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Influence of Amendments and Soil Depth on Available Nutrients and Microbial Dynamics in Contrasting Topsoil Materials Used for Oil Sands Reclamation

Howell, D. Mark. 2015. University of Alberta, M.Sc.

Abstract

As of December 2013, the cumulative area disturbed by oil sands mining in NE Alberta was 896 km 2 out of an estimated final footprint of 4,800 km 2 all of which will require reclamation. Expensive handling costs and scarce soil resources necessitate judicious management and application of salvaged topsoils and soil amendments such that the post - mining landscape is re - established to an %u201Cequivalent land capability%u201D of pre - disturbance conditions. Soil microbial communities and microbially mediated nutrient a vailability are largely overlooked in reclamation analyses, despite their potential in providing a sensitive measurement of ecosystem processes. This study measured nutrient availability and microbiological parameters in directly - placed forest floor mix ( FFM) and peat mix (PM) , which were compared to natural reference sites. The study was divided into two components: 1) assessing fertilizer and charcoal amendments (reclamation to d ecosite); and 2) assessing topsoil application depths (reclamation to a/b ecosite). 1) The principal study on CNRL%u2019s Reclamation Area - 1 (RA - 1) compares a fertilizer amendment on PM and FFM. I added a charcoal amendment to simulate natural additions to soil from wildfire; and compared reclaimed treatments to recently burned and unburned natural reference sites. Microbial biomass - carbon was greatest in natural and reclaimed organic soils. Burning and charcoal amendments tended to increase metabolic quotient, indicating potential nutrient stress or decomposition inefficiency. Nutrient profiles differed mostly between natural and reclaimed sites, followed by sites receiving fertilizer. Fertilization increased TIN availability by two orders of magnitude above unfertilized treatments, while P and K availability were below natural variation. 2) Syncrude Canada%u2019s Aurora Soil Capping Study provided Shallow and Deep topsoil application depths of PM and FFM which were compared to a control receiving no topsoil and a harvested analogue (Harvest). Soil respiration rates were greater in FFM and Harvest than in PM treatments, with no difference attributable to subsoil type or placement depth. Phospholipid fatty acid analysis (PLFA) and community level physiological profiles (CLPP) measured microbial community structure and function, respectively. Non - metric multidimensional scaling ordinations revealed the greatest similarity between FFM and Harvest for available nutrients, PLFA and CLPP analyses. Deep FFM application shared greatest PLFA similarity to Harvest, but Shallow FFM was more similar in CLPP. Shallow PM was more similar than Deep for all parameters measured. PM indicated greater TIN and S availability, and deficiencies in P and K compared to FFM and Harvest.