BOTANICAL AND ECOLOGICAL CHARACTERISTICS
SPECIES: Sequoiadendron giganteum | Giant Sequoia 



GENERAL BOTANICAL CHARACTERISTICS : 
Giant sequoias grow to an average height of 250 to 275 feet (76-84 m)
and 15 to 20 feet (5-7 m) d.b.h.  Record trees have been reported to be
310 feet (95 m) in height and 35 feet (11 m) d.b.h.  The leaves are
awl-shaped, sessile, and persistent.  Seed cones are 2 to 3 inches (5-8
cm) long, serotinous, persistent, and may remain green up to 20 years.
Bark is fibrous, furrowed, and may be 2 feet (0.6 m) thick at the base
of the columnar trunk [6,10].  The oldest known giant sequoia based on
ring count is 3,200 years old [10].


RAUNKIAER LIFE FORM : 
   Phanerophyte


REGENERATION PROCESSES : 
Giant sequoia regenerates primarily by seed, although occasionally it
may reproduce naturally by vegetative methods.  Giant sequoias up to
about 20 years of age may produce stump sprouts subsequent to injury.
Giant sequoia of all ages may sprout from the bole when old branches are
lost to fire or breakage.  Cuttings from juvenile donors root quickly
and in high percentages (up to 94 percent) [10].

Flowering and fruiting:  Giant sequoia is monecious; male and female
cone buds form during late summer.  Pollination takes place between the
middle of April and May.  Fertilization usually occurs in August when
the cones are nearly full-sized.  Embryos develop rapidly during the
next summer and reach maturity at the end of the second growing season.

Seed production and dissemination:  Young trees start to bear cones at
the age of 20 years.  Cones may remain attached to the tree for 8 to 12
years and much of the seed will be retained.  During the late summer,
however, some seed is shed when the cone scales shrink.  Most seeds are
liberated when the cone drys out and becomes detached.  Each cone yields
an average of 230 seeds.  The average number of cleaned seeds per pound
is approximately 81,000 (200,070/kg).  Stored giant sequoia seed remains
moderately viable for many years [5,10,28].  At any given time, a large
tree may be expected to have approximately 11,000 cones.  The upper part
of the crown of any mature giant sequoia invariably produces a greater
abundance of cones than its lower portions.

A mature giant sequoia has been estimated to disperse from 300,000 to
400,000 seeds per year.  Seed dispersal results from seed falling from
the tree-top, insect and rodent activity, or by cones falling to the
ground.  The winged seeds may be carried up to 600 feet (183 m) from the
parent tree.

Seedling development:  Giant sequoia seeds germinate best when totally
buried in disturbed mineral soil.  April, May, September, and October
temperatures are best for early development.  Soil moisture conditions
and seedling survival are generally better in spring than during any
other season.  Light conditions are generally best for growing at
one-half full sunlight.  Upon germination, the seedling stands 3/4 to 1
inch (1.9-2.5 cm) high, usually with four cotyledons.  By autumn,
seedlings have up to six branches and are 3 to 4 inches (8-10 cm) tall.
After the second year, the seedling attains a height of 8 to 12 inches
(20-30 cm) with a taproot penetrating to a depth of 10 to 15 inches
(25-38 cm) [28].

Growth and yield:  Giant sequoia is the worlds largest tree in terms of
total volume.  Beyond the seedling stage, giant sequoia unhindered by an
overstory continues to grow at the same rate as its competitors.  Yields
of second growth stands dominated by giant sequoia were found to equal
or slightly exceed those of second-growth mixed-conifer stands on the
same site.  Lower branches die fairly readily from shading, but trees
less than 100 years old retain most of their dead branches.  Boles of
mature trees generally are free of branches to a height of 98 to 148
feet (30-40 m) [28].


SITE CHARACTERISTICS : 
Low temperatures seem to be the limiting factor for giant sequoia at the
upper elevational limits of its range, as well as in areas with severe
winters where the species has been introduced.  Distribution of giant
sequoia at lower elevations appears to be restricted to sites with
available soil moisture throughout the summer drought period [24,28].

Climate:  Giant sequoia is found in a humid climate characterized by dry
summers.  Mean annual precipitation varies from 35 to 55 inches (88-138
cm).  Most precipitation comes in the form of snow between October and
April.  Mean annual snowfall ranges from 144 to 197 inches (360-493 cm),
and snow depths of 6.6 feet (2 m) or greater are common.  Mean daily
maximum temperatures for July are typically 75 to 84 degrees Fahrenheit
(24-29 deg C).  Mean minimum temperatures for January vary from 34 to 21
degrees Fahrenheit (1 to -6 deg C) [28].

Soils and topography:  Most giant sequoia groves are on granitic-based
residual and alluvial soils.  Some groves are on glacial outwash from
granite.  Other common parent materials include schistose, dioritic and
andesitic rocks.  Giant sequoia grows best in deep, well-drained sandy
loams.  It occurs with higher frequency on mesic sites, such as drainage
bottoms and meadow edges.  Soil pH ranges from 5.5 to 7.5, with an
average of about 6.5.  Long-term site occupancy develops soil of high
fertility, good base status, and low bulk density.  Except for its
moisture content, soil typically plays only a minor role in influencing
the distribution of the species [28].

Elevation:  Elevation of the giant sequoia groves generally range from
4,590 to 6,560 feet (1,400-2,000 m) in the north, and 5,580 to 7,050
(1,700-2,150 m) to the south.  The lowest natural occurrence of the
species is 2,720 feet (830 m) and the highest is 8,860 feet (2,700 m).
Giant sequoia generally appears on southern slopes in its northern
distribution and on more northerly slopes in the south [28].


SUCCESSIONAL STATUS : 
Giant sequoia has adapted to keep its crown higher than that of its
associates.  On disturbed sites, giant sequoia is a strong competitor,
although never totally dominating a stand [10].  Current data does not
indicate that any enlargement of giant sequoia groves is taking place.
Mature giant sequoia mark the outer boundaries, which have remained
stable over a period of 500 to 1,000+ years.  High levels of
reproduction are not necessary to maintain the present population
levels.  Few groves, however, have sufficient young trees to maintain
the present density of mature giant sequoias for the future.  The
majority of giant sequoias are currently undergoing a gradual decline in
density since the European settlement days [24].



SEASONAL DEVELOPMENT : 
Giant sequoia flowers from April to May; cone ripening and seed
dispersal occurs in the spring and summer months.  Seeds dropped just
before the first snow or just as the snow melts may have the best chance
of germinating and becoming successfully established.  Growth of giant
sequoia generally begins in the early spring to late fall [28].

Related categories for Species: Sequoiadendron giganteum | Giant Sequoia