Physiognomy and Structure: The cover and structure of vegetation are highly variable across the range of this macrogroup. It can range from sparsely to completely vegetated and include lichen-dominated, herb-dominated, shrub-herb complexes, and shrub-dominated areas. Some examples within the Great Lakes and North Atlantic Coast may contain a scattered coniferous overstory.

Floristics: This macrogroup includes a combination of grasslands, dwarf-shrublands, shrublands and open-treed savannas. On dunes along the Great Lakes and North Atlantic Coast, Ammophila breviligulata is the most common grass species (Leymus mollis may replace it northward in Newfoundland); Ammophila champlainensis is the most common grass on the shore of Lake Champlain. Other common species include Calamovilfa longifolia, Panicum spp., and Schizachyrium scoparium. In the Great Lakes, low evergreen shrubs such as Arctostaphylos uva-ursi, Juniperus communis, and Juniperus horizontalis occupy dune crests, dune fields, and also the ground layer in the savanna edge of dunes and sandplains. Prunus pumila, Salix cordata, and Salix myricoides (= Salix glaucophylloides) may occur, and Pinus banksiana, Pinus resinosa, Pinus strobus, and Thuja occidentalis often form a scattered overstory canopy. Coastal dunes of the Northeast are characterized by Carex silicea, Cenchrus tribuloides, Hudsonia tomentosa, Lathyrus japonicus, Morella pensylvanica, Panicum amarum, Panicum virgatum, Polygonella articulata, Schizachyrium littorale, Schizachyrium scoparium, and Solidago sempervirens.

Unusual expressions are sandplain grasslands and heathlands of the southern New England / New York coast. These are areas of graminoid- and shrub-dominated vegetation maintained by the combination of extreme conditions and periodic fire or other disturbance. Developing on acidic, nutrient-poor, and very well-drained soils within a few kilometers of the ocean, they may occur as heathlands, grasslands, or support a patchwork of grass and shrub vegetation. Characteristic species include Amelanchier nantucketensis, Arctostaphylos uva-ursi, Carex pensylvanica, Corema conradii, Deschampsia flexuosa, Gaylussacia baccata, Hudsonia ericoides, Hudsonia tomentosa, Schizachyrium scoparium, and Vaccinium angustifolium. Human disturbances may be partly responsible for the origins of these grasslands and heathlands (Motzkin and Foster 2002).

On rocky headlands of northern New England and Canadian Maritime Provinces, Juniperus horizontalis and Juniperus communis may occur, with Empetrum nigrum, Plantago maritima, Solidago sempervirens, and Ligusticum scoticum. Dwarf heath-grassland is dominated by Festuca rubra, Aronia melanocarpa (= Photinia melanocarpa), Symphyotrichum novi-belgii, Vaccinium angustifolium, Vaccinium vitis-idaea, among others. Low coastal shrublands are Gaylussacia baccata- or Gaylussacia dumosa-dominated. Tall shrublands are dominated by Alnus incana ssp. rugosa, Ilex mucronata (= Nemopanthus mucronatus), Aronia x prunifolia (= Photinia floribunda), Prunus pensylvanica, and Viburnum nudum. Gaylussacia baccata and Morella pensylvanica occur in the understory. Common herbs include Pteridium aquilinum var. latiusculum, Trientalis borealis, and Maianthemum canadense (S. Basquill pers. comm. 2015).

Along the South Atlantic Coast, Panicum amarum and Uniola paniculata are characteristic on the foredunes, and Spartina patens (= var. monogyna) and Schizachyrium littorale on the older dunes and sand flats. Iva imbricata is a characteristic shrub. Examples along the Gulf Coast contain Ceratiola ericoides, Chrysoma pauciflosculosa, Helianthemum arenicola, Paronychia erecta, and Schizachyrium maritimum. On the western Gulf Coast, this macrogroup includes ridges dominated by Schizachyrium littorale and a mixture of forbs, and swales dominated by Andropogon gerardii, Muhlenbergia capillaris, Paspalum monostachyum, and Sorghastrum nutans.

Dunes in the northern Great Lakes region, especially Lake Superior, shift in composition. A description is needed.

Dynamics:  The environment of this macrogroup is one of the most dynamic in existence for terrestrial vegetation. The dunes are reworked by storms or by more gradual eolian processes that may completely change the local environment in a short time. Many of these sites are fairly early in the process of primary succession on recent surfaces. The sandy sites found in this macrogroup are influenced by wind deposition, including active dune processes of wind-caused "blowouts" and subsequent restabilization. Environmental processes include sand deposition, sand erosion, and stabilization. Along the Atlantic and Gulf coasts, overwash, erosion, and sea spray from storms occur often. Hurricanes and lesser storms significantly alter this vegetation on a regular basis. Vegetation interacts strongly with geologic processes with the presence of grass an important factor in the development of new dunes. Alteration of dynamic processes, such as artificial enhancement of dunes by planting or sand fencing, can have drastic effects on this vegetation, causing large areas to succeed to woody vegetation.

Great Lakes dunes are relatively young, as the Great Lakes were occupied by ice until approximately 16,000 years ago. The dune sands are derived from glacial sediments, including lacustrine and outwash sands and sandy tills. Most of the larger dune complexes are associated with the Lake Nipissing stage of the Great Lakes, when water levels were 7.6 to 9 m (25-30 feet) higher than present-day lake levels (Dorr and Eschman 1970, cited in Kost et al. 2007). These higher lake levels resulted in greater amounts of coastal erosion and dune formation. A combination of water erosion and wind deposition resulted in the formation of Great Lakes coastal dunes. The sand source for the coastal dunes was glacial sediment that was eroded by streams and by waves eroding bluffs along the Great Lakes shoreline. These sediments were then moved along the Great Lakes shoreline by near-shore currents, and then deposited along the shoreline by wave action. Strong winds then carried the sands inland, creating dunes. Blowouts, sand burial and abrasion, excessively well-drained and droughty soils, desiccating winds, and occasional fires maintain open conditions (Kost et al. 2007). Great Lakes dunes have been negatively impacted by residential development.

On dunes in the Northeast, this vegetation has been altered by hardening of shorelines, trampling, off-road vehicle traffic, and residential development. Barrier islands may be heavily grazed by wild horses.