Military training can lead to disturbed soil conditions that are prone to non-native weed invasion and erosion.  It is common practice to plant cover crops (bridge species) onto disturbed areas, but the effects of these cover crops on the establishment of native communities is not well known.  We began an experiment at Fort Riley, Kansas to test the effectiveness of two species of cover crops in providing vegetative cover and potentially facilitating the establishment of four C₄ prairie grasses (Andropogon gerardii, Bouteloua curtipendula, Schizachyrium scoparium, and Sorghastrum nutans).  We hypothesized that C₃ cover crops would facilitate the establishment of C₄ prairie grasses, and we predicted that western wheatgrass (Pascopyrum smithii) would facilitate C₄ prairie grass establishment better than smooth brome (Bromus inermis).  We also predicted that western wheatgrass and smooth brome would decrease bare ground, decrease non-native weed abundance, decrease soil moisture, and alter the uptake and movement of isotope labeled nitrogen (¹⁵N).  In April 2006 we initiated four seed sowing treatments: 1) nothing sown; 2) only four C₄ prairie grasses sown; 3) western wheatgrass and four C₄ prairie grasses sown; and 4) smooth brome and four C₄ prairie grasses sown.  We will measure percent bare ground, vegetation cover, soil moisture, and ¹⁵N uptake and movement for several years in this experiment as well as in nearby non-disturbed and non-manipulated areas.  In addition, we will compare our results to a greenhouse study we began in September 2005 that also examines the effects of cover crops on the establishment of plant communities.