Sequoia sempervirens
S. sempervirens along US 199
Conservation status
Vulnerable (IUCN 3.1)
Scientific classification
Kingdom:	Plantae
Division:	Pinophyta
Class:	Pinopsida
Order:	Pinales
Family:	Cupressaceae
Subfamily:	Sequoioideae
Genus:	Sequoia
Species:	S. sempervirens
Binomial name
Sequoia sempervirens (D. Don) Endl.

Sequoia sempervirens (pronounced /sɨˈkɔɪ.ə sɛmpərˈvaɪrənz/^[1]) is the sole living species of the genus Sequoia in the cypress family Cupressaceae (formerly treated in Taxodiaceae). Common names include coast redwood, California redwood, and giant redwood. It is an evergreen, long-lived, monoecious tree living 1200–1800 years or more.^[2] This species includes the tallest trees on Earth, reaching up to 379 feet (115.5 m) in height (without the roots) and up to 26 feet (7.9 m) diameter at breast height. Before commercial logging and clearing began by the 1850s, this massive tree occurred naturally in an estimated 2,100,000 acres (8,500 km²) along much of coastal California (excluding southern California where rainfall is not sufficient) and the southwestern corner of coastal Oregon within the United States. It is estimated that more than 95% of the original old-growth redwood forest has been cut down,^[3] due to its excellent properties for use as lumber in construction.

The name sequoia sometimes refers to the subfamily Sequoioideae, which includes S. sempervirens along with Sequoiadendron (giant sequoia) and Metasequoia (dawn redwood). On its own, the term redwood usually refers to the coast redwood, which is covered in this article, and not to the other two species.

Description[link]

Bark detail

Coast redwoods have a conical crown, with horizontal to slightly drooping branches. The bark is very thick, up to 30 cm (12 in), and quite soft, fibrous with a bright red-brown when freshly exposed (hence the name redwood), weathering darker. The root system is composed of shallow, wide-spreading lateral roots.

The leaves are variable, being 15–25 millimetres (0.59–0.98 in) long and flat on young trees and shaded shoots in the lower crown of old trees, and scale-like, 5–10 millimetres (0.20–0.39 in) long on shoots in full sun in the upper crown of older trees; there is a full range of transition between the two extremes. They are dark green above, and with two blue-white stomatal bands below. Leaf arrangement is spiral, but the larger shade leaves are twisted at the base to lie in a flat plane for maximum light capture.

The species is monoecious, with pollen and seed cones on the same plant. The seed cones are ovoid, 15–32 millimetres (0.59–1.3 in) long, with 15–25 spirally arranged scales; pollination is in late winter with maturation about 8–9 months after. Each cone scale bears 3–7 seeds, each seed 3–4 millimetres (0.12–0.16 in) long and 0.5 millimetres (0.020 in) broad, with two wings 1 millimetre (0.039 in) wide. The seeds are released when the cone scales dry out and open at maturity. The pollen cones are oval, 4–6 millimetres (0.16–0.24 in) long.

Its genetic makeup is unusual among conifers, being a hexaploid (6n) and possibly allopolyploid (AAAABB).^[4] The mitochondrial genome of the redwood is paternally inherited (unlike that of other conifers).^[5]

Range and ecology[link]

Sunlight shining through redwoods in Muir Woods

Fog is of major importance in coast redwood ecology. Redwood National Park.

Coast redwoods occupy a narrow strip of land approximately 750 km (470 miles) in length and 8–75 km (5–47 miles) in width along the Pacific coast of North America; from the most southerly grove in Monterey County, California to groves that exist in extreme southwestern Oregon. The elevation range is mostly from 30–750 metres (98–2,460 ft), occasionally down to sea level and up to 920 m (about 3,000 feet) (Farjon 2005). They usually grow in the mountains where there is more precipitation from the incoming moisture off the ocean. The tallest and oldest trees are found in deep valleys and gullies, where year-round streams can flow, and fog drip is regular. The trees above the fog layer, above about 700 metres (2,300 ft), are shorter and smaller due to the drier, windier, and colder conditions. In addition, tanoak, pine and Douglas-fir often crowd out redwoods at these elevations. Few redwoods grow close to the ocean, due to intense salt spray, sand and wind. Condensation from coastal fog accounts for a considerable part of the trees' water needs.^[6]

The northern boundary of its range is marked by two groves on the Chetco River on the western fringe of the Klamath Mountains, 25 km (15 miles) north of the California-Oregon border. The largest (and tallest) populations are in Redwood National and State Parks (Del Norte and Humboldt Counties) and Humboldt Redwoods State Park (Humboldt County, California), with the majority located in the much larger Humboldt County. The southern boundary of its range is the Los Padres National Forest's Silver Peak Wilderness in the Santa Lucia Mountains of the Big Sur area of Monterey County, California. The southernmost grove is in the Southern Redwood Botanical Area, just north of the national forest's Salmon Creek trailhead.^[7]

This native area provides a unique environment with heavy seasonal rains (2,500 millimetres (98 in) annually). Cool coastal air and fog drip keep this forest consistently damp year round. Several factors, including the heavy rainfall, create a soil with fewer nutrients than the trees need, causing the trees to depend heavily on the entire biotic community of the forest, and complete recycling of the trees when dead. This forest community includes Coast Douglas-fir, Western Hemlock, Tanoak, Pacific Madrone, and other trees along with a wide variety of ferns, Redwood sorrel, mosses and mushrooms. Redwood forests provide habitat for a variety of mammals, birds, reptiles, and amphibians. Old growth redwood stands provide habitat for the federally threatened Spotted Owl and the California-endangered Marbled Murrelet.

The thick, tannin-rich bark, combined with foliage that starts high above the ground provides good protection from both fire and insect damage, contributing to the coast redwood's longevity. The oldest known coast redwood is about 2,200 years old;^[8] many others in the wild exceed 600 years. The numerous claims of older trees are incorrect.^[8] Because of their seemingly timeless lifespan, coast redwoods were deemed the "everlasting redwood" at the turn of the century; in Latin, "sempervirens" means "ever green" or "everlasting". Redwood must successfully endure fire in order to attain such great ages and thus it is perhaps not surprising that this species has many fire-resistant characteristics. In addition, fires appear to actually benefit redwood by causing substantial mortality in competing species while having only minor effects on redwood. One recent study, the first to compare post-wildfire survival and regeneration of redwood and associated species, concluded that fires of all severity increase the relative abundance of redwood and that higher severity fires provide the greatest benefit. ^[9]

The prehistoric fossil range of the genus is considerably greater, with a subcosmopolitan distribution including Europe and Asia until about 5 million years ago.

Reproduction[link]

A ring of sequoia trees as seen from below

Coast redwood reproduces both sexually by seed and asexually by sprouting of buds, layering, or lignotubers. Seed production begins at 10–15 years of age, and large seed crops occur frequently, but viability of the seed is low, typically well below 15%.^[10] The low viability may discourage seed predators, which do not want to waste time sorting chaff (empty seeds) from edible seeds. The winged seeds are small and light, weighing 3.3–5 mg (200-300 seeds/g; 5,600-8,500/ounce). The wings are not effective for wide dispersal, and seeds are dispersed by wind an average of only 60–120 m (200–400 feet) from the parent tree. Growth of seedlings is very fast, with young trees known to reach 20 m (65 ft) tall in 20 years.

Coast redwoods can also reproduce asexually by layering or sprouting from the root crown, stump, or even fallen branches; if a tree falls over, it will regenerate a row of new trees along the trunk. This is the reason for many trees naturally growing in a straight line. Sprouts originate from dormant or adventitious buds at or under the surface of the bark. The dormant sprouts are stimulated when the main adult stem gets damaged or starts to die. Many sprouts spontaneously erupt and develop around the circumference of the tree trunk. Within a short period after sprouting, each sprout will develop its own root system, with the dominant sprouts forming a ring of trees around the parent root crown or stump. This ring of trees is called a "fairy ring". Sprouts can achieve heights of 2.3 m (8 ft) in a single growing season.

Redwoods may also reproduce using burls. A burl is a woody lignotuber that commonly appears on a redwood tree below the soil line, though usually within 3 metres (9.8 ft) in depth from the soil surface. Burls are capable of sprouting into new trees when detached from the parent tree though exactly how this happens is yet to be studied. Shoot clones commonly sprout from burls and are often turned into decorative hedges when found in suburbia.

The species is very tolerant of flooding and flood deposits, the roots rapidly growing into thick silt deposits after floods.

Cultivation and uses[link]

The Skyline-to-the-Sea Trail passing through a fallen California Redwood tree

Coast redwood is one of the most valuable timber species in the lumbering industry. In California 899,000 acres (3,640 km²) of redwood forest are in production, virtually all of it second growth.^[11] Though many entities have existed in the production and management of redwoods, perhaps none have had a more storied role than the Pacific Lumber Company (1863-2008) of Humboldt County, California, where it owned and managed over 200,000 acres (810 km²) of forests, primarily redwood. Coast redwood lumber is highly valued for its beauty, light weight, and resistance to decay. Its lack of resin makes it resistant to fire.

P. H. Shaughnessy, Chief Engineer of the San Francisco Fire Department wrote:

In the recent great fire of San Francisco, that began April 18th, 1906, we succeeded in finally stopping it in nearly all directions where the unburned buildings were almost entirely of frame construction and if the exterior finish of these buildings had not been of redwood lumber, I am satisfied that the area of the burned district would have been greatly extended.

Because of its impressive resistance to decay, redwood was extensively used for railroad ties and trestles throughout California. Many of the old ties have been recycled for use in gardens as borders, steps, house beams, etc. Redwood burls are used in the production of table tops, veneers, and turned goods.

The coast redwood is locally naturalized in New Zealand, notably at Whakarewarewa Forest, Rotorua^[12]. Redwood has been grown in New Zealand plantations for over 100 years, and Redwoods planted in New Zealand have higher growth rates than those in California. This is due mainly to even rainfall distribution through the year.^[13] Other areas of successful cultivation outside of the native range include Great Britain, Italy, Portugal,^[14] the Queen Charlotte Islands, middle elevations of Hawaii, Hogsback in South Africa, a small area in central Mexico (Jilotepec) and the southeastern United States from eastern Texas to Maryland. Coast redwood trees were used in a display at Rockefeller Center and then given to Longhouse Reserve in East Hampton, Long Island, New York and these have now been living there for over 17 years (2010) and survived 2 °F (-17 °C).^[15]

Statistics[link]

Dried resin of a redwood tree

An example of a bonsai redwood, from the Brooklyn Botanic Garden

The foliage of an "albino" Sequoia sempervirens exhibiting lack of chlorophyll

Trunk in sectional view

Trees over 200 feet (61 m) are common, and many are over 300 feet (91 m). The current tallest tree is Hyperion, measuring at 379.3 feet (115.6 m).^[8] The tree was discovered in Redwood National Park during Summer 2006 by Chris Atkins and Michael Taylor and has been measured as the world's tallest living organism. The previous record holder was the Stratosphere Giant in the Humboldt Redwoods State Park, at 370.18 feet (112.83 m), last measured in 2004 (was 368.57 feet (112.34 m) in Aug 2000 and 369.29 feet (112.56 m) in 2002). Until it fell in March 1991, the "Dyerville Giant" was the record holder. It too stood in Humboldt Redwoods State Park; it was 372.05 feet (113.40 m) metres high and estimated to be 1,600 years old.

There are 41 measured living trees more than 360 feet (110 m) tall.^[16] There are 178 measured trees that are more than 350 feet (107 m) tall.^[16] Preliminary analysis of LiDAR data indicates there are hundreds of additional trees in excess of 347.8 feet (106.0 m) previously unknown.^[17]

A tree claimed to be 380.12 feet (115.86 m) was cut down in 1914.^[18] A tree claimed to be 424.08 feet (129.26 m) was felled in November 1886 by the Elk River Mill and Lumber Co. at the south fork of Elk river in Humboldt County, yielding 79,736 marketable board feet from 21 cuts.^[19][20][21]

Although coast redwoods are currently the world's tallest trees, it is possible that Australian mountain ash and Douglas-fir trees were taller—exceeding 400 feet (120 m)—before the commercial logging of the 19th and 20th centuries. However, there is fairly solid evidence that before logging coast redwoods were the world's largest trees, with specimens measured at over 55,000 cubic feet (1,600 m³).^[22]

The theoretical maximum potential height of coast redwoods is limited to between 122 to 130 metres (400 to 427 ft), due to gravity and the friction between water and the vessels through which it flows.^[23]

The largest coast redwood is the "Lost Monarch", with an estimated volume of 42,500 cubic feet (1,203 m³); it is 320 feet (98 m) tall with a diameter of 26 feet (7.9 m) at breast high (DBH). It is located in the Grove of Titans. Among current living trees there are only 6 known giant sequoias that are larger; these are shorter, but have thicker trunks overall, giving the largest giant sequoia, General Sherman, a volume of 1,487 cubic metres (52,513 cu ft), making it the world's largest known tree. A redwood cut down in 1926 had a claimed volume of 1,794 cubic metres (63,355 cu ft), but this was not verified.

About fifty albino redwoods (mutant individuals that cannot manufacture chlorophyll) are known to exist, reaching heights of up to 20 metres (66 ft).^[24] These trees survive as parasites, obtaining food by grafting their root systems with those of normal trees. While similar mutations occur sporadically in other conifers, no cases are known of such individuals surviving to maturity in any other conifer species.

Largest trees[link]

The ten largest known coast redwoods by total wood volume in the main trunk and stems combined, as of 2009.^[25]

The order of largest and tallest can change at any time due to new discoveries, loss of stem and foliage, growth, and new measurements. One of the better known Internet databases for large conifers is The Gymnosperm Database,^[8] but its data can be different from other resources due to differences in standards.

Tallest trees[link]

Trees over 112 metres (367 ft), as of 2010.^[16]

There is fairly solid evidence that before logging, coast redwoods were the world's largest trees, with specimens measured at over 55,000 cubic feet (1,600 m³) (660,000 board feet).^[22]

See also[link]

• Bank Hall Gardens
• Bury Me in Redwood Country
• Cryptomeria
• Leighton Hall, Powys
• List of largest giant sequoias
• Northern California coastal forests (WWF ecoregion)
• Pacific temperate rain forest (WWF ecoregion)
• Redwood (color)
• Save-the-Redwoods League

References[link]

Further reading[link]

• Preston, Richard. The Wild Trees: A Story of Passion and Daring, Random House, 2007, ISBN 978-1-4000-6489-2.
• Farjon & members of the Conifer Specialist Group (2006). Sequoia sempervirens. 2006. IUCN Red List of Threatened Species. IUCN 2006. www.iucnredlist.org. Retrieved on 11 May 2006. Database entry includes a lengthy justification of why this species is vulnerable.
• Farjon, A. (2005). Monograph of Cupressaceae and Sciadopitys. Royal Botanic Gardens, Kew. ISBN 1-84246-068-4.
• Noss, R. F., ed. (2000). The Redwood Forest: history, ecology and conservation of the Coast Redwood. Island Press, Washington, D.C. ISBN 1-55963-726-9.

External links[link]

Wikimedia Commons has media related to: Sequoia sempervirens

• Humboldt State University/ Professor Sillett Includes photo gallery, canopy views, epiphytes, and arboreal animals
• Complete Tallest Redwoods List Sponsored by the Tall Trees Club
• Coast Redwoods - Largest & Tallest Photos and Info for Lost Monarch, Del Norte Titan, Stratosphere Giant, Hyperion and more.
• Gymnosperm Database - Sequoia sempervirens champions
• US National Park Service Redwood
• Muir Woods National Monument
• Save the Redwoods League Non-profit organization: education, protection and restoration
• Sempervirens Fund Non-profit organization
• ICT Int. Gallery sensors installation by Dr. Stephen Sillet & team
• Bury Me in Redwood Country Documentary film about coast redwoods
• "Science on the SPOT: Albino redwoods, ghosts of the forest". YouTube video from Quest. KQED. 2010-08-26. http://www.youtube.com/watch?v=os5mZQLpe98. Retrieved 2011-08-14. 
• Humboldt Redwoods State Park (CA) Humboldt Redwoods Interpretive Association
• Preston, Richard. "Climbing the Redwoods" - 2/14-21/2005 New Yorker article about redwoods and climbing.
• More about Sequoia sempervirens:
• Popular Science, November 1943, Saga of the Redwoods

Landsat image of Lake Toba, Indonesia, the largest volcanic crater lake in the world.

Lake Pinatubo, Philippines, formed after the 1991 eruption of Mount Pinatubo.

Space shuttle imagery of Manicouagan Reservoir / Manicouagan impact crater, Canada, the largest impact crater lake in the world.

Heaven Lake, North Korea / China.

Mount Aso crater lake, Japan.

Taal volcano in Lake Taal, Philippines.

Irazú crater lake, Costa Rica.

Maderas crater lake (Ometepe Island), Nicaragua.

Crater Lake in Oregon, USA.

Cuicocha, Ecuador.

Niuafo'ou crater lake, Tonga.

Katmai crater lake, Alaska, USA.

Kelimutu crater lake, Indonesia.

Kerið crater lake, Iceland.

A crater lake is a lake that forms in a volcanic crater or caldera, such as a maar; less commonly and with lower association to the term a lake may form in an impact crater caused by a meteorite, or in an artificial explosion caused by humans. Sometimes lakes which form inside calderas are called caldera lakes, but often this distinction is not made. Crater lakes covering active (fumarolic) volcanic vents are sometimes known as volcanic lakes, and the water within them is often acidic, saturated with volcanic gases, and cloudy with a strong greenish color. Lakes located in dormant or extinct volcanoes tend to have fresh water, and the water clarity in such lakes can be exceptional due to the lack of inflowing streams and sediment.

Lava lakes, a rare phenomenon where a volcanic crater can sustainably contain a significant volume of molten lava, are discussed in a separate article.

Formation[link]

Volcanic crater lakes[link]

Crater lakes form as precipitation within the rim fills the created depression. The water level rises until an equilibrium is reached between the rate of incoming and outgoing water. Sources of water loss singly or together, may include evaporation, subsurface seepage, and in places, surface leakage or overflow when the lake level reaches the lowest point on its rim. At such a saddle location, the upper portion of the lake is contained only by its adjacent natural volcanic dam; continued leakage through or surface outflow across the dam can erode its included material, thus lowering lake level until a new equilibrium of water flow, erosion and rock resistance is established. If the volcanic dam portion erodes rapidly or fails catastrophically, the occurrence produces a breakout or outburst flood. With changes in environmental conditions over time, the occurrence of such floods is common to all natural dam types.

A well-known crater lake, which bears the same name as the geological feature, is Crater Lake in Oregon, USA. It is located in the caldera of Mount Mazama. It is the deepest lake in the United States with a depth of 594 m (1,949 ft). Crater Lake is fed solely by falling rain and snow, with no inflow or outflow at the surface, and hence is one of the clearest lakes in the world.^[1]

The highest volcano in the world, 6,893 metres (22,615 ft) Ojos del Salado in Chile, has a permanent crater lake about 100 metres (300 ft) in diameter at an elevation of 6,390 m (20,960 ft) on its eastern side.^[2] This is most likely the highest lake of any kind in the world.

Due to their unstable environment, some crater lakes exist only intermittently. Caldera lakes in contrast can be quite large and long-lasting; for instance, Lake Toba (Indonesia) formed after its eruption around 70,000 years ago and has an area of over 1,000 square kilometres.

While many crater lakes are picturesque, they can also be deadly. Gas discharges from Lake Nyos (Cameroon) suffocated 1,800 people in 1986, and crater lakes such as Mount Ruapehu's (New Zealand) often contribute to destructive lahars.

Certain bodies of water, although their formation is directly related to volcanic activity, are not usually referred to as crater lakes, including:

• Lakes created by volcanic dams due to lava flowing outside of the volcanic edifice/caldera (such as Garibaldi Lake in Canada, Fuji Five Lakes in Japan),
• Closed atoll lagoons (such as Clipperton lagoon), whose formation process also implies subsequent biogeomorphologic processes,
• Ponds encountered at the bottom of waterfalls occuring in volcanic canyons in a volcanic context but not within a volcanic edifice/caldera (such as Trou de Fer on Réunion Island).

Other kinds of crater lakes[link]

Lakes can also fill impact craters, but these are not usually referred to as crater lakes except in a few isolated cases. Example of such impact crater lakes include Manicouagan in Canada, Lake Bosumtwi in Ghana and Siljan in Sweden.

More rarely they can also fill craters caused by artificial explosions, such as the radioactive Lake Chagan in Kazakhstan.

Other geological features that can be mistaken for a crater lake[link]

Some geomorphological features, when filled with water, can sometimes be confused with crater lakes:

• Pingos (soil-covered ice mounts) whose summital part has collapsed,^[3]
• Sinkholes (karstic holes, also called cenotes), such as Otjikoto Lake in Namibia.

Some circular open-pit mines can also present a similar appearance, such as Big Hole in Kimberley, South Africa, a diamond mine (in a kimberlite pipe) where water has accumulated in the artificially created depression.

List of volcanic crater lakes[link]

This list is incomplete; you can help by expanding it.