Tree of the week

Sequoia

Sequoiadendron giganteum, also known as the giant sequoia, giant redwood or Sierra redwood is a coniferous tree, classified in the family Cupressaceae in the subfamily Sequoioideae. Giant sequoia specimens are the most massive trees on Earth.They are native to the groves on the western slopes of the Sierra Nevada mountain range of California but are grown around the world.

The giant sequoia is listed as an endangered species by the IUCN with fewer than 80,000 remaining in its native California. The tree was introduced to the U.K in 1853 and now there are around 5,000 mature trees.

The Giant sequoia grow to an average height of 50–85 m (164–279 ft) with trunk diameters ranging from 6–8 m (20–26 ft). Record trees have been measured at 94.8 m (311 ft) tall. The specimen known to have the greatest diameter at breast height is the General Grant tree at 8.8 m (28.9 ft). Giant sequoias are among the oldest living organisms on Earth. The oldest known giant sequoia is 3,200–3,266 years old.

Wood from mature giant sequoias is fibrous and brittle; trees would often shatter after they were felled. The wood was unsuitable for construction and instead used for fence posts or match sticks. The giant sequoia is a very popular ornamental tree in many parts of the world. A potential hypothesis for the species name, is in honor of the Cherokee Chief Sequoyah, however there are no surviving records of why the species was named as such.

Giant sequoia specimens are the most massive individual trees in the world.They grow to an average height of 50–85 m (164–279 ft) with trunk diameters ranging from 6–8 m (20–26 ft). Record trees have been measured at 94.8 m (311 ft) tall. Trunk diameters of 17 m (56 ft) have been claimed via research figures taken out of context. The specimen known to have the greatest diameter at breast height is the General Grant tree at 8.8 m (28.9 ft).[8] Between 2014 and 2016, it is claimed that specimens of coast redwood were found to have greater trunk diameters than all known giant sequoias - though this has not been independently verified or affirmed in any academic literature. The trunks of coast redwoods taper at lower heights than those of giant sequoias which have more columnar trunks that maintain larger diameters to greater heights.

The oldest known giant sequoia is 3,200–3,266 years old based on dendrochronology.That tree has been verified to have the fourth-largest lifespan of any tree, after individuals of Great Basin bristlecone pine and alerce. Giant sequoia bark is fibrous, furrowed, and may be 90 cm (3 ft) thick at the base of the columnar trunk. The sap contains tannic acid, which provides significant protection from fire damage. The leaves are evergreen, awl-shaped, 3–6 mm (1⁄8–1⁄4 in) long, and arranged spirally on the shoots.

The giant sequoia regenerates by seed. The seed cones are 4–7 cm (1+1⁄2–3 in) long and mature in 18–20 months, though they typically remain green and closed for as long as 20 years. Each cone has 30–50 spirally arranged scales, with several seeds on each scale, giving an average of 230 seeds per cone. Seeds are dark brown, 4–5 mm (0.16–0.20 in) long, and 1 mm (0.04 in) broad, with a 1-millimeter (0.04 in) wide, yellow-brown wing along each side. Some seeds shed when the cone scales shrink during hot weather in late summer, but most are liberated by insect damage or when the cone dries from the heat of fire. Young trees start to bear cones after 12 years.

Trees may produce sprouts from their stumps subsequent to injury, until about 20 years old; however, shoots do not form on the stumps of mature trees as they do on coast redwoods. Giant sequoias of all ages may sprout from their boles when branches are lost to fire or breakage.

A large tree may have as many as 11,000 cones. Cone production is greatest in the upper portion of the canopy. A mature giant sequoia disperses an estimated 300–400 thousand seeds annually. The winged seeds may fly as far as 180 m (590 ft) from the parent tree.

Lower branches die readily from being shaded, but trees younger than 100 years retain most of their dead branches. Trunks of mature trees in groves are generally free of branches to a height of 20–50 m (70–160 ft), but solitary trees retain lower branches.

The natural distribution of giant sequoias is restricted to a limited area of the western Sierra Nevada, California. As a paleoendemic species,[14] they occur in scattered groves, with a total of 81 groves (see list of sequoia groves for a full inventory), comprising a total area of only 144.16 km2 (35,620 acres). Nowhere does it grow in pure stands, although in a few small areas, stands do approach a pure condition. The northern two-thirds of its range, from the American River in Placer County southward to the Kings River, has only eight disjunct groves. The remaining southern groves are concentrated between the Kings River and the Deer Creek Grove in southern Tulare County. Groves range in size from 12.4 km2 (3,100 acres) with 20,000 mature trees, to small groves with only six living trees. Many are protected in Sequoia and Kings Canyon National Parks and Giant Sequoia National Monument.

The giant sequoia is usually found in a humid climate characterized by dry summers and snowy winters. Most giant sequoia groves are on granitic-based residual and alluvial soils. The elevation of the giant sequoia groves generally ranges from 1,400–2,000 m (4,600–6,600 ft) in the north, to 1,700–2,150 metres (5,580–7,050 ft) to the south. Giant sequoias generally occur on the south-facing sides of northern mountains, and on the northern faces of more southerly slopes.

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 sequoia groves are currently undergoing a gradual decline in density since European settlement.

While the present day distribution of this species is limited to a small area of California, it was once much more widely distributed in prehistoric times, and was a reasonably common species in North American and Eurasian coniferous forests until its range was greatly reduced by the last ice age. Older fossil specimens reliably identified as giant sequoia have been found in Cretaceous era sediments from a number of sites in North America and Europe, and even as far afield as New Zealand and Australia.

Wood from mature giant sequoias is highly resistant to decay, but due to being fibrous and brittle, it is generally unsuitable for construction. From the 1880s through the 1920s, logging took place in many groves in spite of marginal commercial returns. The Hume-Bennett Lumber Company was the last to harvest giant sequoia, going out of business in 1924.[36] Due to their weight and brittleness, trees would often shatter when they hit the ground, wasting much of the wood. Loggers attempted to cushion the impact by digging trenches and filling them with branches. Still, as little as 50% of the timber is estimated to have made it from groves to the mill. The wood was used mainly for shingles and fence posts, or even for matchsticks.

Pictures of the once majestic trees broken and abandoned in formerly pristine groves, and the thought of the giants put to such modest use, spurred the public outcry that caused most of the groves to be preserved as protected land. The public can visit an example of 1880s clear-cutting at Big Stump Grove near General Grant Grove. As late as the 1980s, some immature trees were logged in Sequoia National Forest, publicity of which helped lead to the creation of Giant Sequoia National Monument.[citation needed]

The wood from immature trees is less brittle, with recent tests on young plantation-grown trees showing it similar to coast redwood wood in quality. This is resulting in some interest in cultivating giant sequoia as a very high-yielding timber crop tree, both in California and also in parts of western Europe, where it may grow more efficiently than coast redwoods. In the northwest United States, some entrepreneurs have also begun growing giant sequoias for Christmas trees. Besides these attempts at tree farming, the principal economic uses for giant sequoia today are tourism and horticulture.

www.theaviaryclub.org

info@theaviaryclub.org

Aviary Club of Nigeria

ACN MEDIA