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Conservation Service

Ecological site R081BY325TX

Clay Loam 19-23 PZ

Last updated: 9/19/2023
Accessed: 12/21/2024

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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): 081B–Edwards Plateau, Central Part

This area is entirely in south-central Texas. It makes up about 11,125 square miles (28,825 square kilometers). The towns of Fredericksburg, Junction, Menard, Rocksprings, and Sonora are in this MLRA. Interstate 10 crosses the middle part of the area. A few State parks and State historic sites are in this MLRA.

Classification relationships

USDA-Natural Resources Conservation Service, 2006.
-Major Land Resource Area (MLRA) 81B

Ecological site concept

The Clay Loam has deep, clay loam textures and has high vegetative production. Soils are generally brown, well drained, and moderately permeable.

Associated sites

R081BY334TX	Loamy Bottomland 19-23 PZ The Loamy Bottomland site may be encountered down slope from the Clay Loam site.
R081BY342TX	Shallow 19-23 PZ The Shallow site may be encountered on the adjacent slopes.
R081BY593TX	Limestone Hill 19-23 PZ The Limestone Hill site may be encountered uphill from the Clay Loam site.
R081BY323TX	Clay Flat 19-23 PZ The Clay Flat site is found in similar areas but has higher clay content in depressions.
R081BY336TX	Low Stony Hill 19-23 PZ The Low Stony Hill site is uphill and has shallow soils.
R081BY353TX	Very Shallow 19-23 PZ The Very Shallow site may be encountered on adjacent slopes or slightly upslope.

Similar sites

R081BY323TX	Clay Flat 19-23 PZ The Clay Flat site has higher clay content and is found in depressions.
R081BY333TX	Loamy 19-23 PZ The Loamy site has less than 35 percent clay.

R081BY323TX

Clay Flat 19-23 PZ

The Clay Flat site has higher clay content and is found in depressions.

R081BY333TX

Loamy 19-23 PZ

The Loamy site has less than 35 percent clay.

Table 1. Dominant plant species

Tree	Not specified
Shrub	Not specified
Herbaceous	(1) Bouteloua curtipendula (2) Schizachyrium scoparium

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Physiographic features

The Clay Loam occurs on stream terraces of piedmont alluvial plains below the limestone hills that are gently sloping to gently undulating. This site is usually found on plain surfaces, stream terraces and valleys. The elevation ranges from 1,500 feet to 2,800 feet above sea level. Slope ranges from 0 to 3 percent. The site is used mostly for rangeland while irrigated vegetables, cotton, corn, and grain sorghum are also planted.

Table 2. Representative physiographic features

Landforms	(1) Plateau > Stream terrace (2) Alluvial plain > Plain (3) River valley > Stream terrace
Runoff class	Low to medium
Flooding frequency	None
Ponding frequency	None
Elevation	1,500 – 2,800 ft
Slope	3%
Aspect	Aspect is not a significant factor

Table 3. Representative physiographic features (actual ranges)

Runoff class	Negligible to medium
Flooding frequency	Not specified
Ponding frequency	Not specified
Elevation	Not specified
Slope	Not specified

Climatic features

The climate in the MLRA 81B is subtropical subhumid on the eastern portion and subtropical steppe on the western portion of the MLRA. Winters are dry, and the summers are hot and humid. The precipitation increases from west to east and the temperatures increase from north to south. The area usually receives 65 to 70 percent sunshine each year. The majority of the rainfall occurs during the warm months of April to October. Most precipitation comes from thunderstorms that vary in the amount of water received and the areas covered. Spring is characterized by fluctuating patterns, but mild temperatures prevail. July and August are relatively dry and hot with little weather variability day-to-day. As summer progresses through fall, an increase of precipitation usually occurs in the eastern portions while a decrease of precipitation occurs to the west. Winter temperatures are mild, but polar Canadian air masses bring rapid drops in temperature. These cold spells last 2 or 3 days. Prevailing winds are southerly with March and April the windiest months.

Table 4. Representative climatic features

Frost-free period (characteristic range)	210-240 days
Freeze-free period (characteristic range)	240-280 days
Precipitation total (characteristic range)	19-24 in
Frost-free period (actual range)	210-240 days
Freeze-free period (actual range)	240-280 days
Precipitation total (actual range)	19-25 in
Frost-free period (average)	225 days
Freeze-free period (average)	260 days
Precipitation total (average)	22 in

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) CARTA VALLEY [USC00411492], Rocksprings, TX
(2) ELDORADO [USC00412809], Eldorado, TX
(3) SONORA [USC00418449], Sonora, TX
(4) OZONA [USC00416734], Ozona, TX
(5) BIG LAKE 2 [USC00410779], Big Lake, TX

Soil features

The soils are moderately deep or very deep, well drained, moderately slowly permeable and formed in calcareous loamy and clayey alluvium derived from limestone. In a representative profile, the parent material is calcareous alluvium weathered from limestone hills. The surface layer is dark grayish-brown, calcareous silty clay loam about 26 to 56 inches thick. Internal drainage is well drained and permeability is moderately slow. Soil series correlated to this site include: Angelo, Nuvalde, Rio Diablo, and Valera.

Table 5. Representative soil features

Parent material	(1) Alluvium – limestone
Surface texture	(1) Silty clay loam (2) Clay loam (3) Silty clay
Family particle size	(1) Fine-silty (2) Fine
Drainage class	Well drained
Permeability class	Moderately slow
Depth to restrictive layer	60 – 80 in
Soil depth	60 – 80 in
Surface fragment cover <=3"	5%
Surface fragment cover >3"	1%
Available water capacity (0-40in)	4.9 – 7.9 in
Calcium carbonate equivalent (0-40in)	5 – 40%
Electrical conductivity (0-40in)	2 mmhos/cm
Sodium adsorption ratio (0-40in)	Not specified
Soil reaction (1:1 water) (0-40in)	7.4 – 8.4
Subsurface fragment volume <=3" (4-40in)	15%
Subsurface fragment volume >3" (4-40in)	1%

Table 6. Representative soil features (actual values)

Drainage class	Not specified
Permeability class	Slow to moderate
Depth to restrictive layer	20 – 80 in
Soil depth	20 – 80 in
Surface fragment cover <=3"	Not specified
Surface fragment cover >3"	Not specified
Available water capacity (0-40in)	Not specified
Calcium carbonate equivalent (0-40in)	5 – 60%
Electrical conductivity (0-40in)	Not specified
Sodium adsorption ratio (0-40in)	Not specified
Soil reaction (1:1 water) (0-40in)	Not specified
Subsurface fragment volume <=3" (4-40in)	Not specified
Subsurface fragment volume >3" (4-40in)	Not specified

Ecological dynamics

The dynamics of the site are influenced by the varied semi-arid climate, topography, herbivory, periodic drought, and recurring fires. Most precipitation comes during the summer growing season (April to October) as convective rainstorms of short duration and high intensity. Hard freezes and severe extended droughts occur infrequently, but their effects influence the vegetation composition in the years following and magnify the effects of herbivory and fire.

The reference plant community of the Clay Loam site in MLRA 81B was a fire influenced Midgrass Prairie Community (1.1). The site is responsive to fire because of its nearly level topographic location, dry hot summers, dry winters and few barriers to fire. Fires, started by lightning or native Americans, would likely have been frequent, occurring every 7 to 12 years. Fires influenced the Clay Loam site by maintaining the fire climax grassland community with scattered mottes of trees and shrub vegetation. The soils have good water holding capacity and often receive extra runoff from upslope, making the site more productive than climate predicates. In reference conditions, the site is not subject to severe wind or water erosion. The semiarid climate with infrequent droughts predicates mid and short grasses that can withstand the droughts.

Since European settlement of the area in the 1800’s, many of the reference species have declined or increased, depending on their response to herbivory, reduction in frequency and intensity of fires, and land-use practices. Under heavy continuous livestock grazing, successional patterns tend to go toward woody and cool-season vegetation and more arid microclimates. Exact causes of vegetation change toward more woody species are subject to debate, but suspected causes include continued overgrazing, reduction of frequency and intensity of fire, changes in climate, and increases in atmospheric carbon dioxide concentration and nitrogen deposition since the industrial revolution. Regardless of the cause or causes of vegetation changes, overgrazing is a major factor in retrogression and plant species change due to selective removal of photosynthetic tissue by grazing herbivores.

When retrogression is livestock induced, the initial response is the decline of the dominants and an increase in less palatable subdominants. Initially, the mid and tallgrasses give way to less palatable mid and shortgrasses such as Arizona cottontop (Digitaria californica), cane bluestem (Bothriochloa barbinodis), silver bluestem (Bothriochloa laguroides), dropseeds (Sporobolus spp.), and less palatable forbs such as western indigo (Indigofera miniata), Hairy tubetongue (Siphonoglossa pilosella), and daleas (Dalea spp.). This opens the grass cover to increases or invasion by deep-rooted woody species such as live oaks (Quercus virginiana), mesquite (Prosopsis glandulosa), sumacs (Rhus spp.), juniper (Juniperus spp.), acacia (Acacia spp.), algerita (Mahonia trifoliata), and javelinabush (Condalia eriocoides).

In the Mixed-grass Savannah Community (1.2), primary production shifts from a midgrass prairie toward woody species and shortgrasses. Woody plant cover increases to 10 to 35 percent at the expense of the grass community, but primary production is stable, if not increased. The deeper-rooted woody plants are able to draw water from deeper soil depth. Litter and soil organic matter have changed little. The site takes on a look of a short and midgrass prairie being invaded by shrubs. At this stage, the trend toward shrubs can be reversed to a midgrass prairie with proper grazing management and brush management practices such as prescribed burning and individual plant treatment (IPT). If overgrazing continues and fire is reduced in intensity and frequency, the brush canopy will increase in size and density until the overstory canopy exceeds 40 percent. When this increase in overstory canopy occurs, the Mixed-Brush/Shortgrass Community (2.1) found in the Brushland State is entered.

Continued selective grazing causes the shorter grasses and low-quality annuals and forbs to replace the subdominant midgrasses and palatable forbs. Buffalograss (Bouteloua dactyloides), curlymesquite (Hilaria belangeri), Texas wintergrass (Nassella leucotricha), and low quality annual forbs will dominate the herbaceous understory. The overstory is dominated by live oaks, mesquite, or juniper. Mesquite and/or juniper generally dominate. In this state, common understory shrubs are pricklypear (Opuntia spp.), javelinabush (Condalia spp.), algerita (Mahonia trifoliata), bluewood condalia (Condalia hookeri var. hookeri), yucca (Yucca spp.), and acacia. Grass and forb production is severely reduced. Desertification is taking place resulting in the lowering of soil organic matter, decreased infiltration and water holding capacity. Shorter plants and less litter bring about more exposure of the soil surface to erosion.

Once the threshold of 40 percent woody plant cover is reached, the transition cannot be reversed without extensive brush management, range planting and grazing management. Without these expensive inputs, the Mixed-Brush/Shortgrass Community (2.1) continues to decline as a forage resource. The Mixedbrush/Shortgrass Community (2.1) can be restored with considerable input of energy and expense. With intensive brush management, range planting, prescribed grazing, and prescribed burning, the site can be returned to near reference conditions. Other alternatives include planting crops or pasture. The Converted Land Community (3.1) is a rather stable community if cropping is continuous and grazing management and brush management is practiced on pastureland. If cropland or pasture management is abandoned, these vegetative states revert to what is generally described as Abandoned or Go Back Land Community (3.2). The Go Back Land Community initially reflects the Mid and Shortgrass Savannah Community (1.2), because the community will initially support annual grasses and forbs along with invading mesquite, prickly pear, and other species. Loss of fertility, soil organic matter, and ground cover make these communities more susceptible to erosion.

State and transition model

More interactive model formats are also available. View Interactive Models
Click on state and transition labels to scroll to the respective text

Ecosystem states

1. Grassland

2. Brushland

3. Converted Land

T1A	-	Absence of disturbance and natural regeneration over time, may be coupled with excessive grazing pressure
T1B	-	Extensive soil disturbance followed by seeding
R2A	-	Reintroduction of historic disturbance return intervals
T2A	-	Extensive soil disturbance followed by seeding

State 1
Grassland

Dominant plant species

sideoats grama (Bouteloua curtipendula), grass
little bluestem (Schizachyrium scoparium), grass

Community 1.1
Midgrass Prairie

Figure 8. 1.1 Midgrass Prairie Community

The reference plant community is a fire-dependent midgrass community with less than five percent woody plant cover. The vegetative composition is 85 to 90 percent grasses, 5 to 10 percent forbs, and generally less than five percent trees and shrubs. Scattered trees or mottes of live oak (Quercus virginiana), hackberry (Celtis spp.), and western soapberry (Sapindus saponaria var. drummondii) interrupt the mostly open grassland. The typical Midgrass Prairie Community (1.1) was dominated by sideoats grama (Bouteloua curtipendula). Little bluestem (Schizachyrium scoparium), big bluestem (Andropogon gerardii), and Indiangrass (Sorgastrum nutans) were present in small amounts in more mesic locations. Subdominant species included cane and silver bluestems (Bothriochloa spp.), bristlegrass (Setaria spp.), Arizona cottontop (Digitaria californica), dropseeds (Sporobolus spp.), slim tridens, and rough tridens (Tridens spp.). Vine mesquite (Panicum obtusum), buffalograss (Bouteloua dactyloides), and curlymesquite (Hilaria belangeri) were the primary shortgrasses. The primary cool-season grasses were Texas wintergrass (Nassella leoucotricha), Canada wildrye (Elymus canadensis), and western wheatgrass (Pascopyrum smithii). Climax forbs included catclaw sensitivebriar (Mimosa nutallii), western indigo (Indigo spp.), bundleflower (Desmanthus spp.), snoutbean (Rhynchosia spp.), western ragweed (Ambrosia cumanensis), Engelmann’s daisy (Engelmannia peristenia), and dalea (Dalea spp.). Scattered mottes of live oak (Quercus virginiana), hackberry (Celtis spp.), and western soapberry (Sapindus saponaria var. drummondii) with several understory shrubs covered approximately five percent of the site. Typical shrubs and vines included bumelia, white shin oak, ephedra (Ephedra spp.), greenbriar (Smilax spp.), pricklyash (Zanthoxylum spp.), and white honeysuckle (Lonicera albiflora). This plant community evolved under the influence of the climate, short duration heavy use by large migrating herbivores followed by long rest periods and fire at 7 to 12-year intervals. This community can be maintained in stable condition with proper grazing management and prescribed burning. Overgrazing by any type of herbivores in conjunction with a decrease in intensity and frequency of burning will allow the transition to other vegetative states to occur.

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	1700	3230	3740
Forb	200	380	440
Shrub/Vine	60	114	132
Tree	40	76	88
Total	2000	3800	4400

Figure 10. Plant community growth curve (percent production by month). TX3615, Midgrass Dominant with Shortgrass and Scattered Shrubs. Midgrass dominant vegetation with shortgrasses and scattered 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
2	3	5	13	23	15	4	5	15	7	5	3

Community 1.2
Mid and Shortgrass Savannah

Figure 11. 1.2 Mid and Shortgrass Savannah Community

The Mid and Shortgrass Savannah Community (1.2) reflects the influence of suppression of fires and the effects of grazing on the more palatable species. The indigenous and invading woody plant canopy has increased due to an increase of species such as mesquite, juniper, acacia, algerita, and condalia. The more palatable tall and midgrasses are being replaced by subdominants such as cane and silver bluestem, bristlegrass, curlymesquite, Texas wintergrass, and less palatable forbs and annuals. Forage production is not detrimentally affected but primary production is shifting from grasses to woody species. Woody plant cover increases to 10 to 35 percent at the expense of the grass community. Nutrient cycling and water use is shifting toward the deeper-rooted woody perennials. Soil organic matter and litter are slightly less than in the reference community. The Midgrass Prairie Community (1.1) is also representative, in structure and species, of the community found on this site after brush management practices have been applied. The Mid and Shortgrass Savannah Community (1.2) is reversible with grazing management and prescribed burning practices until brush canopy exceeds 40 percent. When woody plant canopy exceeds 40 percent, the plant community crosses over to a threshold identified as the Brushland State. The Mixedbrush/Shortgrass Community (2.1) within the Shrubland State is not reversible to the Mixed Prairie Community (1.1) without extensive and expensive inputs.

Figure 12. 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)
Grass/Grasslike	1365	2080	2600
Shrub/Vine	420	640	800
Forb	210	320	400
Tree	105	160	200
Total	2100	3200	4000

Figure 13. Plant community growth curve (percent production by month). TX3610, Midgrass Savannah with woody encroachment. Midgrass savannah with woody encroachment. Tallgrasses decline in population and increase of woody canopy to 20%..

Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
J	F	M	A	M	J	J	A	S	O	N	D
3	3	5	13	22	15	5	3	15	7	5	4

Pathway 1.1A
Community 1.1 to 1.2

Midgrass Prairie

Mid and Shortgrass Savannah

This plant community evolved under the influence of the climate, short duration heavy use by large migrating herbivores followed by long rest periods and fire at 7 to 12-year intervals. This community can be maintained in stable condition with proper grazing management and prescribed burning. Overgrazing by any type of herbivores in conjunction with a decrease in intensity and frequency of burning will allow the transition to other vegetative states to occur.

Pathway 1.2A
Community 1.2 to 1.1

Mid and Shortgrass Savannah

Midgrass Prairie

Prescribed grazing, prescribed burning, and brush Management (IPT) are some desirable conservation practices to revert back to the Midgrass Prairie Community from the Mid/Shortgrass Savannah Community.

Conservation practices

Brush Management
Prescribed Burning
Prescribed Grazing

State 2
Brushland

Dominant plant species

oak (Quercus), tree
juniper (Juniperus), tree
mesquite (Prosopis), shrub

Community 2.1
Mixedbrush/Shortgrass

Figure 14. 2.1 Mixedbrush/Shortgrass Community

Continued overgrazing causes a shift from a Mid and Shortgrass Savannah Community (1.2) with 10 to 35 percent woody cover to a Mixedbrush/Shortgrass community (2.1) with over 40 percent canopy cover. The tree and brush canopy of the Mixedbrush/Shortgrass Community (2.1) exceeds 40 percent. Mesquite, and sometimes juniper, dominates the overstory with 50 percent species composition from trees. Common understory shrubs which makes up of 20 percent species composition are pricklypear, algerita, condalia, yucca, and tasajillo (Cylindropuntia leptocaulis). Shortgrasses and low-quality forbs replace the palatable midgrasses. Grasses, which makes up of 25 percent species composition, that are common for this plant community include Texas wintergrass, curlymesquite, buffalograss, Hall’s panicum (Panicum hallii), rough tridens (Tridens muticus var. muticus) slim tridens (Tridens muticus), tobosagrass (Pleuraphis muticus), and fall witchgrass (Digitaria cognata var. cognata). Common forbs, which makes up of 10 percent species composition, include dotted gayfeather (Liatris punctata var. punctata), orange zexmenia (Wedelia hispida), croton (Croton spp.), Western ragweed, prairie coneflower (Ratibida columnifera), and broomweed (Gutierrezia spp.). Annual broomweed (Gutierrezia texana) is also generally present. The tree and shrub canopy acts to intercept rainfall and increase evapotranspiration losses creating a more xeric microclimate and reducing soil moisture and infiltration. Desertification is ongoing. Soil fauna and litter are reduced exposing more soil surface to erosion in interstitial spaces. Without major brush management and grazing management inputs, the Brushland State cannot be reversed into a Grassland State. Without proper management, it will continue to thicken until it reaches maximum woody plant cover and stabilizes with the climate and soil. Although this state provides good habitat cover for wildlife, only limited preferred forage or browse is available for livestock or wildlife.

Figure 15. Annual production by plant type (representative values) or group (midpoint values)

Table 9. Annual production by plant type

Plant type	Low (lb/acre)	Representative value (lb/acre)	High (lb/acre)
Tree	800	1500	1950
Grass/Grasslike	400	750	975
Shrub/Vine	320	600	780
Forb	80	150	195
Total	1600	3000	3900

Figure 16. Plant community growth curve (percent production by month). TX3618, Mixedbrush/Shortgrass Community. Yearlong green forage due to shrubs and cool season species growth in winter and spring. Peak rainfall period from April through September provides most productivity during summer growing season..

Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
J	F	M	A	M	J	J	A	S	O	N	D
5	7	8	14	18	12	6	4	13	2	7	4

State 3
Converted Land

Dominant plant species

kleingrass (Panicum coloratum), grass
weeping lovegrass (Eragrostis curvula), grass

Community 3.1
Converted Land

Figure 17. 3.1 Converted Land Community - Cropland

Figure 18. 3.1 Converted Land Community - Pastureland

Many early settlers of the MLRA, having a farming background, cultivated small fields on the Clay Loam site and adjacent bottomlands for vegetable crops, grain, forage sorghum, and winter cereals for livestock forage. Many of the Clay Loam sites have been converted to cropland in the past. The climate of the central portion of the Edwards Plateau MLRA 81B is such that summer crops succeed only one in four or five years, so farming is not sustainable. Cropping small acreages is still practiced, however, for summer annual forage crops or winter small grain grazing, either for livestock grazing, grain harvesting, or planting for wildlife food plots on many ranches. Many fields, however, have been abandoned and let ‘go back’ to native range or planted to introduced grasses for pasture use. Abandoned cropland areas, or cleared areas, are often seeded to climax native species or introduced grass species such as Kleingrass (Panicum coloratum), blue panicum (Panicum antidotale) or weeping lovegrass (Eragrostis curvula). Herbage production on those seeded to adapted introduced grasses or native grasses reach peak production within a few years, if a full stand is established. In this case, herbage production will equal the reference conditions if species such as little bluestem or sideoats grama are seeded. Adapted introduced species plantings such as Kleingrass may surpass reference condition production. The practice of including adapted legumes or other forbs will enhance vegetative productivity and usefulness, especially for wildlife.

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

Figure 20. Plant community growth curve (percent production by month). TX3600, Cool Season Crops. Cool season species are planted in the fall for winter and spring growth. Species include wheat and oats..

Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
J	F	M	A	M	J	J	A	S	O	N	D
5	5	10	10	5	0	0	0	20	25	15	5

Figure 21. Plant community growth curve (percent production by month). TX3601, Warm Season Crops. Warm season species are planted in early spring. Their peak growth is in late May with a lesser peak in September. Forage and Grain sorghum that are planted during the warm season months..

Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
J	F	M	A	M	J	J	A	S	O	N	D
0	0	8	20	25	20	10	10	5	2	0	0

Figure 22. Plant community growth curve (percent production by month). TX3613, Reclaimed Land. Reclaimed Land seeded with native or introduced 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
3	3	5	13	22	15	5	3	15	7	5	4

Community 3.2
Abandoned Land

Abandoned or Go Back Land is a local name used to describe cropland fields that have been abandoned and undergoing secondary succession. The plant community consists of a mixture of native grasses, forbs, and shrubs. The community results from abandoning cropland and leaving the land idle without range planting or brush management. Weeds and brush from the adjacent rangeland will invade the abandoned cropland. The initial composition of abandoned fields on Clay Loam sites is annual, biennial, and weak perennial grasses and forbs. The species depends on the seed source from adjacent rangeland. The rate of succession depends on grazing management and drought frequency, but reestablishment of reference conditions takes many years. Without grazing management and brush management, brush species such as pricklypear, mesquite, and juniper will dominate before a climax grass community can be established. Biomass production will be limited in the early seral stage and increase as the climax community is approached. Brush management and grazing management are required to allow the field to go back to near reference conditions.

Figure 23. Annual production by plant type (representative values) or group (midpoint values)

Table 10. Annual production by plant type

Plant type	Low (lb/acre)	Representative value (lb/acre)	High (lb/acre)
Grass/Grasslike	550	990	1320
Forb	300	540	720
Shrub/Vine	100	180	240
Tree	50	90	120
Total	1000	1800	2400

Figure 24. Plant community growth curve (percent production by month). TX3619, Midgrass/Mixedbrush Community. Midgrass and Mixedbrush summer growth with some cool season grass growth..

Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
J	F	M	A	M	J	J	A	S	O	N	D
3	3	7	13	20	15	7	5	10	7	5	5

Pathway 3.1A
Community 3.1 to 3.2

Invasion of the seeded fields by brush such as mesquite, pricklypear, condalia, yucca, and juniper is common in this MLRA. Drought and reduced soil cover due to cropping and grazing and a nearby seed source trigger the invasions. The shrub seedlings that appear in seeded or abandoned fields are true seedlings established by seeds brought in by animals, water, or wind. The invading brush must be controlled with grazing management, prescribed burning or other brush management methods or the woody invaders will again dominate.

Pathway 3.2A
Community 3.2 to 3.1

With the implementation of various conservation practices such as prescribed grazing, range/pasture/cropland management, pasture planting, range planting, and crop cultivation, the Abandoned Land Community can be reverted to the Converted Land Community.

Conservation practices

Brush Management
Prescribed Burning
Range Planting
Prescribed Grazing

Transition T1A
State 1 to 2

The Mid and Shortgrass Savannah Community (1.2) is reversible with grazing management and prescribed burning practices until brush canopy exceeds 40 percent. When woody plant canopy exceeds 40 percent, the plant community crosses over to a threshold identified as the Brushland State. The Mixedbrush/Shortgrass Community (2.1) within the Shrubland State is not reversible to the Mixed Prairie Community (1.1) without extensive and expensive inputs.

Transition T1B
State 1 to 3

Brush management, pasture planting, range planting, and crop cultivation are some conservation practices that can shift from the Grassland State to the Converted Land State.

Restoration pathway R2A
State 2 to 1

Alternatives for restoration include: (a) brush management and seeding to return vegetation and grazing management and prescribed fire to maintain the desired community; (b) brush management, cultivation and cropping with adapted crops and/or (c) brush management and seeding with introduced pasture species followed by proper grazing and pasture management.

Conservation practices

Brush Management
Prescribed Burning
Range Planting
Prescribed Grazing

Transition T2A
State 2 to 3

Brush management, pasture planting, range planting, and crop cultivation are some conservation practices that can shift from the Grassland State to the Converted Land State.

Additional community tables

Table 11. Community 1.1 plant community composition

Group	Common name	Symbol	Scientific name	Annual production (lb/acre)	Foliar cover (%)
Grass/Grasslike
1	midgrass			500–1100
	sideoats grama	BOCU	Bouteloua curtipendula	500–1100	–
2	tallgrass			400–880
	big bluestem	ANGE	Andropogon gerardii	400–880	–
	plains lovegrass	ERIN	Eragrostis intermedia	400–880	–
	little bluestem	SCSC	Schizachyrium scoparium	400–880	–
	Indiangrass	SONU2	Sorghastrum nutans	400–880	–
3	midgrasses/shortgrasses			300–660
	threeawn	ARIST	Aristida	300–660	–
	cane bluestem	BOBA3	Bothriochloa barbinodis	300–660	–
	silver beardgrass	BOLAT	Bothriochloa laguroides ssp. torreyana	300–660	–
	tumble windmill grass	CHVE2	Chloris verticillata	300–660	–
	fall witchgrass	DICO6	Digitaria cognata	300–660	–
	Texas cupgrass	ERSE5	Eriochloa sericea	300–660	–
	green sprangletop	LEDU	Leptochloa dubia	300–660	–
	vine mesquite	PAOB	Panicum obtusum	300–660	–
	bristlegrass	SETAR	Setaria	300–660	–
	composite dropseed	SPCOC2	Sporobolus compositus var. compositus	300–660	–
	tridens	TRIDE	Tridens	300–660	–
	slim tridens	TRMU	Tridens muticus	300–660	–
	slim tridens	TRMUE	Tridens muticus var. elongatus	300–660	–
4	shortgrasses			400–880
	buffalograss	BODA2	Bouteloua dactyloides	400–880	–
	curly-mesquite	HIBE	Hilaria belangeri	400–880	–
5	cool-season grasses			100–220
	Canada wildrye	ELCA4	Elymus canadensis	100–220	–
	Texas wintergrass	NALE3	Nassella leucotricha	100–220	–
	western wheatgrass	PASM	Pascopyrum smithii	100–220	–
Forb
6	forbs			200–440
	Cuman ragweed	AMPS	Ambrosia psilostachya	200–440	–
	white sagebrush	ARLUM2	Artemisia ludoviciana ssp. mexicana	200–440	–
	greeneyes	BERLA	Berlandiera	200–440	–
	yellow sundrops	CASE12	Calylophus serrulatus	200–440	–
	prairie clover	DALEA	Dalea	200–440	–
	bundleflower	DESMA	Desmanthus	200–440	–
	Engelmann's daisy	ENPE4	Engelmannia peristenia	200–440	–
	eastern milkpea	GARE2	Galactia regularis	200–440	–
	Gregg's tube tongue	JUPI5	Justicia pilosella	200–440	–
	trailing krameria	KRLA	Krameria lanceolata	200–440	–
	dotted blazing star	LIPU	Liatris punctata	200–440	–
	Nuttall's sensitive-briar	MINU6	Mimosa nuttallii	200–440	–
	evening primrose	OENOT	Oenothera	200–440	–
	narrowleaf Indian breadroot	PELI10	Pediomelum linearifolium	200–440	–
	snoutbean	RHYNC2	Rhynchosia	200–440	–
	wild petunia	RUELL	Ruellia	200–440	–
	awnless bushsunflower	SICA7	Simsia calva	200–440	–
	fuzzybean	STROP	Strophostyles	200–440	–
	vervain	VERBE	Verbena	200–440	–
	creepingoxeye	WEDEL	Wedelia	200–440	–
Shrub/Vine
7	shrubs/vines			60–132
	snakewood	CONDA	Condalia	60–132	–
	tree cholla	CYIMI	Cylindropuntia imbricata var. imbricata	60–132	–
	Christmas cactus	CYLE8	Cylindropuntia leptocaulis	60–132	–
	jointfir	EPHED	Ephedra	60–132	–
	stretchberry	FOPU2	Forestiera pubescens	60–132	–
	algerita	MATR3	Mahonia trifoliolata	60–132	–
	pricklypear	OPUNT	Opuntia	60–132	–
	sumac	RHUS	Rhus	60–132	–
	bully	SIDER2	Sideroxylon	60–132	–
	greenbrier	SMILA2	Smilax	60–132	–
Tree
8	trees			40–88
	pecan	CAIL2	Carya illinoinensis	40–88	–
	hackberry	CELTI	Celtis	40–88	–
	little walnut	JUMI	Juglans microcarpa	40–88	–
	Texas mulberry	MOMI	Morus microphylla	40–88	–
	mesquite	PROSO	Prosopis	40–88	–
	live oak	QUVI	Quercus virginiana	40–88	–
	western soapberry	SASAD	Sapindus saponaria var. drummondii	40–88	–
	elm	ULMUS	Ulmus	40–88	–

Interpretations

Animal community

Many types of wildlife use Clay Loams in conjunction with adjacent Ecological Sites. Grassland insects, reptiles, birds, and mammals frequent the site. Small mammals include many kinds of rodents, jackrabbit, cottontail rabbit, raccoon, skunk, opossum and armadillo. Predators include coyote, red fox, gray fox, bobcat and occasionally mountain lion. Many types of birds including game birds, songbirds, and birds of prey are indigenous. Most are still plentiful. Bison and pronghorn antelope, however, are no longer present, but white-tailed and many species of exotic deer utilize the Clay Loam site in its various states. Deer, turkey and quail particularly favor the habitat provided by the Mid and Shortgrass Savannah Community (2). Deer, turkey, quail, and dove hunting is an important sport, or commercial enterprise, providing considerable income to land owners.

The site in reference condition is very suited to primary grass eaters such as cattle. As retrogression occurs and woody plants invade, the site becomes better habitat for sheep, goats, deer and other wildlife because of the browse and cool-season grasses. Cattle, sheep, and goats should be stocked in proportion to the available grass, forb, and browse production, keeping deer competition for forbs and browse in mind. If the animal numbers are not kept in balance with herbage and browse production through proper grazing management and good wildlife population management, the late Mixedbrush/Shortgrass Community will have little to offer as habitat except cover.

Hydrological functions

The Clay Loam ecological site is a well-drained, very shallow to very deep upland. Its soils are moderately to slowly permeable, but runoff is slow due to gentle slopes. Under reference conditions, the grassland vegetation intercepted and utilized much of the incoming rainfall in the soil solum. Only during extended rains or heavy thunderstorms was there much runoff. Litter and soil movement is slight. Soil cover and organic matter decrease, and surface runoff increases as the Midgrass Prairie Community transitions to the Mid and Shortgrass Savannah Community. These processes continue in the interstitial spaces in the Mixedbrush/Shortgrass Community phase. Once the Mixedbrush/Shortgrass Community canopy surpasses 50 percent the hydrology and ecological processes, nutrient cycling, and energy flow, stabilize within the woody plant canopy. Evaporation and interception losses are higher, however, resulting in less moisture reaching the soil. If overgrazing continues, the shortgrass community deteriorates further, and desertification processes continue. Biomass production is reduced relative to the reference condition and forage production has shifted from primarily grasses to primarily woody plants. The deeper-rooted woody plants are able to extract water from greater depths than grasses of the reference did, so less water will be available for aquifer recharge. The woody plants compete for moisture with the remaining grasses and forbs further reducing production and ground cover in openings. Decreased litter and more bare ground allow erosion from soils in openings between trees.

Recreational uses

The Clay Loam site is well suited for many outdoor recreational uses including recreational hunting, hiking, camping, equestrian and bird watching. Clay Loam, along with adjacent upland sites and Loamy Bottomland site, provide diverse scenic beauty and many opportunities for recreating and hunting.

Wood products

Posts and specialty wood products are made from juniper, mesquite, oak, and many shrubs. Mesquite and oak are used for firewood and charcoal.

Other products

Jams and jellies are made from many fruit-bearing species. Seeds may be harvested from plants for commercial sale. Grasses and forbs are harvested by the dried-plant industry for sale in dried flower arrangements. Honeybees are utilized to harvest honey from the many flowering plants, such as mesquite.

Supporting information

Inventory data references

Information presented was derived from the revised Clay Loam Range Site Description, literature, limited NRCS clipping data (417s), field observations, experience and personal contacts with range-trained personnel. Photos by J. L. Schuster.

Other references

Archer, S. 1994. Woody plant encroachment into southwestern grasslands and savannas: Rates, patterns, and proximate causes. Ecological implications of livestock herbivory in the West, 13-68.

Archer, S. and F. E. Smeins. 1991. Ecosystem-level processes. Grazing Management: An Ecological Perspective. Edited by R.K. Heischmidt and J.W. Stuth. Timber Press, Portland, OR.

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. Journal of Range Management, 56(2):114-126.

Bracht, V. 1931. Texas in 1848. German-Texan Heritage Society, Department of Modern Languages, Southwest Texas State University, San Marcos, TX.

Bray, W. L. 1904. The timber of the Edwards Plateau of Texas: Its relations to climate, water supply, and soil. No. 49. US Department of Agriculture, Bureau of Forestry.

Briske, D. D., S. D. Fuhlendorf, and F. E. Smeins. 2005. State-and-transition models, thresholds, and rangeland health: A synthesis of ecological concepts and perspectives. Rangeland Ecology and Management, 58(1):1-10.

Brothers, A., M. E. Ray Jr., and C. McTee. 1998. Producing quality whitetails, revised edition. Texas Wildlife Association, San Antonio, TX.

Brown, J. K. and J. K. Smith. 2000. Wildland fire in ecosystems, effects of fire on flora. Gen. Tech. Rep. RMRS-GTR-42-vol. 2. Ogden, UT: US Department of Agriculture, Forest Service, Rocky Mountain Research Station, 257:42.

Davis, W. B. 1974. The Mammals of Texas. Texas Parks and Wildlife Department, 41.

Foster, J. H. 1917. The spread of timbered areas in central Texas. Journal of Forestry 15(4):442-445.

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

Gould, F. W. 1975. The grasses of Texas. The Texas Agricultural Experiment Station, Texas A&M University Press, College Station, TX.

Hatch, S. L. and J. Pluhar. 1993. Texas Range Plants. Texas A&M University Press, College Station, TX.

Hamilton, W. and D. Ueckert. 2005. Rangeland woody plant control--past, present, and future. Texas A&M University Press. College Station, TX.

Hart, C. R., A. McGinty, and B. B. Carpenter. 1998. Toxic plants handbook: Integrated management strategies for West Texas. Texas Agricultural Extension Service, The Texas A&M University, College Station, TX.

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

Loughmiller, C. and L. Loughmiller. 1984. Texas wildflowers. University of Texas Press, Austin, TX.

Milchunas, D. G. 2006. Responses of plant communities to grazing in the southwestern United States. Gen. Tech. Rep RMRS-GTR-169. Fort Collins, CO: US Department of Agriculture, Forest Service, Rocky Mountain Research Station, 126:169.

Niehaus, T. F. 1998. A field guide to Southwestern and Texas wildflowers (Vol. 31). Houghton Mifflin Harcourt, Boston, MA.

Ramsey, C. W. 1970. Texotics. Texas Parks and Wildlife Department, Austin, TX.

Roemer, F. translated by O. Mueller. 1995. Roemer’s Texas, 1845 to 1847. Texas Wildlife Association, San Antonio, 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.

Smeins, F. E., S. Fuhlendorf, and C. Taylor, Jr. 1997. Environmental and land use changes: A long term perspective. Juniper Symposium, 1-21.

Taylor, C. A. and F. E. Smeins. 1994. A history of land use of the Edwards Plateau and its effect on the native vegetation. Juniper Symposium, 94:2.

Thurow, T. L. 1991. Hydrology and erosion. Grazing Management: An Ecological Perspective. Edited by R.K. Heitschmidt and J.W. Stuth. Timber Press, Portland, OR.

Tull, D. and G. O. Miller. 1991. A field guide to wildflowers, trees and shrubs of Texas. Texas Monthly Publishing, Houston, TX.

USDA-NRCS. 1997. National range and pasture handbook. Washington, DC: United States Department of Agriculture. Natural Resources Conservation Service, Grazing Lands Technology Institute.

Weniger, D. 1997. The explorers’ Texas: The animals they found. Eakin Press, Austin, TX.

Weniger, D. 1984. The explorers’ Texas: The lands and waters. Eakin Press, Austin, TX.

Vines, R. A. 1984. Trees of Central Texas. University of Texas Press, Austin, TX.

Vines, R. A. 1960. Trees, shrubs and vines of the Southwest. University of Texas Press, Austin, TX.

Contributors

Dr. Joseph Schuster, Range & Wildlife Habitat Consultants, LLC, Bryan, TX
Mark Moseley, RMS, NRCS, Boerne, TX
Edits by Travis Waiser, MLRA Leader, NRCS, Kerrville, TX

Approval

Bryan Christensen, 9/19/2023

Acknowledgments

Technical Review:
Homer Sanchez, State RMS, NRCS, Temple, TX
Charles Anderson, Zone RMS, NRCS, San Angelo, TX
Justin Clary, RMS, NRCS, Temple, TX

QC/QA completed by:
Bryan Christensen, SRESS, NRCS, Temple, TX
Erin Hourihan, ESDQS, NRCS, Temple, TX

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)	Joe Franklin, Zone RMS, NRCS, San Angelo, TX
Contact for lead author	325-944-0147
Date	12/01/2005
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 to slight. Site may receive runoff from adjacent sites.
Number and height of erosional pedestals or terracettes:
None to slight. Minimal pedestals or terracettes due to erosion.
Bare ground from Ecological Site Description or other studies (rock, litter, lichen, moss, plant canopy are not bare ground):
Less than 10 percent bare ground. Small and non-connected areas.
Number of gullies and erosion associated with gullies:
None.
Extent of wind scoured, blowouts and/or depositional areas:
None to slight. Wind erosion hazard of soil is slight.
Amount of litter movement (describe size and distance expected to travel):
Minimal movement of fine litter for short distances.
Soil surface (top few mm) resistance to erosion (stability values are averages - most sites will show a range of values):
Erosion stability values estimated at 5 to 6. Water erosion hazard of soil is slight.
Soil surface structure and SOM content (include type of structure and A-horizon color and thickness):
Angelo soil is grayish brown silty clay loam to 8 inches and brown clay loam in 8 to 14 inches depth. The surface layer is weak fine granular and subangular blocky. Many fine roots and worm casts. SOM is high.
Effect of community phase composition (relative proportion of different functional groups) and spatial distribution on infiltration and runoff:
The reference state provides good plant distribution and soil over so provides excellent infiltration. Under normal rainfall runoff is essentially nil but when rainfall exceeds site's ability to hold water, the runoff is free of erosive action.
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 midgrases

Sub-dominant:
Warm-season tallgrasses Warm-season shortgrasses Forbs

Other:
Cool-season grasses Shrubs/Vines Trees

Additional:
Amount of plant mortality and decadence (include which functional groups are expected to show mortality or decadence):
Minimal. Grasses will almost always show some mortality and decadence, especially under drought conditions.
Average percent litter cover (%) and depth ( in):
Interspaces between plant canopies essentially covered with various sizes of litter and mulch.
Expected annual annual-production (this is TOTAL above-ground annual-production, not just forage annual-production):
2,000 pounds per acre in years with below average moisture, 3,800 pounds per acre in average moisture, and 4,400 pounds per acre in above average moisture years. Site may receive extra moisture from upslope sites and be highly productive in wet 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:
Mesquite, pricklypear, broom snakeweed, agarito, acacia, condalia and annual broomweed.
Perennial plant reproductive capability:
Good. All species should be capable of reproducing except during periods of prolonged drought, heavy natural herbivory or intense fire. Recovery from these disturbances will take 2 to 5 years.

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Ecosystem states

1. Grassland

2. Brushland

3. Converted Land

T1A	-	Absence of disturbance and natural regeneration over time, may be coupled with excessive grazing pressure
T1B	-	Extensive soil disturbance followed by seeding
R2A	-	Reintroduction of historic disturbance return intervals
T2A	-	Extensive soil disturbance followed by seeding