Index of Species Information
SPECIES: Pseudotsuga macrocarpa
Introductory
SPECIES: Pseudotsuga macrocarpa
AUTHORSHIP AND CITATION :
Howard, Janet L. 1992. Pseudotsuga macrocarpa. In: Fire Effects Information System, [Online].
U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station,
Fire Sciences Laboratory (Producer). Available:
https://www.fs.usda.gov/database/feis/plants/tree/psemac/all.html [].
ABBREVIATION :
PSEMAC
SYNONYMS :
NO-ENTRY
SCS PLANT CODE :
PSMA
COMMON NAMES :
bigcone Douglas-fir
bigcone spruce
bigcone Douglas-spruce
hemlock
false hemlock
desert fir
TAXONOMY :
The currently accepted scientific name of bigcone Douglas-fir is
Pseudotsuga macrocarpa (Vasey) Mayr [10,24]. There are no subspecies,
varieties, or forms [3,10]. Bigcone Douglas-fir and Douglas-fir
(Pseudotsuga menziesii) do not naturally hybridize because their ranges
do not overlap. They readily hybridize, however, under laboratory
conditions (see Management Considerations) [6].
LIFE FORM :
Tree
FEDERAL LEGAL STATUS :
No special status
OTHER STATUS :
NO-ENTRY
DISTRIBUTION AND OCCURRENCE
SPECIES: Pseudotsuga macrocarpa
GENERAL DISTRIBUTION :
Bigcone Douglas-fir occurs in mountains of southern California. It is
distributed from the Santa Ynez Mountains in eastern Santa Barbara
County and the Tehachapi Mountains of southwestern Kern County south to
Julian, San Diego County [3,18]. It is cultivated in Hawaii [33].
ECOSYSTEMS :
FRES21 Ponderosa pine
FRES28 Western hardwoods
FRES34 Chaparral - mountain shrub
STATES :
CA
BLM PHYSIOGRAPHIC REGIONS :
3 Southern Pacific Border
KUCHLER PLANT ASSOCIATIONS :
K005 Mixed conifer forest
K030 California oakwoods
K033 Chaparral
K034 Montane chaparral
K035 Coastal sagebrush
SAF COVER TYPES :
243 Sierra Nevada mixed conifer
245 Pacific ponderosa pine
246 California black oak
247 Jeffrey pine
248 Knobcone pine
249 Canyon live oak
255 California coast live oak
SRM (RANGELAND) COVER TYPES :
NO-ENTRY
HABITAT TYPES AND PLANT COMMUNITIES :
Low elevation (<3,500 feet [1,067 m]) bigcone Douglas-fir forest
communities are disjunct, surrounded by extensive areas of chamise
(Adenostoma fasciculatum) chaparral or coastal sage scrub [4,22,13]. In
canyon bottoms, bigcone Douglas-fir communities intergrade with riparian
forest [11]. From 3,500 to 4,500 feet (1,067-1,372 m), stands are more
widespread. Canyon live oak (Quercus chrysolepis) is sympatric with
bigcone Douglas-fir at these elevations. Together they form a
two-layered forest consisting of a subcanopy of canyon live oak and an
overstory of bigcone Douglas-fir [14,21]. Coulter pine (Pinus coulteri)
replaces bigcone Douglas-fir on more xeric sites at these elevations
[1]. From 4,500 to 5,500 feet (1,372-1,676 m), canyon live oak thins
and bigcone Douglas-fir becomes increasingly abundant. At higher
elevations, bigcone Douglas-fir decreases in importance and the bigcone
Douglas-fir forest type is gradually replaced by mixed evergreen forest.
Codominant species at higher elevations not listed as SAF Cover Types
include incense-cedar (Calocedrus decurrens), California white fir
(Abies concolor var. lowiana), singleleaf pinyon (Pinus monophylla),
sugar pine (P. lambertiana), and interior live oak (Q. wislizeni)
[18,32].
Publications listing bigcone Douglas-fir as a dominant or indicator
species are as follows:
Terrestrial natural communities of California [11].
Vegetation types of the San Bernardino Mountains [14].
Vegetation of the San Bernadino Mountains [21].
A vegetation classification system applied to southern California [26].
An introduction to the plant communities of the Santa Ana and San
Jacinto Mountains [32].
MANAGEMENT CONSIDERATIONS
SPECIES: Pseudotsuga macrocarpa
WOOD PRODUCTS VALUE :
There is no current commercial market for bigcone Douglas-fir wood due
to limited distribution and access [18]. It is heavy, hard, and fine
grained but not durable. There is less sapwood than heartwood, and the
latter contains pockets of resin. In the past, the wood was used
locally for fuel and lumber [29].
IMPORTANCE TO LIVESTOCK AND WILDLIFE :
Bigcone Douglas-fir stands provide habitat for black-tailed deer, black
bear, and various small animals. These trees provide preferred spring
habitat for black bear in the San Bernardino Mountains [18]. The seeds
are eaten by various rodents and birds [10].
PALATABILITY :
NO-ENTRY
NUTRITIONAL VALUE :
NO-ENTRY
COVER VALUE :
NO-ENTRY
VALUE FOR REHABILITATION OF DISTURBED SITES :
Bigcone Douglas-fir is used for watershed restoration. Radke and
McDonald [18] reported that the Los Angeles County Department of
Forestry has extensively planted the tree over a 50-year period for that
purpose. Survival rates are not detailed. Bigcone Douglas-fir is
recommended for reforestation of north-facing slopes within its range.
Seed collecting and processing methods are detailed in the literature
[25].
Trees planted on road cuts are often illegally harvested for use as
Christmas trees [12].
OTHER USES AND VALUES :
NO-ENTRY
OTHER MANAGEMENT CONSIDERATIONS :
Bigcone Douglas-fir populations are currently stable, with favorable
rates of reproduction [3]. The tree is being considered for more
extensive plantings in semiarid locales. Its favorable qualities
include resistance to drought, fire, insects, decay, and damage from
ozone [18,20]. The needles of older trees sometimes fade to yellow,
drop, and trees appear dead only to sprout with renewed vigor within 2
years. The reason is unknown, although drought or insects may be
possible causes [10].
Some bigcone Douglas-fir x Douglas-fir hybrids show promise for
outplanting on drier sites in the Douglas-fir region [10,18]. These
hybrids produce wood of comparable quality to that of Douglas-fir
and have the drought tolerance of bigcone Douglas-fir [6].
BOTANICAL AND ECOLOGICAL CHARACTERISTICS
SPECIES: Pseudotsuga macrocarpa
GENERAL BOTANICAL CHARACTERISTICS :
Bigcone Douglas-fir is a native evergreen conifer from 50 to 100 feet
(15-30 m) in height and 22 to 62 inches (56-155 cm) in DBH. Its growth
form is straight and pyramidal. The deeply ridged bark is composed of
thin, woodlike plates separating heavy layers of cork [3,10]; bark of
trees over 40 inches (102 cm) in DBH is from 6 to 8 inches (36-64 cm)
thick [31]. Main branches are long and pendulous, spreading from 20 to
50 feet (6-15 m) [1,3,15,18,21]. Side branches are few. The needles,
from 0.8 to 1.2 inches (2-3 cm) long, are shed about every 5 years
[10,24]. Female cones are from 4 to 7 inches (10-18 cm) long [28,24].
Seeds are large and heavy, each having a short rounded wing [18]. Roots
are described as strong and spreading [18]. The largest known bigcone
Douglas-fir is 91 inches (231 cm) DBH, 173 feet (53 m) tall, and is
estimated to be from 600 to 700 years of age [10].
RAUNKIAER LIFE FORM :
Phanerophyte
REGENERATION PROCESSES :
Sexual: The male strobili of an individual tree usually sheds pollen
before female strobili open, preventing self-pollination [10]. Seed
production begins at about 20 years of age; full seed production occurs
at about age 40. Insect larvae destroy some immature seed. At times,
they will destroy most of the crop. Heavy seed crops are rare. Seeds
fall under the parent tree and only during high winds is wider seed
dissemination possible [18]. Rodents and birds play a minor role in
seed dispersal. Deer mouse, Merriam chipmunk, California ground
squirrel, and western grey squirrel consume considerable portions of the
seed crop [10]. Seed quality tends to be poor. In one laboratory test,
seeds given cold-stratification treatment for 28 days proved 31 percent
viable [18].
Seedbed requirements are broad. Seeds will germinate successfully on
bare mineral soil or deep litter, although some seedling mortality from
damping-off fungi occurs in deep litter. Germination is epigeal [18].
Bigcone Douglas-fir does not reproduce well where fires are frequent
[3,18]. It reproduces best in locales undisturbed for at least 50
years, where emergents are shaded by canyon live oak. Survival is low
on open sites unless soil remains moist, but seedlings surviving on
these open sites attain top growth more rapidly than shaded seedlings
[18,31]. With time, continuous shade becomes a liability. A span of 40
to 70 years commonly is required for bigcone Douglas-fir to penetrate
through 16.5- to 27-foot (5-9 m) overstories of canyon live oak.
Seedlings on higher elevation south or west slopes, however, enter the
sapling-size class within 3 to 5 years [10].
Vegetative: Vegetative reproduction occurs after injury. Bigcone
Douglas-fir does not sprout from the root crown, but intermediate-aged
trees will sprout from the bole. In the Santa Ana Mountains, coppice
sprouts developed in trees that were 5 to 45 inches (13-114 cm) in DBH
and 25 to 300 years old [3]. Pole- and sawtimber-sized trees often
regrow burned crowns (see Plant Response to Fire). Seedlings and
saplings appear to have this ability as well [23]. Sprouting in young
trees is not well documented, however. Some authorities claim that
seedlings and saplings are not usually capable of sprouting following
injury [14,18].
SITE CHARACTERISTICS :
Climate: Bigcone Douglas-fir grows in a mediterranean climate,
characterized by hot summers and wet, mild winters. Annual rainfall
during a 30-year period on a bigcone Douglas-fir site in the San Gabriel
Mountains averaged 30 inches (762 mm) and ranged from 10 to 49 inches
(254-1,245 mm).
Elevation: Bigcone Douglas-fir occurs between 2,000 and 8,000 feet (610
and 2,720 m) [10,24].
Soil and topography: Bigcone Douglas-fir grows in a wide variety of
soil types [10]. At low elevation, it occurs near streams in moist,
shaded canyons and draws where aspects are mostly north and east. At
elevations from 4,440 to 5,600 feet (1,350-1,700 m), aspects include
south- and east-facing slopes. At these elevations, bigcone Douglas-fir
also grows on sloping hillsides, ridges, and benches. At higher
elevations, it occurs on south and west aspects on all types of terrain.
The average angle of slope on which bigcone Douglas-fire grows is 34.5
degrees. Slope angles range from 2 to 90 degrees, although these
extremes are uncommon [3].
Plant associations: The number of plant associates in bigcone
Douglas-fir communities is usually small [14]. Common overstory
associates not listed under SAF Cover Types or Habitat Types and Plant
Communities include bigleaf maple (Acer macrophyllum), California bay
(Umbellularia californica), gray pine (Pinus sabiniana), and white
alder (Rhombus rhombifolia) [1,4,7,10,19]. Shrub associates include
bigpod ceanothus (Ceanothus megacarpus), red shank (Adenostoma
sparsifolium), Eastwood manzanita (Arctostaphylos glandulosa), toyon
(Heteromeles arbutifolia), white sage (Salvia apiana), black sage (S.
mellifera), purple sage (S. leucophylla), and California scrub oak
(Quercus dumosa) [5,10]. Ground cover is usually sparse and may include
California buckwheat (Eriogonum fasciculatum), wild onion (Allium spp.),
scarlet beardtongue (Penstemon ternatus), chainfern (Woodwardia
fimbriata), and western brackenfern (Pteridium aquilinium var.
pubescens [10].
SUCCESSIONAL STATUS :
Bigcone Douglas-fir seedlings are shade tolerant, while mature trees are
intolerant [18]. The bigcone Douglas-fir forest is a climax type. In
the absence of fire or other disturbance, bigcone Douglas-fir invades
and dominates surrounding chaparral and oak communities [19]. Chaparral
shrubs remain the dominant vegetation type of their zone because
succession is constantly interrupted by drought accompanied by fire.
Trees usually do not grow large enough during the fire-free period to
become fire resistant [3,13]. Return of bigcone Douglas-fir to
chaparral sites following disturbance probably requires centuries [14].
SEASONAL DEVELOPMENT :
Bigcone Douglas-fir undergoes the following seasonal development:
cone buds form: September to October [10]
pollination: early March to mid-April [18]
seed germination: March to May [10]
cones mature: August to September [18]
seed released: September to October {18}
needles fall: September to October [10]
FIRE ECOLOGY
SPECIES: Pseudotsuga macrocarpa
FIRE ECOLOGY OR ADAPTATIONS :
Bigcone Douglas-fir is one of only a few western conifers capable of
sprouting following fire. Mature trees sprout vigorously from the
branches and bole after burning. The trunk and main branches of bigcone
Douglas-fir have many dormant adventitous buds, which are insulated from
fire beneath thick bark. Fire or other damage to the tree stimulates
cell division and growth in these buds. Consequently, epicormic stems
grow from the axils of branches or from branch stubs along the trunk
from the middle or upper one-third of the crown [10,18].
Bigcone Douglas-fir growing at low elevation often escapes fire damage
because the mesic sites where it grows are not fire-prone [15].
Potential fuels at higher-elevation sites are sparse because understory
vegetation is killed as trees mature and canopies close [31]. Litter
layers of bigcone Douglas-fir forests are usually poorly developed due
to the paucity of herbaceous understory and the sparse fall of needles
from trees [14]. Survival of bigcone Douglas-fir is enhanced in rough
terrain such as talus gullies and rugged canyons; such topography often
impedes the momentum and intensity of spreading fires [23]. Rates of
deforestation by slope class range from 84 percent for slopes of less
than 10 degrees to 51 percent for slopes between 30 and 39 degrees. On
slopes greater than 40 degrees, bigcone Douglas-fir survival is 75
percent [22].
FIRE REGIMES :
Find fire regime information for the plant communities in which this
species may occur by entering the species name in the FEIS home page under
"Find Fire Regimes".
POSTFIRE REGENERATION STRATEGY :
Secondary colonizer - off-site seed
FIRE EFFECTS
SPECIES: Pseudotsuga macrocarpa
IMMEDIATE FIRE EFFECT ON PLANT :
Fire kills bigcone Douglas-fir seeds. Most authorities claim that
seedlings and saplings are killed by fire [10,14,18]. One study,
however, showed that small burned trees sprouted following a fire of
unreported severity in the Transverse Ranges [23]. The immediate effect
of fire on young trees is therefore unclear, but mortality rates
probably vary according to fire severity [22]. Pole- and
sawtimber-sized trees are fire resistant. Aerial photographs of burns
in the eastern Transverse Ranges show that 60 percent of bigcone
Douglas-fir escaped defoliation during the period from 1938 to 1975
[23]. An additional 15 percent were scorched but not killed.
Twenty-five percent of the trees were killed outright.
The branchlets of defoliated trees are usually killed. Large main
branches generally survive moderate-severity fire, but may be killed
when severely burned. Trunks of severely burned trees are often
protected from fatal damage by their thick bark [18]. Bigcone
Douglas-firs growing sympatrically with canyon live oaks suffer less
fire damage than other bigcone Douglas-firs. These oak seems to act as
a buffer against the intense heat of chaparral fires burning into the
bigcone Douglas-fir community [22,23].
DISCUSSION AND QUALIFICATION OF FIRE EFFECT :
NO-ENTRY
PLANT RESPONSE TO FIRE :
Most sprouting occurs on trees scorched by surface fire. Trees
subjected to crown fire rarely sprout [22]. Aerial photographs taken
over the Meyer and Bear Burns of the Transverse Ranges at postfire years
1 and 2 showed that scorched stands with persistent dead foliage
sprouted, but severely burned stands were killed. Field study of stands
in the Village Burn (severity unreported) near Mount Baldy in the
Transverse Ranges revealed sprouting in pole-sized trees and saplings as
small as 10 feet (3 m) in height. All sprouts died on a number of such
smaller individuals after postfire year 1, but other trees regained full
crowns within 2 to 3 years [23]. The seed-producing ability of bigcone
Douglas-fir is impaired for years [19].
Postfire natural regeneration generally takes decades. A survey of
Transverse Range burns showed natural regeneration was almost
nonexistent in recent burns. No offspring were found in burns less than
19 years old. Seedlings and saplings were most evident in burned areas
free of further fire for 50 or more years. Bigcone Douglas-fir probably
requires the development of an overstory before shade-tolerant seedlings
will establish. Seed dispersal into these shaded areas is usually a
reproductive barrier following stand-replacing fires where all potential
parent trees are killed. Long-distance seed dispersal is inefficient in
bigcone Douglas-fir [23].
DISCUSSION AND QUALIFICATION OF PLANT RESPONSE :
NO-ENTRY
FIRE MANAGEMENT CONSIDERATIONS :
Despite its ability to develop new crowns, bigcone Douglas-fir is not
favored by frequent fire. Repeated fire depletes energy reserves and
enlarges old wounds, and mortality is high in trees subjected to such
fire regimes [18]. Bolton and Vogl [3] speculate that trees subjected
to frequent fire loose their ability to sprout. In contrast to most
conifers, however, fire-damaged trees are usually free from bark beetle
attacks [10]. Bigcone Douglas-fir is adapted to a regime of long,
fire-free intervals [7]. Frequent fire increases the number and density
of the chaparral and woodland species in the spaces between bigcone
Douglas-fir trees [14]. Occasional circumstances of stand defoliation,
however, select in its favor because of its sprouting habit [23]. The
interfaces of chaparral and bigcone Douglas-fir forests are in constant
flux as environmental factors of fire, drought, precipitation, and
erosion assert themselves [32].
The desiccating Santa Ana foehn winds that sweep the Santa Ana and San
Jacinto mountains represent a fire danger to bigcone Douglas-fir trees.
Santa Ana winds are capable of carrying fire downward from upslope mixed
coniferous forests [28,32].
REFERENCES
SPECIES: Pseudotsuga macrocarpa
REFERENCES :
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