Spot-Size of Herbaceous Control Impacts Loblolly Pine Seedling Survival and Growth

Abstract

Abstract Two studies were installed at diverse locations to evaluate the seedling-centered area of herbaceous vegetation control needed to optimize seedling survival and growth. Study site I, established in 1986, was located on an upland Piedmont site in northeast Georgia. Study site II, established in 1985, was located on an alluvial site in southeastern Oklahoma. Treatments applied on both sites were: a no vegetation control check, and competition control in seedling-centered spots 2, 4, 6, and 8 ft in diameter. After 3 years in the field at the Georgia site, trees in the 6 and 8 ft diameter spot treatments averaged 13% to 15% better survival, 49% to 64% larger diameters at breast height (dbh), and 19% to 24% greater height than trees in the check treatments. On the Oklahoma site, after 3 years in the field, survival in treatments receiving vegetation control ranged from 41% to 56% greater survival than in the check treatment. Height in the 4, 6, and 8 ft diameter spot treatments averaged 32% to 47% taller, and dbh was 238 to 425% larger than those in the check. Most of the gain in survival was obtained with only a 2 ft diameter spot size at the Oklahoma location. At the Georgia installation, a 6 to 8 ft diameter spot size treatment was required to obtain a significant increase in survival. Diameter and height responses at both locations increased in proportion to the area treated with herbicide. South. J. Appl. For. 15(4):193-199.