In this study we report on changes in the belowground ectomycorrhizal fungal communities in southern Swedish coniferous forests as a consequence of liming with 3-7 ton limestone per hectare 16 years prior to the study.

A total of 107 ectomycorrhizal fungi were identified from 969 independently sampled root tips by sequencing the internal transcribed spacer region of the ribosomal DNA. Forty, 59 and 51 species were identified in three pine and spruce forests. Within all sites only about 25% of the species overlapped between the limed and the reference areas. However, the most abundant species were often found in both limed and reference plots and 60-70% of the root tips at each site were colonised by species occurring in both limed and reference plots.

Across all three sites, fungal species belonging to the genus Tylospora and the order Pezizales became significantly more frequent in limed plots, while species belonging to the genera Russula and Lactarius decreased in frequency. At individual sites, several species within the genera Amphinema, Piloderma, Inocybe and Hygrophorus were also significantly influenced by liming. We estimate that, at the root tip level, about 30% of the roots were colonised by a different fungal species as a consequence of liming. The observed shift in ectomycorrhizal fungal communities was related to an increased pH and base saturation with liming.

We conclude that even a moderate level of liming have long lasting effects on belowground ectomycorrhizal community composition. We discuss the observed community changes in relation to ectomycorrhizal functionality and biodiversity in limed forests.