The Sudden Sawlog Study was established in 1954 near Crossett, AR, in a 9-year-old loblolly pine plantation to test the hypothesis that loblolly plantations can produce sawtimber in 30 years. To stimulate diameter and height growth and clear wood production, study plots were heavily thinned, trees pruned to 33 feet by age 24 years, under-story mowed, and growth of intensively managed trees compared with control trees. The study was officially closed at age 33 when it was reported that, with intensive management on good sites, loblolly pine can produce sawtimber-size trees in 30 years. The intensively managed and unpruned control trees were harvested in 2001 and the butt two logs of each tree sawn into lumber. At harvest, average diameter at breast height was 22.4 inches on plots receiving intensive treatments compared with 16.1 inches for controls. A portion of the intensively managed and control trees were sawn at a dimension sawmill and a portion sawn at a shop sawmill. Starting at age 9, trees were pruned every 3 years to one-half total height; by age 15 they were pruned to 20 feet and thinned to 100 trees per acre or less. These practices significantly increased the yield of high-grade lumber from butt logs sawn at the dimension and shop sawmills. Pruning every 3 years to one-half total height to 33 feet by age 24 and continued thinning resulted in a large-diameter knotty core in the second log that significantly reduced lumber grade. To reduce the diameter of this knotty core, when loblolly pine is thinned to < 100 trees per acre by age 15, crop trees should be aggressively pruned to 34 feet, either by frequent pruning or pruning to a shorter live crown of 33 to 40 percent with a minimum stem diameter of 2 inches at base of crown. To maximize lumber value, pruned logs should be sawn into shop lumber.
Clark, Alexander, III; Strub, Mike; Anderson, Larry R.; Lloyd, H. Gwynne; Daniels, Richard F.; Scarborough, James H. 2004. Impact of Early Pruning and Thinning on Lumber Grade Yield From Loblolly Pine. Gen. Tech. Rep. SRS–71. Asheville, NC: U.S. Department of Agriculture, Forest Service, Southern Research Station. pp. 199-204