Climate change favours specific fungal communities in boreal peatlands

Fungi play a pivotal role in the carbon sequestration potential of boreal peatlands through the process of decomposition. As such, climate-driven changes in the diversity and community composition of peatland fungal communities could have substantial impacts on carbon release from these ecosystems, especially in subsurface peat that represents an important global carbon stock. We used Illumina MiSeq sequencing of rDNA to examine fungal communities after 18 months in intact peatland mesocosms subjected to conditions associated with Canada's future climate, including: warming, elevated atmospheric CO2 and lowered water table. Warming was the main driver of changes in fungal communities across three depths of the peat profile with both Ascomycota- and Basidiomycota-dominated groups becoming more homogenous under warming conditions. Specific changes in fungal functional groups, however, were temperature dependent with potential cellulose decomposers and mycorrhizal root-associated fungi from Basidiomycota dominant under warming of +4 °C, whereas there was a prevalence of potential lignocellulose decomposers and mycorrhizal root-associated fungi from Ascomycota under +8 °C warming. These climate change-induced shifts in the structure of fungal communities in favour of recalcitrant compound decomposers observed across a depth gradient, may reduce long-term carbon storage of boreal peatlands under future climate change scenarios.