At the former Diplomat Mine near Forestburg, Alberta, Canada we find a diverse soil landscape which can help to conceptualize factors and processes controlling initial pedogenesis and soil distribution on very young landforms in prairie environments. Due to differing reclamation practices in the 1950s and landslides occurring after spoil dumping, four areas can be distinguished by GoogleMaps/LiDAR evaluation and onsite field survey: (i) not-mined, (ii) stock piled and unreclaimed, (iii) stock piled and reclaimed and (iv) affected by post-mining geomorphodynamics and quasi-natural redeposition. The parent material for areas (ii) to (iv) was initially dumped by spreaders but only (ii) didn’t undergo further change. Landscape (iii) has seen levelling of the piles by heavy machinery. Features of landscape (iv) are formed by reshaping the originally dumped and levelled structures. This last landscape unit marks the rim of
the former mine adjacent to the river valley. In practice, mining activities formed new valley slopes. In contrast
to the naturally developed slopes the mine slopes were less stable. Vegetation, which could have hindered slope
wash erosion, was missing after dumping the spoil slopes. Slopes were very steep (or practically undercut) and
therefore, substrates were naturally re-located by mass movements such as sliding and slumping. Characteristic
sliding and slumping structures can be identified in the close-ups of the LiDAR images. Both processes, mass movement and slope wash erosion, may have overlapped. Landscape (ii) is the most contrasting one. Dumped stock piles formed elongated, curved and steep ridges. These landforms do not have a natural analogue but clearly show their technological origin. Most interesting are differences in vegetation. South and southwest facing slopes are covered with grassland whereas north and northeast facing slopes are covered with aspen trees. Some of the ditches are filled with water and form small elongated ponds. The characteristic geomorphology of the prairie can be found in landscape (i). Distinct differences are found in properties and types of soils in these four landscapes. Natural soils and pile soils characteristically differ in parent material and soil horizons. No information is gathered yet for the reclaimed soils and the landslides soils due to prohibited access. However, based on what we find at the former Diplomat Mine we can conclude that distribution, development and properties of unreclaimed soils in historical open cast mines in Alberta are primarily controlled by parent material and topography. The geomorphological set-up is dominating the trajectory of vegetation development and post-mining geomorphodynamics. Contrasting slope aspects determine micro climatic conditions and lead to different vegetation types. This has likely had an effect on soil development and soil properties (especially carbon stocks). Further studies will be conducted to quantify these differing soil properties to refine this conceptual model of initial pedogenesis and soil distribution on very young landforms in the prairie landscapes.
Peat mineral soil mix (PMM) and forest floor mineral soil mix (FMM) are cover soils commonly used for land reclamation, while coarse woody debris (CWD) can be added to create structural diversity and provide an additional source of organic matter. However, the effect of cover soil type and CWD on emission rates of greenhouse gases, such as carbon dioxide (CO₂) methane (CH₄) and nitrous oxide (N₂O) in reclaimed oil sands soils has not been studied. Soil respiration, CH₄ uptake and N₂O emission rates were studied in a factorial experiment consisting of 2 cover soils (FMM vs PMM) × 2 sampling distances from the CWD (near vs away from CWD). Greenhouse gas emission rates were measured in July, August, and September 2012 and 2013 using static chambers. Soil respiration rates were greater in FMM than in PMM regardless of the distance from CWD at each sampling time (p < 0.05). Rates ranged from 461 to 1148 and 293 to 677 mg CO2 m⁻²h⁻¹for FMM and PMM, respectively, in 2012, and from 355 to 1318 and 235 to 700 mg CO2 m⁻²h⁻¹, respectively, in 2013. The CWD increased soil respiration by 22–33% in FMM but not in PMM. Soil respiration rates were positively related to microbial biomass carbon (p = 0.004) and nitrogen (p < 0.001). Soil respiration rates decreased from July to September in 2012 and 2013, and were positively related to soil temperature (p < 0.01) but not with soil water content measured at 5 cm depth. Methane uptake rates were greater in FMM (0.026–0.037) than in PMM (0.015–0.028 mg CH₄⁻²h⁻¹. The CWD increased CH4 uptake rates only in July and August 2012 in FMM, and were negatively related to soil water content (p < 0.001) but not to soil temperature. Nitrous oxide emission rates (0.001–0.016 mg N₂O m⁻²h⁻¹) were not affected by either cover soil type or CWD. Global warming potential of CO₂, CH₄ and N₂O effluxes was greater in FMM than in PMM and near CWD than away from CWD, especially in FMM. Our study demonstrates that applying CWD for oil sands reclamation increases organic matter decomposition (increased CO₂ evolution), driven by the effect on microbial populations. Results from this study provide support to findings in earlier studies that CWD application benefits vegetation establishment through enhancing soil processes in reclaimed oil sands lands.