Impacts of Vegetation Control, Genetic Improvement and their Interaction on Loblolly Pine Growth in the Southern United States—Age 12 Results

A designed study was established in the Coastal Plain of Georgia and northern Florida, and in the Piedmont of South Carolina, Georgia, and Alabama with the objectives of evaluating the impacts of first-generation genetic improvement and of combining genetic improvement and vegetation control on yields of loblolly pine. The two levels of competition control were either none, other than that provided by the operational mechanical site preparation, or complete competition control. Genetic treatments consisted of unimproved seed stock, bulk lot first-generation improved stock or single family first-generation improved stock. In terms of total volume, increases up to 45% (882 ft3/ac) and 39% (863 ft3/ac) were obtained from using complete vegetation control in the Coastal Plain and Piedmont regions, respectively. Improved genetic stock increased total volume an average of 11% (246 ft3/ac) to 16% (364 ft3/ac) in the Coastal Plain and 12% (277 ft3/ac) to 19% (445 ft3/ac) in the Piedmont for bulk lot and single families, respectively. For total volume, the effects of competition control and genetics were additive, indicating the managers should obtain the full benefit of these two treatments. In both regions, improved genetics significantly reduced the percent fusiform infection. In addition, no statistically significant differences were detected between bulk lot and single family plantings across all dependent variables. South. J. Appl. For. 26(1):37–42.