Stable isotope probing of fungi in the rhizosphere of Betula nana

Mycorrhizal networks can be pathways for the transfer of nutrients among plants in nature, but to date, no study has unambiguously identified the fungi involved in situ. We applied a 13C-CO2 pulse-chase labelling experiment of Betula nana followed by the stable isotope probing (SIP) of rhizosphere fungal DNA to identify the fungi involved in the transfer of 13C among conspecific pairs of Betula nana plants in Arctic tundra. We found that Cortinarius collinitus was unique among rhizosphere fungi in being highly enriched in the 13C-SIP-DNA fractions. Our data suggest that Cortinarius collinitus may facilitate shrub spread into Arctic tundra acting as a belowground pathway for the rapid reallocation of resources among plants.