A total of 130 wood-rotting species of the Aphyllophorales were collected from the spruce-fir forest of the southern Appalachian Mountains. They represented 66 genera in 11 families. There are 15 common to numerous species which actively decompose wood substrates and apparently play an important role in the ecology of the spruce—fir forest of the research area.
Trichaptum fusco—viglaceum constantly occurs where dead firs and spruces are standing or lying. Likewise, Amylostereum chailletii, Fomitopsis pinicgla, Grandinia breviseta, and Phellinus chrysoloma are frequent or abundant and dominant throughout the research area. Antrodia serialis, Ganoderma applanatum, Grandinia alutaria, Phellinus laevigatus, Stereum hirsutum, and Trichaptum abietinum commonly occur at somewhat disturbed sites of the forest. Besides them, Botryobasidium vagum, Coniophora arida, Inonotus radiatus, and Phellinus igniarius are commonly distributed in this research area.
In terms of fungal occurrence, the spruce-fir forest of the research area consists of several forest site types. Fungi usually occur when the forest site is disturbed to a certain degree. Naturally disturbed areas (Type III) where frequent windbreaks and windthrows occur provide ideal fungal habitats and supply adequate substrates and moisture for fungal growth. More than three fourths of the fungi counted occurred in this type of forest site. On the other hand, extreme disturbance or impact discourages fungal growth. Where the trees defoliate and the canopy is widely opened (Type IV), the forest floor dries up and fungal occurrence becomes quite reduced. Corticioid fungi are mostly restricted to Type III except when they are able to utilize moisture in Type IV.
Many polyporoid and stereoid fungi grow on both bark and wood. The bark layer supports their fruitbodies and secures mycelial activity inside. When dead trees release or shed bark, corticioid fungi usually colonize the decayed wood and bark remains. They fruit when moisture is stored in substrates and dry up with the desiccation of substrates. Broken or cut wood (= butt) creates a unique habitat as the substrate and the decay are exposed. Some common polyporoid or stereoid fungi colonize this habitat.
About half of the fungi collected occur on bark and the other half on wood, while 27 species of the fungi classified occur on bark and 31 species on wood. Other 68 species occur on bark and wood. The frequency of fungal occurrence is almost same on both bark and wood, but species diversity seems to be more or less greater on wood as decayed and decorticated dead trees newly accommodate corticioid fungi.
On recently dead trees with fresh substrate, Trichaptum, émylostereum, Stereum, and Gloeophyllum constantly occur (Baxter, 1948; Stillwell, 1959). Fomitopsis and Phellinus occur on fresh to somewhat decomposed substrates, but Perenniporia ellipsospora exceptionally occurs on much decomposed substrates. Grandinia breviseta, G. alutaria, and G. Eimosissima have broad ranges of wood rot and play a significant role in decomposition of wood and bark remains (Eriksson and Ryvarden, 1976). But many corticioid fungi are confined to strongly decomposed substrates. When the fungi are grouped according to the type of wood rot, only about 10 species are believed to produce brown rot.
In the spruce-fir forest of the research area, red spruce and Fraser fir are the most important hosts, and more than two thirds of the fungi counted occur on these trees. Egmitopsi§,_ghellinus, and Berenniporia may cause heart rot or butt rot and weaken these trees (Hepting, 1971). Yellow birch and American beech are the most common hardwoods in the research area. Phellinus and Ganoderma may cause trunk rot on them (Hepting, 1971).
Elevational variation of fungi within the research area is related to the distribution of their host trees. Common to abundant species usually occupy a broad range of elevation. Fungal distribution depends on tree type, like conifer or hardwood, rather than individual tree species. The fungal flora of the spruce-fir forest is believed to be rather different from that of hardwood forests at low elevation.