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Logging in the Californian Sierra Nevada arose from the need to support growing communities throughout California. The Gold Rush created a high demand for timber in housing construction, mining procedures, and building railroads. In the early days, harvesting of forests were unregulated and within the first 20 years after the gold rush, a third of the timber in the Sierra Nevada was logged. Concern for the forests rose and created a movement towards conservation at the turn of the 19th century, leading to the creation of state and national parks (Yosemite, Sequoia and Grant Grove) and forest reserves, bringing forest land under regulation. Between 1900 and 1940, agencies like the U.S. Forest Service and The National Park Service regulated the use of the Sierra Nevada’s resources.〔 The economy boom after World War II dramatically increased timber production in the Sierras using clear-cutting as the dominant form of logging.〔 In addition, the California Forest Practice Act, or the Z'Berg-Nejedly Forest Practice Act was enacted in 1973 to regulate private timberland holdings. ==Methods== Logging on privately owned and state-managed timberland in California is restricted to silvicultural techniques defined within by the California Forest Practice Rules. These including: single tree selection, seed tree, shelterwood, group selection, variable retention, and clear-cutting management techniques.〔(【引用サイトリンク】title=Forest Practice )〕 * clear-cutting involves removal of all trees from a tract of land within a 20-acre area followed by replanting if the new ingrowth of seedlings does not meet stocking levels outlined by the Forest Practice Rules. This can result in disturbances in the Sierra Nevada environment by creating patches of densely packed, single-species, same-aged, tree plantations, but may also benefit the forest stand by removing large pockets of pest or fungal infection and improving forest health over the stand as a whole. * Single Tree Selection involves removal of individual trees in a prescribed fashion. Usually this is done across the size distribution of trees in a stand and mimics to some degree the natural mortality pattern and rate within a stand. Low-impact logging meets current needs without compromising the ability of future generations to meet their needs. This typically means smaller periodic harvests and removing the worst trees to eliminate danger to high value trees. Forest management, concerning harvest rate, reforestation, erosion control, and stream protection, is key to limiting environmental degradation from timber harvesting and to protect future resources Logging on federal timberland in California follow national regulations. 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「Logging in the Sierra Nevada」の詳細全文を読む スポンサード リンク
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