SUMMARY 



EMC values for some foliar litter, fine forest fuels, such 

 as Douglas-fir needles, were close to that of the NFDRS 

 values for wood for different temperatures and humidi- 

 ties. EMC's of most litter samples, however, are higher 

 than those of wood. For recently cast, adsorption and 

 desorption, these litters can be classified fi"om lowest to 

 highest EMC's into four general groups: grasses, spruce 

 and fir needles, pine and cedar needles, and aspen and 

 larch foliage. At 300 °K (80 °F) the spruce, fir, and pon- 

 derosa pine needles had the lowest EMC's even after hav- 

 ing weathered over winter for 6 months. The rest of the 

 weathered litter groups are, in order fi^om lowest to high- 

 est EMC's, the pines; the grasses, and then larch, aspen, 

 and cedar. 



The EMC's can be estimated by equations that relate 

 the change in moisture content to temperature and hu- 

 midity. This approach uses the relationships given in the 

 Gibbs free energy equations. The estimates are within 

 ±2 percent MC of the observed values for temperatures 

 of 278 to 322 °K and RH's of 10 to 90 percent. Litter 

 EMC's deviate fi-om the EMC for wood enough that sepa- 

 rate calculations for fire danger rating or fire behavior 

 estimates may be required. These equations provide a 

 means for estimating EMC and MC that allows resolution 

 of the differences that exist in fuel types. 



Temperature had a significant effect on EMC. Foliar 

 litters' EMC's were much lower at high temperatures 

 than wood. This may explain the increased flamma- 

 bility of some fuels on hot days or when heated by direct 

 sunlight so the fuel temperature is higher than the air 

 temperature. 



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