Amendment of Biochar Improves Growth of Aspen on Oil Sands Reclamation Cover Soils Due to Changes in Nutrient Availability and SOM Stability.

Surface mining of oil sands in northern Alberta is a large-scale disturbance with over 900 km² affected to date. Extraction companies are required by law to return the environment to ‘equivalent land capability’, but this has proved challenging to quantify meaningfully and only one site has been certified as reclaimed. Restoring ecosystem function might be a more practical goal for reclamation. In a greenhouse study, we tested the effect of biochar amendment on the productivity of aspen (Populus Tremuloides Michx.) seedlings on Peat-Mineral-Mix (PM) and Forest-Floor-Mineral-Mix (FFM). Biochar is a native component of boreal forest soils in northern Alberta and is known to improve a variety of soil characteristics, for example, soil water retention and the biogeochemical environment. Peat, which is being used for reclamation and is available on site was used the produce the biochar. We compared an operational used PM to FFM, which is a reclamation substrate that is proven to function more similarly to natural benchmarks. All substrates were tested with and without biochar amendment. Our study showed a significant increase in aspen seedling productivity with biochar amendment for PM and a positive trend for FFM. Consequently, amendment of charred peat to PM could be considered as a tool for improving oil sands mine reclamation. This practice might reduce seedling mortality and lead to forest stands which are more comparable to natural boreal forest and potentially can provide similar ecosystem services. Our analysis showed that by amending biochar to PM, SOM characteristics were changed to be more similar to FFM as characterized by simultaneous thermal analysis. Treatments with biochar amendment showed lower root exudation, which might be related to changes in geochemistry. Potassium and Sodium interactions showed significant correlations with growth in the trial, which were influenced by biochar amendment.