NATIVE PRAIRIE GRASSES AND MICROBIAL COMMUNITY RESPONSES TO RECLAMATION OF TACONITE IRON-ORE TAILING

The effect of reclamation treatments on seeded native grass cover and species composition, soil microbial biomass carbon, and populations of actinomycetes, fungi, free-living N-2-fixing bacteria, and aerobic he terotrophic bacteria was compared in field plots in coarse taconite ta iling. Reclamation treatments consisted of all possible combinations o f three rates of composed yard waste, three rates of fertilizer, and i noculation with arbuscular mycorrhizal fungi. Composted yard waste inc reased plant cover, soil microbial biomass, and populations of all gro ups of microorganisms compared with unamended, non-inoculated control plots. Microbial populations and biomass in tailing plots were low com pared with natural soils and were correlated with plant cover and avai lable P. Mycorrhizal inoculation resulted in a 6% increase in plant co ver, although this was not significant, and significantly enhanced N-2 -fixer populations in June but did not affect other groups of microorg anisms. There were no differences between moderate and high rates of c omposted yard waste. We conclude that incorporation of a moderate rate of organic matter can ameliorate the stressful conditions of coarse t aconite tailing and can enhance the initiation of a functional soil ec osystem able to support the establishment of seeded native prairie gra sses and may provide a long-term solution to reclamation of taconite t ailing.