Prediction of Understory Tree Height Growth in Northern Hardwood Stands

Abstract Stand table projection methodology was used to describe the growth of under-story reproduction trees by height class and species in uneven-aged northern hardwood stands in Wisconsin. The movement of stems to larger height classes was based on potential height growth modified by a competition index. Potential height growth was based on site index curves. The most sensitive reproduction competition index developed was a simple unt of overstory competitors weighted by relative tree heights and distance. Inclusion of measures of understory density did not improve growth predictions. Results further indicate that the height growth of a representative tree, with a height equal to the height-class midpoint, can adequately represent the growth of individuals in that class located elsewhere on the understory quadrat. The simplicity of the reproduction competition index and the evident need for only five understory height classes should also allow efficient growth simulation while retaining sensitivity to the overstory tree spatial pattern. FOREST SCI. 23:391-400.