Associated Forest Cover
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fornecido por Silvics of North America
California red fir is a climax species nearly everywhere it is found. It
shares climax status with white fir at the upper limit of the white fir
zone, although at any given place California white fir (Abies concolor
var. lowiana) or red fir regeneration may predominate (9,33).
Throughout the Sierra Nevada, lodgepole pine (Pinus contorta) occupies
wet sites within red fir forests. In the south, dry sites are shared with
sugar pine (P. lambertiana), mountain hemlock (Tsuga
mertensiana), or incense-cedar (Libocedrus decurrens). Scattered
individuals of Jeffrey pine (Pinus jeffreyi), sugar pine, and
western white pine (P. monticola) are found in northern Sierra
Nevada forests and as far south as Yosemite in the southern Sierra Nevada
(32,33).
In the Coast Ranges of California, Shasta red fir frequently shares
dominance with noble fir (Abies procera) and is mixed with
mountain hemlock and Brewer spruce (Picea breweriana) at
elevations generally above 1850 m (6,100 ft). On high elevation
serpentine soils, Shasta red fir is occasionally found with the more
common foxtail pine (Pinus balfouriana), western white pine, and
Jeffrey pine (33).
From the southern Cascades north into Oregon and west into the
California Coast Ranges, Shasta red fir begins to lose its clear climax
status, perhaps as a result of taking on characteristics of noble fir,
which is never a climax species in the northern Cascades (9). Shasta red
fir is replaced successionally by white fir at the lower elevations and by
mountain hemlock at the upper. Major associated species include
Douglas-fir (Pseudotsuga menziesii var. menziesii), white
fir, western white pine, lodgepole pine, and mountain hemlock (9,33).
Red fir is found in seven forest cover types of western North America.
It is in pure stands or as a major component in Red Fir (Society of
American Foresters Type 207) (7), and also in the following types:
Mountain Hemlock (Type 205), White Fir (Type 211), Lodgepole Pine (Type
218), Pacific Douglas-Fir (Type 229), Sierra Nevada Mixed Conifer (Type
243), and California Mixed Subalpine (Type 256).
Brush and lesser vegetation are varied. Dense red fir stands on good
quality sites usually have no understory vegetation. In openings resulting
from tree mortality or logging, and under open stands on poor sites, many
species are possible depending on location (9,20,42). Currant or
gooseberry (Ribes spp.), pinemat manzanita (Arctostaphylos
nevadensis), and mountain whitethorn (Ceanothus cordulatus) are
the most commonly found brush species (9,20,21). Large brush fields can
dominate areas after severe fire. Fir eventually will reclaim these sites
as the climax species. With some combinations of low site quality, brush
species, and resident rodent population, however, reforestation can be
effectively delayed for decades. Small upland meadows are common in red
fir forests and provide habitats for a wide variety of sedges, grasses,
and forbs.
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Climate
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fornecido por Silvics of North America
Climate for the red fir zone can be classified in general as cool and
moist to cold and moist. It is relatively mild for high-elevation forests,
with summer temperatures only occasionally exceeding 29° C (85°
F) and winter temperatures rarely below -29° C (-20° F). One
notable climatic feature is a 4- to 5-month summer dry spell. Between
April (or May) and October, precipitation from scattered thunder-showers
is negligible. Almost all precipitation occurs between October and March,
with 80 percent or more as snow. Snowpack can exceed 4 m (13 ft) in the
Sierra Nevada, and snow can accumulate to more than 2 m (7 ft) in Oregon
and northwestern California (9,39). Total precipitation ranges from 750 to
1500 mm (30 to 60 in).
Best growth appears to be in areas that receive between 750 and 1250 mm
(30 and 49 in) of precipitation. Growth studies on Swain Mountain
Experimental Forest, in the southern Cascades of California, indicate that
California red fir grew best in years with unusually low precipitation (as
low as 38 percent of normal) (29). Low precipitation there usually means
early snowmelt and a longer growing season.
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Damaging Agents
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fornecido por Silvics of North America
Red fir is subject to damage from abiotic
agents, pathogens, insects, and animals. Little is known about the
tolerance of red fir to most abiotic aspects of the environment. Initial
survival of seedlings seems to be better under partial shade although
growth is best in full sunlight. The early advantage of shade may be
related to protection from temperatures in exposed duff and litter that
can frequently exceed 70° C (160° F) early in the growing season
(14).
Red fir appears to be more sensitive to drought than white fir or the
associated pines (26), even though over most of its range there may be no
precipitation for as long as 5 months during the summer. A tendency of red
fir to grow poorly where snowmelt water collects, as on mountain meadows,
indicates a moderate sensitivity to high soil moisture content during the
growing season (8).
Frosts can occur any month of the year, but damage to red fir is minimal
and significant only on Christmas trees. Red fir is more frost resistant
than white fir and about equal to Jeffrey pine (19).
The importance of mechanical injury increases as intensive management of
dense young red fir stands increases. Studies in Oregon and California
show that conventional logging techniques used for thinning or partial
cutting damaged 22 to 50 percent of the residual stand. Seventy-five
percent of these wounds were at ground level where infection by a
decay-causing fungus is almost certain (2). Volume losses by final harvest
can be considerable, although the amount varies greatly from place to
place, perhaps due to type and frequency of wounds (2).
Among pathogens, one parasitic plant causes major damage. Red fir dwarf
mistletoe (Arceuthobium abietinum f. sp. magnificae) is common
throughout the range of red fir and infests 40 percent of the stands in
California (34). Heavily infected trees suffer significant growth losses
and are subject to attack by Cytospora abietis, a fungus that
kills branches infected by dwarf mistletoe and further reduces growth.
Because of reduced vigor, infected trees are more susceptible to bark
beetle attack and other diseases (34). Heart rots, entering through open
mistletoe stem cankers, increase volume loss directly and mortality
indirectly through stem breakage. Recent unpublished research suggests
that losses from bole infection may be of minimal consequence in
well-managed second-growth true fir stands (35).
Changes in wood structure in large stem bulges resulting from dwarf
mistletoe infections reduce strength of lumber produced. Current lumber
grading practices, however, are not adequate to identify the affected wood
(40).
Dwarf mistletoe need not be a problem in young managed stands because
four factors make damage subject to silvicultural control. Red fir can be
infected only by red fir dwarf mistletoe which, in turn, can parasitize
only one other fir, noble fir. Small trees (less than 1 m [3.3 ft] tall)
are essentially free from infection even in infested stands. Infected
young firs, free from new overstory infection, outgrow the spread of
mistletoe if height growth is at least 0.3 m (1 ft) per year, and losses
from bole infections are expected to be minimal in managed, young-growth
stands (34,35). Silvicultural practices that can significantly reduce the
impact of dwarf mistletoe include removal of an infected overstory before
natural regeneration exceeds 1 m (3.3 ft) in height, and stocking control
to promote rapid height growth. Different species can be favored in the
overstory and understory of mixed stands during thinnings or partial
cutting. Sanitation of stand edges adjacent to regeneration areas and
planting a non-host species (such as white fir adjacent to a red fir
stand) appropriate to the site can prevent infection from overstory trees.
Fir broom rust (Melampsorella caryophyllacearum) is abundant in
the central and southern Sierra Nevada. This disease primarily affects
branches but can infect trunks. It can cause spike tops and loss of crown
and provide an entry court for heart rots. Fir broom rust can occasionally
kill trees, especially seedlings and saplings (4).
Annosus root rot (Heterobasidion annosum) is present in all
conifer stands and may become a major disease problem as red fir is
increasingly and intensively managed. Infection is spread from tree to
tree by root contact, forming disease pockets in the stand that slowly
expand. Infection of freshly cut stumps or new wounds by aerially spread
spores creates new infection centers that do not become evident until 10
to 20 years after infection. Annosus root rot does not usually kill red
fir directly, but root damage results in considerable moisture stress and
loss of vigor. The loss of vigor predisposes the tree to attack by bark
beetles, notably Scolytus spp. Direct damage resulting from
infection is restricted primarily to heart rot of butt and major roots,
leading to windthrow and stem breakage (4). Some degree of control is
available through use of borax to prevent infection by Heterobasidion
annosum in freshly cut stumps.
Other heart rots of major significance include the yellow cap fungus
(Pholiota limonella) and Indian paint fungus (Echinodontium
tinctorium). These fungi cause major losses in old-growth trees. Young
trees are generally not affected because they have so little heartwood.
Yellow cap fungus tends to be a more severe disease in California, and
Indian paint fungus is more severe in Oregon. Yellow cap fungus generally
enters through basal wounds. Rot can extend 15 to 18 m (50 to 60 ft) up
the trunk. Indian paint fungus probably infects red fir in the same manner
as it does western hemlock (2). The fungus enters through branchlets less
than 2 mm (0.08 in) in diameter and can remain dormant for as long as 50
years before being activated by injury or stress (6). Dead or broken tops
are other points of entry for Indian paint fungus. The resulting rot is
located in the upper bole and may extend to the ground. Open dwarf
mistletoe cankers serve as entry courts for several decay fungi. None of
the heart rots kill directly but predispose the tree to stem breakage. No
effective control is known for decay fungi, except possibly Heterobasidion
annosum, other than avoiding as much root, stem, and top damage as
possible during stand management (4).
Insects from five genera attack red fir cones and seeds. Losses can be
significant. Cone maggots (Earomyia spp.) cause the most damage.
Several chalcids (Megastigmus spp.) and cone moths (Barbara
spp. and Eucosma spp.) can occasionally cause heavy local
damage to seed crops, especially in poor seed years (13).
Cutworms (Noctuidae) can be a problem in nurseries and may be
especially damaging in natural regeneration areas. Cutworms were
responsible for more than 30 percent of the seedling mortality in a study
on Swain Mountain Experimental Forest in California (14).
The white fir needleminer (Epinotia meritana) is the only
foliage feeder of consequence on established red fir. Even during outbreak
phases the damage caused is apparently minor and temporary (13).
The most severely damaging insect pest on red fir is the fir engraver
(Scolytus ventralis). This bark beetle is found throughout the
range of red fir and causes severe damage nearly everywhere. Losses under
epidemic conditions can be dramatic. Anything that reduces tree vigor-Annosus
root disease, dwarf mistletoe, Cytospora canker, overstocking,
drought, or fire damage-increases susceptibility to fir engraver attack.
Several other species of bark beetles (Scolytus spp., Pseudohylesinus
spp.), the round-headed fir borer (Tetropium abietis), and the
flat-headed fir borer (Melanophila drummondi) frequently join in
attacking and killing individual trees. In epidemic conditions, however,
mortality is caused primarily by the fir engraver. Maintenance of stand
health and vigor is the only known control (13).
Locally, small rodents can cause significant loss of seed and
occasionally girdle seedlings. Squirrels cut and cache cones. Pocket
gophers limit regeneration in many areas, particularly clearcuts, by
feeding on fir seedlings during winter and spring. Pocket gophers in
combination with meadow voles and heavy brush can prevent conifer
establishment for decades. Where gopher populations are high, damage to
root systems of mature trees can be extensive, although not often
identified. In extreme conditions, winter and spring feeding at root
crowns can kill trees up to at least 94 cm (37 in) in diameter at breast
height (23). Direct control is difficult and expensive. Indirect control
by habitat manipulation offers some possibilities.
Spring browsing of succulent growth by deer can retard height growth for
many years. Normally, trees are not killed and in most instances can grow
rapidly once browsing pressure is removed. In managed stands, reduced
height growth can result in significant production loss. Red fir may be
damaged less by deer or rabbit feeding than white fir.
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Flowering and Fruiting
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Red fir is monoecious. Male strobili
(cones) are small-generally less than 1.6 cm (0.6 in) long-deep
purple-red, and densely clustered on the underside of 1-year-old twigs
about midcrown. Female cones are borne erect on 1-year-old branches in the
uppermost crown, although both male and female cones are occasionally
found on the same branch. California red fir flowers from May to June,
with pollen shed and fertilization in late May through June. Shasta red
fir flowers from middle to late June in southwestern Oregon. Populations
in the Coast Ranges of northwestern California probably follow the same
schedule. Seeds begin to reach maturity in mid-August and the ripening
process continues up to time of seedfall.
Cones are large, 15 to 23 cm (6 to 9 in) long, 5 to 8 cm (2 to 3 in) in
diameter, and oblong cylindric in shape. Shasta red fir bracts are longer
than the cone scales and are easily visible on the surface of a mature
cone. California red fir bracts are shorter than the cone scales and are
not visible on an intact cone. Cones of both varieties are brown when
mature and have specific gravities of about 0.75 (8,27,28,36).
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Genetics
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In the northern part of its range, California red fir appears to merge
and hybridize with noble fir, a northern species with morphological and
ecological similarities. Bracts that extend beyond the scales on mature
cones are characteristic of noble fir. North of Mount Lassen, red fir has
similar exserted bracts. South of Mount Lassen, bracts on red fir are
shorter than the scales and are not visible on intact mature cones.
Changes in seed weight, cotyledon number, and cortical monoterpenes in
both species indicate a broad transition zone between latitudes 40°
and 44° N. Similarity with noble fir increases to the north and west
(41). The two species can be artificially cross-pollinated with no
apparent difficulty as long as red fir is the female parent. Success is
reduced by more than 70 percent when red fir is the male parent (5,36).
Discussion continues about the relationship of California red fir, Shasta
red fir, and noble fir; however, the fact that exserted bracts also appear
on a large southern Sierra Nevada population of red fir that has
characteristics in common with both California red fir and Shasta red fir
only adds to the controversy (41).
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Growth and Yield
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Red fir volume production is impressive.
Normal yield tables for unmanaged stands indicate that a 160-year-old
stand on a high site- 18 m (60 ft) at 50 years-can carry 2320 m³/ha
(33,150 ft³/acre). Average sites- 12 m (40 ft) at 50 years-carry 1470
m³/ha (21,000 ft³/acre) at the same age. These volumes are
possible, at least in part, because of the stand density that red fir can
maintain. Basal areas on high sites can be well in excess of 126 m²/ha
(550 ft²/acre) and on average sites in excess of 96 m²/ha (420
ft²/acre). In addition, the normal yield tables indicate that stand
mean annual increment continues to increase until age 140 (37). Less ideal
stands will support slightly less basal area, and mean annual increment
may culminate sooner. The capacity of the species to respond to decreases
in stand density is impressive, even at the advanced age of 100 years. In
stands of white and red fir thinned to 50 percent of their basal area, the
remaining trees increased growth sufficiently that overall stand growth
was not significantly reduced (30).
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Reaction to Competition
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fornecido por Silvics of North America
Although red fir grows best in full
sunlight, it can survive and grow for long periods in relatively dense
shade. Red fir's tolerance of shade appears to be less than that of
mountain hemlock, slightly less than that of white fir and Brewer spruce,
but greater than that of all of its other associates. Red fir's capacity
to maintain significantly more foliage under shade than white fir suggests
that the tolerance difference between them is marginal (1). It is most
accurately classed as tolerant of shade. Red fir seedlings are slightly
more hardy in full sun than white fir seedlings but become established
most easily in partial shade (14,26).
Red fir can carry large basal areas per unit area and maintain high
growth rates for an unusually long time, partly as a result of its shade
tolerance. As an understory tree it can survive more than 40 years of
suppression and, unless diseased, respond to release by increasing growth
dramatically. Time until growth accelerates depends on crown condition.
Even mature dominants can respond to large reductions in stand density.
Seed production on mature dominants can increase after release
(16,25,26,38).
Natural regeneration of red fir can be achieved using shelterwood and
seed tree cuttings. Clearcuts work as long as the size of the opening
perpendicular to the wind does not exceed seed dispersal distances. Site
preparation is important (19). Recent developments in nursery and handling
technologies, including manipulation of root regeneration capacity and
identification of necessary storage and transportation conditions, make
artificial planting commercially practical. Access to planting sites is
commonly difficult in the Sierra Nevada because of heavy snowpacks that
last until June and later.
It is theoretically possible to manage several age classes in a stand
because of the species' shade tolerance. However, the ability of red fir
to support high growth rates for extended periods in dense, even-aged
stands makes even-aged management the likely choice on most sites. Patch
cuttings of small areas- 0.2 to 2.2 ha (0.5 to 5.5 acres)- work well where
larger regeneration cuts are undesirable for visual or environmental
reasons.
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Rooting Habit
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Root systems of mature forest trees, including
red fir, have not been the subject of much research. What little is known
has been gleaned from observations of windthrown trees. Mature red fir
rooting habit appears to be fairly adaptable, deep and intensive where
soil conditions pen-nit or shallow and widespread where rocks or seasonal
water tables limit effective soil depth. There is no strong tendency to
maintain a single, deep taproot, although rapid development of a strong
taproot is critical for survival of new germinants in the dry summer
climate.
On at least some sites, however, saplings and poles have large-diameter,
carrot-like taproots extending more than 1 m (3 ft) deep, with very poor
lateral root development in the upper 30 cm (12 in). This condition has
been found on young pumice soils overlying an old, buried profile.
Periodic lack of fall snow cover exposes the soil to subzero temperatures
and increased temperature fluctuations. Under these conditions pumice
soils are subject to ice crystal formation and severe frost heaving. Fine
lateral roots are probably killed by mechanical damage during ice
formation and frost heaving or, perhaps, by low temperatures.
Red fir is susceptible to windthrow after partial cutting, especially
when marginal codominant and lower crown classes are left as the residual
stand (15). Root diseases contribute significantly to lack of
windfirmness.
Root grafting between red fir trees is indicated by the occasional
presence of living stumps (8).
The effects of mycorrhizal associations are beginning to be explored.
Early information indicates that these root-fungi relationships are
significant in establishment and early growth, especially on poor sites
(3).
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Seed Production and Dissemination
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California red fir can begin
producing seed when only 35 to 45 years old; Shasta red fir produces seed
when about 5 years younger (36). Heavy seed crops-adequate for reliable
regeneration-are produced every 1 to 4 years by California red fir (22)
and about every third year by Shasta red fir (12).
Seeds are wind-disseminated after cones disintegrate on the trees in
late September to mid-October and are dispersed primarily by the
prevailing southwesterly winds (14).
In an exceptional year, seed production for both varieties can exceed
1.4 million per ha (570,000/acre) within a stand and along the edge of an
opening (11, 14). The more frequent "good to heavy" crops may
only reach 10 percent of that value. Seed production varies with tree age,
size, and dominance. The best, most reliable producers are mature, healthy
dominants. Immature fir can produce heavy seed crops, but production is
more erratic than that of mature trees (18). California red fir seeds
average 14,110/kg (6,400/lb). Shasta red fir seeds tend to be smaller and
average 16,095/kg (7,300/lb) (36).
Because cones are borne almost exclusively in the uppermost crown, any
top damage caused by insects, diseases, or mechanical agents (for example,
wind and snow) directly reduces cone production. Large old trees are prone
to such damage. Trees which have lost their tops, however, can frequently
develop new terminals and resume cone bearing.
Studies in California indicate that mature dominants along the edge of a
clearcutting produce up to twice as many cones as similar trees in closed
stands (18). Regeneration data, also from California, indicate that mature
trees left in seed tree or shelterwood cuts increase seed production (25).
The number of Shasta fir seeds falling into a clearing decreases rapidly
with distance from the stand edge. At a downwind distance equal to about 2
to 2.5 times tree height, seedfall is nearly 10 percent of the stand edge
value (11). Dispersal of the heavier California red fir seeds is generally
limited to 1.5 to 2 times tree height (13). Germination rates in standard
tests are relatively low for both varieties, generally less than 40
percent (36). Even lower field germination rates (5 percent or less) can
produce adequate regeneration.
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Seedling Development
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Red fir seeds germinate in the spring
immediately after snowmelt or in, on, and under the snow (10,14).
Germination is epigeal. Seeds that germinate several centimeters above
ground in the snowpack rarely survive. Seeds that fall before the first
permanent snows of winter, therefore, are more effective in producing
seedlings. Initial survival is best on mineral soil, perhaps, as in white
fir, because presence of appropriate mycorrhizal-forming fungi is
increased in the absence of organic layers (3).
Openings created in mixed red and white fir stands in both northern and
southern Sierra Nevada tend to regenerate more readily to red fir. Fifty
to 80 percent of the regeneration will be red fir, even when the
surrounding stand is dominated by white fir (25,32).
Two long-standing assumptions-that red fir growth is extremely slow for
the first 20 to 30 years and that snow damage limits height growth-do not
appear valid. Recent evidence indicates that beyond the first 5 years,
slow growth is not inherent (16,24) and snow damage is significant for
relatively few seedlings (17). Extended periods of slow early growth
appear to result from environmental conditions, such as prolonged shading
and browse damage.
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Soils and Topography
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Red fir is found at high elevations on mountain ranges that continue in
active formation. The soils on which it grows are therefore young and fall
into four orders, Entisols, Inceptisols, Alfisols, and Spodosols. They are
classified as mesic to frigid or cryic, with mean annual soil temperatures
(at 50 cm; 20 in) between 0° and 15° C (32° and 59°
F). All soils but the Alfisols tend to be light colored, shallow, with
minimal or no horizon development, and low in cation exchange capacity and
base saturation. Most are classified in some degree as xeric because of
the long summer dry period. Horizon development is relatively poor even in
the mesic Alfisols. The Spodosols are developed poorly without a true
leached A horizon because of inadequate warm season precipitation. In the
Cascades, red fir is occasionally found on pumice deposits overlying old
soils.
Decomposition of needles and other litter tends to be slow in the wet
winter, dry summer climate. Organic material collects on the surface where
it forms dense black mats from 2 to 8 cm (0.75 to 3.0 in) or more thick
(8).
Tree growth and stand development are best on the deeper soils
associated with glacial deposits or Pleistocene lake beds. On steep slopes
where soils are shallowest, stands are open and tree growth poor. On
moderate to gentle slopes and flat ground where water does not collect,
stands are closed with no understory or herbaceous vegetation (8).
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Special Uses
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Red fir is a general, all-purpose construction-grade wood used
extensively as solid framing material and plywood. Good quality young red
fir, known as "silvertip fir" from the waxy sheen on their
dense, dark-green needles, bring top prices as Christmas trees. These
trees are cultured in natural stands and plantations where early growth is
slower than most species used as Christmas trees, and some individuals are
cultured for as long as 11 years before harvest.
Detailed and exact wildlife censuses for large areas do not exist and
any listing of species numbers associated with a major forest type is an
approximation. There are, however, about 111 species of birds found in the
red fir type of California, 55 of which are associated primarily with
mature forests. Perhaps because of the dense nature of most true fir
forests, there are only about 52 species of mammals commonly present and
only 6 of those are generally associated with mature forests. Few
reptilian species are found at the high elevations and only four are
generally present in the red fir type.
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Vegetative Reproduction
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Under natural conditions red fir does
not reproduce vegetatively either by sprouting or layering. Vegetative
propagation from cuttings is possible but the techniques currently
available are at an early stage of development.
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Distribution
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In California and southern Oregon, red fir is limited to high
elevations. Its range extends from the central and southern Cascade
Mountains of Oregon southward to Lake County in the Coast Ranges of
northwest California and Kern County in the southern Sierra Nevada, from
about latitude 43° 35' to 36° 50' N. Red fir is found outside
these states only along the western border of Nevada, a few kilometers
east of Mount Rose in Washoe County (8,9,22).
Lower elevational limits begin at 1620 to 1800 m (5,300 to 5,900 ft) in
the Cascade and Siskiyou Mountains and increase toward the south, reaching
to 2130 m (7,000 ft) in the southern Sierra Nevada. Upper elevation limits
also increase to the south, beginning at 2010 to 2190 m (6,600 to 7,200
ft) in the Cascade and Siskiyou Mountains, and reaching 2740 m (9,000 ft)
in the southern Sierra Nevada. Red fir can be found growing at lower
elevations in canyons and other protected places where significant cold
air drainage keeps soil and air temperatures low (31). In the California
Coast Ranges, Shasta red fir is found generally between 1400 and 1830 m
(4,600 to 6,000 ft) (8,9,33).
- The native range of California red fir.
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Brief Summary
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fornecido por Silvics of North America
Pinaceae -- Pine family
Robert J. Laacke
Red fir (Abies magnifica) dominates large areas of high country
that are a major source of water, especially in California. For this
reason it has long been an important forest tree. Only recently has red
fir assumed significance as an unusually productive source of wood (17).
Relatively little detailed, coherent silvical information is available,
however.
North of Mount Lassen in northern California, red fir shows
morphological and perhaps ecological characteristics that have led to its
common designation as Shasta red fir (A. magnifica var. shastensis)
(8,9,22). Here, the varieties are referred to collectively as red fir
and are identified only when differences warrant.
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