The Calhoun CZO is comprised of eight research areas in the Calhoun Experimental Forest and surrounding areas in the Sumter National Forest, including the Holcombe's Branch watershed, experimental catchments, and space-for-time (paired hardwood-pine-cultivated field) plots. The areas were chosen primarily for their wealth of historical data giving researchers an ideal platform for testing hypotheses on how critical zones evolve in response to human forcings at the landscape scale.
Calhoun Research Area 8, the newest and easternmost of the 8 CCZO research areas, includes adjacent pine and hardwood stands.
Calhoun Research Area 7, located south of the Enoree River, includes adjacent pine and hardwood stands. This is the southernmost of the 8 CCZO research areas.
Research Area 6 is centered on the historic Rose Hill Plantation, home of South Carolina's secessionist governor William Henry Gist (1807-1874).
Calhoun Research Area 5, located at the corner of Old Buncombe and Sardis Roads, includes adjacent pine and hardwood stands.
One of four historic Calhoun experimental catchments, which were instrumented with precipitation and runoff gauges from the 1940s to 1960s. The catchment was severely eroded and gullied and has been reforested over the last half century. The archived hydrologic records and photographs have been stored in the Coweeta Hydrologic Laboratory data vault since 1962. Contemporary hydrologic responses of the catchments will be compared with the historical data.
0.40 km2, 180-190 m elevation, 16 °C, 1250 mm/yr
The largest of the research areas at the Calhoun, this includes three major subsections: (1) the Calhoun Long-Term Soil-Ecosystem Plots and Reference Areas, (2) the "tower site" (site of future flux tower and clearcut treatment), and (3) the "dove field", which to our knowledge has been continuously cultivated since at least the 1930s. Also included in Research Area 1 is a 70-m deep well in a cow pasture on private land adjacent to the long-term plots.
16 °C, 1250 mm/yr
180-190 m elevation, 16 °C, 1250 mm/yr
134-157 m elevation, 16 °C, 1250 mm/yr
Three historic Calhoun experimental catchments are being re- and up-instrumented based on precipitation and runoff gauging from the 1940s to 1960s. The catchments were severely eroded and gullied and have been reforested over the last half century. The archived hydrologic records were stored in the Coweeta Hydrologic Laboratory data vault since 1962. Contemporary hydrologic responses of the catchments will be compared with those that are historic. The three experimental catchments reside within the much larger Holcombe's Branch, a tributary of the Tyger River. The Holcombe's Branch basin will be used to examine the erosion's interactions with soil carbon gains and losses.
Located in Union County, South Carolina, in the Southern Piedmont region and the heart of the Old South's cotton belt, the John C. Calhoun Experimental Forest is a 5082 acre (2057 hectare) area that has for nearly 70 years been the site of studies of land and water degradation caused by agricultural land uses. The Calhoun was organized October 8, 1947 in response to USDA Forest Service efforts of the 1930s and 1940s that aimed to restore highly degraded soils, forests, and water of the Southern Piedmont. Shortly after World War II, the Calhoun Experimental Forest was established on land so eroded, gullied, and degraded by agriculture that they considered it "to represent poorest Piedmont conditions" (Metz, 1958). When the Calhoun Experimental Forest's laboratory with its scientific staff was abruptly closed in the early 1960s, data collection in its four experimental catchments terminated but records were archived at Coweeta Hydrologic Laboratory, holding the potential to be re-used if and when the catchments are re-instrumented. Today the Calhoun Experimental Forest is managed by the USDA Forest Service's Southern Research Station and Sumter National Forest, Enoree Ranger District.
The Calhoun Experimental Forest warrants our interest not only because of its special 60-year history of research, but also because the history and contemporary uses of the site reflect important structures, forcings, and change ongoing in the large areas of the world not well represented among the initial six CZOs. The Calhoun's geologic substrata, landforms, vegetation, soil conditions, and land-use history are all closely comparable to conditions across much of the southeastern North America. The Calhoun's gently rolling to moderately steep landscapes are derived from granitic-gneiss which underlies nearly half of the Southern Piedmont (Richter and Markewitz 2001). The Calhoun has a warm temperate climate with mean annual precipitation and temperature 1300 mm and 16°C, respectively. Annual potential evapotranspiration averages 850 mm. Common soil series at the Calhoun include the Cecil, Pacolet, Appling, Cataula, Madison, and Chewacla, which comprise many of the region's most common soils. These advanced weathering-stage soils are common throughout the world in non-glaciated warm temperate regions and across the lowland tropics which are experiencing land-use pressures and conversions not dissimilar to those that have already affected the Calhoun.
For the exact locations of our research sites, see the map of Calhoun CZO Water, Soil, and Forest Sampling sites.