A compatible growth-density stand model derived from a distance-dependent individual tree model

Abstract

A compatible growth-density stand model is developed for simulating forest stands with uniformly distributed trees (e.g., square spacing, equilateral triangle spacing, and 1:1.5 row to column ratio tree distribution patterns). The model is based on a distance-dependent individual-tree competition model. The independent variable in the individual-tree model is Hegyi's (1974) diameter-distance competition index with n = 8. The derived growth density stand model satisfies a necessary boundary condition (i.e., stand growth is zero either when stand density is zero or when stand density reaches to a very high level). The stand density which maximizes stand growth rate can be calculated with this stand model. It is found that stands with an equilateral triangle tree distribution pattern have the greatest growth rate among the three uniform stands. Stand growth in measured forests is more than 10% lower than that predicted in uniform stands. Simulation comparisons suggest that the uneven distribution of trees in such stands can reduce stand growth.