Evaluating wetland restoration success is complicated. In this study, soil organic carbon (SOC) pools in a Carolina Bay wetland (CBW) were determined for pre- and post-restoration periods and compared to values in reference wetlands to determine if SOC could be used to evaluate restoration success. The CBW was Juniper Bay in Robeson County, NC, USA, that had been restored for 15 years following its use for agriculture. Previously, we determined both pre-restoration SOCs and post-restoration hydrology. Saturation occurrence and anaerobic conditions (15 years following restoration) were confirmed with Indicator of Reduction in Soils (IRIS) tubes. Soil morphological features, litter thickness, and SOC to 75 cm were also determined. There were significant (p < 0.05) differences in numbers of hydric soil field indicators in the organic soils and no differences in the mineral soils (p > 0.10) between pre- and post-restoration periods. Litter thickness post-restoration increased linearly with saturation duration. SOC decreased following restoration by 49% in mineral soils and 24% in organic soils as compared to pre-restoration values. SOC concentrations in the restored wetland were not significantly different than those in reference wetlands indicating that the Juniper Bay restoration was successfully sequestering C. Litter thickness may be a good indicator of restoration success. SOC levels may decrease compared to reference wetland values if pre-restoration soils were in agriculture.

Restoring wetlands is expensive, and methods for evaluating restoration condition are needed. This study developed chronosequences for use in ecological assessments (EAs) of restoration projects for Carolina Bay wetlands (CBWs) in the Southeastern US that were previously used for agriculture. An empirical method was also developed to estimate saturation levels to be used with the chronosequences. Data were collected from nine restored CBWs whose restoration ages ranged from 0 to 23 years. Plots were sorted into four Hydrologic Groups: 0–13 (Group 1), 14–50 (Group 2), 51–100 (Group 3), and 101+ (Group 4) consecutive days of saturation within 30 cm of the soil surface during the growing season. Litter thickness, tree basal area, and potential tree height were measured within a variable radius plot using a 10-factor prism across all Hydrologic Groups. Litter thickness and tree height reached an equilibrium at 15 years since restoration once crown closure occurred at the sites. In Groups 1 and 2, tree basal area reached an equilibrium at 15 years, and in Groups 3 and 4 it increased linearly to 23 and 21 years. Regression equations were developed (R2 = 0.57–0.73) to estimate saturation duration based on hydrology indicators, litter thickness, potential tree height, and soil type. These results showed that chronosequences and saturation duration would be useful for proposing performance standards in restored CBWs at time periods ranging from 5 to 23 years.

Restoring wetlands on agricultural land can release soil phosphorus (P) to surface waters. Phosphorus is a limiting nutrient in many freshwater systems, thus restricting its release will improve surface water quality by preventing algal blooms. A P balance was used to examine how P was cycling in a Carolina Bay wetland eight years after restoration from prior-drained agricultural land. The change in soil P was evaluated between archived samples taken at restoration (2005), and eight years after restoration (2013). Measured P fluxes included atmospheric deposition, plant uptake, and loss to surface water outflow. The soil total P pool at the time of restoration was 810 kg P ha −1 . No significant (α = 0.05) decrease in the soil P pool was observed over the eight years. Atmospheric deposition contributed 1.0 kg P ha −1 yr −1 , plants incorporated 3.3 P ha −1 yr −1 into woody biomass and 0.4 kg P ha −1 yr −1 as forest floor litter, and 0.2 kg P ha −1 yr −1 was lost to surface waters draining the wetland. Because the loss of P to surface waters was small, and because runoff water concentrations of P declined through this period of study to concentrations below those likely to cause eutrophication (< 0.1 mg L −1 ), we concluded that the wetland was not contributing to the degradation of surface water quality of nearby streams following restoration. Further, isolated wetlands such as that studied may be promising sites for future wetland mitigation projects due to limited impacts on surface water quality.

Hydric soils are found in wetlands. They develop in areas that are saturated and anaerobic for periods long enough for redoximorphic features to form, and/or for organic C to accumulate, all within 30 cm of the soil surface. Hydric soil field indicators are soil layers having well-defined colors, specific quantities of redoximorphic features, and organic C contents, that are used to identify hydric soils in the field. The Hydric Soil Technical Standard describes how a hydric soil without field indicators can be identified using measurements to determine if the soil becomes saturated and anaerobic.

Restoring wetlands is expensive, and hydrology criteria are needed to determine if restored sites are saturated long enough to support the planted vegetation. This study determined relationships among hydrology, soils, and vegetation in a restored Carolina Bay wetland (CBW) to identify field indicators of saturation duration. The study site was in Robeson County, NC in a CBW that had been restored for 15 years. Water-table data for the five-year period following restoration were used to establish saturation periods of: ≤13, 14-50, 51-100, and 101-225 consecutive days occurring during the growing season and within 30 cm of the surface. Sampling plots were established 15 years after restoration along a hydrologic gradient to identify vegetation type, tree basal area, tree height, wetland hydrology field indicators, and inundation. The number of hydrology field indicators increased 50%, going from ≤13 to 101-225 days of saturation. Dominant tree species at the restored site were similar to those found in three reference CBWs. Where saturation occurred for 101+ days, tree basal area and height decreased 40-69% compared to where saturation periods were shorter. Areas that experienced saturation for <51 days contained trees that were 10 cm larger in diameter, had more shrubs and vines, and contained less areal cover of graminoids compared to areas that had saturation for 101- 225 days. Regression equations predicted average saturation duration during the growing season using number of hydrologic field indicators and tree height with R2 values between 0.62 and 0.73. Such relationships would be useful to evaluate restoration success.

Saprolite, weathered bedrock, is being used to dispose of domestic sewage through septic system drainfields, but the thickness of saprolite needed to remove biological contaminants is unknown for most saprolites. This study developed and tested a simple method for estimating the thickness of saprolite needed below septic drainlines to filter E. coli from wastewater using estimates of the volume of pores that are smaller than the length of the coliform (≤10 μm). Particle size distribution (texture) and water retention data were obtained for 12 different saprolites from the Piedmont and Mountain regions of North Carolina (N.C.). Saprolite textures ranged from clay loam to coarse sand. The volume of pores with diameters ≤10 μm were determined by water retention measurements for each saprolite. The data were used in an equation to estimate the saprolite thickness needed to filter E. coli. The estimated saprolite thicknesses ranged from 36 cm in the clay loam to 113 cm for the coarse sand. The average thickness across all samples was 58 cm. Saprolite thickness estimates increased as silt percentage decreased and as sand percentage and in situ saturated hydraulic conductivity increased. Silt percentage may be most useful for estimating appropriate saprolite thicknesses in the field.

Wetlands are often located in landscape positions where they receive runoff or floodwaters, which may contain toxic trace metals and other pollutants from anthropogenic sources. Over time, this can lead to the accumulation of potentially harmful levels of metals in wetlands soils. To assess the potential risk of Cu and Zn buildup in wetland soils in North Carolina, soil data from 88 wetlands were analyzed. In a subset of 16 wetlands, more intensive sampling was conducted. Samples were analyzed for Mehlich 3 Cu and Zn, and a subset of the samples was analyzed for total Cu and Zn. Overall, Mehlich 3 Cu and Zn were low, with mean values of 0.9 mg/kg for Cu and 3.2 mg/kg for Zn. Warning levels for Mehlich 3 Zn were only exceeded in three of the 88 sites; elevated Mehlich Cu was not observed. Total Cu and Zn were also low, with only a few sites having elevated levels; however, there was not a strong linear relationship between Mehlich 3 and total metals. Mean levels of Mehlich 3 Cu and Zn in wetlands were much lower than for human-impacted upland soils and background threshold concentrations that might be indicative of disturbance were much lower than warning levels for agricultural soils. The very low mobile Zn and Cu in most of these wetlands indicated that these metals do not pose a risk to the biota in most North Carolina wetlands, but wetlands with a direct and significant anthropogenic source of metal contamination could be exceptions.

The concept of hydric soils evolved over time with advances in soil science and wetland resource management. Hydric soils are identified in the field by examining morphological characteristics, including organic matter accumulation and redoximorphic features that form in response to prolonged periods of saturation and anaerobic conditions. The Hydric Soil Technical Standard (HSTS) was developed to provide a quantitative procedure for evaluating the hydric status of a soil based upon direct measurements of saturation, anaerobic conditions, and precipitation normality. In practice, the HSTS is used for (a) identifying hydric soils when a field indicator of hydric soils may not be present (e.g., naturally problematic or disturbed soils); (b) evaluating the current functional hydric status of a soil; (c) developing new field indicators of hydric soils; and (d) proposing changes to existing field indicators of hydric soils. The HSTS procedures have progressed over several decades with new approaches to soil analysis, including novel methods to document anaerobic conditions. The following review describes the development of the hydric soils concept and provides guidance for measuring each HSTS component. Practical approaches for collection and submission of HSTS data to the National Technical Committee for Hydric Soils, the group responsible for approving approaches to hydric soil identification in the United States, are also discussed. Expanding the understanding and application of the HSTS promotes technical accuracy, transparency, and efficient decision making in support of hydric soil and wetland resource management.

Potential impacts of climate change on the position of the wetland-hydrology boundary were estimated for four sites in the Eastern U.S. Precipitation and temperature predictions were obtained from the Hadley general circulation model (UKMO-HadCM3) because it most closely approximated observed precipitation for the period 1950–2000. The DRAINMOD hydrologic model was used to compute daily water table levels over two time periods: 1983–2012 (current conditions) and 2041–2070 (future conditions). For each site and time period, the model simulated water table depths for a soil pedon (Typic Paleaquult) that previous work demonstrated was on the wetland-hydrology boundary. Results for the Pitt County site in NC showed that by 2070 the wetland-hydrology boundary would have moved “downhill” to a point that was approximately 17 cm lower in elevation than where the boundary was in 2012 due to a 20% increase in evapotranspiration. Similar analyses were done for hypothetical wetland soils in Miami FL, Easton MD, and Portland ME where the wetland hydrology boundaries were estimated to drop in elevation by 5, 10 and 25 cm, respectively. Our results demonstrated that climate change may have significant impact on wetland boundaries.

Saprolite, weathered bedrock, is being used to dispose of domestic sewage through septic system drainfields, but its ability to remove coliforms is unknown. This study determined if Escherichia coli could be removed by a sandy loam saprolite material. Triplicate columns containing saprolite were prepared with lengths of 30, 45, and 60 cm. A 215-mL solution containing 1 × 105 CFU/100 mL of non-toxic E. coli was applied to the top of each column for 5 days/week for 13 weeks, and selected outflow samples were analyzed for E. coli. Control columns had only tap water applied to them at the same time. Significantly higher (p ≤ 0.10 compared to controls) E. coli concentrations were only detected in samples collected at the end of week 3 for the 30-cm columns and week 4 for the 45-cm columns. E. coli concentrations were small and ranged from approximately 2 to 3 MPN/100 mL. No E. coli were detected in any outflow from the 60-cm columns. From weeks 5 to 13, E. coli concentrations from all columns were either undetectable or not significantly different from the control. The results showed that 60 cm of sandy loam saprolite was sufficient for the removal of E. coli from simulated wastewater.

Core Ideas Normal rainfall ranges are best defined by the 30th and 70th percentiles of historic data. Mean ± SD produces a normal rainfall range twice as large as that of percentiles. Mean ± SD normal rainfall will cause some upland soils to be classified as hydric soils. Water table data collected for hydric soil and wetland identification studies require supporting analysis of rainfall normality. Water table measurements made after periods when precipitation is within a normal range are believed to represent long‐term trends, whereas data collected following periods of abnormally high precipitation represent rare events, potentially resulting in erroneous hydric soil determinations. The USDA‐NRCS currently uses two different methods to assess normal precipitation ranges; both have been used to assess hydric soils. This study compared methodologies that identify normal precipitation periods by using: (i) the range defined by the 30th and 70th percentiles observed within a 30‐yr period [i.e., the Climate Analysis for Wetlands Tables (WETS) method] and (ii) long‐term monthly mean precipitation ± one SD (i.e., the U.S. Soil Taxonomy method). Comparisons were made for 30 geographically diverse locations and soil moisture regimes. The results demonstrated that the U.S. Soil Taxonomy method yielded normal precipitation ranges approximately twice as large as those from the WETS method. As a result, the U.S. Soil Taxonomy method precluded the occurrence of drier than normal conditions in many instances and displayed increased sensitivity to infrequent high rainfall events. Three case studies evaluated the implications of method selection on hydric soil identification, demonstrating that the U.S. Soil Taxonomy method identified normal conditions more frequently than the WETS method. As a result, the adoption of the WETS method, which accounts for the non‐normal distribution of precipitation data, as the sole method to determine normal precipitation periods for hydric soil assessment is recommended.

Carolina Bay wetlands are distinct common components of the Southeastern US Coastal Plain. Many have a history of drainage for agriculture. Restoration of prior-drained Bays can increase P solubility and transport, with potential adverse impacts downstream. To assess risk of off-site P transport, we documented Bay land use, drained area, and proximity to streams and drainageways. We studied Bladen County, NC, where an exhaustive Bay inventory is available. Land-use was documented via classified Landsat decadal images from 1972 through 2010. We compared sequential image pairs to document land-use changes. Phosphorus risk to downstream waters was assessed based on stream proximity, agricultural land use, and arable area. At least 80% of Bays constituting 97% of total Bay area (51,704ha) exhibited evidence of land-use change. Edges of Bays comprising 80% of Bay coverage were within 15m of a stream; Bays comprising 13% were isolated. Twenty-one percent of Bay area remained drained in 2010. Prior, 28% of Bay area posed moderate to severe threats to downstream waters; as of 2010, 9%. Considering long-term effects of restoration-induced off-site transport of agrochemicals, land-use history, drained area, and stream/drainageaway proximity should be considered in choosing Bays for restoration.

Core Ideas Previous tree exposure to saturated conditions limited root death after ponding. Root growth and death had no apparent effect on concentrations of Fe2+, DOC, or DTP. Concentrations of Fe2+ were related to water table levels and redox status. Phosphorus concentrations were controlled by iron reduction and oxidation. Phosphorus (P) dissolution occurs commonly in wetland soils restored from agricultural land. Associated with P release are high concentrations of dissolved organic carbon (DOC) and Fe2+. This field study evaluated the effect of a fluctuating water table on the root dynamics of bald cypress (Taxodium distichum L. Rich.) to determine whether root death created soil reduction microsites, potentially contributing to P dissolution. The study site is a restored Carolina bay wetland with organic soils. Root growth and death were monitored on 16 6‐yr‐old bald cypress using minirhizotrons. Root dynamics, water table levels, and soil porewater chemistry and redox potential in the root zone were monitored for 2 yr. Soil solution samples were analyzed for Fe2+, pH, DOC, and P. High rates of root growth occurred during dry conditions, whereas root death occurred during sustained periods of saturation, particularly within 20 cm of the surface. Cyclic changes in concentrations of Fe2+, DOC, and dissolved total P (DTP) were related to water table position but not to changes in root numbers. After sustained periods of saturated conditions, redox potential decreased to 0 mV, Fe2+ increased to 1.75 mg Fe2+ L–1, and DOC increased to 350 mg L–1, resulting in peak DTP concentrations of 750 μg L–1, compared with 100 μg L–1 during dry periods. This study showed that in these high‐C soils (∼20% organic C) rooting dynamics had minimal impact on changes in P concentrations and that P dissolution was largely controlled by Fe reduction processes occurring within the C‐rich soil matrix.

Carolina Bay wetlands are common in the southeastern US Coastal Plain and important to water quality, carbon sequestration, and habitat. Only South Carolina and Georgia have statewide inventories. We developed and evaluated a novel way to identify and delineate Bays using Bay-dense Bladen County, NC as a testbed. We posited that Bay land use had changed in the past 40 years and that Bays comprise a small subset of their surrounding soils. We classified decadal Landsat images as forest, agriculture, urban, and water. We used 812 previously delineated Bays to identify common Bay soils. From areas with common Bay soils and land-use change, we identified 548 new Bays and delineated them using a semi-automated on-line digitization tool. We saved new Bays to a Google Fusion Table for download and integration within a GIS. To gauge accuracy, Bays were scored on soils, land-use change, wetland delineation, and landscape position. Potential errors included omission of some small Bays (3.3–14.6 % of total Bay area) and commission of misclassified Bays (11 % of 1360 Bays), an estimated overall accuracy of 74 to 86 %. With 1360 delineated Bays, we estimated that as many as 478 have not yet been identified. These are most likely <5.76 ha.

Phosphorus release to ground or surface waters has been observed in wetlands restored from farmland. This study examined whether rhizospheres of bald cypress (Taxodium distichum L.) are a source of increased P dissolution compared with the soil matrix. The study was conducted in root-box rhizotrons filled with mineral and organic soil materials (Aeric Alaquods and Terric Haplosaprists, respectively) from a Carolina bay wetland restored from row crop agriculture. Rhizotrons were planted with bald cypress saplings or left unplanted to simulate rhizosphere and matrix conditions, respectively. Ponding was imposed for 128 d. Soil pore water was sampled in three layers (0-22, 22-41, and 41-59 cm) in each rhizotron twice monthly for dissolved total and reactive P, dissolved organic C (DOC), Fe2+, and redox potential (Eh). Manual root counts monitored growth and death monthly. Root death was most prevalent at 41 to 59 cm, while vigorous root growth was observed near the surface. The rhizosphere treatments exhibited increased Fe2+ dissolution and increased concentrations of DOC relative to matrix conditions; however, no corresponding P increase occurred. Near the surface, rhizosphere P concentrations declined below matrix concentrations after 60 d of ponding. Our results show that the rhizosphere of bald cypress did not cause higher P concentrations than matrix values for mineral and organic soils with 3.5 and 19.5% C, respectively. In addition, root growth near the surface resulted in more oxidizing conditions and/or plant uptake of P, which decreased P concentrations below matrix values.