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South Texas Plains
This is a region characterized by considerable variety. Climatically, the South Texas Plains region is
sub-humid to dry. The in the north part of the South Texas, erosion of the Edwards Plateau can
be seen in the soil. The area is characterized by black soils that extend from Austin to San Antonio
and thence westward, although discontinuously, to Uvalde. Those areas having typical black-earth
soils are highly important for farming purposes. Areas closer to the coastal region have layers of
sand that are stabilized by grasses, shrubs, and mesquite trees. Farther south, lower Rio Grande
country, consisting of a smooth to very slightly rolling upland of black-earth soils and the lowland
of the Rio Grande River, including its delta area.
The area is home to native grasses and shrubs that survive in the semi-dry climate. Hunting is
popular in this area due the large herds of deer that graze on the grasses and shrubs. South Texas
Plains has more biodiversity than any other ecoregion in Texas. Hundreds of species of birds live
in the South Texas Plains. The Rio Grande Valley in the southern portion of the South Texas Plains
is home to many subtropical species of animals due to its humid climate.
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Post Oak Savannah
The original savannahs in the northern part of the Oak-Prairie region were characterized by native grasses
such as little bluestem, silver bluestem, and brownseed paspalum with scattered clumps of trees. Post oak
trees dominated, but other species included blackjack oak, water oak, winged elm, hackberry, and yaupon.
The most striking change to the savannah has been the loss of the native range grasses from overgrazing and
the clearing of the native range to plant other grasses, such as coastal Bermuda grass, for cattle. The rich
diversity of grasses and weeds in the native savannah provided food and cover for many wildlife species and
the planning of the new grasses is responsible for the decline and even disappearance of species such as the
bobwhite quail in much of the area.
The Coyote is an extremely intelligent animal with keen senses of hearing, sight and smell. Coyotes will eat
just about anything. They feed primarily on rabbits, rodents and insects, but they also eat lizards, snakes, fruit,
vegetable matter and even fish. This adaptability also is evident in their use of cover. The Coyote requires
minimal shelter to survive, but it will use a den for the birth and care of its young.
The terrain is nearly level to gently rolling with elevations. The Post Oak Savannah landscape was formed and
maintained by two major forces: frequent fire and grazing of bison. Recurrent fires ignited either by lightning
or humans (American Indian) were the major force that molded the prairie and savannah landscapes.
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Cross Timbers
The terrain in most of this region is very hilly, with sandstone and limestone escarpments, steep slopes, and
irregular surface features. Watersheds of the Red, Colorado, Trinity and Brazos Rivers cross the region from
northwest to southeast. Exposed sandstone rocks and boulders dominate landscape features in many areas.
The cross timbers region provides habitats for white-tailed deer, Rio Grande turkey, bobwhite quail,
fox squirrels, and rabbits. Post oak-blackjack oak woodlands characterize much of the cross timbers
region. Other associated woody species include Spanish oak, live oak, Texas ash, mesquite, Ashe
juniper, cedar elm, skunk bush, rough-leafed dogwood, flame-leaf sumac, hawthorn, and hackberry.
Texas, Our Texas
RM 3
Average Annual Temperatures of Texas for January
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RM 4
Average Annual Temperatures of Texas for July
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RM 5
Average Annual Precipitation of Texas (1961–1990)
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RM 6
Dominant Soils of Texas
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RM 7
The Piney Woods
Big Thicket Pine
Palmetto Leaf
Many parts of this ecoregion are characterized by longleaf pine forests on rolling sandy
uplands. A variety of broad-leaved plants, shrubs, and grasses grow in this ecoregion of
Texas. Photos: National Park Service
Bald Cypress Marsh
Neches River
The Big Thicket national preserve is part of the Piney Woods. There are over 85 species of
trees, 1,000 flowering plants, and over 180 kinds of birds in the Big Thicket.
Photos: National Park Service
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RM 7 continued
Gulf Coast Plains and Marshes
Barrier Island
Barrier islands, peninsulas, marshes, and flat plains characterize this ecoregion. Sixty
percent of the Texas Gulf Coast shoreline erodes from 30 cm to 15 m per year. Photo: U.S. Army
Corps of Engineers
Rosette Spoonbills
Whooping Cranes
The western part of the Gulf Coast Plain is one of the most biologically diverse regions of
Texas. Nearly 500 species of resident and migratory birds have been recorded in the Texas
coastal region. Photo: U.S. Army Corps of Engineers
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RM 7 continued
Edwards Plateau/Llano Uplift
Enchanted Rock
Canyonlands
The Llano Uplift is located within the Edwards Plateau ecoregion. It is sometimes referred to as the
Hill Country. Domelike rock formations of exposed pink granite are located in this region. Unique
plant communities are often found on these domes. An example of this type of rock formation is
the Enchanted Rock.The southeast portion of the Edwards Plateau is an area of canyonlands. A
diversity of plants can be observed in this area, including deciduous forests, grasses, mesquite
trees, and wildflowers. Photos: Texas Parks and Wildlife
Mexican Free-Tailed Bats
Texas Blind Salamander
Mexican free-tailed bats, the Texas blind salamander, and the golden-cheeked warbler are just a few
of the unique animals that can be observed in the region. Cool, clear springs and streams provide
water for the vegetation and wildlife. Photos: Texas Parks and Wildlife
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RM 7 continued
High Plains
Playa
Prairie Dog
This ecoregion usually receives less than 20 inches of precipitation per year. Seasonal
lakes called playas are found in this ecoregion. These lakes are filled with salts due to
the erosion of nearby hills by rainwater. Playas are key sites of biodiversity. They provide
important habitats for ducks, geese, sand hill cranes, shorebirds, amphibians, and small
mammals. Photo: Loren M. Smith, Texas Tech University
Palo Duro Canyon
The Palo Duro Canyon is the second largest canyon in the United States. It was formed by
water erosion of the Prairie Dog Town Fork of the Red River.
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Texas, Our Texas
RM 7 continued
Trans Pecos/Chihuahuan Desert
Croton Peak
Roadrunner
Blooming Cactus
Grasslands
The area generally west of the Pecos River in Texas is often called the Trans-Pecos. It occupies the
northern part of the Chihuahuan Desert, which extends south nearly 500 miles into Mexico. Shown
here is Croton Peak in the northern part of Big Bend National Park. Roadrunners are well-adapted
to desert habitats of the Southwest. They eat insects, spiders, snails, lizards, and some fruits
and seeds.
The Trans Pecos ecoregion has diverse topography. It includes desert flats and valleys, plateaus,
sand hills, and mountain ranges. Grasslands, shrub lands, cactus savannas, and mountain
woodlands also occur. Photo: Michel Farhi
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