Central Atlantic Coastal Maritime Forest

This system encompasses most woody vegetation of Atlantic Coast barrier islands and similar coastal strands, from Virginia Beach to central South Carolina (south approximately to the Cooper River where the true Sea Islands begin). It includes forests and shrublands whose structure and composition are influenced by salt spray, extreme disturbance events, and the distinctive climate of the immediate coast. Many examples of this system will include a component of Quercus virginiana or Morella cerifera. Also included are embedded freshwater depressional wetlands dominated by shrubs or small trees, such as Cornus foemina, Persea palustris, or Salix caroliniana. This system may experience less effects from fire than the equivalent Southern Atlantic Coastal Plain Maritime Forest (CES203.537).

Vegetation includes shrublands and forests. Shrubland dominated by salt-tolerant shrubs such as Morella cerifera and Ilex vomitoria or by stunted trees often occurs on the seaward edge where salt spray is heavier. Forests are typically dominated by a small set of salt-tolerant evergreen trees, mainly Quercus virginiana, Quercus hemisphaerica, Pinus taeda, and in the southern portions, Sabal palmetto. Rare forested wetlands are dominated by a variety of wetland tree species, including Acer rubrum, Nyssa biflora, and Taxodium distichum. A few of the most sheltered areas near the northern end of the range have forests with deciduous species such as Fagus grandifolia and Quercus falcata. Also included are embedded freshwater depressional wetlands dominated by shrubs or small trees, such as Cornus foemina, Persea palustris, or Salix caroliniana. Communities tend to be low in species richness, with all strata limited to a set of salt-tolerant species.

This system occurs on barrier islands and on coastal strands where barrier islands are lacking, and is seldom or never found more than 2 or 3 miles from the ocean. Chronic salt spray is an important influence on vegetation structure and composition; however, the extent to which plant communities found in this system are shaped by salt spray varies. Examples closest to the coast are most likely to exhibit classic streamlined canopy shape due to spray sculpting and are less likely to support salt-intolerant plant species. Heavier salt spray often determines the boundary of this system with Southern Atlantic Coastal Plain Dune and Maritime Grassland (CES203.273). Maritime forest requires some shelter from the ocean, in the form of high dunes or extensive sand flats, in order to develop. This system may occur from the top of interior dunes to wet swales. Soils are sandy, except for mucks in the wettest swamps. Soils range from excessively drained to permanently saturated. They are presumably low in nutrient-holding capacity, but input of nutrients in salt spray probably makes this system fairly fertile. Topography and apparent moisture may vary widely with little change in vegetation. The ocean's moderation of climate may be a significant factor in the character of this system. A number of plant species extend much farther north in the maritime forests than they do even a few miles inland.

Maritime forests occur in the most stable portions of barrier islands, but the maritime environment is still extremely dynamic. Wind events and hurricanes will have significant impacts on this system. The environment for these forests may be severely altered or destroyed by geologic processes, such as the slow movement of dunes or their catastrophic destruction by storms. Sand movement may also create new sites for this system to occupy. Chronic salt spray and intense salt spray during storms are important influences on vegetation structure and composition; however, the extent to which plant communities found in this system are shaped by salt spray varies. Extreme salt spray or saltwater flooding in storms can severely disturb vegetation, though it recovers if the landforms have not been altered. Mature Quercus virginiana trees are fire-resistant when mature, and their litter also does not easily burn (Stalter and Odum 1993). Fire may have naturally occurred infrequently in this system, but probably was not an important factor. Extreme salt spray or saltwater flooding in storms can severely disturb vegetation, although the vegetation recovers if the landforms have not been altered.

Conversion of this type has primarily resulted from clearing and development. Maritime forests occur on the most stable portions of barrier islands and are very attractive building sites. Clearing lots for houses involves disturbing or destroying most, if not all, of the natural vegetative cover to make space for homes, parking areas, drainage fields, and septic systems. Following construction, native vegetation is often replaced by lawns and ornamental shrubs, many of which are exotic and/or invasive (Bellis 1995).

Remnants of maritime forest systems are also threated by edge effects and fragmentation. Breaks in the canopy create eddies in the wind and increase deposition of salt spray. Removal of vegetation on the seaward side increases salt spray deposition on interior portions and can lead to the death of canopy trees and other vegetation. Adjacent clearing, small openings for houses, and roads all contribute to these problems. In addition, several studies have confirmed that road building on barrier islands affects salt transport patterns into the interior of maritime forests (Eaton 1979, Seneca and Broome 1981).

Roads threaten the growth patterns and species composition because opening the forest canopy allows increased salt penetration to the forest interior. Areas without extensive fragmentation into small lots will still suffer degradation from construction of roads, even those that parallel the axis of the barrier island (Bellis 1995). Any kind of canopy opening exposes the uncleared areas of forest vegetation to increases in salt aerosol impact, wind shear, and altered drainage (Gaddy and Kohlsaat 1987). Generally, at least one main road is constructed along the entire length of a barrier island, above the dune ridge at the perimeter of maritime forests, to permit easy access to beaches. Other roads are built laterally to the trunk road for access to developments and private residences. These feeder roads, such as those constructed to provide beach access, are typically parallel to the direction of onshore winds, and serve to intensify the effects of salt spray and wind shear, further degrading the canopy. These would be regarded as having moderately severe degradation. The presence of only roads parallel to the axis of the barrier island represent low severity of degradation, although these are cumulative processes and the degradation will continue to increase with time.

An additional stressor to wetland communities in this system is the removal of groundwater from barrier island aquifers. Rainfall is generally the only source of freshwater on barrier islands, and the maritime forest community acts as the primary watershed. Precipitation entering the watershed is rapidly drawn deep into a freshwater lens, which floats above the denser saltwater in the permeable sediments beneath barrier islands. Pumping of groundwater can dry out wetlands in dune swales. Excessive pumping of freshwater from the lens for residential and commercial purposes can lead to loss of the hydrostatic head in the freshwater lens, which could, in turn, increase the rate of saltwater intrusion into surface waters on the island (Ward 1975, Winner 1975, 1979, Bellis 1995).

The most significant potential climate change effects over the next 50 years (until the early 2060s) include rising sea level and an increase in storms. The climate is expected to be warmer, and estimates of changes in rainfall amounts vary widely. Most maritime upland forest sites are more than 1 m above sea level and are unlikely to be directly inundated. Even if the Outer Banks of North Carolina collapses and most of it is lost, the wide areas that support most of the maritime forests will remain as islands. However, erosion of foredunes and the resulting increased salt spray may be significant impacts. Coastal erosion will likely reduce their extent. Increased hurricane activity, with associated storm surge into the lower portions, heavy salt spray and windthrow will increase mortality of trees and other vegetation (NCDENR 2010). Under possible conditions of climate change, increased natural disturbance by wind, salt spray, and storm surge intrusion will be significant, but the magnitude is quite uncertain. Examples of this system contain species that can recover from these disturbances, but increased frequency will result in younger canopies, more time spent in recovery stages, and shifts toward the most tolerant species. Some maritime forests will likely become maritime shrub and some maritime shrub will become grassland (NCDENR 2010).

Invasive exotic species are also threats, including Vitex rotundifolia, Ligustrum sinense (C. Jolls pers. comm.) and introduced exotic Phragmites australis (Saltonstall 2002).

This system is found from southernmost Virginia to central South Carolina (south approximately to the Cooper River where the true Sea Islands begin).