Sorbus Sorbus Sorbus is a genus of about 100–200 species of trees and shrubs in the rose family, Rosaceae. Species of "Sorbus" ("s.l.") are commonly known as whitebeam, rowan, service tree, and mountain-ash. The exact number of species is disputed depending on the circumscription of the genus, and also due to the number of apomictic microspecies, which some treat as distinct species, but others group in a smaller number of variable species. Recent treatments treat "Sorbus" in a narrower sense to include only the pinnate leaved species of subgenus "Sorbus", raising several of the other subgenera to generic rank. "Sorbus" is
North Fork Mountain pine barren in the Central Appalachians. Other rocky summits, including the summit of Pike Knob, are blanketed by red pine ("Pinus resinosa") forests, here at their southernmost natural occurrences. The Monongahela National Forest has designated of old growth red pine forest on the mountain as the North Fork Mountain Red Pine Botanical Area. Another unusual vegetation type on North Fork Mountain is an elfin forest dominated by yellow birch ("Betula alleghaniensis"), mountain ash ("Sorbus americana"), and mountain holly. The oak-and-pine vegetation of North Fork Mountain contrasts strongly with the more diverse vegetation of the nearby mountains just west of the