Leacock, P.R. 1997. Diversity of ectomycorrhizal fungi in Minnesota's ancient and younger stands of red pine and northern hardwood-conifer forests. Ph.D. Dissertation, University of Minnesota. 96 pp.
Remnant ancient forests were investigated to examine the magnitude of the ectomycorrhizal fungal communities, integral components of forest ecosystems. Quantitative data were obtained for these fungi in red pine and northern hardwood-conifer forests in northern Minnesota, using dispersed, circular, 4-m2 sampling areas along permanent transects in half hectare plots. Basal areas of woody plants were measured for the plots, and soil organic matter and pH were determined. Diversity, species frequencies, and fruitbody densities were examined in ancient and younger stands. The red pine forest, with a major conifer component, harbored a larger community of ectomycorrhizal fungi with two to three times more species, and abundance an order of magnitude greater than that observed for northern hardwood-conifer forest. Differences were found in species composition between the two age classes. Some species characterized old-growth and others, mature red pine forest. Russulaceae were major components in, and included the most abundant taxon of each forest: Russula silvicola for red pine forest, and Lactarius thejogalus for northern hardwood-conifer forest. Laccaria laccata, the second most frequent species, had higher densities in old-growth stands of both forest types. Cortinarius was a dominant genus in the red pine forest with an unknown number of species. By comparison all but a few northern hardwood conifer forest species were infrequent or rare, and a smaller percentage of species were shared among plots. Even though frequency and diversity were similar or less than in younger forest, old-growth stands of both forest types had greater total fruitbody density: 1.1 times greater for red pine and a significant 1.8 times greater for northern hardwood-conifer forest. Greater productivity in these two old-growth forests may be an important factor in ecosystem function. The hypothesis that fungal diversity declines with advanced forest age is not supported by the findings of this study where species diversity and abundance are maintained in these oldgrowth stands.