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Fire Management: Monitoring a Masticated Fuel Break on the Kenai Peninsula
Alaska Region, June 16, 2017
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Plot M-23 in 2016, before treatment.
Plot M-23 in 2016, before treatment. - Photo Credit: USFWS
Plot M-23 in 2017, after mastication.
Plot M-23 in 2017, after mastication. - Photo Credit: USFWS
Yukon Fire Crew members collect masticated material from a study plot for weighing and chip measurement back at the lab
Yukon Fire Crew members collect masticated material from a study plot for weighing and chip measurement back at the lab - Photo Credit: USFWS

The site was unrecognizable from the year before, except for bright pink paint on a few lonely paper birch trees standing in a field of wood chips. We were in the middle of a fuel break established the previous winter to protect residents of Sterling, AK in the event that a wildfire approached the community from the Kenai National Wildlife Refuge (NWR) to the north and east.

In order to decrease the amount and structure of burnable vegetation (fuels) and change fire behavior, trees and understory growth were masticated, or mulched, into chunks of wood and chips. The fuel break is unlikely to stop a fire in its tracks. It will, however, cause a fire to drop out of the tree canopy onto the ground, lowering flame lengths, slowing the fire’s progress, and providing a safer place for firefighters to work. Keeping fire out of the tree canopy also reduces spotting, when embers are lofted from the tops of burning trees, potentially traveling long distances before they land and ignite small fires ahead of the main fire. In some cases, trees are left standing in masticated fuel breaks for aesthetic purposes or, in the case of the birch, to promote growth of deciduous species rather than flammable black spruce that dominated the area before.

Staff from the Fish and Wildlife Service’s Alaska fire management program, Kenai NWR’s Youth Conservation Corps crew, and several members of Chugachmiut Native Corporation’s Yukon Fire Crew worked together to monitor changes in the fuel break over time, starting with conditions before mastication began. Masticated fuel breaks are becoming more common throughout the country because it is more cost effective to masticate large areas compared to thinning a forest by removing individual trees. However, there is still a lot we don’t know about how these fuel breaks will change over time, both ecologically and how they will respond in a fire.

From an ecological standpoint, we are unsure about what types of vegetation will come back and how long it will take. Ideally, more deciduous trees and shrubs will move into the fuel break, providing a natural damper of fire behavior for years to come. If more flammable vegetation recovers, monitoring will help determine how often the area needs to be retreated to maintain its effectiveness. Other concerns include potential seeding in of non-native invasive plant species or establishment of bluejoint reedgrass. Although this annual grass is native to Alaska it can dominate large areas and is easily ignited when dead and dry, promoting fast fire spread. Despite this, it is easier to manage a grass fire than one moving through black spruce.

Another unknown factor is how the masticated material will burn if a wildfire moves through it. Fire crews may intentionally burn the fuel break and the vegetation between the break and the wildfire, robbing the approaching fire of burnable material in order to stop it or greatly reduce its progress. Little is known about how easy it is to ignite masticated fuels, how quickly they may burn once ignited, how long they may smolder, how deeply they may burn, and what emissions they may produce. Differences in size, shape, and depth of the masticated material will affect how it burns, and these will be influenced by type of mastication machinery, operator technique, and what vegetation was originally on the site.

Finally, time affects how masticated sites burn as the woody material becomes weathered, more compacted, and mixed with the underlying soil. To investigate these properties, chips are being collected from monitoring plots for further measurement. Answers to these questions will improve our ability to design efficient and effective fuel breaks and better protect firefighter safety.


Contact Info: Lisa Saperstein, 9077863422, lisa_saperstein@fws.gov
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