Belowground fungal communities in pioneer Scots pine stands growing on heavy metal polluted and non-polluted soils

• Fungal communities in a metal polluted and control site were dominated by ECM fungi.
• Heavy metal pollution induced shifts in fungal community structure but not diversity.
• Shifts in abundance were linked to soil metal pollution and soil mineral composition.
• Initially, dark ECM Ascomycota colonised pine root tips in metal polluted soil.
• Within 2 years, Suillus luteus became the dominant ECM fungus in metal polluted soil.

The impact of soil metal pollution on plant communities has been studied extensively in the past. However, very little is known about the fungal species that co-occur with these plant communities on metal polluted soils. We characterized the belowground fungal community in a heavy metal polluted and a non-polluted soil using 454 pyrosequencing. The fungal communities at both study sites were shown to consist mainly of the same ectomycorrhizal species, but a consistent shift in the relative abundances of these species was observed, whereas no differences in fungal diversity were found. In metal polluted soil, root tips of young pines were initially largely colonized by stress-tolerant dark Ascomycota that were mostly replaced by metal-tolerant Basidiomycota within 2 years. Compared to older forests, a low belowground fungal diversity was observed in the two pioneer stands.