Maturation property of fast-growing hardwood plantation species: A view of fiber length

Abstract

The development of human civilization has caused many problems, among them increases in atmospheric CO 2 and shortage of fossil fuel resources. Fast-growing tree species can help solve these problems. Short rotations cause concern that fast-growing species contain a high proportion of juvenile wood, thus limiting their use. To use fast-growing species for timber, this concern must be addressed. We consider whether xylem maturation depends on cambium age or diameter growth in the tree, and when and where this maturation occurs. To evaluate these options for typical fast-growing species, Acacia mangium, A. auricuriformis, Eucalyptus globulus, E. grandis, Paraserianthes falcataria (Java origin), and P. falcataria (Solomon origin), we have developed a new parameter, the “ b-value”, on the basis of radial distribution of fiber length. From our evaluation using “ b-value”, we reached the following conclusions. For Acacia spp. and Paraserianthes spp., xylem maturation depends on diameter growth. Formation of mature wood in these species starts after a certain diameter is reached, suggesting that accelerating lateral growth from an early growing stage will produce mature wood as soon as possible. In Eucalyptus spp., xylem maturation is controlled by cambium age. In those species, formation of mature wood starts once a certain cambium age is attained. This suggests that it is important to arrest lateral growth at an early growth stage, and then accelerate lateral growth after a certain cambium age is reached. Depending on the tree species concerned, those results will be helpful in the development of plantation management programs.