Sensitivity Of Fire Behavior Simulations To Fuel Model Variations

Stylized fuel models, or numerical descriptions of fuel arrays, are used as inputs to fire behavior simulation models. These fuel models are often chosen on the basis of generalized fuel descriptions, which are related to field observations. Site-specific observations of fuels or fire behavior in the field are not readily available or necessary for most fire management planning situations. Fuels are thought of in general terms and a single fuel model is often assigned to represent large areas of land. Variations in weather, which can substantially affect fire behavior, are not reflected in the available aids for selecting fuel models. The sensitivity of simulated fire behavior variables to the 13 fire behavior fuel models and two-fuel-model alternatives was analyzed. The two-fuel-model concept demonstrated the effect of combining fuel models on simulated fire behavior results.

In a 1964-1967 study on the Challenge Experimental Forest, seedfall was evaluated in 2-, 5-, and 10-acre circular clearcuttings. During the 4 years, 10 seed crops, ranging from light to bumper, were produced by ponderosa pine. white fir, Douglas-fir, and incense cedar. Seedfall ranged from 76 to 40,691 sound seed per acre (188 to 100,547/ha) for a single species in a given year. From 89 to 100 percent of each species' seed fell within an area 1 1/2 times the height of the average dominant tree. Overall, seed distribution was highly variable.