Names for this community in the Carolinas include streamhead pocosin, sandhill seep, and seepage pocosin (Nelson 1986, Schafale and Weakley 1990). Other synonyms are seepage slope in Florida (FNAI and FDNR 1990), Coastal Plain shrub bog/seep in Georgia (Wharton 1978), mesotrophic saturated scrub in Virginia (Rawinski 1990), and semi-evergreen broadleaf acid seep forest in Louisiana and Texas (Bridges and Orzell 1989).
Range/Distribution
Streamhead pocosins do not occur in the Mississippi alluvial plain, but otherwise occur in scattered locations throughout the upper Coastal Plain and fall-line sandhills. Their range extends from southeastern Virginia to northern Florida and west to southeastern Alabama (Martin 1992).
Environmental Factors
Topographic Position
This community occurs in headwaters of small streams in sandhill areas, on flat bottoms surrounding creek heads, and on adjacent seepage slopes (Martin 1992, Schafale and Weakley 1990).
Hydrology
This community receives oligotrophic runoff and seepage from pocosins and sandhills. Like other pocosins, the hydrology is palustrine and the community is seasonally to semipermanently saturated (Schafale and Weakley 1990).
Fire Regime
Streamhead pocosins are influenced by fire in uplands because of their long, narrow shape. Fire is frequent along the edges, but streamhead pocosins are usually too wet to carry fire (Martin 1992, Weakley and Schafale 1991).
Soils
Soils consist of an organic layer overlying or embedded with clay or sand, or wet, seepy sands underlain with clay (Schafale and Weakley 1990). The peat layer, when present, rarely exceeds 30 cm in depth (Martin 1992). These communities receive nutrients from adjacent uplands through groundwater and thus are more fertile than peatland pocosins (Schafale and Weakley 1990).
Physiognomy/Structure
Streamhead pocosin communities are characterized by having a scattered to very dense canopy, a dense shrub layer, and a less sparse herb layer than other pocosin types (Martin 1992, Schafale and Weakley 1990). Infrequently burned streamhead pocosins tend to have greater concentrations of trees and shrubs and fewer herbs than frequently burned examples (Martin 1992).
Commonly Associated Plant Communities
Streamhead pocosins grade upland into sandhill seeps, pine flatwoods, and longleaf pine/turkey oak sandhills (Schafale and Weakley 1990). They grade downstream into Coastal Plain small stream swamps (Schafale and Weakley 1990). They are also associated with AWC swamp forests, bay forests, and beech-magnolia forests (Martin 1992).
Successional Relationships
Under circumstances that are not clear, streamhead pocosins may develop into AWC swamp forest (Schafale and Weakley 1990). In the absence of fire over periods ranging from 20 to 50 years, succession to bay forest or Coastal Plain small stream swamp may occur (Martin 1992). Frequent fire (more often than every 5 years) may lead to the development of an herbaceous bog community at streamhead locations (Martin 1992).
Biological Composition
The canopy consists primarily of pond pine (Pinus serotina) and sweet bay (Magnolia virginiana); but may also include slash pine (P. elliottii), loblolly pine (P. taeda), swamp red bay (Persea palustris), tulip tree (Liriodendron tulipifera), red maple (Acer rubrum), swamp tupelo (Nyssa biflora), black gum (N. sylvatica), and AWC (Martin 1992). The shrub layer is dominated by titi (Cyrilla racemiflora), buckwheat tree (Cliftonia monophylla), and fetter-bush (Lyonia lucida) (Martin 1992). In North Carolina, netted chainfern (Woodwardia areolata), cinnamon fern (Osmunda cinnamomea), and sedge (Carex spp.) are typical herbs (Schafale and Weakley 1990).