A growth and yield model for thinned loblolly pine plantations was developed using data from 128 0.2-acre permanent plots in the Virginia Piedmont and Coastal Plain. The Weibull function, used to characterize stand diameter distributions, was searched to insure that the resulting total basal area and average dbh estimates were identical to those predicted from stand variables using regression equations. Program WTHIN was written in standard FORTRAN to provide stand and stock tables for thinned old-field loblolly pine plantations.

Trials with different thinning intensities indicated reasonable trends, as compared with published studies.