Variation of wood and bark density and production in coppiced Eucalyptus globulus trees in a second rotation

Abstract

Coppiced Eucalyptus globulus trees with 18 years of age and in a second rotation were analysed in relation to wood and bark density in a spacing trial with five initial plant densities. A total of 25 stumps, with a variable number of stems per stump, from one to three, were analysed. A comparison was made to the previous first rotation single stem trees, also harvested at 18 years of age. The average wood basic density at breast height of the eucalypt coppiced trees was 567 kg m-3, with lower wood density for the closest spacings. The wood of coppiced Eucalyptus globulus trees was 2.5% less dense than that of the single stem trees in the first rotation (average 582 kg m-3). Within the tree, the wood density decreased from stump level to breast height level and then gradually increased until 11.3 m and then decreased slightly. The bark density was, on average, 473 kg m-3, ranging from 455 to 487 kg m-3. The mean bark density was comparable to the bark density in the first rotation. The average bark content was 17.4% of the stem volume, providing 25 to 52 ton ha-1. Compared to the first rotation, the average tree volume in the coppice was lower because the individual trees were smaller by 40 to 66%, while the estimated volume production per ha of the coppice was 1.1 to 1.8 times more due to the increased number of trees that were left in each stump.