Impact of initial spacing on yield per acre and wood quality of unthinned loblolly pine at age 21

The market for southern pine first thinnings is soft. Thus, forest managers are planting at wider spacings, and using weed control and fertilization to grow chipping-saw and sawtimber trees in shorter rotations. A 21-year-old unthinned spacing study was sampled to determine the effect of initial spacing on wood quality and yield per acre of planted loblolly pine (Pinus taeda L.). The study area was planted in the Coastal Plain of GA in 1984 with loblolly pine family 7-56 seedlings. Twenty-one trees from each of seven spacings ranging from 6 by 8 feet (908 trees per acre) to 12 by 12 feet (302 trees per acre) were sampled. Total stem green weight per acre of wood and bark to a 3-inch d.o.b top was estimated to be highest in the 6 by 12, 8 by 10 and 8 by 12 foot spacings. Estimated volume of lumber per acre was slightly higher in the 8 by 12 spacing compared to the 12 by 12-feet spacing. Breakeven stumpage price per acre was highest for the trees planted at 8 by 12-feet spacing. Average number of knots, knot diameter, and average maximum knot diameter increased with increased spacing.