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Tree crown measurement
The crown of a tree consists of the mass of foliage and branches growing outward from the trunk of the tree. The average crown spread is the average horizontal width of the crown, taken from dripline to dripline as one moves around the crown. Some listings will also list the maximum crown spread which represents the greatest width from dripline to dripline across the crown.〔Blozan, Will. 2004, 2008. The Tree Measuring Guidelines of the Eastern Native Tree Society. http://www.nativetreesociety.org/measure/Tree_Measuring_Guidelines-revised1.pdf Accessed March 4, 2013.〕〔(Blozan, Will. 2006. Tree Measuring Guidelines of the Eastern Native Tree Society. ) ''Bulletin of the Eastern Native Tree Society'', Volume 1, Number 1, Summer 2006. pp. 3–10.〕〔(American Forests Measuring Guidelines. ) Accessed March 4, 2013.〕 Other crown measurements that are commonly taken include limb length, crown volume, and foliage density. Canopy mapping surveys the position and size of all of the limbs down to a certain size in the crown of the tree and is commonly used when measuring the overall wood volume of a tree.
Average crown spread is one of the parameters commonly measured as part of various champion tree programs and documentation efforts. Other commonly used parameters, outlined in tree measurement, include height, girth, and volume. Additional details on the methodology of tree height measurement, tree girth measurement, and tree volume measurement are presented in the links herein. American Forests, for example, uses a formula to calculate Big Tree Points as part of their Big Tree Program〔 that awards a tree 1 point for each foot of height, 1 point for each inch of girth, and ¼ point for each foot of crown spread. The tree whose point total is the highest for that species is crowned as the champion in their registry. The other parameter commonly measured, in addition to the species and location information, is wood volume. A general outline of tree measurements is provided in the article tree measurement and more detailed instruction in taking these basic measurements is provided in “The Tree Measuring Guidelines of the Eastern Native Tree Society” by Will Blozan.〔〔
==Largest recorded crown spreads==
Data on greatest crown spread is somewhat limited as this parameter is not measured as frequently as are tree height and trunk girth. The largest recorded is the "Monkira Monster" (''Eucalyptus microtheca'') located at the Neuragully Waterhole in southwestern Queensland, Australia, which measured 239 feet in 1954.〔 Accessed March 8, 2013.〕 A raintree (''Albizia saman'') in Venezuela was measured to have a crown spread of 207 feet in 1857. It reportedly is still living, but in poor health.〔 A University of Connecticut site〔(University of Connecticut. Samanea tubulosa (Benth.) Barneby & Grimes. ) Accessed March 8, 2013.〕 suggests that in the wild they may have crown spreads up to 80 meters. Robert Van Pelt measured a crown spread of 201 feet of a kapok tree (Ceiba pentandra) at Barro Colorado Island, Panama, in 2003.〔
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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