Yosemite Trees
Of the 27 varieties of trees in the park, these four are
easy to identify, due to their impressive size and distinctive
characteristics:
California black oak is abundant in Yosemite Valley. These
large deciduous trees, with yellow-green leaves and dark trunks,
produce acorns which the Miwok Indians ground into nutritious
flour.
The incense-cedar has a feathery reddish bark which is often
confused with the giant sequoia. Incense-cedars grow abundantly
throughout the Sierra, while sequoias grow only in limited
numbers of groves.
The giant sequoias are the largest trees on earth. Three groves
of them are located in the park: the Mariposa Grove near the
southern entrance (Highway 41); the Tuolumne Grove, near Crane
Flat on the Tioga Road; and the Merced Grove, off the Big
Oak Flat Road between Crane Flat and the Big Oak Flat Entrance.
The giant sequoia often lives from 1,000 to 3,000 years. A
few of these big trees were planted by settlers in Yosemite
Valley, though they are not native to the Valley.
The ponderosa pine can be identified by its bark made up of
irregularly shaped plates separated by dark furrows. Mature
trees are considerably wide at the base with a straight trunk
rising many feet before reaching the branches.
Giant Sequoias
The Big Tree is Nature's forest masterpiece and so far as
I know, the greatest of living things- John Muir
Although not the oldest living things, a distinction held
by the bristlecone pine, giant sequoias are the largest in
total volume. Outstanding trees are 2,500 to 3,000 years old,
measure up to 35 ft (11 m) in diameter, and tower to heights
of 250 to 300 ft (76 m to 91 m) above the ground. Single sequoia
limbs may be larger than record-size trees of other species.
There seem to be no limits on the trees' growth. Sequoias
typically do not die of old age: they usually die by toppling.
Is a sequoia a redwood?
What is the difference between sequoias and redwoods? The
giant sequoia, a member of the redwood family, has a column-like
trunk, huge stout branches, and cinnamon-colored bark. Its
scientific name is Sequoiadendron giganteum. It is sometimes
called the Sierra redwood. The taller more slender coast redwood,
Sequoia sempervirens, has the kind of profile and branch structure
associated with most conifers. It is named for the color of
its heartwood, not its brownish bark. A third species, the
dawn redwood, is native to China.
Distribution
Giant sequoias occur only in about 75 groves scattered between
4,500 and 7,000 ft (1,372 and 2,133 m) in elevation on the
west slope of the Sierra Nevada. Some groves containa few
trees, others several thousand. The sequoias are not isolated
from other trees, but grow in association with white fir,
sugar pine, ponderosa pine, and incense-cedar. What makes
them stand out from the others is their tremendous size.
Fire: rebirth and renewal
Near the bases of these giants, the bark may be 12 to 18 inches
(30 to 45 cm) thick; however the bark on the limbs is very
thin. This soft, fibrous bark is fire resistant and protects
the growth layer from periodic fires ignited by lightening.
Intense heat generated by the debris accumulated at the tree's
base, along with the effect of repeated fires, can breach
the bark. However, the tree's water-based sap also enhances
the tree's heat tolerance. Burn scars and the blackened, hollow
trunks of some older, yet healthy, trees attest to the many
fires that have burned through the groves over the centuries.
Fire prepares the seed bed by burning off the duff (decomposing
bark, needles, and other vegetation) that accumulates on the
forest floor. Burning off the duff exposes bare mineral soil,
which giant sequoia seedlings need in order to germinate.
The park routinely conducts prescribed burns in the sequoia
groves in order to mimic the natural cycle of fire. Fires
not only bare the soil but also brun off competing smaller
species, such as the shade tolerant white fir and incense-cedar.
From seeds to saplings
Giant sequoias sprout only from seeds--seeds so small and
light they resemble flakes of oatmeal. A 1 ounce (30 grams)
package would contain about 57,000 seeds. The delicate seeds
are procuded in cones that take two years to develop. Although
the size of a chicken's egg, each cone contains 200 to 300
seeds.
Giant sequoias often retain the green cones alive on the tree
for up to 20 or more years. Outside forces, such as fire,
insect larvae, and Douglas squirrels, are required to help
the tree disperse its seeds.
Contact with the ground does not assure the seeds will germinate.
Seeds contain little energy, producing a tap root that is
not more than one inch (2.5 cm) long. If this tiny root fails
to reach mineral soil, it will be unable to transport the
nutrients and water necessary to keep the sequoia sprout alive.
The maturing sequoia
Sequoia saplings grow to their maximum height within several
hundred years. At this time, they are conical, like an upside-down
ice cream cone. The limbs often grow along the entire length
of the trunk. After reaching their maximum height, the trunks
begin to grow outward more quickly. The bark thickens, the
lower limbs fall off, and the trunk expands to form the shape
of a huge column. In addition, the crown of the tree rounds
and the large limbs become craggy in appearance as this forest
monarch comes of age.
Sequoia groves
The largest groves and biggest individual sequoias are found
in Sequoia and Kings Canyon National Parks, in the southern
Sierra Nevada. Many mature sequoias also live exist in Yosemite
National Park in three groves: the Mariposa Grove, Tuolumne
Grove, and Merced Grove. The Mariposa Grove, the largest of
the three groves, is well known for the Grizzly Giant (once
thought to be the oldest living sequoia) and the fallen Wawona
Tunnel Tree. The Wawona Tunnel Tree became world-famous when
an opening was cut through the tree in 1881. For the next
88 years, people came, first in stages and then in automobiles,
to ride through this tree. As a result of wet snow, soggy
soil, high winds, and perhaps combined with the weakening
of the tree from the tunnel, the tree toppled in the winter
of 1968/1969. You can still visit this fallen tree, as well
as still walk through the California Tunnel Tree (carved out
in 1895), near the Grizzly Giant.
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