Parameter Estimation of Nonlinear Models in Forestry.

Partial derivatives of the negative exponential, monomolecular, Mitcherlich, Gompertz,
logistic, Chapman-Richards, von Bertalanffy, Weibull and the Richard’s nonlinear
growth models are presented. The application of these partial derivatives in estimating
the model parameters is illustrated. The parameters are estimated using the Marquardt
iterative method of nonlinear regression relating top height to age of Norway spruce
(Picea abies L.) from the Bowmont Norway Spruce Thinning Experiment. Formulas
that provide good initial values of the parameters are specified. Clear definitions of the
parameters of the nonlinear models in the context of the system being modelled are
found to be critically important in the process of parameter estimation.