Plant community development following reclamation of oil sands mine sites in the boreal forest: a review

Understanding how reclamation practices influence plant community assembly and succession is an important step in developing realistic indicators and targets for reclamation of oil sands mine sites to upland forest ecosystems. We currently have a poor understanding of factors affecting plant community assembly and succession in reclaimed oil sands sites. Through synthesis of research completed over the last 24 years, we identify four key findings: (i) use of surface soil and forest floor material salvaged from mined areas increases plant species cover, richness, and diversity relative to the use of various other cover soil materials (such as clay subsoil); (ii) stockpiling of salvaged surface soils decreases the abundance of native plant propagules and delays early vegetation community development; (iii) differences in plant community composition between reclaimed and adjacent mature forests remain two decades after placing cover soils; however, differences are smaller with use of forest floor–mineral mix than peat–mineral mix; and (iv) plant community assembly is in progress but communities remain different to those found in natural undisturbed conditions. Our review identified critical knowledge gaps for further research to improve understanding of: (i) long-term (60 to 100 years) plant community composition in reclaimed oil sands sites; (ii) how residual forest patches near disturbed oil sands sites act as seed and propagule sources in newly reclaimed sites; (iii) plant community assembly processes in reclamation sites; (iv) the effect of micro-topographic heterogeneity on plant community development; and (v) how soil nutrient availability in different substrates influences plant community development over the long term. Ongoing support for selected existing studies and establishment of new studies focusing on plant community development through long-term monitoring are highly recommended.