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.
Regularity: Regularly occurring
Regularity: Regularly occurring
Global Range: Southern Southeast Alaska to northwestern California.
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].
Regional Distribution in the Western United States
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
Occurrence in North America
- The native range of Pacific silver fir.
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.
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 . The crown is rigid and symmetrical with
lateral branches perpendicular to the stem . Young trees have
resin-filled blisters protruding from the smooth, thin bark. The bark
of older trees is rough textured and flaky .
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 .
Habitat and Ecology
Comments: Forested slopes and flats, with spruce and hemlock.
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 . 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 .
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 . Growth is successful
with thick humus present . Soils are generally shallow, but soil
depth varies from 1.2 to 12 inches (3-30 cm) . Soils are acidic in
the rooting zone (pH 5) . Whatever the soil type, an adequate,
year-round water supply is very important. Often nitrogen and
occassionally sulfur are limiting elements in soils . Soils rich in
magnesium and calcium indicate good sites for Pacific silver fir .
The elevation at which Pacific silver fir grows is quite variable. It
is more common at higher elevations but grows faster at lower elevations
. 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].
Key Plant Community Associations
Pacific silver fir commonly occurs in late seral or climax mixed-conifer
stands . 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 . 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 
Preliminary classification of forest communities in the central portion
of the western Cascades in Oregon 
Forest communities of Mount Rainier National Park 
Plant association of Mount Hood and Willamette National Forests of Oregon 
Forest communities of northern California 
Plant associations for the western hemlock zone 
Preliminary classification systems for the vegetation of Alaska .
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):
FRES22 Western white pine
FRES23 Fir - spruce
FRES24 Hemlock - Sitka spruce
Habitat: Cover Types
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
Habitat: Plant Associations
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
Soils and Topography
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).
Habitat & Distribution
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.
pycnium of Milesina blechni parasitises needle of Abies amabilis
Associated Forest Cover
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).
Diseases and Parasites
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.
Fire Management Considerations
Slash burning and stump removal decrease site preparation cost  but
have considerable repercussions. Slash burning has negative effects on
higher elevation ecosystems because of their low productivity and the
difficulty of replanting . It also destroys advance regeneration
and delays natural regeneration . Ruth  states, "it is good
insurance" to protect advance regeneration in these higher elevation
stands. These areas have a short burning season.
Miller and Bigley  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 .
Tree without adventitious-bud root crown
Secondary colonizer - off-site seed
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 . 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 . Pacific silver
fir is a fire-avoiding species throughout all stages of its life .
It is extremely fire sensitive primarily because its thin bark and
shallow roots . Its foliage is highly flammable . The mean
fire interval for Pacific silver fir as a primary dominant is 192 years
More info for the terms: climax, dispersion
Obligate Climax Species
Pacific silver fir is a late seral or climax species in most habitats
. In the mountain hemlock zone, Pacific silver fir succeeds species
such as Shasta red fir, subalpine fir, and grand fir .
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 . Due to
ineffecient dispersion of seed by wind, migration is slow .
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 .
Often, almost all understory species are eliminated by shade, resulting
in an open forest floor . Pacific silver fir is common in mixed
stands and rare in even-aged stands .
Pacific silver fir reproduces only from seed . Seed production
begins at 20 to 30 years of age . 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 . Complete crop
failures sometimes occur .
Pacific silver fir requires 2 years to complete its reproductive cycle
. It is capable of self-fertilization [14,38]. Wind dispersion of
seed is inefficient because of seed size and cone disintegration .
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 . Pacific
silver fir takes 9 years to reach breast height on average sites , 5
to 9 years on more favorable sites, and up to 80 years when severely
Growth Form (according to Raunkiær Life-form classification)
Plant Response to Fire
often travels only a short distance onto the site . 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 . Slash burning increases the time for Pacific silver fir
to reach 60 percent stocking rate .
Immediate Effect of Fire
Reaction to Competition
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.
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).
Life History and Behavior
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 . 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 . Juvenile growth ranges from 4 to
16 inches (10-40 cm) per year . Advance regeneration is quite
sturdy but grows slowly. Terminal growth averages 19.9 (49.7 cm) per
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.
Seed Production and Dissemination
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).
Flowering and Fruiting
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).
Growth and Yield
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.
and elevation Proportion
of Pacific silver fir¹
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.
Molecular Biology and Genetics
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.
Barcode data: Abies amabilis
Statistics of barcoding coverage: Abies amabilis
Public Records: 1
Specimens with Barcodes: 1
Species With Barcodes: 1
IUCN Red List Assessment
Red List Category
Red List Criteria
Abies amabilis has a very large extent of occurrence and occurs as many millions of mature individuals, despite historical reduction due to unsustainable logging in the past. It regenerates well after disturbance, including clear-felling and on other sites, e.g. after retreating glaciers. Fires and pathogens are a threat but their effect is mostly local. Therefore this species is assessed as Least Concern.
National NatureServe Conservation Status
Rounded National Status Rank: N5 - Secure
Rounded National Status Rank: N5 - Secure
NatureServe Conservation Status
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).
Pests and potential problems
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.
Rotation periods for Pacific silver fir vary, depending on management
objectives. For mountain goat habitat, the recommended rotation period
is 90 to 110 years . 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 . After release by
logging or windfall, suppressed trees respond with immediate and
substantial growth . At lower elevations in the Pacific silver fir
zone, Pacific silver fir usually sun scalds when used as leave tree in
shelterwood cuttings . 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 . 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 .
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 . Calcid flies (Pregastigmus spp.)
infect cones of Pacific silver fir . Franklin  discusses a cone
drying schedule and seed storage conditions. Seeds are delicate and
their coats may be damaged when drying . Edwards  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) , and average 11,000 to 13,800 seeds per pound
(4,590-6,210 seeds/kg) . 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 . Arnott and Mathews  discuss nursery
practice for Pacific silver fir. Highest stocking can be achieved on
bare soil . Seedlings planted in logged areas have done poorly .
Gessel and Klock  report that fertilizer contributes significantly
to growth of Pacific silver fir on poor sites, but Packee and others
 disagree. During the seedling stage when growth is slow,
fertilizer may be more effective than during other stages . 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 .
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 .
Pacific silver fir is damaged by mountain beaver, black bear, and
porcupine, which increases susceptibility to pathogens . Wounds
result in wetwood, circular or radial shake, and frost cracks .
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 . Often a rotation of 40 to 120 years and
minimization of wounding trees will reduce intermediate entry of the
pathogen . Airborne infection of Pacific silver fir is high
year-round . 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 . 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 . The fungus and tree can "wall off" each other,
but once the tree becomes weakened, the fungus will invade .
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 .
Annosus root disease also causes stem decay .
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 .
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 . At the time of logging, stump removal to reduce
innoculum in the soil is useful in preventing further contamination
. Borax application can be part of timber sales contracts when this
treatment is considered appropriate . 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 .
Armillaria (Armillaria ostoyae) is often a secondary pathogen of trees
infected with annosus root disease . 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 . Shoestring rot (Armillaria mellea) is also
detrimental to Pacific silver fir .
Fungi found in advance regeneration of Pacific silver fir are Indian
paint fungus (Echinodontium tinctorium) and Stereum sanguinolentum .
Indian paint fungus has been located on healthy stems and encased branch
piths of suppressed Pacific silver fir. Decay is commonly found near
wounds . Infection sites include small diameter branch stubs between
50 and 60 years of age . Indian paint fungus has a dormant phase,
which occurs when wounded tissues heal . When trees receive a new
injury, the fungus resumes growth . Indian paint fungus is most
easily recognized by the presence of conks or slow decay in old large
wounds . Stand rotation should be 150 years or less and wound
reduction activities should be practiced . Filip and Schmitt 
discuss color recognition of Indian paint fungus and planning and
Pacific silver fir is moderately susceptible to laminated root rot
(Phellinus weirii), which creates forest patches of damaged or dead
trees when abundant . 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 .
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 .
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
. 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 . 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 . 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 . 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 .
Pacific silver fir is a secondary host for dwarf mistletoe (Arceuthobium
tsugense and Arceuthobium abietinum) . 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 . Ruth  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 .
Cultivars, improved and selected materials (and area of origin)
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.
Relevance to Humans and Ecosystems
Value for rehabilitation of disturbed sites
Pacific silver fir is a good choice among tree species for planting in
watersheds and locations with large amounts of mountain snowpack
[22,24,26,41]. It is also well suited for developments such as
campgrounds and trails .
The dense growth of Pacific silver fir provides hiding, cover, and
thermal protection for wildlife .
Importance to Livestock and Wildlife
Old-growth stands provide good mountain goat habitat . Northern
spotted owls are dependent on the availability of old-growth stands for
nest site selection and sufficient prey . Other species with a
preference for old-growth stands include Vaux's swift, fisher, western
red-backed vole, and Olympic salamander . Small nongame birds
prefer late seral or old-growth Pacific silver fir stands .
The seeds of Pacific silver fir are eaten by birds, rodents, and
squirrels [59,63]. Pacific silver fir is the least preferred of trees
browsed by elk .
Wood Products Value
has little odor or resin [14,26]. The wood is weak and has low
durability . The most common uses of Pacific silver fir are light
construction frames, subfloor, construction plywood, sheaths, container
veneer, and pulpwood [14,24,26]. As a "white wood", Pacific silver fir
is a major export to Japan for business construction . It is used
for Christmas trees and decorative greenery [14,24,26].
Other uses and values
component of recreational and wilderness areas .
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.
Abies amabilis, commonly known as the Pacific silver fir, is a fir native to the Pacific Northwest of North America, occurring in the Pacific Coast Ranges and the Cascade Range from the extreme southeast of Alaska, through western British Columbia, Washington and Oregon, to the extreme northwest of California. It is also commonly referred to as the white fir, red fir, lovely fir, amabilis fir, Cascades fir, or silver fir. It grows at altitudes of sea level to 1,500 metres (4,900 ft) in the north of the range, and 1,000–2,300 metres (3,300–7,500 ft) in the south of the range, always in temperate rain forest with relatively high precipitation and cool, humid summers. Common associate trees are Douglas fir and in the extreme southern area of its range, California buckeye.
It is a large evergreen coniferous tree growing to 30–45 metres (98–148 ft) (exceptionally 72 metres (236 ft)) tall and with a trunk diameter of up to 1.2 metres (3 ft 11 in) (exceptionally 2.3 metres (7 ft 7 in)). The bark on younger trees is light grey, thin and covered with resin blisters. On older trees, it darkens and develops scales and furrows. The leaves are needle-like, flattened, 2–4.5 centimetres (0.79–1.77 in) long and 2 millimetres (0.079 in) wide by 0.5 millimetres (0.020 in) thick, matte dark green above, and with two white bands of stomata below, and slightly notched at the tip. The leaf arrangement is spiral on the shoot, but with each leaf variably twisted at the base so they lie flat to either side of and above the shoot, with none below the shoot. The shoots are orange-red with dense velvety pubescence. The cones are 9–17 centimetres (3.5–6.7 in) long and 4–6 centimetres (1.6–2.4 in) broad, dark purple before maturity; the scale bracts are short, and hidden in the closed cone. The winged seeds are released when the cones disintegrate at maturity about 6–7 months after pollination.
Pacific Silver Fir is very closely related to Maries' Fir A. mariesii from Japan, which is distinguished by its slightly shorter leaves (1.5–2.5 centimetres (0.59–0.98 in)) and smaller cones (5–11 centimetres (2.0–4.3 in) long).
The wood is soft and not very strong; it is used for paper making, packing crates and other cheap construction work. The foliage has an attractive scent, and is sometimes used for Christmas decoration, including Christmas trees.
It is also planted as an ornamental tree in large parks, though its requirement for cool, humid summers limits the areas where it grows well; successful growth away from its native range is restricted to areas like western Scotland and southern New Zealand.
- Farjon, A. (2013). "Abies amabilis". IUCN Red List of Threatened Species. Version 2013.2. International Union for Conservation of Nature. Retrieved 2 May 2014.
- Gymnosperm Database: Abies amabilis (2011)
- C.Michael Hogan (2008) Aesculus californica, Globaltwitcher.com, ed. N. Stromberg
- Flora of North America (2008) Vol. 2: Pinaceae
- Interactive Distribution Map of Abies amabilis
|Wikimedia Commons has media related to Abies amabilis.|
Names and Taxonomy
amabilis (Doug) ex. Loud. Pacific silver fir does not hybridize with
its true fir associates. Some morphological intermediates of Pacific
silver fir and subalpine fir (Abies lasiocarpa) have been reported ,
but these have proved not to be hybrids .