Modeling diameter class removals for thinned loblolly pine (Pinus taeda) plantations

Loblolly pine plantations are often thinned at mid-rotation to improve the stand quality looking toward a future final harvest that will maximize sawtimber production. Models are needed for estimating removals by dbh class under such assumptions for various stand characteristics and residual thinning targets. The aim of this study was to develop equations for estimating the proportion of basal area or trees removed by dbh class at time of thinning when removals by selection can potentially occur within all dbh classes. Regression models were developed using data from operationally thinned plots across the southern United States. Proportion of trees removed by dbh class was found to be correlated with stand stocking prior to thinning (quadratic mean dbh), intensity of the thinning and whether the thinning is a first or second thin. Tests of the models with data from independent plots thinned under the same assumptions showed good agreement across most dbh classes. The models developed in this study are independent of any diameter distribution assumptions and can be used to predict stand tables for basal area and number of trees removed and remaining at time of thinning when the purpose of the thinning is to emphasize sawtimber production at final harvest.