An investigation of a bivariate distribution approach to modeling diameter distributions at two points in time

dc.contributor.authorKnoebel, Bruce R.en
dc.contributor.committeechairBurkhart, Harold E.en
dc.contributor.committeememberBuhyoff, Gregory J.en
dc.contributor.committeememberOderwald, Richarden
dc.contributor.committeememberReynolds, Marion R. Jr.en
dc.contributor.committeememberSmith, David Williamen
dc.description.abstractA diameter distribution prediction procedure for single species stands was developed based on the bivariate S<sub>B</sub> distribution model. The approach not only accounted for and described the relationships between initial and future diameters and their distributions, but also assumed future diameter given initial diameter to be a random variable. While this method was the most theoretically correct, comparable procedures based on the definition of growth equations which assumed future diameter given initial diameter to be a constant, sometimes provided somewhat better results. Both approaches performed as well, and in some cases, better than the established methods of diameter distribution prediction such as parameter recovery, percentile prediction, and parameter prediction. The approaches based on the growth equations are intuitively and biologically appealing in that the future distribution is determined from an initial distribution and a specified initial-future diameter relationship. ln most appropriate. While this result simplified some procedures, it also implied that the initial and future diameter distributions differed only in location and scale, not in shape. This is a somewhat unrealistic assumption, however, due to the relatively short growth periods and the alterations in stand structure and growth due to the repeated thinnings, the data did not provide evidence against the linear growth equation assumption. The growth equation procedures not only required the initial and future diameter distributions to be of a particular form, but they also restricted the initial-future diameter relationship to be of a particular form. The individual tree model, which required no distributional assumptions or restrictions on the growth equation, proved to be the better approach to use in terms of predicting future stand tables as it performed better than all of the distribution-based approaches. For the bivariate distribution, the direct fit, parameter recovery, parameter prediction and percentile prediction diameter distribution prediction techniques, implied diameter relationships were defined. Evaluations revealed that these equations were both accurate and precise, indicating that the accurate specification of the initial distribution and the diameter diameter distribution.en
dc.description.degreePh. D.en
dc.format.extentxv, 259 leavesen
dc.publisherVirginia Polytechnic Institute and State Universityen
dc.relation.isformatofOCLC# 12876669en
dc.rightsIn Copyrighten
dc.subject.lccLD5655.V856 1985.K563en
dc.subject.lcshForests and forestry -- Forecasting -- Statistical methodsen
dc.subject.lcshForests and forestry -- Measurementen
dc.subject.lcshTrees -- Growth -- Forecastingen
dc.titleAn investigation of a bivariate distribution approach to modeling diameter distributions at two points in timeen
dc.type.dcmitypeTexten Polytechnic Institute and State Universityen D.en


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