GEORGETOWN-- To look at the natural forests today, you would never know that Hurricane Hugo roared through South Carolina just 10 years ago, said Charles A. Gresham, a Clemson University forest ecologist.
Hugo's 1989 trek through the state damaged some 4.5 million acres of timberland in 23 South Carolina counties. After the hurricane, Gresham and other ecologists identified research sites in four South Carolina forests to track the recovery process over time. These sites have been set aside as permanent research areas through a grant from the Andrew W. Mellon Foundation. They will remain undisturbed by any future developments and are being used to document what happens to forests in the aftermath of major hurricane damage.
Gresham is based at the Clemson's Belle W. Baruch Institute of Coastal Ecology and Forest Science in Georgetown, a public service research and education center that focuses on forests, wildlife and the environment. Every three years since 1993, he and other scientists have visited the research sites to measure the plant life and woody debris left behind, then inventory the types of trees in the study plots.
The study sites are located in the Hobcaw Forest at the Baruch Institute, the Francis Marion National Forest near McClellanville, the Bidler Forest near Holly Hill and the Congaree Forest near Columbia.
"Nature abhors a vacuum," Gresham said. "Within 10 years, we have seen significant recovery-- back to a fully functional, productive forest with a lot of habitat for wildlife. The trees that had their tops broken off by Hugo have re-formed crowns so the canopy has returned. We've also seen a ten-fold increase in the number of new trees filling in open spaces."
Called "advance regeneration," these new trees are coming from seeds dropped into open spaces left when older trees were felled by the hurricane's reported 100-plus mile-per-hour winds and by the rapid growth of seedlings released by the creation of open spaces. A major change Gresham and other scientists have noted is that the new growth is by the "pioneer" species of pine, sweet gum and black gum instead of the "climax" species of oak or tupelo. But the mix of species is expected to change over time as the saplings compete for light and nutrients and slower growing species outlast the faster growing ones.
"I've had to open my mind and think in a different time frame," Gresham said. "We're all accustomed to turning on a computer and 'whoom' you've got what you need right then.
"But forest processes work on a longer time scale. Ten years is a very short time frame in a tree's life. A loblolly pine has a life span of 130 years and there are live oaks down here that are a couple of hundred years old. If we stick around for another 100 years, we might see a very similar forest to what was here before Hugo."
Another observation that has emerged from the study is that disturbance, whether from a hurricane or from a single tree dying, is a natural part of forest dynamics. "It's not rare or unnatural, it's just a normal part of nature's process and the forest's development," Gresham said.
The only remaining evidence of Hugo today is the debris of fallen trees and logs that now provide habitat for wildlife and support the growth of other plants by releasing nutrients into the soil.
Three species of trees weathered the hurricane with less damage than others, Gresham said. Not surprisingly, they are the trees most closely identified with the Lowcountry's coastal plain: live oak, cypress and long leaf pine. These are the species that are most likely to survive when hurricanes hit.
The live oak is low and squat, with wood as hard as steel, so it keeps its head down and lets others take the brunt of the winds, Gresham said. The cypress has a deciduous needle, so Hugo's first gusts of wind in September blew off the needles and then had less resistance to cause further damage. The long leaf pine is generally not as tall as the loblolly pine so was less likely to be damaged by the wind, although taller longleaf pines proved to be just as susceptible as other tall trees.
An inventory at the research sites will be conducted again in 2000 and 2003. "I can't wait to read the next chapter and see how the species composition is changing and how the species are growing," Gresham said.
This research is funded through the South Carolina Agriculture and Forestry Research System based at Clemson, and is being conducted in cooperation with the National Audubon Society, the U.S. Forest Service, National Park Service and the University of Georgia.