State 1
Hardwood Grassland

Community 1.1
Tallgrass Hardwood

Figure 8. 1.1 Tallgrass Hardwood Community

The Loamy Bottomland is a tallgrass hardwood complex supporting trees, a mixture of tall and midgrasses, and excellent forb and shrub plant diversity. Pecan (Carya illinioensis), live oak (Quercus virginiana), Chinkapin oak (Quercus muehlenbergii), and bald cypress (Taxodium distichum) are found along the stream bank and bottom terrace. Elm (Ulmus spp.), hackberry (Celtis spp.), and American sycamore (Platanus occidentalis) are also common. Typical shrubs found at the site were bumelia (Sideroxylon spp.), elbowbush (Forestiera pubescens), brickellbush (Brickellia spp.), and Mexican buckeye (Ungnadia speciosa). Many vines such as grape (Vitis spp.) and greenbriar (Smilax spp.) are common in the woodland areas. Woody species decreases in density and canopy cover as the distance from the stream bank increases, taking on a savannah structure. Tallgrasses, shrubs, and forbs thrived in the open grassland and in the interspaces and beneath the trees, creating a complex of grassland and woodland. This pattern varies depending on soil, grazing regime of and fire frequency. Fires are postulated to have occurred at 7 to 12-year intervals in this region and are thought to have exerted the greatest influence in shaping the plant community.

Little bluestem (Schizachyrium scoparium), Indiangrass (Sorgastrum nutans), switchgrass (Panicum virgatum), Eastern gamagrass (Tripsacum dactyloides), and wildryes (Elymus spp.) dominated the grassland. Maximilian sunflower (Helianthus maximiliani), bundleflower (Desmanthus spp.), and Engelmann’s daisy (Engelmannia peristenia) are important forbs. Numerous perennial forbs, grasses, shrubs, and woody vines contribute to the diversity of the understory vegetation. Switchgrass and Eastern gamagrass, along with numerous sedges (Carex spp.), spikerushes (Eleocharis spp.), flatsedges (Cyperus spp.) and brush species occurr immediately adjacent to the watercourse. These species have a positive effect on stream bank stabilization during flooding events. The deep fertile soils and runoff from adjacent uplands and occasional flooding cause higher productivity than the surrounding ecological sites. Primary above ground production ranges from 2,500 to 6,000 pounds per acre annually depending on soils and precipitation events. The grassland component made up 80 to 90 percent of the herbage production.

Continued overgrazing of this site with livestock will cause a vegetation transition (retrogression) from tallgrasses to midgrasses to woodland with lower seral species and lower forage production. The transition to a woodland state can be halted or reversed by applying moderately intensive management practices like prescribed grazing and prescribed burning until the woody canopy reduces burn effectiveness. The threshold for this occurrence is generally between 30 and 40 percent woody cover. It occurs when there is not enough fine fuel produced by the grass component to control or suppress the invading species. Once that threshold is breached, the plant community transitions to the Mixed-grass Hardwood Complex Community (1.2).

Community 1.2
Mixed-grass Hardwood Complex

Figure 11. 1.2 Mixed-grass Hardwood Complex Community

The Mixed-grass Hardwood Complex Community (1.2) reflects the results of the suppression of fires and the effects of overgrazing on the more palatable species. Indigenous and invading woody plants have increased in density and stature. The hardwood overstory expands in size and density. Mesquite, Ashe juniper and Texas persimmon (Diospyros texana) are the more common invaders. The more palatable tall and mid grasses are being replaced by subdominants such as feathery bluestems (Bothriochloa spp.), bristlegrass (Setaria spp.), Texas wintergrass (Nassella leucotricha), and less palatable forbs and annuals. Forage production is not significantly affected but primary production is shifting to the less palatable or more grazing resistant species.

Annual primary production ranges from 2,300 to 5,500 pounds per acre annually with approximately 65 percent being produced by the grassland component. Nutrient cycling and water use are shifting toward the deeper-rooted woody perennials. Soil organic matter and litter are slightly less than were present in the reference community. The Mixed-grass Hardwood Complex Community (1.2) is reversible with prescribed grazing management and prescribed burning practices until the woody canopy exceeds 35 percent. Once woody plant canopy exceeds 35 percent, the plant community crosses the threshold to the Bottomland Hardwood Community (2.1).

Pathway 1.1A
Community 1.1 to 1.2

Tallgrass Hardwood

Mixed-grass Hardwood Complex

Heavy abusive grazing, no fire, no brush management, and invasion of brush species has shifted from the Tallgrass Hardwood Community to the Mixed-grass Hardwood Community.

Pathway 1.2A
Community 1.2 to 1.1

Mixed-grass Hardwood Complex

Tallgrass Hardwood

Prescribed grazing, prescribed burning, brush management, and IPT are several conservation practices that could be applied to revert back to the Tallgrass Hardwood Community from the Mixed-grass Hardwood Community.

State 2
Hardwood Woodland

Community 2.1
Bottomland Hardwood

Figure 14. 2.1 Bottomland Hardwood Community

Continued livestock overgrazing causes a shift from a Mixed-grass Hardwood Complex Community (1.2) with 15 to 35 percent woody cover to a Bottomland Hardwood Community (2.1) with over 40 percent cover. During this retrogression process, there is a decline in the grassland component. With decreasing amounts of grass, there is a corresponding decrease in ground cover, litter, mulch, and soil organic matter. Soil structure declines and the exposed soil surface is subject to crusting and erosion. Litter and soil losses occur during floods. Annual primary production of the Bottomland Hardwood Community (2.1) can range from as low as 2,000 per acre in dry years to over 5,000 pounds per acre in good moisture years. Grasses and forbs provide less than 35 percent of this production. If the Bottomland Hardwood Community is the result of long term overgrazing by livestock, the remaining grass, forb, and shrub species are generally low-quality forage plants, further reducing the value of this plant community as rangeland.

With time and no tree or shrub control, the canopy can approach 100 percent cover. Bald cypress, pecan, oaks, hackberry, and elms dominate the overstory. Unless removed for lumber, bald cypress generally dominates along the stream edge. Pecan groves with inclusions of oaks, hackberry, and elm are typical on second and third terraces. Many sites have had trees removed for lumber. Ashe juniper and sometimes mesquite form dense thickets where the hardwoods are not too dense. Texas persimmon is found along the outer edges where the site meets Clay loam or Adobe sites. Common understory shrubs are yucca (Yucca spp.), elbowbush, Texas kidneywood (Eysenhardtia texana), ampelopsis (Ampelopsis spp.), grape (Vitis spp.), and Mexican buckeye. Mid and shortgrasses and low-quality forbs replace the most palatable species. Grasses that are common for this plant community include Texas wintergrass, Arizona cottontop (Digitaria californica), broadleaf woodoats (Chasmanthium latifolium), and buffalograss (Bouteloua dactyloides). The grasses and forbs in this plant community make up less than 25 percent of the annual biomass production. Common forbs include asters (Aster spp.), white crown-beard (Verbesina virginica), Ruellia (Ruellia spp.), orange zexmenia (Wedelia hispida), verbena (Verbena spp.), Western ragweed (Ambrosia psilostachya), prairie coneflower (Ratibida columnifera), and Western indigo (Indigofera spp.).

The tree and shrub canopy acts to intercept rainfall and increase evapotranspiration losses creating a more xeric microclimate and reducing soil moisture and infiltration. Soil fauna and litter are reduced exposing more soil surface to erosion in interstitial spaces until the canopy closes. Without major brush management and grazing management inputs, the Bottomland Hardwood Community cannot be reversed into a grassland state. It will continue to become dense woodland 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. Alternatives for restoration include, tree removal, brush management, and revegetation to return vegetation back to near reference condition followed by grazing management and prescribed fire to maintain the desired community.

State 3
Converted Land

Community 3.1
Converted Land

Figure 17. 3.1 Converted Land Community - Cropland

Figure 18. 3.1 Converted Land Community - Pastureland

Many acres have been converted to cropland and pastureland in the past. Historically, most were cut for timber, posts, poles, or firewood. Cropping small acreages is still practiced for grain, hay, or winter small grain, either for livestock grazing, grain harvesting, or planting for wildlife food plots. Irrigation is practiced where water is available.

Abandoned cropland areas, or cleared areas, are often seeded to introduced species, such as bermudagrass (Cynodon spp.) or Kleingrass (Panicum coloratum). 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 reference conditions if species such as big bluestem or switchgrass are seeded. The practice of including adapted legumes or other forbs will enhance productivity and usefulness, especially for wildlife. Irrigation will boost forage production where available.

Invasion of the seeded fields by brush species such as mesquite, pricklypear (Opuntia spp.), condalia (Condalia spp.), willow baccharis (Baccharis spp.), Texas persimmon and juniper are common. Drought and reduced soil cover due to cropping or grazing coupled with a nearby seed source trigger the invasions. The shrubs are 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. Many fields, however, have been abandoned and let go back to native range or planted to introduced grasses for pasture.

Community 3.2
Abandoned Land

Abandoned or go back land is a local name used to describe cropland fields that have been abandoned and are undergoing secondary succession. Many areas of Loamy Bottomland cleared of timber and cultivated by settlers in conjunction with the associated uplands. The abandoned cropland will be invaded by brush from the adjacent rangelands. The initial composition of abandoned fields are annual, biennial, and weak perennial grasses and forbs. The species depends on the seed source from adjacent rangeland or flood deposition. Willow baccharis, mesquite, Texas persimmon and juniper are common early invaders. The rate of succession depends on grazing management and drought frequency.

Without grazing management and brush management, brush species such as mesquite and juniper will dominate before a reference grass community can be established. Brush management and grazing management are required if the goal is restoration of the reference community. Annual production ranges from 1,500 to 3,500 pounds per acre. Without management inputs to control woody plants, most of the herbage produced in early stages of succession is from annual grasses and forbs, while in the latter stages of succession by woody invaders.

Pathway 3.1A
Community 3.1 to 3.2

Abusive grazing, no fires, no brush management, no pasture/cropland management, abandonment, and idled land are some contributing factors in the shift from the Converted Land Community to the Abandoned Land Community.

Pathway 3.2A
Community 3.2 to 3.1

Prescribed grazing, pasture planting, range planting, and crop cultivation conservation practices can help shift the Abandoned Land Community back to the Converted Land Community.

Transition T1A
State 1 to 2

Heavy abusive grazing, no brush management, and no fire have contributed to the shift from the Hardwood Grassland State to the Hardwood Woodland State.

Transition T1B
State 1 to 3

Brush management, pasture planting, range planting, and crop cultivation conservation practices can ease the transition from the Hardwood Grassland State to the Converted Land State.

Restoration pathway R2A
State 2 to 1

The Hardwood Woodland State can revert back to the Hardwood Grassland State through the application of brush management, prescribed grazing, IPT, range planting, and prescribed burning conservation practices.

Transition T2A
State 2 to 3

The Hardwood Woodland State can transition to the Converted Land State through the implementation of various conservation practices including brush management, pasture planting, range planting, and crop cultivation.