|
Tree volume is one of many parameters that are measured to document the size of individual trees. Tree volume measurements serve a variety of purposes, some economic, some scientific, and some for sporting competitions. Measurements may include just the volume of the trunk, or the volume of the trunk and the branches depending on the detail needed and the sophistication of the measurement methodology. Other commonly used parameters, outlined in Tree measurement, include the height, girth, and crown spread. Additional details on the methodology of Tree height measurement, Tree girth measurement, and Tree crown measurement are presented in the links herein. Volume measurements can be achieved via tree climbers making direct measurements or through remote methods.〔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 F. and Riddle, Jess D. 2006. Tsuga Search progress report October 2006. http://www.nativetreesociety.org/tsuga/oct2006/tsuga_search_oct2006.htm〕 In each method, the tree is subdivided into smaller sections, the dimensions of each section are measured and the corresponding volume calculated. The section volumes are then totaled to determine the overall volume of the tree or part of the tree being modeled. In general most sections are treated as frustums of a cone, paraboloid, or neiloid, where the diameter at each end and the length of each section is determined to calculate volume. Direct measurements are obtained by a tree climber who uses a tape to measure the girth at each end of a segment along with its length. Ground-based methods use optical and electronic surveying equipment to remotely measure the end diameters and the length of each section. The largest trees in the world by volume are all giant sequoias in King’s Canyon National Park. They have been previously reported by trunk volume as: General Sherman at 52,508 cubic feet (1,486.9 m3); General Grant at 46,608 cubic feet (1,319.8 m3); and President at 45,148 cubic feet (1,278.4 m3). The largest non-giant sequoia tree currently standing, Lost Monarch, is, at 42,500 cubic feet (1,203.5 m3), larger than all but the top five largest living giant sequoias. The Lost Monarch is a Coast Redwood (Sequoia sempervirens) tree in Northern California that is 26 feet (7.9 m) in diameter at breast height (with multiple stems included), and 320 feet (98 m) in height. In 2012 a team of researchers led by Stephen Sillett did a detailed mapping of the branches of the President tree and calculated the volume of the branches to be 9,000 cubic feet (250 m3). This would raise the total volume for the President from 45,000 cubic feet to 54,000 cubic feet (1,500m3) surpassing the volume of the General Grant Tree.〔Cone, Trace. December 1, 2012. Upon further review, giant sequoia tops a neighbor. http://www.boston.com/news/nation/2012/12/01/upon-further-review-giant-sequoia-tops-neighbor/K0SwEhJhCqjzxAXX3OBVGK/story.html, Boston.com Accessed March 14, 2013.〕〔Quammen, David. 2012. Scaling a Forest Giant. National Geographic Magazine, Vol. 222, No. 6, December 2012, pp. 28-41.〕 It should be noted the branch volume of the General Grant and General Sherman Trees have yet to be measured in this detail. ==Direct Volume Measurements – Trunk== Tree climbers can physically measure the height and circumference of a tree using a tape. The distance from the highest climb point and the top of the tree is measured using a pole that extends from the tree top to the anchor point of the tape. This height is noted and the diameter of the tree is measured at that point. The climber then rappels down the tree measuring the trunk circumference by tape wrap at different heights with the height of each measurement referenced to the fixed tape running down the trunk. Direct trunk measurements are obtained by a tree climber.〔〔 The climber will ascend into the tree until he reaches the highest safe climbing point. Once this point is reached, the climber drops a weighted throw line straight to the ground. A measuring (reference) tape is then attached via a small carabineer to the dropped throw line and pulled up to the top, following the vertical path of the weight’s descent. The tape is affixed to the trunk at this point via several thumbtacks at this point and allowed to hang freely down the trunk. The exact position of the tack relative to the top of the tree is noted. If the top of the tree was not safely reachable a pole or stick is used to assist in measuring the remaining distance to the high point of the tree. The climber pulls up an extendable pole and uses it to reach to the top of the tree from the point at the upper end of the tape. If not vertical, the slope of the leaning pole is measured and the length of the pole is measured. The vertical distance added by the pole to the tape length is (sin Θ x pole length). The lower end of the tape is terminated at the base of the tree. If on sloping ground this is the mid-slope point between the lowest and highest sides of the tree. The total height of the tree is equal to the measured distance from the base at mid-slope to the upper end of the tape where affixed to the tree plus the vertical height measured to the actual top of the tree. Girth measurements are made by wrapping the tape around the tree perpendicular to the bole at successive intervals as the climber rappels down the tree. All points of measurement are referenced for height above ground as measured on the fixed reference tape. Measurement intervals are subjectively chosen based on changes in trunk taper. An area where a change in profile is observed (in or out) is measured with a tape. Clear sections of trunk are selected so as to not include branch collars, burls, etc. For greatest accuracy, measurements are taken on single-trunked trees at no more than 10 foot (3 m) intervals.〔〔 Additional measurements are generally required where the trunk branches or bifurcates or where there are trunk reiterations. Reiterations are identified by an upturned branch that had gained apical dominance and formed an additional branch supporting trunk. Reiteration lengths are terminated at the point of trunk contact. Trunk reiterations are measured and added to the final trunk volume. A bifurcation is defined as a split or fork in the trunk that forms two or more often similarly sized ascending trunks. Bifurcations often form an irregularly shaped fused section that cannot be accurately measured with a tape for the purpose of computing cross-sectional area. All bifurcation lengths are terminated at estimated pith origination from the main stem.〔〔 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「tree volume measurement」の詳細全文を読む スポンサード リンク
|