Carbon sequestration and nutrient accumulation in floodplain and depressional wetlands

We measured soil organic carbon (C) sequestration and nutrient (nitrogen-N, phosphorus- P) burial in Czech and Midwest U.S. freshwater floodplain and depressional wetlands to evaluate how landscape position and agricultural land use intensity affects C, N, and P retention. Land use in the South Bohemia of the Czech Republic is dominated by forest and pasture, whereas in the Midwest U.S., land use is dominated by row crop agriculture. Cs-137 and 210Pb dating of soil cores revealed comparable rates of soil accretion among wetland types, ranging from 0.5 mm/yr in a Czech floodplain wetland to 2.3 mm/yr in a U.S. depressional wetland. Carbon sequestration and N & P burial did not differ among floodplain (47 + 14 g C/m2/yr, 3.7 + 1 g N/m2/yr, 0.47 + 0.16 g P/m2/yr) and depressional wetlands (50 + 19 g/m2/yr, 3.6 + 1.3 g N/m2/yr, 0.51 + 0.14 g P/m2/yr). However, sediment deposition in Czech floodplain and depressional wetlands was only 10-50% (150-340 g/m2/yr) of rates measured in U.S. wetlands (650-1460 g/m2/yr). Our results suggest that, in agricultural landscapes, land use intensity rather than landscape position - floodplain versus depression - drives wetland C sequestration and nutrient retention through increased sediment deposition.