«Recreation Plan Recreation Grants Branch State Parks Division 4200 Smith School Road • Austin, Texas 78744 © 2012 TPWD. PWD ...»
Consistent with the intent of the TWCP, a number of self-directed, regional conservation partnerships (e.g., Bird Joint Ventures, Fish Habitat Partnerships, Estuary Programs) have developed strategic conservation plans that identify priority wetlands conservation strategies and actions. This chapter has been added to the TORP to facilitate implementation of these regional strategic conservation plans and the TWCP, and to align regional wetlands restoration and protection priorities in Texas with resources available through the LWCF Program.
Applications submitted to the Outdoor Recreation Grant program (which disperses LWCF grants) are given priority points if the project provides for the acquisition and preservation of a significant wetland area. Wetlands recognized in an acceptable, published planning document, such as the strategic wetlands conservation plans referenced in this chapter, may qualify for additional priority points.
Texas Wetlands: Regional Descriptions Although wetlands comprise less than 5% of the total land area of the state, Texas has the fourth greatest wetland acreage in the conterminous United States (Dahl, 1990) and contains a diversity of wetland types, including swamps, bottomland hardwood forests, marshes, bogs, springs, resacas, cienegas, riparian areas, playa lakes, and saline lakes. The conservation strategies identified in the TWCP are designed to be uniquely focused on the specific wetland types and regions of the state. Please find the wide variety of diverse wetlands described below by region.
Texas Outdoor Recreation Plan Chapter 3 – Texas WetlandsEast Texas East Texas contains a mosaic of wetland types including forested wetlands, shrub swamps, marshes, oxbow lakes, and bogs. Forested wetlands (Photo 1), the most common wetland type in East Texas, are dominated by bottomland hardwood trees that grow in creek and river floodplains. In floodplains, the ebb and flow of floodwater shapes the forest floor into ridges, swales, or flats. These elevational differences influence the duration of flooding or soil saturation, which, in turn, affect the type and abundance of plants that can grow. As a result, bottomland hardwood forests contain a diversity of trees, shrubs, herbaceous species, and vines that grow together in different vegetation assemblages depending on soil type, water depth, velocity, and flood duration.
Photo 1. Bottomland hardwood forest in east Texas, © TPWD.
Bottomland hardwood forests buffer water, one of our most precious resources, from human activities. Bottomlands anchor soil, prevent soil loss from scouring, and filter various pollutants from water (Wharton, 1980). Pesticides readily adhere to clay and organic particles, and floodplains are sinks for oil, nitrogen, phosphorus, sewage, fly ash, and other particulates.
Bottomlands are open, productive systems that receive supplements from soil and organic matter upstream (Wharton, 1980). Bottomland productivity supports abundant fauna in that system and is crucial to biological production in downstream estuarine systems.
Bottomland hardwood communities in Texas support over 180 species of woody plants, including bald cypress (Photo 2), water oak, willow oak, overcup oak, water hickory, green ash, pecan, possumhaw, buttonbush, planertree, and swamp privet.
Chapter 3 – Texas Wetlands Texas Outdoor Recreation Plan Characteristic herbaceous species include smartweeds, arrowhead, sedges, cutgrass, arrow arum, lizard’s-tail, spiderlilies, and bladderworts. Animals found in forested wetlands include wood ducks, mallards, eastern wild turkeys, swamp rabbits, gray and fox squirrels, raccoons, river otters, beavers, red-eyed vireos, alligator snapping turtles, and cottonmouth water moccasins.
Shrub swamps are dominated by water elm (also known as planertree), buttonbush, and swamp privet. These plants often grow in dense stands with sparse herbaceous understory. Standing water or saturated soils are typically present throughout the year.
Freshwater marshes (Photo 3) contain extensive stands of cutgrass, a perennial species, in deeper portions of the marsh. Other perennial plants occupying the adjacent shallower areas include several smartweed species, arrow arum, soft rush, spikerushes, arrowhead, maidencane, and plumegrass. Numerous submergent species are found in deeper open water pools. Cutgrass marshes are seldom dry.
Historically, during extreme, infrequent droughts, prolonged fires burned the organic peat soils of cutgrass marshes. These fires reduced or eliminated the dense herbaceous cover, which temporarily favored the growth of many annual plant species.
East Texas bogs, found in association with bottomland hardwood forests, occur when bowl-shaped terrain features restrict water drainage. These systems are usually wet year round because of continuous groundwater seepage. Acidic conditions and poor soil aeration support plant communities containing a variety of specialized species, including carnivorous plants such as sundews and pitcher plants (Photo 4). Other plants include red maple, wax myrtle, alder, bladderworts, orchids, ferns, and irises. Species composition is best maintained by periodic prescribed burns to control woody plants.
The Gulf Coast contains a diversity of salt, brackish, intermediate, and fresh wetlands, including wet prairies, forested wetlands, barrier islands, tidal flats, estuarine bays, bayous, and rivers. Coastal prairies also contain rice fields, which can provide excellent wintering waterfowl habitat. Saline and brackish marshes (Photo 5) are most widely distributed south of Galveston Bay, while intermediate marshes are the most extensive marsh type east of Galveston Bay.
The lower coast has only a narrow band of emergent marshes, but has a system of extensive bays, lagoons, and small near-shore ponds, which are critical freshwater sources to diving ducks that feed in saline and hypersaline lagoons. Rainfall along the coast varies from 65 cm on the lower coast to 139 cm on the upper coast (Texas Department of Water Resources, 1984). The existence and extent of specific plant species within these different wetland types depends on their tolerances to fluctuating salt concentrations and variability in water depth. Some overlap of species can be found within the different wetland types on the Gulf coast.
Photo 5. Saline marsh on the Texas coast, © TPWD.
Submerged aquatic vegetation (primarily seagrasses, Photo 6) grows in permanently inundated areas ranging from highly saline to brackish waters, but thrives in shallow subtidal areas of less than six feet. Most submerged aquatic vegetation, including shoalgrass, widgeongrass, manatee grass, clover grass, and turtle grass, is found in the Lower Laguna Madre. Because submerged aquatic vegetation is found below the mean high-tide line, most areas are state-owned (Texas General Land Office, 1997).
Texas Outdoor Recreation Plan Chapter 3 – Texas WetlandsPhoto 6. Submerged aquatic vegetation in the Lower Laguna Madre, © TPWD.
Tidal flats are located in the intertidal zone and are consistently exposed and flooded by tides. Tidal flats, characterized by sand, silt, and clay, have minimal vegetation but are important feeding grounds for coastal shorebirds, fish, and many invertebrates including crabs, oysters, clams, shrimp, and mussels. Texas contains more tidal flats than any other state and houses 23% of the nation’s total (Texas General Land Office, 1997).
Salt marshes (average salinity 18 ppt) have the greatest tidal fluctuation of all marsh types. Soils have a lower organic content than fresher types located further inland (Chabreck, 1972). Salt marshes contain relatively few plant species and are characterized by Spartina alterniflora (smooth cordgrass), a species that depends on regular water fluctuations. Behind this zone may be saltgrass, needle rush, blackrush, saline marsh aster, saltwort, glasswort, and sea lavender.
Brackish marsh communities are transitional between saline and intermediate marshes (average salinity 8.2 ppt). They are still subject to daily tidal influence. Marsh soils have a higher organic content than salt marshes, and water levels are also higher. Brackish marshes contain numerous small bayous and lakes. Dominant species include marshhay cordgrass, saltgrass, saltmarsh bulrush, Olney bulrush, and widgeon grass (Chabreck et al., 1989).
Intermediate marshes (average salinity 3.3 ppt), somewhat tidally influenced, have greater plant diversity than saline or brackish marshes (Chabreck et al., 1989). Species found here include seashore paspalum, marshhay cordgrass, Olney bulrush, arrowheads, common reedgrass, coastal water-hyssop, bearded sprangletop, pondweeds, and naiad.
Chapter 3 – Texas Wetlands Texas Outdoor Recreation Plan Fresh marshes support the greatest diversity in plant species of all marsh types. They are normally free from tidal influence, exhibit slow drainage, and have the highest soil organic content of coastal wetlands (Chabreck et al., 1989). Dominant vegetation includes maiden cane, giant cutgrass, American lotus, white water-lily, smartweed, marsh millet, arrowhead, seedbox, coontail, alligator weed, and many others.
Coastal prairies, often called “rice prairies” because of the current land use, generally extend from the coastal marshes to as much as 75 miles inland. The former tall grass prairies (Andropogon spp.) dotted with shallow, ephemeral prairie wetlands (called potholes) and meandering bayous, creeks, and rivers were replaced by agricultural fields, especially following World War II, in response to an increased market demand for rice and other crops (Stutzenbaker and Weller, 1989).
Those wetlands that were not drained or “land-leveled” for enhanced crop production were often drained to eliminate potential hazards for cattle or to improve grazing conditions during wet cycles (pers. comm. With David Curtis, 1997). Today’s rice and grain fields that are flooded during the fall and winter receive heavy waterfowl use, especially by pintails, mallards, geese, and many wading birds (Gulf Coast Joint Venture Management Board, 1990).
Texas coastal wetlands are an important wintering and migration area for North American waterfowl. Other birds of special concern, such as the bald eagle, peregrine falcon, brown pelican, and whooping crane, all depend on Texas marshes and estuaries, as do otter, alligator, swamp rabbit, furbearers, and amphibians. Texas coastal marshes and estuaries provide productive nurseries/ spawning areas and habitat for seafood species and other marine organisms.
South Texas freshwater or brackish wetlands include small, isolated depressions, or potholes, and resacas, which are relic meanderings of the Rio Grande River. Coastal potholes, formed when clay soils exposed by wind action trap and hold water, often supply the only fresh water for resident wildlife in an area generally devoid of creeks and rivers. Potholes depend on rainfall or underground water sources. High evaporation rates and temperatures may cause potholes to retain water only temporarily or seasonally. The potholes are primarily located in the counties of Cameron, Hidalgo, and Willacy of the Lower Rio Grande Valley and in the sand plains of South Texas, near the coast in Kennedy, Kleberg, and Willacy counties (Witten and Zemites, 1989). Potholes are also found north of Corpus Christi but tend to be smaller, shallower, and more ephemeral (pers. comm. with David Curtis, 1997).
The vegetation composition of potholes depends upon the amount of water available.
Non-permanent wetlands contain both wetland and upland species. Common wetland vegetation includes duckweed, saltmarsh spikerush, common cattail, and smartweed.
Upland vegetation associated with coastal potholes includes live oak, wax myrtle, plantain, silverleaf sunflower, and panic grass. Many animal species depend on wetland
Texas Outdoor Recreation Plan Chapter 3 – Texas Wetlandsvegetation for cover, and for nesting and resting. Coastal potholes are wintering grounds for waterfowl, shorebirds, songbirds, waders, and several species of mammals, fish, and invertebrates. Coastal brushland potholes may also be prime habitat for threatened and endangered species such as the ocelot and jaguarundi.
In the lower Rio Grande Valley, oxbows or resacas are common. Resacas are former streambeds that are subject to repeated drying and flooding, thus forming long quiet ponds. Vegetation associated with resacas includes retama and huisache.
Resacas thrive on periodic inundation from river flooding. However, levees, floodways, and reservoirs, along with irrigation diversion, have virtually eliminated flood flows to resacas, which are no longer scoured and flushed. Siltation has become a major problem within the resacas due to the absence of scouring and the increase in urban runoff, shoreline erosion, and general degradation of water quality (Ramirez, 1986).
The High Plains and Rolling Plains of the Panhandle support wetlands predominantly in playa lakes and saline lakes (High Plains), and in water-table influenced basins and riparian habitats (Rolling Plains). Playas (Photo 7) are ephemeral wetlands characterized by Randall or Ness clays, and are very similar to coastal potholes, but have a different geologic origin. Saline lakes are generally larger than playas, are very saline, and are influenced by groundwater. A few playas and playa-like basins with connections to groundwater occur in the Rolling Plains.
Riparian wetlands include vegetation along main channels of creeks and rivers and associated wet meadow, perched water table lakes, and beaver pond habitats. Riparian wetlands in the Panhandle are characterized by Plains cottonwood, netleaf hackberry, buttonbush, native plum, western dogwood, and persimmon. Salt cedar and Russian olive have both been introduced in the last fifty years and have changed the character and successional characteristics of these riparian systems (Brinson et al., 1981).
Photo 7. The Texas sunset illuminates playa lakes in the panhandle, © TPWD.