Central and South Texas Coastal Forest

This ecological system includes oak-dominated forests woodlands, shrublands and savannas occurring on deep sands of the Pleistocene-aged Ingleside barrier-strandplain of the central Texas coast and the Holocene-aged eolian sand deposits of the South Texas Sand Sheet. Topography varies from larger dunes to smaller ridges and swales. Vegetation of this physiognomically variable and dynamic system primarily includes patches (mottes) of forests, woodlands and shrublands dominated by Quercus fusiformis. Associated species vary in a north/south manner across the range of this system. Some examples contain dense shrublands dominated (almost to the exclusion of other species) by running clones of Quercus fusiformis. Other canopy species in the vicinity of Aransas National Wildlife Refuge, at the northern end of the range, include Quercus marilandica, Quercus hemisphaerica, Persea borbonia, and Celtis laevigata. In this area, understory species include Ilex vomitoria, Smilax bona-nox, Vitis mustangensis, and/or Morella cerifera. Other canopy species on the South Texas Sand Sheet, at the southern end of the range, include Prosopis glandulosa var. glandulosa, Zanthoxylum hirsutum, Condalia hookeri, Lantana urticoides, Ziziphus obtusifolia var. obtusifolia, and a very few other species. Many of the species found in the northern parts of the range of this system are absent in the southern occurrences. Quercus fusiformis - Prosopis glandulosa var. glandulosa / Malvaviscus arboreus var. drummondii Forest (CEGL007785) can be referred to the southern expression, while Quercus fusiformis - Persea borbonia Forest (CEGL002117) represents the northern expression. A characteristic component of the sparse ground cover within the mottes and forests across the entire range is Malvaviscus arboreus var. drummondii. Canopy openings are similar in composition to surrounding grasslands. In addition to Schizachyrium littorale, other herbaceous species common in canopy openings across the range of this system include Paspalum plicatulum, Paspalum monostachyum, Andropogon gerardii, Sorghastrum nutans, Muhlenbergia capillaris, Helianthemum georgianum, Croton argyranthemus, and Froelichia floridana. Minor changes in drainage can cause major differences in species composition. On the Ingleside barrier-strandplain, while Paspalum monostachyum may dominate slightly lower areas, deeper swales are typically dominated by Panicum virgatum, Spartina patens, Fimbristylis spp., Hydrocotyle bonariensis, Rhynchospora spp., Fuirena spp., Eleocharis spp., and Cyperus spp.

Vegetation of this physiognomically variable and dynamic system is dominated by Quercus fusiformis. Stands primarily consist of patches (mottes) of forest, woodland and shrubland in a matrix of more open savannas and grasslands. Closed canopy mottes typically occur within a grassland matrix but may become more extensive forests. In the northern range of this system, other canopy components may include Quercus marilandica, Quercus hemisphaerica, Persea borbonia, and Celtis laevigata. In this area, understory species include Callicarpa americana, Ilex vomitoria, Smilax bona-nox, Vitis mustangensis, and Morella cerifera. Characteristic components of the sparse ground cover within the mottes and forests include Malvaviscus arboreus var. drummondii, Scleria triglomerata, and Erythrina herbacea. A shrubland component of this system is also present in some areas and is sometimes extensive, consisting of a rhizomatous expression of sprouting live oaks referred to locally as "running live oak." This shrubland often appears to be a monoculture of shrubby Quercus fusiformis (1.5-6 m tall), but other species of the oak motte are also found here, including larger Quercus fusiformis trees, Quercus hemisphaerica, Persea borbonia, Morella cerifera (usually in swales), Toxicodendron pubescens, Callicarpa americana, Vitis mustangensis, Ilex vomitoria, Erythrina herbacea, and scattered Quercus marilandica. Small openings with Sorghastrum nutans hint at what is thought to have been the historical condition of these areas. These "running-live oak" thickets are thought to be a modified community that is the result of years of fire suppression and severe grazing pressures. Once this shrubland is established, it is difficult to restore the grassland community to these areas. Canopy openings are similar in composition to surrounding grasslands. In addition to Schizachyrium littorale and Paspalum monostachyum, common components include Heteropogon contortus, Paspalum plicatulum, Trichoneura elegans, Andropogon gerardii, Sorghastrum nutans, Bothriochloa saccharoides, Muhlenbergia capillaris, Dichanthelium spp., Elionurus tripsacoides, Eriogonum multiflorum, Stylosanthes viscosa, Helianthemum georgianum, Croton glandulosus, Paspalum setaceum, Tradescantia humilis, Physalis cinerascens var. spathulifolia, Palafoxia hookeriana, Scleria triglomerata, Thelesperma nuecense, Lechea mucronata, Liatris elegans var. carizzana, and Froelichia floridana. The oak mottes may have expanded at the expense of the oak savanna phase and become more dense in the absence of fire. A maritime component occurs on stabilized dunes composed of deep sand that stretch along San Antonio Bay. This component is characterized by a relatively tall forest (8-12 m) dominated by Quercus fusiformis. Other trees that reach the canopy include Persea borbonia and Quercus hemisphaerica. The midcanopy is dominated by Persea borbonia and Quercus hemisphaerica with Celtis laevigata and Quercus marilandica occurring as occasional associates. The understory includes Ilex vomitoria and Callicarpa americana. A characteristic member of the sparse ground layer is Scleria triglomerata. [continued in Other Comments]

This system occurs on deep sands of the Pleistocene-aged Ingleside barrier-strandplain and the Holocene- and Pleistocene-aged eolian sand deposits of the South Texas Sand Sheet. Ridge and swale topography characterizes these sites, with some large (up to 15 m tall) vegetated dunes present. Topography varies from larger dunes to smaller ridges and swales.

Fire, climate, and edaphic factors all likely played a role historically in maintaining a more open structure in this vegetation. Historically, fire likely limited the development of woody cover. Likewise, edaphic conditions limited this system to deep sandy soils. Loss of these natural processes often results in a shift toward a more closed canopy and decrease in native grass cover. Threats to this system include fire suppression, coastal development, invasive exotics, and damage by vehicles.

This system is endemic to Texas. It is found within 10 km of the coast on deep sands of ancient Pleistocene strandplains (the Ingleside barrier-strandplain) at its northern extent and within a much greater distance from the coast (100 km) on the Holocene-aged eolian sand deposits of the South Texas Sand Sheet (primarily Kenedy and Brooks counties but extending into adjacent Jim Hogg, Hidalgo, and Willacy counties) at its southern extent.