Soil Properties in Natural, Restored and Farmed Closed Depressions on the Des Moines Lobe of Iowa: A Chronosequence Study of Restoration Timeframes.

The Des Moines Lobe landform region of Iowa is the most southern extent of the larger prairie pothole region. This region, consisting of closed drainage systems, poorly drained soils and wetlands, has been extensively artificially drained via subsurface tiles and surface ditches in order to promote agricultural productivity. By removing water from perennially wet soils, soil climate, morphology and chemistry has been altered. Attempts at restoring these wetlands have been made, but their success is not well documented in terms of soil properties. The objective of this study was to use a chronosequence approach to determine the restoration timeframes of soil properties within 30 years of closed depression wetland restoration by comparing restored soil properties to that of natural wetlands. This study collected soil samples from 21 closed depressions that were in 5 different stages of restoration including currently farmed soils, 10, 20, and 30 year restorations as well as natural soils. Soil chemical properties were found to have a faster rate of restoration than soil morphological properties. Soil macronutrients were consistent with natural concentrations within 10 years of restoration. SOM was found to increase significantly during 30 years of restoration near the soil surface, but did not change significantly deeper in the soil profile. Clay content decreased with restoration age and appears to have affected temporal patterns of CEC. Older restorations may be needed in order to further track the restoration progress of SOM and CEC. Results from our study can provide guidance for future efforts to understand long term anthropogenesis of wetland soil properties.