Dataset: Soil Redox and Hydropattern control Soil Carbon Stocks across different habitats in Tidal Freshwater Wetlands in a Sub-estuary of the Chesapeake Bay
Wetlands contain spatial and temporal variations in hydrology that affect vegetation and soil processes. In this study different wetland habitats were identified in both a natural and restored wetland site that varied in hydropattern (level of surface or ground water over time), with the goal of understanding how inundation impacts redox conditions and soil organic matter. Tidal freshwater wetlands were selected in Maryland, USA along the Patuxent River, a Chesapeake Bay tributary. Five habitats (mudflat, low marsh, high marsh, swamp, and adjacent upland) were selected at Patuxent Wetland Park, a natural wetland, and four habitats (mudflat, low marsh, high marsh, and adjacent upland) were selected at Wootons Landing Wetland Park, a restored wetland. Within each habitat three randomly located plots were established, and a data logging water level recorders were installed at one plot per habitat in February 2014 to monitor water level at 10-minute intervals. Water level depth was also measured manually in two additional observation wells within plots every two weeks for one year from February 2014 to March 2015. Soil cores to a depth of 50 cm were collected and soil C stocks were calculated based on soil bulk density and C percentage. Natural wetland habitats had shallower groundwater than their restored counterparts. Mudflats in both sites were most frequently flooded, followed by marsh and swamp habitats in the natural site. The restored high marsh that was dominated by Phragmites australis had the highest soil redox measurements at 12.5 and 40 cm soil depth (273±27 and 252±33 mv, respectively). Soil C stocks were also significantly higher in the natural compared to the restored wetland (14.8±0.50 and 8.9±0.99, respectively, P <0.0001). Restored mudflat and marsh habitats had similar hydrological regime compared to the natural counterparts, but they had lower soil C stocks. Monitoring of hydrology and vegetation in similar habitats in restored and reference sites may help improve restoration success in achieving specific structural or functional outcomes. Promoting the accumulation of soil organic matter in the restored wetland is not only controlled by the hydropattern, but also by the soil redox conditions that are impacted by the invasion of Phragmites australis.