Forest 7'v/V.v (///(/ their Relations to Burns 25 



This type is found principally along the stream courses 

 and on the north slopes between the elevations of 7,500 and 

 9.000 feet. It encroaches on the Western Yellow Pine type 

 along the streams, and may be found as low as 7,000 feet on the 

 north slopes of the draws. Typically it occurs in fairly dense 

 stands which often have a density of 0.7 or more but this also 

 depends largely on the soil and moisture conditions. The tole- 

 rance of the species causes a dense stand which creates favor- 

 able conditions for underbrush and unfavorable conditions for 

 grass to a more pronounced degree than in the composite type. 

 Wherever the forest floor is moist, shady and covered with a 

 heavy mat of litter, the underbrush composed of Aspen (Populus 

 treuiuloides ?.Iichx.) and Mexican Locust (Robinia nco-Me.vicana 

 Gray.), is very dense and the grass is almost eliminated. Where- 

 ever fire has not affected it, the reproduction of White Fir and 

 Douglas Fir is very dense in all stages of growth. This forms 

 a very favorable condition for the rapid spreading of fire and 

 compensates for the absence of grass. The poor fire resistance 

 of these species increases the extent and severity of fires in this 

 type. 



White Fir is rendered less fire resistant because it usually 

 becomes infected by a fungus as soon as it reaches the size of 

 standards. In a few years the tree becomes so badly diseased 

 that the leaves fall and the branches die. These dead and dying 

 trees increase the danger of fire from lightning as well as the 

 intensity of fires after they are started. A minor factor, which 

 probably deserves mention, is the presence of a lichen (Usnea 

 sp.) on dead and dying trees as well as on some of the vigor- 

 ous living ones. This lichen burns very readily and may in- 

 crease the destructiveness of fires to individual trees. 



The causes of fires in this type are very much the same as 

 in the composite type. The danger of fire from campers is 

 greater since camp-sites are usually chosen along the stream 

 courses where this type prevails. Frequently campers think they 

 have fully extinguished camp fires which are often still smould- 

 ering. These incipient fires burn into the litter, where a breeze 

 may fan the embers into a flame and cause a forest fire. 



The fighting of fire in this type is made more difficult because 

 of the underbrush and fallen logs. A back fire would probably 

 have to be resorted to more frequently than in the composite 

 type. In addition to rakes and shovels a saw and ax are usually 

 necessary to clear away smaller logs and heavy underbrush when 

 a lane is being made to check the fire. 



