Document Type

Thesis

Degree Name

Doctor of Philosophy (PhD)

Department

Geography & Environmental Studies

Program Name/Specialization

Environmental Science

Faculty/School

Faculty of Arts

First Advisor

Dr. Richard Petrone

Advisor Role

Supervision

Second Advisor

Roxane Andersen

Advisor Role

Guidance on statistical analysis

Third Advisor

Robin Slawson

Advisor Role

Thesis review

Abstract

Peatlands have a unique biogeochemical function, characterized by an imbalance between the rates of biomass accumulation and decomposition. These characteristics facilitate the ability of peatlands to support the sequestration of nutrients and carbon. In disturbed peatlands, these functions are compromised. Thus, reclamation targets amongst other key functions, the recovery of biogeochemical functioning. These functions could serve as a measure of recovery to conditions that are present in natural analogues. This thesis examines the recovery of microbially-mediated nutrient transformation processes in a fen peatland that was constructed on a post-mining landscape in the Athabasca oil sands region, Fort McMurray, Alberta. The major themes of this thesis examined (1) the concept of developing a functional-based approach for evaluating the functioning and trajectory of the constructed fen, (2) the impacts of donor-peat management practices on the resulting peat quality and the potential implications to the ecohydrological functioning of the constructed fen, (3) the evolution of above and below-ground nutrient transformation processes among different revegetation strategies in the constructed fen, and (4) the effect of revegetation and edaphic variables on the greenhouse gas (GHG) dynamics of the constructed fen.

The concept of developing a functional-based approach for evaluating the functioning of a constructed fen was examined by synthesizing the dominant processes of peatland development. The interactions and feedback processes that underlie various peatland ecosystem functions and their quantifiable variables were identified through this synthesis. This also highlighted the sensitivity of microbially-mediated biogeochemical processes to a range of variability in other ecosystem processes. As an alternative to the bio-indicator approach, microbially-mediated biogeochemical processes present potential functional indicators of ecosystem function.

The impact of donor-peat management practices on the ecohydrological functioning of the constructed fen was studied using cores extracted along transects in the donor fen before peat transfer, and after placement in the constructed fen. Relative to the properties of a reference fen, the donor-peat had a higher surface bulk density, and higher concentration of extractable nutrients. Transfer of peat to the constructed fen increased the near-surface bulk density, and decreased organic matter content and concentration of extractable nutrients.

Evolution of above and below-ground nutrient transformation processes were assessed among different revegetation strategies, over the first two growing seasons post-construction. Revegetation facilitated both above-ground productivity and the cycling of below-ground nutrients. Supply of labile substrates in the re-vegetated plots increased microbial potential activity, which was reflected in higher rates of respiration, nutrient acquisition and productivity. Nutrient dynamics within the constructed fen suggest that phosphorus limitation could hamper the establishment of a diverse plant community, whereas the build-up of microbial biomass appears to be NO3- limited. Ammonification, nitrogen mineralization and phosphorus availability were identified as potential functional indicators of the fen’s recovery.

Finally, the effects of revegetation strategies and environmental characteristics of the constructed fen on GHG dynamics were examined. Relative to a natural fen, significantly lower (p < 0.001) fluxes of methane (CH4) were observed in the constructed fen. This correlated with higher bulk density, lower organic matter content, and higher pH and SO42- concentration. Revegetation did not stimulate CH4 production, but increased carbon dioxide (CO2) uptake and reduced the global warming potential (GWP) contribution of nitrous oxide (N2O) by 63CO2-e m-2 yr-1 relative to the non-vegetated control. These studies provide a novel insight into the concept of assessment of a constructed fen ecosystem through the evolution of biogeochemical functioning.

Convocation Year

2016

Convocation Season

Spring

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