Forest Tvpes and their Relations to Burns 29 



practically all Engelmann Spruce with the exception of a few 

 Alpine Fir. This seems to indicate that the Douglas Fir came in 

 merely as a second temporary type which possibly increased the 

 amount of litter and humus. These conditions aided by a more 

 perfect crown cover which excludes the sunlight, paved the way 

 for the Engelmann Spruce seedlings which later made up the pre- 

 dominating species in the permanent type. The cycle of the 

 burn effect in this type may therefore be stated as follows : 



1. Aspen and Mexican Locust (temporary) 



2. Douglas Fir (temporary) 



3. Engelmann Spruce with some Alpine Fir (permanent). 

 The regeneration which has been described seems to be 



typical in restocking after the usual burn. However, there are 

 a great many exceptions. One area was noticed in a burn in a 

 sub-alpine type where the area was restocking very well with 

 Engelmann Spruce seedlings. The site had been burnt over 

 about seven years previous, and no temporary type of either 

 Aspen or Douglas Fir had come in. This might be accounted for 

 in a measure by the exceptionally moist soil. Another area 

 which had been burnt over 50 or 60 years before, had restocked 

 so heavily with Aspen that all other species were excluded 

 These are exceptions, however, and should not be mistaken for 

 the typical conditions. 



