Carl Trettin explains long-term soil studies installed on the Santee. Photo by Rodney Kindlund.
In 1934, the U.S. Forest Service allocated 6,100 acres of the Francis Marion National Forest (Francis Marion) near Charleston, South Carolina, for the Santee Experimental Forest (the Santee).
By the 1930s, much of the site had been heavily used for centuries. The upland had been cleared to raise livestock and produce naval stores (tar, pitch, turpentine, and other products from pine), while rice and indigo were cultivated in the bottomlands. Between 1897 and 1929, the area was heavily logged. Early research on the Santee focused on thinning and fire management in loblolly pine stands.
In the 1960s, in response to new concerns about the impacts of a burgeoning timber industry, Forest Service researchers set up gauged weirs in the Santees streams and weather stations on watersheds to study the effects of forest management activities on the soils and waters of the Coastal Plains.
From the Santee Experimental Forest. Photo by Rodney Kindlund.
The Santee includes four gauged watersheds of different sizes. Researchers began their first long-term hydrologic observations in 1964, using the four watersheds to study soil moisture dynamics and runoff processes, as well as the effects of different types of land management practices such as reducing the forest understory (through prescribed burning), clearcutting, thinnings, and constructing drainage and impoundments.
Though not much was published at the time, the data collected between 1964 and 1982 was fundamental in documenting a hydrology altogether different from mountain watersheds.
“In the mountains, water moves fast down steep slopes, but in coastal areas, water moves in a slow, diffuse way,” says Carl Trettin, team leader for the SRS Center for Forested Wetlands based at the Santee. “In the Coastal Plain the riparian zone is much wider, so much more sediment is captured before it can enter the rivers. This also means there’s greater potential for mitigating nutrients such as nitrogen because the water is moving slow enough for the denitrifying bacteria to do their job and convert nitrogen to nitrogen gas.”
These differences in water flow, water balance, and nutrient cycling processes between mountain and coastal landscapes underscore the importance of the long-term data collected from the Santee weirs and rain gauges, especially now, as changing land uses put new pressure on water sources in the Coastal Plains.
After 1982, there were no Forest Service hydrologists around to analyze data from the weirs and rain gauges on the Santee. Fortunately, technicians on the site steadily kept records over the years (except from 1982 until after Hurricane Hugo in 1989) from both weirs and weather stations, storing them in whatever format was available at the time—tape, floppy discs, and often on paper.
The Santee unit finally got another research hydrologist, Devendra Amatya, in 2002. With urban development fast encroaching on the Francis Marion, pushing water-quality issues to the forefront, Amatya began bringing together a wide range of cooperators interested in using science to ensure water quality and quantity in the Charleston area. In 2004, he started a research initiative focused on the Turkey Creek watershed in the Francis Marion with partners from colleges and universities, private industries, and State and Federal agencies joining SRS scientists in studies of the urbanizing landscape in relation to water quality.
As part of the project, cooperators revived one of the gauged weirs set up more than 40 years ago on the Turkey Creek watershed to provide the long-term baseline data that will help SRS scientists and regional planners look at the effects of land management and climate on the poorly drained watersheds of the Coastal Plains.
“No matter what happens, the real challenge,” Amatya says, “is to not let new threats—from population growth to climate change—catch scientists and leaders off guard.” Forest Service employees and collaborators celebrated the 75th anniversary of the Santee in 2012.
With University of New Hampshire research scientist, Zhaohua Dai, Trettin and Amatya just published an SRS General Technical Report titled Effects of Climate Variability on Forest Hydrology and Carbon Sequestration on the Santee Experimental Forest in Coastal South Carolina.
For more information, email Carl Trettin at ctrettin@fs.fed.us or Devendra Amatya at damatya@fs.fed.us.
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