Salt tolerance as a factor in determining suitability of northern grasses for revegetation of oil sands sites affected by tailings release water

We compared the effects of release water from the enhanced non‐segregating oil sands mining tailings (eNST) on the growth and physiological responses of three grass species varying in salt tolerance: a relatively salt‐sensitive Kentucky bluegrass ( Poa pratensis ), a moderately salt‐tolerant Alkali bluegrass ( P. juncifolia ), and a highly salt‐tolerant halophytic Nuttall's alkali grass ( Puccinellia nuttalliana ). Since salt concentrations vary in tailings depending on manufacturing technology and environmental factors, we also examined plant responses to eNST release water that was supplemented with 60 and 120 mM NaCl. The study demonstrated that the responses of P. pratensis , P. juncifolia , and P. nuttalliana to eNST varied according to their salt tolerance level, pointing to salinity as the major factor detrimental to plants. The eNST water severely reduced growth, chlorophyll concentrations, and gas exchange in P. pratensis , and the addition of NaCl aggravated the effects of eNST. The treatment with 50%‐diluted eNST water did not affect the growth of P. juncifolia . However, the 100% eNST and 50% eNST + NaCl treatments exceeded the tolerance threshold of P. juncifolia and decreased the growth and physiological parameters. Poa pratensis and P. juncifolia accumulated high levels of leaf Na in all treatments. Puccinellia nuttalliana showed little or no effects of the applied treatments on the growth and physiological parameters. It also excluded Na from the leaves and maintained low leaf Na/K and Na/Ca ratios. We recommend considering plants with superior salt tolerance levels for the revegetation of sites where roots may come in contact with oil sands tailings release water.