Quality of sawn timber produced from young Paulownia trees planted in Tochigi, Japan

This study aimed to clarify the quality of full-size sawn timber produced from young Paulownia trees. Although the number of sampled trees is limited, sawn timber (n = 93; 38 × 89 × 1820 mm) was produced from 25 trees (4 years old; mean stem diameter at 1.3 m above the ground = 17.5 cm; mean tree height = 9.5 m) of Paulownia species growing in a plantation located in Mashiko, Tochigi, Japan. The timber was visually graded and subjected to a static bending test. Linear mixed-effect models with random effects of individual trees, visual grading class, or the existence of pith cavities were developed. The mean value of all sawn timber was 3.45 GPa in modulus of elasticity (MOE) at 15% moisture content, and 13.7 MPa in modulus of rupture (MOR) at 15% moisture content. The visual grading classes did not affect the bending properties of sawn timber. The existence of a pith cavity in a timber reduced the MOR. In conclusion, improving the sawing process to eliminate the pith cavity from the sawn timber is necessary to obtain sawn timber with higher strength properties.