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NWRC Coastal Prairie Research Program

The Coastal Prairie Region

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Texas and Louisiana prairiesThe coastal prairie region refers to the habitats that occur within the western gulf coast area and includes the coastal prairie grasslands as well as adjacent and included coastal wetlands and gallery forests . Ecological conditions within the coastal prairie region vary from the coast inland and from east to west with major gradients in hydric, saline, and climatic features. Additional references on the features of this region can be found in the general bibliography.

Located along the western gulf coast region of the United States, just inland from the coastal marsh, is the coastal prairie. The coastal prairie is a type of tallgrass prairie and is similar in many ways to the tallgrass prairie of the Midwest United States. This ecosystem once extended from Corpus Christi,TX, to its eastern limit at the margin of pine savanna along a north to south line running from Opelousas to Lafayette, LA (see map). The portion in southwest Louisiana is often called the "Cajun prairie" because it was settled in the early 19th century by exiled Acadian settlers. The Cajun prairie originally extended from a narrow 11-mile (17.7 km) wide neck at the Sabine river and widened to its eastern limit. It is estimated that, in presettlement times, the Cajun prairie encompassed as much as 2.5 million acres of land. The Texas portion of the coastal prairie is estimated to have included about 6.5 million acres of habitat that extended in a band along the coast immediately inland from the marsh.

Today, substantially less than one tenth of a percent of the coastal prairie remains in a relatively undisturbed condition. The remaining 99.9 percent has been nearly eliminated for agriculture and development. While much of the former prairie has been converted to pasture for cattle grazing, the vast majority has been altered for the culture of rice and sugarcane. In Louisiana, the few remaining remnants of original upland prairie are found only on narrow strips of land along railroad tracks. Much more coastal prairie remains in southeast Texas; however, much of this prairie has lost species of grasses and wildflowers because of grazing.

The factors that contribute to the establishment and maintenance of prairie are rainfall, soil type, fire, and herbivory. Drought, fire, and competition from adapted grass and forb species combine to prevent the establishment of woody plants and maintain the grass-dominated ecosystem. Many prairie species depend on fire for seed set, satisfying seed dormancy, and the removal of accumulated biomass. Drought can occur in areas of low rainfall (west to central Texas), and in areas of high rainfall as a result of root restriction by a soil hard pan or by low water availability in heavy clay soils during dry summers (east Texas to Louisiana).

Bison on a prairieGrazing (historically by bison (Bison bison and elk (Cervus) and now by cattle) affects vegetation dynamics by stressing grazed species, satisfying seed dormancy by partial digestion, and by creating disturbances which allow recruitment by opportunistic species. The scarcity of big bluestem (Andropogon gerardii), Indiangrass (Sorghastrum nutans) eastern gamagrass (Trypsacum dactyloides) and many wildflowers in Texas prairie remnants may be due to overgrazing by cattle. Palatable native grasses such as big bluestem, Indiangrass and eastern gamagrass cannot tolerate the close grazing of cattle but are adapted to the fast moving, tip nipping of bison. Foreign species, such as Vasey grass (Paspalum urvillei), from South America, and Johnsongrass (Sorghum halepense), from the Mediterranean, which are adapted to cattle grazing, flourish in overgrazed prairie.

Natural prairie is dominated by long-lived perennials which form a dense mat of intertwined roots. With the exception of partridge pea (Cassia fasciculata), false foxglove (Agalinis sp.) and a few others, annuals are rare in undisturbed prairie sod. In Midwestern tallgrass prairie, disturbances are rapidly recolonized vegetatively by surrounding plants. Seed is thought to be only of occasional importance in the recruitment of species to new areas of prairie. It is not yet clear what role seed recruitment plays in the coastal prairie.

Despite the small size of the Cajun (Louisiana) prairie remnants, they contain a high diversity of native tallgrass prairie flora. Big bluestem, Indiangrass, and switchgrass (Panicum virgatum) dominate these remnants just as they dominate the prairie of the Midwest. Because coastal prairie grades into coastal marsh the southern most prairies often have shallow standing water and are often dominated by switchgrass and eastern gammagrass.

Eryngium yuccifolium pictureMany wildflowers common on prairies of Iowa and Illinois are also found on the Cajun prairie. An obligate prairie species in our area, Eryngium yuccifolium (see picture at right), is a noted indicator of moist prairie from Minnesota to Texas. Eryngium yuccifolium is very common in Cajun prairie as are such northern prairie species as Kansas gayfeather (Liatris pycnostachya) and blackeyed susan (Rudbeckia hirta).

Traveling west into the coastal prairie of Texas, western species appear such as sideoats gramma (Bouteloua curtipendula), prairie coneflower (Ratibida columnaris), and small patches of prairie cordgrass (Spartina pectinata).  Near the Texas coast prairie grades into high salt marsh, producing a unique prairie type called salty prairie, dominated by gulf cordgrass (Spartina spartinae). These Texas remnants face the same problems as those in Louisiana: many of the unique areas of prairie are being destroyed by development.

While the coastal prairie contains a great deal of vegetation common with the central and northern "true prairie," there are some plants in the coastal prairie community that are only found in this system. One such endemic is the prairienymph (Herbertia lahue var. cerulea). The prairienymph is a member of the iris family and is fairly common in the prairies of Texas though rare in the adjoining Cajun prairie. Its rarity may be due to the severe loss of habitat in Louisiana and possibly also from a reduction of native pollinators.

Chinese Tallow (Triadica sebiferum)Other southern prairie natives ashy sunflower (Helianthus mollis) and  slender bluestem (Schizachyrium tenerum) also occur in long-leaf pine understory of Southern states.  Brown-seed paspalum (Paspalum plicatulum), restricted to coastal states can be a dominant in wet prairies of Texas and Louisiana, possibly because it is an increaser on sites with heavy grazing.

Among the most serious problem facing prairie remnants and restorations is invasion by exotic plants. Two of the most problematic invaders are Macartney rose (Rosa bracteata) and Chinese tallow tree (Triadica sebiferum). Both species rapidly invade abandoned farm land and also easily colonize overgrazed fields. While their ability to colonize intact prairie is apparently slow, it does occur over time. These invading species are root sprouters, giving them the ability to readily management by early spring fire.  Annual growing season burns appear can be effective if sufficient fuel and burn conditions exist.

Chinese Tallow forestThere has also been a proliferation of native woody plants such as eastern baccharis (Baccharis halimifolia) and wax myrtle (Myrica cerifera) in the absence of fire. Where fire has been reinstated as a management tool, Baccharis infested prairies recover with little loss of diversity.  However, in prairies reclaimed from Chinese tallow infestations, herbaceous communities do not recover.  When fire management is applied to native prairies with a history of heavy grazing, herbaceous ground cover lack the plant diversity typical of remnant prairies. These reclaimed prairies, chiefly in Texas, are composed primarily of little bluestem (Schizachyrium scoparium) and very few other grasses or wildflowers. Methods for reintroducing grasses and forbs to depauporate remnants and restorations are needed.

Prairie restoration is gaining interest in parts of Texas and Louisiana as well as in parts of the Midwest. Methods vary between geographical areas and individual restorationists, and success varies from year to year. Planting a restoration involves (1) preparation by herbicide, solarization, or tillage; (2) planting by haying, seeding, sodding, or transplanting; and (3) management by mowing, irrigation, grazing, and fire. The best time for planting varies based on location and method.

There are no simple answers to the question of how we may best preserve a diverse and functioning coastal prairie. Restoration on public land and by concerned citizens on private land and continued research on restoration technology, ecosystem health and control of invasive exotics are crucial if this most endangered community type is to be preserved.

Tallow trees burningPrairie restoration is gaining interest in parts of Texas and Louisiana as well as in parts of the Midwest. Methods vary between geographical areas and individual restorationists, and success varies from year to year. Planting a restoration involves (1) preparation by herbicide, solarization, or tillage; (2) planting by haying, seeding, sodding, or reintroduction; and (3) management by mowing, irrigation, grazing, and fire. The best time for planting varies based on location and method.

There are no simple answers to the question of how we may best preserve a diverse and functioning coastal prairie. Restoration on public land and by concerned citizens on private land and continued research on restoration technology, ecosystem health and control of invasive exotics are crucial if this most endangered community type is to be preserved.


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