Soil microbial communities identify organic amendments for use during oil sands reclamation

Most of the soil microbial community responsible for nutrient cycling in boreal forests is found in surficial organic horizons, often referred to as forest floor layers. In the Athabasca oil sands region of northern Alberta, Canada, reclamation of upland forests utilizes peat as an organic amendment due to shortages in forest floor materials. However, differences in physical and chemical properties between peat and forest floor raise the concern that the use of peat will fail to promote a soil microbial community consistent with sustainable forest ecosystems. As a strategy to maximize the limited supply of forest floor, this study investigated mixing both materials. Specifically, we determined the differences in microbial community composition and activity between fresh and stockpiled forest floor, peat and mixtures of both using basal respiration and phospholipid fatty acid (PLFA) analysis. Basal respiration increased with forest floor addition, but only responded to water content within the pure forest floor treatment. Mixing fresh peat and forest floor produced greater than additive respiration, and the overall PLFA profiles illustrated a microbial community more similar to the forest floor material than to the peat. This suggests a proportionally greater activity in the microbial community associated with the forest floor that is dominating the mixed treatment. Individual phospholipid indicators further demonstrated a distinct shift in their abundance going from the pure peat to the pure forest floor. Taken together, results provide evidence that mixing forest floor and peat provides benefits by increasing the water-holding capacity of the mixed material as compared to pure forest floor, while producing a microbial community more analogous to an upland forest community than to peat alone.