The effects of previous drying on shrinkage and moisture content of some southern bottomland hardwoods

Three logs for each of nine southern hardwood species were obtained, and specimens were separated into heartwood and sapwood. Specimens were dried from the initial green condition to oven-dry and then resaturated and dried again to oven-dry. A simple linear regression analysis was performed to determine the relationship between volumetric shrinkage and moisture content of never-dried and previously-dried specimens. The average fiber saturation point was 33.3 (33.6 for sapwood and 32.9 for heartwood) for never-dried specimens and 29.4 (28.2 for sapwood and 30.6 for heartwood) for previously-dried specimens. An average of 86% of the variability in volumetric shrinkage of never-dried specimens can be attributed to moisture content, and 90.5% of the variability in volumetric shrinkage of previously-died specimens can be attributed to moisture content. Highly significant differences for the species factor were found to exist at an equilibrium moisture content of 90% relative humidity (RH) and 75% RH for both never-dried and previously-died specimens. Volumetric shrink-age differed significantly for species and wood-types at 90%, 75%, and 0% RH for previously-died wood and 75% and 0% RH for never-died wood. A t-test revealed significant differences between volumetric shrinkage of never-dried and that of previously-dried wood for both wood-types of two species and one wood-type of three others.