Operational Use of Prescribed Fire in Southern California Chaparral
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Operational Use of Prescribed Fire in Abstract: The use of prescribed fire in the 1 chaparral could reduce the incidence and impacts Southern California Chaparral of severe wildfires and enhance watershed re- sources. This paper describes the operational planning needed for a successful prescribed fire Ron Dougherty and Philip J. Riggan2 and discusses the recent experience with this technique on the Cleveland National Forest. Fire is a dominant natural feature in Mediter- PRESCRIBED FIRE OBJECTIVES ranean-type ecosystems throughout the world. With their characteristic summer droughts and highly Fire Hazard Reduction flammable vegetation, these ecosystems are fre- quently coursed by catastrophic wildfires. The use of prescribed fire in chaparral has potential for reducing the occurrence, size, and Nowhere is the threat to human life and prop- impact of large wildfires. Mosaics of different- erty more acute than in the complex association of aged chaparral stands can be produced and main- wildland chaparral and developed urban areas in tained by periodic burning under low to moderate southern California. Here, in November 1980, over fire intensity conditions. These mosaics break up 320 homes were destroyed and 36,000 ha of chap- large areas of heavy fuel accumulation and main- arral watershed were burned by major wildfires tain a substantial area of chaparral in a young, raging under the influence of foehn-type Santa Ana productive state. The occurrence and adverse winds. These were not uncommon events; in modern effects of large wildfires should be reduced since times, homes are destroyed and thousands of hect- fire propagation and resistance to control are ares are burned every year by wildfire. Loss of considerably less in well-stocked young stands life and property can be even greater in the with their low dead fuel volumes (Rothermel and flooding and debris production that often follows Philpot 1973, Philpot 1974). major chaparral fires. Areas of young chaparral have been useful in Fire suppression and prevention programs have the suppression of large wildfires burning under reduced the frequency and size of wildfires, but extreme conditions. In 1979, the 1900-ha Monte this approach alone has not prevented catastrophic Fire in the Angeles National Forest was contained wildfires, and natural fire regimes may have been on the south and west when driven by moderate altered, with profound effects upon this fire- Santa Ana winds into areas burned 4 years pre- adapted ecosystem. In response to these problems, viously by the Mill and Pacoima Fires. Fire efforts are being made to use fire under pre- activity in the young age classes was greatly scribed conditions to manage chaparral fuels and reduced, with only uneven fire spread through provide positive resource benefits. grass and light fuels on the north-facing slopes.3 The southward advance of the 1980 Turner Fire in A program designed to develop and demonstrate and adjacent to the Trabuco District, Cleveland the use of prescribed fire and other management National Forest, was halted under 30 to 50 km/h techniques in the chaparral has been underway winds when it reached an age-class boundary of the since 1977 on the Laguna-Morena Demonstration Area 1975 Tenaja Fire.4 The 1980 Thunder Fire in the in San Diego County. This paper discusses the Mt. Baldy District, Angeles National Forest, rationale for prescribed burning in the chaparral burned southward along San Antonio Canyon under and associated ecosystems, presents an overview of the influence of strong Santa Ana winds. Long the operational planning needed for a successful distance spotting into 27-year-old chaparral on prescribed fire, and discusses our recent experi- the east side of the canyon propagated the fire ence with this technique. and required sustained fire suppression action. Spotting into chaparral burned during the 1975 Village Fire on the west side of the canyon pro- duced only poorly propagating fires that presented little resistance to control.5 While even young stands of chaparral may propagate fire under the 1 Presented at the Symposium on Dynamics and most extreme conditions, both the resistance to Management of Mediterranean-type Ecosystems, June 22-26, 1981, San Diego, California. 3Personal communication from C. Gripp, Angeles 2 Assistant Fire Management Officer, Eldorado National Forest, Flintridge, Calif. National Forest, Placerville, Calif.; Soil Scien- tist, Pacific Southwest Forest and Range Experi- 4Personal communication from M. Stout, ment Station, Forest Service, U.S. Department of Cleveland National Forest, Santa Ana, Calif. Agriculture, Glendora, Calif. 5Personal communication from W. Hite, Angeles National Forest, Glendora, Calif. Gen. Tech. Rep. PSW-58. Berkeley, CA: Pacific Southwest Forest and Range 502 Experiment Station, Forest Service, U.S. Department of Agriculture; 1982. control and potential for mid- and long-range increased in some areas of coastal sage at the spotting are greatly reduced. urban interface. These benefits are particularly valuable at the A large-scale age-class management program wildland-urban interface where a mosaic of natural could be designed to substantially reduce the and planted vegetation often presents extreme fire adverse impacts of high intensity wildfire. hazards. Embers from large chaparral wildfires, Prescribed fires can be conducted under weather such as the highly destructive Stable and Panorama and fuel conditions chosen to minimize fire inten- Fires of 1980, can be carried a considerable sity and planned to encompass specific terrain of distance into the developed community by long- limited area. Cooler fire temperatures reduce range spotting. Carefully applied prescribed nutrient loss (Dunn and DeBano 1977), soil water burning and age-class management in heavy chapar- repellency (DeBano 1981) and erosion (Wells, in ral adjacent to the interface could substantially press), and seed destruction. Prescribed fires reduce this problem. Less is known about the frequently burn only 40 to 70 percent of the value of prescribed burning where the fuels are vegetation within the fire perimeter, thus creat- coastal sage scrub. ing both a diversity of habitat and more nutrient- rich browse that are favorable for wildlife Prescribed fire can also be applied for the (Lillywhite 1977, Bissel and others 1955). The protection of high-value riparian and woodland area burned within major watersheds can also be resources. In stands of California live oak controlled, and this helps to reduce downstream (Quercus agrifolia Nee), substantial mortality in flooding potential. A planned sediment management younger age classes can occur during severe wild- program using prescribed fire on important water- fires, and larger trees can suffer damage to the sheds could be designed to minimize and regulate cambium and lower stem that makes them more sus- debris production. ceptible to disease and insects (Plumb 1980). California black oak (Quercus kelloggii Newb.) is The intensity and effects of a prescribed fire more susceptible and can be largely topkilled in chaparral may necessarily be greater than those during wildfire. Understory prescribed burning associated with prescribed burning in coniferous can be successfully applied in stands of these forests or other woodlands. In conifer forests, species to reduce fuel accumulations (Green 1980) light ground fires with flame lengths less than and provide protection against severe wildfires. 1/2 m could be used to achieve good fuel reduc- Understory burning may also encourage seedling tion. Flame lengths greater than 2 m could well regeneration in areas of heavy litter accumula- be excessive, causing undue damage to tree crowns tion, aid in the control of forest pathogens and boles, and the forest floor. In the chaparral (Parmeter 1977), and mineralize nutrients in the however, flame lengths greater than 2 to 3 m may forest floor litter. be necessary to propagate the fire and attain desired fuel reduction. The amount of soil heat- Serious fire hazard problems also exist in many ing can be acceptable since the duration of heat- of the coniferous forest areas of southern Cali- ing is short and the alternative is burning under fornia. Before 1905, ponderosa (Pinus ponderosa wildfire conditions with possibly extreme fire Laws.) and Jeffrey (Pinus jeffreyi Grev. and effects. Flame lengths in themselves are not here Balf.) pine stands in the San Bernardino Mountains a cause for concern, as they are in forest under- were coursed by low intensity fires at a frequency story burning where canopy damage must be avoided. averaging 10 to 12 years (McBride and Laven 1976). The mature overstory was not readily damaged by these fires, yet fuel accumulations are now large PLANNING THE PRESCRIBED FIRE enough to virtually assure destruction of the mature stand. Prescribed fire can be used suc- Site Selection cessfully to reduce these accumulations, but care must be taken to minimize tree damage and control The selection of sites for prescribed burning the fire. on the National forests is an interdisciplinary process involving professionals from fire, re- source, wildlife, and planning disciplines. Enhancement and Management of Watershed Resources Priorities are determined by the land and resource management objectives specified in the National The application of prescribed fire may provide forest management plan. A prescribed fire may a variety of watershed and wildlife benefits. have one or more major resource objectives related Foremost among