Chemosystematic Studies in the Genus Pseudotsuga. III: Population Differences in British Columbia as Determined by Volatile Leaf Oil Analysis

Abstract

Detailed analysis of the volatile leaf oil terpenes of different Douglas-fir populations and provenances growing in British Columbia confirmed the previous classification into the following terpene types: three coastal (A, B, and C), coastal intermediate, intermediate, interior intermediate, and Rocky Mountain. In areas of overlap of the coastal and Rocky Mountain varieties a continuous gradation of terpene types may be encountered. Differences in elevation or soil sites within homogeneous populations do not affect the terpene patterns noticeably. The major area of overlap occurs in the Cascade Mountains of southern British Columbia. Further inland either interior intermediate or Rocky Mountain types are found. However, at wet sites there is a noticeable increase of the typical coastal terpenes. Conversely, at drier sites in the southern coastal regions, including southeastern Vancouver Island, a distinct increase of the typical Rocky Mountain variety terpenes was recorded. Somewhat unexpectedly, this was also found at Cowichan-Skutz, which is a typical wet coastal site. Equally unexpected was the finding of many trees with the coastal C terpene pattern in three locations near D'Arcy; no noticeable increase in the typical Rocky Mountain variety terpenes was recorded at D'Arcy.A simplified gas chromatographic technique was developed which reduces the cost of analysis by a factor of ten, yet allows differentiation between the seven terpene types.