Date of Award
Doctor of Philosophy
Arnold G. van der Valk
The purpose of this dissertation is to evaluate recent prairie wetland restorations to see if they are comparable to natural wetlands and to provide guidelines for site selection, design, and performance of future restorations. Detailed studies were made of the revegetation and water regime of 62 wetlands restored in 1988. Wetlands were evaluated to see if they have the potential to: (1) improve water quality, based on watershed land use, basin morphometry, and emergent vegetation development, and (2) provide wildlife habitat, based on landscape pattern, water regime, and vegetation composition. Most restorations are small (less than 4 ha) and are restored to be seasonal or semipermanent wetlands. Few restored wetlands (16.1%) seem to receive high loadings of agricultural pollutants because watersheds of most restored wetlands are more than one-half permanent cover. Wetlands restored by removing drainage tile (17.5%) that receive high loadings of nutrients may not improve water quality because residence time is too short. Inlets and outlets in these wetlands are typically adjacent to each other. The vegetation compositions of wetlands flooded for one, two and three years were compared to environmental and historical factors for the 62 wetlands. Mantel tests were used to determine if either factor accounted for vegetation differences among sites. The vegetation recolonizing restored wetlands within one year of flooding was found to be affected by past land use. A TWINSPAN ordination of these sites showed that wetlands drained by ditches or ineffectively drained by tile are recolonized by shallow emergent species that likely survived drainage as refugial populations. Tiled wetlands were colonized by mudflat annuals and submersed aquatics. Wet prairie and sedge meadow species were generally not found. A study of ten restored wetlands flooded for three years and ten natural wetlands showed that the mean number of species in the flora of natural wetlands and restored wetlands was 45.8 and 26.9 species per basin, respectively. Seedbanks of natural wetlands were also more diverse than those of restored wetlands with a mean of 15 species for natural wetlands and 8 species for restored wetlands. Thirty-seven wet prairie and sedge meadow species of natural wetlands (including typical dominants) were not found in restored wetlands.
Digital Repository @ Iowa State University, http://lib.dr.iastate.edu/
Susan Marie Galatowitsch
Galatowitsch, Susan Marie, "Site selection, design criteria and performance assessment for wetland restorations in the prairie pothole region " (1993). Retrospective Theses and Dissertations. 10428.