"We found that, beyond a minimum required level of chilling, many different combinations of temperatures resulted in spring budburst," Harrington said. "Plants exposed to fewer hours of optimal chilling temperatures needed more hours of warmth to burst bud, whereas those exposed to many hours of chilling required fewer hours of warm temperatures for bud burst."
The plants were responding, the researchers found, to both warm and cold temperatures they experienced during the winter and spring. And, they noted that the same temperatures can have different effects depending on how often they occura fact that may seem counterintuitive at first. While some winter warming may hasten spring budburst, substantial periods of mid-winter warming, such as is projected under several future climate scenarios, may actually delay, not promote, normal budburst.
Harrington and her colleagues used their findings and research results from other species to develop a novel model that depicts this gradual tradeoff between chilling and forcing temperatures and have verified its accuracy using historical records. They found that the model was fairly accurate in predicting past budburst in Douglas-fir plantations, which indicates it works well with real-world conditions.
Because the model is based on biological relationships between plants and temperature, the researchers expect it will be fairly straightforward to modify for use with other species and for other areas. Managers, for example, could use the model to predict changes in budburst for a wide range of climatic projections and then evaluate the information to determine if selecting a different species to plant or stock from a different seed zone would be a useful management strategy.
|Contact: Yasmeen Sands|
USDA Forest Service, Pacific Northwest Research Station