Date of Award
Master of Science
Theses & dissertations (Interdisciplinary)
Ecology and Evolutionary Biology
As interfaces between terrestrial and aquatic systems, riparian areas are important for many wildlife species. Like other natural communities in the Midwest, however, riparian areas have been greatly altered. Recently, habitat restoration through farm-bill and flood-mitigation programs, such as the Wetlands Reserve Program (WRP) and Emergency Wetlands Reserve Program (EWRP), has substantially increased the amount of riparian habitat in the midwestern United States. Working on restored areas in the Iowa River Corridor of east-central Iowa, I assessed the effects of management on vegetation structure and composition, the abundance and biomass of arthropods, and bird use and reproductive success. For a better understanding of important habitat features, I also investigated the relationships between vegetation and arthropod variables and bird use. Lastly, I quantified the extent of alteration of the Iowa River Corridor since settlement, the effects of restoration on the landscape, and the contribution of restored areas to bird populations. Restoration of riparian grasslands provided habitat for many bird species, including 9 grassland or wetland species of conservation concern. Although burning may have negatively influenced density of some bird species by removing residual vegetation and decreasing food resources, disking led to increased density of several species, and increased species richness and conservation value. Disking decreased cover of grasses, and increased forb cover; it also increased abundance and biomass of potential arthropod food resources. Dickcissels, in particular, appeared to respond positively to the changes brought about by disking. Nest success in these riparian habitats was generally low. Burning and disking, however, appeared to have positive effects on reproductive success, possibly by affecting the habitat use or foraging efficiency of predators. Although vegetation variables explained variation in bird density, species richness, and conservation value, adding arthropod abundance improved most models. Restored riparian grasslands in the Iowa River Corridor provided habitat for several bird species of conservation concern. Accounting for the influences of vegetation and arthropods, and using burning and disking as management tools, however, can likely increase the conservation benefits of these habitats for birds in the Iowa River Corridor and other riparian systems throughout the Midwest.
Thomas Jefferson Benson
Benson, Thomas Jefferson, "Breeding bird, plant, and arthropod responses to restoration and management of riparian conservation easements in the Iowa River Corridor, east-central Iowa" (2003). Retrospective Theses and Dissertations. 17510.