Abies amabilis

Pinaceae -- Pine family

    Peggy D. Crawford and Chadwick Dearing Oliver

    Pacific silver fir (Abies amabilis), also known as silver fir  and Cascades fir, has a gray trunk, a rigid, symmetrical crown, and  lateral branches perpendicular to the stem. It contrasts strikingly with  the more limber crowns, acute branch angles, and generally darker trunks  of its common associates Douglas-fir (Pseudotsuga menziesii), western  hemlock (Tsuga heterophylla), and mountain hemlock (T.   mertensiana). The species name, amabilis, means lovely.

General: Pine Family (Pinaceae). Pacific silver fir is a U.S. native conifer that ranges from 100 to 230 feet tall and up to 45 inches in diameter at the base. Like all true firs, it has erect, cylindrical cones that are borne near the tips of the uppermost branches. Secondary branches and twigs are typically in pairs, with leaves twisted or curved so that they tend to lie in one plane. Mature cones are 3.5 to 6 inches long and purple. Mature trees are erect, conical in outline, with spreading, spray-like branches and a scaly, gray to whitish bark. Young shoots have a dense, short, pinkish brown pubescence. Most of the needle-like leaves range from 0.5 to 1.3 inches long, are bright green, somewhat flattened, and have notched tips.

Distribution: For current distribution, please consult the Plant Profile page for this species on the PLANTS Web site.

Pacific silver fir occurs from extreme southeastern Alaska south through
western British Columbia, the Cascade Range of Washington and Oregon, to
northwestern California [6,7,51,55,60]. Pacific silver fir is also
found in the Olympic Mountains of Washington [6,7,38].

More info on this topic.

This species can be found in the following regions of the western United States (according to the Bureau of Land Management classification of Physiographic Regions of the western United States):

1 Northern Pacific Border
2 Cascade Mountains
4 Sierra Mountains

AK CA OR WA BC

Pacific silver fir is found in southeastern Alaska, in coastal British  Columbia and Vancouver Island, and along the western and upper eastern  slopes of the Cascade Range in Washington and Oregon. It also grows  throughout the Olympic Mountains and sporadically in the Coast Ranges of  Washington and northern Oregon. Near Crater Lake, OR, Pacific silver fir  disappears from the Cascade Range and then reappears at a few locations in  the Klamath Mountains of northwestern California. The major portion of its  range lies between latitudes 43° and 55° N. (35).

     
- The native range of Pacific silver fir.

Abies amabilis Douglas ex J. Forbes:
Canada (North America)
United States (North America)

Note: This information is based on publications available through Tropicos and may not represent the entire distribution. Tropicos does not categorize distributions as native or non-native.

Canada

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

United States

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

Global Range: Southern Southeast Alaska to northwestern California.

Native to the Pacific Northwest, Pacific silver fir ranges from southern Alaska to northern California. Well developed stands are primarily found at elevations from 1,000 to 7,000 feet on the coastal slopes of the Cascades. However, in the northern part of its range, stands occur well below 1,000 feet. Pacific silver fir usually occurs in uniform stands or associated with western hemlock (Tsuga heterophylla). The geographic range is characterized by a maritime to submaritime climate, with an annual precipitation between 40 to 260 inches per year, and average summer temperatures between 57 to 59 degrees F. Plants have a mild frost tolerance and a low tolerance for frozen soil conditions. Soils are usually very moist, somewhat acidic (pH 5), and rich in magnesium and calcium. A thin bark and highly flammable foliage contribute to low levels of resistance to fire.

Trees to 75m; trunk to 2.6m diam.; crown spirelike, with age becoming flat topped, cylindric. Bark gray, thin, smooth, with age breaking into scaly plates. Branches diverging from trunk at right angles, short, stiff; twigs mostly opposite, darker brown abaxially, light brown adaxially, pubescence tan. Buds hidden by leaves or exposed, brown, globose, small, resinous (at least apically), apex rounded; basal scales short, broad, triangular, densely pubescent, usually not resinous, margins entire, apex sharp-pointed. Leaves (0.7--)1--2.5cm ´ 1--3mm, mostly 2-ranked, flexible, ± concealing the adaxial surface of the twigs (especially in mid to upper crown), some leaves forwardly directed, others usually longer and spreading horizontally, proximal portion ± straight; cross section flat, prominently grooved adaxially; odor pungent; abaxial surface with 5--6 stomatal rows on each side of midrib; adaxial surface dark, lustrous green, lacking stomates; apex prominently notched; resin canals small, near margins and abaxial epidermal layer. Pollen cones at pollination red, becoming reddish yellow. Seed cones cylindric, 8--10(--13) ´ 3.5--5cm, purple, sessile, apex round to nipple-shaped; scales ca. 2 ´ 2cm, pubescent; bracts included. Seeds 10--12 ´ 4mm, body tan; wing about as long as body, rose to tan; cotyledons 4--7.

More info for the term: monoecious

Pacific silver fir is a monoecious, long-lived, native conifer
[14,24,38,66,68]. At maturity, it can reach heights of 100 to 230 feet
(30-70 m) and diameters of 36 to 44 inches (90-110 cm) [24,26,38]. The
average maximum age for Pacific silver fir is 400 to 500 years on good
sites, and 250 to 350 years on more adverse sites. The maximum recorded
age is 540 years [14,59]. As Pacific silver fir becomes older, growth
is commonly deformed [57]. The crown is rigid and symmetrical with
lateral branches perpendicular to the stem [14]. Young trees have
resin-filled blisters protruding from the smooth, thin bark. The bark
of older trees is rough textured and flaky [6].

The needles grow from opposite sides of the branch, spreading
horizontally or brushed forward. The top is flat, grooved, and
"lustrous green", and the underside is stomatiferous and silvery white
[6,38]. Pacific silver fir has a second type of foliage on the
uppermost, cone-bearing branches. These needles are very sharp and
curved. The cones are stiffly erect, barrel shaped, and 3.5 to 6 inches
(8.9-15.2 cm) long [6].

Tree, Evergreen, Monoecious, Habit erect, Trees without or rarely having knees, Primary plant stem smooth, Tree with bark smooth, Tree with bark rough or scaly, Young shoots 3-dimensional, Buds resinous, Leaves needle-like, Leaves alternate, Needle-like leaf margins entire (use magnification), Leaf apex mucronulate, Leaves < 5 cm long, Leaves < 10 cm long, Leaves not blue-green, Leaves white-striped, Needle-like leaves flat, Needle-like leaves not twisted, Needle-like leaf habit erect, Needle-like leaf habit drooping, Needle-like leaves per fascicle mostly 1, Needle-like leaf sheath early deciduous, Needle-like leaf sheath persistent, Twigs pubescent, Twigs not viscid, Twigs without peg-like projections or large fascicles after needles fall, Berry-like cones orange, Woody seed cones > 5 cm long, Bracts of seed cone included, Seeds tan, Seeds winged, Seeds unequally winged, Seed wings prominent, Seed wings narrower than body, Seed wings equal to or broader than body.

More info for the terms: fern, shrub, vine

The climate throughout the range of Pacific silver fir is maritime to
submaritime [14,41]. Pacific silver fir is usually submontane to
subalpine [27,41]. It thrives in areas that receive a great deal of
precipitation. Average annual precipitation ranges between 38 and 262
inches (965-6650 mm), mostly in the form of snow [14,22,27,42]. The
average winter temperature is 26 to 29.8 degrees Fahrenheit (-3.2 to
-1.7 deg C), and the average summer temperature is 57.2 to 58.8 degrees
Fahrenheit (14-14.9 deg C) [14,71]. Pacific silver fir is absent in
coastal areas with dry summers [59]. There is a correlation between
growth, snow-free period, days above a certain temperature, absence of
frost pockets, and preferable sites for Pacific silver fir [32].
Pacific silver fir has a mild frost tolerance and poor frozen soil
tolerance because of its need for water during the winter [22,51].

Pacific silver fir is an indicator of very moist soils. It occurs on
soils in the orders Alfisols, Entisols, Inceptisols, Histosols, and
Spodosols [51,67]. Soil parent materials include basalt, glacial till,
volcanic ash, pumice, and sedimentary rock [31,51,52]. Pacific silver
fir can grow where the water table is near the surface during the
growing season if the soil is well aerated, thick, and/or with wood
accumulations on top of the mineral soil [59]. Growth is successful
with thick humus present [59]. Soils are generally shallow, but soil
depth varies from 1.2 to 12 inches (3-30 cm) [27]. Soils are acidic in
the rooting zone (pH 5) [41]. Whatever the soil type, an adequate,
year-round water supply is very important. Often nitrogen and
occassionally sulfur are limiting elements in soils [32]. Soils rich in
magnesium and calcium indicate good sites for Pacific silver fir [42].

The elevation at which Pacific silver fir grows is quite variable. It
is more common at higher elevations but grows faster at lower elevations
[59]. Pacific silver fir occurs at a maximum of 7,000 feet (2,120 m) in
the southern part of its range and at a maximum of 1,000 feet (330 m) in
the northern part of its range [14,22,24,27,51].

Overstory associates not mentioned in Distribution and Occurrence
include noble fir (Abies procera), Alaska cedar (Chamaecyparis
nootkatensis), Shasta red fir (Abies magnifica var. shastensis), and
western larch (Larix occidentalis) [9.14,27,51,60]. Shrub understory
includes huckleberry (Vaccinium spp.), Cascades azalea (Rhododendron
albiflorum), devils club (Oplopanax horridum), copper bush (Cladothanus
pyrolaeflorus), rustyleaf menziesia (Menziesia ferruginea), salal
(Gaultheria shallon), vine maple (Acer circatum), and Oregon-grape
(Berberis nervosa) [9,12,15,28,52]. Herbaceous species are beargrass
(Xerophyllum tenax), bunchberry (Cornus canadensis), twinflower (Linnea
borealis), queenscup beadlily (Clintonia uniflora), dwarf blackberry
(Rubus lasiococcus), rosy twistedstalk (Streptopus roseus), coolwort
foamflower (Tiarella unifoliata), deer fern (Blechnum spicant),
salmonberry (Rubus spectabilis), vanillaleaf (Achlys spp.), and
evergreen violet (Viola sempervirens) [9,12,14,28,52].

More info for the terms: association, climax, codominant

Pacific silver fir commonly occurs in late seral or climax mixed-conifer
stands [52]. Throughout its range the most commonly associated conifer
is western hemlock (Tsuga heterophylla). Pacific silver fir also
reportedly grows in extensive pure stands in parts of the southern
Washington Cascade Range [14]. Below are publications in which Pacific
silver fir is listed as a dominant or codominant species:

Preliminary plant associations of the southern Oregon Cascade Province [9]
Preliminary classification of forest communities in the central portion
of the western Cascades in Oregon [16]
Forest communities of Mount Rainier National Park [28]
Plant association of Mount Hood and Willamette National Forests of Oregon [35]
Forest communities of northern California [55]
Plant associations for the western hemlock zone [64]
Preliminary classification systems for the vegetation of Alaska [68].

More info on this topic.

This species is known to occur in the following ecosystem types (as named by the U.S. Forest Service in their Forest and Range Ecosystem [FRES] Type classification):

FRES20 Douglas-fir
FRES22 Western white pine
FRES23 Fir - spruce
FRES24 Hemlock - Sitka spruce

More info on this topic.

This species is known to occur in association with the following cover types (as classified by the Society of American Foresters):

205 Mountain hemlock
206 Engelmann spruce - subalpine fir
213 Grand fir
215 Western white pine
221 Red alder
223 Sitka spruce
224 Western hemlock
225 Western hemlock - Sitka spruce
226 Coastal true fir - hemlock
227 Western redcedar - western hemlock
228 Western redcedar
229 Pacific Douglas-fir
230 Douglas-fir - western hemlock

More info on this topic.

This species is known to occur in association with the following plant community types (as classified by Küchler 1964):

K001 Spruce - cedar - hemlock forest
K002 Cedar - hemlock - Douglas-fir forest
K003 Silver fir - Douglas-fir forest
K004 Fir - hemlock forest
K005 Mixed conifer forest
K012 Douglas-fir forest
K013 Cedar - hemlock - pine forest
K014 Grand fir - Douglas-fir forest
K015 Western spruce - fir forest

Pacific silver fir grows on soils developed from nearly every type of  parent material found in the Northwest. Layering in soil profiles caused  by successive deposits of volcanic ejecta, colluvium, or glacial till is  especially common (1,43). The greatest known growth rates for Pacific  silver fir occur at low elevations on fine-textured residual soils from  sedimentary and basaltic rocks (16). Growth is reduced on poorly drained  or shallow rocky soils.

    In northern Washington and British Columbia, podzolization is the  dominant process in well-drained soils under Pacific silver fir. A typical  podzol is characterized by strong acidity of organic (pH 3.3 to 4.0) and  mineral horizons, moderate to thick (3 to 45 cm; 1 to 18 in) surface  accumulations of organic matter, and moderate to extremely low base  saturation. In Oregon, podzolization is less strongly expressed and soils  are more shallow and rocky. Pacific silver fir has been found on many soil  suborders throughout its range: Folists in the order Histosols; Aquents,  Fluvents, Orthents in the order Entisols; Andepts, Aquepts, Ochrepts,  Umbrepts in the order Inceptisols; and Aquods, Humods, and Orthods in the  order Spodosols (35).

    At upper elevations in Washington, soils beneath Pacific silver fir  stands are generally low in available nitrogen, with availability  decreasing with age (44). External nutrient cycling is slow; a mean  nitrogen residence time as long as 120 years has been found in old-growth  forest floors (24). Nitrification has not been found to occur.  Availability of phosphorus tends to be low but availability of base  elements does not appear to limit plant growth (42). Internal cycling  meets much of the annual nutrient requirements. Foliar nitrogen  concentrations between 0.7 and 1.2 percent and foliar phosphorus  concentrations of 0.11 to 0.20 percent have been reported (3,42,52).  Pacific silver fir differs significantly from western hemlock in its  ability to accumulate specific elements (46).

    Pacific silver fir grows at sea level along the coast from Alaska to the  Olympic Peninsula; farther inland, it is absent at lower elevations. Its  range in elevation is narrowest in Alaska, 0 to 300 m (0 to 1,000 ft), and  greatest in the western Cascade Range of Washington, where Pacific silver  fir may be found from 240 to 1830 m (800 to 6,000 ft). In British Columbia  it is found from 0 to 1525 m (0 to 5,000 ft) in elevation on western  Vancouver Island and from 180 to more than 1680 m (600 to more than 5,500  ft) on the lower mainland. Pacific silver fir grows on the highest ridges  and peaks in the Coast Ranges of Washington, from 365 to 850 m (1,200 to  2,800 ft). In the Olympic Mountains, it is the predominant montane species  up to 1400 m (4,600 ft), with lower limits at sea level on the west side  and at 360 m (1,200 ft) in the central mountains. It is found between 610  and 1830 m (2,000 and 6,000 ft) in the Cascade Range in Oregon as far   south as the divide between the Rogue and Umpqua Rivers. On the east side  of the Cascade Range, it is confined to high elevations, down to 1160 m  (3,800 ft) in Oregon and 1000 m (3,300 ft) in Washington (30,35).

Climate throughout the range of Pacific silver fir is distinctly  maritime. Summers are cool, with mean daily temperatures of 13° to 16°  C (55° to 61° F), and winter temperatures are seldom lower than  -9° C (16° F) (35). Mean number of frost-free days ranges from  40 near tree line to more than 250 at low elevations (26). Length of  growing season also differs from year to year at a given location. Mean  annual precipitation varies greatly, ranging from 6650 mm (262 in) on the  west coast of Vancouver Island to an extreme low of 965 mm (38 in) on the  eastern side of Vancouver Island. Average annual precipitation in the  Cascade Range is more than 1500 mm (59 in); winter snowpacks are as much  as 7.6 m (25 ft) deep (9). A summer dry season is characteristic of this  region, but Pacific silver fir is dependent on adequate soil moisture  during the growing season. It is most abundant on sites where summer  drought is minimal, such as areas of heavy rainfall, seepage, or prolonged  snowmelt.

Moist, coastal coniferous forests; 0--2000m; B.C.; Alaska, Calif., Oreg., Wash.

Systems

• Terrestrial

Comments: Forested slopes and flats, with spruce and hemlock.

Pacific silver firs reproduce only from seed. Both pollination and seed dispersal are effected by wind. Plants are capable of self-fertilization and produce mature cones and seeds two years after pollination. Cones disintegrate while on the tree and seeds are either dispersed by wind or small mammals. Cool moist sites are optimal for germination, but full sunlight produces maximum growth. Germination can occur on a variety of substrates, including litter, rotten wood, moss, and organic and mineral soils.

Foodplant / parasite
pycnium of Milesina blechni parasitises needle of Abies amabilis

Western hemlock is a common associate throughout most of the range of  Pacific silver fir, in the Abies amabilis zone and portions of the  Tsuga heterophylla zone (9). Noble fir (Abies procera) is an  important associate in southern Washington and northern Oregon. Other  associates west of the Cascade Range are Douglas-fir, western redcedar  (Thuja plicata), and grand fir (Abies grandis), with Sitka  spruce (Picea sitchensis) and lodgepole pine (Pinus contorta)  important near the coast. At subalpine elevations in the Tsuga  mertensiana zone (9), Pacific silver fir is associated with mountain  hemlock, Alaska-cedar (Chamaecyparis nootkatensis), and subalpine  fir (Abies lasiocarpa). Toward the eastern limits of its range, it  grows with a mixture of coastal and interior species: western larch (Larix  occidentalis), western white pine (Pinus monticola), lodgepole  pine, subalpine fir, grand fir, and Engelmann spruce (Picea  engelmannii). Shasta red fir (Abies magnifica var. shastensis)  is an associate in the extreme southern portion of its range.  Extensive pure stands of Pacific silver fir have been reported in the  Mount Baker and Mount Rainier regions and elsewhere in the southern  Washington Cascade Range (40).

    Pacific silver fir is a major species in the forest cover type Coastal  True Fir-Hemlock (Society of American Foresters Type 226) (5). It is also  found in the following types:

    205 Mountain Hemlock 
206 Engelmann Spruce-Subalpine Fir 
223 Sitka Spruce 
224 Western Hemlock 
225 Western Hemlock-Sitka Spruce 
227 Western Redcedar-Western Hemlock 
228 Western Redcedar 
229 Pacific Douglas-Fir 
230 Douglas-Fir-Western Hemlock

    Shrubs associated with Pacific silver fir are primarily ericaceous.  Blueleaf huckleberry (Vaccinium deliciosum), Cascades azalea (Rhododendron  albiflorum), and rustyleaf menziesia (Menziesia ferruginea) are  common understory species at higher elevations; copper bush (Cladothamnus  pyrolaeflorus) is important in subalpine British Columbia (2). Alaska  huckleberry (Vaccinium alaskaense), big huckleberry (V.  membranaceum), ovalleaf huckleberry (V. ovalifolium), and  devilsclub (Oplopanax horridum) are widespread associates. At its  lower limits of elevation, Pacific silver fir is found with salal (Gaultheria  shallon) and Oregongrape (Berberis nervosa).

    Common herbaceous associates are common beargrass (Xerophyllum  tenax), bunchberry (Cornus canadensis), twinflower (Linnaea  borealis), queenscup (Clintonia uniflora), dwarf blackberry  (Rubus lasiococcus), strawberryleaf blackberry (R. pedatus),  rosy twistedstalk (Streptopus roseus), coolwort foamflower  (Tiarella unifoliata), and deerfern (Blechnum spicant).  Rhytidiopis robusta is a constant bryophyte associate.

    Major habitat types include Abies amabilis-Tsuga  mertensiana/Vaccinium membranaceum-Rhododendron albiflorum on cold,  wet sites at high elevations and Abies amabilis/Xerophyllum tenax on  shallow coarse-textured soils at various elevations. Abies amabilis /  Vaccinium alaskaense is a widespread type on modal sites. Abies  amabilis/Rubus lasiococcus, Abies amabilis/Streptopus roseus, Abies  amabilis / Tiarella unifoliata, and Tsuga  heterophylla-Abies amabilis/Blechnum spicant are herb-dominated types  found in moist habitats. The Abies amabilis / Oplopanax horridum type  occupies wet, alluvial habitats (2,9).

Pacific silver fir is easily killed by fire  because of its shallow rooting habit and thin bark. It has lower  resistance to windthrow than Douglas-fir, western hemlock, or western  redcedar. It is susceptible to windthrow after heavy partial cuts (9), on  the borders of clearcuts or partial cuts, and even in closed canopy stands  during strong winds. Resistance to breakage from snow and damage by frost  is moderate. The foliage of Abies amabilis and other true firs is  more easily damaged by volcanic tephra than is the foliage of associated  conifers (22). Several types of animal damage have been reported: heavy  browsing by Roosevelt elk (34), bark stripping by bears in pole-size  stands, clipping of terminal buds by grouse and rodents (13), and cutting  of cones and cone buds by squirrels.

    Pacific silver fir is susceptible to many types of insect damage. Seed  chalcids (Megastigmus pinus and M. lasiocarpae) and cone  maggots (Earomyia abietum) have been known to infest a high  proportion of cones during good seed years (17). Western hemlock looper  (Lambdina fiscellaria lugubrosa) and western blackheaded budworm  (Acleris gloverana) are serious defoliators of mixed Pacific  silver fir and western hemlock stands in British Columbia. Many other  loopers are of minor importance; two species that cause periodic outbreaks  the greenstriped forest looper (Melanolophia imitata) and  saddleback looper (Ectropis crepuscularia). The western spruce  budworm (Choristoneura occidentalis) also feeds on Pacific silver  fir in pure and mixed stands.

    The silver fir beetle (Pseudohylesinus sericeus) and fir root  bark beetle (P. granulatus) can be very destructive together and  in combination with the root rotting fungi Armillaria mellea,  Heterobasidion annosum, Phellinus weiri, and Poria subacida. The  last major outbreak of silver fir beetles lasted from 1947 to 1955; it  killed 2.5 million m³ (88 million ft³) of timber in Washington  (12).

    An imported pest, the balsam woolly adelgid (Adelges piceae), is  the most devastating killer of Pacific silver fir. Attacks on the crown by  this insect result in swelling or "gouting" of branch nodes,  loss of needles, and reduced growth for many years; attacks on the stem  usually cause a tree to die within 3 years. Trees of all ages and vigor  are susceptible, although some individuals seem to have natural  resistance. In southern Washington, damage has been heavy on high-quality  sites at low elevations, such as benches and valley bottoms (28). In  British Columbia, heaviest damage is on similar sites below 610 m (2,000  ft). Pacific silver firs growing with subalpine firs at high elevations  are relatively immune and suffer only temporary gouting. Spread of the  aphid has been slow since the major outbreak of 1950-57, but infested  areas remain a problem. No effective direct control methods have been  found for forest stands.

    Pacific silver fir is a secondary host for hemlock dwarf mistletoe (Arceuthobium  tsugense) and can be infected in mixed stands containing western or  mountain hemlock. A. abietinum also attacks Pacific silver fir and  western hemlock; it is more common in central Oregon in the Cascade Range.  Needle casts (Lophodermium uncinatum, Phaeocryptopus nudus, Virgella  robusta) and rusts (Uredinopsis spp.) are common on  reproduction in some localities in British Columbia.

    Thinning studies on the west coast of Vancouver Island indicated that  Pacific silver fir is more susceptible to Heterobasidion annosum root  and butt rots than are western hemlock, Douglas-fir, or Sitka spruce.  Airborne infection of Pacific silver fir stumps was not seasonal as in  other species, and infection rates were high throughout the year (29).  Pacific silver fir is also one of the Northwest conifers most susceptible  to laminated root rot (Phellinus weiri) (27) and shoestring rot  (Armillaria mellea).

    Overmature Pacific silver firs are highly prone to heart rot, primarily  by the Indian paint fungus (Echinodontium tinctorium) and the  bleeding conk fungus (Haematostereum sanguinolentum). In British  Columbia, Pacific silver firs were free of decay to age 75; then incidence  increased with age to 11 percent at 275 years, 40 percent at 375 years,  and 100 percent in trees more than 400 years (6). Released advance  regeneration scarred by logging is rarely infected by heart rot fungi. In  one instance, E. tinctorium was nearly absent in young stands 30  years after release, even though adjacent unlogged stands were heavily  infected. Lack of suitable branch stubs for entry by fungi and rapid  closing of wounds because of accelerated growth are believed to prevent  infection (20).

    Deterioration is rapid after logging, windthrow, or death caused by  insects or diseases. Within 5 years of death, loss in cubic volume can be  from 50 to 100 percent. Primary decay fungi on dead wood are Fomitopsis  pinicola, Ganoderma applanatum, Hirschioporus abietinus, and Poria  subacida.

More info for the term: natural

Slash burning and stump removal decrease site preparation cost [56] but
have considerable repercussions. Slash burning has negative effects on
higher elevation ecosystems because of their low productivity and the
difficulty of replanting [57]. It also destroys advance regeneration
and delays natural regeneration [23]. Ruth [57] states, "it is good
insurance" to protect advance regeneration in these higher elevation
stands. These areas have a short burning season.

Miller and Bigley [46] found that slash burning decreases the number of
conifers, including Pacific silver fir. Logging of Pacific silver fir
leaves a high residue volume which can become a high fire hazard. Some
ways to reduce slash loadings and fire hazard are to cut lower volume or
younger stands, and use more volume or yard cull logs to encourage
utilization (which is currently practiced on federal lands). These
practices may reduce the effects of slash burning on site productivity
and stand development [46].

More info for the terms: root crown, secondary colonizer

Tree without adventitious-bud root crown
Secondary colonizer - off-site seed

More info for the terms: fire frequency, frequency, severity

In the Pacific silver fir zone, fires are infrequent (fire interval is
500 years) because of the humidity and the high levels of precipitation.
Surface fires are usually of low severity [69]. Some stands of Pacific
silver fir show no evidence of having burned. Fire frequency is a
limiting factor in the range of Pacific silver fir [69]. Pacific silver
fir is a fire-avoiding species throughout all stages of its life [72].
It is extremely fire sensitive primarily because its thin bark and
shallow roots [26]. Its foliage is highly flammable [50]. The mean
fire interval for Pacific silver fir as a primary dominant is 192 years
[1].

More info on this topic.

More info for the terms: climax, dispersion

Obligate Climax Species

Pacific silver fir is a late seral or climax species in most habitats
[41]. In the mountain hemlock zone, Pacific silver fir succeeds species
such as Shasta red fir, subalpine fir, and grand fir [27].

Pacific silver fir is very shade tolerant and has low spatial
requirements [14,15,22,26,71]. Pacific silver fir can survive in the
shade and emerge in stands that are uneven-aged [51]. Due to
ineffecient dispersion of seed by wind, migration is slow [56].

Following disturbance, Douglas-fir and noble fir become established.
Pacific silver fir is the last to invade, sometimes 400 to 500 years
after the disturbance. After extensive forest fires, Pacific silver fir
may not become important among the large trees for 700 to 800 years
[61,69]. Eventually, Douglas-fir and noble fir fail to reproduce [27].
Often, almost all understory species are eliminated by shade, resulting
in an open forest floor [51]. Pacific silver fir is common in mixed
stands and rare in even-aged stands [59].

More info for the terms: dispersion, frequency, fresh, litter

Pacific silver fir reproduces only from seed [14]. Seed production
begins at 20 to 30 years of age [14]. There are approximately 400 seeds
per cone; percentage of sound seed ranges from 6.3 to 35 percent
[14,24]. Good seed crops are generally produced every 2 to 3 years
[14,59], but intervals between good seed crops may be as long as 6 years
according to some reports [17,25]. Production of seed is poor due to
the high frequency of low pollen production years [14]. Complete crop
failures sometimes occur [59].

Pacific silver fir requires 2 years to complete its reproductive cycle
[63]. It is capable of self-fertilization [14,38]. Wind dispersion of
seed is inefficient because of seed size and cone disintegration [59].
Germination occurs in the spring. Germination can occur on a variety of
substrates such as litter, rotten wood, moss, organic and mineral soils,
and fresh volcanic tephra. Cool, moist sites are optimal for
germination, but full sunlight produces maximum growth [14]. Pacific
silver fir takes 9 years to reach breast height on average sites [14], 5
to 9 years on more favorable sites, and up to 80 years when severely
suppressed [36].

More info on this topic.

More info for the term: phanerophyte

Phanerophyte

More info for the term: tree

Tree

Pacific silver fir germinates on exposed mineral soils, but its seed
often travels only a short distance onto the site [56]. Burned soils
have radical temperature fluctuations, which may prevent Pacific silver
fir from establishing on burned sites. One year after the 1978 Hoh fire
in the Olyumpic Mountains, Pacific silver fir seedlings were found at a
great concentration, but they did not appear as healthy as other
seedlings [2]. Slash burning increases the time for Pacific silver fir
to reach 60 percent stocking rate [23].

Pacific silver fir has a low fire tolerance and is usually killed by any
forest fire [6,50,69].

Pacific silver fir can grow in a  variety of stand development conditions. It can seed onto outwash after  glacial retreat (35), seed into burned areas, develop from advance  regeneration after removal of the overstory, and grow slowly from a  suppressed tree into an overstory tree in more uneven-aged stands where  disturbances are minor.

    Advance regeneration may have a cone-shaped crown or can become flat  topped, with lateral branch growth greatly exceeding height growth. After  extensive removal of the overstory, some (but not all) advance  regeneration can accelerate in diameter and height growth and form a new  forest (20).

    Even-aged, pure, or mixed stands vary in stocking but can have more than  2,470 stems per hectare (1,000/acre). When crowns close during the sapling  and pole stages, understory vegetation is almost completely eliminated by  shade, causing an open forest floor. Lower limbs become shaded and die,  creating branchfree boles. This condition may last 200 years (31).

    Eventually the overstory crowns abrade and let more light into the  understory, allowing development of shrubs and advance regeneration. This  may occur after one to three centuries-probably depending on site quality,  spacing, and disturbance history-and has been observed to last to age 500  years (31). Individual overstory trees eventually die and advance  regeneration grows slowly upward, creating a multi-aged, old-growth forest  with a major component of Pacific silver fir that will be  self-perpetuating, barring a major disturbance. Pacific silver fir is  referred to as the climax species at mid-elevations of its range (9)  because of its ability to survive in the shade and to emerge in all-aged  stands.

    Because of its slow early height growth, associated species such as  western hemlock, Douglas-fir, and noble fir initially overtop Pacific  silver fir when grown in the open. After the initial overtopping, on many  sites Pacific silver fir appears to outgrow and become taller than western  hemlock after 100 years (19). On cool, moist sites at the upper extremes  of the range of Douglas-fir, Pacific silver fir can stratify above  Douglas-fir as well (40). Noble fir appears to maintain a height advantage  over Pacific silver fir indefinitely on all sites where both species grow.

    Pacific silver fir is one of the most shade-tolerant trees in the  Northwest. There is confusion regarding its relative shade tolerance  compared with western hemlock. It has been described as equal, greater,  and less shade tolerant than hemlock (26,40). It can most accurately be  classed as very tolerant of shade.

    Most silvicultural treatments of Pacific silver fir have dealt with  regeneration and early stocking levels after old-growth stands were  logged. Regeneration practices vary from clearcutting followed by burning  and planting to clearcutting with reliance on natural advance and  postlogging regeneration. Each practice successfully obtains regeneration  for certain sites and management regimes. Early stocking control-thinning  sapling and pole-size trees to 495 to 740/ha (200 to 300/acre)- is  practiced to increase growth rates of individual trees. Trees left in  pole-size stands after thinning markedly increase in diameter growth and  apparently respond to fertilization. Possible commercial thinning regimes,  rotation ages, and regeneration plans for managed stands (where advance  regeneration may not be prevalent) are primarily in the planning stages.

    Young, post-harvest stands can develop densely from advance  regeneration. These stands may require thinning to maintain diameter  growth, to keep from buckling in heavy snow or wind, and to ensure advance  regeneration before the next harvest.

Pacific silver fir seedlings have roots that more  closely resemble a true taproot system than do western hemlock seedlings  (38), and the roots can penetrate more compact soils than can the roots of  western redcedar, Sitka spruce, and western hemlock (27). Seedlings can  develop adventitious roots where volcanic tephra covers the original soil  surface (1). Advance regeneration has, small root-to-shoot ratios, and the  roots are predominantly in the organic layers. Mature Pacific silver fir  can have a relatively flat, shallow, platelike root system on poorly  drained or shallow soils or in areas where there is nutrient  immobilization in the forest floor (15). On soils where podzolization  develops and organic matter accumulates, feeding roots become concentrated  in organic horizons as a stand ages.

    Peak growth of seedling roots occurs when shoots are least active.  Activity is high in early spring and late autumn even in cold soils. Roots  can also be active during the winter when soil temperatures are just above  freezing; however, water conductance is dramatically reduced after  seedlings are preconditioned to cold temperatures (39). At upper  elevations in both young and mature stands, a large proportion of annual  biomass production is in the root systems (15). Roots are intensely  mycorrhizal at upper elevations, and Cenococcum graniforme is a  major mycorrhizal symbiont (45).

The dense growth of Pacific silver fir provides cover and protection during the winter for wildlife. Old-growth stands provide habitat for mountain goat, northern spotted owl, Vaux’s swift, western red-backed vole, and the Olympic salamander. Seeds provide food for birds, rodents, and squirrels, while the leaves of growing shoots are browsed by elk.

More info on this topic.

Pacific silver fir has a 2-year reproductive cycle. In May of the first
year, buds are initiated; differentiation follows in July.
Megagametophytes and ovuliferous scales are initiated in mid-July and
mid-August, respectively. Both are dormant by November and remain
dormant until April of the second year, at which time development of the
pollen-cone and seed-cone buds is resumed [63]. Pollination occurs in
May and is well synchronized with female receptivity [14,63].
Fertilization occurs in early July, 4 to 5 weeks after pollination. In
early August, meristems and cotyledons of embryos develop and mature by
the end of the month. Cones change from green to purple at maturity
[6,63]. As cones mature, they disintegrate before the seed can be
dispersed, which occurs in September and October [24,63].

Germination occurs in the spring [14]. Juvenile growth ranges from 4 to
16 inches (10-40 cm) per year [14]. Advance regeneration is quite
sturdy but grows slowly. Terminal growth averages 19.9 (49.7 cm) per
year [14].

Although Pacific silver fir can produce  epicormic or adventitious sprouts, it does not regenerate by stump  sprouting. Upturning of lower branches after tops of young trees are cut  may resemble sprouting.

Pacific silver fir germinates in the  spring after overwintering under snow. Germination is epigeal (37).  Seedlings germinating on snow because of early snowfall or late seed fall  are generally short lived. Germination can occur on a variety of media: on  litter humps and in moist depressions in the subalpine zone; on edges of  melting snowpack in subalpine meadows; and in litter, rotten wood, moss,  organic soils, mineral soils, and fresh volcanic tephra (2,11,25).  Survival is better on mineral seedbeds than on organic seedbeds. Early  mortality of seedlings is attributable more to germination on snow,  adverse climatic effects, and competing vegetation than to disease (18).

    Cool, moist habitats are best for germination, but full sunlight  produces maximum subsequent growth. Seedlings can also grow under dense  shade; seedlings 8 to 12 years old and about 10 cm (4 in) tall can  frequently be found beneath older, closed forest canopies. Seedlings that  survive continue to grow very slowly, existing as advance regeneration  that can be 65 to 110 years old and only 45 to 200 cm tall (18 to 80 in).  When existing as advance regeneration, Pacific silver fir has flat-topped  crowns caused by slow height growth relative to lateral branch growth.

    Seedlings are sturdy and erect and resist being flattened by litter and  heavy, wet snow. Survival of Pacific silver fir as advance regeneration at  middle elevations, where western hemlock is primarily found in openings,  is attributed partly to its ability to resist being buried by litter after  snowmelt (40). At the highest elevations, Pacific silver fir is found  primarily in openings and less frequently beneath the canopy (38). Stems  of seedlings growing on slopes often have a "pistol-butted"  sweep, caused by heavy snow creeping downhill.

Cone production begins at  years 20 to 30 (33,37). Good seed years vary from region to region; a good  seed crop generally occurs every 3 years (8). Pacific silver fir is not  considered a good seed producer; this condition is attributed to frequent  years of low pollen, the extended period between pollination and  fertilization, and archegonial abortion producing empty seeds (33).  Percentage of sound seed varies, with reports of 6.7 to 35 percent and 51  percent in one location (4). Germinative capacity varies widely from 3 to  70 percent- but averages 20 to 30 percent. Cleaned seeds range from 17,200  to 45,860/kg (7,800 to 20,800/lb) (37).

    The seeds are heavier than seeds of most Pacific Northwest conifers  except noble fir. Seeds each contain a single wing but often fall from the  upright cone axis by pairs on ovuliferous scales, as the bracts contort  and tear themselves from the cone-a process that does not require wind.  When the seeds are dispersed by the wind, they do not carry far; unsound  seeds are carried farther than sound seeds. In one study, only 9 percent  of the sound seeds were found more than 114 m (375 ft) from the stand  edge, compared with 41 percent at the stand edge and 34 percent more than  38 m (125 ft) (4).

Pacific silver fir is monoecious;  self-fertilization is possible because times of pollen dispersal and seed  cone receptivity overlap on the same tree. Flowers differentiate from  axillary buds of current-year lateral shoots in early July of the year  before seed development (32). When receptive to pollination, the seed  cones appear purple, erect, and 8 to 16 cm (3 to 6 in) tall on the upper  surfaces of 1-year-old branches in the upper parts of tree crowns. Just  before pollination, the pollen cones appear red, pendent, and usually  abundant on the lower surfaces of the branches somewhat lower on the  crowns than the seed cones. Cone buds burst the following May, and  pollination occurs about 2 weeks later-before vegetative bud burst. The  pollen does not germinate and begin forming its pollen tube until 4 to 5  weeks later, resulting in a 6-week delay between pollination and  fertilization (7,33).

    Initiation of phenological events varies with latitude, altitude,  aspect, weather, and snowpack and is apparently related to mean soil and  air temperatures. For example, pollination may occur in mid-May at 900 m  (2,960 ft) in central Washington but is delayed until mid-June at 1600 m  (5,250 ft) and until late May in southern British Columbia (7,32,33).

    Seeds are fully mature in late August, and dissemination begins in  mid-September- one of the earliest dispersal times for Pacific Northwest  conifers. Initiation of dispersal is apparently independent of altitude or  latitude (7); most seeds are shed by the end of October but may be shed  until the following April (21,33).

There is a broad range of height growth rates  of Pacific silver fir because of the wide variation of climates with  elevation and latitude. Site index values (at 100 years) in southern  British Columbia range from 12 to 46 m (40 to 150 ft) (26) and have been  negatively correlated with elevation in Washington (16). In subalpine tree  clumps at higher elevations, Pacific silver firs reach heights of 18 to 24  m (60 to 80 ft).

    The largest Pacific silver fir tree known was in the Olympic National  Park, WA. It was 256 cm (101 in) in d.b.h. and 74.7 m (245 ft) tall. Trees  55 to 61 m (180 to 200 ft) tall and more than 60 cm (24 in) in d.b.h. are  common in old-growth stands. Trees 500 to 550 years old have been found on  Vancouver Island and in the North Cascades National Park, WA. Maximum age  reported is 590 years (48).

    Early height growth from seeds is generally considered very slow; 9 or  more years are usually required to reach breast height. Juvenile height  growth ranges from 10 to 40 cm (4 to 16 in) per year, depending on length  of the growing season (50). Planted seedlings also grow slowly, with  height increments of 3 to 15 cm (I to 6 in) for the first few years after  planting (47). On productive sites at low elevations, Pacific silver fir  is capable of much greater rates, averaging 90 cm (35 in) per year above  breast height on some 30-year-old trees (16). Growth of released advance  regeneration is more rapid than early growth from seeds (20,49). After an  initial lag following overstory removal (as by avalanche, windstorm, or  clearcutting), growth rates of 50 cm (20 in) or more per year can occur  (49). When released from suppression, advance regeneration trees change  from flat-topped to more conical crowns (41).

    Pacific silver fir occasionally shows an abnormal height growth pattern,  in which various sapling and pole-size trees curtail height growth for at  least 1 year while adjacent trees grow normally. Causes of this phenomenon  are not known.

    Height-age and site index curves for Pacific silver fir have recently  been constructed (23); however, little information on yield of  second-growth stands is available. Data from sample plots on a variety of  sites (table 1) indicate that large volumes can be expected from Pacific  silver fir in pure stands or mixed with hemlocks. Close spacing and lack  of taper are partly responsible for high volumes found in pure, even-aged  stands of Pacific silver fir.

    Table 1- Volume yield of second-growth stands in  Washington and British Columbia, dominated 
by Pacific silver fir, based on sample plot data.           
Plot location  
and elevation  Proportion  
of Pacific silver fir¹   
 
Age   
 
Density 
 
Volume              pct  yr  trees/ha  m³/ha      Washington:                King County, 975 m  100  47  1,850  980        Whatcom County, 760 m  95  70  2,879  875      Vancouver Island, BC (28):                Santa Maria Lake, 533 m  85  100  1,361  1593        Labor Day Lake, 922 m  65  125  1,016  1505        Haley Lake, 1204 m  64  108  1,011  950        Haley Lake, 1119 m  59  92  1,302  1197        Sarah Lake, 116 m  53  111  420  1220        pct  yr  trees/acre  ft³/acre      Washington:                King County, 3,200 ft  100  47  749  14,004        Whatcom County, 2,500 ft  95  70  1,165  12,504      Vancouver Island, BC (28):                Santa Maria Lake, 1,750 ft  85  100  551  22,764        Labor Day Lake, 3,025 ft  65  125  411  21,506        Haley Lake, 3,950 ft  64  108  409  13,576        Haley Lake, 3,670 ft  59  92  527  17,105        Sarah Lake, 380 ft  53  111  170  17,434      ¹Based on the  total nymber of trees in sample plots.        Volume in old-growth stands is extremely variable, depending on the mix  of species and degree of stand deterioration. One densely stocked plot at  1100 m (3,600 ft) in the north Cascades had 1813 m³/ha (25,895 ft³/acre),  83 percent Pacific silver fir by volume. An older, more open stand in the  same area had 840 m³/ha (12,000 ft³/acre).

    Stands at upper elevations (predominantly Pacific silver fir) in western  Washington carry large amounts of leaf biomass- 18 to 25 t/ha (8 to 11  tons/acre); total standing biomass ranges up to 500 t/ha (223 tons/acre)  in mature and older forests. Leaf area indexes of 14 have been reported  (14). A large proportion of the net primary production is below ground in  subalpine stands; this is apparently a characteristic of the cool sites  and low nutrient mobilization rates rather than the species itself. Values  of net primary production in two upper elevation Pacific silver fir stands  in western Washington were determined (15). In the 23-year-old stand,  total net primary production was 18 000 kg/ha (16,060 lb/acre); in the  180-year-old stand it was 17 000 kg/ha (15,170 lb/acre). Of this, the  above-ground portion was 6500 kg/ha (5,800 lb/acre) and 4500 kg/ha (4,010  lb/acre) for the two stands, respectively. Woody growth made up 65 percent  of this amount in the younger stand, and 50 percent in the older stand.  The below-ground portion was 11 500 kg/ha (10,260 lb/acre) and 12 500  kg/ha (11,150 lb/acre) for the two stands, respectively. Small conifer  roots and mycorrhizae made up 65 percent of this amount in the younger  stand and 73 percent in the older stand.

Despite its extensive range, Pacific silver fir is not a highly variable  species. Cortical oleoresin analyses of sample trees from northern  California to the Alaska border revealed no chemical variants, and  variation among populations was similar to that within populations (51).  Similar results were obtained from analyses of bark blister and leaf and  twig oils.

    No artificial hybrids of Pacific silver fir and any other species have  been described. It does not hybridize with any of its true fir associates  even though pollen shedding and cone receptivity periods may overlap in  some localities (7). Some morphological intermediates of Pacific silver  fir and subalpine fir have been described, but these proved not to be  hybrids (36).

    The only known cultivated variety of Pacific silver fir is Abies  amabilis var. compacta, a dwarf form that has current branches  2 to 3 cm (0.8 to 1.2 in) long.

The following is a representative barcode sequence, the centroid of all available sequences for this species.

Barcode of Life Data Systems (BOLDS) Stats
Public Records: 1
Specimens with Barcodes: 1
Species With Barcodes: 1

Year Assessed

• Needs updating

Assessor/s

Reviewer/s

Canada

Rounded National Status Rank: N5 - Secure

United States

Rounded National Status Rank: N5 - Secure

Rounded Global Status Rank: G5 - Secure

Reasons: Moderately widespread in limited geographic range.

Please consult the PLANTS Web site and your State Department of Natural Resources for this plant’s current status (e.g. threatened or endangered species, state noxious status, and wetland indicator values).

Pacific silver firs are susceptible to several fungal diseased, including Annosus root disease (Heterobasidion annosum). Infected trees may show retarded leader growth, sparse and chlorotic foliage, stem decay, and abortive cones. The most reliable way to detect this disease is by the presence of fruiting bodies in the duff layer at the root collar on the outer bark. Trees become infected by rood contact or by airborne spores falling onto woonds. Other fungal diseases include Indian paint fungus (Echinodontium tinctorium) and laminated root rot (Phellinus weirii). Both can infect stands of trees and result in patches of damaged or dead trees.

Trees weakened by disease or poor growing conditions may become infested with fir-engraver beetle (Scolylus ventralis), silver fir beetle (Pseudohylesinus sericeus), or fir root bark beetle (Pseudohylesinus granulatus). In large numbers, these beetles may kill entire trees before any symptoms are observed. Pacific silver firs are also susceptible to Western spruce budworm (Choristeneura occidentalis), Douglas fir tussock moth (Orygia pseudotsugata) infestation. Applying fertilized and varying the age and density of stands reduces the infestation. Balsam wooly aphids (Adelges piceae) are an extremely devastating pest to this species. Infected trees appear swollen with little growth and usually die from the top down within 2 to 3 years. To prevent further infestation, most trees need to be removed and the site rplanted with such species as western hemlock.

More info for the terms: association, density, duff, phase, presence, selection, tree, tussock

Rotation periods for Pacific silver fir vary, depending on management
objectives. For mountain goat habitat, the recommended rotation period
is 90 to 110 years [70]. For other nontimber (i.e. recreational, etc.)
benefits, the suggested rotation period is 150 to 200 years. Commercial
rotations are seldom longer than 110 years [70]. After release by
logging or windfall, suppressed trees respond with immediate and
substantial growth [59]. At lower elevations in the Pacific silver fir
zone, Pacific silver fir usually sun scalds when used as leave tree in
shelterwood cuttings [26]. Sudden exposure to sunlight temporarily
reduces growth. By the third season, the exposed trees are growing
faster than those trees at the stand edge. As many as seven growing
seasons may be needed for Pacific silver fir to reach maximum rates of
branch and height growth [65]. The shade tolerance of Pacific silver
fir makes it a good choice for the selection method. The disadvantage
of this practice is that it appears to encourage disease [36].

The timing of cone collection (mid to late August) is important because
cones disintegrate as they mature. Felling and topping are not
successful collection methods. The cones are susceptible to molding and
heat build-up if sacked when wet [18]. Calcid flies (Pregastigmus spp.)
infect cones of Pacific silver fir [59]. Franklin [24] discusses a cone
drying schedule and seed storage conditions. Seeds are delicate and
their coats may be damaged when drying [16]. Edwards [17] reviews
techniques of seed extraction, viability, and germination testing.
Cleaned seeds range from 17,200 to 45,860 seeds per pound (7,800-20,800
seeds/kg) [14], and average 11,000 to 13,800 seeds per pound
(4,590-6,210 seeds/kg) [24]. A stratification period of 21 to 28 days
is required. Seeds should be sown in spring at a density of 62.5 to 125
per acre (25-50 per ha) and approximately 0.25 inch (0.64 cm) deep,
depending on the site [24]. Arnott and Mathews [7] discuss nursery
practice for Pacific silver fir. Highest stocking can be achieved on
bare soil [34]. Seedlings planted in logged areas have done poorly [6].

Gessel and Klock [31] report that fertilizer contributes significantly
to growth of Pacific silver fir on poor sites, but Packee and others
[51] disagree. During the seedling stage when growth is slow,
fertilizer may be more effective than during other stages [52]. The
application of nitrates are more beneficial to Pacific silver fir than
ammonia compounds [31,42,51]. Fertilizer combined with thinning results
in accelerated volume and radial growth [31].

Herbicides have various effects on Pacific silver fir. The effect of
glyphosate and granular and liquid hexazinone had little effect. 2,4-D
ester, when applied at maximum rates in spring and late summer, had a
moderate effect on Pacific silver fir. Triclopyr ester had no effect
when applied in summer [10].

Pacific silver fir is damaged by mountain beaver, black bear, and
porcupine, which increases susceptibility to pathogens [56]. Wounds
result in wetwood, circular or radial shake, and frost cracks [3].

Pacific silver fir is among those species that are most seriously
affected by annosus root disease (Heterobasidion annosum). The
incidence of fungal infestations is higher in stands 200 years or older
than in younger stands [14]. Often a rotation of 40 to 120 years and
minimization of wounding trees will reduce intermediate entry of the
pathogen [22]. Airborne infection of Pacific silver fir is high
year-round [14]. Annosus root disease infects trees when roots grow in
contact with infected fungus food base. Other trees become infected
through root contacts. Air-borne spores colonize wounds up to 1 month
old [62]. Trees with this fungus show butt rot, retarded leader growth,
sparse and chloritic foliage, and distress cone crops; mortality may
occur [22,55]. Young stands can have high infection levels with low
severity damage [70]. The fungus and tree can "wall off" each other,
but once the tree becomes weakened, the fungus will invade [22].

After being weakened by annosus root disease, infestation by
fir-engraver beetle (Scolylus ventralis), silver fir beetle
(Pseudohylesinus sericeus), or fir root bark beetle (Pseudohylesinus
granulalus) is frequent [14,22,55]. When beetle populations are high,
Pacific silver fir may be attacked and killed before symptoms of
infection are found. These effects are enhanced during a drought [55].
Annosus root disease also causes stem decay [22].

The most reliable way to diagnose Annosus root disease is by the
presence of conks, or fruiting bodies, found in the duff layer at the
root collar on the outer bark. Ectotrophic mycelium on the roots cannot
be used in diagnosing annosus root disease [55].

To prevent damage to trees during logging, options include using
rubber-tired skidders, working with a proven crew, and afterwards,
treating remaining stumps with a registered pesticide to prevent its use
as a food source [62]. At the time of logging, stump removal to reduce
innoculum in the soil is useful in preventing further contamination
[62]. Borax application can be part of timber sales contracts when this
treatment is considered appropriate [70]. Saplings and pole-sized trees
are too small to be effective innoculum sources. Management should
involve reducing mortality, thinning fir trees at least 25 feet (7.5 m)
from dead trees, and minimizing wounding during salvage logging [22].

Armillaria (Armillaria ostoyae) is often a secondary pathogen of trees
infected with annosus root disease [55]. Pacific silver fir is
moderately susceptible to Armillaria. In stands with smaller trees,
thinning those within 25 feet (7.5 m) of dead trees, reducing mortality,
and minimizing wounding is helpful. Prescribed burning may slow
Armillaria growth [22]. Shoestring rot (Armillaria mellea) is also
detrimental to Pacific silver fir [14].

Fungi found in advance regeneration of Pacific silver fir are Indian
paint fungus (Echinodontium tinctorium) and Stereum sanguinolentum [20].
Indian paint fungus has been located on healthy stems and encased branch
piths of suppressed Pacific silver fir. Decay is commonly found near
wounds [4]. Infection sites include small diameter branch stubs between
50 and 60 years of age [4]. Indian paint fungus has a dormant phase,
which occurs when wounded tissues heal [4]. When trees receive a new
injury, the fungus resumes growth [3]. Indian paint fungus is most
easily recognized by the presence of conks or slow decay in old large
wounds [22]. Stand rotation should be 150 years or less and wound
reduction activities should be practiced [22]. Filip and Schmitt [2]
discuss color recognition of Indian paint fungus and planning and
operational activities.

Pacific silver fir is moderately susceptible to laminated root rot
(Phellinus weirii), which creates forest patches of damaged or dead
trees when abundant [15]. Infected trees in sawtimber-sized stands
should be removed, followed with stump removal or replacement with
disease-tolerant species. Air-drying the stumps kills the fungi. Fire
is ineffective against annosus root disease, Armillaria, and laminated
root rot [56].

Potebniamyces dieback (Phacidium balsamicola) causes small branch
dieback and swelling at the girdling point but does not cause
significant losses. Treatment involves spacing severely infected trees
at precommercial thinning levels. For white-spored rusts (Uredinopsis
spp.), site preparation procedures should avoid encouraging the growth
of alternate hosts. In severe cases, it may be necessary to apply
herbicide to alternate hosts. There is no management practice known for
Virgilla robusta and Abies rust (Pucciniatrum spp.), except to minimize
the number of alternate hosts of Abies rust during site preparation.
Other fungi prevalent in fir stands include Caloscypha fulgens,
Sirococcus blight, and Sirococcus strobilinus [62].

Pacific silver fir is also susceptible to western spruce budworm
(Choristeneura occidentalis), Douglas-fir tussock moth (Orygia
pseudotsugata), and fir-engraver beetle [22,35]. The effects of these
pests can be alleviated by the application of fertilizer, and minimized
by variation of stand structure and by planting pest-tolerant species
[22]. At sites of western spruce budworm infestation, treatment should
decrease the number of vulnerable trees and should increase the number
of young trees by lowering maximum tree sizes. Ambrosia beetles
(Trypodendron lineatum and Gnathotrichus sulcatus) can be captured with
pheromone, multifunnel traps in late June when the beetles are flying.
Harvesting should be planned so that logs are not left on the ground to
be attacked by ambrosia beetles [45]. One of the most devastating pests
to Pacific silver fir is balsam woolly aphid (Adelges piceae) [14,57].
Infested trees appear swollen, with gouty twigs, poor crowns, and little
growth; death occurs within 2 to 3 years [22]. Infested trees have
mottled-red foliage, distinct "crown lean", and appear to die from the
top down. Trees greater than 28 inches (71 cm) in d.b.h. sustain the
most damage among the dominant crown classes [29]. In order to protect
nearby stands, the advance regeneration must be destroyed and the site
should be returned to a seral habitat, such as western hemlock [56].

Pacific silver fir is a secondary host for dwarf mistletoe (Arceuthobium
tsugense and Arceuthobium abietinum) [14]. Dwarf mistletoes cause
growth loss and tree mortality when in association with canker fungi
(Cytospora abietis). The key management practices should be detection,
evaluation, prevention, and suppression. Living infected residues
should be killed before susceptible regeneration reaches 3 feet (0.9 m)
or 10 years of age [22]. Ruth [57] suggests removing the overstory and
burning seedlings and other residue material in seedling infected
stands. Slash burning may be one of the most effective tools to
eliminate dwarf mistletoe. Special site preparation and herbicides may
also be useful tools for treatment [56].

Contact your local Natural Resources Conservation Service (formerly Soil Conservation Service) office for more information. Look in the phone book under ”United States Government.” The Natural Resources Conservation Service will be listed under the subheading “Department of Agriculture.”

Cultivars include a slow-growing, broadly ovoid form, ‘Compacta’ and a low-growing, spreading form with horizontal branches, ‘Spreading Star.’ Retail nurseries in the Pacific Northwest that stock native shrubs and trees may carry the cultivars.

Cone production may begin at an age of 20 to 30 years. Each cone can produce up to 400 seeds, but the percentage of viable seed ranges from 6.3 to 35 percent. Preferred methods of cone collecting include extension poles with appropriate pruners. Cones should be collected between mid and late August or just prior to disintegration. They should be stored in well-ventilated bags or sacks at temperatures between 70 and 80 degrees until the cones have disintegrated. Seeds can be extracted mechanically by using screens and then cold-stratified under dry conditions at temperatures between 10 and 30 degrees F for 4 to 6 months. Germination is best accomplished by placing them in a moist, well-aerated soil mix at temperatures between 35 and 40 degrees F. Light enhances germination and development of seedlings. Plant can be grown either individually in containers or in flats prior to transplantation. Under field conditions, seed should be sown in the spring at a density of 62.5 to 125 per acre and approximately 0.25 inches deep. During the first few years, growth ranges from 4 to 16 inches annually. Fertilizer combined with thinning enhances growth.

Management for most fungal diseases involves thinning at least 25 feet from dead trees and minimizing wounding during logging or trimming. Treating remaining stumps with fungicide or stump removal after logging is useful in preventing further contamination. In some cases, removal of infected trees and trunks should be practiced as soon as disease is diagnosed. Air drying large stumps often reduces chances of further infection.

Pacific silver fir is marketed with western hemlock and is typically  used for construction framing, subflooring, and sheathing. It is commonly  used for construction plywood even though it is not as strong as  Douglas-fir. Because of its light color and lack of odor, gum, and resin,  Pacific silver fir is well suited for container veneer and plywood. It is  occasionally used for interior finish and is suitable for poles. Good  yields of strong pulp can be produced by both mechanical and chemical  processes. It is a minor Christmas tree species, and its boughs are  occasionally used for decorative greenery.

    Because Pacific silver fir is common on midslopes of the Cascade Range,  it is a large component of many municipal watersheds, wilderness areas,  and recreation areas. Its beauty and ability to withstand or respond to  human impact make it a suitable species for multiple-use management.

Pacific silver fir is used in urban landscaping and grown commercially for Christmas trees. When used for landscaping, sufficient space should be allocated for the relatively large size of mature trees. The soft, light-weight wood is weak and has low durability. It has been used for light construction frames, construction plywood, container veneer, and pulpwood.

The dense growth of Pacific silver fir provides cover and protection during the winter for wildlife. Old-growth stands provide habitat for mountain goat, northern spotted owl, Vaux’s swift, western red-backed vole, and the Olympic salamander. Seeds provide food for birds, rodents, and squirrels, while the leaves of growing shoots are browsed by elk.