West Gulf Coast Upland Longleaf Pine Forest

The common and unifying feature of this system is vegetation naturally dominated by Pinus palustris. This was formerly the most extensive system within its natural range in western Louisiana and eastern Texas. In most of the region, longleaf pine is (presently) a distinctive, but rarely dominant, element of existing vegetation. However, this tree historically dominated the vegetation across nearly all uplands regardless of soil type or moisture (excluding wetlands), and longleaf pine forests were among the most valuable economic resources in the region at the turn of the century. Typical sites include sandhills on well-drained to excessively drained soils, but the type is also found on loamy and clayey upland soils. The importance of frequent fire has been well documented for the perpetuation of this system. This type lies outside the ranges of Aristida stricta and Aristida beyrichiana, unlike comparable systems east of the Mississippi River, but most stands at least formerly supported open grass-dominated understories rich in species diversity.

Examples are characterized by relatively open-canopied woodlands dominated by Pinus palustris with an herbaceous layer often dominated by graminoids. It often occupied gently rolling uplands with coarse-textured, well-drained soils. Pinus echinata may be a significant component of some of the stands. Quercus stellata, Quercus marilandica, Quercus incana, Pinus taeda, Liquidambar styraciflua, and Nyssa sylvatica may also be common components of the canopy or subcanopy. Occurrences that are less frequently burned may develop a significant shrub layer with species including Callicarpa americana, Vaccinium arboreum, Vaccinium stamineum, Morella cerifera, Ilex vomitoria, Rhus copallinum, and Toxicodendron radicans. Instances with a more optimal fire-return interval will retain a more open understory with a grassy aspect. Unlike comparable systems east of the Mississippi River, this type lies outside the ranges of Aristida stricta and Aristida beyrichiana, but most stands historically supported open grass-dominated understories rich in species diversity. The herbaceous layer is often dominated by grass species such as Schizachyrium scoparium, Schizachyrium tenerum, Sporobolus junceus, Panicum virgatum, Nassella leucotricha, Andropogon ternarius, Dichanthelium spp., and Andropogon virginicus. Pteridium aquilinum may be locally abundant, forming a continuous ground cover. Forbs may be diverse in the herbaceous layer, including species such as Pityopsis graminifolia, Solidago odora, Tephrosia spp., Tragia urens, Euphorbia corollata, Croton argyranthemus, Vernonia texana, Alophia drummondii, Lespedeza virginica, Aristolochia reticulata, Rhynchosia reniformis, Stylosanthes biflora, Opuntia humifusa (= var. humifusa), Cnidoscolus texanus, Stylisma pickeringii var. pattersonii, Rudbeckia grandiflora var. alismifolia, Silphium laciniatum, Ruellia humilis, Liatris pycnostachya, and Liatris elegans. With prolonged absence of fire, hardwoods and Pinus taeda may come to dominate the system (Elliott 2011).

In most of the region, Pinus palustris is (presently) a distinctive, but rarely dominant, element of existing vegetation (Harcombe et al. 1993). However, this tree historically dominated the vegetation across nearly all uplands regardless of soil type or moisture (excluding wetlands), and longleaf pine forests were among the most valuable economic resources in the region at the turn of the century (Bray 1906).

This system represents the presumed matrix vegetation type of the inner (landward) portions of the West Gulf Coastal Plain in Louisiana and eastern Texas within the range of Pinus palustris. In Louisiana, these are mapped as the Upper Terrace and some smaller landward units (Snead and McCulloh 1984). The system is bounded on the outer (seaward) side by West Gulf Coastal Plain Wet Longleaf Pine Savanna and Flatwoods (CES203.191) and on the inner (landward) side primarily by West Gulf Coastal Plain Pine-Hardwood Forest (CES203.378) and other hardwood or hardwood-pine systems. Stands are found on sedimentary Pleistocene formations (particularly the Bentley Formation), to formations of the Tertiary period (particularly the Catahoula and Wilcox formations). Historically, this system was more widely distributed on older, more inland formations of the Eocene and Paleocene epochs. They occupy topography ranging from rolling uplands, to hills and ridges such as those associated with the Kisatchie Wold (or Kisatchie Cuesta) and the Sabine Uplift, and are usually associated with coarse-textured, well-drained Ultisols and Alfisols, including loams, sandy loams, loamy sands, and sands, though occurrences may also be found to a lesser extent on tighter soils such as clay loams (Elliott 2011). It is characteristically dissected by small to large streams.

Frequent fire was the predominant natural disturbance in this system, which is now dependent on management with prescribed fire. The importance of frequent surface fire (every 1-5 years) has been widely accepted for the perpetuation of this system (Stambaugh et al. 2011a and others). Fires are usually low in intensity overall, consuming only shrubs and herbs, but will occasionally kill patches of young pine regeneration and rarely kill individual older trees. Historically, individual fires covered extensive areas. This high fire frequency is dependent on the presence of fine fuels in the form of grasses and pine leaf litter. This ecological system is also affected by hurricane and tornado occurrences every 200 +/- years. In mature stands, competition between pine and hardwood trees is also a factor in maintaining species composition.

This ecological system is much reduced form its original extent. Today, only 10 to 25% of this system remains in Louisiana (Smith 1993). The primary historic threat was conversion to other forest types or agriculture including forest plantations (LDWF 2005). A primary threat to current occurrences of this ecological system is alteration of the natural fire regime. With longer fire-return intervals, this system quickly becomes invaded by fire-sensitive woody species common in the nearby forest systems. An increase in cover of off-site woody species can suppress the regeneration and growth of species typical of this system in its natural state. 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. Pinus palustris woodlands have also declined due to conversion to intensively managed pine plantations. Longleaf pine forests were among the most valuable economic resources in the region at the turn of the twentieth century (Bray 1906). Overall losses of longleaf pine in Texas have exceeded those of all other southern states (Outcalt 1997); less than 16,200 hectares of mostly second-growth stands remain (McWilliams and Lord 1988). Land use practices continue to degrade remaining examples of longleaf pine communities (Bridges and Orzell 1989a).

The natural range of this system is in the coastal plains of western Louisiana and eastern Texas. Its boundary follows TNC Ecoregion 41 (West Gulf Coastal Plain) closely in western Louisiana, but extends slightly into Ecoregion 40 (Upper West Gulf Coastal Plain) in eastern Texas.