Compression properties of small clear southern yellow pine specimens tested across five decades

Southern yellow pine (SYP) is one of the most used softwood species in the world. Most of this raw material come from fast-grown plantation trees. It is of interest to determine if SYP clear wood properties may have changed over the long term, in particular whether such properties may have declined. Herein, specific gravity (SG), ultimate compression strength parallel to grain (UCS||), and UCS perpendicular to grain (UCS?) from three samples were compared: Sample 1 tested in 2014; Sample 2 from molding and millwork producers tested in 2017-2019; and Sample 3 from a study conducted in the mid-1960s. With respect to specific gravity (SG), the wood in Sample 1 was significantly lower than that from Samples 2 and 3. With respect to UCS||, all three samples were statistically different. Adjusting to 12 percent moisture content had no influence on the mean separation of UCS||. With respect to UCS?, no statistically significant differences were detected among the test data from any of the three samples. However, for the UCS data generated from the SG and moisture content-related model, Sample 2 was higher than Sample 3, and Sample 3 was higher than Sample 1, and these differences were statistically significant. Overall, these findings do not suggest that broad or consistent changes or declines of these wood strength properties have occurred during the past five decades.