5th Symposium on Fire and Forest Meteorology and the 2nd International Wildland Fire Ecology and Fire Management Congress

Monday, 17 November 2003
Fire intensity in natural and manipulated fuels during spring buring in mixed shrub woodlands
Tim Bradley, National Park Service, Whiskeytown, CA; and J. Gibson and W. Bunn
The wildland urban interface of Whiskeytown National Recreation Area is characterized by a complex mix of vegetation types that includes mixed oak woodlands, chaparral, mixed conifer, and knobcone pine vegetation types. Just outside of the park, the expansion of homes and other developments is a phenomenon that continues unabated despite the potential that these volatile fuels pose for fast moving intense fires. This imprint of humanity challenges land managers by increasing the level of risk from escapes involved with prescribed fire, which has been a primary tool available for the reduction of fire risk in these fire prone landscapes. Additional challenges include the effects of smoke in an already impacted air basin, and the fact that several applications of prescribed fire may be necessary in order to establish desired fuel conditions.

Within recent years, the park has tested, on a small scale, a variety of alternative fire risk reduction methods, including vegetation chipping and mastication, understory tree or shrub thinning, and biomass removal. These alternative techniques expand the list of options fire managers have for reducing fire risk, yet numerous questions remain about how these treatments alter fire risk through time and what the ecological impacts are as a result.

To assist in answering this uncertainty, a study has been initiated in the park with support funding from the National Fire Plan and the Joint Fire Sciences Program to evaluate impacts to vegetation and soils following varied risk reduction treatments. One component of this study is the quantification of basic fire behavior measures. A total of 36 plots (20 brush masticated and 16 with unmanipulated vegetation) ranging in size from 1/10th to 1/5th acre were burned during the spring of 2003. Within each plot, four monitoring plots were established. Pre and post fire measurements were taken within each monitoring plot for fuels data, including 1 hr, 10 hr, 100 hr, 1000 hr cover; litter and duff depth; and litter type. Fire behavior measures recorded include maximum flame length, flame zone depth, rate of spread, and maximum temperature, recorded by use of temperature sensitive paints at three separate strata (0.5 meters above surface, directly on top of litter surface, and at interface between duff and soil layer) within each monitoring plot.

Initial findings show a large range of variability in fire behavior measures, largely as a function of the diverse surface fuel conditions. Relationships between fuel and environmental conditions will be investigated and reported on to facilitate predictive modeling for both fire control and fire effects. Information and experience gained from this project can be applied to future fire management activities in the park or areas with similar vegetation complexes that are aimed at reducing fire risk while balancing ecological impacts.

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