Southern Atlantic Coast Dry Oak Forest

This system encompasses oak-dominated forests of somewhat fire-sheltered dry to dry-mesic sites in the Mid-Atlantic and South Atlantic coastal plains from southeastern Virginia to Georgia. Sites where this system occurs are somewhat protected from most natural fires by some combination of steeper topography, isolation from the spread of fire, and limited flammability of the vegetation. If fires were more frequent, the vegetation would likely be replaced by more fire-tolerant southern pines, especially Pinus palustris.

Vegetation consists of forests dominated by combinations of upland oaks, particularly Quercus alba, Quercus falcata, and Quercus stellata. In the northern part of the range, Quercus rubra may be a component, while in the southern part, evergreen species such as Quercus nigra or Quercus hemisphaerica become more prominent. Hickories (Carya spp.) are also prominent, including Carya tomentosa (= Carya alba), Carya glabra, and Carya pallida. Other woody plants may include Tilia americana var. caroliniana, Acer floridanum (= Acer barbatum), Aesculus pavia, Osmanthus americanus var. americanus, Ilex glabra, Ilex opaca, Vaccinium arboreum, Vaccinium elliottii, and Clethra alnifolia. Some typical herbs are Trillium maculatum and Chasmanthium sessiliflorum. There is some variation in composition with aspect and degree of exposure to fire. Pinus echinata may be present in some stands, particularly on drier south- and west-facing slopes but is typically not dominant. 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. More mesophytic species such as Fagus grandifolia and Magnolia grandiflora are absent or are confined to the understory. Analogous systems on the Gulf Coastal Plain have pine as a natural component, and this may be true for some examples of this system as well, where occasional fires may allow them to regenerate. A well-developed shrub layer may be present, with Vaccinium spp. and Gaylussacia spp. most typical. The herb layer is generally sparse, and species richness tends to be low. In examples where fires have occurred, the understory is open and savannalike and dominated by grasses and forbs rather than shrubs.

This system occurs in dry-mesic to dry but not xeric sites, generally on upper to midslopes in bluff systems, but occasionally it occurs on broader uplands or on the highest parts of non-flooded river terraces. Soils are generally acidic, though calcareous soils occur occasionally (as in Carya glabra - Tilia americana var. caroliniana - Acer barbatum / Trillium maculatum Forest (CEGL004747)). Soils are loamy to clayey and well-drained but not excessively drained. Similar sites with coarse sandy soils tend to support other ecological systems, in part due to the influence of more frequent fire. Sites are somewhat protected from most natural fires by steep topography and by limited flammability of the vegetation. Fires that penetrate them are generally low in intensity and have fairly limited ecological effect.

Fire is intermediate in frequency in this system, being less frequent than in adjacent Pinus palustris-dominated stands, and more frequent than in mesic hardwood stands below. This fire regime is an important factor separating it from adjacent Pinus palustris-dominated systems. If fire does penetrate, it is likely to be low in intensity and have somewhat limited ecological effects. However, there is some evidence that this system has expanded into areas once occupied by Pinus palustris as fire has been suppressed (Ware et al. 1993). There may have been a shifting boundary between these systems, driven by variation in fire frequency. These forests probably generally naturally existed as old-growth forests, with canopy dynamics dominated by gap-phase regeneration. However, exposure to occasional fires and hurricanes may create more frequent and larger canopy disturbances than analogous systems inland.

Frequent surface fires occurred on a 5- to 10-year return interval from both lightning and Native American ignitions. These frequent light surface fires would have maintained a grassy understory and kept more fire-tolerant hardwoods and shrubs from capturing the understory and forming a midstory layer. Lightning fires occurred primarily during the spring dry season (April and May) with a secondary peak of Native American and settler burning during the fall (October and November) (Landfire 2007a). Occasionally, during extensive droughts, mixed-severity or stand-replacement fires did occur, especially in drier stand dominated of codominated by Pinus echinata.

Local blowdown winds associated with thunderstorms created gaps on a small but continual basis. More extensive regional disturbances included tropical storms during the growing season and ice storms during winter (in the northern part of the range). Dense stands of middle to older aged pines (where present) were susceptible to periodic mortality from bark beetle epidemics (Landfire 2007a).

Conversion of this type has primarily resulted from removal of the characteristic dominant hardwoods (primarily Quercus species and Carya species) through logging, and the subsequent development of the sites to human uses. This is also the most critical anthropogenic threat. This may result in a stand dominated by wind-blown or bird-dispersed tree species, including Acer rubrum, Celtis spp., Fraxinus americana, Juglans nigra, Juniperus virginiana, Liquidambar styraciflua, Liriodendron tulipifera, Prunus serotina, Robinia pseudoacacia, Sassafras albidum, Ulmus americana, and the exotic Ailanthus altissima. These and other fire-intolerant species persist and increase in the absence of fire (Edwards et al. 2013). Logging which is not carefully done can lead to soil erosion, and then conversion to pine plantation or succession to Pinus taeda, Liquidambar styraciflua, Acer rubrum ruderal forest (Nordman 2013). Patches dominated by Pinus taeda and/or Pinus echinata are artifacts of past disturbance and succession in the absence of fire. These are likely to eventually succumb to drought, fire or insect damage. Another major threat is conversion to human-created land uses, including residential development, industrial development, and infrastructure development. Feral hog (Sus scrofa) activity can eradicate the native ground and shrub flora (Engeman et al. 2007). In addition, invasive exotic species, including Ligustrum sinense, Lonicera japonica, Microstegium vimineum, Pueraria montana var. lobata, Rosa multiflora, and others can become dominant in the ground and shrub layers following canopy disturbance and are threats to the natural species diversity of these habitats (Edwards et al. 2013). The most significant potential climate change effects over the next 50 years include periods of drought, which will affect the health and survival of the canopy trees.

This system ranges from southeastern Virginia (south of the James River) south to southeastern Georgia in the Atlantic Coastal Plain.