Wildland fuel is important to fire managers because it is the one factor that can be directly manipulated to achieve management goals, such as restoring ecosystems, lowering fire intensity, minimizing plant mortality, and reducing erosion. However, managers often find it difficult to measure, describe, and map wildland fuels because of the great variability in the characteristics of fuelbed components. Thus, few have attempted to quantify this variability to understand its effect on fire spread, burning intensity, and ecological effects.
This study investigated the spatial variability of a number of wildland fuel characteristics for the major fuel components found in six common northern Rocky Mountain ecosystems (see map below). Surface fuel characteristics of loading, particle density, bulk density, and mineral content were measured for eight fuel components--four downed dead woody fuel size classes (1, 10, 100, 1000 hr), duff, litter, shrub, and herb--on nested plots located within sampling grids to describe their variability across spatial scales. Canopy bulk density, biomass, and cover were also measured for each plot in the grid.
Results indicated that all fuels had high spatial variability in loading (two to three times the mean), and this variability increased with the size of fuel particle. Fuel components varied at different scales, with fine fuels varying at scales of 1 to 5 m, coarse fuels at 10 to 150 m, and canopy fuels at 100 to 500 m.
Results from this study have profound implications for fire management; high spatial variability that is different across fuel components might render many conventional fuel products and analyses inadequate. Findings and data from this study can be used to map fuel characteristics, such as loading, at finer scales to accommodate the next generation of three dimensional fire behavior prediction models. New fuel classifications can also be developed to describe the variability of fuel across the different sizes and types of fuels in the fuelbed.