Stand-level height-diameter equations for young ponderosa pine plantations in Neuquen, Patagonia, Argentina:: Evaluating applications of equations developed in the western United States

Two linear and two nonlinear height-diameter models commonly used in the western United States were tested for the young ponderosa pine (Pinus ponderosa) plantations of northern Patagonia, where it is the most widely planted species. The equations were fitted to each of 127 plots, located throughout the geographic range of the plantations in Neuquen province. The four equations were compared using Furnival's (1961) index of fit. Even though there were no important differences among models tested, the nonlinear model previously applied by Wykoff et al. (1982), H = 1.3 + exp(beta(0) + (beta(1)/(D + 2.54))) + epsilon was preferable because it converged more efficiently than the other nonlinear equation and was more flexible than the linear functions. Differences in the behavior of plot-level and regionwide equations demonstrated the biases possible if regionwide equations are applied to estimate missing heights within a plot. The coefficients for the two nonlinear models fitted to trees growing in several regions in the western United States generally overestimated the height of Neuquen trees.