Radial and Vertical Variation in Stem Properties of Juvenile Black Locust (Robinia Pseudoacacia)

Ten 10- to 12-year-old black locust (Robinia pseudoacacia L.) trees from two sites were analyzed to determine the within-tree variation (radially and vertically) and the between-site variation of selected wood properties. Specific gravity, fiber length, and extractive content exhibited significant radial variation for samples taken at breast height. Specific gravity increased radially from 0.57 near the pith to 0.68 near the cambium. Fiber length also increased radially from 0.75 mm (pith) to 1.06 mm (cambium). Radial variation was also exhibited by benzene-EtOH and total extractive content. Sap-wood tissue possessed the lowest benzene-EtOH content (2.70%) and total extractive content (6.81%), while the outer heartwood tissue maintained the highest extractive levels, 4.60% and 8.54%, respectively. Vertical stem analysis of samples obtained at intervals of 20% of the total-tree height showed a positive relationship with height, for ash content and hot-water extractive content, and a negative relationship with height for fiber length and benzene-EtOH extractive content. Stem tissue was composed of 84.7% wood and 15.3% bark. Mean heartwood content was 54.1%. Total stem-wood fiber length, specific gravity, and total extractive content averaged 1.05 mm, 0.68 and 7.32%, respectively. Nonextracted specific gravity was the only property differing significantly between sites averaging 0.69 and 0.66 for the two sites