Surface mining requires the removal of vegetation, soils and overburden which must be reclaimed following mining operations. Reclamation in the Athabasca oil sand mine region involves landform construction, soil placement and native species revegetation that is intended to begin the reestablishment of ecosystem functions that were present prior to disturbance. The importance of ectomycorrhizae, symbioses between plant roots and fungi, to forest reestablishment following reclamation is not well understood. The inclusion of local, undisturbed reference ecosystems and their successional pathways(s) is one way to evaluate the importance of ectomycorrhizae on early forest development following reclamation. Toward this goal, we compared the community assembly of ectomycorrhizal fungi in reclaimed and a range of reference ecosystems. Reclaimed sites had three salvaged and directly placed cover soil types: forest floor material, peat, and subsoil material. Reference ecosystems included: 1) mature jack pine (Pinus banksiana) forest with forest floor intact, 2) jack pine forest where trees were removed and forest floor was left intact, and 3) jack pine forest where both trees and forest floor were removed. In May 2012, seedlings of three host species (Populus tremuloides, Pinus banksiana, and Picea glauca) were planted in all sites to assay soils for ectomycorrhizal fungi in reclaimed and reference ecosystems. Subsets of these seedlings were harvested in August 2013 and 2015, and fungi colonizing roots were identified using molecular techniques.
Results/Conclusions
Two years after planting, communities of ectomycorrhizal fungi colonizing seedlings on reclaimed sites differed from those in mature jack pine forest with forest floor intact. Four years after planting, fungal communities on seedlings assaying soils diverged across the reclaimed ecosystems. Fungal communities assayed in reconstructed soils of the reclaimed sites also fell on trajectories unique from those observed at the reference ecosystems. Four years following the afforestation of reclaimed sites, the ectomycorrhizal community not only differed across soil types, but also varied greatly from the other reference ecosystems.