MODELLING DIAMETER DISTRIBUTION IN EVEN-AGED AND UNEVEN-AGED FOREST STANDS

Abstract

Five distributions, Weibull, gamma, Johnson S_B, log normal and generalised normal, are compared in terms of their ability to model diameter data in even-aged and uneven-aged forest stands. Moments ratio diagrams of various statistical distributions are applied as a measure of the flexibility of the distribution in regard to their changes in shape. Some of the strengths and weaknesses of the distributions that have been used for describing diameter distributions in even-aged and uneven-aged stands are discussed. Data were
obtained from 16 uneven-aged stands of mixed species located at Bukit Lagong Forest Reserve, Kepong, Selangor, and 9 even-aged stands of Acacia mangium species located at Kemasul Forest Reserve, Pahang. All the stands were from plantations and the ages ranged from 5 to 22 y.