Like people, trees like to head for nicer weather when temperatures get extreme.
Trees migrate slowly, of course. But University of Illinois researchers report that the movement of white spruces in Alaska and Canada is even more sluggish than previously believed -- a finding that could add to climate change woes.
"The fact they can't respond as fast as we thought has big implications for global warming," doctoral student Lynn Anderson says.
She's lead author of a paper on the subject posted online this week, ahead of publication in the Proceedings of the National Academy of Sciences.
Important source of wood
Anderson gathered DNA samples from 24 forests -- half in Alaska, half in Canada. "We drove 14,000 miles in three weeks, I and a friend." The friend was a fellow student collecting parsnip webworms for a completely different project.
Back in the lab, she painstakingly examined DNA sequences for five years to determine the origins of the spruces, which today are of great commercial importance as a source of pulpwood, lumber and other products.
The results found strong evidence of tree "refuges" in Alaska during the height of the last glacial period, lasting from 17,000 to 25,000 years ago.
Instead of being limited to areas south of the ice sheets and then migrating north with great rapidity when the climate warmed, as an old theory has it, spruces also hung tough in ice-free areas in the north.
Not so fast
For the previous but hotly debated theory to be true, the trees would have had to travel at the relatively breakneck pace of 1,500 to 2,000 meters a year -- about seven times the normal speed for trees.
That supposition was based on fossilized spruce pollen from sediment cores drilled in lake bottoms. Suspiciously, the cores contained no fossils of other tree material.
"The trees have to be there to drop needles and seeds," Anderson said. "Pollen goes a long distance in the air."Chicago Sun Times
