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''Sequoiadendron giganteum'' (giant sequoia, giant redwood, Sierra redwood, Sierran redwood, or Wellingtonia) is the sole living species in the genus ''Sequoiadendron'', and one of three species of coniferous trees known as redwoods, classified in the family Cupressaceae in the subfamily Sequoioideae, together with ''Sequoia sempervirens'' (coast redwood) and ''Metasequoia glyptostroboides'' (dawn redwood). The common use of the name "sequoia" generally refers to ''Sequoiadendron giganteum'', which occurs naturally only in groves on the western slopes of the Sierra Nevada Mountains of California. It is named after Sequoyah (1767–1843), the inventor of the Cherokee syllabary. ==Description== Giant sequoias are the world's largest single trees and largest living thing by volume. Giant sequoias grow to an average height of and in diameter. Record trees have been measured to be in height and over in diameter. The oldest known giant sequoia based on ring count is 3,500 years old. Giant Sequoias are among the oldest living things on Earth. Sequoia bark is fibrous, furrowed, and may be thick at the base of the columnar trunk. It provides significant fire protection for the trees. The leaves are evergreen, awl-shaped, long, and arranged spirally on the shoots. The seed cones are long and mature in 18–20 months, though they typically remain green and closed for up to 20 years; each cone has 30–50 spirally arranged scales, with several seeds on each scale, giving an average of 230 seeds per cone. The seed is dark brown, long and broad, with a wide, yellow-brown wing along each side. Some seeds are shed when the cone scales shrink during hot weather in late summer, but most are liberated when the cone dries from fire heat or is damaged by insects. The giant sequoia regenerates by seed. Young trees start to bear cones at the age of 12 years. Trees up to about 20 years old may produce stump sprouts subsequent to injury, but unlike coast redwood, shoots do not form on the stumps of mature trees. Giant sequoias of all ages may sprout from their boles when branches are lost to fire or breakage. At any given time, a large tree may be expected to have about 11,000 cones. Cone production is greatest in the upper portion of the canopy. A mature giant sequoia has been estimated to disperse 300,000–400,000 seeds per year. The winged seeds may be carried up to from the parent tree. Lower branches die fairly readily from shading, but trees less than 100 years old retain most of their dead branches. Trunks of mature trees in groves are generally free of branches to a height of , but solitary trees will retain low branches. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Sequoiadendron giganteum」の詳細全文を読む スポンサード リンク
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