Gulf Coast Interior Longleaf Pine Woodland

This ecological system represents Pinus palustris forests of rolling, dissected to relatively flat uplands of the East Gulf Coastal Plain. These stands occur primarily in the Southeastern Plains (EPA Ecoregion 65). It is found inland of the Gulf Coast Flatwoods (EPA Ecoregion 75a) and extends landward into the Upper East Gulf Coastal Plain Ecoregion by about 80 km (50 miles). It potentially occupies a much larger geographic area than the related Pinus palustris woodlands of the outer coastal area. The characteristic species is Pinus palustris, although many stands may support only relictual individuals following a long history of exploitation, harvest, and stand conversion, primarily to agriculture or to planted stands of Pinus elliottii var. elliottii or Pinus taeda. This system includes stands with a range of soil and moisture conditions. Mesic stands on medium- to fine-textured soils are more typical of the system, although limited xeric areas on deep sands are also present. In natural condition, fire is believed to have been frequent enough to limit development of fire-intolerant hardwood species as well as Pinus taeda and Pinus echinata. Although such species may be present or even common in the most mesic stands, they generally do not share dominance in the overstory unless fire has been absent from the stand.

Occurrences of this system are typically more-or-less open-canopy stands (woodlands) dominated by the evergreen needle-leaved tree Pinus palustris. In parts of the range, and on more rolling topography, other pines may be present, including Pinus echinata and Pinus taeda. These may increase or become codominant with extended fire-return times. Unless fire suppression is extreme, deciduous trees generally do not share dominance in the canopy. More mesic stands (e.g., those on finer-textured soils) may contain oaks, such as Quercus falcata, Quercus nigra, or Quercus pumila, and occasionally species favoring more xeric conditions, such as Quercus marilandica or Quercus stellata, in combination with the more mesic oaks. Even more xeric stands (uncommon in this system) may contain "scrub oaks" such as Quercus incana, Quercus laevis, Quercus margarettae, or Quercus arkansana. In fire-suppressed areas, Quercus falcata, Liquidambar styraciflua, Acer rubrum, Quercus nigra, Nyssa sylvatica, Cornus florida, Callicarpa americana, and/or Rhus copallinum may invade or increase. Some typical mesic to dry-mesic herbaceous species include Andropogon ternarius, Andropogon gyrans var. gyrans, Schizachyrium scoparium, Sorghastrum nutans, and Panicum virgatum. Aristida stricta or Aristida beyrichiana are also dominant or at least present in the herbaceous layer of many more southern and coastward examples. Variation in floristic composition of this wide-ranging system is related to site conditions, fire-return interval, and local or regional floristics. The herbaceous layer typically becomes much less diverse with increased fire-return interval. The wiregrass Aristida beyrichiana is not present throughout the range of this system, and even within the range of this species, it tends to be dominant or more abundant in moister sites, particularly in the western part of the system's range (and also in examples of East Gulf Coastal Plain Near-Coast Pine Flatwoods (CES203.375)).

This system once occupied extensive areas of the East Gulf Coastal Plain from the northern range limits of Pinus palustris southward to the inland terminus of the Coastal Flatlands (sensu Peet and Allard (1993); Ecoregion 75a (EPA 2004)). In its natural condition, this system occupied a range of upland soils from clays and loams to deep sands, including weathered and older Ultisols. Due to locally distinctive understory, shrub and herbaceous vegetation associated with differing soil textures, "sandhills" and "loamhills" are generally recognizable as distinctive components of this system. However, they are generally interspersed to such an extent that differentiating them as separate systems is not practical. The topography of this system is generally more rolling than East Gulf Coastal Plain Near-Coast Pine Flatwoods (CES203.375) to the south. The largest and best examples occupy landscapes where prescribed fire is an active management practice. Localized soil characteristics will determine the specific composition of the lower strata. Ultisols are the dominant soil order and cover most of the range of the system. Ultisols most commonly associated with Pinus palustris are the Typic Paleudults and Plinthic Paleudults. More limited areas are occupied by Psamments and other coarser-textured materials. Pinus palustris grows in warm, wet temperate climates characterized by hot summers and mild winters. The annual mean temperatures range from 16-23°C (60-74°F), and the annual precipitation ranges from 1090 to 1750 mm (43-69 inches) (Boyer 1990). Fall is the driest season of the year, although periods of drought during the growing season are not unusual (Boyer 1990).

Frequent fire was the predominant natural disturbance in this system, which is now dependent on management with prescribed fire. Component communities naturally burned every few years, many averaging as often as every 3 years. Fires are naturally low to moderate in intensity. They burn above-ground parts of herbs and shrubs but have little effect on the fire-tolerant trees. Vegetation recovers very quickly from fire; the perennial species resprout quickly. Many herbaceous plants have their flowering triggered by burning. Frequent fires help maintain more species richness at small sample scales, compared to pinelands of the other regions (Carr et al. 2010). In the absence of fire, hardwoods increase. Quercus spp. and shrubs, kept to low density and mostly reduced to shrub size by fire, become tall and dense and can suppress Pinus palustris regeneration. Herb layer density and diversity decline without occasional fire. Frequent fire requires a mix of fine fuels composed both of herbaceous (primarily grasses) fine fuels and Pinus palustris leaf litter. Consequently, thinning the Pinus palustris canopy to low basal area or opening too large gaps, particularly in absence of Aristida beyrichiana, can lead to rapid hardwood encroachment due to lack of abundant and continuous fuels necessary for frequent fire (K. Kirkman pers. comm.). Only on the most excessively drained coarse sands does the vegetation not undergo substantial structural alteration and reduction in species richness after a number of years without burning. This is due to the infertile soils. This structural alteration occurs more slowly on these infertile soils, but due to the slow accumulation of fuels, lack of fire can become more pronounced.

Canopies are believed to naturally be multi-aged, consisting of a fine mosaic of small even-aged groves driven by gap-phase regeneration. Pinus palustris is shade-intolerant and slow to reach reproductive age but is very long-lived. Pinus palustris seedlings can survive under a gap opening in canopy >35%. However, they will not move out of grass stage unless the gap fraction is >60%. Because these canopy gaps have less needle fall, the frequent fires which burn there are less intense, which permits Pinus palustris seedlings to survive. Pinus palustris can also stay in the sapling stage for decades and still take advantage of a gap opening to move into the canopy (Kirkman and Mitchell 2006).

Lack of fire is a big threat for all Pinus palustris ecosystems. Threats also include the loss of habitat from commercial and residential development, and fragmentation of habitat by roads. These threats limit prescribed burning due to urban interface, safety and smoke management concerns. Invasive exotic species are threats, including Imperata cylindrica (Brewer 2008), Lespedeza bicolor, Lespedeza cuneata, Ligustrum sinense, Lonicera japonica, Lygodium japonicum, and feral pigs (Sus scrofa), which root up Pinus palustris seedlings (Wahlenberg 1946) and herbaceous plants with thick roots. Pinus palustris woodlands have declined due to conversion to intensively managed pine plantations. The collecting of snakes by putting gasoline or kerosene in gopher tortoise burrows is a real threat, as it pollutes the tortoise burrow which is habitat for many species.

This system formerly occupied an extensive range across the southern parts of Alabama, northern Panhandle of Florida (north of the Cody Scarp), southern Mississippi, and southwestern Georgia and was also present in limited areas of Louisiana. It has been greatly reduced in its extent, with much of its range now occupied by agriculture or by planted stands of Pinus taeda. In southwestern Mississippi, this system is apparently absent (or very rare and limited) west of 91°W longitude to the limits of the alluvial plain and northwest of a line running approximately from the intersection of 31°N latitude and 91°W longitude, northeastward to the city of Jackson, Mississippi. This is consistent with the ranges of "Oak-Pine" vegetation versus "Longleaf-Loblolly-Slash Pines" (generally equivalent to this system) in Shantz and Zon (1924). In southwest Georgia, this ecological system occurs in Coastal Plain areas which drain to the Gulf of Mexico.