State 1
Grassland

Community 1.1
Mid and Tallgrass Prairie

Figure 8. 1. Mid and Tallgrass Prairie Community

The reference plant community for this site is a fire induced mid and tallgrass prairie. Live oak was widely scattered on ridges and along draws, but made up less than three percent canopy. Woody plant production consisted mostly of shrubs. Little bluestem (Schizachyrium scoparium) was the dominant grass on the east side of the MLRA. Big bluestem (Andropogon gerardii) and Indiangrass (Sorghastrum nutans) occupied favorable micro-sites and were locally dominant. In the western half, sideoats grama (Bouteloua curtipendula) and little bluestem were the co-dominants and big bluestem and Indiangrass were seldom present. Also occurring on the site but in smaller amounts were meadow dropseed (Sporobolus asper var. asper), feathery bluestems (Bothriochloa spp.), Texas wintergrass (Nassella leucotricha), Texas cupgrass (Eriochloa sericea), and a number of shortgrasses. Typical forbs were Maximilian sunflower (Helianthus maximiliani), Engelmann’s daisy (Engelmannia peristenia), wooly-white (Hymenopappus spp.), half-shrub sundrop (Calylophus serrulatus), catclaw sensitivebriar (Mimosa nuttallii), and bundleflower (Desmanthus spp.). Shrubs included sumacs (Rhus spp.), Texas kidneywood (Eysenhardtia texana), greenbriar (Smilax spp.), and bumelia (Sideroxylon spp.). Live oak (Quercus virginiana), hackberry (Celtis spp.), Texas redbud (Cercis canadensis var. texensis), and mesquite (Prosopsis glandulosa) were typical tree species. The Mid and Tallgrass Prairie Community (1.1) produced approximately 1,800 to 3,500 pounds of biomass annually, depending upon the amount of precipitation. Annual production declines from east to west due to decline in precipitation. Grasses made up to 85 to 90 percent of the total annual production. The mid and tallgrasses aided in the infiltration of rainfall into the slowly permeable soil and reduced runoff. The Mid and Tallgrass Community (1.1) furnished good habitat for grass and forb eaters such as bison and pronghorn antelope.

Community 1.2
Midgrass/Oak Savannah

Figure 11. 1.2 Midgrass/Oak Savannah Community.

The Midgrass/Oak Savannah Community (1.2) is a midgrass dominated grassland being encroached by indigenous or invading woody species that had been held at low densities by repeated fires and competition from a vigorous grass component. The overstory is primarily live oak. Numerous brushy species, including juniper and mesquite, are increasing in density because overgrazing by livestock has reduced grass cover, exposed some soil and reduced fine fuel for fire. In this phase, the increasing woody species are generally less than five feet tall and are subject to control by fire and improved grazing management. The woody canopy varies between 10 and 25 percent depending on severity of grazing, time since last burned and availability of invading species. Typically, oaks increase in size and mesquite and/or juniper increase in density. Less preferred brushy species such as bumelia, Texas persimmon (Diospyros texana), spiny hackberry (Celtis pallida), sumacs (Sumac spp.), condalia (Condalia spp.), elbowbush (Forestiera pubescens), and feather dalea (Dalea spp.) also increase. The prairie becomes a savannah being encroached by woody species. The preferred tall grasses are being replaced by the more grazing resistant midgrasses, although little bluestem persists. Important grasses are sideoats grama, tall dropseed, meadow dropseed, vine mesquite (Panicum obtusum), plains lovegrass (Eragrostis intermedia), Texas cupgrass (Eriochloa sericea), and feathery bluestems (Bothriochloa spp.). Most of the reference forbs still exist. Annual primary production ranges from 1,600 to 3,500 pounds per acre depending on precipitation amounts and the soil series, with production generally decreasing from the eastern boundary of the MLRA to the western boundary of the MLRA. Forage production is predominantly grass species. Heavy abusive grazing by livestock and wildlife has reduced plant cover, litter and mulch and has increased bare ground exposing the soil to some erosion. There could be some mulch and litter movement during rainstorms but due to gentle slopes, little soil movement would take place in this vegetation phase.

Pathway 1.1A
Community 1.1 to 1.2

Mid and Tallgrass Prairie

Midgrass/Oak Savannah

With overgrazing, decrease in intensity and frequency of fires and no brush management, this plant community transitions very quickly into the Midgrass/Oak Savannah Community.

Pathway 1.2A
Community 1.2 to 1.1

Midgrass/Oak Savannah

Mid and Tallgrass Prairie

With brush management, proper grazing, and prescribed burning, the Midgrass/Oak Savannah will transition back to the Mid and Tallgrass Prairie Community.

State 2
Woodland

Community 2.1
Oak/Mixed-brush/Shortgrass

Figure 13. 2.1 Oak/Mixed-brush/Shortgrass Community.

The Oak/Mixedbrush Plant community presents a 25 percent or greater woody plant canopy dominated by live oak with mixed brush, especially Ashe juniper and/or mesquite increasing in density and size. It is the result of selective overgrazing by livestock and deer and the differential response of plants to defoliation. There is a decline in diversity of the grassland component and an increase in woody species and unpalatable forbs. Primary production has decreased due to decline in soil structure and organic matter and has shifted toward the woody component. All, except the more palatable woody species, have increased in size. Mesquite was an early increaser throughout the MLRA. Ashe juniper spreads throughout the eastern boundary and some redberry juniper (Juniperus pinchotii) is found in the western boundary. Many of the climax shrubs are present. Typically, algerita (Mahonia trifoliata), Texas persimmon, prickly pear (Opuntia spp.), condalia (Condalia spp.), shin oak (Quercus sinuata), and sumac (Sumac spp.) form thickets. Remnants of reference condition grasses and forbs and unpalatable invaders occupy the interspaces between trees and shrubs. Cool-season grasses such as Texas wintergrass can be found under and around woody plants. Because of grazing pressure and competition for nutrients and water from the woody plants, the grassland component shows lack of plant vigor and productivity. Common herbaceous species are three-awns (Aristida spp.), hairy tridens (Erioneuron pilosum), hairy grama (Bouteloua hirsuta), sedges (Carex spp.), Queen’s delight (Stillingia sylvatica), prairie coneflower (Ratibida columnifera), Texas grama (Bouteloua rigidiseta var. rigidiseta), and red grama (Bouteloua trifida). As the grassland vegetation declines, more soil is exposed to crusting and erosion. During this phase, soil and water erosion can be high. High interception losses by the increasing woody canopy combined with evaporation and runoff can reduce the effectiveness of rainfall. Soil organic matter and structure decline in the interspaces but conditions may improve under woody plant cover. Some soil loss could occur during heavy rainfall events. Annual primary production is approximately 1,000 to 3,000 pounds per acre. In this stage, production is balanced between herbaceous plants and woody plants. Browsing animals such as goats and deer find fair food value if browsing has not been excessive. Forage quality for cattle is low. Unless brush management and good grazing management are applied at this stage, the transition toward dense woodland community will continue. The trend cannot be reversed with good grazing management practices alone.

Community 2.2
Oak/Juniper/Mesquite Woodland

Figure 15. 2.2 Oak/Juniper/Mesquite Woodland Community.

Oak, juniper and/or mesquite dominate the Oak/Juniper/Mesquite Woodland Community. Juniper is more prevalent in the eastern portion of the MLRA. With the associated brushy understory shrubs, the woody canopy can approach 100 percent ground cover with continued heavy grazing. Common understory shrubs are pricklypear (Opuntia spp.), algerita (Mahonia trifoliata), condalia (Condalia spp.), yucca (Yucca spp.), Texas persimmon (Diospyros texana), elbowbush (Forestiera pubescens), pricklyash (Zanthoxylum spp.), and tasajillo (Opuntia leptocaulis). Shortgrasses and low quality annual and perennial forbs occupy the tree interspaces. Characteristic grasses are Texas wintergrass, curlymesquite, buffalograss, Hall’s panicum (Panicum hallii var. hallii), rough tridens (Tridens muticus var. muticus), slim tridens (Tridens muticus), tobosagrass (Pleuraphis mutica), and fall witchgrass (Digitaria cognata). Grasses and forbs make up 25 percent or less of the annual biomass production. Common forbs include dotted gayfeather (Liatris punctata var. punctata), orange zexmenia (Wedelia hispida), croton (Croton spp.), western ragweed (Ambrosia psilostachya), prairie coneflower (Ratibida columnifera), and broomweed (Gutierrezia spp.). The tree and shrub canopy acts to intercept rainfall and increase evapotranspiration losses, creating a more xeric microclimate. Soil fauna and litter are reduced exposing more soil surface to erosion in the few interstitial spaces. However, within the woody canopy hydrologic processes stabilize and soil organic matter and mulch begin to increase and eventually stabilize under the woodland. Without major brush control and management inputs, this plant community cannot be reversed. Without proper management, the site will continue to thicketize until it 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.

Pathway 2.1A
Community 2.1 to 2.2

Oak/Mixed-brush/Shortgrass

Oak/Juniper/Mesquite Woodland

With heavy abusive grazing, no fire, no brush management, and invasion of brush species, the Mixed-brush/Shortgrass Community will shift to the Mixed-brush Shrubland Community.

Pathway 2.2A
Community 2.2 to 2.1

Oak/Juniper/Mesquite Woodland

Oak/Mixed-brush/Shortgrass

With prescribed grazing, prescribed burning, and brush management (IPT) conservation practices, the Mixed-brush Shrubland Community can revert back to Mixed-brush/Shortgrass Community.

State 3
Converted Land

Community 3.1
Converted Land

Figure 17. 3.1 Converted Land Community.

Early settlers of the MLRA, having farming background, cultivated small fields for vegetable crops, grain, forage sorghum, and winter cereals for livestock forage. Many of the Shallow sites were converted to cropland. In Edwards Plateau summer crops succeed only one in every 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. Cropland fields are used for livestock grazing, grain harvesting or wildlife food plots on many ranches. Many fields, however, have been abandoned and let ‘go back’ to native range or planted to native or introduced grasses for pasture. Abandoned cropland areas, or woodland areas, are often cleared and plowed for seeding to native or introduced 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 community if species such as little bluestem or sideoats grama are seeded. Adapted introduced species plantings such as Kleingrass may surpass reference community production. The practice of including adapted legumes or other forbs will enhance productivity and usefulness, especially for wildlife.

Community 3.2
Abandoned Land

The Abandoned Land Community describes cropland fields that have been abandoned and are undergoing secondary succession. The ‘go back land’ results from abandoning cropped land and leaving it idle without seeding or brush management. Settlers cultivated many areas of the Shallow Ecological Site because of their gentle slopes, loamy soils and location. Many cropland fields have since been abandoned. The abandoned cropland will be invaded by brush from the adjacent rangeland. The initial composition of abandoned fields on the Shallow site is composed of 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 community species takes many years. Without grazing management and brush management practices, brush species such as pricklypear, mesquite, and juniper will dominate the site before a grass community can become established. Biomass production will be limited in the early seral stage and increase as the reference community is approached. Brush management and grazing management are necessary to allow the field to ‘go back’ near reference community conditions.

Pathway 3.1A
Community 3.1 to 3.2

Invasion of the seeded fields by brush 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.

Transition T1A
State 1 to 2

The changes in species composition are small initially, but unless proper grazing and prescribed burning are applied; the woody species continue to increase in size and density. When the canopy of the woody plants becomes dense enough (25 percent) and tall enough (greater than five feet) to suppress grass growth and resist fire damage, a threshold in ecological succession is crossed. The Midgrass/Oak Savannah Community transitions into the Oak/Mixedbrush Shortgrass Community. Normal range management practices, such as proper grazing and prescribed burning, cannot reverse the trend to tallgrass dominance.

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

With reclamation, prescribed grazing, prescribed burning, brush management, and range planting, the Woodland State can shift to the Grassland State.

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.