The Fungal Community of a High-Arctic Semi-Desert Ecosystem Is Robust to Two Decades of Doubled Summer Precipitation but Influenced by Plant Dominance.

In high-arctic semi-desert ecosystems, climate projections suggest a doubling of the current ≤ 250 mm annual precipitation by 2075, increasingly falling as summer rain. This is expected to affect the balance among fungal ecological groups and stimulate decomposition over build-up of soil organic matter. Here, we report the effects of 25 years of artificially doubled summer rainfall combined with nitrogen and phosphorus addition on soil fungal communities and organic matter stocks, in a semi-desert near Zackenberg in NE Greenland entirely dominated by the ectomycorrhizal plant species Salix arctica, Dryas integrifolia and Kobresia myosuroides. Surprisingly, soil fungal biomass and community composition and soil carbon and nitrogen pools were mostly unaffected by the treatments, while the three plant species appeared to cause consistent small-scale variation. The fungal communities were dominated by the ectomycorrhizal genera Cortinarius, Tomentella and Inocybe, but the evergreen Dryas supported a larger abundance of potentially nitrogen-mining Cortinarius species, while the graminoid Kobresia was associated with a larger abundance of saprotrophic or root-invasive Mycena species. Our results suggest that the soil fungal community and linked processes of this high-arctic ecosystem were more robust to two decades of doubled summer rainfall than expected. Long-term changes in belowground fungal communities will likely be mediated by changes in plant communities rather than driven directly by climate change.