A model of the juvenile growth and survival of Pinus radiata D. Don -: Adding the effects of initial seedling diameter and plant handling

Initial ground line diameter (GLD) of Pinus radiata D.Don and the care of trees during transport to the field growing site affect subsequent tree growth and survival. An existing model of juvenile growth had not included these effects, and so a new model was created that represented their effects on growth, survival and uniformity. The new model was built with cohorts defined by each initial GLD class and with quality of tree stock handling as an extra independent variable, using data from 17 experiments. Weibull distributions representing the size classes developing within each cohort enabled the model to represent interchanges in dominance, and added to the range of questions that could be answered using the model. Reducing quality of handling and reducing initial GLD decreased growth, survival, and crop uniformity. Changes in small GLDs were more important than changes in large ones. The final model represented the effects of initial ground line diameter, tree stock handling (careful, timely planting compared to rough, poorly scheduled planting), site quality, and site preparation on growth of radiata pine in the central North Island of New Zealand in a way that allows managers to evaluate the impacts of seedling grading.