Pacific Southwest Research Station

Balancing Fuel Reduction, Soil Exposure, and Erosion Potential

Researchers from Humboldt State University and the Forest Service Pacific Southwest Research Station are quantifying relationships between fuel reduction and erosion potential by evaluating the relationship between fine scale fuel moisture variation and patterns of soil exposure with prescribed burning. Erosion will then be tested among treatments by changing the proportion of soil covered by masticated and natural fuels, using simulated rainfall.

Proposal [pdf]

Lead Researchers: Andrew P. Stubblefield and J. Morgan Varner, Humboldt State University; Eric Knapp, USFS Pacific Southwest Research Station; Mark Grismer, UC Davis

1. Determine optimal levels of surface fuel retention with mechanical mastication and prescribed fire treatments that maximize goals of reducing fire hazard/severity while minimizing the threat of erosion and sedimentation.
2. Understand mechanisms by which burn patchiness (including sediment capture in islands of unburned fuel) can be created even under the current high fuel loading and fuel continuity in Tahoe Basin forests by linking fuel moisture with timing of prescribed fire and the pattern of the resulting burn.

Sampling Sites and Methods:

• Eight burn sites (2008-2009 prescribed fires or wildfires) and eight mastication sites (within past 1 to 2 years) within the basin.
• Intensively characterize forest floor fuels in all prescribed fire units and stands burned by wildfire along 50+ m linear transects following hillslope contours.
• Identify plots for runoff simulation:
• Fire treatment sites will be placed at locations where fire has exposed bare soil over 0-25, 25-50, 50-75 and 75-100 percent of a plot
• Mastication treatment sites will include a eight treatments representing different fuel loads and patchiness

Timeframe: August 2008 through June 2011 (3 years)

Products:

1. Workshop with Lake Tahoe basin resource managers regarding balancing fuels, restoration, and erosion potential in the Lake Tahoe basin, including field tour and presentations
2. Workshop or symposium at a national meeting linking fire severity and erosion potential
3. Management summary regarding fuel treatment prescriptions for balancing fuel reduction, soil exposure, and potential for erosion in the Tahoe basin
4. Project Web site on balancing wildfire risk and erosion risk in the Sierra-Nevada
5. Manuscript on burn heterogeneity in prescribed fires linking season, forest floor composition, and moisture content variation
6. Manuscript on developing fuel treatments for balancing fuel reduction, soil exposure, and potential for erosion in the Tahoe basin
7. Manuscript on consequences of fire and fuels treatments for erosion in the Tahoe basin