In addition, the influence of the prescribed fires on soil heating, soil water con- 

 tent, and root mortality of nonconifers was estimated. These data provided an estimate 

 of the amount of mineral soil exposed and a forecast of early vegetative competition. 



LITERATURE 



Research on duff consumption has been related to either duff water or to indices 

 of fire danger or drought (Artley 1976) . Because measurements of physical parameters 

 (such as duff water content) enhance consistent interpretation over time, and decrease 

 the chance of interpretive error, they are probably more useful in describing duff 

 consumption. 



Duff moisture has repeatedly been used in research describing and predicting duff 

 reduction by fire. Early investigations related duff reduction to a subjective esti- 

 mate of duff moisture content (Sweeny and Biswell 1961; Morris 1966). Later attempts 

 explained duff consumption by precisely measuring the variables thought to be the most 

 important contributors. For example. Hough (1968) and Steele and Beaufait (1969) deter- 

 mined that measurements of the moisture content of the litter, the duff, and the woody 

 fuel, all were useful in predicting duff reduction. More recently, emphasis had shifted 

 to the use of multivariate regression analysis and correlation analysis in order to 

 formulate prediction equations for duff reduction. Van Wagner (1972) found that the 

 best predictor of duff weight consumed by fire in eastern pine stands is duff moisture 

 content and is more closely related to duff consumption than measurements of actual 

 fire behavior. 



Similar results have been reported from prescribed fire studies in three different 

 areas within western larch forests of northwestern Montana. Duff consumption is lin- 

 early related to the moisture content of the lower half of the duff when it is between 

 the range of approximately 40 to 110 percent (Shearer 1975). Steele (1975) attributed 

 duff consumption to preburn duff depth, duff moisture content, and the weight of the 

 woody shrubs. Norum (1975, 1977) concluded that duff reduction was dependent on the 

 factors above the duff which most influenced fire intensity and persistence, in addi- 

 tion to the moisture content of the lower duff. Van Wagner (1965) also found that 

 mineral soil exposure increased as fire intensity increased. Similarly, Beaufait and 

 others (1977) showed a strong relationship between the water loss from a water can 

 analog (Beaufait 1966; George 1969) and duff consumption. In addition, they concluded 

 that duff reduction by fire was a function of the moisture content of the upper half of 

 the duff. 



STUDY AREA AND TREATMENT 



The study was conducted on the 7,460 acre (3,019 ha) Coram Experimental Forest, 

 on the Flathead National Forest, in northwestern Montana (fig. 1). The study sites 

 are located below the main ridge facing east into Abbot Basin (lat. 48° 25' N. , long. 

 113° 59' W.). Six blocks, consisting of two clearcuts (14 and 17 acres; 5.7 and 6.9 ha), 

 two shelterwoods (35 and 22 acres; 14.2 and 8.9 ha), and two sets of eight small clear- 

 cuts (average 0.8 acre; 0.3 ha, range from 0.3 to 1.4 acres; 0.1 and 0.6 ha), were 



2 



