The observed abundance of ectomycorrhizal fungi (EMF) species on root tips of four tree species populating the forest plot near Basel, Switzerland (Picea abies (Pa), Pinus sylvestris (Ps), Larix decidua (Ld) and Fagus sylvatica (Fs); n = 3). (a) Bar colours indicate the tree species from which the roots originated (only top 30 OTUs are displayed). Asterisks denote EMF associations with all four tree species. (b) Proportion of root tips associated with EMF species found on one, two, three, or four different host tree species. (c) Schematic presentation of the distribution of the four tree species in the mixed forest plot