Neal Smith National Wildlife Refuge
The Neal Smith National Wildlife Refuge (NSNWR) is located in Prairie City, Iowa, and comprises part of the Walnut Creek Watershed. Since its creation in 1990, the primary management objective at the Refuge has been the reestablishment and maintenance of the historical landscape - including plant communities (e.g., prairie reconstruction, oak savanna resotration) and animal communities (e.g., reintroduction of bison and elk). In addition, the Refuge seeks to restore important disturbance processes such as fire.
Of the Refuge's current area of 4,343 acres, approximately 18% have been planted to native prairie, while 579 acres are still rented to local farmers. New land within the Refuge boundaries, which comprise 8000 acres total, continues to be purchased by the government when consensual agreements are reached. More information about the refuge can be found at the Neal Smith National Wildlife Refuge and the Friends of the Prairie Learning Center websites.
Experimental Setup
Our research utilizes twelve experimental watersheds (0.5 to 3.2 ha each) within the NSNWR (Sites 1, 2, and 3 in the figure shown), established to test the effects of different perennial-annual plant mixture on ecohydrologic and biodiversity responses according to a fully replicated, incomplete block design (3 replicates X 4 treatments in 4 blocks). The treatments consist of varying proportions (0%, 10%, and 20%) of perennial vegetation within a row-crop system. The 10% perennial vegetation treatments either have the perennial vegetation all at the bottom of the watershed or in contour strips distributed from the lower portions to the upper portions of the watershed. The 20% perennial vegetation treatment has contour strips distributed across the watershed. Two additional watershed (4.2 and 5.1 ha) located adjacent to our study area and having 100% reconstructed native prairie were also included as part of the study design to provide a comparative baseline (established in 2004 as part of a companion project by the USDA-ARS National Soil Tilth Laboratory and the Iowa Geologic Survey; Site "0" in Figure 3). The two watersheds in Site 0 are not part of the balanced incomplete block experimental design but rather will be used as reference watersheds primarily to compare water and nutrient storage and transport. The perennial strips have a minimum width of 4 m and the minimum disturbance between strips is 36 m to accommodate agricultural operations between the strips. Pre-treatment data on key response variables were collected for 2005-6, perennial vegetation consisting of reconstructed native prairie was seeded during the summer of 2007, and post-treatment data collection began in spring 2007. Analysis of the pretreatment data confirmed that the watersheds had similar slope, soil textures, and soil carbon and nitrogen concentrations.