A Site Dependent Simultaneous Growth Projection Model for Pinus kesiya Plantations in Zambia and Zimbabwe

Abstract

Abstract The aim of this study was to create a stand level yield model for Pinus kesiya (Royle × Gordon) plantations in Zambia and Zimbabwe based on the simultaneous projection model approach. The purpose was to prepare prediction models for the measurable and allometrically related stand variables which characterize the development of planted P. kesiya stands. The modeled stand characteristics are assessable in the inventories of forest plantations and are frequently employed in traditional stand yield tables and modern growth simulators. Special attention was paid to the selection of flexible nonlinear model forms that are simple and stable. Two model forms were developed: (1) a polymorphic and base age invariant site index equation, used as a growth projection model for stand dominant height, and (2) a stand volume prediction model based on Honer's single tree volume model. The projection form of the site index equation was obtained using the algebraic difference approach to solve analytically the rate parameter of the autocatalytic growth model. The simultaneous growth projection model included a model for basal area median diameter. The basal area median diameter was also used as a predictor of stand basal area. This improved the accuracy of stand basal area predictions. A model for the basal area median diameter also makes it possible to apply theoretical diameter distributions for the prediction of future stand stages. FOR. SCI. 48(3):518–529.