Demonstration plots of Cupressus lusitanica
Mill., C. macrocarpa
Gordon, and Chamaecyparis nootkatensis
(D.Don) Spach x C. macrocarpa ("Leyland") in Rotorua, aged 21 years, were felled to compare lumber performance for appearance and structural uses. The trees had been planted at 1111 stems/ha, and later pruned in stages to height 5-8 m and thinned to 550 stems/ha.
Twenty trees of C. lusitanica, seven of C. mac rocarpa, and 12 of Leyland were cut into 3-m sawlogs and sawn to 150 × 50-mm and 100 × 50-mm sizes, slowly air-dried, then kiln-dried and dressed. Lumber was graded visually as appearance and structural grades. All boards were tested for long-span bending stiffness using the E-grader, and a sample were tested for characteristic bending stiffness and strength.
Each taxon had some advantages and disadvantages in growth, form, and sawn timber characteristics. Cupressus macrocarpa had grown to the same diameter at breast height (dbh) as C. lusitanica, and both had grown much faster than Leyland. Cupressus macrocarpa was the tallest but was badly affected by canker. Leyland had straighter stems than the others, and a higher frequency of branching.
Sawn-timber recovery was 50-60% for all log height classes of each species, except for the butt logs of C. macrocarpa where it was approx. 40% owing to fluting and high taper. Leyland yielded more of the best appearance grades, with 46% Dressing, 35 % Merchantable, and only 19% Box. Cupressus lusitanica averaged 26% Box, and C. macrocarpa 46%. Checks within knots were the worst defect for appearance grades in C. lusitanica, surface checks in C. macrocarpa, and pruned branch stub holes in Leyland. Long-span bending tests showed that C. lusitanica boards were much less stiff than those of the other species/hybrids. Bending stiffness of C. lusitanica was 4-6 GPa for both board sizes, and 6-8 GPa for C. macrocarpa and Leyland.
Stiffness increased from the inner boards to the outer in C. lusitanica (4.3-7.2 GPa). Characteristic bending strength was lowest for C. lusitanica (21.3 Wa) and values for C. macrocarpa (31.4 MPa) and Leyland (28.0 Mpa) were similar to global Pinus radiata D. Don values.