Soil landscape relationships on restored hillslopes on the Des Moines Lobe in central Iowa

Increased awareness of the economic and environmental values of prairie and wetland ecosystems has resulted in numerous areas of cultivated land being converted back to native ecosystems. Little information exists documenting the changes in soils and hydrology on these ecosystems. This dissertation includes studies of the hydrology, the sources of soil spatial variability, and the amount of carbon in restored prairie-wetland complexes in central Iowa. Four general groups were developed to describe soil hydromorphology along the restored prairie-wetland hillslopes. Soil morphology was correlated with hydrology for all groups on the restored hillslopes. Mean and shallowest water table depths varied for all groups. Group I included Clarion and Nicollet soils on upland prairie summits with redoximorphic features restricted to Bg and Cg horizons. Group II soils included Delft and Webster soils on upland prairie-backslopes. Group III soils included Canisteo and Delft soils on wet prairie or sedge wetland-footslopes. In general, group II and III soils had thicker A horizons than group I soils with low chroma mottles or pore linings and Bg horizons with low chroma mottles, high chroma mottles or a combination of both. Group IV soils included dominantly Okoboji soils in closed pond depressions with sola having a mixture of low chroma mottles, high chroma mottles, and low/high chroma pore linings. Soil depth explained most of the systematic variability in available K and P and total and organic C in upland prairies and wetland ecosystems. Sources of variability differed among prairie and wetland ecosystems for coarse silt, clay, bulk density, extractable cations, CEC, and pH. Highest soil microbial biomass C amounts and variability was in the upland prairie-backslopes. Slope position explained 52% of the total systematic variability in organic C. Soil depth explained for 74% of the total systematic variability in microbial biomass C. Our studies conclude (i) restored hillslopes are producing significant amounts of microbial biomass and organic C; (ii) longer term monitoring of water tables is required to better understand soil hydromorphic relationships; (iii) spatial relationships and variability attributable to site, transect, vegetation, slope position, and depth should be considered when assessing restored hillslopes.