Ectomycorrhizal community structure under willows at former ore mining sites

The goat willow (Salix caprea) belongs to the typical pioneer vegetation at former ore mining sites in Middle Europe as a result of its high metal-tolerance. Ectomycorrhizal (EM) fungi are known to contribute essentially to the tolerance of plants against abiotic stress. We investigated the EM associations of S. caprea at three former silver-mining sites around Freiberg (Saxonia, Germany) after 33 years of revegetation. The EM colonisation ranged from 3 to 36% of the fine root tips. We found 14 different EM types and characterised them morphologically as well as anatomically. The fungal partners were identified using LSU and ITS sequences. They belonged to four families: Thelephoraceae, Cortinariaceae, Tricholomataceae and Tuberaceae. Thelephoraceae, with 53–91%, comprised the largest portion of the total EM colonisation at all test sites and sampling dates. Thelephoraceae produced mainly contact exploration types of ectomycorrhiza. Tricholoma cingulatum was the only EM fungus which was found as ectomycorrhiza and sporocarp. We suppose that the low exploration of the majority of EM associations of S. caprea, in combination with high portions of metal-chelating organic acids containing fungal partners, contributes essentially to the high tolerance of this tree species against high metal concentrations in the soil.