According to the patterns of radial distribution of fiber lengthand the relationships between DBH and b-value, we consider thatxylem maturation in A. mangium, A. auricuriformis and P. falcataria(Java and Solomon origins) depends on diameter growth. Formationof mature wood starts after a certain diameter is reached in these species, suggesting that we should accelerate lateral growthfrom the early growing stage in order to produce mature wood as early as possible. On the other hand, we consider xylem maturationis controlled by cambium age in E. globulus and E. grandis. In those species, formation of mature wood starts once a certain cambiumage is attained. This suggests that lateral growth should be arrestedat an early growing stage, and lateral growth subsequentlyaccelerated after a certain cambium age is reached, in order to reduce the percentage of juvenile wood in the harvested trunk.