Tree-ring analysis of yellow-cedar (Chamaecyparis nootkatensis) on Vancouver Island, British Columbia

Yellow-cedar (Chamaecyparis nootkatensis (D. Don) Spach) are the oldest known coniferous trees in Canada. This paper reports on the first dendrochronological investigation of yellow-cedar trees at montane sites on Vancouver Island. Mature yellow-cedar trees were selected for study at four sites along a 200-km northwestsoutheast transect. Trees older than 500 years were common at three of the four sites, with numerous individuals older than 750 years identified. Carefully prepared cores proved well suited for ring-width measurement, with 220 cores from 156 trees included in our final four chronologies. The best replicated segment of the four chronologies (1800-1994 A.D.) show common intervals of reduced radial growth in the 1800s, 1840s, 1860s, 1920s, 1950s, and 1970s. While the relative strength of the between-site signals varies over this interval (r = 0.424-0.908), it is apparent that the chronologies share a common radial growth signal. Our efforts to identify the role climate played in this relationship were successful and the results appear to have a dendroecological basis within the annual yellow-cedar growth cycle. Six different temperature and precipitation variables explain 61% of the annual ring width variance. Our results suggest that further dendrochronological and dendroclimatological studies using this long-lived species are warranted.