Variation of density and growth ring width in stems of Sitka and Norway spruce

The variation with height and radial distance from the pith of basic density and ring width has been determined in stems of 48-year-old Sitka and Norway spruce planted at two spacings at Durris, Kincardineshire. The pattern of radial variation of density was broadly similar at all heights: high near the pith, falling to a minimum and then a gradual increase. The mean whole-stem densities were significantly different at the two spacings in Sitka but not in Norway spruce. Density at breast height was inversely correlated with ring width, strongly in Sitka but weakly in Norway spruce. The density/ ring width regression equation for outer wood in Sitka spruce at age 48 differed from that at age 31. In Norway spruce a high correlation was found between whole-stem density and the density of rings 16–25 at breast height.