114 Forest Club Annual 



the early growth of the seeding, and later growth of the tree; 

 but the relative difference in light received on various aspects 

 is probably not of sufficient importance to influence the type 

 as determined by soil moisture. For instance, white pine will 

 grow well on south slopes with proper moisture conditions 

 although the white pine type is found on northerly slopes. 



The alpine and yellow pine types are determined usually by 

 altitude, though in a given region soil and slope direction are im- 

 portant local factors. 



FIRE A FACTOR IN TYPE FORMATION. 



Fire plays an important part in the formation of the above 

 mentioned types. The southerly slopes, particularly the south- 

 westerly ones, receiving the sun's rays more nearly perpendicu- 

 larly and for longer periods of time soon become very dry. These 

 exposures are subjected also to the prevailing, heaviest and warm- 

 est winds. Consequently fires sweep over them with great fury, 

 cleaning up everything before them ; but the fires travel slowly 

 down the northern exposure, burning more lightly. The result 

 is that only such thicker barked trees as the Douglas fir and 

 western larch survive on the southerly slopes, the thinner barked 

 trees, especially the western white pine, being killed at once. 

 The resulting reproduction on these slopes is therefore Douglas 

 fir and western larch, so that gradually this mixture becomes the 

 prevailing type. Douglas fir being able to withstand more severe 

 drought conditions than the western larch becomes predominant. 

 Undoubtedly there are many of these southerly slopes which if 

 given protection would grow splendid stands of white pine ; but 

 up to the present time fire has been a great factor in the de- 

 termination of the forest types growing upon them. In the 

 future by proper protection and planting it may be possible to 

 reconstruct the types considerably, so that the best southerly 

 slopes may yield white pine timber, a much more valuable pro- 

 duct than these slopes are at present producing. 



BRIEF DESCRIPTION OF TYPES WITH SPECIES IN MIXTURE. 



The western white pine type is found generally on the 

 northerly and easterly slopes. It contains the following species 

 in mixture western hemlock, lowland fir, western red cedar, and 

 at higher elevations western larch and Douglas fir. The red 

 cedar is usually found along the water courses and at slight 

 elevations above them, and together with western white pine and 

 hemlock form a distinct cover type. Lowland fir and western 



