42 BULLETIN 1200, U. S. DEPARTMENT OF AGRICULTURE. 
This long list of shrubs, trees, and nonwoody plants that compete 
with the Douglas-fir seedlings emphasizes the need of getting a stand 
of young trees started immediately after the forest is removed. 
Nearly all these competitors can endure more shade than Douglas- 
fir seedlings and consequently are able to crowd them out when the 
rapid height growth of Douglas firs—their greatest advantage in 
competing with this ground cover—does not give them the lead. 
The Douglas-fir forests of Oregon and Washington usually have 
an undergrowth of various species of herbs, shrubs, and trees rang- 
ing from sparse to dense. The density of the undergrowth varies 
inversely with the completeness of the stand of Douglas fir. (PI. 
XY.) <A dense stand of young growth of Douglas fir usually suc- 
ceeds in crowding out all competitors. The competition with other 
species is more keen in open areas, and in some places Douglas fir 
is unable to compete successfully with other species and regains the 
area, 1f at all, only by a slow process of invasion. 
In competition one species drives the other back, and the one that 
can best utilize the given combinations of soil, ight, moisture, and 
temperature is the victor. Douglas fir often occupies the south ex- 
posures and the ridges, because it is better adapted to thrive in those 
localities than competing species. Where it does not occur on the 
deep, moist loam soils the competing western red cedar and western 
hemlock have prevented its establishment. 
Where the Douglas-fir forests are delimited from the forests of 
western red cedar and western hemlock it is not because of the in- 
ability of Douglas fir to thrive at the boundaries between the types. 
In a favorable area the species makes no selection as to soil, but 
where conditions are less favorable it is forced by other species to oc- 
cupy those soils to which it is better adapted. The Douglas-fir 
forests continue to crowd the western red cedar and western hem- 
lock largely because of the ability of Douglas fir to establish its 
seedlings during their first season of growth. Its superiority in 
this respect over the western red cedar and western hemlock is due 
to its larger. seed and the greater amount of food stored in the seed, 
which enables the seedling to send down a much deeper root system 
earlier in its life. 
The seeding age of any species is also an important factor in com- 
petition. Nearly all the large areas of chaparral in southwestern 
Oregon are the result of repeated fires. Fires gradually reduced the 
number of seed trees, and although reproduction followed in the 
same manner as in the west coast Douglas-fir region, the succeeding 
fires often destroyed the forest before it reached seeding age. 
The effect of the seeding age on the succeeding forest is clearly 
demonstrated in this region. There are large areas of almost pure 
knobcone pine in places that were formerly occupied by Douglas 
fir and its associated species. The chief reason the knobcone pine 
gained possession of the ground was its age of seed production. 
The knobcone pine produces a sufficient quantity of seed at 10 years 
of age to be a determining factor in the establishment of the type. 
The resistance of the cones to fire protects the seeds through the fire. 
For these reasons, if successive fires should occur at intervals of 10 
or 15 years, the knobcone pine would stand a better chance of sur- 
