsides prior to a prescribed fire. Then, trying not to disturb the vegetation which could influence fire behavior when the site was burned, I crawled under the brush running asbestos-covered wires from the thermocouples to data loggers which were about the size of a football. Each one recorded information from several scattered thermocouples. Then we had to bury the data loggers so they could survive the fire. This was in the 1970s. The researchers in the Portugal study mentioned above used thermocouples and data loggers, but the data loggers were probably about the size of a package of chewing gum — much easier to bury.

On another project the temperature was measured using heat sensitive paint, a much less accurate system. About eight different paints were used which discolored at specific temperatures. A narrow strip of each paint was brushed onto a very thin strip of aluminum which was stapled onto stakes, sticking out to the side at various heights above the ground. After the fire burned through you would examine the strips and you might see, for example, that the 1,200 degree paint discolored but the 1,250 degree paint did not, so you could conclude that the temperature at that location was between 1,200 and 1,250 degrees. Sometimes it was a judgement call about which paints discolored and which ones did not.

At what temperatures do forest fires burn?

We’ve been asked a few times, “what is the temperature of a forest fire”, so we placed an entry on our Frequently Asked Questions page:

An average surface fire on the forest floor might have flames reaching 1 meter in height and can reach temperatures of 800°C (1,472° F) or more. Under extreme conditions a fire can give off 10,000 kilowatts or more per meter of fire front. This would mean flame heights of 50 meters or more and flame temperatures exceeding 1200°C (2,192° F). (Information provided by Natural Resources Canada.)

How hot is the sun?

On our Facebook page someone once wrote that forest fires burn hotter than the sun. He, of course, was badly and sadly mistaken. According to

The temperature in the photosphere [near the surface] is about 10,000 degrees F (5,500 degrees C). It is here that the sun’s radiation is detected as sunlight.

The interior of the sun is much hotter and can reach more than 27 million degrees F (15 million degrees C).

Double firefighter fatalities in Portugal

FirefighterCloseCalls is reporting that two Portuguese firefighters have died as a result of burns they received while working on a wildfire:



In Portugal, on September, 21st, Volunteer FF Pedro Manuel Santos Brito died in the Line of Duty from burns. He passed away in the University of Coimbra Hospital. A member of the Corpo de Bombeiros Voluntários de Côja, FF Brito suffered 2nd and 3rd degree burns while operating in a wildland fire in the woods of Casal Cimeiro, in Arganil, Portugal on Sep. 15th. The same fire also had already claimed the life of 25-year-old Volunteer FF Patrícia Alexandra Rodrigues Abreu. Three other FFs were injured in the blaze, but are recovering well. Our condolences to all affected. RIP.

Monday morning one-liners

Fire near Pompeys Pillar, MT, BAe-146
A BAe-146 air tanker drops on a fire near Pompeys Pillar, MT, Sept. 2, 2012. Photo by Lisa Openshaw, Shepherd Volunteer Fire Department

On Sunday firefighters stopped a fire after it burned 326 acres north of Pompeys Pillar in Montana (see photo above).

The National Interagency Fire Center moved the national preparedness level from four to three.

Elizabeth Reinhardt of the USFS and Dick Bahr of the NPS are quoted in an article about how larger and more frequent fires over the last several decades have limited the size of some fires, as they move into the previously burned areas.

Wildfire south of Porto, Portugal, September 2, 2012
Wildfire south of Porto, Portugal, September 2, 2012

Hot, dry, and windy weather led to several large wildfires in Portugal on Sunday.


Thanks go out to Kelly

Wildland firefighter LODDs, 2010

At Wildfire Today we try to keep track of the line of duty deaths (LODD) of firefighters working on wildland fires. The past year, 2010, again produced a lengthy list of firefighters who passed away while doing their job. We make no claim that it is a complete or official tally. If you are aware of any that we missed, let us know. Some of the dates are approximate and may be the date of the report of the fatality. The last three incidents are gray areas, in that the victims were not all firefighters, or were not necessarily actively involved in fire suppression at the time of the incident. They were included because they were very significant incidents.

At the end of the list is a report from the U.S. Fire Administration providing their statistics on the number of LODDs for 2010.

January 11. Australia. A firefighter was killed and four others were injured when their fire truck rolled over while they were responding to a grass fire at Lake Mokoan near Benalla in northeast Victoria, Australia. (map)

April 11. Kansas.  A firefighter was overcome by smoke and died while working on a fire west of Peru.

April 24. New Brunswick, Canada. A pilot from Grand Falls, with Forest Protection Ltd., was conducting a practice flight in a water bomber when the plane crashed shortly after taking off from the airport.

June 23. Washington. The chief of the Franklin Fire District 4 in Basin City, Washington, was killed when a snow cat that had been converted to a fire apparatus rolled about 100 feet down a hill while he was working on a vegetation fire.

July 30. Russia. Wildfires in Russia killed at least 25 people including 2 firefighters, and destroyed over 1,000 homes. Some reports say three firefighters died in the fires.

July 31. Canada. An air tanker crashed while working on a fire in British Columbia. The Convair 580, operated by Conair, went down in central B.C. The two pilots were killed.

August 2. Arkansas. A firefighter was operating an Arkansas Forestry Commission 2002 International tractor trailer, and was en route to check on the status of an earlier fire. The tractor trailer load reportedly shifted causing the vehicle to cross the roadway center line, go into a ditch and then overturn.

August 11. Portugal. Civil protection officials said a female firefighter died, one fireman was badly burned and their team had to be evacuated when they found themselves surrounded by flames after a sudden change in the direction of the wind in Gondomar region. On Monday, a fireman was killed and another seriously injured when their truck fell into a burning ravine in the mountainous Sao Pedro do Sul area.

August 13. Spain. Two firefighters were been killed in wildfires. The blazes hit near the village of Fornelos de Montes in the country’s northwestern Galicia region, close to the border with Portugal, where several forest fires are still raging.

September 21. Spain. A 46-year old firefighter died while extinguishing a wildfire in Senes.

September 24. Ohio. A firefighter was killed when a pressurized tank failed and he was struck by debris.

September 24. Virginia. A firefighter collapsed and later died while working on a fire in New Church, Virginia off Route 13.

November 16. South Carolina. A firefighter was suppressing a grass fire in the median of Interstate 20 when a van rear-ended a sedan as they approached the fire scene. The sedan was pushed into two parked fire trucks causing them to crash into a firefighter, causing his death.

November 23. California. One inmate was killed and 12 were injured when their crew carrier vehicle was involved in a head-on accident. Three of the injured were in critical condition. The elderly driver of the other vehicle was also killed. As far as we know the inmate crew was not assigned to a fire at the time of the crash.

December 5. China. A massive wildfire in Tibet’s Sichuan province killed 22 people, including Chinese soldiers during a rescue operation. Of the 22 killed, 15 were soldiers, two were workers with the grassland administration, and five others were local civilians.

December 6. Israel. At least one of the 43 government employees that were killed in the Carmel Mountain fire in Israel was a police officer. The Police Chief in Haifa (Israel) died in the Line of Duty from her burn injuries after 4 days of hospitalization. She was the first ever woman police chief there, and was gravely injured in the Carmel forest fire, while driving along with the bus full of Prison Service cadets that burned and killed the cadets as well.

Below is the The U.S. Fire Administration’s report of the on-duty firefighter fatalities in 2010. Click on FullScreen to see a larger version.

Continue reading “Wildland firefighter LODDs, 2010”

Russian air tanker in Portugal hits trees and starts fires

We just found out about this incident that occurred in Portugal. From Wikinews:

The Russian Beriev 200 [air tanker] leased to the Portuguese Government suffered an accident last Thursday (July 6, 2006) afternoon, after one of its engines was damaged.

The accident occurred after a refueling operation at the dam of Aguieira, near Santa Comba Dão. As the aerial firefighting aircraft took off at the end of the refueling maneuver in the water – designated as ‘scooping’ – its “left wing hit the top of the trees and the aircraft suffered some damage” to its fuselage, said Colonel Anacleto dos Santos, director of the Cabinet of Prevention and Investigation of Accidents with Aircraft (GPIAA), to the Portuguese newspaper Correio da Manhã.

While hitting the top of the trees, leaves and some wood entered the left engine, which didn’t blow up, but that had to be turned off and the pilot was forced to release fuel for safety reasons. The release of the fuel started small wildfires across the area, reaching some houses, which were quickly extinguished by firefighters and helitack units of the GNR’s Intervention, Protection and Rescue Group.
The airplane was able to do an emergency landing at the Monte Real Air Base, where it’s currently operating from, thanks to the flight experience of one of the Russian pilots. When contacted by the Lusa news agency, National Service of Firefighters and Civil Protection, vice-president Lieutenant-Colonel Joaquim Leitão explained that the repairs will be made by the aircraft company and that all the parts necessary to repair the damages will have to come from Russia, by which the solution for the problem will take “some days”.

Be-200 air tanker
File photo of a Be-200 Russian-made air tanker

Thanks and a tip of the hat go out to Chuck.