Plant abundance, diversity, and composition following reclamation in Alberta’s oil sands
The oil sands of Fort McMurray, Canada have caused an economic boom in the Canadian economy. Unfortunately, the oil extraction process has resulted in major, and sometimes irreversible, degradation of the natural landscape. Restoring oil sands to natural systems is the key mandate of oil sand development. The main restoration goal is to restore forest’s capability to produce and conserve levels of biodiversity and ecosystem services that match pre-disturbed ecosystems. Unfortunately, in many cases, this goal is unattainable. Due to the limitations of current knowledge restored forests rarely match the composition and structure of the original forest. In this study, we examined the dynamics of ground and shrub vegetation abundance, diversity, and composition following restoration and tested the effects of substrate, over-story composition, and age since restoration on oil sands disturbance sites. A total of 94 stands of conifer, mixed-wood, and broadleaf over-story types ranging from 5 to 30 years old with 6 substrate materials were studied. These substrates include: overburden, lean overburden, secondary overburden, clay overburden, and tailings.
Total vegetation cover decreased with stand age for all over-story story types. With the exception of clay overburden and secondary overburden, every substrate was significantly different, with overburden and tailings having the lowest cover values. Unlike total vegetation cover, woody species were not shown to have substrate as a significant variable in terms of cover. Similar to total abundance, total richness was driven by substrate and peaked in the younger stands. Multivariate analysis indicated that plant communities were compositionally distinct across substrates. Graphical analysis produced two distinct groupings of substrates: tailings/overburden and lean overburden/secondary overburden/clay overburden. Our results demonstrate that plant communities vary along substrates in terms of composition, as well as abundance and richness. Our results also show that age plays a role in the diversity of vegetation, as influenced by protocols enacted by the oil sands companies. Collectively, our results suggest that substrate and stand age are the most influential factors in the ongoing restoration of the oil sands.