USDA Forest Service
 

Pacific Southwest Research Station


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Pacific Southwest
Research Station

800 Buchanan Street
Albany, CA 94710-0011
(510) 883-8830
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Research Topics Fire Science

Harvesting fire-killed trees

A patch of smalll burned sticks remains of tree seedlings following a high severity wildfire.
Fire effects from an area burned at high severity in the 1999 Megram Fire and burned again in the 2009 Backbone Fire. Fallen snags from the previous fire can lead to higher severity re-burns. In this case, consumption of down logs killed tree seedlings that established after the first fire. U.S. Forest Service photo by Eric Knapp.

Whether to salvage trees in the immediate aftermath of high severity wildfire is a complex and controversial topic. Fire-killed trees that are left standing (snags) provide valuable habitat for many wildlife species. Also, the post-fire environment is highly disturbed and any additional soil disturbance could potentially contribute to erosion, promote the invasion of exotic plants, or kill tree seedlings and other plants that re-establish after the fire.

In the short term, many of the strongest arguments for cutting fire-killed trees are economic (extracting some value and putting people to work) or safety related (removing snag hazard during future forest management activities and along roads). The majority of fire-killed snags remain standing for less than 10 years, so, in the longer term, snags fall to the ground and become fuel.

Where fallen snags create heavy concentrations of downed woody fuel, subsequent fires have a higher probability of top-killing all vegetation, including regenerating trees that established after the first fire. Where the scale and extent of stand-replacing tree patches (areas with overstory tree mortality) are outside of the historical norm, or where forest density was unnaturally high prior to the wildfire, the effect of excess downed wood on future fire behavior is likely to also be outside of the historical norm.  The elevated probability of high-severity fire will remain until dead and down fuels are returned to more appropriate levels, often by repeated wildfires. Only then will conditions be optimally suited for the re-establishment of new trees.

Post-fire salvage can help reduce excess fuels and decrease the risk of subsequent high-severity wildfires. Converting dead trees into long-lived forest products rather than allowing them to decompose in the field or burn in future wildfires may also provide carbon sequestration benefits. Managers can better balance potentially negative impacts, in part, by thoughtfully and strategically leaving snags standing for wildlife at varying spatial scales and/or prioritizing salvage for areas where future fire hazard concerns are the most acute. Post-fire salvage efforts also provide foresters the opportunity to go back in to these areas and plant new trees to potentially restore forest conditions.

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Last Modified: Dec 19, 2016 03:02:37 PM