EFFECTS OF GRAZING AND HAYING ON ARTHROPOD DIVERSITY IN NORTH DAKOTA CONSERVATION RESERVE PROGRAM GRASSLANDS

A study of arthropod populations in North Dakota CRP grasslands was conducted to determine the impact of grazing and haying management practices on the arthropod fauna. Four sampling methods were used to collect arthropods: flight intercept traps, pitfall traps, sweep net, and soil samples. The three study sites occurred in Bowman, Ward, and Stutsman counties, North Dakota. Each site consisted of three pastures under a twice-over rotation grazed system, one pasture grazed seasonlong, a hayed field, and an idle area which served as a control. Shannon’s Index showed there were no significant differences in diversity among pastures or county sites. Correspondence analysis (COA) showed Diplopoda (millipedes) and Formicidae (ants) were correlated to idle and hayed treatments in which both groups had a higher mean abundance. Stutsman County had the highest mean abundance of millipedes. Two beetle families, Elateridae (click beetles) and Curculionidae (weevils), showed a trend toward the idle area from COA, but neither group had a significantly higher mean abundance in idle areas. Ward County had the highest mean abundance of both click beetles and weevils. Miridae (plant bugs) showed a strong trend to hayed fields where they had a significantly higher mean abundance. A significantly higher mean abundance of plant bugs was found in Bowman County. Acrididae (grasshoppers) were found equally abundant in all pasture types in 1995, but fewer were found in idle areas in 1996. The lowest mean abundance of grasshoppers was collected in Ward County. Grasshopper densities did not reach threatening levels in either year of this study. Based on the overall results grazing and haying appear to be viable options for post-contract uses of CRP lands with regard to management of arthropod populations.