Formation and vertical distribution of juvenile and mature wood in a single stem of Cryptomeriajaponica

A single tree stem was used to study the formation and vertical distribution of juvenile and mature wood in Cryptomeriajaponica D. Don. The sample tree was collected from a 45-year-old plantation with 1.5 × 3.0 m spacing at Maio-li, Taiwan. Nine diametric wood strips were cut from the tree trunk from both the east and the west aspects, starting from 0.3 m by increments of 2.5 m to the top of the tree. The widths of juvenile and mature wood were recorded with two measures, i.e., the number of rings and the width in millimetres. The relationships between both the width of juvenile and mature wood and the height and age at each level of the tree were obtained by regression methods. The relationships between the age of the cambial initial and the period of juvenile wood formation at the various height levels were also determined. It was found that juvenile wood has a conical shape with a wide base at the bottom of the tree. There is no significant difference in the ratio of juvenile to mature wood width between the east and west aspects of the tree. The impact of both the height and age at each level of the tree on the width of juvenile wood appears to differ, and a similar observation must be made for mature wood. A high proportion of the total wood volume (64%) was found to be juvenile wood. No mature wood was observed at the top of the tree. The width of juvenile wood is highly correlated with the age of formation of cambial initials counted from the year of seed germination. The older the cambial initial, the narrower is the width of juvenile wood in terms of ring count.