Short-Term Projection Accuracy of Five Asymptotic Height-Age Curves for Loblolly Pine

Height-age data from the Southwide Pine Seed Source Study of loblolly pine plantations were used to evaluate short-term projection accuracy of five nonlinear asymptotic height-age curves: Cilliers-Van Wyk, Chapman-Richards, first-degree logistic, Gompertz, and Lundqvist. Upper asymptotes were selected for each plot by two alternative methods: fixed at a reasonable value, and estimated from the data through age 20. Accuracy was assessed by comparing observed top heights at age 25 with predicted top heights at this age. For short-term projections of height-age curves, the Cilliers-Van Wyk, Chapman-Richards, and Lundqvist models show promise, especially when the upper asymptote is fixed. Forest Sci. 31:414-418.