How do you make soil where there isn’t any? We often take for granted this resource so essential to life on our planet – you just look down, and there it is. However, some environments, such as those impacted by humans, lack the building blocks for healthy ecosystems. Without soil there can’t be vegetation, and without vegetation there can’t be wildlife. If we think beyond individual habitats and ecosystems, without soil we lose so many ecosystem functions that we depend on – clean water, food, greenhouse gas storage, and more.
Soil scientists are key to rebuilding stable and safe conditions for humans and wildlife, and are often tasked with reclaiming the land after human impacts. Although a difficult task, land reclamation is essential to a thriving future.
One such soil scientist is Valerie Miller. Valerie completed her PhD at the University of Alberta with Dr. M Anne Naeth, researching how to build new soils for land reclamation in Northern diamond mines. Since diamonds were discovered in 1991, mining in the northern Canadian territories has increased dramatically. There are seven former or current diamond mines in Canada, with significant associated environmental disruptions and waste produced. These impacts are magnified in the arctic and subarctic, where short, cold, dry growing seasons create difficult conditions for soil and vegetation. Despite increased development and mining in the North, knowledge about land reclamation is limited. This is where researchers like Valerie come in.
One of the biggest challenges to Northern reclamation is where to source soil from. There is limited material available onsite and transporting materials long distances is not feasible. So we needed to look at building soil with what was available. My objective was to build suitable soils using online mining waste materials to support revegetation and site reclamation post diamond mining in the Canadian North.
Working in the Diavik Diamond Mine, Northwest Territories, Valerie aimed to build viable soil using the mining waste materials that were on site. These new soils would be called “anthroposols”, meaning that they were built or altered by humans. Valerie tested different combinations of soil forming components both in greenhouses and in field plots. She focused on understanding the features that yield healthy soil production so that her results could be applied to diverse land reclamation efforts around the world.
Mining tends to produce large amounts of waste materials, like crushed rock, that could be used to build soils; organic materials are often less available and may require a combination of on site materials, like treated sewage, and off site materials.
The first component to consider is the substrate which forms the basis of new soils. A good substrate promotes healthy and rapid plant growth by providing specific properties, such as how much water or nutrients it contains and how easily available these are to plants. Soil substrates need to be rough enough to trap seeds, ensure infiltration and deep percolation, and reduce erosion, while being fine enough to hold water long enough for plants to use it. While the perfect substrate may not exist, Valerie explored different combinations of crushed rocks, lakebed sediment, and processed kimberlite (the source rock of diamonds, a waste material after processing to remove diamonds), to understand how each could form the basis of a suitable anthroposol.
Adding amendments was the next consideration. Substrates may not be the perfect soil – they may be missing components. In the case of Diavik, the substrates were all very low in organic matter and nutrients, characteristics key for a healthy soil. On site organic materials for field experiments were limited to treated sewage and a small stockpile of available soil. Greenhouse experiments tested additional materials including peat, fertilizer, biochar, and Black Earth©, as well as combinations of materials. In the first few years, sewage appeared to be the most successful amendment, providing essential nutrients and organic matter, and being available on site.
There’s more to the environment than just laying down a flat bed of soil. It is necessary to consider the shape and features of land. When you look over a landscape, it’s rarely perfectly flat. Small differences in the shape and features of the land, from small centimetre variations to large metre high differences, play an important role in how new soils form and plants grow. These micro topographic variations trap seeds, provide protection from wind or water erosion, collect water and organic matter, and more. These differences play an important role in determining plant communities by creating a heterogeneous environment with different chemical and physical properties. The arctic tundra is naturally diverse, with boulders, cracks, and depressions; reclaimed land must mimic this.
So, what is the perfect recipe? It may depend on the land reclamation site. Valerie emphasized the strength of this research being in the large number of combinations of materials and placement methods studied in each experiment. The diversity in her research means that the results can be used for many different environments with different conditions and demands. Land reclamation demands flexibility and adaptability to fit each unique situation.
By building soils, we can tailor them to address site specific limitations. Using the knowledge we gained in this research, we can adapt these anthroposols to take advantage of local materials and be used at disturbances worldwide
About Dr. Valerie Miller
Valerie Miller completed her PhD in land reclamation at the University of Alberta in 2019, working at a diamond mine in northern Canada to build soils using mine waste. During her PhD program she was a teaching assistant, a course instructor, a community volunteer coordinator, and a volunteer with various science outreach organizations. Presently, Valerie is the Coordinator of the Land Reclamation International Graduate School (LRIGS) and the Outreach and Engagement Coordinator of the Future Energy Systems Research Program at the University of Alberta.