Clemson scientists, collaborators working to restore longleaf pine forests
CLEMSON, South Carolina — Billions of magnificent trees that were nearly annihilated a century ago are making a slow, yet promising, comeback thanks in part to a team of Clemson University researchers and their collaborators.
Colossal stands of longleaf pines once dominated vast swaths of the United States from southeastern Virginia to Florida and west through Louisiana to Texas. But in the 18th and 19th centuries, more than 90 million acres of longleaf forest were obliterated to build ships and railroads. By 1920, the towering trees had been nearly wiped out. And equally distressing, the understory of these forests, which harbor one of the most diverse and fascinating ecosystems in the world, disappeared along with the trees.
“At one time, it was estimated that longleaf pine forests covered as many as 93 million acres. Right now, we’re down to about 3 million acres, and very little of that is old-growth longleaf pine,” said T.J. Savereno, a senior associate agent for Clemson Cooperative Extension. “But there have been efforts across the range of longleaf — involving state and federal agencies, private landowners and nonprofits — to bring back the longleaf pine and its associated ecosystem.”
Since 2011, Savereno has worked in conjunction with Joan Walker of the U.S. Forest Service to spearhead an ongoing project called “The South Carolina Longleaf Pine Ground-Layer Common Garden Study,” which has focused on a variety of native plants commonly found in the understories of longleaf pine forests. Three different common-garden plots at Clemson University’s Sandhill, Pee Dee and Coastal research and education centers have become home to legumes, grasses and asters collected in the wild from 23 locations in North Carolina, South Carolina and Georgia. One of the main focal points of the study is to determine how well plant species from relatively wide-ranging geographical regions thrive in a common location.
“Even within their own species, plants are genetically adapted to their environment. They have special abilities to thrive where they grow, and if you move them too far out of their comfort zone, they may not grow as well,” said Walker, a research ecologist for the U.S. Forest Service who is based at Clemson University. “The understory of a longleaf system is like a prairie, and a lot of its species are widespread and have the same name in Minnesota or Texas as they do in South Carolina. We knew there were variations within these species, but we didn’t know how variable they were and in what ways they varied. So we’ve gathered seeds from many places, put them in the same garden, and then watched to see how they perform, side by side.”
In recent years, the restoration of longleaf pine forests and understories has become a major conservation issue. The U.S. Department of Agriculture, U.S. Department of the Interior, U.S. Department of Defense, The Nature Conservancy, National Wildlife Federation, U.S. Fish and Wildlife Service, The Longleaf Alliance, S.C. Forestry Commission and a variety of other entities have joined the cause. Longleaf pines, which grow up to 100 feet tall and can live for more than 300 years, are aptly named. Their needlelike leaves reach 18 inches in length and are prized by landscapers and homeowners. The deep-rooted trees produce excellent lumber, can withstand windstorms, pests and fire, and are beneficial to soil and water quality.
But what lies beneath their canopy might be of even greater value than the trees themselves. The understory is home to more than 30 endangered and threatened animals, such as red-cockaded woodpeckers, indigo snakes and gopher tortoises. Turkey, quail, songbirds and many different species of beneficial insects also thrive in this environment. None of this would be possible without the native plants that make up the understory of a well-managed longleaf pine forest.
“There are three main plant groups associated with longleaf ground cover that we’re focused on,” said Savereno, who is based in Lee County. “One is the group of legumes, which improve soil fertility and produce seeds that are high in protein and consumed by many species of wildlife. Second are native grasses, such as wire grass and the bluestems, which offer shelter and also provide fuel for fire. Third are the asters, which are blooming plants that attract native pollinators and that also produce seeds eaten by songbirds and small mammals.”
The longleaf ecosystem is dependent on fire to maintain its viability. Nature takes care of some of this via lightning strikes, which have always been frequent through the Southeast. Properly executed prescribed fires are also effective. Fire kills small trees and other woody plants that otherwise would grow to full height and compete with the longleaf pines, thereby creating a canopy too dense to allow a sufficient amount of sunlight to reach the ground and nourish the herbaceous vegetation.
“Prescribed fire was employed by the American Indians as a land management tool for thousands of years, and many European settlers followed their lead,” Savereno said. “However, beginning in the early 1900s, there were campaigns to portray prescribed fire as a backward, destructive practice and to discourage landowners from burning. And when Smokey Bear appeared in the 1940s, his message was ‘Only You Can Prevent Forest Fires.’ But if you’ve noticed, the slogan has been changed in recent years to ‘Only You Can Prevent Wildfires,’ because there is now a recognition that fire plays a crucial role in maintaining a healthy ecosystem. However, prescribed fire managers need to be well-trained. It can be done safely if it’s done properly.”
In addition to physical observation of the plants in the three common gardens, genetic testing is under way to determine how many genetically distinct groups are contained within the collections. Genetics might underlie how well plants perform in the gardens. Walker has enlisted the expertise of Clemson University scientist Saara DeWalt, as well as the university’s Genomics and Computational Biology Lab. The multifaceted team is employing a technique called genotyping-by-sequencing to look at the genetic structure of the herbaceous species that will be used to restore longleaf pine savannah across the Southeast. It has started by unravelling genetic variation in goat’s rue.
“Goat’s rue is one of the most photogenic and beautiful plants that we have in the garden. And we found that of our 13 or 14 populations, there are three really distinct genetic groups,” said Walker, who is also an adjunct professor at Clemson. “One of them corresponds to the Sandhills, which is east and west from Columbia. This group was different than the plants from the Francis Marion National Forest. And those two groups were different from plants down around Savannah and southeast Georgia. We’ve found that these differences are related to geography. So there might be really good reasons to not move plants from places that are as close as Savannah is to the Sandhills. This is a pretty big discovery.”
In the future, the team plans to conduct genetic testing on every species in the gardens. When all have been analyzed and genetic data matched with performance in the common gardens, the researchers will then be able to make recommendations about where to collect seeds to restore longleaf pine savannahs in particular parts of the Southeast,.
“We may have to use seed of some species from the same savannah that is being restored,” said DeWalt, an associate professor in the biological sciences department. “For others, we may be able to use seed sources that are collected from farther away.”
Savereno and Walker are passionate about longleaf pine ecosystems and have studied them for years. Their goal is to assist in the range-wide effort to restore or improve millions of acres of longleaf pine forests across the Southeast. It’s a work in progress, but one that is gaining momentum every day.
“There are ecological, cultural and recreational reasons to restore longleaf pine forests to at least a remnant of their former glory,” Savereno said. “A healthy longleaf pine ecosystem is a haven for so many important plants and animals. That’s why I’m working so hard to try to undo some of the damage of the past.”
There’s one final benefit. Longleaf pine forests are stunning illustrations of nature at its finest.
“The garden experiment had humble beginnings. We didn’t start out with a lot of funding, but we had plenty of heart,” Walker said. “I love these trees. I love these herbaceous plants. They’re beautiful. And if I can help it, they will be here for generations to come.”