VALUE AND USE
SPECIES: Tsuga heterophylla | Western Hemlock 



WOOD PRODUCTS VALUE : 
Western hemlock wood is recognized as an all-purpose raw material.  It
is one of the best pulpwoods for paper and paper board products [57,72].
It is the principal source of alpha cellulose fiber used in the
manufacture of rayon, cellophane, and many plastics [10].  Other uses
are lumber for general construction, railway ties, mine timbers, and
marine piling.  The wood is suited also for interior finish, boxes and
crates, kitchen cabinets, flooring, and ceiling, gutter stock, and
veneer for plywood [57,72].


IMPORTANCE TO LIVESTOCK AND WILDLIFE : 
Roosevelt elk and black-tailed deer browse western hemlock in coastal
Oregon, Washington, and British Columbia [57].  In the Oregon Cascades
deer mice consumed about 22 percent of the western hemlock seed fall.
This consumption occurred just before or during the germination process
[76].  Black bear girdle pole-size western hemlock and larger saplings
or damage the bark at the base of the trees.  Snowshoe hare and rabbit
clip off the main stems of western hemlock seedlings.  Mountain beaver
clip the stems and lateral branches of seedlings and girdle the base of
saplings [57].

Old-growth western hemlock stands provide hiding and thermal cover for
many wildlife species.  In the southern Selkirk Mountains of northern
Idaho, northeastern Washington, and adjacent British Columbia, grizzly
bear have been known to use heavily timbered western hemlock forests
[48].  In the western Oregon Cascades, western hemlock provides habitat
for many species of small mammals, including the northern flying
squirrel and red tree vole [7,67]. In Washington and Oregon, the
northern spotted owl is often found in forests dominated by Douglas-fir
(Pseudotsuga menziesii) and western hemlock.  The majority of barred
owls observed in British Columbia have occurred in the Columbia Forest
Biotic Area in which western hemlock and western redcedar are the major
climax species [6].  Western hemlock is used for nest trees by cavity
nesting bird species such as the yellow-bellied sapsucker and northern
three-toed woodpecker [51].


PALATABILITY : 
NO-ENTRY


NUTRITIONAL VALUE : 
NO-ENTRY


COVER VALUE : 
NO-ENTRY


VALUE FOR REHABILITATION OF DISTURBED SITES : 
Western hemlock is suitable for planting on moist, nutrient very poor to
nutrient medium sites in pure or mixed species stands (mainly with
Pacific silver fir [Abies amabilis], Sitka spruce [Picea sitchensis],
alder [Alnus spp.], or western redcedar).  Natural regeneration is
preferred over planted stock [44].  Western hemlock is difficult to grow
in outdoor nurseries.  Container-grown stock appears to result in higher
quality seedlings with less damage to roots and better survival than
bareroot stock [57].  Methods for collecting, storing and planting
western hemlock seeds and seedlings have been detailed [63].


OTHER USES AND VALUES : 
Alaska Indians made coarse bread from the inner bark of western hemlock
[72].  Young western hemlock saplings can be sheared to make excellent
hedges.  In Britain western hemlock is often planted as an ornamental
[46].


MANAGEMENT CONSIDERATIONS : 
Insects and disease:  The major root and butt pathogens of western
hemolock are:  Armillaria mellea, Heterobasidion annosum, Phaeolus
schweinitzii, Laetiporus sulphureus, Inenotus tomentosus, Poria
subacida, Phellinus weiri, and Indian paint fungus (Echinodontium
tinctorium) [30,57].  Western hemlock is severely damaged by Indian
paint fungus in the high Cascades; cull due to this rot may run as high
as 80 percent in old-growth stands [30].  Dwarf mistletoe (Arceuthobium
campylopodum) is a common parasite on western hemlock which causes
wide-spread growth loss and mortality in old-growth stands [62].

Important insects attacking western hemlock are a weevil (Steremnius
carinatus), western larch borer (Tetropium velutinum), western
blackheaded budworm (Acleris gloverana), western hemlock looper
(Lambdina fiscellaria lugubrosa), green striped forest looper
(Melanolophia imitata), saddleback looper (Ectropis crepuscularia), and
hemlock sawfly (Neodiprion tsugae).  The western hemlock looper has
caused more mortality of western hemlock than any other insect pest.
Outbreaks can last 2 to 3 years on any one site.  Although mortality is
greatest in old-growth western hemlock, vigorous 80- to 100-year-old
stands can also be severely damaged by this insect.  The hemlock sawfly
is considered the second most destructive insect of western hemlock in
Alaska [57].

Other damaging agents:  Pole-sized and larger stands of western hemlock
are subject to severe windthrow.  Uprooting is increased in areas where
a high water table or impenetrable layer in the soil causes trees to be
shallow rooted [62].  Blowdown is a major problem in western hemlock
forests, and the need to leave windfirm borders is always present.  If
only part of the stand will be removed, the leave trees need to be as
windfirm as possible [64].

Western hemlock suffers frost damage in the Rocky Mountains, especially
along the eastern edge of its range [57].

On droughty sites, top dieback is common; in exceptionally dry years,
entire stands of western hemlock saplings die [57].  Western hemlock
seedlings and saplings are susceptible to sunscald following exposure of
young stems by thinning.  Sunscald lesions often become infected with
decay organisms [62].

Western hemlock is one of the conifers most sensitive to damage by
sulfur dioxide.

Spring applications of the iso-octyl esters of 2,4-D and 2,4,5-T in
diesel oil can kill up to 3 years of leader growth [57].

Fertilization:  The response of western hemlock to nitrogen fertilizer
is extremely variable.  For overstocked stands, a combination of
precommercial thinning and fertilizer often gives the best response
[57].

Silvicultural considerations:  In terms of biomass production, western
hemlock forests are among the most productive forests in the world.
Natural stands of western hemlock along the Pacific Coast attain higher
yields than Douglas-fir stands having the same site index [57,64].  Pure
stands of western hemlock are so densely stocked that an acre of
100-year-old western hemlock forest can yield more timber (150,000 to
190,000 board feet on a good site) than a comparable stand of larger,
less dense Douglas-fir [10,64].

Western hemlock can be regenerated by most standard harvest methods.  In
the past, clearcutting was the most common method used in western
hemlock stands [64,74].  As an aesthetically viable alternative to
clearcutting, shelterwood cutting has been proposed as a means of
controlling brush competition and favoring western hemlock seedlings
[77].  The shelterwood method has been used successfully in even-aged
stands.  Observations suggest that cutting of uneven-aged stands by the
individual tree selection method will be successful in obtaining western
hemlock regeneration [38,64].  In the grand fir (Abies
grandis)-cedar-hemlock ecosystem, Graham and Smith [34] found that the
individual tree selection method of harvest promotes the regeneration
and growth of shade-tolerant species, such as western hemlock.  The seed
tree method will work, but rarely is used in harvesting of western
hemlock stands because many seed trees blow down during wind storms
[64].

A common problem in regeneration of western hemlock is overtopping by
competing vegetation such as alder, thimbleberry (Rubus parviflorus),
and salmonberry (Ribes spectabilis).  When exposed to full sunlight
after clearcutting, these brush species tend to form dense thickets and
exclude hemlock regeneration.  These species can be controlled with
herbicides [64].

Western hemlock responds well to release after long periods of
suppression.  Advance regeneration up to 4.5 feet (1.4 m) tall appears
to respond better to release than taller individuals.  Poor response to
release has been noted for suppressed trees over 100 years old [57].

Related categories for Species: Tsuga heterophylla | Western Hemlock