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us
rector, con­
,jJviculture.
xecutive di­
ll K. Halls,
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Contents stages of
Robert E.
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Page
Chapter
FoREST TYPES AND TREATMENTS
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16 .
NoRTHEASTERN SPRUCE-FIR
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.cegas, Olaf
Barton M. Blum, USDA Forest Service ·ntire manu­
Arthur G. Randall, University of Maine (retired) Harold M. Klaiber, Scott Paper Company ) f Asheville,
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David H. Van Lear, Clemson University
NoRTHERN HARDWOODS
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Ralph D. Nyland, State University of New York David A. Marquis, USDA Forest Service Donald K. Whittemore, International Paper Company OAK-HICKORY
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' ........... 23 Ivan L. Sander, USDA Forest Service Clair Merritt, Purdue University E. H. Tryon, West Virginia University (retired)
SoUTHERN BoTToMLAND HARDWOODS
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30 R. W. McGarity, International Paper Company
J. S. McKnight, Consulting Forester
B. G. Blackmon, University of Arkansas (formerly USDA Forest Service)
LoBLOLLY PINE
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37 Ernst V. Brender, USDA Forest Service (retired) Roger P. Belanger, USDA Forest Service Barry F. Malac, Union Camp Corporation LODGEPOLE PINE
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' .... ' ... . . . . . . . . . . . . . . .. . . . ... . . 46 James E. Lotan, USDA Forest Service
P. H. Cochran, USDA Forest Service Joel L. Frykman, Consulting Forester INTERIOR PONDEROSA PINE
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54
Gilbert H. Schubert, USDA Forest Service (retired and now deceased)
Charles A. Wellner, USDA Forest Service (retired )
Russell H. Hudson, St. Regis Paper Company
James W. Barrett, USDA Forest Service
CoASTAL D ouGLAS FIR
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64 James E. King, Weyerhaeuser Company William K. Ferrell, Oregon State University (retired) Dean S. DeBell, USDA Forest Service SITKA SPRUCE-WESTERN HEMLOCK .
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Gerald E. Hoyer, Washington State Department of Natural Resources Alan B. Berg, Oregon Stale University Kenneth N. Wiley, Consulting Forester (retired Weyerhaeuser Company) .
72 l
tA___
___
CHOICES IN SILVICULTURE
Coastal Douglas-Fir 1 n a contest for the world's most important forest tree, Douglas-fir
.l would have to be the United States' entry. It occupies a huge acreage
in the Pacific Northwest and in the Rocky Mountains. In its youth it is a
magnificent Christmas tree. At maturity, it is an outstanding timber spe­
cies. In old age it commands the surrounding forest from a prodigious
height. Southern pine is rapidly overtaking Douglas-fir in markets close
to the source of supply, but southern pine is a trade name representing a
whole complex of species. Douglas-fir stands by itself.
The characteristics and requirements of Douglas-fir growing from the
west slopes of the Cascades to the Pacific Ocean are somewhat different
from those of trees growing in the Rocky Mountains. As a result, two
distinct Douglas-fir forest types are recognized. Only the coastal type is
described here.
Coastal Douglas-fir occupies about 17 million acres in three regions:
the Olympic Peninsula and Coast ranges, the Cascade Mountains, and
the Puget Sound Basin and Willamette Valley. Conditions in this large
area range from very moist and fertile lowlands near the Pacific Coast to
dry and extremely steep slopes in the Cascades. Human populations
range from dense near urban centers to very sparse.
Under the circumstances, no rational plan can be written for a
Douglas-fir stand without knowing where it is. How does one manage a
grove of 300-year-old trees within sight of Portland or Seattle? One does
everything possible to keep the trees alive for the inspiration of thou­
sands of people. How does one manage a similar grove in the wilds of the
Cascade Range? Very possibly one harvests them because they have
reached economic maturity-because they are no longer earning profit
for their owner.
COAS TAL D O UG LAS- F I R FO REST TYPE
Over much of the range of coastal Douglas-fir, winters are wet, but
summers are dry-summer droughts are common. A major use of the
forests, therefore, is for storage of winter rain and snow for summer use.
A tree cover and an ample layer of leaf and needle litter on the forest
floor capture rainwater.
A forest cover also keeps silt from washing into streams. Even small
66
CHOICES IN SILVICULTURE
amounts of silt can destroy the spawning sites for salmon. These fish are
also sensitive to small rises in water temperature. Streams must be pro­
tected when stands are logged, and foresters usually prescribe special
treatments for streamside vegetation.
The original Douglas-fir forest supported substantial populations of
arboreal wildlife including tree-mice, owls, flying squirrels, martens, and
fishers. Logging improved conditions for wildlife adapted to a forest in
which a new stand is succeeding an old one-elk, deer, snowshoe hares,
mountain beavers, black bears, robins, and grouse. As more and more of
the original forest has been convened to young stands of even-aged
Douglas-fir, such early succession wildlife has been provided with plenty
of habitat. But the progressive loss of old-growth habitat has caused
some wildlife species to decline; two such are the bald eagle and the spot­
red owl.
Tree Characteristics
Douglas-fir produces large amounts of seed every 5 to 7 years and
much smaller amounts in the intervening years. Bare soil is required for
satisfactory germination and early survival. Although Douglas-fir trees
can survive for long periods in the shade, they grow fastest in full sun­
light. Timber production, therefore, is greatest when all the trees in a
stand are approximately the same age. As wildlife habitat, an even-aged
stand is low in diversity. Diversity can be increased if the even-aged
stands are in small blocks, and if some snags are left standing. In addi­
tion, development of red alder can be encouraged. This species, which
often grows with Douglas-fir, provides for a number of wildlife species
that do not ordinarily occur in Douglas-fir alone.
The first thing most visitors notice about forests in the Pacific North­
west is the great height of the trees. Heights of over 200 feet are not at all
unusual. Coastal Douglas-fir may take more than 100 years to reach this
stage of maturity. One result is that profitable timber rotations of 100
years are common in the Pacific Northwest.
For bald eagle nesting, a tree must not only be tall, but old, with
heavy limbs. The eagles favor clumps of trees near the shore, but such
nesting sires are becoming rarer each year. Since second-growth Douglas­
firs are normally harvested before they get large enough for eagle
nesting, foresters must make special efforts to provide suitable trees.
Epidemics of Douglas-fir bark beetles can kill the majority of trees
CoASTAL DouGLAS-FIR
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Silvicultural Systems
It is at times better to be lucky than good, and the early harvesters of
Douglas-fir were very lucky. Establishing vigorous new stands probably
did not enter their heads. They clearcut because that was the most con­
venient way to log the giant trees they encountered. Today, millions of
acres of second-growth Douglas-fir demonstrate that clearcutting is an
excellent way to reproduce the species. Poorly stocked acres on certain
sites show that clearcutting will not always work.
Clearcutting with natural seeding is effective with Douglas-fir. Since
seeds are light and have efficient wings, they are carried lo n g distances by
the wind. They will reach all parts of an opening as large as 80 acres if
that opening is designed to take advantage of prevailing winds. Stands
larger than 80 acres are usually harvested in stages over a period of years.
Under this system, a new piece is harvested only after the last piece has
established seedlings. By locating clearcuts appropriately in space and
time, foresters can provide the diverse conditions that favor many types
of wildlife.
Bare soil must be provided for the falling seeds, and the cheapest way
of getting bare soil is by burning. Because very large quantities of tops,
limbs, and rotten wood are usually left when a mature stand of Douglas­
fir is harvested, a burn has two purposes-disposal of logging slash and
seedbed preparation. Snags left for wildlife must be protected from in­
tense flames by clearing an area around them.
Clearcutting is usually most successful on the best sites, but competi­
tion from brush must be controlled. Clearcutting often fails to establish a
good new stand on dry sites and on cold ones that are subject to frost
heaving. Here, some trees should be left standing to shelter the seedlings.
The biggest advantage of natural seeding is that it avoids the cost of
buying and planting nursery-grown seedlings. The only investment is for
slash disposal and seedbed preparation. The big problem is delay. Heavy
seed crops usually occur 3 to 7 years apart, and the crops in intervening
years may be very light. As a result, the time between timber harvest and
establishment of a good new stand may be up to 10 years. During this
period, which foresters call the regeneration lag, grasses and shrubs de­
velop and subsequently compete strongly with young trees for moisture
over large areas. Since these and other bark beetles spend almost their en­
tire lives in the inner bark of trees, insecticide sprays are ineffective
against them. The keys to bark beetle control are to avoid the conditions
under which populations explode and to keep trees healthy so they can
resist attack. Populations of Douglas-fir bark beetles build up in areas
where windstorms have knocked down large numbers of trees. Prompt
salvage after windstorms can help prevent epidemics. Scattered insect­
killed trees provide wildlife habitat and should be left standing.
$
Regeneration lag may be as long as 10 years in the Douglas-fir type.
68
CHOICES IN SILVICULTURE
and nutrients. These conditions favor deer, rabbits, and mountain
beaver, which damage young trees and further delay reestablishment of a
new stand.
Other disadvantages associated with clearcutting include an unattrac­
tive appearance and a lack of site protection until a new stand is estab­
lished. Streams caiJ be guarded by designing roads and skid trails prop­
erly and by leaving strips of timber along the banks. Because streamside
areas are rich wildlife habitats, animals and birds as well as fish benefit
from protection of this vegetation. Appearance can be improved some­
what by shaping harvest areas in an attractive fashion, and by avoiding
clearcutting near major roads. The best way to protect the site, however,
is by getting a new stand established as quickly as possible.
Clearcutting with planting or direct seeding is used on fertile soils.
The cost can often be justified solely on the basis of avoiding a regenera­
tion lag. Planting is also the only way to introduce genetically improved
trees into the forest. These trees grow faster and often are more resistant
to insects and diseases than ordinary stock. Another advantage of plant­
ing is that the distance between trees can be exactly controlled. Irregular
distribution of seedlings is a common problem with natural and artificial
seeding. The costs associated with planting often dictate additional ex­
penditures to protect seedlings from wildlife.
Broadcasting seeds costs far less than planting seedlings, but tech­
niques have not yet been perfected in this forest type. In some spots,
birds and mammals may consume almost all the broadcast seeds. Some
portions of the new stand may be far too dense and others far too open.
The seed-tree system may seem an obvious way to cut huge areas and
still provide for new stands by leaving a few seed trees on each harvested
acre. Early foresters tried this system; they usually left defective trees
that could still produce seed. These seed-trees usually blew over before
they could do their job.
From experience, the seed-tree system simply is not practical in the
coastal Douglas-fir type. Risk of losing seed trees is high, and leaving
anything but the best trees is questionable from the standpoint of genet­
ics. In excellent seed years, trees about I20 feet apart have produced
good stands on experimental areas. Such years tend to come infre­
quently, and in between there is too little seed to do much good. When a
stand does become established, a way must be found to harvest the seed
trees without damaging the new stand.
Limiting the size of clearcuts appears to be more dependable than
relying on seed trees. Small cutting units are also best for wildlife.
On hot, dry slopes at low elevations and on cold sites at elevations
over 1,500 feet, some shade is highly beneficial to newly established
seedlings. The shel!erwood system provides these conditions. It also has
value along roads and streams, where it protects the soil and improves
the appearance of the harvested area. In a shelterwood system it is easy
to leave large snags for wildlife.
It must be emphasized, however, that shelterwood cutting is not
CoASTAL DoUGLAS-FIR
69
necessary to establish good new stands in most of the coastal Douglas-fir
region. Logging is considerably more difficult and costly with this system
than with clearcutting, and the difficulties are compounded by the great
size of mature trees.
Where shelterwood is necessary, a two-cut system is entirely satisfac­
tory. In this system, sufficient trees are removed to provide approxi­
mately half sunlight and half shade on the forest floor. The strongest and
most vigorous trees should be spared in the first cutting. They will pro­
vide the best genes for the new stand, and they are most likely to survive
a windstorm.
A seedbed of bare soil must be provided, and this is no easy task. It
usually must be done with heavy equipment, because a fire in the logging
slash from the first cutting is likely to be so intense that it will kill the
standing trees. Where thorough seedbed preparation is not possible, or
where the seed crop is poor, planting may be needed to get enough seed­
lings established quickly.
As soon as a good stand of Douglas-fir seedlings is firmly rooted, the
remaining mature trees should be harvested. Considerable care is re­
quired to fell and skid these trees without damaging seedlings.
The group selection system of cutting trees in groups that occupy be­
tween 1/4 acre and 5 acres is often an excellent substitute for shelterwood
cutting. Though this practice is not common on public or private hold­
ings at present, it provides room for felling, skidding, slash disposal, and
seedbed preparation. It also gives some shelter to young seedlings. If the
small cuts are carefully located, even wildlife with short home ranges can
be given access to a variety of forest age classes. Forage for big game is
abundant in the small openings.
There are some obvious disadvantages. Logging costs are consider­
ably higher for 2-acre patches than for 20-acre areas. In addition, en­
tirely too much shelter is provided at the edges of small openings, where
the heavy shade favors establishment of western hemlock and true firs
rather than Douglas-fir. Where deer are numerous, potential damage to
seedlings must be considered; browsing is heaviest on the smallest cutting
units. Despite these disadvantages, group selection is becoming increas­
ingly popular, particularly on public lands.
As a method for reproducing Douglas-fir, single-tree selection has lit­
tle to recommend it. Such cutting strongly favors western hemlock and
true firs, and where Douglas-fir seedlings are established, their growth is
poor. Logging costs are prohibitive, and disposal of logging slash is next
to impossible.
Extensive research on single-tree selection was done more than 30
years ago. The results were unmistakable. Cutting of single trees in
mature stands increased the likelihood of death among uncut trees,
primarily from windthrow. There was no increase in growth of uncut
trees to compensate for such mortality.
The system may have some value in recreation areas if the owner is
willing to accept more shade-tolerant species as substitutes for Douglas­
'--"-��""'''
70
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71
COASTAL DOUGLAS-FIR
CHOICES IN SILVICULTURE
fir. It also may have application on very poor sites where stands are very
open. Owners of small tracts sometimes prefer the periodic income and
improved aesthetics associated with single-tree selection. In general,
however, thi system should not be tried in the coastal Douglas-fir type.
Intermediate Cuttings
A typical stand o r seedlings and saplings contains from one thousand
to several thousand trees per acre. A typical stand of mature Douglas-fir
may contain less than 100 trees per acre. What happens to the rest of
these young trees? If not removed in thinnings, they die and decay. One
purpose of thinning, therefore, is to harvest weak trees before they die
and are lost. Another purpose is to concentrate growth on the best trees
in the stand. In this manner, the trees in the final harvest will have the
greatest possible value.
Studies have shown that precommercial thinning-cutting some trees
before they reach salable size-is a wise investment in dense stands of
Douglas-fir. Once the trees reach 8 inches in diameter, they are salable,
and there is no doubt that thinnings at regular intervals until final harvest
will bring profit to the owner.
Even small snags have value for wildlife, and should not be cut dur­
ing thinning. Because thinning increases the amount of sunlight reaching
the understory, it increases shrub growth and fruit production. Black
bears are sometimes troublesome in thinned areas because they are
R EFERENCES
capable of damaging vigorous trees which have reached merchantable
size.
With the long timber rotations generally contemplated for coastal
Douglas-fir, the question is not whether to thin, but how often and how
heavily. Detailed information on the effects of thinning in this forest
type is available.
Fertilizing
Curtis, R. 0., D. L. Reukema, R. R. Silen, R. Fight, and R. M. Romancier.
1974. Exciting possibilities-intensive management of Douglas-fir. Forest In­
dustries. October: 48-50.
Franklin, J. F. 1963. Natural regeneration of Douglas-fir and associated species
using modified clearcutting systems in the Oregon Cascades. USDA Forest
Service, Research Paper PNW-3. Pacific Northwest Forest and Range Experi­
ment Station, Portland, Oregon.
Growth of many Douglas-fir stands has been considerably enhanced
Hooven, E. F. 1973. A wildlife brief for the clearcut logging of Douglas-fir.
benefits continue for 5 to 10 years, and they are sufficient that some
Journal of Forestry 71: 210-214.
Isaac, L. A. and E. J. Dimock II. 1958. Silvical characteristics of Douglas-fir
variety menziesii. USDA Forest Service, Silvical Series 9. Pacific Northwest
Forest and Range Experiment Station, Portland, Oregon.
by applying ! 50 to 200 pounds of nitrogen fertilizer per acre._ The
owners are considering fertilizing every 5 to 10 years after the young
trees' crowns close. Other owners are examining the opportunity of fer­
tilizing 5 to 10 years prior to final harvest, the purpose being to shorten
the length of the investment period.
Miller, R. E. and R. D. Fight. 1979. Fertilizing Douglas-fir forests. USDA Forest
Service, General Technical Report PNW-83. Portland, Oregon.
Reukema, D. L. 1975. Guidelines for precommercial thinning of Douglas-fir.
USDA Forest Service, General Technical Report PNW-30. Pacific Northwest
Forest and Range Experiment Station, Portland, Oregon.
Williamson, R. L. 1973. Results of shelterwood harvesting of Douglas-fir in the
Cascades
of
western
Oregon.
USDA
Forest
Service,
Research
Paper
PNW-161. Pacific Northwest Forest and Range Experiment Station, Port­
land, Oregon.