324 Forestry Quarterly 



1.00" in diameter appear immune from windfall, in the fir type 

 this immunity holds for trees over 60" in diameter. The greatest 

 amount by volume occurs throughout the area and by types, in 

 trees between 32" and 40". This diameter class and that from 

 92" to 100" are the most critical periods in respect to windfall, 

 as shown by the greatest per cents of windfall in the standing 

 timber occurring in these classes, except in the fir type, where it 

 is for 32" to 40" and for 52" to 60" that the most cedar windfall 

 occurred. This difference in the fir type is due to the greater 

 protection afforded the cedar by the presence of a greater num- 

 ber of firs about them. The danger of windfall seems little af- 

 fected by exposure or topography, except in the case of very 

 .steep exposed localities where there was windfall in fir ; but tall, 

 dominant trees with well formed crowns are more liable to be 

 windthrown than others; much of the windfall in these other 

 shorter trees and in the trees of smaller diameter classes, occurred 

 where the larger ones have carried them down either by opening 

 up the stand and weakening their hold on the soil, or because of 

 interlacing root systems. 



