Natural Recovery of Vegetation on Reclamation Stockpiles After 26 to 34 Years

ABSTRACT Stockpiling of soils is essential for reclamation after oil sands mining, and can influence revegetation through degradation of seed viability and soil quality. Three peat-mineral stockpiled areas in upland boreal forest, aged 26 to 34 years, were assessed for effects on soil, vegetation, and successional status to study the natural recovery of vegetation. Six upland (five native, one nonnative) and one lowland native species community types were identified where non-vascular had more communities than vascular plants. Upland boreal species that were likely not present in the soil seed bank, colonized the sites relatively quickly with a plant community of early to mid successionals, including persistence of a lowland species (Amblystegium serpens) and nonnatives. Presence of a non-native community (Melilotus officinalis) 26 to 34 years after reclamation can be concerning. Stockpiled soil texture (clay) and tall shrub stem density were most influential on plant community development. Stem density (DBH > 5 cm), self-thinning of early successional species (Salix, Betula papyrifera), and presence of climax species (Picea glauca) resembled the successional trend of natural boreal forests in the region. Results from this study suggest natural recovery of upland boreal forest on lowland peat substrate is possible and can support evolving plant communities.