Effects of burning moist fuels on seedbed preparation in cutover western larch forests effectsofburning211artl Year: 1978 Figure 5.—Duff reduction related to the water content of the louer half of the duff layer (from Shearer 1975). 50 100 150 200 DUFF MOISTURE CONTENT (PERCENT OVENDRY WEIGHT) At 50 percent water content, the duff layer is mostly burned off, but as the water content increases, a decreasing percentage of the duff layer is consumed. Above 110 percent, however, duff reduction drops to a uniformly low amount. When the results of this study are superimposed on Shearer's curve,
Effects of burning moist fuels on seedbed preparation in cutover western larch forests effectsofburning211artl Year: 1978 Figure 5.—Duff reduction related to the water content of the louer half of the duff layer (from Shearer 1975). 50 100 150 200 DUFF MOISTURE CONTENT (PERCENT OVENDRY WEIGHT) At 50 percent water content, the duff layer is mostly burned off, but as the water content increases, a decreasing percentage of the duff layer is consumed. Above 110 percent, however, duff reduction drops to a uniformly low amount. When the results of this study are superimposed on Shearer's curve, it is not surprising that lower duff water content had no significant correlation to duff consump- tion. In the clearcuts, lower duff water averaged 155 percent, with a range from 71 to 275 percent. The shelterwood averaged 148 percent with a range from 77 to 205 percent. The range of the subblock mean lower duff water contents (140 to 188 percent) is plotted on figure 5 in order to clearly show that the conditions as sampled were outside of the predictive portion of the curve. The unusually high duff moisture resulted from the high precipitation and low temperature on the Coram Experimental Forest during August 1975, the month preceding the fires. During that month there was a total of inches ( cm) of precipita- tion, twice the normal mean, and the average daily maximum temperature was °F (°C), approximately 2°F (°C) below normal. This was the coldest August ever re- corded at the Hungry Horse Dam, and the third wettest since records were started in 1947. Soil Water None of the prescribed fires greatly changed the amount of water within the sur- face 4 inches ( cm) of soil; within the upper inch ( cm), the average was percent before, and was percent after fires. Of the 398 samples taken within the surface inch during the week of burning, 63 percent contained 20 to 30 per- cent water, while 15 percent contained less than 20 percent
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