Nomenclature
A. System: Terrestrial or Palustrine (Allard 1990)
B. Physiognomic Type: Terrestrial Woodland/Savannas and Palustrine
Woodland/Savannas (Allard 1990)
Classification System
This community is synonymous with the "flatwoods" community described by Stout and Marion (1993), the "mesic pine communities," (including flatwoods and savannas) of Christensen (1988), and the "flatwoods" of Abrahamson and Hartnett (1990). Also included in this description are "wetland longleaf pine savannas" of the West Gulf Coastal Plain, described in Bridges and Orzell (1989).
Several pine flatwoods communities are described under a variety of names in state classification systems. In Louisiana, pine flatwoods and pine savannas are referred to as mesic pine flatwoods and wet pinewood savannas respectively (Smith 1988). Wharton's (1978) mesic pine lowland forest and longleaf pine upland forest in Georgia are also types of pine flatwoods (Stout and Marion 1993). In Mississippi, coastal flatwood forests, wet flatwood forests, wet pine savannas, and pine savannas are types of pine flatwoods (Allard 1990). Nelson's (1986) pine savannas, pine flatwoods, pine-saw palmetto (Serenoa repens) flatwoods, and upland pine-wiregrass (Aristida stricta or A. beyrichiana) woodlands in South Carolina are all types of pine flatwoods communities. In North Carolina's state classification (Schafale and Weakley 1990), wet pine flatwoods, pine savannas, and mesic pine flatwoods are all types of pine flatwoods, as are mesic flatwoods and wet flatwoods in Florida (FNAI and FDNR 1990). In Texas, the longleaf pine-beakrush series is a pine flatwoods community (Allard 1990).
Range
A. Bailey's Ecoregion: Province 232-Outer Coastal Plain Mixed Forest. Section 232B-Coastal Plains and Flatwoods, Lower; Section 232C-Atlantic Coastal Flatlands; Section 232D-Florida Coastal Lowlands (Western); Section 232F-Coastal Plains and Flatwoods, Western Gulf; 232G-Florida Coastal Lowlands (Eastern).
B. Current Distribution: Southeastern coastal plain from Southeast Virginia south to Florida and west to Texas (Stout and Marion 1993).
Environmental Factors
A. Topographic Position: This community occurs on extensive flats or terraces and generally has low, flat topography (Stout and Marion 1993). On the West Gulf Coastal Plain, abundant pimple mounds and swales provide microtopographic heterogeneity (Bridges and Orzell 1989).
B. Hydrology: The community occurs on poorly drained soils. Soils may be saturated or exhibit standing water during the wet season, but may also dry out during the summer (Christensen 1988).
C. Fire Regime: Frequent, low-intensity surface fires generally characterize the fire regime. Historical evidence suggested that a fire frequency of 1 to 3 years is necessary to maintain this community (Ware, Frost, and Doerr 1993). The chances that a severe, crown-killing fire will occur increase as the fire frequency decreases (Christensen 1988).
D. Soil: This community occurs on fine sandy loams, silt loams, and sandy soils that are poorly drained, acidic, and otherwise low in nutrients (Abrahamson and Hartnett 1990). Moisture level, pH, texture, and clay content of the soil vary across the range of this community. Soils supporting this community in the West Gulf Coastal Plain are generally more calcareous than those to the east (Bridges and Orzell 1989).
Physiognomy/Structure
Pine flatwoods (sensu Stout and Marion 1993) typically exhibit an emergent tree layer of pines with limbless lower trunks and a ground layer of low vegetation. However, physiognomy varies markedly with fire regime and moisture. For thisreason, some authors (e.g., Christensen 1988) have subdivided pine flatwoods into two communities, flatwoods and savannas. In this case, "savannas" generally refer to communities that have not experienced fire suppression and have a sparse canopy of pines and a diverse groundcover, while "flatwoods" may refer to fire-suppressed communities that exhibit a well-developed woody understory and a sparse groundcover (Christensen 1988). Note that, in other cases (e.g., Schafale and Weakley 1990), flatwoods and savannas refer to communities on different physical sites.
Commonly Associated Plant Communities
Wet prairies, marshes, upland sandhills, pine woods, dry prairies, sand pine (Pinus clausa) scrub, scrubby flatwoods, xeric sandhills, and pocosins often occur adjacent to pine flatwoods (Abrahamson and Hartnett 1990, Christensen 1988). Pine flatwoods can be bordered by beech-magnolia (Fagus grandifolia - Magnolia grandiflora) forest (southern mixed hardwood forest) on slopes (Bridges and Orzell 1989). In southwest Louisiana and southeast Texas, this community can grade directly into coastal prairie to the south (Bridges and Orzell 1989). Smaller, often isolated examples of communities that may be inclusions in pine flatwoods are pocosins (cypress [Taxodium spp.] dome and swamp forests, pond cypress [T. ascendens] pond forests, and small depression pocosins), pitcher plant (Sarracenia spp.) communities, and Coastal Plain small depression pond complexes (Martin 1992a-e).
Successional Relationships
Typical pine flatwoods may succeed to southern mixed hardwoods in the absence of fire, but successional rates and final composition of the vegetation may vary according to site conditions (Christensen 1988). Wetter slash pine and pond pine phases of pine flatwoods may succeed into bayheads (see Menges et. al. 1993 for results of a 20-yr study; Stout and Marion 1993). In North Carolina, flatwoods often either succeed to pocosins or persist with low species richness, in the absence of fire (M. Schafale, pers. comm., 1994).
Biological Composition
A. Dominant or Characteristic Plant Species: Longleaf pine, slash pine, and pond pine usually dominate the canopy in pure stands or in various combinations. InLouisiana, loblolly or shortleaf pine may be important canopy species (Smith 1988). Common understory species are gallberry, shiny blueberry, fetterbush, dwarf live oak, runner oak, sand live oak, hairy laurel, and southern bayberry (Myrica cerifera). Saw palmetto may also be a dominant understory component within its range (Stout and Marion 1993). Predictable grasses are wiregrass or bluestems (Andropogon and Schizachyrium spp.). Other grasses that may be important are muhly's (Muhlenbergia spp.), dropseeds (Sporobolus spp.), and toothache grass (Peet and Allard 1993, Harcombe et al. 1993). Common forbs are milkweeds (Asclepias spp.), pinebarren aster (Aster reticulatus), vanillaleaf (Carphephorus odoratissimus), gayfeather (Liatris spp.), queens delight (Stillingia sylvatica), baptisia (Baptisia spp.), milkpea (Galactia spp.), yellow colicroot (Aletris lutea), deathcamas (Zigadenus spp.), polygala (Polygala spp.), and yellow-eyed grasses (Xyris spp.; Stout and Marion 1993).
B. Variation in Structure and Composition: The composition and structure of pine flatwoods vary with geographic location, soil conditions, climate, and fire frequency. Historically, longleaf pine dominated more upland sites, while slash pine and pond pine increased in dominance with increasing periods of wetness and decreasing fire frequency. Slash pine would be codominant in its range west of southeastern Louisiana, and north of Georgetown Co., SC, while pond pine was sometimes codominant up to eastern North Carolina. Otherwise, longleaf pine occurred as a single dominant. Wiregrass is characteristic in pine flatwoods east of Mississippi, but bluestems, muhlys, and toothache grass are characteristic in pine flatwoods to the west (Stout and Marion 1993).
East of the Mississippi River, five distinct understory phases in pine flatwoods have been recognized: (1) wiregrass flatwoods, (2) cutthroat grass (Panicum abscissum) flatwoods, (3) palmetto flatwoods, (4) gallberry flatwoods, and (5) fern-south Florida slash pine (Woodwardia virginica and Osmunda cinnamomea/P. elliottii var. densa; Stout and Marion 1993).