Upper Texas Coast Shell Ridge Forest

This system includes a range of woody vegetation typically dominated by Quercus virginiana present along the northern Gulf of Mexico, from Vermillion Bay in Louisiana to the upper Texas coast. Landscape position includes shell ridges along the coast and bay margins, coastal salt domes, stranded ancient barrier ridges (Ingleside barrier strandplain), and chenier ridges of the Chenier Plain. In addition to Quercus virginiana, other species such as Celtis laevigata and Quercus nigra may be present to codominant in the canopy which may also include Carya illinoinensis, Diospyros virginiana, Fraxinus pennsylvanica, Liquidambar styraciflua, and Magnolia grandiflora.

Typically these forests and woodlands are dominated by Quercus virginiana; however, other species such as Celtis laevigata and Quercus nigra may be present to codominant in the canopy. Other species such as Liquidambar styraciflua, Carya illinoinensis, Diospyros virginiana, Fraxinus pennsylvanica, and Magnolia grandiflora may also be present in the canopy. The understory is often patchy but may include species such as Ilex vomitoria, Callicarpa americana, Zanthoxylum clava-herculis, Crataegus viridis, Sabal minor, Morella cerifera, and/or Sideroxylon lanuginosum. Woody vines present in this system include Vitis mustangensis, Parthenocissus quinquefolia, Campsis radicans, and Toxicodendron radicans. The two epiphytes Tillandsia usneoides and Pleopeltis polypodioides may be commonly encountered. The herbaceous layer is usually sparse, but may include species such as Schizachyrium scoparium, Sanicula canadensis, Malvaviscus arboreus var. drummondii, Elephantopus carolinianus, and Oplismenus hirtellus. Triadica sebifera and Ligustrum sinense may be important non-native invaders (Elliott 2011).

This system occupies sand and shell ridges (Quaternary deposits) which resulted from ancient abandoned beach ridges associated with migrating shorelines, shell ridges, as well as salt domes near the coast. The Ingleside barrier strandplain, an ancient barrier ridge composed of deep sands and occurring well inland of the current Gulf shoreline, may support occurrences of this system. Most occurrences occupy ridges formed from sediments deposited along ancient shorelines. These ridges (cheniers), which often parallel the coast and are composed of coarse material such as sand or shell, may be up to 3 m above mean sea level. Some occurrences occupy coastal salt domes, which may rise 30 m above the surrounding landscape. The soils are typically Entisols of coarse-textured material, either sand or shell. The Ecological Site Description, which may be related to this system, is the Coastal Sand ecoclass (Elliott 2011).

This ecological system is heterogeneous in physiognomy, including forests, woodlands and shrublands. The Chenier Plain was historically characterized by a prograding coastline replenished by sediments carried to the Gulf of Mexico initially by the Mississippi and subsequently the Atchafalaya and other rivers. It is void of barrier islands and sediments are reworked by waves into beach ridges, sometimes with a substantial shell component. This process has been continuing since the last glacial retreat, and as the coastline prograded, older beach ridges were left as interior ridges surrounded by marsh. These interior beach ridges are referred to as cheniers (from the French word for oak) because they were historically dominated by Quercus virginiana. Ridges parallel the coast and are usually 3-5 m above mean sea level. Though not confined to coastal areas, salt domes are a distinctive feature along the Gulf Coast of upper Texas and Louisiana where they often form a drastic contrast to the low-lying Coastal Plain sediments surrounding them. Formed by the rise of salt masses which push up overlying strata, salt domes may rise 30 m above the surrounding landscape. The natural vegetation of cheniers and coastal salt domes are quite similar. The Ingleside barrier strandplain is a Pleistocene barrier ridge that is exposed discontinuously along the Texas coast. One of these areas is located northeast of Galveston Bay and supports Quercus virginiana-dominated woodlands included within this ecological system. Shell ridges located along coast and bay margins are typically dominated by halophytic shrubs. Similar vegetation may also be found on coastal dredge spoil. Vegetation structure and composition of occurrences of this system may be influenced by salt spray (on those shell ridges, salt domes and cheniers closest to the gulf), tropical storms and hurricanes, and the distinctive climate of the immediate coast. Studies have shown that chenier forests and woodlands are very important stop-over sites for neotropical migrants during both spring and fall migration.

The primary threats to this ecological system are clearing and conversion to other land uses such as pasture, residential development, and infrastructure, sand mining, invasive species such as Triadica sebifera, and the reduced formation of new beach ridges (Neyland and Meyer 1997). Only 2 to 10% of the presettlement occurrences of this system remain in Louisiana (LDWF 2005) and these fragmented remnants are further impacted by overgrazing and invasive species. Very little of this system is under conservation ownership (LDWF 2005).

This ecological system is found in small patches along the northern Gulf of Mexico, from Vermillion Bay in Louisiana to the upper Texas coast.