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Surface fuel loadings within mulching treatments in Colorado coniferous forests

Formally Refereed

Abstract

Recent large-scale, severe wildfires in the western United States have prompted extensive mechanical fuel treatment programs to reduce potential wildfire size and severity. Fuel reduction prescriptions typically target non-merchantable material so approaches to mechanically treat and distribute residue on site are becoming increasingly common. We examined how mulch treatments alter the distribution of woody material by size class by comparing paired mulched and untreated sites in lodgepole pine (Pinus contorta), mixed conifer, ponderosa pine (Pinus ponderosa), and pinyon pine/juniper (Pinus edulis/Juniperus sp.) forests 2-6 years after mechanical treatment. Mulching treatments reduced tree density and canopy bulk density, and increased canopy base height, potentially lowing active crown fire risk. In general, mulching increased total woody surface fuel loadings 2-3-fold, but the magnitude differed among forest types. Average total woody surface fuel loads in the untreated areas ranged between 7 and 12Mgha-1, but increased to 27-63Mgha-1 in treated areas. Large diameter fuels (>7.62 cm) represent about 35­69% of the total woody fuel load in the untreated areas, but only about 8-14% of the total fuel load in the treated areas. Woody fuels in treated areas were dominated by material <2.54cm diameter (i.e. 1 and 10 h fuels). In general, mulch fuelbed depth was a useful predictor of fuel loading. Mulching created a compact fuelbed (i.e. bulk density 138-150 kgm-3) that differs from pretreatment needle-dominated fuelbed and will likely change fire behavior and effects. Quantification of the mulched fuelbed characteristics within these four forest types should aid in modification of current fuel models or creation of new fire behavior fuel models.

Keywords

mastication, chipping, fuels management, fuel load equations

Citation

Battaglia, Mike A.; Rocca, Monique E.; Rhoades, Charles C.; Ryan, Michael G. 2010. Surface fuel loadings within mulching treatments in Colorado coniferous forests. Forest Ecology and Management. 260: 1557-1566.
https://www.fs.usda.gov/research/treesearch/37453