A model of the growth of juvenile radiata pine in the central North Island of New Zealand: links with older models and rotation-length analyses of the effects of site preparation

Data from 27 site preparation experiments were used to construct a model that predicts growth, survival and size class distributions of radiata pine with respect to altitude, weed control, cultivation, fertilisation, and initial stocking during the first five years after planting. Only stand values, however, are used in this paper. The question of linking the model with existing growth and yield models for older crops is discussed, and a theoretical structure is proposed that clarifies assumptions required if the models are jointly used to evaluate the worth of establishment practices throughout complete crop rotations. It was found that the initial growth model generally predicted similar basal area growth rates to those of the Pumice Plateau Model (PPM88), a growth model for older crops, in age ranges where the two models overlapped, but some of the assumptions required for rotation-length analyses need further testing. Measurements over 8 years in a designed experiment examining alternative site preparation strategies showed that PPM88 was insensitive to the effects of site preparation in predicting growth that occurred after the establishment phase.