We examined taxonomic composition of fungal communities in Picea abies log bark using next generation sequencing. Three successional stages along gradients of log attributes were identified. In the initial stage, the communities were composed by yeasts, plant pathogens and cosmopolitan saprotrophic fungi with broad substrate utilization. In the intermediate stage, bark was colonized mainly by saprotrophs common in decaying wood, symbionts of epixylic plants and nematode-trapping fungi. The final stage was characterized by the dominance of mycorrhizal fungi. Wood-decaying fungi occurred in all stages. However, their sporadic appearance in bark samples suggests that they are not essential for bark decomposition. Our results provide an insight into the hidden diversity of wood-inhabiting communities – fungal communities, associated with decomposition of bark as a component of coarse woody debris.