USDA Forest Service

Pacific Southwest Research Station

Pacific Southwest
Research Station

800 Buchanan Street
Albany, CA 94710-0011
(510) 883-8830
United States Department of Agriculture Forest Service. USDA logo which links to the department's national site. Forest Service logo which links to the agency's national site.

Research Topics Fire Science

Masticated Fuels:
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Masticated Fuels Research

Fuel loading in masticated areas

While small trees and shrubs can be chipped and sold to generate energy, market conditions for biomass are volatile and removal of this biomass is often not cost effective. Masticated biomass is therefore usually left on the forest floor to protect the soil from erosion and to retain nutrients. The biomass contained within the shrubs, hardwoods, and small conifers can be considerable. Masticated wood is often highly fractured and fragmented, with a high surface area: volume ratio. Size and shape of the individual pieces depends on the specific machinery used and amount of mastication effort (i.e. the amount of time spent per unit area).

We sampled fuels at 10 masticated sites from SW Oregon to the central Sierra Nevada in California, using both a plot-based method and Brown's planar intercept method. Final fuel loading values for fine woody fuels, litter, and duff were from plot data and fuel loading values for large woody fuels were from transect data.

Key findings:
  • The surface fuel load at some sites was considerable. Most of the masticated wood at all sites fell within the 10 hr (1/4 -1 in. diameter) size category.
  • Fuel bed is quite compact, which is expected to moderate fire behavior. Compactness is related to operator effort (time spent per unit area) and the mastication machinery used, with drum-type cutting heads yielding finer particle size and more compact fuel bed than rotary cutting heads. Because of the variability in particle size, fuel loading is not well predicted by fuel bed depth.
  • We recommend using a hybrid methodology for evaluating loading in masticated fuelbeds, where 1-h and 10-h fuels are estimated with a plot-based method, and larger fuels estimated with the standard Brown's transect method. If a high level of accuracy is not necessary, fuel loading can also be roughly estimated using a fuel loading photo series (below).
Fuel loading (masticated wood plus litter) at 10 masticated sites, listed from lowest to highest. (click on site name for photographs and additional site information).
Site name 1hr
Total masticated
wood + litter
Tons/ acre
Shasta 2.1 3.7 0.6 8.5
Whitmore 2.0 4.2 0.7 9.2
Iron Mtn 2.8 6.2 1.6 12.3
Sierraville 2.3 5.0 2.9 12.9
Whiskeytown 5.3 7.3 1.6 17.5
Taylor Ridge 5.9 9.7 0.9 21.8
Challenge 4.8 10.4 3.4 23.8
Applegate 5.5 11.0 3.8 25.2
Stanislaus 7.0 11.2 2.1 26.6
Mad River 10.5 15.6 2.3 29.6
Last Modified: Dec 19, 2016 02:46:58 PM