Influence of Precommercial Thinning and Fertilization on Total Stem Volume and Lower Stem Form of Loblolly Pine

Two cultural treatr7zents were applied in an overstocked loblolly pirze (Pinus taeda L.) plantation (2,900 trees/ha after eight growing seasorzs): precom~nercial tlzinning (Yes or No) to 747 tt-ees/lza after the eighth growing season and broadcast fertilizatiorz (Yes or No) with diamrrzonium phosphate (150 kg/ha of P and 135 kg/ha of N) early in the ninth growing season. Total height and diameter at breast height (dbh) measurenzents were taken periodically through the 14th growing season. Fertilization increased tree volume more than thinning in the 9th through 10th growing seasons, but thinning was most eflective by the 13th growing season. Over the 6-year period, thinning was the most eflective cultural practice: check, I10 dm2; fertilized only, 135 dm'; thinned only, 165 dm'; and thinned and fertilized, 220 dm-'/loblolly pine tree. After the 14th growing season, the fir-st 5 m of bole was divided into five sections beginning at a 15-cm stump height: 15-30, 30-60, 60-125, 125-250, nrzd 250-500 cm, and the volume for each section was calculated. Outside-bark volume per section increased consistently with thinning and fertilization; therefore, cultural practices did not change stern form in the lower bole. South. J. Appl. For. 29(4):215-220.