Fungi associated with tree species at an Alberta oil sands reclamation area, as determined by sporocarp assessments and high-throughput DNA sequencing

Abstract Gateway Hill is a 104-ha area in the oil sands region of Alberta, which was operationally reclaimed and reforested in the late 1980s and certified as reclaimed in 2007/08. In 2014, ∼30 years after reclamation was completed, we began studies with the main objective to determine the soil fungi present at the site. Sporocarp surveys in 2014 and 2016 were used to supplement metagenomic analyses of soil fungi in jack pine (Pinus banksiana), white spruce (Picea glauca), and Siberian larch (Larix sibirica) stands. Fungal internal transcribed spacer amplicons of DNA extracted from forest floor, root, and fine soil fractions were sequenced using Roche 454 pyrosequencing in 2014. Coarse soil reclamation samples and soil samples from a nearby unmined spruce stand were sequenced with Illumina in 2016. Sequenced community assemblages were first assessed using unconstrained multivariate analyses, and then using (partially) constrained ordination techniques to directly account for the effects of tree species and other confounding factors. Based on soil DNA analyses the relative abundance of ectomycorrhizal taxa was greater in spruce stands, saprotrophs were more abundant in pine stands, and pathogens were more abundant in larch stands. Associations of fungal taxa, mostly saprotrophs and ectomycorrhizae, with tree species were especially prominent in root fractions. The sporocarp survey found sporcarp abundance was greatest in pine stands and they tended to have more ectomycorrhizal taxa and spruce and larch stands more saprotrophic taxa. The effects of tree species on fungal taxa differed between the sporocarp surveys and soil DNA analyses: many of the fungi identified by sporocarp presence were not detected by soil DNA sequencing, whereas the latter method detected many more species in all trophic groups. Both DNA sequencing methods showed that many operational taxonomic units were preferentially associated with either spruce or pine stands. Though not definitive, preliminary examination of soil fungi using the Illumina platform showed that a natural spruce stand at the base of Gateway Hill had greater species richness than did reclaimed spruce stands. The results of this study show that communities of soil fungi have become established since the initiation of reclamation. Further work is underway to compare this reclamation site to other unmined forest sites.