Characterization of soils in a drained Carolina bay wetland prior to restoration

Carolina bays are oval shaped wetland depressions in the Atlantic Coastal Plain. Many of these bays have been drained for agriculture and now are excellent sites for wetland restoration. This research was to evaluate the soils in a drained Carolina bay, Juniper Bay, for a successful restoration of wetland hydrology and vegetation. Juniper Bay was drained in three phases 30, 20, and 15 years ago and placed into agricultural production. Three natural Carolina bays were used for reference. The soils were grouped according to the thickness of organic material; organic (<60cm), histic (40–60cm), and mineral (<20cm). There was relatively low variability in physical and chemical properties among the reference bays. Juniper Bay soil groups were evaluated against similar soils in the RB, the length of time in agriculture, and for differences between crest and ditch locations. Bulk densities of drained organic soil and from the reference bays were used to estimate a primary subsidence rate of 3.9cm yr−1. Secondary subsidence rate was estimated to be 2.0 cm yr−1 using changes in bulk density and sand concentration between sub-surface organic horizons and surface horizons. Juniper Bay had higher nutrient levels and lower amounts of organic carbon compared to the reference bays. All soil types had higher nutrient levels, base saturations, and pHs, but lower organic carbon contents, cation exchange capacities, and total nitrogen levels the longer the soils had been in agricultural production. Depth of nutrient leaching increased from 40cm at 15 years to 65cm by 30 years. Differences were minimal between crest and ditch locations. In Juniper Bay the Oi and Oe horizons are absent, the Oa horizons are thinner, and organic carbon levels are lower, while bulk density, K_sat, and aggregation have increased. Soils near the ditch have thinner organic horizons and larger aggregates than soils near the crest. The original water table was at the original surface for part of the year. Plugging all the ditches could result in open water because of the estimated 60cm of subsidence. The increased nutrient levels could allow invasive species to out-compete desired bay vegetation.