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Influence of Capping Depth on Forest Reclamation Success in the Athabasca Oil Sands
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- Author / Creator
- Venskaitis, Sara A. S.
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Surface mining in the Athabasca Oil Sands region (AOSR) of Alberta, Canada, has led to the removal of over 760 km2 of boreal forest. Successful reclamation of these areas must return them to an equivalent capability boreal forest community. Clearwater overburden is a saline byproduct of surface mining, used in the construction of large-scale, out-of-pit landforms. To reclaim these landforms, a capping treatment is placed upon them to provide a suitable rooting media, and ensure the re-establishment of a forest vegetation community.
Using a range of peat-mineral mix (PMM) and subsoil capping thicknesses on existing Clearwater overburden reclamation sites in the AOSR, I sought to assess the long-term effects of soil cover thickness and material on boreal forest growth and development. I compared the tree height and dbh of planted trembling aspen (Populus tremuloides) and white spruce (Picea glauca) over 19 years, and at 9 and 13 years post-planting. As of 19 years post-planting at an overburden capping trial, I was able to observe a trend towards taller trees in the thickest capping treatment (100 cm, versus 50 and 35 cm), but only for the fast-growing, early-successional trembling aspen. The slower-growing, typically mid-successional white spruce did not display differential responses among the capping treatments. Examining 13-year-old sites with 100 cm of capping demonstrated high site-to-site variability in growth outcomes. Comparing the performance of the 100cm capping treatment against a thicker, 150 cm treatment at 9-year-old sites found no height or dbh differences for either species.
I additionally compared understory communities over 19 years and at 13 years after the planting of trees. Over 19-years, communities trended towards expectations for more natural boreal forest communities (increased litter cover, increased presence of forest species) but the continued presence of introduced and noxious species was notable. At 13 years, high site-to-site variability distinguished the sites of the same treatment (100 cm) but communities with different treatments (100cm, 50 cm, and 35 cm) on the same site were more similar to each other.
I conclude that trembling aspen growth suggests 100cm of PMM capping (versus 50 cm or 35 cm) is a sufficient thickness for this species, and further investment in 150 cm of capping is not justifiable at this time. White spruce did not display any differences in growth between any of the treatments sampled to date. Understory communities have progressed towards some expectations of natural boreal forest communities, but high site-to-site variability for the same treatment indicates that PMM capping treatment may not play a dominant role in this process. -
- Graduation date
- Fall 2019
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- Type of Item
- Thesis
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- Degree
- Master of Science
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- License
- Permission is hereby granted to the University of Alberta Libraries to reproduce single copies of this thesis and to lend or sell such copies for private, scholarly or scientific research purposes only. Where the thesis is converted to, or otherwise made available in digital form, the University of Alberta will advise potential users of the thesis of these terms. The author reserves all other publication and other rights in association with the copyright in the thesis and, except as herein before provided, neither the thesis nor any substantial portion thereof may be printed or otherwise reproduced in any material form whatsoever without the author's prior written permission.