September 2, 2008
In late May and June 2008, Santa Cruz County experienced two major wildland fires, which impacted more than 5,000 acres. Approximately 70 homes and many other outbuildings were lost, and hundreds of residents (including yours truly) were evacuated as the two fires burned out of control in separate areas of the county. Both fires were apparently caused by human carelessness and spread rapidly due to extremely dry conditions, strong winds, and heavy fuel loads of dense chaparral and knob cone pine. Both fires briefly entered the redwood/Douglas perimeter forests where CalFire was finally able to establish containment and full control.
Central Coast Forest Watch (CCFW) conducted numerous ground investigations of the two burn areas. We also just completed an aerial photographic flyover of the aftermath of the Summit and Martin fires. We are particularly interested in learning more about how redwoods fared in the fire and the impacts of selection logging on fuel loads and fire behavior.
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Because fuel depth and loading play a significant role in fire intensity and rate of spread in redwood forests (Nives 1989) (from the Cal Poly report), Dicus' study was designed to examine fuel loading and potential fire behavior immediately before and after a selective harvest to evaluate the potential fire hazard in the residual stand.
The study site was located in a maritime, Mediterranean climate with cool, rainy winters and dry summers moderated by coastal fog. Most of the forest was 100-year-old second growth. Fuel loads were sampled prior to the September 2002 harvest and again after the selection harvest was completed. Transects were established; 1-hour, 10-hour, 100-hour and larger fuels were sampled and surface fuel, litter, and duff depths were measured.
Potential fire behavior was modeled using BehavePlus fire modeling software. Fuel loading of the 1-hour, 10-hour, and 1000-hour timelag fuel classes as well as litter loading and fuel depth were all significantly higher after the selective harvest. Higher fuel loadings and fuel depths after harvest led to a greater fire behavior in the post-harvest stand. After harvest, both the potential rate of spread and fire intensity increased dramatically, leading to a significantly greater fire hazard.
The report concludes: "...the increased fuel load from harvesting coupled with hot, dry foehn winds, which are not uncommon on the site, could quickly increase fire behavior and subsequent mortality of the residual high-value trees in these stands. Further, home sites adjacent to the study site are presently at an increased risk of wildfire."
CCFW has submitted a grant application for funding to hire a fire ecologist to do a pre- and post-fire vegetation analysis of the Summit Fire to help increase understanding of the spread of fire in our community. Initial observations indicate that chaparral and knob cone pine were the primary fuels in both fires and that the redwood/Douglas-fir conifer forests actually slowed the fire progress and aided fire crews in stopping the wildfires. Redwood areas that suffered extensive heat damage were harvested within the past 20 years. We have seen little evidence of crown fires. If any occurred, they were at the interface with the chaparral areas.
For more information: jodifredi@aol.com.
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TOC for Forest & River News, Summer 2008