The ridge-snowbed gradient is of high importance in alpine areas in structuring the vegetation cover. However, to what degree belowground fungal communities are affected by the gradient is much poorer understood. In this study, the fungal diversity and community composition associated with roots of the ectomycorrhizal plant Bistorta vivipara were studied along the ridge–snowbed gradient. Fifty root samples were collected in ten plots in an alpine area in central Norway and the fungal communities analyzed by 454 pyrosequencing analyses of tag encoded ITS1 amplicons. A distinct turnover in the fungal communities was found along the ridge-snowbed gradient, paralleled by changes in soil content of carbon, nitrogen and phosphorus. A large proportion (66%) of the detected 801 non-singleton OTUs belonged to Ascomycota, but basidiomycetes dominated quantitatively (i.e. number of reads). Numerous fungal OTUs, many with taxonomic affinity to Sebacinales, Cortinarius and Meliniomyces, showed distinct affinities to either ridge or snowbed plots, indicating habitat specialization. Although a turnover in fungal communities was observed, the diversity remained at the same level along the gradient.
Key words: alpine, Bistorta vivipara, ectomycorrhiza fungal community composition, fungal richness, gradient, ridge and snowbed, root associated fungi, symbiosis