Physiognomy and Structure: No Data Available

Floristics: Composition is usually that of a mixed forest, with overstory codominance by Tsuga canadensis, which is most abundant, and several hardwoods, most frequently Fagus grandifolia, Quercus alba, and/or Quercus montana (= Quercus prinus). Tsuga canadensis, Fagus grandifolia, and Quercus montana are most constant, with Tsuga and Fagus typically having high cover in the understory and shrub, as well as overstory layers. Liriodendron tulipifera, Quercus rubra, Acer rubrum, and Nyssa sylvatica are constant but minor overstory associates. Acer rubrum and Nyssa sylvatica also occur commonly in the understory. Quercus alba and Betula lenta are less constant in the overstory mixtures, but each is important in a subset of stands. True shrubs are often sparse but frequently include Viburnum acerifolium, Kalmia latifolia, Hamamelis virginiana, Rhododendron periclymenoides, and scrambling vines of Smilax rotundifolia. The herb layer is generally sparse to very sparse, but a number of species frequently occur at low cover, including Eurybia divaricata, Polystichum acrostichoides, Medeola virginiana, Dioscorea quaternata, Maianthemum racemosum ssp. racemosum, Thelypteris noveboracensis, Goodyera pubescens, and Carex digitalis. Less constant herbs that are occasionally important include Hexastylis virginica, Epigaea repens, Dryopteris marginalis, Polypodium virginianum, and Dennstaedtia punctilobula. Species richness of 13 plot-sampled stands averaged 31 taxa per 400 m2.

Dynamics:  The restriction of hemlock-hardwood forests to steep, sheltered slopes in the Piedmont and Coastal Plain is likely a function of both a suitably cool microclimate and protection from fire and logging. Such sites have been hypothesized to be Pleistocene refugia, i.e., stations where Tsuga has persisted from a wider distribution in colder climates of the late Wisconsin and early Holocene (Nemeth 1973). However, paleoecological studies indicate that these hemlock communities became established later in the Holocene, when streams probably served as migration corridors for Tsuga as the climate warmed (Prentice et al. 1991). The introduced Asiatic insect hemlock woolly adelgid (Adelges tsugae) is present in most, if not all, contemporary stands of this community. Outbreaks over the past two decades have caused at least some mortality of larger hemlocks in most stands, and some stands have been essentially devastated by the loss of most or all overstory hemlock. Increased sunlight from canopy gaps in these stands appears to have increased shrub densities, and likely contributes to less mesic site conditions, which decreases suitability for hemlock germination and growth. Although individual trees can be treated, there are currently no practical and economical treatments for forest stands.