Oscar Garcia
Forest Research Institute, New Zealand Forest Service, Rotorua,
New Zealand.
A methodology for modelling the growth of managed even-aged stands has been developed. The state of a stand is represented by a number of variables --- typically basal area, stocking, and top height. Changes of state through growth and mortality are given by a system of differential equations which are a multivariate generalisation of the Bertalanffy-Richards model. For estimation purposes random perturbations are included, and the parameters are estimated by maximum likelihood based on the resulting stochastic differential equations. The growth equations are complemented by models for thinning, early growth, volume per hectare, and diameter distributions. The methods have been applied to the development of a model for \emph{Pinus radiata} D. Don in Golden Downs Forest, Nelson, with satisfactory results.