Provisional. A provisional ecological site description has undergone quality control and quality assurance review. It contains a working state and transition model and enough information to identify the ecological site.
Areas shown in blue indicate the maximum mapped extent of this ecological site. Other ecological sites likely occur within the highlighted areas. It is also possible for this ecological site to occur outside of highlighted areas if detailed soil survey has not been completed or recently updated.
MLRA notes
Major Land Resource Area (MLRA): 087A–Texas Claypan Area, Southern Part
This area is entirely in south-central Texas. It makes up about 10,535 square miles (27,295 square kilometers). The towns of Bastrop, Bryan, Centerville, College Station, Ennis, Fairfield, Franklin, Giddings, Gonzales, Groesbeck, La Grange, Madisonville, and Rockdale are in this MLRA. Interstate 45 crosses the northern part of the area, and Interstate 10 crosses the southern part. A number of State Parks are located throughout this area. The parks are commonly associated with reservoirs.
Classification relationships
USDA-Natural Resources Conservation Service, 2006.
-Major Land Resource Area (MLRA) 87A
Ecological site concept
The sites are characterized by a sandy surface layer that extends 20 to 40 inches to a loamy subsurface layer. The sites are more productive and less droughty than soils with deeper sands, but not as productive as soils with a higher clay content.
These soils are on gently sloping to strongly sloping ridges and stream terraces. Slopes range from 0 to 12 percent, but are typically between 1 and 8 percent. Some soils have a perched water table up to 30 inches. The water table is highest in later winter and early spring, or during extremely wet precipitation periods.
Table 2. Representative physiographic features
Landforms
(1) Plains > Ridge (2) Plains > Stream terrace
Runoff class
Very low to high
Flooding frequency
None
Ponding frequency
None
Elevation
200–750 ft
Slope
1–8%
Water table depth
30–80 in
Aspect
Aspect is not a significant factor
Table 3. Representative physiographic features (actual ranges)
Runoff class
Not specified
Flooding frequency
Not specified
Ponding frequency
Not specified
Elevation
Not specified
Slope
12%
Water table depth
Not specified
Climatic features
The climate for MLRA 87A is humid subtropical and is characterized by hot summers, especially in July and August, and relatively mild winters. The summer months have little variation in day-to-day weather except for occasional thunderstorms that dissipate the afternoon heat. The moderate temperatures in spring and fall are characterized by long periods of mild days and cool nights. The average annual precipitation in this area is 41 inches. Most of the rainfall occurs in spring and fall. The freeze-free period averages about 276 days and the frost-free period 241 days.
Table 4. Representative climatic features
Frost-free period (average)
241 days
Freeze-free period (average)
276 days
Precipitation total (average)
41 in
Bar
Line
Figure 2. Monthly precipitation range
Bar
Line
Figure 3. Monthly average minimum and maximum temperature
Figure 4. Annual precipitation pattern
Figure 5. Annual average temperature pattern
Climate stations used
(1) CROCKETT [USC00412114], Crockett, TX
(2) FAIRFIELD 3W [USC00413047], Fairfield, TX
(3) SOMERVILLE DAM [USC00418446], Somerville, TX
(4) BARDWELL DAM [USC00410518], Ennis, TX
(5) FRANKLIN [USC00413321], Franklin, TX
(6) MADISONVILLE [USC00415477], Madisonville, TX
(7) BELLVILLE 6NNE [USC00410655], Bellville, TX
(8) GONZALES 1N [USC00413622], Gonzales, TX
(9) LA GRANGE [USC00414903], La Grange, TX
(10) ELGIN [USC00412820], Elgin, TX
(11) SMITHVILLE [USC00418415], Smithville, TX
(12) COLLEGE STN [USW00003904], College Station, TX
Influencing water features
A high water table may exist after periods of heavy rainfall.
Wetland description
A stream or wetland does not influence the plant community of this site.
Soil features
The soils are deep to very deep, fine sands and loamy fine sands with a surface 20 to 40 inches thick over loamy subsoils. Water soaks rapidly into the open soils. Even light showers penetrate below the evaporation zone and are more effective on this site than sites with deeper sands. Water retention is relatively low but the soils give up a high percent of their moisture to growing plants. Although air, water, and plant roots move through the soil with ease, frequent rains are needed to produce optimum plant growth. Inherent low fertility causes these soils to produce forage of lower quantity than associated sites with higher clay content. The site is subject to erosion where adequate herbaceous cover is not maintained and on heavy use areas such as roads and livestock trails. Soils correlated to this site include: Dubina, Dutek, Heaton, Newulm, Nimrod, Rader, Rehburg, Robco, Silstid, Straber, Styx, Tanglewood, and Tremona.
Table 5. Representative soil features
Parent material
(1) Alluvium–sandstone and shale
Surface texture
(1) Loamy fine sand
(2) Fine sand
Family particle size
(1) Loamy
Drainage class
Moderately well drained to well drained
Permeability class
Moderate to slow
Soil depth
45–80 in
Surface fragment cover <=3"
1%
Surface fragment cover >3"
Not specified
Available water capacity (0-40in)
2–5 in
Calcium carbonate equivalent (0-40in)
Not specified
Electrical conductivity (0-40in)
2 mmhos/cm
Sodium adsorption ratio (0-40in)
4
Soil reaction (1:1 water) (0-40in)
4–7.8
Subsurface fragment volume <=3" (Depth not specified)
6%
Subsurface fragment volume >3" (Depth not specified)
1%
Ecological dynamics
The Sandy site evolved and was maintained by the grazing and herding effects of native wild large ungulates, periodic fires, and extreme climatic fluctuations. Conversion of this site to cropland and the subsequent abandonment of cropping removed the natural native vegetation, organic matter, and fertility and allowed woody species to dominate the site. Continuous grazing by confined domestic livestock and the suppression of fire on non-cropland sites removes little bluestem (Schizachyrium scoparium), Indiangrass (Sorghastrum nutans), switchgrass (Panicum virgatum), and preferred forbs such as tephrosia (Tephrosia spp.) and prairie clover (Dalea spp.).
Less productive perennial and annual grasses and forbs will replace these plants. Years of continuous grazing generally lead to periods of prolonged rest for recovery of the perennial herbaceous plant component. These prolonged rest periods with no fire or brush management lead toward a community dominated by woody species such as winged elm (Ulmus alata), yaupon (Ilex vomitoria), post oak (Quercus stellata), and eastern red cedar (Juniperus virginiana).
State and transition model
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One community exists in the Savannah State, the 1.1 Tallgrass/Oak Savannah Community. The State is dominated by warm season perennial grasses and the overstory canopy cover is less than 25 percent.
Community 1.1 Tallgrass/Oak Savannah
Figure 6. Tallgrass/Oak Savannah Community
The characteristic plant community of this site is the reference plant community. This site is an open savannah of post oak and blackjack oak (Quercus marilandica) trees that shade 20 to 25 percent of the ground. The herbaceous component is mid and tallgrasses and is dominated by little bluestem which usually makes up 50 to 75 percent of the total annual production. Indiangrass, purpletop tridens (Tridens flavus), switchgrass, beaked panicum (Panicum anceps), sand lovegrass (Eragrostis trichodes), brownseed paspalum (Paspalum plicatulum), and thin paspalum (Paspalum setaceum) also occur. Cool season forage plants are scarce on this site. A variety of shrubs, vines, and forbs occur in this community.
Grazing prescriptions that permit acceptable grazing periods and allow adequate rest periods along with prescribed fire every five to seven years are important in the maintenance of the reference herbaceous plant community and the savannah landscape structure. Continuous overgrazing or over rest and the absence of fire tend to allow a vegetative shift towards woody species. Without corrective measures, this shift will continue to the Shrubland State.
Figure 7. Annual production by plant type (representative values) or group (midpoint values)
Table 6. Annual production by plant type
Plant type
Low (lb/acre)
Representative value (lb/acre)
High (lb/acre)
Grass/Grasslike
2400
2800
3200
Tree
300
350
400
Forb
150
175
200
Shrub/Vine
150
175
200
Total
3000
3500
4000
State 2 Shrubland
One community exists in the Shrubland State, the 2.1 Oak Scrub/Shrubland Community. The herbaceous production is not as great compared to the Savannah State, and overstory canopy has increased between 25 and 50 percent.
Community 2.1 Oak Scrub/Shrubland
Figure 8. Oak Scrub/Shrubland Community
This plant community is a transitional community between the Savannah and Woodland States. It develops in the absence of fire or mechanical or chemical brush management treatments. It is usually the result of abandonment following either cropping or yearly continuous grazing. Trees and shrubs begin to encroach onto pastureland or replace the grassland component of the Tallgrass/Oak Savannah Community. In addition to the naturally occurring oaks, other woody species such as eastern persimmon, winged elm, and eastern red cedar increase in density and canopy coverage (25 to 50 percent). Remnants of little bluestem and Indiangrass may still occur but the herbaceous component of the community becomes dominated by lesser producing grasses and forbs. Initially, species such as brownseed paspalum (Paspalum plicatulum), tall dropseed (Sporobolus compositus), and fall witchgrass (Digitaria cognata) replace the taller grasses. As the site continues to transition, the plants which increase or invade on the site include sandbur (Cenchrus spp.), red lovegrass (Eragrostis secundiflora), Yankeeweed (Eupatorium compositifolium), bullnettle (Cnidoscolus texanus), croton (Croton spp.), snake cotton (Froelichia spp.), prickly pear (Opuntia spp.), queen's delight (Stillingia texana), beebalm (Monarda spp.), and baccharis (Baccharis spp.).
Prescribed burning on a three to five year interval in conjunction with prescribed grazing may be a viable option for returning this site to the Savannah State providing woody canopy cover is less than 50 percent and adequate herbaceous fine fuel still exists. When this threshold is exceeded, mechanical or chemical brush control becomes necessary to move this transitional community back towards the Savannah State.
Figure 9. Annual production by plant type (representative values) or group (midpoint values)
Table 7. Annual production by plant type
Plant type
Low (lb/acre)
Representative value (lb/acre)
High (lb/acre)
Grass/Grasslike
1350
1575
1800
Tree
900
1050
1200
Shrub/Vine
600
700
800
Forb
150
175
200
Total
3000
3500
4000
State 3 Woodland
One community exists in the Woodland State, the Post Oak/Elm Woodland Community. The site is characterized by little herbaceous production. The overstory canopy is over 50 percent and shrubs also limit light to the surface.
Community 3.1 Post Oak/Elm Woodland
Figure 10. Post Oak/Elm Woodland Community
This plant community is a closed overstory (50 to 80 percent) woodland dominated by post oak, winged elm, blackjack oak, black hickory (Carya texana), and eastern red cedar. Understory shrubs and sub-shrubs include yaupon, farkleberry, possumhaw (Ilex decidua), and American beautyberry (Callicarpa americana). Woody vines also occur and include poison ivy (Toxicodendron radicans), grape (Vitis spp.), greenbriar (Smilax spp.), Virginia creeper (Parthenocissus quinquefolia), and peppervine (Ampelopsis arborea). A herbaceous understory is almost nonexistent, but shade-tolerant species including longleaf woodoats (Chasmanthium sessiliflorum), cedar sedge (Carex planostachys), ironweed (Veronia baldwinii), and goldenrod (Solidago spp.) may occur in small amounts.
Prescribed burning in conjunction with prescribed grazing may be used to convert this site back to a Savannah State but generally it takes many consecutive years of burning due to light fine fuel loads comprised mainly of hardwood tree leaves. Weather conditions are rarely condusive to burning this fuel type in this region. Chemical brush control on a large scale is not a viable treatment option on this site due to the resistance of yaupon to broadcast herbicide applications. However, individual plant treatment with herbicides on small acreage is a viable option. Mechanical treatment of this site, along with seeding, is the most viable option for reversion back to the reference community. Although, the economic viability of this option is questionable.
Figure 11. Annual production by plant type (representative values) or group (midpoint values)
Table 8. Annual production by plant type
Plant type
Low (lb/acre)
Representative value (lb/acre)
High (lb/acre)
Tree
1350
1575
1800
Shrub/Vine
1050
1225
1400
Grass/Grasslike
450
525
600
Forb
150
175
200
Total
3000
3500
4000
State 4 Converted
The Converted Land State contains one community, the 4.1 Converted Land Community. The state is characterized by the land manager farming crops or planted grasses.
Community 4.1 Converted Land
Figure 12. Converted Land Community
Conversion of this site to cropland occurred from the middle 1800's to the early 1900's. Some remains in cropland today, typically cotton (Gossypium spp.), corn (Zea mays), sorghum (Sorghum spp.), and soybeans (Glycine max). Specifically, this site is used for watermelons, peas, sweet potatoes, and peanuts. Ditching, land leveling, and levee construction has significantly changed the topography and hydrology on many acres of this site. While restoration of this site to a semblance of the reference plant community is possible with seeding and prescribed grazing, complete restoration of the reference community in a reasonable time is very unlikely.
Following crop production, this site is often planted to native or introduced grasses and legumes for livestock grazing or hay production. Typical species planted include improved Bermudagrass varieties, bahiagrass, switchgrass, dallisgrass, eastern gamagrass, annual ryegrass (Lolium multiflorum), and white clover. Many of the introduced species (bahiagrass, Bermudagrass, and dallisgrass) are invasive-moving by wind, water, and animals. Once established, they are extremely difficult to remove and will hinder the reestablishment of native species. The establishment and maintenance of these species requires cultivation, fertilization, weed control, and prescribed grazing management.
Transition T1A State 1 to 2
The Savannah State will transition to the Shrubland State when continued heavy grazing pressure, no brush management, and/or field abandonment continues. The transition is evident when woody species canopy cover exceeds 25 percent and grasses shift composition to more shade-tolerant species.
Transition T1B State 1 to 4
The transition to the Converted State occurs when the site is plowed for planting crops or pasture. The driver for the transition is the land manager's decision to farm the site.
Restoration pathway R2A State 2 to 1
Restoration back to the Savannah State requires brush management, prescribed grazing and/or prescribed fire. Mechanical or chemical controls can be used to remove the woody overstory species and shrubs. Prescribed grazing may require destocking and/or deferment.
Transition T2A State 2 to 3
The Shrubland State will transition to the Woodland State when continued heavy grazing pressure, no brush management, and/or field abandonment continues. The transition is evident when woody species canopy cover exceeds 50 percent and grasses shift composition to more shade-tolerant species.
Transition T2B State 2 to 4
The transition to the Converted State occurs when the site is plowed for planting crops or pasture. The driver for the transition is the land manager's decision to farm the site.
Restoration pathway R3A State 3 to 1
Restoration back to the Savannah State requires substantial energy inputs. Brush management and prescribed grazing will be needed to shift the community back to the reference state. Mechanical or chemical controls can be used to remove the woody overstory species back below 25 percent. Prescribed grazing may require destocking and/or deferment to manage the understory grasses back to those found in the reference community. Fire may be an option, but only if adequate amounts of fine fuel exist in the understory.
Transition T3A State 3 to 4
The transition to the Converted State occurs when the site is plowed for planting crops or pasture. The driver for the transition is the land manager's decision to farm the site.
Restoration pathway R4A State 4 to 1
The restoration to State 1 can occur when the land manager ceases agronomic practices. Range planting of native species found in the reference community will be required to bring back a similar community as the State 1 plant composition. The extent of previous soil disturbances will determine how much seedbed preparation will be needed, as well as the ability to be restored. Proper grazing and brush management will be required to ensure success.
Transition T4A State 4 to 3
The Converted Land State will transition to the Woodland State when continued heavy grazing pressure, no brush management, and/or field abandonment continues. The transition is evident when woody species canopy cover exceeds 50 percent and grasses shift composition to more shade-tolerant species.
Additional community tables
Table 9. Community 1.1 plant community composition
The historic savannah provided habitat to bison, deer, turkey, migratory birds and large predators such as wolves, coyotes, mountain lions, and black bear. White-tailed deer, turkey, coyotes, bobcats, and migratory birds find suitable habitat in these savannahs today. Domestic livestock and exotic ungulates are the dominant grazers and browsers on this site. As the savannah transitions through the various vegetative states towards the woodlands, the quality of the habitat may improve for some species and decline for others. Management must be applied to maintain a vegetative state in optimum habitat quality for the desired animal species.
Hydrological functions
Peak rainfall periods occur in May and June from frontal passage thunderstorms and in September and October from tropical systems as well as frontal passages. Rainfall amounts may be high (three to five inches per event) and events may be intense. Extended periods (60 days) of little to no rainfall during the growing season are common. Because of the gently sloping to sloping topography with a rapid intake rate of the surface sands and very rapid permeability of the soils, there is usually little to no runoff on this site. Water from these somewhat excessively drained soils provides groundwater recharge.
Recreational uses
Hunting, camping, bird watching, and equestrian are all common activities.
Wood products
Oaks are used for firewood. Hickory and mesquite are used for barbecue wood. Yaupon is used for landscaping.
Other products
Fruit from dewberries, grapes, and plums are harvested.
Supporting information
Inventory data references
These site descriptions were developed as part a Provisional Ecological Site project using historic soil survey manuscripts, available site descriptions, and low intensity field traverse sampling. Future work to validate the information is needed. This will include field activities to collect low, medium, and high-intensity sampling, soil correlations, and analysis of that data. A final field review, peer review, quality control, and quality assurance review of the will be needed to produce the final document.
Other references
1. Archer, S. 1994. Woody plant encroachment into southwestern grasslands and savannas: rates, patterns and proximate causes. In: Ecological implications of livestock herbivory in the West, pp. 13-68. Edited by M. Vavra, W. Laycock, R. Pieper. Society for Range Management Publication, Denver, CO.
2. Archer, S. and F.E. Smeins. 1991. Ecosystem-level Processes. Chapter 5 in: Grazing Management: An Ecological Perspective. Edited by R.K. Heitschmidt and J.W. Stuth. Timber Press, Portland, OR.
3. Bestelmeyer, B.T., J.R. Brown, K.M. Havstad, R. Alexander, G. Chavez, and J.E. Herrick. 2003. Development and use of state-and-transition models for rangelands. J. Range Manage. 56(2): 114-126.
4. Brown, J.R. and S. Archer. 1999. Shrub invasion of grassland: recruitment is continuous and not regulated by herbaceous biomass or density. Ecology 80(7): 2385-2396.
5. Foster, J.H. 1917. Pre-settlement fire frequency regions of the United States: a first approximation. Tall Timbers Fire Ecology Conference Proceedings No. 20.
6. Gould, F.W. 1975. The Grasses of Texas. Texas A&M University Press, College Station, TX. 653p.
7. Hamilton, W. and D. Ueckert. 2005. Rangeland Woody Plant Control: Past, Present, and Future. Chapter 1 in: Brush Management: Past, Present, and Future. pp. 3-16. Texas A&M University Press.
8. Scifres, C.J. and W.T. Hamilton. 1993. Prescribed Burning for Brush Management: The South Texas Example. Texas A&M University Press, College Station, TX. 245 p.
9. Smeins, F., S. Fuhlendorf, and C. Taylor, Jr. 1997. Environmental and Land Use Changes: A Long Term Perspective. Chapter 1 in: Juniper Symposium 1997, pp. 1-21. Texas Agricultural Experiment Station.
10. Stringham, T.K., W.C. Krueger, and P.L. Shaver. 2001. State and transition modeling: and ecological process approach. J. Range Manage. 56(2):106-113.
11. Texas Agriculture Experiment Station. 2007. Benny Simpson’s Texas Native Trees (http://aggie-horticulture.tamu.edu/ornamentals/natives/).
12. Texas A&M Research and Extension Center. 2000. Native Plants of South Texas (http://uvalde.tamu.edu/herbarium/index.html).
13. Thurow, T.L. 1991. Hydrology and Erosion. Chapter 6 in: Grazing Management: An Ecological Perspective. Edited by R.K. Heitschmidt and J.W. Stuth. Timber Press, Portland, OR.
14. USDA/NRCS Soil Survey Manuals counties within MLRA 87A.
15. USDA, NRCS. 1997. National Range and Pasture Handbook.
16. USDA, NRCS. 2007. The PLANTS Database (http://plants.usda.gov). National Plant Data Center, Baton Rouge, LA 70874-4490 USA.
17. Vines, R.A. 1984. Trees of Central Texas. University of Texas Press, Austin, TX.
18. Vines, R.A. 1977. Trees of Eastern Texas. University of Texas Press, Austin, TX. 538 p.
19. Wright, H.A. and A.W. Bailey. 1982. Fire Ecology: United States and Southern Canada. John Wiley & Sons, Inc.
Contributors
Mike Stellbaur Tyson Hart
Approval
Bryan Christensen, 9/21/2023
Rangeland health reference sheet
Interpreting Indicators of Rangeland Health is a qualitative assessment protocol used to
determine ecosystem condition based on benchmark characteristics described in the Reference Sheet. A suite of 17 (or
more) indicators are typically considered in an assessment. The ecological site(s) representative of an assessment
location must be known prior to applying the protocol and must be verified based on soils and climate. Current plant
community cannot be used to identify the ecological site.
Author(s)/participant(s)
Mike Stellbauer, David Polk, and Bill Deauman
Contact for lead author
Mike Stellbauer, Zone RMS, NRCS, Bryan, Texas
Date
06/08/2004
Approved by
Bryan Christensen
Approval date
Composition (Indicators 10 and 12) based on
Annual Production
Indicators
Number and extent of rills:
None.
Presence of water flow patterns:
Water flow patterns are uncommon on this site.
Number and height of erosional pedestals or terracettes:
Pedestals or terracettes are uncommon for this site when occupied by the reference community.
Bare ground from Ecological Site Description or other studies (rock, litter, lichen, moss, plant canopy are
not bare ground):
Expect no more than 25 percent bare ground randomly distributed in small patches.
Number of gullies and erosion associated with gullies:
No gullies should be present.
Extent of wind scoured, blowouts and/or depositional areas:
None.
Amount of litter movement (describe size and distance expected to travel):
This site has highly permeable soils with high infiltration rates. Only small-sized litter will move short distances with intense storms.
Soil surface (top few mm) resistance to erosion (stability values are averages - most sites will show a range
of values):
Soil surface is resistant to erosion. Soil Stability class range is expected to be 3 to 5.
Soil surface structure and SOM content (include type of structure and A-horizon color and thickness):
Soil surface structure is 0 to 40 inches thick with colors from pale brown fine sand to dark brown loamy fine sand and generally weak fine granular structure. SOM is less than one percent.
Effect of community phase composition (relative proportion of different functional groups) and spatial
distribution on infiltration and runoff:
The savannah of trees, shrubs, vines, grasses and forbs, along with adequate litter and little bare ground, provides for maximum infiltration and little runoff under normal rainfall events.
Presence and thickness of compaction layer (usually none; describe soil profile features which may be
mistaken for compaction on this site):
None.
Functional/Structural Groups (list in order of descending dominance by above-ground annual-production or live foliar
cover using symbols: >>, >, = to indicate much greater than, greater than, and equal to):
Dominant:
Warm-season tallgrasses >>
Sub-dominant:
Warm-season midgrasses >
Other:
Trees > Shrubs/Vines > Forbs
Additional:
Amount of plant mortality and decadence (include which functional groups are expected to show mortality or
decadence):
There should be little mortality or decadence for any functional groups.
Average percent litter cover (%) and depth ( in):
Litter is primarily herbaceous.
Expected annual annual-production (this is TOTAL above-ground annual-production, not just forage annual-production):
3,000 pounds per acre for below average moisture years to 4,000 pounds per acre for above average moisture years.
Potential invasive (including noxious) species (native and non-native). List species which BOTH characterize
degraded states and have the potential to become a dominant or co-dominant species on the ecological site if
their future establishment and growth is not actively controlled by management interventions. Species that become
dominant for only one to several years (e.g., short-term response to drought or wildfire) are not invasive
plants. Note that unlike other indicators, we are describing what is NOT expected in the reference state for the
ecological site:
Potential invasive species include bahiagrass, common Bermudagrass, post oak, yaupon, eastern persimmon, and winged elm.
Perennial plant reproductive capability:
All perennial plants should be capable of reproducing except during periods of prolonged drought conditions, heavy natural herbivory or intense wildfires.
The Ecosystem Dynamics Interpretive Tool is an information system framework developed by the USDA-ARS Jornada Experimental Range, USDA Natural Resources Conservation Service, and New Mexico State University.
Click on box and path labels to scroll to the respective text.
