Southern Atlantic Coast Moist Hardwood Forest

This upland system of the Atlantic Coastal Plain ranges from Delaware south to interior Georgia in a variety of moist but non-wetland sites that are naturally sheltered from frequent fire. Such sites include lower slopes and bluffs along streams and rivers in dissected terrain, mesic flats between drier pine-dominated uplands and floodplains, and local topographic high areas within bottomland terraces or nonriverine wet flats. Soil textures are variable in both texture and pH. The vegetation consists of forests dominated by combinations of trees that include a significant component of mesophytic deciduous hardwood species, such as Fagus grandifolia or Acer floridanum. Its southern limit is generally exclusive of the natural range of Pinus glabra and Magnolia grandiflora. Upland and bottomland oaks at the mid range of moisture tolerance are usually also present, particularly Quercus alba, but sometimes also Quercus pagoda, Quercus falcata, Quercus michauxii, Quercus shumardii, or Quercus nigra. Pinus taeda is sometimes present, but it is unclear if it is a natural component or has entered only as a result of past cutting. Analogous systems on the Gulf Coastal Plain have pine as a natural component, and this may be true for some examples of this system. Understories are usually well-developed. Shrub and herb layers may be sparse or moderately dense. Within its range, Sabal minor may be a prominent shrub. Species richness may be fairly high in basic sites but is fairly low otherwise.

Stands of this system include a significant component of mesophytic species such as Fagus grandifolia or Acer floridanum (= Acer barbatum). Upland and bottomland oaks at the mid range of moisture tolerance are usually also present, particularly Quercus alba, but sometimes also Quercus falcata, Quercus michauxii, Quercus shumardii, or Quercus nigra. Other hardwood components include Liriodendron tulipifera, Liquidambar styraciflua, Carya cordiformis, Nyssa sylvatica, and Magnolia tripetala. Pinus taeda is sometimes present, but it is unclear if it is a natural component or has entered only as a result of past removal of the hardwood canopy and subsequent invasion. Analogous systems on the Gulf Coastal Plain have pine as a natural component, and this may be true for some examples of this system. Understories are usually well-developed. Shrub and herb layers may be sparse or moderately dense, with the herb layer being forb-dominated. Some typical smaller trees and shrubs include Cornus florida, Symplocos tinctoria, Oxydendrum arboreum, Hamamelis virginiana, Morus rubra, and Stewartia malacodendron. Within its range, Sabal minor may be a prominent shrub. Some stands may contain Arundinaria gigantea. Some typical herbs include Mitchella repens and Hexastylis arifolia. Species richness may be fairly high in basic sites but is fairly low otherwise.

This system occurs in a variety of moist non-wetland sites that are naturally sheltered from frequent fire. The distribution of these forests is determined by the interaction of local topography and soil texture. Most common are lower slope and bluff examples along streams and rivers in dissected terrain, but some examples occur on mesic flats between drier pine-dominated uplands and floodplains or on local high areas within bottomland terraces or nonriverine wet flats. Soils cover the full range of mineral soil textures, except the coarsest sands. Richer and more mesic stands occur in more strongly concave and finer-textured areas. Soils are not saturated for any significant time during the growing season and seldom, if ever, are extremely dry. Soils developed from calcareous materials or rich alluvium may be basic; others are strongly acidic. Sites are protected from most natural fires by steep topography or by surrounding extensive areas of non-flammable vegetation (Batista and Platt 1997).

Fire is naturally infrequent to absent in this system. Sites are protected from most natural fires by steep topography or by surrounding extensive areas of non-flammable vegetation (Landfire 2007a). If fire does penetrate, it is likely to be low in intensity but may have significant ecological effects. These forests probably generally exist naturally as old-growth forests, with canopy dynamics dominated by gap-phase regeneration. However, exposure to occasional fires and severe storms may create more frequent and larger canopy disturbances than analogous systems inland. Storm-related disturbance can be followed by waves of tree recruitment, growth, and death resulting in changes in the density and structure of tree populations and in consequent fluctuations in forest species composition. Disturbances in these forests appear to be critical for both regeneration and change in older stands (Batista and Platt 1997). Periodic droughts will cause death of or stress to moisture-requiring canopy trees.

Conversion of this type has primarily resulted from repeated canopy removal through logging, which is also the most critical anthropogenic threat. These sites were historically less frequently logged than the adjacent pine-dominated uplands, with more desirable species being removed in preference to Fagus grandifolia, which is less desirable in the lumber trade. In addition, some mesic hardwood forests in more moderately dissected terrain have been converted to pine plantations or impacted (destroyed or fragmented) by agriculture. Bluff habitats are often prime sites for development, especially along major rivers. Complete devastation by natural agents was probably very rare in this forest type (Batista and Platt 1997). These forests also suffer the effects of ozone and acidic atmospheric deposition.

Aside from actual site conversion, feral hogs (Sus scrofa) represent one of the greatest threats to biodiversity in these forests (Engeman et al. 2007). They can be especially difficult to control in sensitive slope forests (Edwards et al. 2013). In addition, invasive exotic species including Lygodium japonicum, Lonicera japonica, and Ligustrum sinense can become dominant in the ground and shrub layers following canopy disturbance (Edwards et al. 2013). For mesic hardwood forests containing Fraxinus species or Persea borbonia, emerald ash borer (recently found in Georgia) and laurel wilt (spread by a non-native ambrosia beetle) may also be significant stressors, respectively.

The most significant potential climate change effects over the next 50 years include periods of drought, which has affected parts of the coastal plain. Droughts will affect the health and survival of the moisture-requiring trees, as well as increase the probability of damaging wildfire.

This system ranges from Delaware south to central Georgia in the Atlantic Coastal Plain. Its southern limit is generally exclusive of the natural range of Pinus glabra as mapped by Kossuth and Michael (1990) and Magnolia grandiflora as mapped by Outcalt (1990).