Biological Soil Crusts and Native Species for Northern Mine Site Restoration

The nitrogen cycle is highly sensitive to pollutants and restoration of this biogeochemical pathway is essential to ensure long-term sustainable ecosystems. In a greenhouse trial, the growth and nitrogen fixation rates of Dryas drummondii, Hedysarum alpinum, Oxytropis campestris and Lupinus arcticus were determined in both tailings and cover soils with amendments of rhizobia and biochar.  In a growth chamber trial, Pure Nostoc commune culture, Dried Nostoc spp. and biological soil crust (BSC) slurries derived from mature soil crusts were applied with and without biochar to tailings.  L. arcticus had the highest biomass and all species with the exception of D. drummondii showed nitrogen fixation after 3 months, with higher rates observed in cover soils. Nodulation and nitrogen fixation only occurred in herbs given a rhizobia innoculum, indicating the need for microbial amendments.  All mature BSC treatments had significantly higher rates of nitrogen fixation compared with other treatments. Inclusion of biochar did not significantly increase the rates of nitrogen fixation for BSCs, but did influence nitrogen fixation by native herbs. Including local native nitrogen-fixing species in seed mixes and establishing ay reduce the application rates 
of artificial fertilizer and promote plant community growth while establishing primary successional processes.