Community composition of root‐associated fungi in a <i><scp>Q</scp>uercus</i>‐dominated temperate forest: “codominance” of mycorrhizal and root‐endophytic fungi

Abstract In terrestrial ecosystems, plant roots are colonized by various clades of mycorrhizal and endophytic fungi. Focused on the root systems of an oak‐dominated temperate forest in J apan, we used 454 pyrosequencing to explore how phylogenetically diverse fungi constitute an ecological community of multiple ecotypes. In total, 345 operational taxonomic units ( OTU s) of fungi were found from 159 terminal‐root samples from 12 plant species occurring in the forest. Due to the dominance of an oak species ( Q uercus serrata ), diverse ectomycorrhizal clades such as R ussula , L actarius , C ortinarius , T omentella , A manita , B oletus , and C enococcum were observed. Unexpectedly, the root‐associated fungal community was dominated by root‐endophytic ascomycetes in H elotiales, C haetothyriales, and R hytismatales. Overall, 55.3% of root samples were colonized by both the commonly observed ascomycetes and ectomycorrhizal fungi; 75.0% of the root samples of the dominant Q . serrata were so cocolonized. Overall, this study revealed that root‐associated fungal communities of oak‐dominated temperate forests were dominated not only by ectomycorrhizal fungi but also by diverse root endophytes and that potential ecological interactions between the two ecotypes may be important to understand the complex assembly processes of belowground fungal communities.