Soil characteristics of four southern Appalachian fens in North Carolina, USA

Mountain fens are uncommon and unique wetlands in the southern Appalachian Highlands. We selected four mountain fens in North Carolina to compare soil particle-size distribution, organic carbon, pH, cation exchange capacity ( CEC), and exchangeable Mg+2, Ca+2, and K+. Three of the sites are depressio nal areas on alluvial floodplains at elevations between 700 and 1130 m abov e sea level, while the fourth site is located on a slope intersecting groun d-water seepage at an elevation of 950 m. Feat accumulation amounted to a s hallow surface Sphagnum layer (usually <5 cm) at three sites, and the organ ic carbon content of the surface soil horizon ranged from 4 to 21%. Three o f the soils would be classified as Cumulic Humaquepts, and the other is a T erric Haplohemist. The pH of the surface horizon of the four soils ranged f rom 4.3 to 4.9. The alluvial fens had higher silt concentrations than the s eepage fen, and two of the alluvial fens had a subsurface, fine-textured de posit. The seepage fen showed little textural variation with depth. Exchang eable Ca+2 concentrations were higher for the seepage fen. The CEC ranged f rom 15 to 62 cmol, kg(-1) in the surface horizon, and base saturation (Ca+2 , Mg+2, and K+) was <12% for the three alluvial fens and 20% for the seepag e fen. Base saturation increased to 40% in the lower horizons of the seepag e fen but remained <10% for the alluvial fens. The differences in soil char acteristics suggest that geomorphic location should be considered when comp aring mountain fens.