Characterization of yields for Pinus taeda genotypes at the half-sib, full-sib, and varietal levels of genetic improvement at two planting densities at age 5 in the upper coastal plain of Georgia
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Seedling deployment options for the establishment of operational Pinus taeda plantations in the Southeastern U.S. now include half-sib families, full-sib crosses, and varietals. In 2005, a study to evaluate the effects of genotype and density on yield and quality was established on a moderately well-drained upland site in the Upper Coastal Plain in Marion County, GA. Establishment culture intensity was operational and included chemical and mechanical site preparation and herbaceous weed control. The genotypes used in the trial included four varietal entries (C32 and C93 referred to as “high yielding” below, and C36 and C40 referred to a “low-yielding”), three full-sib genotypes (M2, M15, M16), and one well-known and widely-planted half-sib family (OP3). The density treatment included a 388 tree per acre planting level and a 518 tree per acre planting level. The trial design is a split-block, randomized complete block. Tree measurements were completed at the end of the 5th growing season. Genotype and density treatment mean differences were evaluated for statistical significance for traits including survival, DBH (diameter at 4.5 ft), height, and mean tree volume, at the alpha level of 0.01. These means and their relative significance are summarized in Table 1.