Sequoia

Biology and ecology of sequoias

Economic importance

Resources

Sequoias are species of coniferous trees in the genus Sequoia, family Taxodiaceae. Sequoias can reach enormous height and girth and can attain an age exceeding 1,000 years. These giant, venerable trees are commonly regarded as botanical wonders.

About 40 species of sequoias are known from the fossil record, which extends to the Cretaceous, about 60 million years ago. At that time, extensive forests dominated by sequoias and related conifers flourished in a warm and wet climatic regime throughout the Northern Hemisphere. Ancient fossil stands of sequoias and other conifers have even been found in the high Arctic of Ellesmere Island and Spitzbergen. This indicates a relatively mild climatic regime in the Arctic in the distant past, compared with the intensely cold and dry conditions that occur there today. Similarly, the famous Petrified Forest located in a desert region of Arizona is dominated by fossilized sequoia trees and their relatives that lived in that area many millions of years ago. Clearly, compared with their present highly restricted distribution, redwoods were abundant and widespread in ancient times.

Only two species of sequoias still survive. Both of these species occur in relatively restricted ranges in northern and central California and southern Oregon. The specific reasons why these species have survived only in these places and not elsewhere are not known. Presumably, the local site conditions and disturbance regime have continued to favor redwoods in these areas and allowed these trees to survive the ecological onslaught of more recently evolved species of conifers and angiosperm trees.

The ancient biomass of ancient species of the redwood family are responsible for some of the deposits of fossil fuels that humans are so quickly using today as a source of energy and for the manufacturing of plastics.

Biology and ecology of sequoias

The two living species of sequoias are the redwood or coast redwood (Sequoia sempervirens ) and the giant sequoia, big tree, or Sierra redwood (S. gigantea, sometimes placed in another genus, Sequoiadendron ). Both of these species can be giants, reaching an enormous height and girth. However, the tallest individuals are redwoods, while the widest ones are giant sequoias.

The redwood occurs in foggy rainforest of the Coast Range from sea level to about 3,300 ft (1,000 m) in elevation. The range of the redwood extends from just south of San Francisco, through northern California, to southern Oregon. This tree has evergreen, flattened, needle like foliage that superficially resembles that of yews (Taxus spp., family Taxodiaceae ) and has two whitish stripes underneath. The seed-bearing female cones are as long as 1 in (2.5 cm) and have 15-20 scales. The seeds tend not to germinate prolifically. If cut down, redwoods will regenerate well by vegetative sprouts from the stump and roots, an unusual characteristic among the conifers. Redwoods have a thick, reddish, fibrous bark as much as 10 in (25 cm) deep. Redwood trees commonly achieve a height of 200-280 ft (60-85 m). Exceptional trees are as tall as 360 ft (110 m), can have a basal diameter of 22 ft (6.7 m), and can be older than 1,400 years. No other living trees have achieved such lofty heights.

The giant redwood has a somewhat more inland distribution in northern California. This species occurs in groves on the western side of the Sierra Nevada Mountains, at elevations of 4,000-8,000 ft (1,200-2,400 m) with fairly abundant precipitation and soil moisture. The giant redwood has scale like, awl-shaped foliage, very different in form from that of the redwood. The female cones are rounder and larger than those of the redwood, up to 3.5 in (9 cm) long and containing 24-40 wedge-shaped scales. The bark is fibrous and thick and can be as much as 24 in (60 cm) thick at the base of large trees. One of the largest known individuals is known as the General Sherman Tree, which is 274 ft (83 m) tall, has a basal diameter of 31 ft (9.4 m), and is estimated to be a venerable 3,800 years old. In terms of known longevity of any organism, the giant redwood is marginally second only to individuals of the bristlecone pine (Pinus aristata ) of subalpine habitat of the southwestern United States.

Other living relatives of sequoias are the bald cypress (Taxodium distichum ) of the southeastern United States and the Montezuma bald cypress (T. mucronatum ) of parts of Mexico. Asian relatives, sometimes cultivated as unusual ornamentals in North America, include the metasequoia or dawn redwood (Metasequoia glyptos-troboides ) and the Japanese cedar or sugi (Cryptomeria japonica ). The dawn redwood of central China was described in the fossil record prior to being observed as living plants by astonished western botanists in the 1940s. For this reason, the dawn redwood is sometimes referred to as a “living fossil.”

Wildfire is important in the ecology of redwood forests, but especially in groves of giant redwood. Young seedlings and trees of giant redwood are vulnerable to fire, but older, larger trees are resistant to ground-level fires because of their thick bark. In addition, older redwoods tend to have lengthy expanses of clear trunk between the ground and their first live branches so that devastating crown fires are not easily ignited. Some of the competitor trees of the giant redwood are not so tolerant of fire, so this disturbance helps to maintain the redwood groves.

The development of lower- and mid-height canopies of other species of conifer trees in an old-growth stand of giant redwoods could potentially provide a “ladder” of flammable biomass that could allow a devastating crown fire to develop, which might kill the large redwood trees. Because giant redwoods do not sprout from their stump after their above-ground biomass is killed, they could end up being replaced by other species after a grove is badly damaged by a crown fire. This could result in the loss of a precious natural stand of giant redwoods, representing a tragic loss of the special biodiversity values of this type of rare natural ecosystem.

To prevent the development of a vigorous under-story of other species of trees in old-growth groves of giant redwoods, these stands are sometimes managed using prescribed burns. Fire allows open stands of redwoods to occur, while preventing the development of a potentially threatening, vigorous population of other species of trees, such as white fir (Abies concolor ) and Douglas-fir (Pseudotsuga menziesii ). Fire may also be important in the preparation of a seedbed suitable for the occasional establishment of seedlings of giant redwood.

Economic importance

The coast redwood has an extremely durable wood, and it is highly resistant to decay caused by fungi. The heartwood is an attractive reddish color, while the outer sapwood is paler. The grain of redwood lumber is long and straight, and the wood is strong, although rather soft. Redwood trees are harvested and used to make durable posts, poles, and pilings, and are manufactured into value-added products such as structural lumber, outdoor siding, indoor finishing, furniture and cabinets, and sometimes into shakes, a type of roofing shingle made by splitting rather than sawing blocks of wood.

Because of its great usefulness and value, the coast redwood has been harvested rather intensively. If the logged site and regeneration are appropriately managed after the harvesting of redwoods, it will regenerate rather well to this species. Consequently, there is little risk of the commercial extinction of this valuable natural resource. However, few natural stands of the coast redwood have survived the onslaught of commercial exploitation, so its distinctive old-growth ecosystem is at great risk of ecological extinction. Natural, self-organizing, old-growth redwood forests can only be preserved, and this must be done in rather large ecological reserves, such as parks, if this ecosystem is to be sustained over the longer term.

Compared with the coast redwood, the giant redwood is of much less commercial importance and is relatively little used. Most of the best surviving old-growth groves of this species are protected from

KEY TERMS

Commercial extinction —A situation in which it is no longer economically profitable to continue to exploit a depleted natural resource. The resource could be a particular species or an entire ecosystem, such as a type of old-growth forest.

Ecological (or biological) extinction —A representative of a distinct ecosystem or living individuals of a particular species (or another biological taxon) that no longer occurs anywhere on Earth.

Prescribed burn —The controlled burning of vegetation as a management practice to achieve some ecological benefit.

Sprout —Non-sexual, vegetative propagation or regeneration of a tree. Sprouts may issue from a stump, roots, or a stem.

exploitation in National Parks and other types of ecological reserves. However, there is increasing interest in developing commercial stands of the giant redwood elsewhere within its natural range, while continuing to protect the surviving old-growth stands.

Both species of sequoias are sometimes grown as ornamental trees in warm, moist, temperate climates outside of their natural range. Sequoias have been especially popular in horticulture in parts of England.

Resources

BOOKS

Nystrom, Andrew Dean, Peter Johnstone, and Peter E. Palmquist, eds. Giants in the Earth: The California Redwoods. Berkeley, CA: Heyday Books, October 2001.

Watts, Tom. Pacific Coast Tree Finder. 2nd ed., Rochester, NY: Nature Study Guild Publishers, December 2004.

Bill Freedman

Sequoia

Sequoias are species of coniferous trees in the genus Sequoia, family Taxodiaceae. Sequoias can reach enormous height and girth and can attain an age exceeding 1,000 years. These giant, venerable trees are commonly regarded as botanical wonders.

About 40 species of sequoias are known from the fossil record, which extends to the Cretaceous, about 60 million years ago. At that time, extensive forests dominated by sequoias and related conifers flourished in a warm and wet climatic regime throughout the Northern Hemisphere. Ancient fossil stands of sequoias and other conifers have even been found in the high Arctic of Ellesmere Island and Spitzbergen. This indicates a relatively mild climatic regime in the Arctic in the distant past, compared with the intensely cold and dry conditions that occur there today. Similarly, the famous Petrified Forest located in a desert region of Arizona is dominated by fossilized sequoia trees and their relatives that lived in that area many millions of years ago. Clearly, compared with their present highly restricted distribution, redwoods were abundant and widespread in ancient times.

Only two species of sequoias still survive. Both of these species occur in relatively restricted ranges in northern and central California and southern Oregon. The specific reasons why these species have survived only in these places and not elsewhere are not known. Presumably, the local site conditions and disturbance regime have continued to favor redwoods in these areas and allowed these trees to survive the ecological onslaught of more recently evolved species of conifers and angiosperm trees.

The ancient biomass of ancient species of the redwood family are responsible for some of the deposits of fossil fuels that humans are so quickly using today as a source of energy and for the manufacturing of plastics .

Biology and ecology of sequoias

The two living species of sequoias are the redwood or coast redwood (Sequoia sempervirens) and the giant sequoia, big tree , or Sierra redwood (S. gigantea, sometimes placed in another genus, Sequoiadendron). Both of these species can be giants, reaching an enormous height and girth. However, the tallest individuals are redwoods, while the widest ones are giant sequoias.

The redwood occurs in foggy rainforest of the Coast Range from sea level to about 3,300 ft (1,000 m) in elevation. The range of the redwood extends from just south of San Francisco, through northern California, to southern Oregon. This tree has evergreen, flattened, needle-like foliage that superficially resembles that of yews (Taxus spp., family Taxodiaceae) and has two whitish stripes underneath. The seed-bearing female cones are as long as 1 in (2.5 cm) and have 15-20 scales. The seeds tend not to germinate prolifically. If cut down, redwoods will regenerate well by vegetative sprouts from the stump and roots, an unusual characteristic among the conifers. Redwoods have a thick, reddish, fibrous bark as much as 10 in (25 cm) deep. Redwood trees commonly achieve a height of 200-280 ft (60-85 m). Exceptional trees are as tall as 360 ft (110 m), can have a basal diameter of 22 ft (6.7 m), and can be older than 1,400 years. No other living trees have achieved such lofty heights.

The giant redwood has a somewhat more inland distribution in northern California. This species occurs in groves on the western side of the Sierra Nevada Mountains, at elevations of 4,000-8,000 ft (1,200-2,400 m) with fairly abundant precipitation and soil moisture. The giant redwood has scale-like, awl-shaped foliage, very different in form from that of the redwood. The female cones are rounder and larger than those of the redwood, up to 3.5 in (9 cm) long and containing 24-40 wedge-shaped scales. The bark is fibrous and thick and can be as much as 24 in (60 cm) thick at the base of large trees. One of the largest known individuals is known as the General Sherman Tree, which is 274 ft (83 m) tall, has a basal diameter of 31 ft (9.4 m), and is estimated to be a venerable 3,800 years old. In terms of known longevity of any organism , the giant redwood is marginally second only to individuals of the bristlecone pine (Pinus aristata) of subalpine habitat of the southwestern United States.

Other living relatives of sequoias are the bald cypress (Taxodium distichum) of the southeastern United States and the Montezuma bald cypress (T. mucronatum) of parts of Mexico. Asian relatives, sometimes cultivated as unusual ornamentals in North America , include the metasequoia or dawn redwood (Metasequoia glyptostroboides) and the Japanese cedar or sugi (Cryptomeria japonica). The dawn redwood of central China was described in the fossil record prior to being observed as living plants by astonished western botanists in the 1940s. For this reason, the dawn redwood is sometimes referred to as a "living fossil."

Wildfire is important in the ecology of redwood forests, but especially in groves of giant redwood. Young seedlings and trees of giant redwood are vulnerable to fire, but older, larger trees are resistant to ground-level fires because of their thick bark. In addition, older redwoods tend to have lengthy expanses of clear trunk between the ground and their first live branches so that devastating crown fires are not easily ignited. Some of the competitor trees of the giant redwood are not so tolerant of fire, so this disturbance helps to maintain the redwood groves.

The development of lower- and mid-height canopies of other species of conifer trees in an old-growth stand of giant redwoods could potentially provide a "ladder" of flammable biomass that could allow a devastating crown fire to develop, which might kill the large redwood trees. Because giant redwoods do not sprout from their stump after their above-ground biomass is killed, they could end up being replaced by other species after a grove is badly damaged by a crown fire. This could result in the loss of a precious natural stand of giant redwoods, representing a tragic loss of the special biodiversity values of this type of rare natural ecosystem .

To prevent the development of a vigorous understory of other species of trees in old-growth groves of giant redwoods, these stands are sometimes managed using prescribed burns. Fire allows open stands of redwoods to occur, while preventing the development of a potentially threatening, vigorous population of other species of trees, such as white fir (Abies concolor) and Douglas-fir (Pseudotsuga menziesii). Fire may also be important in the preparation of a seedbed suitable for the occasional establishment of seedlings of giant redwood.

Economic importance

The coast redwood has an extremely durable wood , and it is highly resistant to decay caused by fungi . The heartwood is an attractive reddish color , while the outer sapwood is paler. The grain of redwood lumber is long and straight, and the wood is strong, although rather soft. Redwood trees are harvested and used to make durable posts, poles, and pilings, and are manufactured into value-added products such as structural lumber, outdoor siding, indoor finishing, furniture and cabinets, and sometimes into shakes, a type of roofing shingle made by splitting rather than sawing blocks of wood.

Because of its great usefulness and value, the coast redwood has been harvested rather intensively. If the logged site and regeneration are appropriately managed after the harvesting of redwoods, it will regenerate rather well to this species. Consequently, there is little risk of the commercial extinction of this valuable natural resource. However, few natural stands of the coast redwood have survived the onslaught of commercial exploitation, so its distinctive old-growth ecosystem is at great risk of ecological extinction. Natural, self-organizing, old-growth redwood forests can only be preserved, and this must be done in rather large ecological reserves, such as parks, if this ecosystem is to be sustained over the longer term.

Compared with the coast redwood, the giant redwood is of much less commercial importance and is relatively little used. Most of the best surviving old-growth groves of this species are protected from exploitation in National Parks and other types of ecological reserves. However, there is increasing interest in developing commercial stands of the giant redwood elsewhere within its natural range, while continuing to protect the surviving old-growth stands.

Both species of sequoias are sometimes grown as ornamental trees in warm, moist, temperate climates outside of their natural range. Sequoias have been especially popular in horticulture in parts of England.

Resources

books

Weatherspoon, C.P., Y.R. Iwamoto, and D.D. Douglas. eds. Management of Giant Sequoia. Berkeley, CA: Pacific Southwest Forest and Range Experiment Station, 1985.

Bill Freedman

KEY TERMS

Commercial extinction

—A situation in which it is no longer economically profitable to continue to exploit a depleted natural resource. The resource could be a particular species or an entire ecosystem, such as a type of old-growth forest.

Ecological (or biological) extinction

—A representative of a distinct ecosystem or living individuals of a particular species (or another biological taxon) that no longer occurs anywhere on Earth.

Prescribed burn

—The controlled burning of vegetation as a management practice to achieve some ecological benefit.

Sprout

—Non-sexual, vegetative propagation or regeneration of a tree. Sprouts may issue from a stump, roots, or a stem.

SEQUOIA

SEQUOIA, a genus of coniferous trees, comprising the species Sequoia sempervirens (the redwood) and Sequoia-dendron giganteum (the giant sequoia), thought to be named for Sequoyah, the Cherokee Indian blacksmith and silversmith who invented the Cherokee alphabet about 1809. Both species average 275 feet in height, with trunks from 15 to 35 feet in diameter. Sequoias are the largest of all American forest trees, with the tallest redwoods attaining heights of more than 350 feet and the giant sequoia generally containing the largest total volume of wood. The redwood is found in the Pacific Coast region, from California to Oregon; the giant sequoia grows wild only on the western slope of the Sierra Nevada in California, generally between five thousand and seven thousand feet in elevation, where it finds a mix of mild temperatures and adequate rainfall. Sequoia wood is soft, light, and of a reddish color that darkens on exposure. Once believed to be the world's oldest living things—some are more than three thousand years old—sequoias have very thick bark that makes them highly resistant to insects, fire, and fungi. They have a very shallow root system, however, and rely on a straight trunk and well-balanced limbs to stay upright; most fall to their death.

Sequoias probably first became known to the white man in 1833, when Captain Joseph Walker's expedition sighted them. A. T. Dowd is credited with discovering the Calaveras grove in 1852. In less than a decade, loggers began extensive cutting of the sequoia, and cutting continued into the twentieth century, although on a lesser scale. The Sequoia National Park in the Sierra Nevada was established on 25 September 1890 to protect the groves of giant sequoia. The General Sherman tree in the park is 272 feet high and one of the oldest living things in the world; another famous tree had a hole bored through its trunk, allowing automobiles to drive through.

BIBLIOGRAPHY

Dilsaver, Lary M. Challenge of the Big Trees. Three Rivers, Calif.: Sequoia Natural History Association, 1990.

Orsi, Richard J., Alfred Runte, and Marlene Smith-Baranzini, eds. Yosemite and Sequoia: A Century of California National Parks. Berkeley: University of California Press, 1993.

JohnFrancisJr./c. w.

See alsoLumber Industry ; National Park System .

Sequoia

Sequoia is a genus of conifer containing one species, Sequoia sempervirens, the coast redwood. It is named for a Georgian Indian chieftain who invented the Cherokee alphabet. Traditionally included in the Taxodiaceae, current workers combine this family with the cypress family, Cupressaceae. One of the world's tallest tree species, sequoias can exceed 115 meters (360 feet) in height. The trunk, covered in red, shredding bark, is about 3 to 5 meters (10 to 16 feet) in diameter, but may reach 10 meters (33 feet). The branches bear both triangular and needlelike leaves. Male (pollen-producing) and female (seed-bearing) cones are borne on the same tree, but on different branches. Sequoiadendron giganteum, the giant redwood, formerly included in Sequoia, was placed in its own genus in 1939.

Coast redwoods form coniferous forests in western North America, from coastal central California to southernmost Oregon. Here they receive fog that provides moisture and cool conditions during the dry summer months. Coast redwoods are relics, plants that had wider distribution in the milder, moister climate of the past. Adult trees can live 2,200 years, and their thick bark resists most fires, which clear the undergrowth and create the open conditions needed for seedling establishment.

Redwood lumber is greatly desired, as it is rot resistant and straight grained. Therefore, redwood trees have been logged heavily during the last 150 years. Trees readily resprout from roots and stumps, so forests grow back quickly. Nevertheless, concern for the disappearance of virgin groves prompted the creation of Muir Woods National Monument in 1908. Less than five percent of the ancient redwood forests are intact, and most of those survive only through the protection of parks and National Forests.

see also Coniferous Forests; Conifers; Gymnosperms; Record-holding Plants; Trees.

Dean G. Kelch

Bibliography

Lanner, Ronald M. Conifers of California. Los Olivos, CA: Cachuma Press, 1999.

Sequoia (family Taxodiaceae) A monotypic genus of evergreen conifers, S. sempervirens (coast redwood) of the N. American coastal fog belt from Oregon to California. Sequoia is a giant, columnar tree, probably the tallest in the world. The bark is soft and spongy, and it yields valuable timber. The leaves are spreading and yew-like.