is
afforded by hemlock, either practically pure or mixed with white
fir, but probably the most typical is the ordinary Western yellow
pine under certain conditions. At its best this tree composes a
forest so dense that all young growth is shaded out, but everyone
is familiar with the frequent opener stand containing all ages.
The younger trees are often called blackjack.

EVEN-AGED FORESTS

On the other hand, trees extremely intolerant of shade occur only
in what the forester calls even-aged forests. Being unable to start
in the darkness of an existing stand of any considerable density,
they must seize opportunities to recover openings. The Douglas
fir of the Northwest, more commonly called red or yellow fir, is
an excellent illustration. In the interior states this species
reproduces under cover to some extent, because there is a stronger
light average throughout the year and because the stand is not so
dense. In the typical Douglas fir forests of Oregon and Washington,
discussed in this booklet, it never does so. While hemlock, cedar
and white fir undergrowth may be abundant, Douglas fir seedlings
are seldom seen except in burns, slashings, roads, or open spots
in the woods. And the fir trees composing the dominant stand are
of nearly the same age.

How, then, did this even-aged fir forest begin? Close scrutiny
will practically always find the answer in fragments of charred
wood. Long ago another similar forest occupied the ground until
lightning or an Indian's fire started a new cycle. Possibly recurring
burns swept the area many times before wind-blown seeds began to
start advance groups of fir, which, when fifteen or twenty years
old, themselves fruited and filled the blanks between them. Perhaps
destruction was not so complete and surviving trees made the process
a swifter one. Except in the very oldest forests, where remains
of the original stand have entirely rotted away, the history in
either case may be read in ancient snags and fallen logs.

Suppose, however, that fire had not come to aid the fir in perpetuating
itself? This, too, we can answer from the signs today. Every
Northwestern woodsman knows tracts of varying size (usually small
because fire has been almost universal) covered with big old hemlock,
white fir and cedar, with here and there a dying giant fir, perhaps,
but mainly showing fir occupancy only by rotting stumps and logs. No
sign of fire is seen. When this fir forest was approaching midd