BOTANICAL AND ECOLOGICAL CHARACTERISTICS
SPECIES: Pseudotsuga menziesii var. menziesii | Coast Douglas-Fir 



GENERAL BOTANICAL CHARACTERISTICS : 
Coast Douglas-fir is a large, coniferous, evergreen tree.  Adapted to a
moist, mild climate, it grows bigger and more rapidly than the inland
variety.  Trees 5 to 6 feet (150-180 cm) in diameter (150-180 cm) and
250 feet (76 m) or more in height are common in old-growth stands [31].
These trees commonly live more than 500 years and occasionally more than
1,000 years [31].  Old individuals typically have a narrow, cylindric
crown beginning 65 to 130 feet (20-40 m) above a branch-free bole [20].
Self-pruning is generally slow and trees retain their lower limbs for a
long period.  Young, open-grown trees typically have branches near the
ground.  It often takes 77 years for the bole to be clear to a height of
17 feet (5 m) and 107 years to be clear to a height of 33 feet (10 m)
[31].  In wet coastal forests, nearly every surface of old-growth coast
Douglas-fir is covered by epiphytic mosses and lichens [20].

This tree's rooting habit is not particularly deep.  The roots of young
coast Douglas-fir tend to be shallower than roots of the same aged
ponderosa pine, sugar pine, or incense-cedar [54].  Some roots are
commonly found in organic soil layers or near the mineral soil surface
[60].  The bark on young individuals is thin, smooth, gray, and contains
numerous resin blisters.  On mature trees the bark is thick (4 to 12
inches [10-30 cm]) and corky [33].  Foliage consists of yellowish-green,
1-inch-long (2.5 cm) needles spirally arranged around the branchlets.
Pendent, 2- to 4-inch-long (5-10 cm) cones are located primarily in the
upper crown.


RAUNKIAER LIFE FORM : 
   Phanerophyte


REGENERATION PROCESSES : 
Cone and seed production:  Appreciable seed production begins at 20- to
30-years of age in open-grown coast Douglas-fir.  Seed production is
irregular.  Over a 5- to 7-year period, stands usually produce one heavy
crop, a few light or medium crops, and one crop failure [31].  Even
during heavy seed crop years, only about 25 percent of trees in closed
stands produce an appreciable number of cones [31].  Each cone contains
26 to 50 seeds [59].  Seed size varies greatly; average number of
cleaned seeds per pound varies from 32,000 to 40,000 (70,400-88,000/kg)
[59].  Seeds from the northern portion of coast Douglas-fir's range tend
to be larger than seed from the south [31].

Dispersal:  Douglas-fir seeds have a relatively large single wing and
are dispersed by wind and gravity.  Most fall within 110 yards (100 m)
of the parent tree, but some may travel much greater distances.  On rare
occasions, sites more than 0.5 mile (0.8 km) from a seed source have
reseeded after cutting [19].  Small amounts of seeds are also dispersed
by mice, chipmunks, and squirrels.

Seed predation:  Caching of Douglas-fir cones by the Douglas squirrel,
and foraging for seeds on the ground by chipmunks, mice, voles, and
birds reduces seed quantity considerably [35].  Insect damage varies
greatly but can be profound.  Insects may destroy less than 5 percent of
a large seed crop, but a high percentage of seeds produced in small
crops are often destroyed [67].

Viability:  Commonly, less than 40 percent of coast Douglas-fir seeds
are sound [31].  Seed soundness decreases during poor seed crop years.
During poor cone production years in northwestern California, old-growth
Douglas-fir seed soundness averaged 18 percent, while seed soundness was
53 percent in a 49-year-old western Washington stand [67].  Seeds remain
viable for only 1 or occasionally 2 years [35].

Germination and seedling establishment:  Germination and seedling
establishment are best on mineral soil seedbeds.  Organic seedbeds
generally become too hot and dry during the summer for Douglas-fir
seedlings to survive, but seedlings may tolerate a light litter layer if
the seedbed remains moist [53,76].  Natural stocking of Douglas-fir
following timber harvest is usually highest where site preperation
measures, such as broadcast burning or mechanical scarification, are
used to expose mineral soils [76].  First year seedlings survive and
grow best in partial shade [31,35].  Shading is especially important on
southerly aspects, where it lessens seedbed heating and drying.
Seedling survival and growth on severe sites is generally best in 50
percent shade [76].  Douglas-fir cannot survive, however, under the
dense shade cast by heavy logging slash or competing understory
vegetation [53].  Once established, seedlings require full sunlight.


SITE CHARACTERISTICS : 
Coast Douglas-fir is the most dominant tree species in the Pacific
Northwest, occurring in nearly all forest series, from near sea level
along the coast to above 5,000 feet (1,524 m) in the Cascades.  It
competes well on most parent materials, aspects, and slopes [6].  Pure
stands are common north of the Umpqua River in Oregon [31].

Elevation:  In Washington and Oregon, Douglas-fir grows from near sea
level to over 5,000 feet (1,524 m).  In the southern Oregon Cascades and
in the northern Sierra Nevada, it is generally occurs between 2,000 and
6,000 feet (609-1,829 m).  In the southern Sierra Nevada it is occurs up
to 7,500 feet (2,286 m) [31].

Soils:  Douglas-fir grows on a wide variety of parent materials and soil
textures but grows best on well-aerated, deep soils with a pH between 5
and 6 [31].  It grows poorly on oligotrophic soils where calcium,
magnesium, nitrogen, phosphorus, and potassium are in low supply [39].

Frost:  Coastal Douglas-fir will not tolerate frost below 14 degrees
Fahrenheit (-10 deg C) for more than a week, even if the ground is well
protected against freezing by snow [39].

Tree Associates:  See SAF Cover Types and Habitat Types And Plant
Communities for overstory associates.  

Understory Associates:  Shrub associates in the central and northern
part of coast Douglas-fir's range include vine maple (Acer circinatum),
salal, Pacific rhododendron (Rhododendron macrophyllum), Oregon grape
(Berberis nervosa), red huckleberry (Vaccinium parvifolium), and
salmonberry (Rubus spectabilis).  In the drier, southern portion of its
range shrub associates include California hazel (Corylus cornuta var.
californica), oceanspray (Holodiscus discolor), creeping snowberry
(Symphoricarpos mollis), western poison-oak (Toxicodendron
diversilobum), ceanothus (Ceanothus spp.), and manzanita (Arctospaphylos
spp.) [31].


SUCCESSIONAL STATUS : 
Coast Douglas-fir is a major, long-lived seral dominant of low and
middle elevation moist forests from southwestern British Columbia to
northwestern California [21].  In these forests it is shade intolerant
and requires stand-destroying disturbance (wildfire, logging, extensive
windthrow) to initiate a new cohort of seedlings.  Today, estensive
areas of western Washington and Oregon are covered by seral, nearly pure
stands of Douglas-fir that seeded in rapidly following logging and
wildfire [21].  This species is extremely long-lived.  Stands 350 to 750
years old are subclimax and may contain a significant component of
Douglas-fir for several more centuries [20].  Without disturbance, these
stands will eventually give way to shade-tolerant associates such as
western hemlock, western redcedar (Thuja plicata), and Pacific silver
fir, but it may take 1,000 or more years for Douglas-fir to be fully
replaced [20,21].  This longevity allows Douglas-fir to persist until
the next disturbance, ensuring a seed supply for postdisturbance
establishment.

On drier sites, Douglas-fir is more shade-tolerant and may assume climax
dominance.  It is more shade tolerant than ponderosa pine, sugar pine,
western white pine (Pinus monticola), lodgepole pine (P. contorta),
incense cedar, and noble fir (Abies procera) but less shade tolerant
than white fir [36,54].  In the white fir zone of northern California,
Douglas-fir is seral, but as sites become drier it may assume climax
dominance [63].  Similarly, it is a seral component in moist redwood
(Sequoia sempervirens) forests, but as sites become drier farther
inland, redwood gives way to mixed evergreen forests codominated by
Douglas-fir, Pacific madrone, and tanoak [64].

In the Cascades, Douglas-fir is seral throughout most of the western
hemlock zone.  However, it achieves climax on lower elevation hot and
dry sites, which are typically southeast- to west-facing slopes [2,15].


SEASONAL DEVELOPMENT : 
The phenology of coast Douglas-fir is influenced greatly by latitude and
elevation.  Flowering occurs during March and April in the warmer parts
of its range and as late as May or June in colder areas [31].  The cones
mature in one growing season and are normally ripe by late August or
early September.  Cones open as they dry, so wet fall weather can delay
seedfall.  Approximately 70 to 90 percent of the seeds are dispersed by
November 1, with the remainder falling during winter [59].  Cones remain
on the tree 1 or more years after seed dispersal [59].

Related categories for Species: Pseudotsuga menziesii var. menziesii | Coast Douglas-Fir