Ectomycorrhizal fungal hyphae communities vary more along a pH and nitrogen gradient than between decayed wood and mineral soil microsites

Ectomycorrhizal (ECM) fungal community composition is structured by soil properties, but specialization for woody microsites by ECM fungi is equivocal. Because fungal mycelia explore the substrate and colonize nutrient patches, studies targeting ECM fungal hyphae may reveal niche preferences. Moreover, studying the distribution and composition of ECM fungal hyphal communities contributes to our understanding of nutrient cycling in forest soils. We used next-generation sequencing to determine whether the composition of forest floor fungal communities present as hyphae differed among three microsite types: decayed wood, mineral soil adjacent to intact logs, or control mineral soil of mature spruce forests in British Columbia. The microsites were located in three blocks that were separated by 1 km and varied in elevation. Across the site, the ECM fungal lineage /amphinema-tylospora was the most operational taxonomic unit (OTU)-rich group, while the saprotrophic order Mortierellales was also dominant. ECM fungal species differed among microsites. For example, ECM fungal OTUs identified as Tylospora fibrillosa and Russula curtipes were more frequent in decayed wood as compared with control mineral soil. However, ECM fungal communities were more strongly structured by block characteristics, and we conclude there is no distinct group of ECM fungi specializing in the soil microsites examined in this forest.