Characterizing Diameter Distributions by the use of the Weibull Distribution

Abstract

The well known Weibull distribution is fitted to sampled diameter distributions from 120 Sitka spruce stands and 90 stands of other conifer species, these being spread throughout Great Britain and having a wide range of ages. The parameters of the Weibull distribution, estimated by the method of Maximum Likelihood, are then regressed, using weighted least squares, upon mean diameter at breast height, d say hence yielding a family of Weibull distributions indexed by d. The effect of using minimum sampled dbh as an additional index is also examined. The results are compared with the Forestry Commission's Stand Tables and are found to be an improvement.