Compatible Basal Area Growth and Yield Models Consistent With Forest Growth Theory
Compatible growth and yield models often include constraints which prevent them from fitting the sample data as well as empirically derived equations. However, the superiority of such constrained equations can be demonstrated by examining their fit to the complementary stand characteristic. For example, if parameter estimation has been performed using growth as the dependent variable, the compatible yield equations should be evaluated as part of the process of choosing the best model. Thus chances are reduced of either selecting a model that has been strongly influenced by unusual aberrations in the sample data or selecting a model based on inappropriate constraints. To illustrate, one empirical and two constrained basal area growth models, have been fitted to a common data set obtained from red pine (Pinus resinosa Ait.) plantations that were subject to a variety of thinning regimes. One constrained model in which an inverse relationship between growth and current basal area was specified, gave the poorest fit to the growth data used for parameter estimation, however, the compatible yield form estimated future yields the best of all three models. This anomalous result provides some justification for using the new model for growth and yield estimation. Forest Sci. 29:279-288.
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