Main Articles Listing: Natural Resources 8. Fire Management in the West By Susan McGinley March 25, 2003 A wildfire, whether started by lightning or by human ignition, will burn depending on the available fuel load. Fire ecologists measure this in tons per acre for oak woodland and timber, and in pounds per square foot in grassland. Factors include the amount of brush or wood on the ground, moisture level, slope of a hillside, wind speed and direction, and some educated guesses about how intensely the fire will burn and where it might go. By calculating each fire’s characteristic burn pattern and intensity, natural resource managers and fire fighters have a better idea how to monitor and control them. After the devastating fires that swept Arizona in 2002, this still-evolving strategy has become even more critical. Malcolm Zwolinski, a professor of watershed management at the University of Arizona who has studied the effects of fire for 30 years, said the 2002 Bullock fire near Mt. Lemmon severely burned some areas and left others untouched or only lightly singed. Zwolinski and his colleagues from the School of Renewable Natural Resources in the UA College of Agriculture and Life Sciences are working on fire behavior models based on GIS maps, plus climate and ground information to assist local, state and federal agencies. Scientists from the UA Laboratory of Tree Ring Research and the geography and regional development department are also investigating fire histories, climate changes and fuels’ availability. Fire managers try to anticipate the worst case scenario from the fuel conditions, Zwolinski says. The Roper fire near Sierra Vista was fueled by grasses and other materials that burn rapidly and spread quickly, but don’t generate as much heat as timber fires with tons of fuel. Grassland fires produce less energy than timber fires, and don’t cause as much resource damage. They also are often quite beneficial, burning off dead material and releasing nutrients, such as nitrogen, magnesium, potassium and phosphorus to make them more available to plants. Grasses also regenerate from their unburned roots, green up quickly and provide improved grazing for domestic animals and wildlife.” Periodic grassland fires also control some of the woody shrubs that have invaded grasslands in the Southwest over the past few decades. The impacts of fire are related to how well a plant species is adapted to resist fire, Zwolinski says. “Grasslands do better in general, yet Ponderosa pines can resist fire because they have thick bark and a higher foliar moisture content than other types of trees, such as eucalyptus that burn quickly.” Most cacti species are not tolerant to fire, including saguaros, prickly pear and barrel cactus. Tumbleweeds are very flammable and can spread fires. “We try to use the fire behavior models when we want to suppress a fire, to see where it will go and how hot it will get, based on fuel load. This technique can also be used for a prescribed burn.” Zwolinski shares his fire models with college students and the Southwest Fire Council, that includes federal, state and local land management agencies in Arizona, New Mexico and west Texas. He teaches courses in fire ecology and wildland fire management that draw students from across the university who are interested in the impacts of fire on the environment. He also participates in a national training course on the role of fire in ecosystem management for professional fire fighters. Above all, Zwolinski says Western conifer forests are different from hardwood forests in the eastern United States, and thus require a different management approach. “Western forests have a lot more needle-bearing trees that are susceptible to fire,” he says. Hardwood forests in the East are difficult to burn because the trees have an elevated crown and large surface leaves, so you don’t get the conflagrations that occur in the West. The increased moisture, mainly from snow, causes a more rapid decomposition of debris. Out in the drier West, decomposition is slower. This makes a difference in the fundamental approach agencies take to managing fire in the West. Controversial approaches abound, from complete suppression of fire that led to the problem in the first place, to the clearcutting or logging of old growth forests that won’t solve the problem either, according to Zwolinski. “Mt. Lemmon was reported to be one of the most dangerous areas for fire in the country, and so was Mt. Graham,” Zwolinski says. “The solution to preventing this buildup is thinning the younger trees, not clearcutting, and burning underneath them to reduce fuel load and the danger of fire.” Contact Information Malcolm Zwolinski 520.621-1432 mjz@ag.arizona.edu - Updated: March 25, 2003 [e-Mail me the articles]    -     [Search our articles]    -     [contact us ]     return to media home