U.S. scientists say they've found strong evidence an Alaskan tree refuge existed during the last glacial period, 17,000 to 25,000 years ago.
University of Illinois researchers said a genetic analysis of living spruce trees suggests that trees cannot migrate in response to climate change as quickly as some scientists have thought.
"One view is that trees were restricted to areas south of the continental ice sheets covering North America, and then migrated extremely rapidly as the climate grew warmer," said Feng Sheng Hu, an ecologist at Illinois and corresponding author of the paper. "The other view is that there was a refuge in the ice-free areas north of the ice sheets, and spruce trees expanded within those areas as the climate warmed.
"It now seems clear that a glacial refuge existed, and the trees advanced from at least two directions," he said, noting the data also suggest it is likely the migration rate was lower than previously thought.
The research appears in the early online edition of the Proceedings of the National Academy of Sciences in advance of publication.
Copyright 2006 by United Press International
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