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Ecological site R083BY018TX

Clay Flat

Last updated: 9/19/2023
Accessed: 11/21/2024

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General information

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.

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Figure 1. Mapped extent

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): 083B–Western Rio Grande Plain

Major Land Resource Area (MLRA) 83B It makes up about 9,285 square miles (24,060 square kilometers). The border towns of Del Rio, Eagle Pass, Laredo, and Zapata are in this MLRA. Interstate 35 crosses the area just north of Laredo. The Amistad National Recreation Area is just outside this MLRA, northwest of Del Rio, and the Falcon State Recreation Area is southeast of Laredo. Laughlin Air Force Base is just east of Del Rio. This area is comprised of inland, dissected coastal plains.

Classification relationships

USDA-Natural Resources Conservation Service, 2006.
-Major Land Resource Area (MLRA) 83B

Ecological site concept

The Clay Flat is characterized by heavy clay soils on nearly level slopes. Sites are productive, but can be droughty due to their high clay content and available moisture to plants.

Associated sites

R083BY003TX	Gravelly Ridge
R083BY015TX	Saline Clay
R083BY016TX	Saline Clay Loam
R083BY010TX	Vega
R083BY019TX	Gray Sandy Loam

Table 1. Dominant plant species

Tree	(1) Prosopis glandulosa
Shrub	(1) Celtis ehrenbergiana (2) Ziziphus obtusifolia
Herbaceous	(1) Sporobolus airoides (2) Tridens albescens

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Physiographic features

These nearly level soils are on smooth uplands and occasionally flooded drainageways on the inland, dissected Coastal Plains. Slopes range from 0 to about 1. Elevation is 200 to 600 feet.

Table 2. Representative physiographic features

Landforms	(1) Coastal plain > Drainageway (2) Coastal plain > Flat
Runoff class	High
Flooding duration	Brief (2 to 7 days)
Flooding frequency	None to occasional
Ponding frequency	None
Elevation	61 – 183 m
Slope	0 – 1%
Aspect	Aspect is not a significant factor

Climatic features

MLRA 83B mainly has a subtropical steppe climate along the Rio Grande River and subtropical subhumid climates in La Salle and McMullen counties. Winters are dry and mild and the summers are hot. Tropical maritime air masses predominate throughout spring, summer and fall. Modified polar air masses exert considerable influence during winter, creating a continental climate characterized by large variations in temperature. Peak rainfall occurs late in spring and a secondary peak occurs early in fall. Most heavy thunderstorm activities occur during the summer months. July is hot and dry with little weather variations. Rainfall increases again in late August and September as tropical disturbances increase and become more frequent as the storms dissipate. Tropical air masses from the Gulf of Mexico dominate during the spring, summer and fall. Prevailing winds are southerly to southeasterly throughout the year except in December when winds are predominately northerly.

Table 3. Representative climatic features

Frost-free period (characteristic range)	231-321 days
Freeze-free period (characteristic range)	313-365 days
Precipitation total (characteristic range)	508 mm
Frost-free period (actual range)	214-365 days
Freeze-free period (actual range)	260-365 days
Precipitation total (actual range)	483-533 mm
Frost-free period (average)	270 days
Freeze-free period (average)	340 days
Precipitation total (average)	508 mm

Characteristic range

Actual range

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Figure 2. Monthly precipitation range

Characteristic range

Actual range

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Figure 3. Monthly minimum temperature range

Characteristic range

Actual range

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Figure 4. Monthly maximum temperature range

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Figure 5. Monthly average minimum and maximum temperature

Figure 6. Annual precipitation pattern

Figure 7. Annual average temperature pattern

Climate stations used

(1) EAGLE PASS 3N [USC00412679], Eagle Pass, TX
(2) CRYSTAL CITY [USC00412160], Crystal City, TX
(3) FALCON DAM [USC00413060], Roma, TX
(4) LAREDO 2 [USC00415060], Laredo, TX
(5) ZAPATA 1 S [USC00419976], Zapata, TX
(6) DEL RIO INTL AP [USW00022010], Del Rio, TX
(7) CATARINA [USC00411528], Asherton, TX
(8) DEL RIO 2 NW [USC00412361], Del Rio, TX

Soil features

The soils are very deep, moderately well drained with very slow permeability. They were formed in alkaline clayey alluvium. Surface color is dark gray or gray. The profile is effervescent throughout. Gilgai relief, in undisturbed areas, has microhighs 5 to 12 feet in diameter and 3 to 12 inches higher than the microlows. The soil series correlated to this site is the Monwebb series.

Table 4. Representative soil features

Parent material	(1) Alluvium – sedimentary rock
Surface texture	(1) Clay
Family particle size	(1) Fine
Drainage class	Moderately well drained
Permeability class	Very slow
Soil depth	203 cm
Surface fragment cover <=3"	0%
Surface fragment cover >3"	0%
Available water capacity (0-101.6cm)	10.16 cm
Calcium carbonate equivalent (0-101.6cm)	2 – 40%
Electrical conductivity (0-101.6cm)	0 – 20 mmhos/cm
Sodium adsorption ratio (0-101.6cm)	0 – 40
Soil reaction (1:1 water) (0-101.6cm)	7.4 – 8.4
Subsurface fragment volume <=3" (Depth not specified)	0 – 3%
Subsurface fragment volume >3" (Depth not specified)	0%

Ecological dynamics

The Clay Flats are a productive plant community, but this is a droughty site due to heavy clay soils with high shrink/swell properties. If this site is denuded by excessive grazing, extended long-term drought, or some other catastrophic event and perennial grasses are lost, the site will be slow to recover. The plant communities found on this site are dominated by midgrasses with occasional shrubs throughout. The dominant midgrasses include alkali sacaton (Sporobolus airoides), vine mesquite (Panicum obtusum), false Rhodesgrass (Trichloris crinita), white tridens (Tridens albescens), silver bluestem (Bothriochloa laguroides), Arizona cottontop (Digitara californica), and plains bristlegrass (Setaria vulpiseta). Shortgrasses such as curly-mesquite (Hilaria belangeri), Hall’s panicum (Panicum halli), and buffalograss (Bouteloua dactyloides) were common to the site but made up a small percentage of the total herbaceous production. The woody plant community on this site is sparse and scattered and contain honey mesquite (Prosopis glandulosa), lotebush (Ziziphus obtusifolia), wolfberry (Lycium berlandieri), whitebrush (Aloysia gratissima) and prickly pear (Opuntia spp.). Forbs common to the site include jicamilla (Jatropha cathartica), low wild mercury (Argythamnia humilis), Texas varilla (Varilla texana), hairy tubetongue (Justicia pilosella), and prostrate bundleflower (Desmanthus glandulosus).

Historically, the plant community was maintained by periodic grazing of roaming herds of wildlife, such as bison (Bos bison), and numerous fires that were set by lightning and Native Americans. Likely, this was a shifting mosaic over time over the landscape consisting of burned/grazed and unburn/ungrazed portions. The site was very productive and maintained a high percentage of ground cover with forage production. Runoff of rainfall was slow allowing the soil profile to fill to capacity. The fertility of the site was high.

The accounts of early explorers and settlers suggest that the Rio Grande Plains was likely a vast mosaic of open grassland, savannah, and shrubland. While moving in 1691 out of Maverick County and into Zavala County, Don Domingo de Teran found after crossing the Nueces River “the country was level and covered with mesquites and cats’ claw.” In 1849, Michler described south Texas as “concerning the land both on the Frio and the Leona, from these rivers back, that it may be divided into four parallel strips-the first, next to the river, consisting of heavy timber, and a heavy black soil, the second, a mesquite flat, of small width, and the soil of a lighter nature, and very fertile; the third, a range of low hills, covered with loose stones, and thick chaparral; the fourth, a wide-open prairie.” Lehman indicates, “thus while it is quite true that the Rio Grande Plains once had fewer woody plants and more grass than now, it is also true that an ample seed stock of shrubs and trees has been widely distributed for as long as man has known.” The vegetation structure likely varied from place-to-place depending on topography, soil properties, and time since the last major disturbance.

Large numbers of domestic livestock grazed South Texas as early as the mid-1700’s. Formal deeds to properties from the Spanish and Mexican governments came in the late 1760’s with much larger blocks granted in the decades to follow. Lehman indicated, “in 1757, the official Spanish census showed residents of Camargo and Reynosa in the lower Rio Grande owning over 90,000 sheep and goats. By way of contrast, combined numbers of cattle, oxen, horses, mules and burros were less than 16,000.” By the mid-1800’s, according to Lehman’s figures from the U. S. Census of 1889, “there were a minimum of 1,644,268 sheep-fully 45 percent of Texas total population, grazing south of the Nueces River.” According to Inglis, “the Rio Grande Plains had the four-leading sheep producing counties in the state and ten of the top fifteen sheep producing counties were in South Texas. The peak decade was 1880 to 1890, at times exceeding two million head.” These domestic animals were in addition to bison, antelope, deer, and large herds of wild horses. It is obvious from early accounts, that much of the Rio Grande Plains was periodically grazed hard by both domestic animals and wild populations as early as the early to mid-1700’s. It may be that overgrazing by sheep and goats could have suppressed the many shrubs, reduced shrub canopy, and arrested shrub seedlings.

State and transition model

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Standard diagram

Figure 8. STM

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Click on state and transition labels to scroll to the respective text

Ecosystem states

1. Grassland

2. Shrubland

3. Seeded

T1A	-	Absence of disturbance and natural regeneration over time coupled with excessive grazing pressure
T1B	-	Excessive soil disturbance followed by seeding improved forage species
R2A	-	Reintroduction of historic disturbance return intervals
T2A	-	Excessive soil disturbance followed by seeding improved forage species
T3A	-	Absence of disturbance and natural regeneration over time coupled with excessive grazing pressure

State 1
Grassland

Dominant plant species

alkali sacaton (Sporobolus airoides), grass
vine mesquite (Panicum obtusum), grass

Community 1.1
Midgrass Dominant

The reference community for the site was a midgrass dominated plant community. Trees and shrubs on this site were widely scattered and made up an insignificant portion of total production. Bison grazing was intermittent, and fires were both frequent (5 to 10 years) and intense. This site was extensively grazed by wild ungulates and domestic livestock by the mid-1700’s and even more heavily grazed by livestock by the mid-1800’s. Abusive grazing with no rest was exacerbated by the introduction of barbed wire and water development. Continued overuse will result in a reduced production of biomass, reduced litter accumulation, loss or reduction of some midgrass species, and reduction of fire frequency and intensity. Common midgrasses include alkali sacaton, false Rhodesgrass, white tridens, Arizona cottontop, plains bristlegrass, and Texas bristlegrass. Shortgrass species include curly-mesquite, buffalograss, and Hall’s panicum. Woody plants included honey mesquite, lotebush, guayacan, wolfberry, whitebrush, and prickly pear.

Figure 9. Annual production by plant type (representative values) or group (midpoint values)

Table 5. Annual production by plant type

Plant type	Low (kg/hectare)	Representative value (kg/hectare)	High (kg/hectare)
Grass/Grasslike	1121	2802	4147
Tree	168	224	252
Shrub/Vine	112	168	196
Forb	28	56	112
Total	1429	3250	4707

Figure 10. Plant community growth curve (percent production by month). TX4800, Midgrass Dominant Community. Warm-season midgrasses with forbs and shrubs..

Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
J	F	M	A	M	J	J	A	S	O	N	D
1	1	2	10	20	20	5	8	15	10	6	2

Community 1.2
Mid/Shortgrass Dominant

Figure 11. 1.2 Mid/Shortgrass Dominant Community

This plant community develops as abusive grazing continues. Midgrasses such as alkali sacaton, false Rhodesgrass, vine mesquite, and plains bristlegrass decrease in the plant community. Less palatable midgrasses such as white tridens and pappusgrass increase along with increased amounts of curly-mesquite and other shortgrasses. Fire frequency and intensity will decrease allowing woody plants and prickly pear to begin encroaching on the landscape. Woody canopy includes mesquite, lotebush, and guayacan.

Figure 12. Annual production by plant type (representative values) or group (midpoint values)

Table 6. Annual production by plant type

Plant type	Low (kg/hectare)	Representative value (kg/hectare)	High (kg/hectare)
Grass/Grasslike	897	2466	3587
Tree	224	280	308
Shrub/Vine	168	224	252
Forb	28	56	112
Total	1317	3026	4259

Figure 13. Plant community growth curve (percent production by month). TX4805, Mid/Shortgrass Dominant Community. Mid and shortgrasses with increasing trees and shrubs..

Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
J	F	M	A	M	J	J	A	S	O	N	D
1	1	5	15	20	20	5	5	15	8	4	1

Pathway 1.1A
Community 1.1 to 1.2

The reference community (1.1) will transition to the Mid/Shortgrass Dominant Community (1.2) with lack of fire, continued overgrazing, insufficient rest cycles, and/or natural disturbances, like prolonged drought.

Pathway 1.2A
Community 1.2 to 1.1

This phase can be managed back to the Midgrass Dominant Community (1.1) but will take the reintroduction of fire to the ecosystem or some method of brush management that allows selective removal of the plants. A prescribed grazing plan will be essential to reverse the trend and return the midgrasses back to the plant community over an extended period time.

State 2
Shrubland

Dominant plant species

honey mesquite (Prosopis glandulosa), shrub
lotebush (Ziziphus obtusifolia), shrub

Community 2.1
Mid/Shortgrass Shrubland Complex

This community develops because of continued heavy grazing which reduces biomass production and litter accumulation thus reducing fire frequency and intensity. Other subtle impacts occur on the site as water, mineral, and energy cycles are altered. Midgrasses are significantly reduced and alkali sacaton, false Rhodesgrass, vine mesquite, Arizona cottontop and other more palatable mid grasses may be absent. Other midgrasses such as pappusgrass, white tridens, hooded windmillgrass, and purple three-awn are the most common midgrasses. Shortgrasses such as curly-mesquite, whorled dropseed, and Hall’s panicum are much more common than in the reference community and account for a higher percentage of herbaceous production. Due to reduced grass canopy, decreased fire frequency, and more exposed soil surface, woody species have increased significantly on the site. The woody plant community will be dominated by honey mesquite and prickly pear, but other woody species such as lotebush, guayacan, whitebrush will be present.

Figure 14. Annual production by plant type (representative values) or group (midpoint values)

Table 7. Annual production by plant type

Plant type	Low (kg/hectare)	Representative value (kg/hectare)	High (kg/hectare)
Grass/Grasslike	673	2018	2914
Tree	448	504	560
Shrub/Vine	224	280	336
Forb	56	84	112
Total	1401	2886	3922

Figure 15. Plant community growth curve (percent production by month). TX4801, Mid/Shortgrasses Shrubland Community. Mid and shortgrasses with forbs and 20-50% woody canopy..

Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
J	F	M	A	M	J	J	A	S	O	N	D
1	1	2	10	20	20	5	8	15	10	6	2

Community 2.2
Wooded Grassland

Figure 16. 2.2 Wooded Grassland Community

In community 2.1, midgrasses are limited in volume and may be relegated to growing within thorny shrubs and/or prickly pear. Interspaces between woody plants are dominated by shortgrasses such as curly-mesquite, whorled dropseed, Hall’s panicum, and purple three-awn. Fire is a rare occurrence and most likely occurs only following years of abundant rainfall. Honey mesquite and prickly pear are greatly increased along with woody shrubs such as whitebrush, lotebush and guayacan. This state may also be heavily invaded by goldenweed and perennial broomweed, which greatly reduces grass production. These weedy species along with mesquite can be managed with appropriate herbicides allowing grasses to increase and flourish. Herbicidal uses should be followed by prescribed grazing and prescribed burning as needed.

Figure 17. Annual production by plant type (representative values) or group (midpoint values)

Table 8. Annual production by plant type

Plant type	Low (kg/hectare)	Representative value (kg/hectare)	High (kg/hectare)
Grass/Grasslike	392	1121	1681
Tree	673	729	785
Shrub/Vine	252	308	336
Forb	56	112	168
Total	1373	2270	2970

Figure 18. Plant community growth curve (percent production by month). TX4802, Wooded Grassland Community. Wooded Grassland Community with 50 to 80% woody canopy cover..

Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
J	F	M	A	M	J	J	A	S	O	N	D
1	1	5	14	16	16	10	13	15	6	2	1

Pathway 2.1A
Community 2.1 to 2.2

Continued heavy grazing coupled with lack of fire will cause this community to transition to the Woodland Community (2.2). Brush density and height will continue to increase and shade the ground.

Pathway 2.2A
Community 2.2 to 2.1

To transition Community 2.2 back to 2.1, the land manager will need to apply prescribed grazing, prescribed burning (if enough fuel loads still exist), and brush management. The key is lessening the canopy cover by woody species.

State 3
Seeded

Dominant plant species

Kleberg's bluestem (Dichanthium annulatum), grass

Community 3.1
Introduced/Native Species

The Seeded State is a result of two pathways. One pathway is the result of rootplowing followed by seeding. In the past, seeds adapted to this site included Kleberg bluestem, King Ranch bluestem or Rhodesgrass. The other pathway is a result of abusive grazing followed by invasion of the site by the above-mentioned species. Seeds of the introduced bluestems are wind borne and when these species are present or carried in on vehicles or equipment, invasion is both rapid and complete. Once this site is established to these species, especially the introduced bluestems, reclamation back to a native state is nearly impossible due to the aggressive nature of these plants.

Figure 19. Annual production by plant type (representative values) or group (midpoint values)

Table 9. Annual production by plant type

Plant type	Low (kg/hectare)	Representative value (kg/hectare)	High (kg/hectare)
Grass/Grasslike	673	1793	2690
Tree	45	56	78
Shrub/Vine	22	34	45
Forb	11	22	34
Total	751	1905	2847

Figure 20. Plant community growth curve (percent production by month). TX4806, Converted Land Community - Introduced Seeding. Seeded into introduced grass species..

Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
J	F	M	A	M	J	J	A	S	O	N	D
1	1	5	15	20	20	5	5	15	8	4	1

Transition T1A
State 1 to 2

Once the woody canopy exceeds approximately 20 percent and is taller than three feet, a threshold will have been crossed to the Shrubland State (2). In this case energy in the form of heavy equipment and/or herbicides will be required along with prescribed grazing to shift the plant community back to the Grassland State (1).

Transition T1B
State 1 to 3

The Grassland Savannah State (1) can be converted to the Seeded State (3) by controlling the brush and seeding to native or introduced grasses. It may also be plowed and converted to cropland.

Restoration pathway R2A
State 2 to 1

Brush management is the key driver in restoring Shrub/Woodland State (2) back to the Grassland Savannah State (1). Reduction in woody canopy below 20 percent will take large energy inputs depending on the canopy cover. A prescribed grazing plan and prescribed burning plan will keep the state functioning.

Transition T2A
State 2 to 3

The Shrubland State (2) can be converted to the Seeded State (3) by controlling the brush and seeding to native or introduced grasses. It may also be plowed and converted to cropland.

Transition T3A
State 3 to 2

If the Seeded State (3) is left alone, eventually the woody plants will create a moderate to heavy canopy. At this point, the desired understory grasses, forbs, and/or crops will be shaded out and the site will transition into a Shrubland State (2).

Additional community tables

Table 10. Community 1.1 plant community composition

Group	Common name	Symbol	Scientific name	Annual production (kg/hectare)	Foliar cover (%)
Grass/Grasslike
1	Midgrasses			560–2074
	alkali sacaton	SPAI	Sporobolus airoides	448–1121	–
	large-spike bristlegrass	SEMA5	Setaria macrostachya	336–897	–
	vine mesquite	PAOB	Panicum obtusum	224–448	–
	false Rhodes grass	TRCR9	Trichloris crinita	112–448	–
2	Midgrasses			280–1037
	Texas bristlegrass	SETE6	Setaria texana	168–448	–
	white tridens	TRAL2	Tridens albescens	224–448	–
	silver beardgrass	BOLAT	Bothriochloa laguroides ssp. torreyana	84–168	–
	Arizona cottontop	DICA8	Digitaria californica	56–168	–
3	Short/Midgrasses			168–622
	hooded windmill grass	CHCU2	Chloris cucullata	84–168	–
	tobosagrass	PLMU3	Pleuraphis mutica	0–140	–
	plains lovegrass	ERIN	Eragrostis intermedia	0–112	–
	whiplash pappusgrass	PAVA2	Pappophorum vaginatum	22–112	–
	purple threeawn	ARPU9	Aristida purpurea	11–84	–
	sand dropseed	SPCR	Sporobolus cryptandrus	11–56	–
4	Shortgrasses			112–415
	curly-mesquite	HIBE	Hilaria belangeri	112–224	–
	Hall's panicgrass	PAHAH	Panicum hallii var. hallii	56–168	–
	Madagascar dropseed	SPPY2	Sporobolus pyramidatus	6–112	–
	buffalograss	BODA2	Bouteloua dactyloides	0–112	–
	Texas grama	BORI	Bouteloua rigidiseta	0–34	–
	red grama	BOTR2	Bouteloua trifida	0–22	–
	fall witchgrass	DICO6	Digitaria cognata	0–22	–
Forb
5	Forbs			28–112
	Drummond's goldenbush	ISDR	Isocoma drummondii	6–112	–
	broom snakeweed	GUSA2	Gutierrezia sarothrae	0–56	–
	Texas varilla	VATE2	Varilla texana	0–56	–
	Berlandier's nettlespurge	JACA3	Jatropha cathartica	6–22	–
	weakleaf bur ragweed	AMCO3	Ambrosia confertiflora	6–22	–
	Cuman ragweed	AMPS	Ambrosia psilostachya	6–22	–
	low silverbush	ARHU5	Argythamnia humilis	1–11	–
	prairie broomweed	AMDR	Amphiachyris dracunculoides	0–11	–
	Gregg's tube tongue	JUPI5	Justicia pilosella	6–11	–
	sensitive plant	MIMOS	Mimosa	2–11	–
	silverleaf nightshade	SOEL	Solanum elaeagnifolium	0–11	–
	globemallow	SPHAE	Sphaeralcea	2–11	–
	haplopappus	HAPLO11	Haplopappus	2–6	–
	upright prairie coneflower	RACO3	Ratibida columnifera	0–6	–
	fanpetals	SIDA	Sida	2–6	–
	Forb, annual	2FA	Forb, annual	1–6	–
	Forb, perennial	2FP	Forb, perennial	1–6	–
	Rio Grande stickpea	CACO	Calliandra conferta	1–6	–
	glandular bundleflower	DEGL8	Desmanthus glandulosus	2–6	–
Shrub/Vine
6	Shrubs/Vines			112–196
	pricklypear	OPUNT	Opuntia	11–56	–
	lotebush	ZIOB	Ziziphus obtusifolia	17–56	–
	spiny hackberry	CEEH	Celtis ehrenbergiana	11–45	–
	Texas lignum-vitae	GUAN	Guaiacum angustifolium	22–45	–
	crown of thorns	KOSP	Koeberlinia spinosa	6–22	–
	Berlandier's wolfberry	LYBE	Lycium berlandieri	11–22	–
	catclaw acacia	ACGRG3	Acacia greggii var. greggii	6–22	–
	catclaw acacia	ACGRW	Acacia greggii var. wrightii	6–22	–
	Schaffner's wattle	ACSCB	Acacia schaffneri var. bravoensis	6–22	–
	whitebrush	ALGR2	Aloysia gratissima	6–22	–
	Texan goatbush	CAERT	Castela erecta ssp. texana	6–22	–
	jointfir	EPHED	Ephedra	6–17	–
	leatherstem	JADI	Jatropha dioica	6–11	–
	Christmas cactus	CYLE8	Cylindropuntia leptocaulis	6–11	–
Tree
7	Trees			168–252
	honey mesquite	PRGL2	Prosopis glandulosa	168–252	–

Interpretations

Animal community

As a historic tall/midgrass prairie, this site was occupied by bison, antelope, deer, quail, turkey, and dove. This site was also used by many species of grassland songbirds, migratory waterfowl, and coyotes. This site now provides forage for livestock and is still used by quail, dove, migratory waterfowl, grassland birds, coyotes, and deer.

Feral hogs (Sus scrofa) can be found on most ecological sites in Texas. Damage caused by feral hogs each year includes, crop damage by rutting up crops, destroyed fences, livestock watering areas, and predation on native wildlife. Feral hogs have few natural predators, thus allowing their population to grow to high numbers.

Wildlife habitat is a complex of many different plant communities and ecological sites across the landscape. Most animals use the landscape differently to find food, shelter, protection, and mates. Working on a conservation plan for the whole property, with a local professional, will help managers make the decisions that allow them to realize their goals for wildlife and livestock.

Grassland State (1): This state provides the maximum amount of forage for livestock such as cattle. It is also utilized by deer, quail and other birds as a source of food. When a site is in the reference plant community phase (1.1) it will also be used by some birds for nesting, if other habitat requirements like thermal and escape cover are near.

Shrubland (2): This state can be maintained to meet the habitat requirements of cattle and wildlife. Land managers can find a balance that meets their goals and allows them flexibility to manage for livestock and wildlife. Forbs for deer and birds like quail will be more plentiful in this state. There will also be more trees and shrubs to provide thermal and escape cover for birds as well as cover for deer.

Seeded State (3): The quality of wildlife habitat this site will produce is extremely variable and is influenced greatly by the timing of rain events. This state is often manipulated to meet landowner goals. If livestock production is the main goal, it can be converted to pastureland. It can also be planted to a mix of grasses and forbs that will benefit both livestock and wildlife. A mix of forbs in the pasture could attract pollinators, birds and other types of wildlife. Food plots can also be planted to provide extra nutrition for deer.

This rating system provides general guidance as to animal preference for plant species. It also indicates possible competition between kinds of herbivores for various plants. Grazing preference changes from time to time, especially between seasons, and between animal kinds and classes. Grazing preference does not necessarily reflect the ecological status of the plant within the plant community. For wildlife, plant preferences for food and plant suitability for cover are rated. Refer to habitat guides for a more complete description of a species habitat needs.

Hydrological functions

The grassland and the grassland/shrubland communities on this site use all the water from rainfall events that occur. Research has shown that the evapotranspiration rate on the grassland and the grassland/shrubland is nearly the same. Very little water could be harvested from this site if the woody plant community is replaced by a grass-dominated community.

Recreational uses

White-tailed deer, quail, javelina, and feral hogs are hunted on the site. Bird watching is also common.

Supporting information

Inventory data references

Information presented was derived from the revised Range Site, literature, limited NRCS clipping data (417s), field observations, and personal contacts with range-trained personnel.

Other references

Archer, S. 1995. Herbivore mediation of grass-woody plant interactions. Tropical Grasslands, 29:218-235.

Archer, S. 1995. Tree-grass dynamics in a Prosopis-thornscrub savanna parkland: reconstructing the past and predicting the future. Ecoscience, 2:83-99.

De Leon, A. 2003. Itineraries of the De Léon Expeditions of 1689 and 1690. In Spanish Exploration in the Southwest, 1542-1706. Edited by H. E. Bolton. Charles Scribner’s Sons, New York, NY.

Dillehay T. 1974. Late quaternary bison population changes on the Southern Plains. Plains Anthropologist, 19:180-96.

Duaine, C. L. 1971. Caverns of Oblivion. Packrat Press, Oak Harbor, WA.

Everitt, J. H., D. L. Drawe, and R. I. Leonard. 2002. Trees, Shrubs, and Cacti of South Texas. Texas Tech University Press, Lubbock, TX.

Everitt, J. H., D. L. Drawe, and R. I. Lonard. 1999. Field Guide to the Broad-Leaved Herbaceous Plants of South Texas. Texas Tech University Press. Lubbock, TX.

Frost, C. C. 1998. Presettlement fire frequency regimes of the United States: a first approximation. In Fire in ecosystem management: shifting the paradigm from suppression to prescription. Tall Timbers Fire Ecology Conference Proceedings. 20:70-81.

Gilbert, L. E. 1982. An ecosystem perspective on the role of woody vegetation, especially mesquite, in the Tamaulipan biotic region of South Texas. Proceeding Symposium of the Tamaulipan Biotic Province, Corpus Christi, TX.

Hanselka, W., R. Lyons, and M. Moseley. 2009. Grazing Land Stewardship: A Manual for Texas Landowners. Texas AgriLife Extension Service, College Station, TX.

Hart, C. R., T. Garland, A. C. Barr, B. B. Carpenter, and J.C. Reagor. 2003. Toxic Plants of Texas: Integrated Management Strategies to Prevent Livestock Losses. Texas Cooperative Extension Bulletin B-6103 11-03.

Heitschmidt R. K., Stuth J. W., eds. 1991. Grazing management: an ecological perspective. Timberline Press, Portland, OR.

Inglis, J. M. 1964. A history of vegetation of the Rio Grande Plains. Texas Parks and Wildlife Department Bulletin No. 45, Austin, TX.

Lehman, V. W. 1969. Forgotten legions: sheep in the Rio Grande Plains of Texas. Texas Western Press, University of Texas at El Paso, El Paso, TX.

McGinty A., D. N. Ueckert. 2001. The Brush Busters success story. Rangelands, 23:3-8.

McLendon T. 1991. Preliminary description of the vegetation of South Texas exclusive of coastal saline zones. Texas Journal of Science, 43: 13-32

Norwine, J. 1978. Twentieth-century semiarid climates and climatic fluctuations in Texas and northeastern Mexico. Journal of Arid Environments, 1:313-325.

Norwine, J. and R. Bingham. 1986. Frequency and severity of droughts in South Texas: 1900-1983, 1-17. In Livestock and wildlife management during drought. Edited by R. D. Brown. Caesar Kleberg Wildlife Research Institute, Kingsville, TX.

Parvin, R. W. 2003. Rio Bravo Resource Conservation and Development. Llanos Mestenos South Texas Heritage Trail. Zapata, TX.

Scifres, C. J. and W. T. Hamilton. 1993. Prescribed burning for brushland management: the South Texas example. Texas A&M Press, College Station, TX.

Scifres C. J., W. T. Hamilton, J. R. Conner, J. M. Inglis, and G. A. Rasmussen. 1985. Integrated Brush Management Systems for South Texas: Development and Implementation. Texas Agricultural Experiment Station, College Station, TX.

Texas Parks and Wildlife Department. 2007. List of White-tailed Deer Browse and Ratings. District 8.

Thurow, T. L. and J. W. Hester. 1997. How an increase or reduction in juniper cover alters rangeland hydrology. Juniper Symposium Proceedings. Texas A&M University, San Angelo, TX.

Weltz, M. A. and W. H. Blackburn. 1995. Water budget for south Texas rangelands. Journal of Range Management, 48:45-52.

Wright, B. D., R. K. Lyons, J. C. Cathey, and S. Cooper. 2002. White-tailed deer browse preferences for South Texas and the Edwards Platea

Contributors

Gary Harris, MSSL, NRCS, Robstown, Texas

Approval

Bryan Christensen, 9/19/2023

Acknowledgments

Reviewers:
Jason Hohlt, RMS, NRCS, Kingsville, Texas
Shanna Dunn, RSS, NRCS, Corpus Christi, Texas
Justin Clary, RMS, NRCS, Temple, Texas
Vivian Garcia, RMS, NRCS, Corpus Christi, Texas

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)	Vivian Garcia, Zone RMS, NRCS, Corpus Christi, Texas
Contact for lead author	361-241-0609
Date	04/25/2008
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:
None except following extremely high intensity storms when short flow patterns may appear.
Number and height of erosional pedestals or terracettes:
None.
Bare ground from Ecological Site Description or other studies (rock, litter, lichen, moss, plant canopy are not bare ground):
0 to 3 percent bare ground with small and non-connected areas.
Number of gullies and erosion associated with gullies:
None.
Extent of wind scoured, blowouts and/or depositional areas:
None.
Amount of litter movement (describe size and distance expected to travel):
Minimal and short.
Soil surface (top few mm) resistance to erosion (stability values are averages - most sites will show a range of values):
Stability class anticipated to be 5 to 6 at surface.
Soil surface structure and SOM content (include type of structure and A-horizon color and thickness):
A-horizon is 0 to 7 inches of gray clay with medium subangular blocky to moderate very fine granular structure. Surface horizons are hard, firm, very sticky, very plastic with common medium tubular pores. Some surfaces have few fine krotovinas with snail shell fragments. They have violent effervescence and are moderately alkaline.
Effect of community phase composition (relative proportion of different functional groups) and spatial distribution on infiltration and runoff:
High canopy, basal cover, and density with small interspaces should make rainfall impact negligible. This site has very deep, well drained soils with nearly level slopes but have high runoff due to the high clay content.
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 midgrasses >>

Sub-dominant:

Other:
Warm-season shortgrasses > Cool-season midgrasses > Perennial forbs > Trees > Shrubs/Vines

Additional:
Forbs make up 5% species composition while trees and shrubs/vines compose trace percent species composition.
Amount of plant mortality and decadence (include which functional groups are expected to show mortality or decadence):
Grasses will exhibit some mortality and decadence, though very slight.
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):
1,275 to 4,000 pounds per acre.
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:
Mesquite, prickly pear, golden weed, and white brush are primary invaders.
Perennial plant reproductive capability:
All species should be capable of plant reproduction, except during periods of prolonged drought conditions, heavy natural herbivory, or wildfires.

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Ecosystem states

1. Grassland

2. Shrubland

3. Seeded

T1A	-	Absence of disturbance and natural regeneration over time coupled with excessive grazing pressure
T1B	-	Excessive soil disturbance followed by seeding improved forage species
R2A	-	Reintroduction of historic disturbance return intervals
T2A	-	Excessive soil disturbance followed by seeding improved forage species
T3A	-	Absence of disturbance and natural regeneration over time coupled with excessive grazing pressure