Modeling salt redistribution and plant growth in reclaimed saline-sodic overburden upland forests: A case study from the Athabasca Oil Sands Region, Canada

Migration of salts from overburden/mine spoil with elevated salinity and sodicity into placed soil reclamation cover materials can adversely affect forest growth. In this study, we explored whether the ecosystem model ecosys which uses water potential and salt concentration gradients to simulate lateral and vertical water and solute fluxes can be used to determine the effects of salt redistribution on plant productivity in reclaimed landforms. In this study, salt transport and consequent effects on plant growth were simulated and tested against electrical conductivity (EC) and plant growth measured with soil cover depths of 35 cm, 50 cm and 100 cm in a 17-year-old forest reclamation site on a slope constructed on saline-sodic overburden in Northern Alberta. Overall, results from this study demonstrated the applicability of ecosys in predicting salinity effects on forest productivity in reclaimed landscapes. The modelled results showed that the upward salt movement from overburden to coversoil was influenced by the cover depth as observed in the measured values. Upward salt movement into the covers equilibrated with modelled downslope salt discharge after nine years from reclamation, maintaining a stable EC profile in the root zone. Even though modelled aspen vs. white spruce growth was adversely affected by salinity in shallow covers (≤50 cm depth) during dry years, long-term plant productivity in all the covers did not change markedly under the current climate. A clear topographical effect on salinity in the reclamation covers was not found during the study period, although the modelled salt discharge indicated a risk of salinization in downstream areas.