14 THE AMES FORESTER 



SEED PRODUCTION. 



The production of seed in any type has not been found to be 

 a limiting factor in determining type except in very special and 

 extraordinary cases. Any forest type produces sufficient quantities 

 of seed and at short enough intervals to insure a perpetuation 

 of the type providing other factors are favorable. The variations 

 of seed production may, however, have some bearing on limita- 

 tions of species. Some species, such as hemlock and cedar, 

 produce almost annual crops of seed and thereby provide a con- 

 stant supply of seed and are ready to take advantage of all 

 favorable seasons for establishment while species producing seed 

 at more or less periodical intervals, as western white pine, Doug- 

 las fir, and others may miss favorable seasons of establishment 

 through a lack of seed. 



SEED DISTRIBUTION. 



The distribution of forest tree seeds depends to a great extent 

 on the local conditions, such as topography, wind, rodents, etc. ; 

 and perhaps even to a greater degree on the nature of the seed 

 itself. Heavy seeds as western yellow pine and western white pine 

 are usually carried only a short distance by wind, seldom ex- 

 ceeding 5 to 6 chains, while lighter seeds as western red cedar 

 and western hemlock may be carried farther. 



Where the forest type changes abruptly from a Douglas fir- 

 cedar-hemlock type on the north and east slopes to a yellow 

 pine type on the south and west slopes, as occurs in Idaho and 

 Oregon, the determining factor very clearly is not seed distribu- 

 tion. The location of seed-bearing trees of all these species 

 would insure seed of all species being distributed over large parts 

 of the areas covered by very distinct types, yet some of the species 

 do not appear at all in the stand although the presence of seed is 

 assured. 



SEED GERMINABILITY. 



The foregoing discussion has shown that the presence of seed 

 alone on an area does not insure the appearance of the species 

 nor does this factor alone determine type limitations, however, in 

 this same connection the germinability of the seed is important. 

 When white pine, Douglas fir, hemlock, yellow pine and cedar 

 are in competition the seed of each species may be present at the 

 same time, but the varying periods required for germination, 

 under favorable conditions, give the advantage to the species 

 which germinate quickly, such as hemlock and cedar and may 

 result in the suppression of the dilatory Douglas fir and white 

 pine. In some instances the disadvantages of delayed germina- 

 tion are offset by the ability to overcome competition by faster 

 growth during establishment. This character has enabled the 

 white pine and Douglas fir to be successful competitors of hem- 

 lock and cedar on sites favorable to all of these species. The 



