| dc.description.abstract | Radial and axial variation of tracheid length, relative density, ring width, radial
and tangential shrinkage, and juvenile and mature wood volume were studied in a single
stem of jack pine, 37 km north of Thunder Bay. The tree was 60-year-old and was from
a naturally grown stand in the Jack Haggerty Forest of Lakehead University, Thunder
Bay, Ontario. Specimens were taken from the tree stem at heights of 0.15, 1.4, 3.4, 5.4,
7.4, 9.4, 11.4, 13.4, 15.4 m along west and east aspect. Juvenile and mature wood
boundary was demarcated by using the radial variation pattern of tracheid length as the
criterion.Tracheid length increased from pith outward in the juvenile wood, reaching a
maximum, then remained constant or leveled off towards the bark in the mature wood.
The rate of increase in tracheid length with ring age increased with increasing height
with an exception at 13.4 m. The mean tracheid length in the juvenile and mature wood
increased from the base upward, reaching a maximum at 3.4 m and 5.4 m for the
juvenile and mature wood, respectively, followed by a decrease further to the top.
Relative density decreased from the pith outward with ring age in the juvenile wood and
remained less variable in the mature wood, with an exception at 0.15 m. Relative density
decreased with increasing height with an exception at 13.4 m in both juvenile and
mature wood. Ring width increased with ring age from the pith outward in the juvenile
wood and fluctuated in the mature wood. Ring width decreased with increasing height in
the juvenile wood. No axial trend for ring width variation in the mature wood was found.
Tangential shrinkage was greater than radial shrinkage. The mean tracheid length of the
west aspect was significantly different from that o f the east aspect. Relative density of
both juvenile and mature wood in the east aspect was significantly higher than that in the
west aspect. Ring width in the west aspect was significantly wider than that in the east
aspect for mature wood. For both tracheid length and ring width, there was no difference
between west and east aspects in the juvenile wood. Radial, tangential shrinkage (overall
and the two outermost wood strips) increased from pith outward to the bark, reaching a
maximum then followed by a leveling off. Radial, tangential shrinkage (overall and the
two outermost wood strips) decreased with increasing height with an exception at 0.15
m. The percentage of juvenile wood accounted for 16% and 30%, respectively, of the
entire stem volume based on ring age and stem diameter as criteria. The juvenile wood
zone was conical in shape. There was a strong negative correlation between juvenile
wood width and cambial initial age. The values for percentage of juvenile wood volume
at breast height can be used to predict the entire stem value. | |
