Quantitation of endorhizal fungi in high Arctic tundra ecosystems through space and time: The value of herbarium archives

Mycorrhizal fungi are widespread in temperate and tropical regions, but generally are thought to be relatively depauperate at high latitudes. The potential impact of global warming on the polar ecosystems has renewed interest in research into tundra soil microbiota. Although logistical impediments limit field access, herbarium accessions are a potential resource for surveying mycorrhizal distribution. We present: (i) a method for examining fungi in roots of herbarium specimens that provides morphological preservation comparable to formalin fixation; and (ii) a multiple quantitation method to assess diverse morphotypes. Arbuscular mycorrhizae, fine endophytes, and septate endophytes were widespread in Asteraceae roots from Axel Heiberg and Ellesmere islands, Arctic Canada, during 2004. Roots from the same species collected from this region since 1982, stored in our herbarium, consistently contained abundant endorhizal fungi. Although 2004 was one of the coolest growing seasons in the survey, mycorrhizal abundance was highest in that year. Endorhizal fungi are likely to be important for plant survival and soil-forming processes in High Arctic tundra environments, and may be sensitive to climate variation.