The Colorado River in the Lampasas Cut Plain of Texas
The Colorado River of the Lampasas Cut Plain (Lp) occurs in Mills and Lampasas counties in North Central Texas (Diggs et al. 1999; see figure below used with permission from authors).
The Lp and Fort Worth Prairie (Fp) comprises a large grassland with scattered woody vegetation called the Grand Prairie. Woody vegetation occurs along waterways, in scattered groves, or associated with mesas and buttes. Accounts from the mid-1800s describe the region as grasslands with fringes of timber along the Brazos River with grassland species such as prairie chickens, bison, pronghorn antelope, and wolves as well as other big game including bear and elk (Diggs et al. 1999). The Grand Prairie consists of shallow soils overlaying persistent bands of limestone (Hill 1901). The Fp portion is mainly flat plains but southward there are more rugged and dissected areas with numerous low buttes and mesas (Hill 1901). The rocky buttes
1

and mesa comprise a small fraction of the area relative to the broad sloping valleys that support grasslands (Hayward et al. 1992) with woody vegetation along bottomlands of waterways such as the Colorado River.
The upland vegetation of the Lp contains greater biodiversity than adjacent regions (see map below) due to its greater topographic diversity. Depending on the conditions present, the Lp may resemble grasslands of the Fp or be Postoak-blackjack ( Quercus stellata-Q. marilandica ) oak woodlands found in the West Cross Timbers (Wt), or vegetation similar to the Edwards
Plateau, which occurs to the south and west of the region (Diggs et al. 1999). To the west in rocky soils on and near the buttes and mesas, oaks, including Texas red oak ( Quercus buckleyi ),
Plateau live oak ( Q. fusiformis ), and shin oak ( Q. sinuata var. breviloba ), as well as sumac ( Rhus spp.) , and junipers ( Juniperus spp.) occur. In areas with deeper soils, grasses dominate and in deeper sandy soils Postoak-blackjack oak woodlands of the Wt occur. Because of fire suppression and overgrazing in the Lp, junipers are more abundant in the rocky soils and mesquite ( Prosopis glandulosa) and prickly pear ( Opuntia spp.) have become more abundant in the deeper soils (Diggs et al. 1999; Wimmer 2003). To date, little is known about the vegetation of the Colorado River Bottomlands in the Lp.
Bottomlands are considered to be the most diverse ecosystem in Texas. Prior to European settlement, Texas had approximately 16 million acres of bottomland habitat dominated by hardwoods but as of 2000, has less than 5.9 million acres (Halff Associates 2003). Bottomlands contribute to the state’s biodiversity and at least 74 species of threatened and endangered animals depend directly on bottomlands (Halff Associates 2003). Over 50 percent of Neotropical songbirds are associated with bottomlands (Halff Associates 2003). Besides providing critical wildlife habitat, bottomlands 1) serve as catchments and water retention areas in times of flooding, 2) help control erosion, 3) contribute to the nutrient cycle, and 4) play a vital role in maintaining water quality by serving as a depository for sediments, wastes and pollutants from runoff (Halff Associates 2003). Despite these important functions, bottomlands are one of the most endangered ecosystems in the United States (Halff Associates 2003).
Little is known about the bottomlands of the Lp . However, south of the region, in the
Edwards Plateau, bottomland trees along the Colorado River generally consist of bald cypress
( Taxodium distichum ), pecan ( Carya illinoensis ), oaks ( Quercus spp.), elm ( Ulmus spp.), cottonwood ( Populus deltoides ), and hackberry ( Celtis laevigata ) and most of these hardwoods are generally old growth trees between 50-100 years old (Halff Associates 2003). Since the
Colorado River is in the Central Fly zone for migratory waterfowl and other birds, the bottomlands are of great significance to the area serving as a travel route, nesting and rearing habitat, and food source for an abundant number of animals along the Colorado River (Halff
Associates 2003). In addition, the bottomlands improve habitat along the Colorado River by improving water quality, buffer against pollutants, lower water temperatures by shading, and provide organic nutrients to the water (Halff Associates 2003). Lastly, bottomlands not only
2

serve as buffer zones for water quality but also help protect farm and ranchlands from erosion and in areas where the buffer zone has been removed along the Colorado River, there is substantially more head cutting and eroding taking place than in areas that have bottomland buffer zones (Halff Associates 2003). For these reasons, it seems clear that we need to know more about the Colorado River bottomlands so that it can continue to provide ecological services and natural beauty to the region.
In addition to its high value as an ecosystem, a number of rare plants and communities
(Diggs et al. 1999; Poole et al. 2007) may occur on or near the river. Rare communities along the river include the Arizona walnut ( Juglans nigra )/American sycamore ( Platanus occidentalis ) and maiden hair fern ( Adiantum capillus-veneris ) grottos. Potential rare plants include Basin bell flower ( Campanula reverchonii ) known from granite and sand/gravel bars in San Saba County,
Hill Country wild mercury ( Ditaxis aphoroides ) on sandy or rocky limestone soils and known historically from Mills County, Texabama croton ( Croton alabamensis var. texensis ) endemic to
North Central Texas on limestone canyon slopes and forest understory, sycamore-leaf snowbell
( Styrax platanifolius ) on stream edges in limestone areas, scarlet clematis ( Clematis texensis ) on rocky stream banks, as well as the possibility of Comanche Peak prairie clover ( Dalea reverchonii ) in Walnut limestone glades. The following work attempts to inform people about some of the dominant plants that occur in this relatively unknown region of Texas.
Works Cited:
Diggs, G. M., Jr., B. L. Lipscomb, and R. J. O’Kennon. 1999. Shinners and Mahler’s
Illustrated Flora of North Central Texas. Botanical Research Institute of Texas, Fort
Worth, Texas.
Halff Associates, Inc. 2003. Lower Colorado River Basin Study: Phase I-Information Paper.
Report prepared for United States Corps of Engineers and Lower Colorado River
Authority.
Hayward, O.T., P. N. Dolliver, D. L. Amsbury, and J. C. Yelderman. 1992. A field guide to the
Grand Prairie of Texas, land, history, culture. Program for Regional Studies, Baylor
University, Waco, Texas.
Hill, R.T. 1901. Geography and geology of the Black and Grand Prairies, Texas. U. S.
Geological Survey. Annual Report 21.United States Geological Survey, Washington, D.C.
Poole, J. M., W. R. Carr, D. M. Price, & J. R. Singhurst. 2007. Rare plants of Texas. College
Station, Texas: Texas A&M University Press. 640 pp.
Wimmer, S. M. 2003. Vegetation response to summer burning in the Hill Country of Texas.
Unpublished Masters thesis. Texas Tech University, Lubbock, Texas.
3