Wood and bark specific gravity of small-diameter, pine-site hardwood in the south

Abstract

Ten amall-diameter treee from each of the 22 species (~ treee) were 88IDpled from throughout the southern United States. Mean SO was determined for stem wood and bark and the whole stem, for branch wood and bark and whole branches (to a minimum diameter of O.M in.), and fortlee wood and bark and thewholetlee. Significantdift'erencee were determined a) among the speci. for each tree part measured and b) among the tree part8 of each SpeciM. The relationship between both stem-wood SO and stem-bark SO and height above ground is plotted by SpeclM. There was a significant inverse linear relationship between green MC and SO; with the exception of bark, the aahM contained lower ~t moisture than did speciM of similar SO. Comparison of stem-wood SO values with Wood Handbook valuM indicates that small-diameter pine-eite hardwoods are somewhat denser than larger trees of the same species more typically meuuled. that portion of each species range occurring ir the 11 southern states from Virginia to Arkan sas and eastern Texas. Sampling was restrictec: to trees between 5.5 and 6.5 inches in diameter outside bark, at breast height. Tree age vanec: from a species mean of27 years in yellow-popl8J to 59 years in black tupelo, with an overal average of 39 years. To sample the stem wood and bark ir proportion to occurrence by volume, 2-inch thick disks were removed at 48-inch interval. along the stemThe lowest disk was taken at2inches above ground, and the stem was con sidered to end at a point of branching abovt which a main stem could no longer be die tinguished. A 45-degree, pith-centered Wedg. measuring 1/2 inch along the grain W8J removed from each disk, and the wood and bar! separated at the cambium. SG values wer. determined from ovendry (OD) weight ani green volume, the latter determined by wate immersion after saturation. An average SG fo stem wood (or for stem bark) was obtained b: adding the weights and the volumes of th individual wedges of that stem to yield one 01 weight and one green volume. Whole-stem S< was found by combining all the bark and woo weights and the volumes from stem wedges. As REPORTED previoU8ly (1, 2, 3, 8), ~sonnel at the Southern Foreet Experiment Station have studied thoee properties of smalldiameter hardwoods deemed important to the forest products industry. The hardwoods studied produce a substantial fraction of the total volume of fiber on sites capable of growing southern pine. However, they generally have not been utilized because they lack a market and because of their small size and poor form. An evaluation of their properties should aid process engineers in devjsing utilization procedures for this hardwood resource. Specific gravity (SG) is an important property because it is an indicator of other properties and of fiber yield per unit volume. It is also relatively easy to measure. The objective of the study was to determine, for each of 22 species, mean SG values for the entire tree; i.e., wood plus bark, and for tree wood and bark separately; and for the entire stem, and for stem wood and bark separately; and for the entire branches, and for branch wood and bark separately. A second objective was to deterDline changes in SG along the length of the stem for each species. The 22 speci~ investigated (Table 1) comprise nearly 90 percent of the hardwood volume growing on sites which support, or are capable of supporting, pine stands. The author is Professor of Foreetl'y, Iowa Stat U niv., Am_, Iowa. This pa-Pel' was prep~ while h was with the So. FOI'Mt Expl Sta., USDA Fo~ S~ Pineville., La. Thia paper was received fo publication in July 1976. Procedure A total of220 trees, 10 of each species, were cut from widely separated locations throughout