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EXCITING POSSIBILITIES
Intensive management of Douglas fir
I
West of the Cascades, the Pacific Northwest contains
crop from insects, animals, and disease. We can harvest
the crop at ages which take advantage of the naturally
the most productive natural coniferous forests on earth.
Since the first settlement, the most i_mportant tree has
high grovvth rates of young stands. Given these, we can
been Douglas fir, a species remarkable for long life, rapid
further increase production over that of the wild forest
f!rowth, relative freedom from insect and disease attack,
by
and utility_ of its wood.
fertility improvement, and
(1) control of spacing and competition, (2) soil
(3)
genetic improvement.
Methods of forestry necessarily differ from those of
\'Ve are no"v in transition from the wild forests of the
past to the managed forests of the future. Our present
agriculture. The long time period required to grow a
forests
forest crop involves much greater biologic and economic
are
a
combination
of
remaining
old-growth
stands, second-growth stands which became established
uncertainties-longer exposure to risks of fire, insects,
in a haphazard manner after past fires or cutting, and
increasing areas of young stands established by planned
and
cutting and regeneration.
nontimber products; and changes in tax systems, tax
levels, and interest rates. The less productive nature of
disease;
changes
in
value
of land, timber, and
individual species; changes in value of timber versus
Despite a very large growing stock, annual production
rates in the wild forests of the past were relatively low.
the land and lower value of the crop mean that cultural
Our new forests are capable of much higher production.
and protective measures must be relatively inexpensive.
Trees are plants, and the means which can be used to
And, wood is only one of the products of the forest.
increase production are basically similar to those used
The choice of measures applicable in a specific situation
with other crops. Intensive culture is really agronomic
depends
forestry. We must be able to get prompt and adequate
recreational, and scenic values as well as on their direct
regeneration of desired species. We must protect the
effects on economic returns from wood production.
-on
their
effects
on
watershed,
wildlife,
By ROBERT 0. CURTIS, DONALD L. REUKEMA, ROY R. SILEN, ROGER FIGHT and ROBERT M. ROMANCIEA*
SINCE COMMERCIAL
duces
immediate
naturally
·been
management
thinning
incomei
one
practices
of
pro·
it
the
has
first
applied
to
The results obtained in such stands do
not represent the potential under
really intensive management.
Intensive culture starts with prompt
complete
existing stands. \Ve have considerable
and
areas of second-gro\vth stands ready
genetically
establishment
desirable
of
reproduction.
for commercial thinning, and a great
Early spacing is controlled through
deal of this is being done.
·
Because most of these
regeneration
practices
and
early
feasible thinning opportunity by the
time commercial size is reached.
think
that
precommercial
We
thinning will usually be most cheaply
and effectively applied as. a single
thinning when trees are small, perhaps
12 to 20 feet in height.
precommercial thinning. Commercial
thinning
haphazard manner,
thinning begins as soon as it can be
quality
\Vithout early control of spacing and
con1petition, they are quite variable in
done at a profit and is continued at
intervals \Vhich permit. forestalling or
plantation
stocking,
salvaging
originated
in
a
species
composition,
and
of
most
mortality
and
for early precornmercial
The need
stands
is
most
sites.
critical
This
is
on
poor
dramatically
illustrated by results of the Wind River
spacing
test
(site
IV).
Average diameters of domin3nt and
ability to respond to thinning. Tree
n1aintenance of adequate crowns \Vhile
codominant
trees.
and stand characteristics gradualiy
beco1ne fixed \vith advancing age; the
avoiding creation of holes which
cannot be quickly occupied by the
planting
initial spacings of 4x4
longer thinning is delayed, the less it
rer.1aining stand. Fertilization is likely
can pron1ote tree development and
to be common practice on sites where
response can be anticipated.
increase usable yields per acre.
There is fairly good information on
results of con11nercial thinning in
previously
stands.
untreated
Such
Douglas
thinning
fir
reduces
Control of initial spacing through
thinnable
gad
vigorous
crowns
cial thinning, or both. \viii usu:illy be
increased gro\ving space. In contrast,
The objective is to
trees at the close spacing had not yet
necessary (fig.
I).
reached
small
net
and
regeneration practices or precommer­
steins. to
that
after
wide spacings were already cominer­
cially
gro\vth,
result
years
12xl2 (fig. 2). Trees grown at the
concentrate gro\vth on re\ativ?ly fev,•
the
41
through I 2xl 2 ft, ranged from 6.0 in.
in the 4x4 spacing to 10.8 in. in the
n ort:ility losses but also reduces total
\Vith
at
produce vigorous. rapidly
able
to
take
advantage of
com111ercial size, and their
crowns
would
make
rapid
production is only slightly increased.
gro\ving: tr.ees \Vith full crO\V!lS \Vhich
\Viii rew;h co111n1ercial thinning size in
response to any present thinning
impossible. Throughout the 41 ·year·
The authors are members of the staff of
the USFS Pacific Northwest Forest and
1ni n i nn11 11 ti1ne. The nun1ber of sterns
rct:iined
should be
sufficicnl
to
ahead in
provide
value.
r:ange Expr!riment Station, Portland. Ore.
48
full
use of
the site and
a
period, the wide spacings have been far
merchantable volume and
FOREST INDUSTRIES/October 1974
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Fig. 1.
Sit e
3. A 40-year-old stand after repeated commercial
thinning to 170 trees per acre, 11 in. average dbh.
Fig.
IV stand after precommercial thinning from
1,300 trees to 400 t r ees per acre.
on
After such initial spacing control,
poorer
sites.
':
\Vhile
that
from
suppression
mortality
and
so
may
commercial thinning· will likely begin
commercial
when stand average diameters reach 8
better sites.
any
stagnation.
roundwood markets develop (fig. 3).
F erti lizati on
mercial thinning and fertilization are
to 10 inches, perhaps less if strong
is
greater
on
generally improved by application of
first; but thinning interval
150 to 200 pounds of nitrogen per
shoul<l lengthen or cuts become lighter
acre, which at present costs about $25.
as the stand grows older, since the
Consistent response to other elements
potential for crown expansion declines
has not been demonstrated.
with age and cutting creates larger
Response
holes in older stands.
reduce
Results
Growth of coastal Douglas fir is
Thinning intervals should probably be
short at
thinning
to
nitrogen
has
been
tendency
from
to\vard
combined
precom­
particularly encouraging and in some
cases
exceed
the
added
tion also insures that the -increased
growth is placed on stems which will
actually be harvested.
production
observed over the full range of site
Genetic improvement
classes, though not in all instances.
Average relative increases in 10-year
cubic-volume growth, with application
The
long-range
possibilities
of
increased production through genetic
improvement is shown by agriculture.
of 200 pounds N per acre (a small
Realization
compared with the normal yield table 1
amount, compared to agricultural use),
forestry is obviously further away than
for
are estima"ted at about 5% on site I,
that from fertilization and thinning of
estimates
well-stocked
stands;
\Vhile
of
untliinned
the
natural
combination
15% on site III, and 25% on site V. On
of
of its full potential in
existing stands.
precommercial and commercial thin­
many experimental plots, short-term
ning will increase total production by
increases in gro\vth have b en much
about 30% (fig. 5). The relative gain
Present programs are of two main
types. The first uses seed orchards
greater than in this (fig. 6). Naturally,
increases are· greatest where nitrogen
intensively selected parent trees and
deficiency is the principal factor limit­
depends
ing growth.
Gains from fertilization of low-site
selection for its gains. The second is
from precom1nercial thinning is greater
1 Richard E. McArdle, Walter H. Meyer, and
Donald Bruce. The Yield of Douglas Fir in
the
Pacific
Northwest.
USDA
Technical
Bulletin No. 201 (Rev. 1961). Reprinted by
Corvallis, Oregon, 1971.
seed from selected trees in the forest.
Here, some gain comes from selection
And,
in
young
stands,
differentiation of crown classes and
but most from progeny testing aimed
at identifying the top quarter of the
•
back to
Under
both
types of program, a
second round of tree improvement has
been started using controlled crosses
from parents in the present progratns.
For commercial seed
production,
so
:c
A study dating
1912 shows this gain to be substantial
and sure if the test is long continued.
•o
:".
...
"
'"
of
absolutely.
70
:c
efficiency
based on collection of wind-pollinated
parentage.
80
on
land are impressive both relatively and
fertilization appears to accelerate both
Oregon State University Book Stores, Inc.,
composed of grafted cuttings from
initially
ungrafted
orchards
•o
progeny
fron1
nre
which
grown
the
in
poorer
three-fourths of the families will be
ren1oved, \vith the ren1:1inder expected
30
D
D
20
.•
.
•
10
u
.:
..
u
N
0
0
Fig.
2
0
10
20
D
•
D
•
•
•
.:
.:
.,
"
0
0
u
CROWN WIDTH (feel)
D
.•
u
·=
D
•
•
0
·=
"
to provide elite set d in 15 to
The
potential
5 years.
it11provc1nen t
in
volume growth has bc n conservatively
estin1atcd at 10 1 fur the first roun d ,
and
at
least
another
I O(,:h
\vht:n
progeny fron1 kno\Vll crosses beco111es
available as a seed source. ()ther gains
come
fron1
such
I
i
I
i
f
effects of
either treatment alone. TI1is cotnbina­
attainable on limited uniform areas
suggest that on site III commercial
thinning alone will produce about a
5% gain in production over a rotation,
Current
'
characteristics·
as
49
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l
GROSS
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and
fertilization
1n 1y
give
highest
returns on those sites \\'hich arc poor
because of nutrient deficiencies.
Further and 1najor li1nitations are
o
itnposcd by conflicts \Vith uses other
NET
than
ti1nbcr
obvious
and
diversion
production. The
itnpor. tant
of
land
1nost
of these is
to
nonthnber
producing uses. As of 1970, about 6%
of the con1111ercial forestland in the
I
Douglas
reserved
Unadjusted means:
• Gross
timates are that by the year 2000
another 7% of the present conin1ercial
o Net
Fig.4
fir region \Vas in various
classifications. Present es­
1000
forestland
Fig.5
"
0 '----'----'
0
improved bole
improved wood traits, and
possibly
improved
responsiveness to
change
real
from
population.
risks
the
In a
genetic
adapted
natural
which must
have
been
lost
to
\Vithout
tional
po\verlines, etc.,
considering possible addi­
reserved.
areas
such
as
Wilderness. Much of the land so lost
will be of high site quality.
We are all acutely aware of the
importance of forest values other than
Intensified management is usually
in
crop
420
than in many other species.
intensive culture techniques.
are
280
NITROGEN (po..inds per acre)
form, hardiness and
survival,
There
140
will
urbanization, roads
associated
with
shorter
rotations.
timber, and that neither
maximum
timber
maximum
production
nor
Calculations of present net worth for
direct financial returns are necessarily
newly
the controlling criteria. Rather, we
established
stands
suggest
withstand all climatic extremes and
highest stumpage returns for rotations
need to maxllnize returns from some
pest attacks for 50 years or more, the
in
combination of values including social
the
range
of
30
to
60 years,
only safety lies in a very diverse pool
according to site, interest rate, and
of genetic types, so that loss of a single
values that are not readily measured in
utilization assumptions. The regenera­
type represent; only a small fraction
dollars.
tion stage is a period when things can
Another point is partly social and
of
go badly wrong. On some areas there is
applies particularly to clearcut areas.
locality is very sensitive in Douglas fir,
real
local trees are used for the breeding
delays, possible loss of the site to
In general, an area looks devastated to
the general public for IO years after
population. Another safeguard is the
brush
extremely
populations
severe animal damage to regeneration.
"cutover." From there on, it looks
which preserve the entire gene pool of
Long rotations postpone these prob­
beautiful. If we operate on a 40-year
the locality.
lems.
rotation, \Ve \Viii always have 25% of
the
stand.
Since
large
adaptation to
base
growth
rates
which
of
or
extended
less
regeneration
desirable
species, or
There is the possibility that very
Factors limiting intensive culture
The
risk
close
are
utilization
rotations
might
on
lead
the area looking devastated. With an
short
80-year rotation, the 25% figure is
seriously
halved. This is one of several factors
very
to
harvest. For the next IO years it looks
on small areas
reduced site productivity, unless we
which may lead to increased use of the
under ideal conditions can never be
are prepared to apply fertilization and
shelterwood harvest
attained in .management of large areas.
soil management practices con1parable
future.
Rates actually attainable are restricted
to those in agriculture.
biologically
possible
system
in
the
We have not treated economics as a
economic
Regeneration is not instantaneous,
separate topic. Economic considera­
factors; and \Vithin the framework of
not uniform, and not always of desired
tions and decisions are an integral part
biological
species.
by
both
biological
and
possibilities,
economic
factors largely determine what we can
actually do.
In
wild
stands,
a
considerable
fraction of gro\vth is lost to insects
Sometimes \Ve can't get it.
Irregular distribution and poor species
of
all intensive culture plans. We must
use our economics tools at every stage
control may give young stands \vhich
to evaluate options and help select the
cannot
best alternatives, although economic
gain will be only one of the
be
molded
into
efficient
producers. Harvest cutting and slash
and diseases. Intensified management
disposal practices can have a lasting
considerations that the land manager
will reduce but not eliminate losses,
and we can expect that the relative
effect
must weigh.
through
their
influence
on
One last thought. We tend to think
regeneration.
ilnportance of pests will change.
Compared \vith such species as the
Site and topographic limitations
southern pines, Doug1as fir is a slow
starter.
However,
juvenile
stage,
capacity
for
it
once
has
the
intensive management, and no doubt
many of then1 are today. But our ideas
be applied first and most
of forestry and our econo1nic situation
intensively on the best sites and \Vill
have changed radically in the last 30
generally
gro\vth over
there produce highest returns. By and
years, and no doubt they will continue
long periods of tin1e. fi..1axin1un1 mean
large this is certainly correct, but it
to change in the next 30. We might
annual incren1cnt is attained relatively
docs not necessJrily apply equaUy to
remember that even site IV Douglas fir
late. l'he decline thereafter is slow,
all
\Vil! out-produce almost anything in
and
biologically
n1ercial thinning 1nay give large returns
North America easi of the Rot:kies and
is 1nuch wider
on poorer sites prone to stagnation,
north of the southern pine region.
the
reasonable
50
sustained
past
a remarkable
It is a truism that 1nanagement \vill
of our lo\ver site lands as unsuited to
range
rotations
of
practices.
For exa1nple, prccon1­
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FOREST INDUSTRIES/October 1974