Compressive properties of clear and knotty loblolly pine juvenile wood

Compression parallel to the grain tests were done on 3/4- by 1- by 4-inch clear specimens; 8-inch to 14-inch long clear and knotty 2 by 4’s; and untrimmed rounds from butt logs of 276 10-year-old trees of loblolly pine. The average values of the maximum crushing strength (MCS) of the inner and outer small specimens, clear 2 by 4’s, and rounds were 48 percent, 62 percent, 51.5 percent, and 62.5 percent, respectively, of the species mean MCS at the same moisture content. Knots reduced the MCS of the 2 by 4’s by about 22 percent, and of the rounds by about 9 percent. The average values of the modulus of elasticity (MOE) of the clear 2 by 4’s and rounds were 37 percent and 56 percent, respectively, of the species mean value. Correlation between specific gravity and MCS was fair for the clear rounds, good for the clear 2 by 4’s, and high for the small specimens. MCS and MOE were highly correlated for the clear 2 by 4’s but poorly correlated for the clear rounds. There were significant differences in the growth rate of the trees and the properties of the wood from the same families, but grown on two different locations.

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