The opening of buds on Douglas-fir trees each spring is the result of a complex interplay between cold and warm temperatures during the winter, scientists with the U.S. Forest Service's Pacific Northwest Research Station have found.
Their researchwhich is featured in the December issue of Science Findings, a monthly publication of the stationled to the development of a novel model to help managers predict budburst under different scenarios of future climate.
"We take it for granted that buds will open each spring, but, in spite of a lot of research on winter dormancy in plants, we don't really understand how the plants are sensing and remembering temperatures," said Connie Harrington, research forester and the study's lead. "The timing of budburst is crucial because, if it occurs prematurely, the new growth may be killed by subsequent frosts, and if it occurs too late, growth will be reduced by summer drought."
Although scientists have long recognized that some plants require a certain amount of exposure to cold temperatures in the winter and warm temperatures in the spring to initiate the opening of buds, the precise interaction between these chilling and forcing requirements has, until now, been largely unexplored. Harrington and her station colleagues Peter Gould and Brad St Clair addressed this knowledge gap, which has implications for forecasting the effects of climate change on plants, by conducting greenhouse experiments in Washington and Oregon using Douglas-fir, an ecologically and economically important species.
For their experiments, the researchers exposed Douglas-fir seedlings from 59 areas in western Oregon, western Washington, and northern California to a range of winter conditions. After the seedlings finished their first year of growth, they were divided into groups and placed in different locations where their exposure to temperatures varied according to predetermined scenarios. In the spring, the scien
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USDA Forest Service, Pacific Northwest Research Station