A Loblolly Pine Seedling-Grade by Genotype Study
Abstract A loblolly pine (Pinus taeda L.) seedling grade study was established in January 1987 on a Coastal Plain site at Bellville, Georgia. The factorial study involved three seedling grades (Wakeley's Grade 1, 2, and 3) and three half-sib families (#5, 25, 56). Trees were measured at ages 8 and 13 yr. Both family and seedling grade affected survival, height, and diameter at age 8 yr. Survival among families varied by as much as 3 percentage points while there was a 10 percentage point difference between Grade 1 and Grade 2 seedlings. Only family was related to height and diameter at age 13. Volume gains from planting Grade 1 seedlings instead of Grade 3 seedlings varied by family but there were no significant interactions between family and seedling grade. Differences in height among families and among seedling grades decreased over time. At age 8, there was a 5.3 ft difference between the tallest and shortest family but by age 13, the difference declined to 3.7 ft.Overall, planting family 56 instead of family 25 resulted in an additional 645 ft3/ac by age 13. Planting Grade 1 seedlings instead of Grade 3 seedlings produced an additional 303 ft3/ac. Per acre volume differences among families were greater at age 13 than at age 8. In contrast, differences among seedling grades were about the same at age 8 and 13 yr. The overall mean annual increment (MAI) for this study was 207 ft3/ac/yr. In comparison, the MAI for Grade 1 seedlings of family 56 was 239 ft3/ac/yr. South. J. Appl. For. 26(3):153–158.