Accuracy of eastern white pine site index models developed in the Southern Appalachian Mountains
Three older, anamorphic eastern white pine (Pinus sfrobus L.) site index models developed in the southern Appalachian Mountains between 1932 and 1962 were evaluated for accuracy and compared with a newer, polymorphic model developed in 1971. Accuracies of the older models were tested with data used in development of the 1971 model, in which actual site index had been determined by stem analysis. The 1971 model could not be evaluated for accuracy because independent data were unavailable. Evaluation statistics included prediction accuracy, bias, variance, mean square error, and tolerance interval. For one of the older models, prediction accuracy within 5 percent of observed site index was 100 percent, and other statistics compared favorably. Based on the premise that a polymorphic model best describes growth of eastern white pine over a range of site qualities, the site index model developed in 1932 performed surprisingly well.