The History and Status of the Hemlock-Hardwood Forests of the Allegheny Plateau

(...) Before settlement, Fagus grandifolia (beech) and Tsuga canadensis (hemlock) dominated the moister segments of the Plateau. Outliers of the more southern Appalachian oak forest occupied the more xerophytic sites, e.g. upper slopes, stonier soils, and soils with a fragipan. The disturbance regime of the pre-settlement period, creating small canopy gaps, favoured the ascendancy of the slower growing shade-tolerant beech and hemlock in the understorey and eventually the overstorey. (...)