Planting nonlocal seed sources of loblolly pine - Managing benefits and risks

Seed source testing of loblolly pine (Pinus taeda), which began in the 1920s, has allowed large realized genetic gains from using nonlocal seed sources in operational plantations. Seed source testing continues, and deployment guidelines are still being refined. Some general effects of seed source movement can be described, but there are still gaps in (1) understanding exactly how far certain seed sources can be moved, (2) the degree of risk involved, and (3) how certain traits such as wood quality vary by seed source, especially with seed source movement. In some cases, seed source movement gains can be achieved with little risk; for example, planting Livingston Parish, Louisiana material for rust resistance in more easterly Gulf Coastal areas. Also, movement of seed sources one plant hardiness zone north can result in increased growth with little concern for winter damage. Big gains in growth, however, from using nonlocal seed sources may come at significant risk. Two industrial examples of planting nonlocal seed sources and how risks were managed are covered: (l) South-to-north movement: MeadWestvaco's use of loblolly pine north of the native range in Kentucky and surrounding areas, and (2) East-to-west movement: Weyerhaeuser's use of North Carolina coastal plain families in southern Arkansas and southeast Oklahoma. To deal with the significant risks of seed source movements, one must be aware of the risk factors, understand historical climatic data (are the risks high or low within a typical harvest rotation period), and have silvicultural and genetic strategies to mitigate or reduce risk. Possible genetic strategies include thorough testing and allocation of orchard families of the nonlocal seed source, development of a land race (breeding and testing for local adaptation of the nonlocal seed source), interprovenance hybrids, and interspecific hybrids. Examples of these are discussed in this article.