Understanding Fire

Fire scientists study how fires burn and use that information to develop tools and techniques for protecting homes and forests. Understanding fire behavior will help you better prepare your home and landscape for wildfire.

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Flame Front

Recently there have been very extreme fires with large fire fronts and fire tornadoes that burn everything in their paths. Though these are dramatic events, they are not how the majority of homes burn. Forest thinning and prescribed fire projects around neighborhoods help to reduce the intensity of wildfires near homes.

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Embers

The majority of homes that burn in wildfires burn when embers land on vulnerable areas of the house and landscape and start small fires. When no firefighter is available to contain these small fires they grow and destroy the house. Residents can reduce their risk by improving their homes’ ignition resistance and creating defensible space.

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Radiant Heat

Homes can burn when the heat from a fire very nearby (such as a next door neighbor’s house burning) directly ignites vegetation, or siding or breaks windows allowing the fire to get into the house. Residents can reduce their risk by improving their homes' ignition resistance and creating defensible space.

How Forests Burn

In a forest where fires rarely happen fuel accumulates over time. There’s surface fuel (grass, logs, woody debris, brush), ladder fuel (shrubs, small trees), and tree crowns. The severity of fires that ignite in a forest can be reduced by removing and modifying fuels.

uf-slide4 T r e e C r o w n s L a d d e r F u e l S u r f a c e F u e l S u r f a c e F i r e s s p r e a d q ui c k l y t h r o u g h b r u s h a n d w o o d y d e b r i s L a d d e r F u el s a l l o w t h e fir e t o m o v e u p into the tree crowns will burn when thereis plentiful surface and ladder fuels below C r o w n Fires

Note: Fuels reduction involves removing surface fuels, reducing shrubs and small trees that can act as ladders for fires to get into tree crowns, pruning large trees to make it more difficult for flames to reach into the crowns, and removing trees so their crowns no longer touch.

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Low Severity Fires burn mainly on the forest floor, consuming fuels and small trees and shrubs but not killing the majority of the mature trees on site. These fires help thin the forest and keep down fuels leading to a healthier and more resilient forest.

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High Severity Fires kill most of the trees in the forest by burning through their canopies. The size and frequency of high severity fires have been steadily increasing throughout the Sierra Nevada.

Tools to Reduce Fire Severity

The goal of forest projects at Lake Tahoe is to reduce the severity of fires that may burn in the area, not to eliminate fire altogether. This is done by forest thinning and prescribed fire.

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Thinning involves reducing the number of small trees in the forest by cutting and removing them from the site with equipment.

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Prescribed Fires are set by forest managers during less flammable weather conditions and kept within control lines so that the fire is of low severity, consuming fuels that would otherwise burn at high severity during dangerous weather.

Note: These fuel reduction efforts have been successful at reducing height of flames and the number of trees killed by fires.