MODELLING BRANCH DEVELOPMENT FOR FOREST MANAGEMENT

The locations and dimensions of branches encased within a tree-stem influence the appearance, strength, and ultimately the end-use of timber. A model which predicts branch development through time would enable the New Zealand forest industry to obtain better estimates of log and timber grades at time of harvest from inventory information collected at any time during the rotation. Choosing the appropriate level of detail with which to model branch development for forest management requires a compromise between understanding growth processes, data collection costs, model accuracy and precision, and suitability for use by forest management. The approach chosen was to model the occurrence of branch clusters within annual shoots on Pinus radiata D. Don, and to model the diameter growth of branches at the point of attachment to the tree stem. This approach has several major advantages. It is based on an understanding of branch morphology and basic growth processes. It allows the utilisation of existing models of annual height development, stem taper, and growth which are based on extensive field measurements. We believe that the model structure is cost-efficient in terms of the data requirements. The increased costs of data collection to develop a more detailed model of the full extent of the crown would not be matched by a similar increase in worth to the forest industry.