Southwide Pine Seed Source Study—Loblolly Pine at 25 Years

Abstract A rangewide system of loblolly pine (Pinus taeda L.) seed source plantings has shown inherent variations in growth rate, fusiform rust resistance, and other less commercially important traits. Most of the variation is due to coastal-continental effects and to ecotypic differentiation of the loblolly population west of the Mississippi River. The western population is slower growing, more rust resistant, and more drought resistant than the eastern loblolly population, whereas coastal plain populations are faster growing, more susceptible to ice and cold, and less drought resistant than loblolly from areas with a more continental climate such as northern Georgia, Alabama, or Piedmont South Carolina. The differences in growth rate associated with these major physiographic and climatic effects are persisting as the test nears timber-rotation age, but the smaller growth-rate differences within physiographic regions are less stable.