FLEXURAL PROPERTIES OF LUMBER FROM 2 40-YEAR-OLD LOBLOLLY-PINE PLANTATIONS WITH DIFFERENT STAND DENSITIES

The effects of stand density on the flexural properties and compliance -to-grade requirements of lumber from two 40-year-old loblolly pine pl antations were evaluated. The results indicate that stand density is p ositively influencing the flexural stiffness and grade compliance of t he lumber produced from these plantations. On the other hand, stand de nsity had no effect on the flexural strength of the lumber from these plantations. The lumber from the denser 40-year-old stand, which had 2 8 m/50 yr site index, 2.4-by 2.4-m original spacing, never thinned, wi th 679 trees/ha and 11.4-sq m basal area at harvest, has 96% and 66% c ompliance to required flexural strength and stiffness values, respecti vely. The lumber from the thinned 40-year-old stand, with 28 m/50 yr s ite index, 2.4-by 2.4-m original spacing, thinned at age 25, with 450 trees/ha and 10.2-sq m basal area at harvest, has 96% and 53% complian ce to required flexural strength and stiffness values, respectively. I t is now evident from the results of these studies that even dense sta nds must be older than 40 years of age before they can be harvested fo r lumber production to ensure attainment of at least 95% lumber grade compliance, i.e., strength and stiffness values that are consistent wi th assigned Visual grades.