On the Rock Face

Biologist Gary Walker and his students make unexpected finds in hard-to-reach places
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Biology professor Gary Walker has spent more than 20 years investigating unique plants growing on and around cliff faces in the Appalachian region. He has found that these rare and restricted plant species hold interesting data on their natural history, as revealed by their genetics, as well as how they have adapted to the earth's changing climatic history.

"Cliff faces are habitats where glacial-relict plants don't have to compete with other species better adapted to the warmer, present conditions of today," said Walker, whose work has been published inNature and other scientific journals.

"They generally are also protected from natural wildfires and human contact. Many of these plants grow very slowly and can live a long time."

Walker first worked with cliff faces while pursuing his Ph.D.at theUniversity of Tennessee in the 1980s. He discovered that the northern white cedars he was studying were disjunct on cliff faces in the southern Appalachian region from their main range in a section of Canada stretching from Winnipeg to Nova Scotia.

He also found higher levels of genetic variation in the cedars in the southern Appalachians than he observed in the boreal forests of Canada, and that the cedars had clearly adapted to the warmer temperatures at their more southern locale after glaciers retreated north thousands of years ago.

"These high levels of genetic variation seem to have been accumulated and preserved over long periods of time through the use of alternative breeding systems, asexual and sexual, in these small, cliff-face populations," Walker said.

This unexpected discovery sparked a life-long interest in cliff-face ecology. Since coming to Appalachian State University's Department of Biology in 1988, Walker has passed on his interest in cliff-face plants to numerous graduate students, allowing them to merge their passions of rock climbing, conservation and biology.

Science meets sport

The first student interested in continuing Walker's cliff-face research was Peter Smith, who finished his master's degree at Appalachian in 1998 and now works for the National Land Trust. Smith, an avid rock climber, looked at the impact that climbing had on the vegetation found on rock faces in the Linville Gorge Wilderness Area. He discovered that the only vegetation that persists in climbed areas is crustose lichens, including a previously undescribed species, which was only recently named Fuscidia appalachiana.

Smith's research received national attention and was featured in Science, the weekly journal published by the American Association for the Advancement of Science. Shortly thereafter, Climbing magazine contacted Walker, less than pleased that conservation efforts based on the study might restrict climbers' access to affected cliff faces in popular climbing destinations throughout North America. Walker makes it clear, however, that he has nothing against the sport of rock climbing, and has even enjoyed time in a climbing harness himself. But, he does want climbers to be aware of their surroundings.

"It's an ethical dilemma for climbers," he said. "Most of them are environmentalists and are trying to balance that with their love of climbing. But there are ways to mitigate or even completely avoid most of the damage."

Discovering 900-year-old trees

Walker and his student Emily Parrisher conducted a similar climbing-impact study in Tennessee's Obed Wild and Scenic River National Park. Using information from this study and working with climbers in the area, the park's resource managers have since restricted climbing in some areas and put up warning signs in others to alert climbers to biological sensitivity.

During the course of their work in the Obed River gorge, they discovered ancient red cedars, some approaching 900 years of age, at the base of the cliff faces. Walker and Pete Soulé in the Department of Geography and Planning are now working under a National Park Servicegrant to study these rare trees. By examining the trees' rings, they can reconstruct the region's climate and fire history, and measure periods of environmental change.

National Park Service can use the data for interpreting the area's natural history and developing management and protection policies.

Walker acknowledges the serendipity he's experienced in studying cliff faces, both in his personal research and that of his students. "That's one of the neat things about science," he said. "We may be looking at one thing, and then we find something even more interesting along the way."