Background
A soil stockpile is a pile of soil created after stripping material off an oil and gas, or mine site, that is then stored for later use in reclamation. Topsoil stockpiles consist of the top 15-30 cm of the soil profile and are valuable for reclamation because they are dense in plant propagules, important for nutrient cycling, and enhance the growth of plants (Bowen et al. 2005; MacKenzie 2012).
There is a large volume of stockpiled soils in the oil sands region, with approximately 67 million cubic meters for eight mines as of 2009 (OSRIN 2014). One mine is planning on reclaiming approximately half of its lease using stockpiled soils (I. Sherr, pers. comm. 2018). Therefore, researching the potential of stockpiled soils for use in reclamation is going to be very important for the oil sands region, and Alberta.
There is a large volume of stockpiled soils in the oil sands region, with approximately 67 million cubic meters for eight mines as of 2009 (OSRIN 2014). One mine is planning on reclaiming approximately half of its lease using stockpiled soils (I. Sherr, pers. comm. 2018). Therefore, researching the potential of stockpiled soils for use in reclamation is going to be very important for the oil sands region, and Alberta.
In both natural forests and stockpiles the abundance of viable seeds is known to decline with depth (Buss & Pinno 2019; Dickie et al. 1988; Iverson & Wali 1982; Qi & Scarratt 1998). However, this trend is a problem for stockpiled soils because the whole pile is made up of topsoil, which has a high concentration of seeds (MacKenzie 2012). The concern is that seeds are being lost at depth, which are needed for future reclamation.
The goal of land reclamation is to end up with a diverse native plant community that is similar to what was present before disturbance. Therefore, much of vegetation sampling in reclamation is focused on looking for a trajectory towards a mature/natural forest ecosystem in the boreal forest of Alberta. In Virginia, they did see recovery of reclaimed mines towards the reference forest sites, but with many common forest species missing (Holl 2002). Getting woody species to establish on reclamation sites can and will be a challenge (Holl 2002).
The vegetation community occurring on the surface of the stockpile also impacts the seed bank to be used for reclamation. This association of the above ground vegetation and seed bank communities has been found in natural forests as well as on soil stockpiles in other countries (Beatty 1991; Olano et al. 2002; Rydgren and Hestmark 1997). Having an idea of what will be present in the seed bank community, based on what is in the above ground community will be important for future reclamation efforts and research in Alberta.
The goal of land reclamation is to end up with a diverse native plant community that is similar to what was present before disturbance. Therefore, much of vegetation sampling in reclamation is focused on looking for a trajectory towards a mature/natural forest ecosystem in the boreal forest of Alberta. In Virginia, they did see recovery of reclaimed mines towards the reference forest sites, but with many common forest species missing (Holl 2002). Getting woody species to establish on reclamation sites can and will be a challenge (Holl 2002).
The vegetation community occurring on the surface of the stockpile also impacts the seed bank to be used for reclamation. This association of the above ground vegetation and seed bank communities has been found in natural forests as well as on soil stockpiles in other countries (Beatty 1991; Olano et al. 2002; Rydgren and Hestmark 1997). Having an idea of what will be present in the seed bank community, based on what is in the above ground community will be important for future reclamation efforts and research in Alberta.
Research Objectives
1. Our first objective is to determine where most of the seeds are in soil stockpiles, and if their numbers decline with depth. This research will help to get a better idea of how deep soil can be salvaged before the seed bank is diluted and how much high seed density material could be available for reclamation in these stockpiles. We expect that the number of seeds will decline with depth. If this is the case, forming flatter stockpiles with a smaller volume of buried soil could be a better option.
2. Our second objective is to see if stockpile plant communities are becoming more similar to natural forest communities over time. If not, seeding of missing functional groups such as shrubs and tree species, or weed management could be considered.
2. Our second objective is to see if stockpile plant communities are becoming more similar to natural forest communities over time. If not, seeding of missing functional groups such as shrubs and tree species, or weed management could be considered.
3. Lastly, we would like to see if surface vegetation communities can be a good indicator of the seed bank community. This will allow companies to see if they will require additional seed bank testing or analysis before using a stockpile for reclamation. It is expected that the above ground community will be a good indicator due to their contribution to the seed bank from seed rain. However, some differences could occur due to competition with established above ground vegetation.