Wood structure and production within the trunk and branches of Piceasitchensis in relation to canopy formation

Abstract

The seasonal progress of wood production and variation in tracheid dimensions were followed systematically along the trunk and main branches of Piceasitchensis trees and analysed in relation to the distribution of light intensity and leaf weight as the canopy develops. The aim was to provide data towards building models to predict effects of management on within-tree patterns of wood production and structure. Tracheid production began earliest at the tips of branches towards the base of the crown; the data show that tracheid production in the main stem began earliest several internodes below the leader, its onset progressing faster and having a shorter distance to travel down the upper branches. Tracheid production appeared to cease simultaneously throughout the trunk in codominant trees; it ceased earlier in severely suppressed trees, which consequently produced little or no latewood.In the main stem, maximum ring width occurred at least one internode above that carrying maximum total leaf dry weight. Maximum rate of tracheid production occurred one or two internodes above those having maximum current leaf dry weight, several internodes above the maximum total leaf weight. In branches, rate of wood production was closely correlated with light intensity.The seasonal increase in wall thickness from early- to latewood occurred more rapidly as you progress down the main stem to below the crown in 16-year-old trees; hence, Mork latewood began progressively earlier lower down the stem; this pattern was not developed in the trunk of younger trees. In all branches, latewood began earlier at the base than at the tip, owing to a more rapid seasonal increase in wall thickness towards the branch base. Tracheid diameter increased from the leader down to midcrown. In branches, partial correlations suggest that tracheid diameter varied with light intensity at the tip but inversely with whorl number at the branch base.