Ectomycorrhizal fungi were investigated on five different forest tree species growing in pure stands on the south slope of the Taunus Mountains, which are situated at the northern end of the Rhine rift valley in Central Germany. Mycorrhizal fungi accompanying the genus Xerocomus were identified and their frequencies counted. Using ITS markers, 22 different fungal species were identified down to species level and 6 down to genus level. On European beech (Fagus sylvatica) 16 fungal species and 4 genera were identified and on Sessile oak (Quercus petraea) 16 ectomycorrhizal species and 2 genera were determined. On both deciduous trees we observed exclusively: Cortinarius subsertipes, Genea hispidula, Lactarius quietus, Tylopilus felleus and a Melanogaster genus. On Norway spruce (Picea abies) we identified 13 different mycorrhizal species and 3 different genera, on Silver fir (Abies alba) 12 species and 3 genera, and in association with European larch (Larix decidua) 11 species and 3 genera. On these conifers Cortinarius anomalus, Lactarius necator and a Piloderma genus occurred exclusively. Comparisons with published data of ectomycorrhizal diversity on the same five tree species, growing in different areas of Germany and Europe, led to the conclusion that there is relative site specificity for ectomycorrhizal communities. Upper soil compartments of the stands investigated in the Taunus Mountainssuffer from soil acidification (pH-H₂0 ~3.7 to ~4.8). However, a clear correlation between upper soil pH-values and fungal diversity was not observed. On the other hand, nitrate concentrations in upper soil compartments (~26 to ~91 kgNO₃^-/ha) were higher in older stands as compared to younger ones. Higher nitrate concentrations in upper soils correlated with lower numbers of mycorrhizal individuals.