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Redwoods

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What is the largest living thing on earth? A redwood tree. Surprised?

The redwood tree dates back to about 110 million years ago, being most abundant on earth approximately 65 million years ago. They have been steadily declining since. Redwoods belong to the Taxodiaceae family. There are three tree species that are referred to as redwoods. The Sequoia (Sequoia sempervirens) or coast redwood is found along the northern Californian coast. These trees can grow to be over 100 meters (330 feet) tall, 20 feet in diameter and can live for 2000-4000 years. The Sierra redwood (Sequoiadendron gigantea) is found in isolated groves in the Sierra Nevada Mountains. Sierra redwoods only reach heights of about 95 meters (310 feet) but have massive trunks (12 meters or 40 feet in diameter). Lastly, the Dawn redwood (metasequoia or glyptostroboides) is found in a small valley in central China. Dawn redwoods reach heights of only 45 meters or 146 feet, but are still huge.

How have redwoods managed to survive so long? They have several survival strategies.

Redwoods grow very tall and extremely fast. They out-compete other trees for the sun.

Their bark is very thick and acts as a heat shield when exposed to fire. But, if there is a crack or opening in the bark, fire can penetrate and burn the heartwood (or heartwood). The tree continues to survive or grow as long as the cambium (the living part of the tree) is not harmed. These large openings in redwood trees are called goosepens.

The bark contains tannins, which discourage insect pests such as termites and ants.

There are many ways to get a new redwood. A redwood that has been knocked over will continue to grow from its limbs, sometimes producing a new tree. Occasionally, newer trees form a circle around an older tree or stump - clones of the original tree. This circle of trees is called a fairy ring or cathedral spire. Strangest of all are burls - knobby growths that appear similar to cancer in humans but are not harmful to the plant. Chemical signals hold the burl dormant until the tree dies or the tree is stressed, which lessening the chemical signal. The burl then begins to grow. Burls sometimes grow at the base of the redwood tree (or redwood burl)or on the trunk. Lastly, it is possible to grow redwoods from seeds no larger than the tomato's.

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