Then comes the period of utilizing the main crop. As we propose to keep
the wood lot as such, and desire to reproduce a satisfactory wood crop
in place of the old one, this latter must be cut always with a view to
that reproduction. There are various methods pursued for this purpose
in large forestry operations which are not practicable on small areas,
especially when these are expected to yield only small amounts of
timber, and these little by little as required. It is possible, to be
sure, to cut the entire crop and replant a new one, or else to use the
ax skillfully and bring about a natural reproduction in a few years;
but we want in the present case to lengthen out the period during which
the old crop is cut, and hence must resort to other methods. There are
three methods practicable.
We may clear narrow strips or bands entirely, expecting the neighboring
growth to furnish the seed for covering the strip with a new crop--"the
strip method;" or we can take out single trees here and there, relying
again on an after growth from seed shed by the surrounding trees--the
"selection method;" or, finally, instead of single trees, we may cut
entire groups of trees hero and there in the same manner, the gaps to
be filled, as in the other cases, with a young crop from the seed of
the surrounding trees, and this we may call the "group method."
In _the strip method_, in order to secure sufficient seeding of the
cleared strip, the latter must not be so broad that the seed from the
neighboring growth can not be carried over it by the wind. In order to
get the best results from the carrying power of the wind (as well as to
avoid windfalls when the old growth is suddenly opened on the windward
side) the strips should be located on the side opposite the prevailing
winds. Oaks, beech, hickory, and nut trees in general with heavy seeds
will not seed over any considerable breadth of strip, while with maple
and ash the breadth may be made twice as great as the height of the
timber, and the mother trees with lighter seeds, like spruce and pine,
or birch and elm, maybe able to cover strips of a breadth of 3 or 4 and
even 8 times their height. But such broad strips are hazardous, since
with insufficient seed fall, or fail years in the seed, the strip may
remain exposed to sun and wind for several years without a good cover
and deteriorate. It is safer, therefore, to make the strips no broader
than just the height of the neighboring timber, in which case not only
has the seed better chance of covering the ground, but the soil and
seedlings have more protection from the mother crop. In hilly country
the strips must not be made in the direction of the slope, for the
water would wash out soil and seed.
Every year, then, or from time to time, a new strip is to be cleared
and "regenerated." But if the first strip failed to cover itself
satisfactorily, the operation is stopped, for it would be unwise to
remove the seed trees further by an additional clearing. Accordingly,
this method should be used only where the kinds composing the mother
crop are frequent and abundant seeders and give assurance of reseeding
the strips quickly and successfully.
[Illustration: Fig. 13.--Showing plan of group system in regenerating
a forest crop. 1, 2, 3, 4, successive groups of young timber, 1 being
the oldest, 4 the youngest, 5 old timber; _a_, wind mantle, specially
managed to secure protection.]
The other two methods have greater chances of success in that they
preserve the soil conditions more surely, and there is more assurance
of seeding from the neighboring trees on all sides.
_The selection method_, by which single trees are taken out all over
the forest, is the same as has been practiced by the farmer and
lumberman hitherto, only they have forgotten to look after the young
crop. Millions of seed may fall to the ground and germinate, but
perish from the excessive shade of the mother trees. If we wish to be
successful in establishing a new crop, it will be necessary to be ready
with the ax all the time and give light as needed by the young crop.
The openings made by taking out single trees are so small that there is
great danger of the young crop being lost, or at least impeded in its
development, because it is impracticable to come in time to its relief
with the ax.
The best method, therefore, in all respects, is the "_group method_"
which not only secures continuous soil cover, chances for full seeding,
and more satisfactory light conditions, but requires loss careful
attention, or at least permits more freedom of movement and adaptation
to local conditions (fig. 13).
It is especially adapted to mixed woods, as it permits securing for
each species the most desirable light conditions by making the openings
larger or smaller, according as the species we wish to favor in a
particular group demand more or less shade. Further, when different
species are ripe for regeneration at different times, this plan makes
it possible to take them in hand as needed. Again, we can begin with
one group or we can take in hand several groups simultaneously, as may
be desirable and practicable.
We start our groups of new crop either where a young growth is already
on the ground, enlarging around it, or where old timber has reached
its highest usefulness and should be cut in order that we may not lose
the larger growth which young trees would make; or else we choose a
place which is but poorly stocked, where, if it is not regenerated,
the soil is likely to deteriorate further. The choice is affected
further by the consideration that dry situations should be taken in
hand earlier than those in which the soil and site are more favorable,
and that some species reach maturity and highest use value earlier
than others and should therefore be reproduced earlier. In short, we
begin the regeneration when and where the necessity for it exists, or
where the young crop has the best chance to start most satisfactorily
with the least artificial aid. Of course, advantage should betaken of
the occurrence of seed years, which come at different intervals with
different species.
If we begin with a group of young growth already on the ground, our
plan is to remove gradually the old trees standing over them when no
longer required for shade, and then to cut away the adjoining old
growth and enlarge the opening in successive narrow bands around the
young growth. When the first band has seeded itself satisfactorily, and
the young growth has come to require more light (which may take several
years), we remove another band around it, and thus the regeneration
progresses. Where no young growth already exists, of course the first
opening is made to afford a start, and afterwards the enlargement
follows as occasion requires.