Fuels Inventory and Appraisal in Intermountain Quaking Aspen (Populus tremuloides) Communities
Field research was conducted in quaking aspen, Populus tremuloides Michx., communities. Fifty-one plots were established in seven major locations in the Bear River Range of northern Utah. The locations inventoried were divided into two age classes: young aspen (under 70 yr) and old aspen (over 70 yr). Custom fuel models were developed for each age class and the data were analyzed for relationships between fuel loads and other measurable factors, including: basal area, average diameter at breast height (d.b.h.), fuel depth, litter loads, tree regeneration, shrub loads, herbaceous loads, slope, tree height, aspect, percent aspen in the plot, grazing intensity, trees infected with disease, elevation, and stand age.
The computer program BEHAVE, fuels inventory data, and the two customized fuel models were used to predict fire behavior, including: flame length, fireline intensity, rate of spread, and heat per unit area.
Young aspen stands and old aspen stands differed significantly for most of the variables studied. The customized fuel models for the young aspen and old aspen also differed, and these fuel models predicted different fire behavior in the two aspen age classes. When fuel loads were compared to the other stand characteristics inventoried for the 51 plots, fuel loads were most strongly correlated with average d.b.h. (P=.005). Fuel loads were also negatively correlated to grazing intensity (P=.024) for the 51 plots. No significant correlations were found between fuel loads and the other variables when analyzed for the seven locations. In general, stand conditions were not-good indicators of fuel loads in aspen communities.
Most important to this study were the differences in the fuel data. When used to develop custom fuel models, the young and old aspen fuel models represented two distinct stand types and predicted different fire behavior. Neither stand type was well represented by Northern Forest Fire Laboratory (NFFL) model 8. The customized fuel models better represent aspen communities in the Bear River Range and should be used by managers for fire behavior predictions.