Adjusting a process-based growth model for varying site conditions through parameter estimation

The problem of estimating the parameters of a process-based growth model using typical stand growth measurements is studied. The data consists of measurements of diameter, height, number of trees, and live crown ratio obtained from plots representing different site qualities. Analysis of the identifiability of model parameters is made which shows 1) that the structure of the model makes certain parameter combinations unidentifiable, and 2) that the data at hand do not support all the parameters. It is not possible to reduce the number of parameters in the model without losing its biological significance. The model has been modified slightly on the basis of identifiability analysis and initial estimations and the set of parameters to be estimated has been restricted. Measurements of diameter, height, density, and live crown ratio are needed for reliable fitting of the model. -from Authors