characteristics contribute to rapid surface spread, 

 and their organic mass requires extensive dig- 

 ging in order to stop or extinguish the deep, 

 slow-burning fires. Drought conditions such as 

 those in 1957 and 1958 may cause extreme dry- 

 ness of moss ground cover to depths of several 

 feet. 



Tundra. — The tundras mark the limit of 

 arborescent vegetation; they consist of black 

 mucky soil with a generally frozen subsoil, but 

 support a dense growth of mosses, lichens, and 

 dwarf turflike herbs and shrubs. The treeless 

 area in the Bering Sea and Arctic littorals is 

 largely covered by tundra. 



Peat and muck. — Peat material can be clas- 

 sified as woody, fibrous, or sedimentary; the 

 type depends upon the degree of decomposition 

 and the method of its accumulation. Muck is any 

 peat material, altered by such features as aera- 

 tion, drainage, or micro-organism action or culti- 

 vation that causes so great a decomposition that 

 its original botanical character is no longer evi- 

 dent. These types are not particularly pertinent 

 to fire control except that they may hold smolder- 

 ing fire for a long time. Quenching a fire in them 

 is extremely difficult because the materials 

 smolder similarly to punk or rotten wood. 



FUEL TYPE CLASSIFICATION 



Formal fuel type mapping or classification 

 has not been done in Interior Alaska. However, 

 through experience and observation of the man- 

 ner in which different types of fuels burn under 

 various conditions of slope and aspect, Robinson 

 prepared a preliminary rate-of-spread classifi- 

 cation for Alaskan fuel types. Table 10 shows 

 generally the relative speed at which fires ignite 

 and burn in the major fuel types. 



Figure 36. — - Tundra type, Steese Highway. 



Table 10. — Rate-of-spread classifications for Alaskan fuel types' 



Fuel type 



Valley bottom 



Benchla 



nd 



Slopes 



Ridgetops 



Wet 



Dry 



Wet 



Dry 



Southerly 



Northerly 



White spruce or 

 birch-spruce 



M 



H 



H 



E 



E 



H 



E 



White birch or 

 birch-aspen 



M 



H 



H 



E 



E 



H 



E 



Black spruce 



H 



E 



H 



E-F 



E-F 



H 



H 



Aspen 



M 



M 



M 



M 



H 



M 



M-H 



Cottonwood 



L 



M 



L 



M 



M 



M 





Willow-alder 



M 



M 



M 



H 



H 



M 



M 



Grass 



E 



F 



F 



F 



F 



F 



F 



Muskeg 



M 



H 



H 



E 



F 



H 



E 



Tundra 



M 



H 



H 



E 



E-F 



H 



E-F 



'Rate of spread: L=low, 



M = medium. 



H = high, 



E = extreme, F = 



flash. 









Based on Bl of 40: 3 m 



p.h. wind; 30 



percent 



relative humidity; 



severity 



index 8; today' 



s slat moisture 



content 6 percent. 



40 



