Ecological and taxonomic studies of the Russulaceae and other ectomycorrhizal Basidiomycetes in the high-elevation forests of the southern Appalachians

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Virginia Polytechnic Institute and State University

Temperate and boreal fungal floras indicate that species of the Russulaceae (the genera Russula andLactarius) are among the dominant ectomycorrhizal fungi in forest communities. The contribution of the Russulaceae to the communities of ectomycorrhizal Basidiomycetes fruiting in red spruce and adjacent northern hardwood forests in West Virginia was evaluated and compared with other ectomycorrhizal Basidiomycetes occupying the same habitats. The Russulaceae exhibited the greatest species diversity of any family of ectomycorrhizal fungi fruiting in the stands studied (44% of the species in spruce, 39% of the species in hardwoods). Species of Lactarius and Russula were among the most productive in both forests.

Species diversity, productivity, and fruiting phenology of all ectomycorrhizal Basidiomycetes were compared between red spruce and northern hardwood stands for a 3-year period. Sporocarp numbers and sporocarp frequency in 384 four m² quadrats in each forest type was used to estimate productivity. Species richness was greater in hardwoods (36 species) than in spruce (27 species). Nine species were common to both forests. Most productivity was concentrated in a few species, while most species were rare. Species-area curves were constructed for both forests. Fungal species and tree species composition in both forests were compared by principal component analysis.

Fungi in spruce forests were more productive than in hardwood forests. Productivity was highly variable among the three seasons studied because of climatic variability. Sporocarp abundance and frequency were positively correlated with basal area and density of mycorrhizal trees and were negatively correlated with fern cover in hardwood forests. Fruiting seasons extended from early July to late September or early October.

Numbers of species fruiting from the same four m² quadrats ranged from 0 to 7 in spruce forests and 0 to 5 in hardwood forests. Spatial patterns of sporocarps of major species were characterized by the variance-to-mean ratio, mean crowding, patchiness, and spatial autocorrelation and were found to exhibit highly aggregated, contagious patterns. Interspecific associations between pairs of major species were measured by 2 x 2 contingency tables and Cole's index of association.

A taxonomie and geographic survey of Russula and Lactarius in both the quantitative study areas and in similar habitats in the Southern Appalachians was presented.