Estimates of Soil Erosion from Perched Cemeteries, Sampson County, North Carolina

Article excerpt

The Coastal Plain of the United States has not been recognized traditionally as a region experiencing significant soil erosion because of its low relief and permeable soils. Measurements of soil profile truncation in cemeteries were used to estimate rates of surface lowering and soil erosion in Sampson County, on the Coastal Plain of North Carolina. Measurements of the depth to the top of the argillic horizon (DTA) in relatively undisturbed profiles in small, perched cemeteries (ranging in age from 99-180 yr) were compared with adjacent cultivated fields. The mean truncation of soils from ten study sites was 25.8 cm, with the mean surface lowering of 2.0 cm. Correcting for compaction, this translates to a mean soil loss estimate of 24.4-27.4 Mg/ha/yr.

KEY WORDS: soil profile truncation, soil erosion, cemeteries, Coastal Plain, North Carolina

INTRODUCTION

Accelerated soil erosion associated with human activities has long been recognized to be problematic in many parts of the U.S. (Bennett 1931). Many studies have shown that poor land management practices associated with agricultural activities have led to large increases in upland soil erosion and floodplain sedimentation (Happ 1945; Knox 1972, 1987, 1989; Trimble 1974, 1981, 1983; Costa 1975; Meade 1982; Magilligan 1985; Phillips et al. 1993; Beach 1994; Lecce 1997). Although there is a general consensus that significant erosion has occurred within the Piedmont region of the eastern U.S. (Costa 1975; Trimble 1974), most researchers have considered erosion to be minimal on the Coastal Plain (Daniels, Gamble, and Wheeler 1971, 1978; Maxwell 1988; Markewich, Pavich, and Buell 1990; Beyer 1991). Recent research, however, has questioned this assertion (e.g., Phillips et al. 1993, 1999; Phillips, Slattery, and Gares 1999; Slattery, Gares, and Phillips 2002). The exposure of oxidized B-horizons in cultivated fields and the presence of cemeteries perched above the surrounding landscape provide qualitative evidence that soil erosion is significant in the Coastal Plain. The purpose of this study was to estimate post-settlement rates of soil erosion on Coastal Plain uplands in Sampson County, North Carolina, using measurements of soil profile truncation adjacent to perched cemeteries. Measurements of the depth to the argillic horizon (DTA) from these uncultivated cemetery sites, along with one uncultivated, virgin forest site, were compared to those from adjacent cultivated fields to assess differences in the rate of surface lowering and soil loss.

BACKGROUND

The southeastern Piedmont has long been considered a region with high rates of soil loss (e.g., Bennett 1931; Trimble 1974) due to its steep slopes and clay-rich soils with low infiltration rates and high runoff. Much of the soil eroded from the Piedmont, however, apparently remains within drainage basins in the region rather than being transported to the Coastal Plain (Costa 1975; Phillips 1991, 1992). Moreover, Phillips (1995) argued that sediment dynamics in the Piedmont and Coastal Plain are decoupled, with sediment transported in the Coastal Plain derived from erosion within the region.

The southeastern Coastal Plain, in contrast, is relatively flat with gentle slope gradients and soils with sandy, permeable surface horizons. Daniels, Gamble, and Wheeler (1971, 1978) and Markewich, Pavich, and Buell (1990) recognized that over geologic time scales the Coastal Plain is a stable surface with very low rates of erosion. Markewich, Pavich, and Buell (1990) believed that the high infiltration capacities of these sandy surfaces, rather than low slopes, are the primary reason for low rates of erosion in the Coastal Plain. Several studies, however, have documented accelerated rates of historic soil erosion within the Coastal Plain. Lowrance, Sharpe, and Sheridan (1986) reported accelerated erosion and sedimentation on the Georgia Coastal Plain following the onset of agricultural development in the 1870s. …