Frequency and diversity of ectomycorrhizal and saprophytic macrofungi in the Laurentide Mountains of Quebec

Abstract

Total macro fungus frequency in closed forest associations of the Laurentide Mountains varied little (147 – 185 %) from one to another. The macrofungal flora of the deciduous forest was composed mainly of many infrequent species, whereas coniferous forests had few, but very frequent, macrofungi. Total frequency was significantly lower (15%) in open stands of the spruce–cladina association. Species richness decreased gradually (from 125 to 34 species) towards the north and with increasing altitude. Both the Simpson and the Shannon–Wiener diversity indices were significantly lower in the coniferous forest when compared with the deciduous forest. This decrease in diversity was due to the scarcity of saprophytic fungi in mor humus, whereas the number of ectomycorrhizal species remained constant. The diversity of saprophytic fungi was related significantly to that of vascular plants, whereas the diversity of ectomycorrhizal macrofungi was related mainly to the percent cover of ectomycorrhizal hosts. A total of 195 species of macrofungi were recorded for the study sites. In the maple – yellow birch forest, most of the macrofungi were saprophytic members of the Tricholomataceae, Hygrophoraceae, Strophariaceae, and Clavariaceae, many being exclusive in this association. However, each biological group had approximately equal frequency (44–54%) and richness (37–45 taxa). Species composition of the coniferous forest differed from the former in the clear dominance of ectomycorrhizal macrofungi from the Cortinariaceae, Russulaceae, and the Boletaceae. In the black spruce – cladina association, saprophytic fungi were scarce and ectomycorrhizal species were also relatively infrequent. In all the sites, the equitability of macrofungal frequency was high, as seen by the high proportion of rare species. The decline in species richness observed in this study, when moving from deciduous to coniferous forests, corresponds well with the increase in environmental rigor and instability, as well as the decrease in the diversity of organic substrate and species of vascular plants.