Growth of Common Plants of Boreal Reclamation Sites in Oil Sands Tailings Cake Mixes and Process Water

Oil sands surface mining and processing in Alberta generate large volumes of fluid tailings and process water high in salts and metals, which must be reclaimed. We investigated growth of four common plants (two native and two non-native) found in boreal oil sands reclamation sites as influenced by substrate type (tailings cake, and mixtures of cake-sand, cake-peat, and cake-forest floor mineral mix) and water quality (0%, 50%, and 100% oil sands process water). Overall, cake-peat supported the highest aboveground biomass among substrates whereas cake and cake-sand performed poorly, possibly due to high sodium and chloride concentrations. Adding process water to substrates generally reduced growth or increased mortality. Grasses had greater growth than forbs, and for each functional group, non-native species performed better than native species. Hordeum vulgare had the highest overall growth with no mortality followed by Agropyron trachycaulum with negligible (0.5%) mortality. Chamerion angustifolium was most affected by the treatments with the lowest growth and highest mortality (56%). Sonchus arvensis had higher growth than C. angustifolium but its slow growth makes it less suitable for reclaiming tailings. Our results indicate that H. vulgare and A. trachycaulum could be good candidates for use in initial reclamation of oil sands tailings.