8S2 JOURNAL OF FORESTRY 



gradual succession takes place as in lodgepole pine in which, however, 

 the tolerant hemlock and cedar become the invaders and the climax 

 forest is a mixed uneven-aged forest composed mostly of western hem- 

 lock and western red cedar. When the pure even-aged forest suffered 

 holocaustic fire at maturity, Hofmann found a succession forest of pure 

 even-aged Douglas fir exactly like the forest that had been destroyed. 



In the yellow pine forest, the same law of succession works as 

 inevitably as it does in the lodgepole pine and Douglas fir forests. The 

 efifect, however, is less apparent to the eye, because the forest, with 

 few exceptions, remains pure yellow pine. In the arid region in which 

 yellow pine occurs, there is to be found no more tolerant species, in 

 fact, no other species whatever, which can compete with it on its site. 

 Thus for the- lack of an invader, yellow pine becomes its own suc- 

 cessor, yellow pine seedlings occupying the places vacated by old trees 

 as they drop out of the stand from time to time. The result is the 

 climax forest of western yellow pine — the many-aged virgin forest of 

 pure yellow pine which is so common in this region. If this forest is 

 now removed at one stroke, an even-aged forest will succeed, just as 

 in the case of Douglas fir and lodgepole. The succession, however, has 

 an entirely different source than that of the compared species. Whereas 

 Douglas fir succeeds through its seed stored in the duff and lodgepole, 

 through its seed stored in serotinous cones, yellow pine succession is 

 effected by the cover of reproduction already established on the forest 

 floor. Yellow pine is but an infrequent seed producer ; and even after 

 a prolific seed crop an adequate cover of reproduction is never a cer- 

 tainty, because the frequent droughts, and late frosts make for but a 

 low rate of survival. The survivals from a number of years of seeding 

 germination and establishment, however, make nearly everywhere in 

 this region an excellent ground cover of advance reproduction — the 

 natural source of the forest which will succeed even-aged when the 

 overwood is removed at one stroke. In this case, the removal obviously 

 cannot be by fire, but must be by cutting alone. And this doubtless 

 explains why over the greater part of the yellow pine region there are 

 so few examples of even-aged stands. 



It is clear from this exposition that natural succession in yellow pine 

 can give rise to both even-aged and uneven-aged forests — the latter 

 being the climax forest. What now does this knowledge indicate with 

 regard to the method of cutting? For one thing, it indicates that the 

 present selection method of the Forest Service has been dictated by 



