Warming reshapes state's boreal forest

Posted: Monday, September 11, 2006

FAIRBANKS - Glenn Juday stands next to a white spruce that sprouted from seed two years after Britain ceased hostilities against the colonies in the Revolutionary War, the last time fire swept through the Bonanza Creek Experimental Forest.

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The 221-year-old trees are the monarchs of the northern boreal forest, rising 110 feet, and they have no business surviving on 11 inches of annual rainfall.

"That's just ridiculously low," said Juday, a forest ecologist.

What makes the forest possible are cool temperatures. At least they used to be.

A favorable combination of snow melt and rainfall that gives trees moisture just when they need it most has been disrupted by warming in recent decades - more frost-free days, more 70-degree days, less heat loss at night, a potentially lethal combination to trees of the northern boreal forest. While climate warming has been most obvious in Alaska's glaciers and pack ice, it's also threatening to reshape the ecosystem that covers most of the state.

Warming may be behind a proliferation of insects that have attacked trees in unprecedented numbers. It's a suspect in forest fires that burned a record 6.6 million acres in 2004. And drought brought on by warming threatens the hardwoods that stand next to the dominant species, the white and black spruce.

Juday said that if warming continues to accelerate, insects, fire and drought will change Alaska's forest within decades.

"It's not wild talk to claim that, well, maybe it will get too dry for the trees to grow here," Juday said. "It can and does happen."

James Kruse, a U.S. Forest Service entymologist in the Alaska Regional Forest Health Program in Fairbanks, said Alaska has been an environment of extremes, going back to the Ice Age.

"When things happen up here, it tends to happen big," he said.

He said he may be "a little more optimistic" than Juday. But he acknowledges that tree species may disappear or even be replaced by grasses, if models follow most dire trends. But he does not pretend to guess how bad it's going to get, he said.

"It's much less of an intact forest than it used to be and it's got the decline processes under way that are going to do it in," Juday said. "A few of the trees will survive, and they'll become really old trees, but it's been hit pretty hard."

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