Climatic warming and its effect on bud burst and risk of frost damage to white spruce in Canada

Temperature data from ten weather stations across Canada were used to model the effects of climate warming on the timing of bud burst and the risk of frost damage to white spruce (Picea glauca (Moench) Voss). There was evidence of increasingly earlier dates of bud break over the course of this century at half of the stations examined (Amos and Brome, Quebec; Cochrane, Ontario; Fort Vermilion, Alberta; and Woodstock, New Brunswick), with the period 1981 to 1988 having the earliest predicted dates of bud burst (earliest degree day accumulation). Risk of frost damage at most stations in the 1980s was usually greater than in earlier periods. Weather data modelled for climate warming of 5 degrees C predicts that bud burst will occur two to four weeks sooner than was the case during 1961 to 1980 at all stations, but that this will generally be accompanied by decreased risk of frost after bud burst. However, while the expected trend is one of reduced frost risk in the future, as the climate gradually warms frost risk is expected to fluctuate upward or downward depending on interactions between provenance and local climate.