Radial variability of wood density and fibre length in the red oak trees (Quercus rubra L.)

Wood density and fibre length are two wood properties that are important in determining the quality of wood for commercial use. The fibre length of red oak has not been studied to the same extent as in other oak species. The aim of this paper is to explore the anatomical variation and wood density of red oak wood, as valuable information for researchers in other fields. Samples were taken in a 60-year-old red oak stand in the south part of Belgrade on the site of Stepin Lug. Along the south radius, the disc samples of 20 x 20 mm were cut from the sapwood, mature and juvenile wood. Ovendry density and fibre length were measured from the pith to the bark. According to the obtained data, the average oven-dry density of wood per radius is 0.694 g/cm3 . The lowest is in the juvenile wood and ranges from 0.628 to 0.681 g/cm3 , then in the part of sapwood - 0.662 g/cm3 , and the highest is in the mature wood where the density ranges from 0.707 to 0.740 g/cm3 . The presented values show certain differences, but also conform to literature data on the density of some industrial species from the genus Quercus L. The obtained results of the wood fibre length show that it varies from 0.99 to 1.33 mm which was measured in mature wood. The average length in a mature zone is 1.26 (1.16-1.33) mm, while in a juvenile area the average length is 1.02 (0.85-1.23) mm. Based on the known wood fibre length, it is possible to determine the density of red oak wood. In this research, a positive influence was determined in both parts of the tree, juvenile and mature, but a better mathematical dependence was obtained in the mature zone.