le
age, the shade bearing species began to appear beneath it. As the
firs began to crowd themselves out, the later comers shot up with
the increased light and filled the open places. At last the even-aged
fir forest was completely transformed into a selection forest of
other trees, which will remain until some accident again gives
fir a chance if any survives near enough to reach the spot with
seed.

Douglas fir is not the only Western tree which usually grows in
even-aged stands. Lodgepole pine has the same habit, often supplanting
yellow pine after fire or logging. Western white pine is perhaps more
tolerant than Douglas fir, hence more likely to hold its own without
artificial aid, but is also more certain to compete successfully
if it has such aid. The same is true of tamarack.

NATURE AS A MODEL

We thus see that if economic reasons suggest it, we may use the
selection system as a basis for artificially managing the shade
bearing species such as hemlock, white fir, cedar, spruce, and even
Western yellow pine. We may cut the largest and oldest trees and
still have a well started second crop. If there is not much young
growth to leave, even a little is valuable. It may be decidedly
best to leave medium sized trees, which otherwise we would cut,
because they are still growing rapidly.

On the other hand, we see that this method would not be of any
advantage at all in insuring a second crop of Douglas fir, for
there is no young growth of this species to protect. The small and
medium sized trees, instead of being immature, are merely stunted
specimens of the same age as their larger brothers and unlikely
to gain in size if left. Selection cutting here would save for
future use only such understory of shade-bearing species as may
exist. Unless this is an object, the best plan is to cut clean and
get all we can. If we leave any fir at all it is for the purpose of
reseeding, not to secure better utilization of the trees themselves,
and whether we do so depends, theoretically at least, upon whether it
is better than artificial seeding or planting. In short, selection
cutting harvests the ripest trees of a perpetual forest, while
clean cutting destroys the forest in order to start an entirely
new and more rapid growing one.

Clean cutting is therefore necessary as well as natural in dealing
with intolerant trees. But it does not follow that the selection
system, although natural to tolerant species, is the only one a