Influence of Variation in Physical and Chemical Properties of Southern Red Oak Lumber on Decay Resistance

Abstract

Although differences in decay resistance of the heartwood of various oak species have long been recognized, the effect of changes in physical and chemical wood properties on this decay resistance have not been well defined. Scheffer et al (5) studied the decay resistance of seven native oaks. They found that, within the species of the red oak group studied, there were no practical differences in resistance. However, they did find differences in decay resistance between individual trees of the same size in the same locality, and attribute this variability to genetic differences. Within a tree they found that asa rule resistance decreased from the outer heartwood toward the pith and from the butt to the top. They made no direct study of the effect of physical or chemical properties of oak wood on decay resistance, but found that resistance decreased as ring width decreased in the outer heartwood of white oak. A number of investigators have studied decay resistance in relation to physical and chemical properties of the wood of other tree species. Extractives have been shown to be closely related to decay resistance (4, 8). Scheffer and Hopp (6), in their study of decay resistance of black locust heartwood, demonstrated the toxicity of hot-water extractives and concluded that the concentration of extractives accounted for a substantial part of the variability in decay resistance within anyone tree, but that other factors must be considered in accounting for differences between trees. In laboratory tests, assuming that air and moisture conditions are not limiting, it might be expected that within a tree species the higher the specific gravity the greater the decay resistance until such time as availability of food becomes a limiting factor. Southam and Ehrlich (7) in their discussion of specific gravity and decay resistance believe that this theory accounts for the contradictory conclusions arrived at by other workers (2, 3,9).

Citation

Toole, E. Richard; Darwin, W. N. 1970. Influence of Variation in Physical and Chemical Properties of Southern Red Oak Lumber on Decay Resistance. Research Report MSUFPUL-RR-10. Stoneville, MS: USDA-Forest Service, Mississippi State University Forest Products Utilization Laboratory: 12 p.