Pocosins in the strictest sense are shrub bogs that occur on domed peatlands that have developed on clay soils in shallow basins and divides between ancient rivers and sounds in the Atlantic Coastal Plain (Richardson 1991). Pocosin-like vegetation also occurs in large Carolina bays with deep peat. The largest domed peatlands occur primarily in North Carolina, but pocosins and pocosin-like vegetation extend into South Carolina and Georgia. Many pocosins are large in extent covering thousands of acres.

Nutrient inputs and hydrology are dominated by rainfall, and soil formation processes are influenced by hydroperiod. Precipitation is the only form in which water and nutrients enter the system. Hardpans of clay or other substances underlie peat deposits and pond water; thus, pocosins have long hydroperiods, typically 6-9 months per year (Sutter and Kral 1994). The water table is highest in winter when evapotranspiration is low and lowest in summer, even though the rainfall is most abundant July through September (Richardson and Gibbons 1993, Sharitz and Gresham 1998). Soils are deep peats and organic mucks that have formed because of the long hydroperiod. These soils are extremely low in nutrients, particularly phosphorus. Domed peatlands are topographically elevated above the surrounding communities and water exits these systems through streams and rivers that form on peatland margins (Richardson and Gibbons 1993, Sharitz and Gresham 1998).

Vegetation of domed peatlands is often somewhat concentrically arranged, but also can have a mosaic pattern produced by fire. Low pocosin typically occupies central portions of peat domes and grades into high pocosin in intermediate portions of peat domes. (Weakley and Schafale 1991). Pond pine woodland, bay forests or Atlantic white cedar swamp are found on outer portions of peat domes and depending on moisture regime those communities grade into either savannas and flatwoods on drier sites or swamp forest where communities grade into lakes or other water bodies. The zonation of vegetation is less clear in large Carolinabays where both high and low pocosin can occur than in large domed peatlands (Weakley and Schafale 1991). High and low pocosins in Carolinabays are often surrounded by frequent fire communities such as pine flatwoods, or pine savannahs (Weakley and Schafale 1991).

The large domed peatlands occurrence of high pocosin, and low pocosin, are associated with gradients of soil depth and nutrient availability, though fire frequency may also play a role (see successional relationships). Low pocosins have deep peats 1 – 5 m (3-16 ft) and extremely low available nutrients. High pocosins have peat deposits that are shallower, typically up to 1.5 m (5 ft). Nutrients tend to be less limited where peat is shallow because vegetation can root in mineral soils where nutrients are more available than in peat (Sharitz and Gresham 1998, Weakley and Schafale 1991).

Vegetation

The vegetation of high pocosin and low pocosin share some dominant species but differ in vegetation structure (except soon after fires). Low pocosins are characterized by low shrub stature, less than 1.5m (5 ft) and a sparse tree canopy. Dominant low pocosin vegetation includes titi (Cyrilla racimiflora), fetterbush (Lyonia lucida), and (Zenobia pulverulenta). Greenbrier (Smilax laurifolia) is a common vine, and trees include pond pine (Pinus serotina), red maple (Acer rubrum), sweetbay magnolia (Magnolia virginiana), red bay (Persea borbonia), and loblolly bay (Gordonia lasianthus) (Richardson 1991, Weakley and Schafale 1991). Openings in low pocosin (occasionally in high pocosin) often have standing water and can include herbaceous species such as Virginia chain fern (Woodwardia virginica), grasses (Andropogon glomeratus), sedges (Carex striata), non-vascular plants (Sphagnum spp.) and carnivorous plants such as (Sarracenia flava), (Sarracenia purpurea), and sundews (Drosera spp.) (Weakley and Schafale 1991, Christensen 1981).

High pocosin is characterized by taller shrubs than those of low pocosin, 1.5 to 3 m tall, with an overstory that is more dense than that of low pocosin, but still scattered (Weakley and Schafale 1991, Sharitz and Gresham 1998). Titi, fetterbush, and gallberry (Ilex glabra) dominate high pocosin vegetation. Switch cane (Arundinaria gigantea) may also occur in high pocosin. Herbs in high pocosin are uncommon to absent, except immediately following fire.

Pond pine and Zenobia are considered indicators of pocosin vegetation and the latter is essentially an endemic of pocosin vegetation (Weakly and Schafale 1991, Sharitz and Gresham 1998).

Rare plants in high and low pocosin are generally associated with herbaceous openings (Robertson et al 1998), which fires are important in creating, and the pond pine woodland ecotone, which is fire maintained. Various pitcher plants and other carnivorous plants are found in these openings. The federally endangered rough leaved loosestrife (Lysimachia asperulifolia) can be found in low pocosin within Carolina bays and other habitats (USFWS 1987). The once federally listed white wicky (Kalmia cuneata) can also be found in Carolina bay pocosins (USFWS 2000). Several other rare species tracked by state heritage programs are also associated with herbaceous openings in pocosins (Robertson et al. 1998).

Animals

There has been very little research on pocosin fauna. There are no known animals that are endemic to pocosins. Generally, the animals that are characteristic of the region are found in pocosins. Pocosins likely serve an important function as regional refugia for many species of wildlife, in large part because they are the only natural areas that remain (Richardson and Gibbons 1993).

The invertebrate fauna of pocosins is not well studied. Two species that are commonly cited as being associated with pocosins include the swamp specializing palamedes swallowtail butterfly (Papilio palamedes) and the Hessel’s hairstreak (Mitoura hesseli), whose larval food plant is Atlantic white cedar (Chamaecyparis thyoides) (Richardson and Gibbons 1993, Sharitz and Gresham 1998). Atlantic white cedar is an occasional inhabitant of high pocosin. Presumably, the suite of species associated with insectivorous plants such as pitcher plants (Sarracenia spp.) and sundews (Drosera spp.) are present.

Fish that inhabit larger water bodies situated within pocosins include typical game fish of the region. Likewise amphibian and reptile species characteristic of the region are presumed inhabitants of pocosins. Rare species include the eastern diamondback rattlesnake (Crotalus adamanteus), and the American alligator (Alligator mississippiensis) (Sharitz and Gresham 1998).

Avian fauna are somewhat better studied, but like other groups, the inhabitants are characteristic of the region. High pocosin and pond pine woodland tend to support suites of bird species that are similar to regional suites of species. Low pocosin is relatively low in bird diversity and abundance probably due to low levels of structural diversity. Eighty-three species of wintering birds have been documented from high pocosin. Three abundant species of low pocosin include common yellow throat warblers (Geothlypis trichas), eastern wood peewees (Contopus virens) and rufous-sided towhees (Pipilo erythrophthalmus) (references in Sharitz and Gresham 1998).

Typical mammals of pocosins include common species such as white tailed deer, raccoon and possums as well as animals specializing in wetland habitats such as northern river otters, mink, and marsh rabbits. Small mammals include common shrews, and mice. The southernmost occurrence of bog lemmings is in unmodified pocosins in central North Carolina (Mitchell et al. 1995). The black bear will use large tracts of pocosin and is now dependent on large tracts of pocosin vegetation for cover (Sharitz and Gresham 1998, Robertson et al 1998).

Several community types occupy large domed peatlands and are often arranged somewhat concentrically. In the interiors of these peatlands, low pocosin occupies the deepest most nutrient poor peats. High pocosin is intermediate in nutrient status and peat depth. On the outer portions of these peat domes, where peat is most shallow, are either bay forests, pond pine woodlands or Atlantic white cedar forests or other swamp forests (Weakley and Schafale 1991). Herbaceous communities can be scattered throughout. Similar community types can be found on smaller peatlands. It is clear that fire, hydrology and nutrient availability play roles in which communities develop where, but their exact roles and interactions are not well studied.

There are two opposing theories of succession in large domed peatland communities. One theory (Wells 1928) proposes that fire is the controlling factor, where frequent fire promotes low pocosin, intermediate frequencies result in high pocosin and very low frequencies result in bay forests. The other theory (Otte 1981 cited in Sharitz and Gresham 1998 and Richardson and Gibbons 1993) suggests that nutrients are the controlling factor. There is a gradient of nutrient availability (phosphorus being most limiting) from very limited nutrient availability in low pocosin to high pocosin to more available nutrients in bay forest (Richardson and Gibbons 1993). In the development of these peat domes, as peat accumulates and becomes deeper, nutrients become more and more limiting as plant roots fail to reach underlying mineral soils. Thus, according to Otte’s theory, the successional trajectory is from marsh to swamp to bay forest to high pocosin to low pocosin, reflecting the build-up of peat and the decreasing availability of nutrients.

Others have recognized that nutrient limitations on domed peatlands may be a special case, and where nutrients are not so limiting, fire frequencies are more critical in determining community type (Christensen 1981, Frost 1995). Frost (1995) described the pre-settlement occurrence of these community types with respect to fire frequencies, soil fertility and organic matter depth.

Despite lack of study and different theories some patterns do seem clear. Atlantic white cedar forests develop under a very specific fire regime, where seed sources are available after infrequent, catastrophic, high intensity surface fires (crown fire), when water tables are high and peat doesn’t ignite or doesn’t burn deeply. Small Atlantic white cedar does not tolerate even low intensity fire, thus for stands to exist fires must not be frequent (Schafale and Weakley 1990). In the absence of fire Atlantic white cedar forests are believed to become bay forest, pond pine woodland or other types of swamp forest.

Relatively more frequent fire favors pond pine woodland rather than Atlantic white cedar forest or bay forest (Schafale and Weakley 1990). On sites where nutrients are not as limiting as in the high and low pocosins of large domed peatlands, the vegetation sequence goes from pond pine woodland to high pocosin to low pocosin with increasing frequency of fires (Frost 1995). High and low pocosins on large domed peatlands tend to maintain vegetation structure and composition even in the absence of fires thus lending credence to the nutrient limitation theory.

Severe fires that consume peat in any of these communities can result in an herbaceous community (Hungerford et al. 1998). The magnitude of soil consumption required for the development of an herbaceous community is unknown and likewise weather it is soil consumption per se that is the cause is unknown.

The prolonged absence of fire in communities except the most nutrient limited (high and low pocosin of large domed peatlands) is thought to promote succession toward bay forests (Weakley and Schafale 1991). Within the landscape mosaic, bay forests are situated where, by chance fire frequency has been lowest, or where landscape features create areas that are not likely to burn, for instance along drainage ways that develop at the edges of domed peatlands (McKevlin 1996). Most bay forest species are known to resprout so after some non-severe burns bay forests may regenerate themselves rather than becoming either Atlantic white cedar forests, or pond pine woodland or an herbaceous community (Schafale and Weakley 1990).

Many possible successional pathways have been suggested for each of these communities (reviewed in McKevlin 1996). It seems that the successional pathway a community takes is dependent on the frequency, intensity and severity of fires along with soil fertility and hydrologic conditions during and after the fire (McKevlin 1996, Frost 1995). Hydroperiod may be very important because of its effects on fire frequency and peat build-up. Peat build-up in turn affects nutrient status. Fire reduces peat formation and also creates a temporarily more fertile environment by releasing nutrients stored in organic matter. Water table depth during a fire contributes to depth of peat consumption.

These communities may be perpetuated by fire or may become other community types because of fire. With more study, these relationships may become clearer. Current research mapping community types with remote sensing technology (Bucher and High 2000) coupled with mapping of fire footprints and other parameters related to fire frequency, intensity and severity may help reveal more information on successional relationships of these communities.