Macrofungi associated both with Alnus viridis and A. incana were investigated by Favre (1960) and reported in his study on the subalpine and montane fungus flora of the Swiss National Park (SNP) and its adjacent regions. In the above publication most mycoecological data presented by Favre, such as collecting dates for all records, are unfortunately not readily accessible to the reader or are absent. Therefore, in this present mycoecological analysis both published and unpublished data (kept in G) have been taken into account and, if feasible, added.
During a period of 17 years, Favre made 76 excursions (mostly during August and September) to seven stands of A. incana and 15 stands of A. viridis. The sites he explored are located in six regions (Zernez, S-chanf, Susch, Scuol, S-charl, Pass dal Fuorn) either within the SNP or close to its borders. The areas investigated best are those of S-charl (including 19 excursions to a small topographically defined stand of A. viridis in the subalpine zone of Val Sesvenna) and S-chanf. By comparison Favre has been visiting locations with A. viridis about four times more often than those with A. incana, and hence a clear correlation can be demonstrated between the number of visits and the number of agarics gathered on either habitats. In locations with A. incana about 67 species of macrofungi have been recorded whereas stands dominated by A. viridis yielded about 138 different taxa.
The total number of macrofungi either associated as symbionts or saprobes on detritus of the two species of Alnus found in the study area was about 157. Beside Alpova diplophloeus, the most common group of fungi are the Agaricales with 17 ectomycorrhizal representatives exclusively found in association with alders. Accordingly the most dominant and constant ectomycorrhizal macrofungi of A. viridis are Lactarius obscuratus, Naucoria luteolofibrillosa, and N. scolecina. The most frequently gathered saprobic macrofungi of A. viridis are Rutstroemia firma, Mycena citrinomarginata, M. galopoda, Clitocybe alnetorum, and Pseudobaeospora pillodii. Relying upon Favre's data, however, Naucoria escharoides is the only dominant and most consistently ectomycorrhizal agaric associated with A. incana.
A comparison of species lists reported from additional alder forests in Central Europe revealed that in the SNP region about nine ectomycorrhizal fungi (including Russula alnetorum, Lactarius obscuratus, and Cortinarius atropusillus) must be considered as being exclusively associated with A. viridis. In contrast, Paxillus filamentosus is the only agaric entering ectomycorrhizal symbiosis with the more common and much wider distributed A. incana, which in the SNP region is restricted to the montane zone.