Publication Date:
1992-03-01
Description:
A method of estimating individual tree volume by importance sampling is developed that is based on the cylindrical shells volume integral. The cylindrical shells volume integral conceptualizes a tree stem as being a solid of revolution comprising a collection of thin cylinders. Previous applications of importance sampling to individual tree volume estimation have been based on the method of slices integral, in which the tree stem is viewed as a solid of revolution comprising a collection of thin disks. Both approaches provide unbiased estimates of individual tree volume for any monotonic tree taper, if it can be assumed that the tree is circular in cross section. An advantage of the cylindrical shells approach is that total tree height need not be measured to accomplish the estimation process, as would be required when using importance sampling estimators based on the method of slices integral. Tree volume estimation via importance sampling based on the cylindrical shells integral requires measurement of stump cross-sectional area, which is usually more easily obtained than total or merchantable height measurements. Both approaches require one or more upper stem diameter measurements. Computer simulation shows that use of antithetic variates with importance sampling reduces the variance of the volume estimate significantly when a paraboloid is used as a proxy taper function.
Print ISSN:
0045-5067
Electronic ISSN:
1208-6037
Topics:
Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
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