Effects of Age and Sampling Position on Wood Property Variations in Nigerian Grown <em>Gmelina Arborea</em>

Abstract

Wood properties of plantation grown (Gmelina arborea Roxb.) were evaluated in this study. Eighteen trees from 3 age classes namely: 18, 28 and 36 years were sampled at the butt, 50% merchantable length ML and 90% ML, and were radially partitioned into inner wood, middle wood and outer wood, on the basis of distance from pith. Result obtained was analyzed using ANOVA at 5%level. Mean SG were 0.33 for age 18, 0.41 for 28 and 0.46 for the 36 year old Gmelina. While SG varied inconsistently in 18 year old Gmelina, it decreased significantly from butt to 90% ML in 28 and 36 year old trees. MOR ,MOE and MCS// decreased generally from base to top for all age classes except in 28 year old, where variation in MOE was inconsistent. All properties studied increased from inner wood to outer wood. Axial uniformity in strength properties ranged between 0.50 and 0.64, 0.65 and 0.73, and from 0.49 to 0.82 in MOR, MOE and MCS respectively. Radial uniformity index also ranged between 0.69 and 0.78 in MOR, 0.78 and 0.85 in MOE and between 0.76 and 0.80 in MCS. For all the properties studied, wood uniformity was best in 36 year Gmelina along the radial plane, while 18 year Gmelina had the best uniformity index along the axial plane. Effect of age was highly significant on strength properties and its variation patterns. In particular, there was about 44.8% increase in strength properties from 18 to 28 years and 19.1% increase from 28 to36 years. Woods of Gmelina arborea varied significantly along and across the bole, and should be treated as such in their conversion and utilization strategies.