A hurricane-wrecked forest may not look pretty, but it works. After partially uprooting trees in a pattern that mimicked severe storm damage, researchers found that more than three-quarters continued to put out a full canopy of leaves the following spring. The area looked trashed, but the flow of nutrients and water through the forest was unperturbed.
Traditionally, foresters have viewed the devastation of a hurricane or tornado as a mess of mangled lumber to be cleaned up, rather than as a natural part of a forest's life. The biggest timber salvage operation in U.S. history was launched in the northeast U.S. after "The Great Hurricane of 1938," says plant ecologist David Foster, director of the Harvard Forest, a 3000-acre tract in Petersham, Massachusetts. After the cleanup at Harvard Forest, researchers noticed that stream flow in the forest increased dramatically and that the white pines downed by the storm were eventually succeeded by deciduous hardwoods.
Wondering if this kind of succession is par for the course, Foster's team decided not to wait for the next killer storm to find out: Instead, they whipped up their own storm. In October 1990, the scientists used a cable and winch to exert force equal to hurricane gales, yanking down trees on a 2-acre plot of mixed hardwood forest. By the time the wrecking crew was finished, about 600 of 900 trees on the plot had either been pulled down or damaged by another tree's fall. Many of the largest trees, red oak and birch, were partially uprooted, while smaller, more supple trees, primarily hickory and red maples, just bent. The faux hurricane, they report in the December issue of Ecology, did little to affect the flow of stream water and nutrients through the forest. "This is a functioning ecosystem," says Foster. "It just happens to be all busted up and lying on its side." This study, he says, suggests that salvage logging can interfere with a forest's ability to sustain itself in the wake of a storm.
Creating your own hurricane, of sorts, is "a neat idea," says Charles Canham, a forest ecologist at the Institute for Ecosystem Studies in Millbrook, New York. The experiment complements past studies that were conducted right after storms, he says. "One of the problems with studying hurricanes is that you're rarely prepared for them."