Popular Science: From mining landscape to natural forest
Reforestation has been happening for a long time, but it is necessary to realize that it doesn't only mean planting a few trees. The focus should be on all of the natural landscape elements from the climate and relief to the flora and fauna. It's important to preserve the soil conditions, prevent erosion and to let the ecosystem (including the soil) develop to a state that is not prone to disturbances.
It's also important to take into account the forest restoration before the mining starts in order to make a plan that often includes preserving the original soil covering. The restoration process is very variable, depending on the location. In some conditions it's possible to achieve excellent results only with natural succession; in others, massive technical intervention is required. During the treatment of the relief, it's already necessary to perceive the soil, climate and hydrology conditions in the area. Reducing the slope is usually needed. On the other hand, it is necessary to make the interventions judiciously, because every movement of heavy machinery causes compaction, which is also undesirable. We need to prevent erosion, landslides and excessive subsidence of the soil. Even if the original soil is returned to the mining site, it's not the same soil as before. This soil is called Anthroposols in Canada, Udorthents in the USA, and Technosols in the world reference base for soil resources, and when stripped and then returned, the individual soil horizons are mixed. The content of organic matter, vegetation, soil microbial processes and soil fauna (which plays a significant role, particularly in the decomposition of organic material and aeration) are all very important for soil establishment and development. The choice of appropriate technology must respect the local conditions. Although using technology in drier areas is necessary, in a wetter climate (due to the soil compaction), it can cause more harm than good. The selection of suitable vegetation mainly depends on the soil properties and hydroclimatic conditions. In each case of reclamation, choosing appropriate pioneer tree species (e.g. birch, poplar, willow, aspen, and alder) and the main ones is vital. It is advisable to plant a mixture of tree species; this provides of a variety of potential habitats and allows the developing forest to build resistance and resilience to external stressors.
In Alberta, as in the United States, mining companies have an obligation to salvage and stockpile the topsoil after stripping it. In most countries of Europe, mined landscapes must be returned to their original use by reclamation and companies are required to have a reclamation plan. Topsoil salvage is only required when reclaiming to agricultural land. In Australia, where bauxite mining is in development, only the use of native tree species has been allowed since the 80s.
Although each region has its own characteristics and needs, it's possible to observe basic rules, which ensure a positive future development of the land after reclamation. According to the synthesis and observations in regions of North America, Europe and Australia, scientists came to common findings, which can be broadly applied to the development of best practices for forest restoration. This includes the usage and handling of stripped soil to minimize the undesirable effects on soil and vegetation redevelopment, facilitating natural regeneration as much as possible, using stripped soil, surface soil and woody materials to create heterogeneity at a variety of scales, leaving residual forest patches nearby when possible to serve as seed sources and propagule banks. Overall, it's useful to focus on slightly manipulated spontaneous succession with an ecosystem composed of representatives of the native vegetation.
The goal of successful restoration is for the forest to be productive and self-sustaining and to fulfill the environmental and socio-economic objectives.
by Kateřina Fraindová
Macdonald, S., E., Landhauser, S., M., Skousen, J., Franklin, J., Frouz, J., Hall, S., Jacobs, D., F., Quideau, S. (2015): Forest restoration following surface mining disturbance: challenges and solutions. New Forests, Vol. 46, Is. 5, s. 703-732.