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Fuel: logs, sticks, needles, duff, and much more

Author(s): Russell T. Graham, Theresa B. Jain, Alan E. Harvey
Year Published: 2000

Fuels burned by either prescribed or wildfires are complex and important components of forested ecosystems. Fine fuels consisting of fallen limbs, twigs, and leaves of shrubs and trees are rich in nutrients. If these fuels are not immediately burned, nutrients can leach from these materials into the forest floor, especially if they overwinter. Larger fuels consisting of standing dead trees, large limbs, and down logs or coarse woody debris (CWD) play critical roles in fixing and storing nitrogen (N), protecting the soil surface, and supplying organic matter to the forest floor. Up to 40% of the top 30 cm of a forest soil can be composed of rotten CWD buried (soil wood) in the mineral soil. In addition the litter layer (duff) composed of rotten wood, leaves, twigs, needles, cones, and other fine fuels decompose to form the humus layer. These surface layers coupled with soil wood store and release nutrients, are sites for nitrogen fixation, and provide habitat for ectomycorrhizae. Depending on the ecosystem, amounts of CWD desired for maintaining soil productivity range from 15 Mg ha-1 (7 tons ac-1) in ponderosa pine forests of northern Arizona to 74 Mg ha-1 (33 tons ac-1) in western hemlock forests of northern Idaho. Fires occurring when the lower organic layers are moist ensures preservation of much of the microbiological and nutrient properties of these organic components. These organic components are critical for sustaining forested ecosystems and how they are burned can have both short- and long-term impacts on forest productivity. Therefore both mechanical and fire fuel treatments used to meet reforestation and hazard reduction objectives should conserve these materials.

Citation: Graham, Russell T.; Jain, Theresa B.; Harvey, Alan E. 2000. Fuel: logs, sticks, needles, duff, and much more. In: Crossing the millennium: integrating spatial technologies and ecological principles for a new age in fire management, 1999 Joint Fire Science Conference and Workshop. 1999 June 15-17; University of Idaho and the International Association of Wildland Fire. p. 189-194.
Topic(s): Fire Effects, Ecological - First Order, Fire Intensity / Burn Severity, Ecological - Second Order, Soils, Fire Regime
Ecosystem(s): Subalpine wet spruce-fir forest, Subalpine dry spruce-fir forest, Montane wet mixed-conifer forest, Montane dry mixed-conifer forest
Document Type: Conference Proceedings, Synthesis
NRFSN number: 10957
FRAMES RCS number: 2378
Record updated: May 10, 2018