Response of aquatic vegetation communities and other wetland cover types to floodplain restoration at Emiquon Preserve

More than half of the natural wetlands in the Illinois River valley (IRV) have been lost through conversion of floodplain wetlands and lakes to drainage and levee districts for agricultural production. During 2007–2013, we monitored the response of wetland vegetation communities to restoration at Emiquon Preserve, a former floodplain that was drained and farmed for more than 80 years. Spatial coverage of wetland vegetation and other cover types rapidly expanded from 252 ha in 2007 to 1,944 ha in 2013 (mean 1,512 ± 239 ha) with little supplemental planting or hydrological management. Restored vegetation emulated aquatic plant communities that were largely eliminated from the IRV, most importantly floating-leaved and submersed aquatic vegetation. Mean annual wetland cover included aquatic bed (44%), open water (20%), persistent emergent vegetation (10%), hemi-marsh (10%), and nonpersistent emergent vegetation (9%). Average moist-soil seed and tuber density was similar to managed wetlands in the IRV (mean 724 ± 224 kg/ha). A viable option for restoration of diverse aquatic macrophyte communities within degraded wetlands of large river systems includes passive restoration of hydrology and vegetation behind levees while maintaining infrastructure to facilitate drawdowns when necessary or to mimic historical conditions.