Budding Time Linkages

It does not sound as if there isanything safely linear about all this. As this makes clear, the variables havenot sorted themselves out and the apparent linkages may be open to question. Otherwiseit may be possible to assemble an empirical model to support best practice onan acre by acre basis. 

In mountain country, this couldwell be valuable.  Elevation climatechanges are huge and intensely local.  Onereally would like to be able to make adjustments to counter the effect.

I am not sure if it mattersotherwise.  Budding time is not that importantand may vary by a week or so anyway.

Winter temperatures play complex role in triggering spring budburst

Study yields new model that can help managers calculate when plantswill burst bud under different climate scenarios

PORTLAND, Ore. January 11, 2010. The opening of budson Douglas-fir trees each spring is the result of a complex interplay betweencold and warm temperatures during the winter, scientists with the U.S. Forest Service’s Pacific Northwest Research Station have found.  

Their research—which is featured in the December issue of ScienceFindings, a monthly publication of the station—led to the development of anovel model to help managers predict budburst under different scenarios offuture climate.  

“We take it for granted that buds will open each spring, but, in spiteof a lot of research on winter dormancy in plants, we don’t really understandhow the plants are sensing and remembering temperatures,” said ConnieHarrington, research forester and the study’s lead. “The timing of budburst iscrucial because, if it occurs prematurely, the new growth may be killed bysubsequent frosts, and if it occurs too late, growth will be reduced by summerdrought.”

Although scientists have long recognized that some plants require acertain amount of exposure to cold temperatures in the winter and warmtemperatures in the spring to initiate the opening of buds, the preciseinteraction between these chilling and forcing requirements has, until now,been largely unexplored. Harrington and her station colleagues Peter Gould andBrad St Clair addressed this knowledge gap, which has implications forforecasting the effects of climate change on plants, by conductinggreenhouse experiments in Washington andOregon usingDouglas-fir, an ecologically and economically important species.

For their experiments, the researchers exposed Douglas-fir seedlingsfrom 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 intogroups and placed in different locations where their exposure to temperaturesvaried according to predetermined scenarios. In the spring, the scientistsmonitored the seedlings and documented the length of time it took for theirbuds to open.  

“We found that, beyond a minimum required level of chilling, manydifferent combinations of temperatures resulted in spring budburst,” Harringtonsaid. “Plants exposed to fewer hours of optimal chilling temperatures neededmore hours of warmth to burst bud, whereas those exposed to many hours ofchilling required fewer hours of warm temperatures for bud burst.”

The plants were responding, the researchers found, to both warm andcold temperatures they experienced during the winter and spring. And, theynoted that the same temperatures can have different effects depending on howoften they occur—a fact that may seem counterintuitive at first. While somewinter warming may hasten spring budburst, substantial periods of mid-winterwarming, such as is projected under several future climate scenarios, mayactually delay, not promote, normal budburst.

Harrington and her colleagues used their findings and research resultsfrom other species to develop a novel model that depicts this gradual tradeoffbetween chilling and forcing temperatures and have verified its accuracy usinghistorical records. They found that the model was fairly accurate in predictingpast budburst in Douglas-fir plantations, which indicates it works well withreal-world conditions.

Because the model is based on biological relationships between plantsand temperature, the researchers expect it will be fairly straightforward tomodify 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 climaticprojections and then evaluate the information to determine if selecting adifferent species to plant or stock from a different seed zone would be auseful management strategy.

To read the December issue of Science Findings online, visit

 http://www.treesearch.fs.fed.us/pubs/36960.