USDA Town Hall Meeting in Athens, Georgia

by Viniece Jennings, SRS Integrating Human and Natural Systems unit

Cassandra Johnson Gaither (left), U.S. Forest Service Southern Research Station Project Leader, and Gregory Parham (right), USDA Assistant Secretary for Administration.

On April 15, the Office of the Secretary of Agriculture organized a local town hall meeting in Athens, Georgia, to discuss key issues facing the USDA and to improve employee engagement. The meeting included agencies in Athens and other stakeholders across the state.

The meeting took place at the Russell Research Center in Athens. The key speaker was Dr. Gregory Parham, USDA Assistant Secretary for Administration. He outlined key points in the USDA’s Strategic Plan such as improving employee engagement and developing a 21st century workforce. Representatives spoke on behalf of seven USDA agencies.

Dr. Cassandra Johnson Gaither, project leader for the U.S. Forest Service Southern Research Station (SRS) Integrating Human and Natural Systems unit, provided an overview of Forest Service activities within SRS. Her remarks were well received and she was invited to participate in a special session where Dr. Parham met with leaders who work on the ground. “It was a great opportunity to meet other members of the USDA family located in Athens; it was refreshing to see a representative from the Secretary’s Office translate the vision in the strategic plan to local employees,” shares Johnson Gaither.

For more information, email Viniece Jennings at

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The Calhoun

Long-term research on restoring soil on wasted lands

The Calhoun in the 1940s, after almost a century of soil degradation. Photo by U.S. Forest Service.

Until the middle of the 20th century, forest researchers were mostly concerned with what could be done above the ground—growing trees, protecting them from insects and diseases, maximizing productivity, and regenerating stands after harvesting. It was not until 1947, when the Calhoun Experimental Forest (Calhoun) was established on the Sumter National Forest in the Piedmont of South Carolina, that soil studies began in earnest.

The 2,078-acre site for the Calhoun was chosen because it represented the poorest Piedmont conditions, the “worst of the worst.” The hope was that studies at the Calhoun could inform efforts to reforest ruined lands across the Piedmont and the South.

Under Louis Metz, the first director of the experimental forest, and with later guidance from Carol Wells, the Calhoun staff began a program of work aimed at soil improvement. According to Metz, their goal was “to find the cheapest, quickest, most effective ways of speeding tree growth, increasing plant nutrients, and improving soil structure so that the land stores water for plant use.”

To that end, they installed the Calhoun Long-Term Soil Ecosystem Experiment, regarded by many as one of the finest long-term ecological studies in the world. Started in 1957 by Metz and expanded by Wells in the 1960s, the versatility of the study has allowed scientists to address a series of important issues. At first, the experiment consisted of planting pine seedlings at different densities to determine how best to grow pine forests on soil exhausted by farming, with the aim of providing the information needed to improve soil and watersheds across the South. Later, as the stands grew, they provided long-term data that informed new studies of tree and stand dynamics, biomass, and ecosystem productivity.

The soil sample archives kept since the first experiments on the Calhoun make it one of the few sites in the world where chemical changes in soil over decades can be directly observed. In the 1980s, data from the Calhoun provided direct evidence of acid rain effects on soil. Today the same resource is providing data on carbon sequestration from over 40 years of direct observation of plant biomass, forest floor, and mineral soil.

The Calhoun is now managed collaboratively by Duke University and the U.S. Forest Service Southern Research Station (SRS). SRS research ecologist and science team leader Mac Callaham works with Duke soil scientist Daniel Richter to coordinate studies on a site that provides a rare opportunity for long-term observations on soil response to degradation, restoration, and sustainability.

Read about the next phase of research at the Calhoun, the Calhoun Critical Zone Observatory established with a National Science Foundation grant.

For more information, email Mac Callaham at

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The Calhoun Critical Zone Observatory

Recovery after extreme soil erosion and land degradation

by Sarah Farmer, SRS Science Delivery Group

As this picture from the 1950s shows, the Calhoun Experimental Forest suffered from severe erosion. Photo by U.S. Forest Service.

From surface to core, the Earth’s radius is almost 4,000 miles, but only the uppermost sliver of that rocky expanse, called the critical zone, sustains life. This zone extends from the base of weathered rock to the treetops, and includes water, soils, vegetation, and animals.  

A new study, led by Duke University and funded with a $5 million National Science Foundation grant, will bring university and U.S. Forest Service researchers and managers together to examine the critical zone and its recovery after extreme soil erosion and land degradation. Mac Callaham, a team lead at the Southern Research Station (SRS) Center for Forest Disturbance Science, will be one of a group of scientists involved in the study. Other participating institutions in the new Calhoun Critical Zone Observatory include the University of Georgia, Georgia Tech, University of Kansas, Mississippi State University, and Roanoke College.

The study will take place in the Calhoun Experimental Forest (Calhoun) located in Sumter National Forest in South Carolina. The Calhoun was established in 1947, a time when much of the Piedmont faced severe degradation. After well over a century of intensive crop production, erosion was so severe that nearly 6 inches of top soil had been washed into the rivers, while the abandoned cropland was furrowed by gullies and ravines. The land where the Calhoun was established represented the poorest of poor Piedmont conditions.

Today, almost 70 years later, the gullies and ravines are blanketed with leaf litter and shaded by trees, but the scars remain. Some experts have suggested that the reforestation indicates natural restoration processes, but the new study takes a more critical perspective. “Our study is guided by a hypothesis that the impressive-looking reforestation masks fundamental alterations to the local and regional hydrology, biology and chemistry,” says Daniel Richter, a researcher at Duke University and lead investigator of the study. “Much of the Piedmont may not be recovered so much as it has been re-stabilized in a highly altered state.”

Because the Calhoun Critical Zone Observatory involves studies of  historical and current geological and hydrological processes, along with land uses, vegetation patterns, soil dynamics, and a number of other factors, researchers from many disciplines will pool their expertise to discover how above and belowground systems are functioning and may have recovered.

Researchers will gather information about the site from a range of sources, from library archives to networks of wireless sensors—and  from the more than 60 years of data collected by the Forest Service and Duke University at the site. “We’ll also be digging holes to collect soil animals and doing some field studies,” says Callaham, who will be focusing on how different soil animal communities – especially earthworms – affect soil function. Callaham and his colleagues found earlier that different land uses led to different earthworm communities. “Native worms were reliably found in relatively undisturbed oak-hickory forest fragments, and occasionally in planted pines, but almost never in pastures or plowed fields,” says Callaham. “We are interested in the role of different earthworm communities in water infiltration, macropore density, and gas diffusion rates.”

Researchers are also interested in understanding how land degradation and reforestation affects the relationship between aboveground and belowground systems, as well as the long-term effects of erosion on organic carbon dynamics, how human-caused changes in the critical zone might affect human livelihoods, and how human-influenced critical zones might be forever altered, yet still stabilize and enter new steady states.

The Calhoun project is the newest addition to a network of six Critical Zone Observatories in the U.S., with more developing across the globe. Although the U.S. observatories are funded separately and focus on different aspects of the critical zone, their common goal is to develop predictive abilities for how the critical zone will respond to projected changes in climate and land use. The Calhoun study adds crucial information about how severely degraded land can recover and continue to provide clean water, air, and other ecosystem services.

Visit the Critical Zone Observatory website.

For more information, email Mac Callaham at

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