Eastern Hemlock - Hardwood Forests Forests of this group are (or were) characterized by the dominance or co-dominance of eastern hemlock (Tsuga canadensis) in nearly every vertical stratum. Similar forests are known from the Great Lakes region and the northeastern United States and range as far south as the southern Blue Ridge of North Carolina and Tennessee. In Virginia, stands occupy mesic, sheltered habitats in the northern half of the mountains, as well as isolated, north-facing river bluffs and ravines throughout much of the Piedmont. Rare, marginal stands have also been found on bluffs of the extreme inner Coastal Plain in Fairfax, Prince William, and Hanover counties. A number of tree associates, especially sweet and yellow birches (Betula lenta var. lenta and Betula alleghaniensis), northern red and chestnut oaks (Quercus rubra) and (Quercus montana), and eastern white pine (Pinus strobus), usually contribute to mixed overstories, but the total cover of overstory and understory hemlock in these forests usually exceeds that of any other species. In the Piedmont, where hemlock forests may intergrade with Mesic Mixed Hardwood forests, American beech (Fagus grandifolia) and white oak (Quercus alba) are frequent associates. Understories vary from sparse to moderately dense; some stands have ericaceous shrub layers dominated by mountain laurel (Kalmia latifolia) or Catawba rhododendron (Rhododendron catawbiense). Herbs are typically very sparse, but rare stands on basic or calcareous substrates have more diverse lower strata.
Eastern Hemlock - Hardwood Forests are closely related to Acidic Cove Forests but generally have a less diverse composition of woody species, a greater dominance of hemlock in all strata, and considerably lower species richness. Several notable old-growth hemlock forests occur in Virginia, including a stand in the Skidmore Fork drainage on Shenandoah Mountain (Rockingham County) and The Limberlost in Shenandoah National Park (Madison County). All eastern hemlock forests in Virginia are now highly threatened by the hemlock woolly adelgid (Adelges tsugae), an introduced insect that has caused extensive mortality in many, if not most stands. Stands that have lost most of their hemlock appear to be succeeding into different types - primarily northern hardwoods and acidic cove forests in the mountains, and mesic mixed hardwoods in the Piedmont.
References: Coulling (1999), Fleming (2002a), Fleming (2002b), Fleming et al. (2007), Harrison et al. (1989), Nemeth (1973), Rawinski et al. (1994), Rawinski et al. (1996).
Three community types have been classified through analysis of data from 37 plots (Fig. 1) that were included in several large-scale regional classification projects. However, more plot data is needed from a wider geographic sample of this group. Additionally, there is considerable urgency to complete the needed data collection as intact stands of this group become fewer each year because of the hemlock woolly adelgid. Click on any highlighted CEGL code below to view the global USNVC description provided by NatureServe Explorer.