Two years ago, a Fourth of July windstorm swept through the Boundary Waters Canoe Area Wilderness with the force of a hurricane. Straight-line winds toppled tree trunks like dominoes, flattening more than a third of the million-acre wilderness.
To many, the storm seemed like a catastrophe, but it's provided a rare opportunity for scientists to study how a wilderness recovers from a massive natural disturbance.
A small grove of white cedar, with trees 500-1,000 years old was not damaged by the blowdown at Three Mile Island in Seagull Lake. See other images from BWCAW.
ALAN HANEY KNOWS THE BOUNDARY WATERS CANOE AREA WILDERNESS WELL. A forestry professor at the University of Wisconsin at Stevens Point, Haney has studied the effects of disturbances such as fire and logging on the forest for the past 25 years. He has 100 study plots, each 20 acres, scattered across the Boundary Waters wilderness and surrounding woods. So when the storm cut a swath through his study area, he was perfectly positioned for a "before and after" study.
His results so far show a wilderness much more resilient than scientists suspected. "Overall, the system seems to be adjusting remarkably quickly," Haney says, "more so than we would have anticipated given the severity of the storm."
Among the tangle of downed trunks, small trees and shrubs are flourishing. Woodpecker populations are thriving. Some species of songbirds, including magnolia warblers, mourning warblers, winter wrens, and white-throated sparrows are increasing. Haney has also found evidence that new birds are moving into the blowdown area. "One of the biggest surprises that we found was the yellow bellied flycatcher, a relatively lesser known species," he says. His crews hadn't recorded the birds on any of the study plots prior to the storm, but afterward, they found them on every plot where the storm had hit.
Like all the species native to the Boundary Waters, the flycatchers have lived for millions of years in a north-woods ecosystem that evolved with massive disturbance. The area was frequently swept by wildfire until the fire suppression policies of the past century. Windstorms, although much smaller than the July 1991 storm, are also fairly common. So Haney and other scientists expected the plant and animal life of the forest would be well adapted to withstand the effects of the storm.
A 200-year-old red pine forest was flattened by the July 4, 1999 wind storm at Three Mile Island in Seagull Lake, at the end of the Gunflint Trail.
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(Photo: Dave Hansen, University of Minnesota Agricultural Experiment Station.
Even so, the details have still surprised him. Crews crawling through fallen tree trunks have noticed ladyslippers and other kinds of orchids blooming undisturbed on the forest floor. "On one of the sites where 15 years ago we had recorded the very beautiful calypso orchid in bloom, we found it in bloom again this year under the debris," says Haney. "We hadn't seen it on that site in 15 years."
Inside the wilderness boundaries, the forest has been left to recover on its own.
But outside the wilderness, some storm-damaged plots have been logged to salvage downed timber and reduce the danger of fire. Haney's surveys have found bird numbers and diversity on these logged plots are much less than on unsalvaged plots, with six to 10 nesting birds per logged plot, compared to as many as 60 on the unlogged sites.
University of Minnesota forest ecologist Lee Frelich has also been studying the effects of the storm. He's been surprised to find that two tree species, paper birch and white cedar, withstood the winds much better than others, such as jack pine, aspen, spruce and fir. Frelich has found clumps of ancient cedars, 500 to 1,000 years old, that the wind didn't harm at all. In part that's because the slow-growing cedars are so short.
The cedars reach a maximum height of only about 20 feet, and many are only four to five feet tall; mature red and white pines in the area can be 90-100 feet tall. Frelich says the dwarf cedars resemble large bonsai. "They have very thick trunks for their size. They have a lot of dead branches. They have little tufts of live foliage here and there, " he explains. "Some of them look like the bristlecone pines out in California; they just have one strip of live bark and maybe one live branch on the tree, so there wasn't much for the wind to push on."
When the storm first struck, some scientists worried that the toppled forest would be a feast for insects that might spread to nearby, standing trees, but so far that doesn't seemed to have happened, according to Bill Mattson, an entomologist with the U.S. Forest Service in Rhinelander, Wisconsin. He says the wilderness's response has "highlighted the beauty of natural systems" that have "been there through thick and thin."
One question scientists had hoped to study was how well large animals such as moose and wolves can navigate the blowdown areas. But so far there's been no funding for such a study, so scientists can only guess at the answer.
The U of M's Frelich says he's noticed that moose seem able to make their way through , and he suspects the horizontal logs act as a highway for smaller mammals. He and his students were standing in the forest last summer when they noticed a fisher, a dark-furred member of the weasel family, regarding them from a log. The animal turned and quickly disappeared, making its way effortlessly through the tangle.