Microbial communities in organic substrates used for oil sands reclamation and their link to boreal seedling growth

Soil reconstruction in the Athabasca oil sands region utilises forest floor and peat materials as surface organic amendments to help reclaim decommissioned mine sites to upland boreal forests. The objective of this study was to characterize the microbial community in these two organic materials, and to determine the relationships between two boreal tree seedlings, aspen (Populus Tremuloides Michx.) and alder (Alnus crispa Ait), and their respective rhizosphere microbial communities. The forest floor exhibited a greater basal respiration than the peat, and a distinct microbial community structure as seen with phospholipid fatty acid analysis. Stable isotope probing showed greater carbon flow between trees and their rhizosphere communities when seedlings were grown in forest floor material. However, only the alder seedlings demonstrated correspondingly greater growth in the forest floor material. These results suggest that forest floor material fosters a microbial community which interacts more closely with boreal tree seedlings than peat does.