- Manwiller, Floyd G.
Southern Forest Experiment Station, Forest Service, U.S. Department of Agriculture
Weighted stem averages were determined for wood and bark of 72 trees representing the commercial range of Pinus glabra Walt. The trees were stratified into three age classes (15,30, and 45 years) and two growth rates (averaging 4.9 and 9.0 rings per inch). Within-stem variation was determined from 1,296 earlywood and latewood sampling points in the 72 stems. Tracheid length increased with tree age and averaged 0.2 mm. longer in fast-growth trees than in slow-grown. Tracheid diameter did not differ with age, but radial and tangential diameters averaged 2 to 4 um. larger in fast-grown latewood tracheids averaged 0.27 um thicker than those from slow-grown stems. Tracheids near the pith were short, of small diameter, and had thin walls with large fibril angles; those near the bark were longest and had greatest diameters, thickest walls, and smallest fibril angles. Extracted specific gravity did not differ with age class or growth rate in earlywood or latewood. However, wood specific gravity averaged lower in fast-grown trees (0.408 unextracted) than in slow-grown (0.442) because fast-grown trees contained a greater proportion of large-diameter, thin walled earlywood tracheids. Bark specific gravity averaged 0.391 in slow-motion trees and 0.371 in fast-grown. Bark thickness increased with tree age. Wood chemical components did not vary with age class or growth rate, and mechanical properties did not differ greatly. Microtensile strenght and longitudinal shrinkage of earlywood and latewood did not vary with position in stem. Green volumes and ovendry weights are tabulated for bark and wood components.