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Old Tjikko is a 9,550-year-old Norway Spruce, located on Fulufjället Mountain of Dalarna province in Sweden. Old Tjikko originally gained notoriety as the "world's oldest tree" but is instead the oldest living clonal Norway Spruce, as there are older clonal trees, while no individual tree reaches Old Tjikko's age. The age of the tree was determined by carbon dating of genetically matched plant material collected from under the tree, not by dendrochronology, or counting tree rings. The trunk itself is estimated to be only a few hundred years old, but the plant has survived for much longer due to a process known as layering (when a branch comes in contact with the ground, it sprouts a new root), or vegetative cloning (when the trunk dies but the root system is still alive, it may sprout a new trunk). ==Discovery and details== Old Tjikko is estimated to be at least 9,550 years old, making it the world's oldest known individual vegetatively cloned tree. It stands tall and is located on Fulufjället Mountain of Dalarna province in Sweden. For thousands of years, the tree appeared in a stunted shrub formation (also known as a krummholz formation) due to the harsh extremes of the environment in which it lives. During the warming of the last century, the tree has sprouted into a normal tree formation. The man who discovered the tree, Leif Kullman (Professor of Physical Geography at Umeå University), has attributed this growth spurt to global warming, and given the tree its nickname "Old Tjikko" after his late dog.〔 The tree has survived for so long due to vegetative cloning. The visible tree is relatively young, but it is part of an older root system which dates back thousands of years. The trunk of the tree may die and regrow multiple times, but the tree's root system remains intact and in turn sprouts another trunk. The trunk may only live for about 600 years, and when one trunk dies another eventually grows back in its place. Also, each winter, heavy snow may push the tree's low-lying branches to ground level, where they take root and survive to grow again the next year in a process known as layering. Layering occurs when a tree's branch comes in contact with the earth, and new roots sprout from the contact point. Other trees, such as coast redwoods and western redcedars are known to reproduce by layering. The tree's age was determined by carbon-14 dating of the root system, which found roots dating back to 375, 5,660, 9,000, and 9,550 years. Carbon dating is not accurate enough to pin down the exact year the tree sprouted from seed, but given the estimated age the tree is supposed to have sprouted around 7550 BC. For comparison, the invention of writing (and thus, the beginning of recorded history) did not occur until around 4000 BC. Researchers have found a cluster of around 20 spruce trees in the same area, all over 8,000 years old.〔(【引用サイトリンク】title=World’s oldest living tree discovered in Sweden )〕 Previous researchers considered the Norway spruce species to be a relative newcomer to Sweden, with theories postulating the tree migrated into the area around 2,000 years ago. Trees much older than 10,000 years would be practically impossible in Sweden, because until around 11,000 years ago the area was in the grip of a world-wide ice age.〔 Nature conservancy authorities are considering putting a fence around the tree to protect it from possible vandals or trophy hunters. 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「Old Tjikko」の詳細全文を読む スポンサード リンク
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