A Simple Stand Growth Model Based on Canopy Dynamics and Biomechanics

Abstract

A new approach to simulating net forest growth is presented. The model is based on density effects on mean crown dimensions and the stem geometry required to counteract the bending moment generated from wind action on the crown. Stem geometry is based on the constant-stress principle of stem formation. Various structural and growth properties of hypothetical loblolly pine stands growing on a range of site indexes and with a range of initial tree densities are calculated with the model and compared with published values and well-known patterns. Size-density relations calculated with the model are consistent with converging, curvilinear lines reported for slash pine and loblolly pine plotted on log-transformed axes. Linear relationships between mean crown length and mean spacing agree with observations from various coniferous species, and culmination of current annual increment corresponds with the rapid changes in canopy structure reported with Sitka spruce. Overestimations of mean annual increment appear to result from differences in canopy dynamics in the loblolly pine plots used to fit the model's regression equations and the canopy dynamics in the loblolly pine plantations used for comparisons. The model has the potential to create an alternative approach for accessing environmental changes on forest growth and yield to complement extant carbon-balance models. FOR .S CI. 59(3):335-344.