A Compatible System of Growth and Yield Equations for Slash Pine Fitted with Restricted Three-Stage Least Squares

Abstract

Abstract A system of compatible and interrelating equations (after Clutter 1963) was developed to predict growth and yield in volume, basal area, and dominant height for site-prepared slash pine plantations in the Southeast. Because of logical restrictions on certain parameters and contemporaneous correlations among the variables, the usual unrestricted least squares approach to fitting equations is not appropriate for such a system. The wealth of developments in econometrics for fitting such systems of interrelating equations was reviewed and tested, and restricted three-stage least squares gave the best results. Measures of goodness of fit and precision are nearly as good with restricted three-stage least squares for this system and data as with the conventional unrestricted least squares approach. Methods for placing confidence limits on predicted yields are demonstrated. Forest Sci. 32:185-201.