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Extensive areas of the northern mixed grass prairies of North America require restoration and reclamation as they have been extensively disturbed by agricultural, mining and oil and gas related activities. Amending seedbeds with mulch may avoid soil erosion and help both plant recruitment and early vegetation development in these water limited landscapes. A field experiment was established to determine if straw and hay mulch facilitate early revegetation. The site is an abandoned irrigation area in southern Alberta, Canada. Soil was tilled and the seedbed prepared through manual harrowing, then plots were broadcast seeded with Elymus trachycaulus, Bouteloua gracilis, Astragalus canadensis and Linum lewisii. Hay and straw mulch were applied at two rates (300 and 600 g m−2). Plant recruitment and cover were assessed through the first four years. Mulch had a positive impact on recruitment of all species planted except Bouteloua gracilis. While a thinner material like hay proved to be most effective at high rates (600 g m−2), a thicker material like straw encouraged quick recruitment for these species only at low application rates (300 g m−2). However, these early differences among mulch treatments did not show an impact in either recruitment or cover during subsequent years. Bouteloua gracilis, whose recruitment and growth were broadly impaired by mulch, showed an abundant and constantly increasing cover in the bare ground control and in plots with low application rates of hay. Both recruitment and cover per species indicate that plots are following two different trajectories that show some degree of resilience; the bare ground treatment is dominated by Bouteloua gracilis whereas the mulch treatments are characterized by vegetation dominated by Elymus trachycaulus, Linum lewisii and Astragalus canadensis. Fil: Mollard, Federico Pedro Otto. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura. Universidad de Buenos Aires. Facultad de Agronomía. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura; Argentina. University of Alberta; Canadá Fil: Naeth, M. Anne. University of Alberta; Canadá Fil: Cohen Fernández, Anayansi. University of Alberta; Canadá. Coastal Raintree Consulting; Canadá

Seedling establishment in semiarid prairie sites under reclamation can be facilitated by mulch due to its effects on seedbed conditions. Effects on plant recruitment can also be inhibitory, as mulch can filter out or attenuate environmental signals that break seed dormancy and can negatively affect early seedling performance. A manipulative field experiment was established to determine if straw and hay mulch facilitate seedling emergence and establishment. The reclamation site is an abandoned irrigation area in the mixed grass prairie of southern Alberta, Canada. Soil was tilled and the seedbed prepared through manual harrowing, then plots were broadcast seeded with Elymus trachycaulus, Bouteloua gracilis, Hesperostipa comata, Astragalus canadensis and Linum lewisii. Hay and straw mulch were applied at two rates (300 and 600 g m−2). Seedling emergence and survival were assessed through the first growing season. Both hay mulch rates increased E. trachycaulus and L. lewisii seedling emergence relative to bare ground. A. canadensis seedling emergence was more than ten times higher with low straw and both hay rates than with bare ground. Straw mulch facilitated seedling emergence at a low rate but had a neutral effect at high rates. Effects of low straw and both hay mulch rates on seedling establishment were facilitative for E. trachycaulus and L. lewisii and neutral for B. gracilis. Effects of high straw rates were neutral for E. trachycaulus and L. lewisii and hindered B. gracilis seedling establishment. These results clearly show that low mulch rates can increase native plant establishment during the critical first year of prairie reclamation as they were able to overcome microsite limitations.