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Redwoods

 

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Overview
They are the giants of the earth, bigger than dinosaurs or whales. They tower over 67 meters (220 feet) high, outlive most other forms of life, and have inspired pioneers, poets, and presidents alike. They are the redwoods of California. Actually, the term "redwood" refers to several species. For example, the towering coast redwoods (Sequoia sempervirens) grow in the mild, misty climate along the Pacific coast of California and southern Oregon. The oldest among them is 2,200 years; the tallest measures 113 meters (370 feet). Their cousins, the giant sequoias (Sequoiadendron giganteum), live in the harsher climate of the Sierra Nevada mountains. These trees are more massive and live even longer. Although all redwoods are valuable natural resources, the coast redwoods are the focus of this Newton's Apple segment. Like all trees, the coast redwoods have developed a highly successful root, trunk, and leaf system using air, water, and sunlight to live and reproduce. The shallow roots of the redwood can spread laterally over 75 meters (250 feet) as they collect and send water and minerals to the leaves. The leaves, in turn, create food through photosynthesis and send the nutrients back down through the trunk to the roots. The unusual characteristics of the redwood's trunk have enabled it to survive the centuries. The outer layer of a tree's trunk, or bark, is made up of dead cells. In redwoods, the bark is fibrous and thick, often measuring 30.5 centimeters (one foot). The thickness of the bark and its lack of resin help redwoods resist damage from forest fires. Tannic acid in the bark helps the trees resist disease and insect infestation. The layers under the bark sustain the life of the tree. The phloem, cambium, sapwood, and heartwood each plays a role in the healthy growth of the redwood tree. Because of the high demand for their wood, coast redwoods have long been a target of the lumber industry. Ecologically, forests have felt this impact. Without the trees' roots in place, erosion plays havoc by clogging up streams with silt and destroying the watershed. Conservationist John Muir may have spoken for everyone working to save the redwoods when he wrote, "The clearest way into the Universe is through a forest wilderness." Conservationists and the logging industry have long been at odds. How would you explain the issues? What do you think our national policy should be toward logging the forests? Can you identify areas near your home or school that suffer from ecological stress?

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