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 . 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.

Effect of stand density on longitudinal variation of wood and bark growth in fast-growing Eucalyptus plantations

“…Miranda et al (2016) studied 11-year-old E. globulus trees grown in Portugal with an average bark content of 15.2%, varying from 9.6 to 23%. Miranda & Pereira (2015) have investigated E. globulus trees at 18 years of age and found a mean bark content of 17.4% of the total stem volume for second rotation trees and 13.8% for first rotation trees at the same age. Silva et al (2018) assessed the variation in bark content and thickness of 4.5 year-old Eucalyptus and Acacia planted in pure and mixed stands.…”

“…Most studies that investigated the bark content of trees were based on the total bark content expressed as percentage of the total stem (Ramírez et al 2009, Miranda & Pereira 2015, Miranda et al 2016. Quilho & Pereira (2001) in 15-year-old Eucalyptus globulus trees reported a mean bark content of 11% of stem dry weight, with higher values in the lower part of the stem (14% at 5% height level), decreasing to the 35% of height level (9%) and increasing again (but less) towards the top (12% at 75% height level).…”

“…We found no evidence in the literature on the longitudinal variation of bark thickness and bark content of Eucalyptus trees planted at different stand densities. Regarding the variation in bark characteristics with stand density, the longitudinal variation in bark density in trees at five different spacing was investigated by Miranda & Pereira (2015). They reported that bark density was highest at the stump level (488 kg m -3 ), decreased along the stem up to 3.3 m (462 kg m -3 ) and then remained rather constant at an average of 465 kg m -3 .…”

“…Despite being physiologically important, the presence of bark is currently undesirable for most industrial applications. Trees produce large amounts of bark during their growth; in Eucalyptus globulus, the bark content varies from 15.2% for trees with 7 to 11 years of age (Ramírez et al 2009, Miranda et al 2016) to 17.4% for 18-year-old trees (Miranda & Pereira 2015).…”

“…Quilho & Pereira (2001) have evaluated within and between-tree variation of bark content in Eucalyptus globulus in Portugal and stated that bark thickness was higher in the site with better growth and always decreased from the tree base to the top. Miranda & Pereira (2015) have investigated variation in wood and bark characteristics in Eucalyptus globulus trees grown with different planting densities in Portugal and reported that bark content varied from 13.4 to 14.4% of the stem volume. In Brazil, Rocha et al (2016) assessed the influence of plant spacing on wood and bark density in 7-year-old Eucalyptus hybrids grown in northern Minas Gerais, Brazil and concluded that trees at wider spacings (9 m 2 ) produce bark with greater density than at narrowed spacings (1.5 m 2 ).…”