State 1
Grassland State

Community 1.1
Tallgrass Community

Figure 9. Community Phase 1.1

This is the reference or diagnostic community for the site. The description is based on early range site descriptions, clipping data, professional consensus of experienced range specialists, and analysis of field work.

The Tallgrass Community (1.1) is the interpretive plant community for the Sandy Bottomland Ecological Site. The Tallgrass Community evolved under the influence of periodic flooding, grazing, periodic fire and a dry sub-humid climate. Occasional flooding and a fluctuating water table influenced the plant community. Woody plants, primarily cottonwood, hackberry, pecan and American elm were widely scattered along the stream edges and draws. Shrubs and vines such as bumelia, plum, prickly ash, greenbriar, skunkbush sumac, elbowbush, baccharis, Carolina snailseed and grape were present but kept suppressed by climatic conditions, periodic fires and grass competition. The herbaceous component accounted for up to 90 percent of the site’s primary annual production, with tall grasses such as switchgrass, Indiangrass, big sandreed, big/sand bluestem, eastern gamagrass and little bluestem accounting for 60 to 70 percent of the herbage production. Secondary grasses were purpletop tridens, sand lovegrass, Texas cupgrass, vine mesquite, Arizona cottontop, plains bristlegrass, sideoats grama and dropseed. Canada and Virginia wildrye, Texas wintergrass and western wheatgrass were common cool-season grasses. Common forbs included Maximilian sunflower, Illinois bundleflower, catclaw sensitivebriar, heath aster, gaura, lespedeza, tickclover, mentzelia, and bush morning glory. (See Plant Community Composition and Annual Production table below).

The Tallgrass Community (1.1) was productive due to good soil and water relationships, although soil fertility is low. Herbage production ranged from 2,500 to 6,500 pounds per acre per year. Soil erosion was low due to the abundant plant cover, litter, and slow runoff. Runoff from the was reduced due to the dense tallgrass cover. The tallgrass ground cover helped disperse and slow down runoff thus holding soil in place and enhancing infiltration into the rapidly permeable soils. Concentrated water flow patterns were probably rare.

Generally, the Sandy Bottomland is a preferred habitat for both livestock and wildlife so most areas of this site have received overgrazing by livestock and wildlife and have regressed to a lesser plant community type. Without proper livestock grazing management that adjusts animal numbers to annual forage production and judicious prescribed burning, the Tallgrass Community (1.1) will transition (regress) to a Tallgrass/Midgrass Community (1.2).

Community 1.2
Tallgrass/Midgrass Community

The Tall/Midgrass Community (1.2) reflects the results of the suppression of fires and the effects of overgrazing on the more palatable species. An occasional severe flooding event may also cause damage to the grassland. Indigenous and invading woody plants have increased in density and stature. Mesquite, western soapberry, salt cedar and baccharis are the more common woody invaders. Little bluestem, sideoats grama, vine mesquite, are generally persistent in this phase, but most of the more palatable tall and midgrasses are being replaced by subdominants such as tall dropseed, purpletop tridens, sand lovegrass, knotroot bristlegrass, Texas wintergrass and less palatable forbs and annuals. Western ragweed, heath aster, mentzelia and Louisiana sagewort are common forbs. Common bermudagrass often invades the sandy areas near the stream edge. 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 2,000 to 6,000 pounds with approximately 80 percent being produced by the grassland component. Nutrient cycling and water use is shifting toward the deeper-rooted woody perennials. Soil organic matter, litter and ground cover are slightly less than were present in the reference community.

In the Tall/Midgrass Community (1.2) ecological processes have changed little and the pathway back to the HCPC can be accomplished without major energy inputs. Good grazing management alone will not reverse the trend towards the woodland state, however. Some form of woody plant control, such as prescribed burning and selective, mechanical brush control must accompany it.

The transition of the Tall/Midgrass Community (1.2) toward a woodland state is reversible with prescribed grazing management and prescribed burning practices until the woody canopy exceeds 15 to 20 percent. Once woody plant canopy exceeds 20 percent, the plant community crosses a threshold to a shrub influenced woodland state represented by a Mixed-grass/Mixed-brush Community (2.1). Once the threshold into a woodland state is crossed, the transition is irreversible without considerable energy input in the form of mechanical or chemical brush control.

Pathway 1.1A
Community 1.1 to 1.2

Without proper livestock grazing management that adjusts animal numbers to annual forage production and judicious prescribed burning, the Tallgrass Community (HCPC) will transition (regress) to a Tallgrass/Midgrass Community (1.2).

Pathway 1.2A
Community 1.2 to 1.1

With the implementation of various conservation practices such as Prescribed Grazing and Prescribed Burning, the shift from the Tall/Midgrass Community to the Tallgrass Community may be possible.

State 2
Woodland State

The Mixed-grass/Mixed-brush Community (2.1) supports a 20 to 35 percent woody plant cover dominated by various bottomland hardwoods, although their numbers are often diminished. Mixed-brush areas form within the grassland particularly on recent sand deposits. Grassland vegetation still dominates herbage production. Midgrasses, shortgrasses and a variety of forbs dominate the herbaceous layer. All, but the more palatable woody species, have increased in size and density. The typical woody plant cover is dominated by mesquite, willow baccharis, salt cedar, ephedra and greenbriar. Pecan, cottonwood, western soapberry, hackberry and elm persist near the stream edge. Little bluestem often remains the dominant grass, but as regression progresses under heavy grazing pressure, it gives way to sand dropseed, silver bluestem, red lovegrass, and other less palatable shortgrasses and forbs. Alkali sacaton is abundant where saline soil conditions occur. Salt cedar may also invade these areas. Eastern redcedar is a common invader in the northern portion of this site. Annual herbage production ranges from 1,800 to 5,800 pounds per acre.

The Mixed-brush/Mixed-grass/Annuals Community (2.2) is composed of brush species including cottonwood, pecan, hackberry and western soapberry. Mesquite, willow baccharis and salt cedar have increased tremendously in the past few decades. The shrubs often form dense thickets where grazing has been heavy and continuous and fires have been excluded. Salt cedar and baccharis are particularly problematic where salinity has increased. Common understory shrubs are elbowbush, bumelia, plum and pricklyash. Midgrasses, shortgrasses, cool-season grasses and low quality annual and perennial forbs occupy the tree interspaces. Alkali sacaton, inland saltgrass and seep muhly become the primary grasses in deteriorated salty areas. The woody overstory can reach 75 percent ground cover with less than 25 percent of the herbage being produced by the grassland component.

Community 2.1
Mixed-grass/Mixed-brush Community

The Mixed-grass/Mixed-brush Community (2.1) supports a 20 to 35 percent woody plant cover dominated by various bottomland hardwoods, although their numbers are often diminished. Mixed-brush areas form within the grassland particularly on recent sand deposits. Grassland vegetation still dominates herbage production. Midgrasses, shortgrasses and a variety of forbs dominate the herbaceous layer. This community is the result of selective grazing by livestock, suppression of fire and the differential response of plants to defoliation. The diversity of the grassland component declines while unpalatable woody plants and forbs increase. All, but the more palatable woody species, have increased in size and density. The typical woody plant cover is dominated by mesquite, willow baccharis, salt cedar, ephedra and greenbriar. Pecan, cottonwood, western soapberry, hackberry and elm persist near the stream edge. Little bluestem often remains the dominant grass, but as regression progresses under heavy grazing pressure, it gives way to sand dropseed, silver bluestem, red lovegrass, and other less palatable shortgrasses and forbs. Gaura, western ragweed, verbena, thread leaf groundsel, heath aster, bush morning glory, Mexican sagewort, mentzelia and tickclover are commonly found in this community. Cool-season grasses, such as Texas wintergrass and Texas bluegrass are persistent under and around woody plants where shading occurs. Alkali sacaton is abundant where saline soil conditions occur. Salt cedar may also invade these areas. Eastern redcedar is a common invader in the northern portion of this site.

Annual herbage production ranges from 1,800 to 5,800 pounds per acre, depending on precipitation events, flooding events and dry cycles. Annual herbage production is less than in the Mixed-grass/Mixed-brush Community (1.2) due to decline in soil structure and organic matter. Herbage production is balanced between the grassland component and woody species.

As the grassland component declines, more soil is exposed to erosion. During the middle and end of this plant community phase, considerable soil becomes exposed. Water erosion is not a serious problem because of shallow slopes on the site. Higher interception loss of water by the increasing woody canopy combined with evaporation losses reduces the effectiveness of rainfall. Litter, soil organic matter and structure decline in the interspaces, but hydrologic conditions improve under the woody plant cover.

When the woody plant cover reaches 35 to 40 percent and the herbaceous component contributes less than 50 percent of the herbage production, the Mixed-grass/Mixed-brush Community (2.1) transitions into a Mixed-brush/Mixed-grass/Annuals Community (2.2). Prior to reaching this threshold, the Mixed-brush/Mixed-grass Community can be converted to a grassland state with judicious use of broadcast or individual brush control, prescribed burning and prescribed grazing.

Community 2.2
Mixed-brush/Mixed-grass/Annuals Community

The Mixed-brush/Mixed-grass/Annuals Community (2.2) is the result of long-term continued overgrazing by livestock and no control of woody species. Several woody species may dominate the site. Cottonwood, pecan, hackberry and western soapberry were the early dominants. Mesquite, willow baccharis and salt cedar have increased tremendously in the past few decades. The shrubs often form dense thickets where grazing has been heavy and continuous and fires have been excluded. Salt cedar and baccharis are particularly problematic where salinity has increased. Common understory shrubs are elbowbush, bumelia, plum and pricklyash. Midgrasses, shortgrasses, cool-season grasses and low quality annual and perennial forbs occupy the tree interspaces. Characteristic grasses found in this plant community are Texas wintergrass, threeawns, sand dropseed, giant dropseed, big sandreed, annual panicum, silver bluestem and sedges. Representative forbs include heath aster, western ragweed, mentzelia, Mexican sagewort, annual broomweed and verbena. Texas wintergrass persists where mesquite is dominant and can become abundant following above normal rainfall. Alkali sacaton, inland saltgrass and seep muhly become the primary grasses in deteriorated salty areas.

The woody species will continue to thicken until the community stabilizes with the climate and soil. The woody overstory can reach 75 percent ground cover with less than 25 percent of the herbage being produced by the grassland component. An understory of eastern redcedar can develop in the northern portion of this site, especially if fire is not used. The mature phase of the Mixed-brush/Mixed-grass/Annuals Community provides cover for wildlife, but only limited amounts of preferred forage or browse is available for livestock or wildlife.

Returning the Mixed-brush/Mixed-grass/Annuals Community (2.2) back to a grassland state requires extensive and expensive reclamation practices. Range planting, prescribed grazing and prescribed burning, must follow intensive mechanical brush control. Land use other than livestock production might dictate alternative reclamation approaches to create the plant community that best fits the intended use.

Pathway 2.1A
Community 2.1 to 2.2

With heavy continuous grazing, no fires, and no brush management, the Mixed-grass/Mixed-brush Community will shift to the Mixed-brush/Mixed-grass/Annuals Community.

Pathway 2.2A
Community 2.2 to 2.1

With Brush Management and Prescribed Grazing conservation practices, the Mixed-brush/Mixed-grass/Annuals Community can be shifted to the Mixed-grass/Mixed-brush Community.

State 3
Converted Land State

This site, due to flooding and sandy soil is not recommended for cultivation. However, some sites in the past were farmed and planted to crops or planted to permanent pasture. Some are maintained in orchards. The permanent pasture could include bermudagrass, old world bluestems or other perennial plants.

Even though a Sandy Bottomland site may have been cultivated for a substantial period of time, the site can return to something resembling the reference state. The return of a cultivated field to the reference state depends on the soil integrity. Many things affect soil integrity, such as the amount of A horizon remaining, erosion, loss of organic matter, soil type, and others. There are many examples of idled cultivated fields that closely resemble the reference state. Remnant terraces usually reveal the fact that the fields were cultivated at some time in the past although terraces are not as common on bottomlands. It is sometimes difficult to determine if fields were cultivated others were not if successfully reseeded. The most obvious clue is the lack of native forb diversity.

If the cultivated land is abandoned, woody plants and early successional herbaceous herbaceous plants will establish. Without brush management, prescribed grazing or prescribed fires, the plant community will revert back to the Mixed brush/Mixed grass/Annuals Community (2.2)

Annual Production by Plant Type Table:
The plant production in the Converted Land is highly variable. If planted to permanent pasture and not fertilized, production will resemble the reference state. If fertilized, the plant community will produce more than the reference state depending upon level of fertility and rainfall. Total production and composition of an abandon land is very difficult to predict and should be determined on-site.

Transition T1A
State 1 to 2

The Grassland State will transition into the Woodland State with the presence of heavy continuous grazing, no brush management, and no fires.

Transition T1B
State 1 to 3

The Grassland State will transition into the Converted Land State with the use of Crop Cultivation, Plowing, Range Planting, Pasture Planting, Pest Management, Nutrient Management, and Brush Management.

Transition T1B
State 1 to 3

The Grassland State will transition into the Converted Land State with the use of Crop Cultivation, Plowing, Range Planting, Pasture Planting, Pest Management, Nutrient Management, and Brush Management.

Restoration pathway R2A
State 2 to 1

Returning the Woodland State back to a Grassland State requires extensive and expensive reclamation practices. Range planting, prescribed grazing and prescribed burning, must follow intensive mechanical brush control.

Transition T2A
State 2 to 3

The Shrubland State will transition into the Converted Land State with the use of Crop Cultivation, Plowing, Range Planting, Pasture Planting, Pest Management, Nutrient Management, and Brush Management.

Transition T3B
State 3 to 2

Without brush management, prescribed grazing or prescribed fires, along with the invasion of brush species and abandonment, the Converted Land State will revert back to the Woodland State.