Jennifer Buss | ALES Graduate Seminar

A graduate exam seminar is a presentation of the student’s final research project for their degree.
This is an ALES MSc Final Exam Seminar by Jennifer Buss. This seminar is open to the general public to attend.
Thesis Topic: Impacts of Soil Stockpiling on Seed Bank Communities and the Availability of Nutrients

MSc with Drs. Brad Pinno and Sylvie Quideau.

Seminar Abstract:

Soil stockpiles are used around the world to reclaim sites affected by industrial activities. Oil sands surface mining and in situ extraction activities in Alberta, Canada, have directly impacted more than 900 km² of land, with more development expected in the future. Soil stockpiles will be essential for the reclamation of large- and small-scale oil and gas sites across Alberta with over half of the disturbed area expected to be reclaimed using stockpiled soils. However, stockpiling soils can lead to the degradation of soil biological, physical, and chemical properties, so it is critical that we understand the potential implications of using this soil in reclamation. Therefore, I studied the impacts of soil stockpiling on seed banks, aboveground plant communities and available nutrients.

To investigate the impacts of soil stockpiling, plant communities and nutrient availability were sampled in eight soil stockpiles of varying ages across Alberta. Four stockpiles and four nearby mature forest sites were sampled in the Cold Lake region and four stockpiles and two mature forest sites were sampled in the Fort McMurray region. Seed bank samples were taken from depths of 0-5cm, 5-10cm, 10-20cm, 20-30cm, and >50 cm and germinated in a greenhouse using the seedling emergence method. Aboveground vegetation cover was also estimated at these locations. Soil samples were taken from 0-10cm, 10-20cm, 20-30cm, and >50cm for a lab incubation to estimate the availability of macronutrients (NO₃^–, Ca²⁺, Mg²⁺, K⁺, H₂PO₄^– /HPO₄^2-, SO₄^2-) in stockpiled and mature forest soils using plant root simulator probes (PRS; Western Ag Innovations, Saskatoon, SK, Canada).

In Chapter 2 the impacts of soil stockpiling were represented by seed bank abundance, species richness, functional group composition, and the relationships between the seed bank and aboveground plant communities. In Chapter 3 nutrient availability was compared between stockpiles and mature forest sites, as well as with depth. Nutrient availability was also compared across stockpiles and mature forest sites.

The results of the seedling emergence study showed that stockpile seed banks had higher seedling abundance and species richness than nearby forested sites but were dominated by grasses and non-native forbs. Most seeds germinated from the surface layer, with 92% of seeds germinating from the LFH layers in the forested sites, and 68% from the 0-5 cm layer in the stockpiles. Mature forest sites had more similarities between the aboveground and seed bank communities than the stockpiles.

As indicated by the soil incubation, stockpiles had higher availability of Ca²⁺, Mg²⁺, NO₃^– compared to the mature forest sites. There was also high availability of NO₃^– below 20-90 cm in stockpiles. The variability with depth that was present in the mature forest sites for Ca²⁺, Mg²⁺, clay content, and pH were not found in stockpiles, likely due to mixing. Variability was high across stockpiles for NO₃^–, SO₄^2-, and H₂PO₄^–/ HPO₄^2- compared to the mature forest sites.

Planting or seeding on these stockpiles with desirable reclamation species may be useful in the future to supplement the seed bank. Salvaging fresh topsoil to shallower depths could also help prevent dilution of the seed bank. Variability in nutrient availability across stockpiles could mean that management of stockpiles and reclamation sites should be done on a smaller scale and focus on differences across stockpiles. Overall, all stockpiles were dominated by grasses and non-native forbs, despite higher variability in N, SO₄^2-, and H₂PO₄^–/HPO₄^2-.