• Chang, C.I.
  Faculty of Forestry, University of Toronto, Toronto, Ont.
  
• Kennedy, R.W.
  Faculty of Forestry, University of Toronto, Toronto, Ont.
  

Two hundred thirty-two white spruce trees were sampled from 29 plots in 6 localities in southern Ontario. Specific gravities of discs cut at four-foot intervals were determined for each tree. The amount of dry wood substance contained in each tree was obtained by multiplying weighted, whole tree specific gravity by tree volume. Although specific gravity was negatively correlated with growth rate, this reduction in dry weight per unit volume was minor in relation to the increased volumes associated with rapid growth rates.

The equation using the regression of the logarithm of dry wood production on tree age was determined. Trees having dry wood production of more than 1.5 times the standard error of estimate indicated by the regression lines were selected as superior trees. The characteristics of these superior trees together with the environments in which they grew were examined. The absence of any relationship with environmental factors suggested, a genetic cause of above-average wood production. Superiority of a tree was mainly due to fast radial growth rate. The prospect of designing a tree breeding program to improve rate of dry wood production is discussed.