LONGITUDINAL VARIATION OF RING WIDTH, WOOD DENSITY AND BASAL AREA INCREMENT IN 26-YEAR-OLD LOBLOLLY PINE (PINUS TAEDA) TREES

Longitudinal variations in select wood quality parameters were examined in 26-year-old loblolly pine trees planted in Anhui Province, China. Wood density and ring width were measured from cross-sections of different heights of merchantable stems. The average ring width decreased from the base to 1.3 m, then increased to the maximum at 7.6 m, and thereafter reduced with stem height. The longitudinal patterns varied with cambial age in ring width. The coefficient of variation in ring widths along the stem height was greater than 21% at the cambial age 5-8 years and 9-12 years, and small variations were observed in other cambial age groups. The average wood density declined from 1.3 m to 7.6 m and then slightly increased with increasing stem height. The wood density showed great variation at different growth stages below 7.6 m, but varied less above 7.6 m. Basal area increment (BAT) gradually increased with increasing ring number (from the pith to the bark) at different stem heights, and markedly reduced after the 22nd ring. These results indicate that the longitudinal variations of wood density, ring width and BAI in loblolly pine are greatly affected by cambial age. The detailed information of the wood properties along stem heights could be useful to wood utilization of loblolly pine.