Snow fungi as a food source for micro-arthropods

Snow fungi are often visibly abundant on tundra and forest understory vegetation immediately after snow melt in Nordic regions. Fungal hyphae are a common food source for many terrestrial arthropods and snow fungi could therefore be a potentially important component of an as of yet unexplored winter food web. We compared the abundance of soil arthropods (Acari and Collembola) from paired patches with and without dense infections of snow fungi in the forest understory of a northern Swedish boreal forest after snow melt. Although we did not find increased abundance of these animals when snow fungi were present, Collembola and Acari were sustained on a diet of snow fungi for six months. The isotope signature of the snow fungi clearly differed from humus and other fungal types from literature values obtained from similar boreal forests, suggesting that these fungi may occupy a novel N niche during winter in northern boreal forests. Our study shows for the first time that snow fungi are a potential food source for micro-arthropods during winter and spring. Potentially, snow fungi may represent the basis of an unexplored sub-nivean winter food web but further work is required to assess their importance for community development and winter litter decomposition.