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5. Sandpits maintained mechanically <br />For this example, mechanical creation includes island lowering, discing, and vegetation <br />removal through herbicide application and/or chopping and mechanical maintenance <br />includes vegetation removal through herbicide application and/or chopping, predator <br />fencing, and predatar trapping. <br />Experimental Design <br />The study will be a quasi- randomized control-treatment experimental design. The <br />experimental unit will be an approximately 3 acre area of bare sand (at the appropriate <br />elevation). There will be two different types of experimental units for this study: river <br />and sandpits. The river experimental units will be river reaches with contiguous areas of <br />land on islands in the active river channel. The sandpit experimental units will be <br />contiguous areas of land that were mined for gravel. <br />The area of interest for this study will be the Platte River beginning at the junction of <br />U.S. Highway 283 and Interstate 80 near Lexington, Nebraska, and extending eastward to <br />Chapman, Nebraska. For treatment 1, the experimental units will be bare sand areas that <br />develop in locations immediately downstream of clearing and leveling actions. For <br />treatments 2 and 3, experimental units will be selected by a systematic procedure with a <br />random start within those properties available for study. For treatment 4, the <br />experimental units will be bare sand areas that develop in locations distant from and not <br />influenced by clearing and leveling actions. Sandpit experimental units (treatment S) will <br />be selected by a systematic procedure with a random start within those properties <br />available for study. <br />There are additional variables that could be incorporated into the design as treatment <br />variables (i.e. presence of habitat complex). Variables that are not incorparated into the <br />study design, will be evaluated in the analysis as covariates. Some of these covariates <br />include flow, population size, width of river, and adjacent management activities. <br />This study will encounter difficulties as a result of the existence of two types of <br />experimental units (i.e., sandpits and in-channel areas). Some management activities that <br />could be evaluated for effects on reproductive parameters will not apply to both the river <br />and sandpit units (e.g. width of river, island size). In addition, there could be <br />confounding influences between the two types of areas that are not estimable. <br />It is possible that a paired design could be implemented to minimize spatial variation. A <br />paired design would be effective at reducing variation if there are localized influences on <br />reproductive parameters that have not been incorporated into the design (e.g., localized <br />flood events). This paired design would require assumptions of independence to be <br />addressed for the units located in close proximity. <br />Replication <br />The study design will be balanced and will involve 5 replicate experimental units for each <br />of the 5 treatments, for a total of 25 experimental units. Since we can not determine how