A year after the second-largest fire season on record in Alaska, the 2015 fire season is still smoking.
The Alaska Division of Forestry has detected 16 “holdover” fires so far this season, including one on Saturday that ignited the 8,130-acre Medfra Fire now burning in a remote part of Southwest Alaska.
Holdover fires are just what the term implies, fires that were thought to be extinguished but come back to life the following season when conditions dry out and temperatures warm up. While not uncommon in fire-prone Alaska, the number of holdover fires this summer is much higher than normal.
State Forestry has found 12 holdover fires in the Kenai/Kodiak Area, three in Southwest Alaska and one in the Mat-Su Valley. All but one of those reported on the Kenai Peninsula were found within the perimeter of the Card Street Fire that burned almost 8,900 acres last year near Soldotna. The remaining holdover fire was from the 2014 Funny River Fire, which burned almost 200,000 acres.
Firefighters in the Mat-Su Valley on Sunday discovered a holdover fire from last year’s 7,500-acre Sockeye Fire in Willow.
The three holdover fires in Southwest Alaska are progeny of the Soda Creek Fire, which burned approximately 16,500 acres last summer.
The term holdover fire is somewhat of a misnomer. More often they are holdover hot spots that consist of a small, smoldering patch of burned ground putting off enough smoke to be visible. However, if that hot spot is located on the perimeter of the fire near unburned fuel, all it takes is an ember carried by wind to ignite the unburned fuel and start a new wildfire.
Holdover fires are common in Alaska because the duff layer that blankets the forest floor – including moss, twigs, leaves and spruce needles, etc. – is so thick, said Alaska Division of Forestry fire behavior analyst Robert Ziel.
“In the high boreal forest in Alaska there is so much fuel and it’s so deep, once fire gets established it’s hard to put out,” Ziel said. “They get buried below where they can get moisture, the duff above them absorbs the moisture and once the ground freezes they become impervious.”
The frozen duff acts as a sort of insulating umbrella, he said.
More than 5.1 million acres burned in Alaska last summer, making it the second-largest fire season on record. The volume of fire last summer combined with a lack of snow cover last winter as well as a warm, dry spring is likely contributing to the high number of holdover fires, Ziel said.
“There are probably holdover fires every year and the question is whether we get the conditions that expose them,” Ziel said.
Most of the holdover fires have been in stands of low-lying black spruce that burned extremely hot last summer, Ziel said. The hotter a fire burns the deeper down it goes, he said.
Several of the holdover fires found on the Card Street Fire have been located right along the edge of the fire perimeter, Howie Kent, Fire Management Officer for the Division of Forestry’s Kenai/Kodiak Area, said. Those are the hot spots that worry Kent and other fire managers.
“The Card Street Fire didn’t burn cleanly; there’s a lot of mosaic, a lot of unburned fuel out there,” Kent said. “There’s still potential for a 5- to 10-acre fire to make a run to the edge of the perimeter and get out into the green. That’s what we’re trying to prevent.”
Fire managers and researchers are just beginning to study holdover fires, i.e. the conditions they are found in, how often they occur and the problems they cause.
“It’s one thing to say you’ve got holdover fires and it’s another thing to say how they’re going to affect fire management,” Ziel said.
Given the volume of fire on the landscape last summer, fire managers expect more holdover fires to pop up in other parts of the state as conditions get hotter and drier.
“It will be interesting to see with how much fire we had around the state last year how widespread our discoveries will be,” Ziel said.