Hardwood Hammocks: Ecosystem Description

Upland hardwood hammocks extend along the coastal plain, from eastern Texas to North Carolina.  These mixed evergreen-deciduous hardwood ecosystems have some of the highest number of tree and shrub species per unit area in the United States (Platt and Schwartz 1990). Live Oak (Quercus virginiana) is a common overstory dominant; other overstory species include southern magnolia (Magnolia grandiflora), Pignut hickory (Carya glabra), sweetgum (Liquidambar styraciflua), beech (Fagus grandifolia) and cabbage palm (Sabal palmetto). Dogwood (Cornus florida), hophornbeam (Ostrya virginiana), and other oak species (Quercus spp.) are common understory species in hardwood hammocks. Shrub species include saw palmetto (Serenoa repens) and greenbrier vines (Smilax spp.). Because of dense overstory layer and shrub cover herbaceous layers are often sparse or non-existent (Laessle and Monk 1961).

Soils of hammocks are usually phosphatic or calcareous and fertile (Christensen 1981), although areas that are less fertile have been shown to support hardwood hammock species in the absence of fire (Monk 1968).

Upland hardwood hammocks are divided into different classes (mesic and xeric) based upon the soil moisture characteristics of the site. Hydric hammocks also occur, but only in bottomland areas. Vince et al. (1988) provides a thorough overview of hydric hammocks. Large expanses of hardwood hammocks do not occur like other southeastern ecosystems such as pine flatwoods. Instead scattered patches of hardwood hammocks are found between upland sand/clayhill pinelands (Platt and Schwartz 1990), and sites that are protected from fire, such as a leeward site of a wetland (Myers 2000).