Radial distribution of thujaplicins and thujic acid in old growth and second growth western redcedar (Thuja plicata donn)

Radial cross sections of seven old growth cedars and ten second growth cedars taken at breast height were cut into increments averaging about 60 years growth for old growth trees and 10 years growth for second growth trees. These increments were extracted with ethanol:benzene (1:2). The extractives were analyzed for thujaplicin content by colorimetry of their ferric chelates, as well as by a new method utilizing capillary gas chromatography (GC) of their methylated derivatives. A statistical analysis of the two methods gave an r² value of 0.81 and a slope of 0.99. Thujic acid contents were also determined by the new GC method. Distribution of thujaplicins and thujic acid generally increased from pith to outside heartwood, then decreased in the sapwood. Maximum thujaplicin contents were also related to the tree age.Forestry, Faculty ofGraduat