Description and interpretation of the growth of spruces by means of the Evolon-model

The growth of the mean stand height of spruces (Picea abies) for different site classes is described using the Evolon model. The data are taken from g rowth tables established by A. v. GUTTENBERG (1915). As a result of a param eter optimisation we obtain parabolic growth (kappa = 0.41) for the initial growth phase and hyperbolic asymtotic approximation (h = 1.67) to the satu ration value during the later saturation phase. The values for the scale-in dependent parameters kappa and lambda of the Evolon model can be interprete d as follows: The initial growth process is mainly determined by the geneti c information of the given species. This growth phase is described by the p arameter kappa. In the later saturation phase, however, ecological limitati ons come into effect. During this phase the tree undergoes an adaptation pr ocess to its individual growth limit caused by the site conditions. This sa turation process is described by the parameter lambda. Three parameters of the Evolon-model do not show a clear dependence on the site conditions. Onl y two parameters, which represent tree heights, depend clearly on the site conditions. The description of the data by the Evolon-model is remarkably b etter than the description by the commonly used Richards model. Simultaneou sly the Evolon model provides more realistic growth predictions than the Ri chards-model does.