THE WESTERN VALLEYS 125 



transient viability. The demands of the species are exacting as 

 to soil and atmospheric moisture, and the temperature range 

 seems normally to lie between -40 and 100 degrees. The trees 

 are very susceptible to disease and are easily killed by fire. 



Thus it will be seen that the negative or limiting factors 

 predominate. Among the positive silvkultural characteristics 

 two only are of much significance as far as competition is con- 

 cerned, viz., the rate of growth and tolerance in early years. 

 These two qualities alone enable the white pine to compete ad- 

 vantageously with all other native forest species and to outstrip 

 many of them in growth. They enable them to enter stands 

 of older trees which are beginning to open as they approach 

 maturity. The importance of these qualities becomes the more 

 apparent when we consider the nature of the species with which 

 the white pine is called upon to compete. The hemlock and 

 grand fir are both very tolerant of shade and may grow in dense 

 stands thougji such are not frequent in this region. The Doug- 

 las spruce, arbor vitae, larch and even lodgepole pine may appear 

 along with the white pine in the same situation and in competition 

 with it. All of the usual competitors except the fir are vigorous 

 producers of seed and hence of special importance in the com- 

 petitive struggle. 



On the whole the white pine can scarcely be said to be for- 

 tunate in its seeding habits. The percentage of germinable 

 seed has been shown to vary, according to the size of the cones, 

 from 15 to 90, but mostly 50 or less. The seeds are sought as 

 food by various animals. Moreover the germination response 

 is slow and the seeds may lie even in well tended nursery beds 

 for a year before germination. It is difficult to see, in the com- 

 plex of influences to which all plants are subject, how any ad- 

 vantage accrues to the tree by such a habit, in view of the fact 

 that such delay may increase the chances for destruction by ani- 

 mals and by decay, and enhance the advantage to other species 

 by increasing their lead in the race. It has also been learned 

 that little seed is produced unless the crowns are well lighted, 

 which indicates that competition is directly responsible for a 

 large reduction in the seed crop. (75.) 



An element of weakness in the white pine is its susceptibility to 

 disease, especially to the attacks of Trametes pini. Whole stands 



