Loamy Bottomland 25-28" PZ
Scenario model
Current ecosystem state
Select a state
Management practices/drivers
Select a transition or restoration pathway
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Transition T1A
Absence of disturbance and natural regeneration over time, may be coupled with excessive grazing pressure
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Transition T1B
Extensive soil disturbance followed by seeding
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Restoration pathway R2A
Adequate rest from defoliation, followed by reintroduction of historic disturbance regimes
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Transition T2A
Absence of disturbance and natural regeneration over time, may be coupled with excessive grazing pressure
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Transition T2B
Extensive soil disturbance followed by seeding
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Restoration pathway R3A
Adequate rest from defoliation and removal of woody canopy
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Transition T3A
Extensive soil disturbance followed by seeding
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No transition or restoration pathway between the selected states has been described
Target ecosystem state
Select a state
State 1
Savanna State
Description
The reference plant community for the Loamy Bottomland ecological site is a tallgrass/hardwood savanna. The site is dominated by warm-season perennial tallgrasses such as switchgrass, Indiangrass, big bluestem, eastern gamagrass, and little bluestem. Warm-season midgrasses such as sideoats grama, vine mesquite, bristlegrass, purpletop, dropseeds, white tridens, and silver bluestem are also abundant. The Loamy Bottomland site historically has a significant amount of trees, shrubs, and vines. The shaded and moist environment enables cool-season and shade tolerant perennial grasses and grass-like plants to occupy the site.
Although the general plant type composition is similar to the original plant community, obvious shifts in plant species and structure of the Midgrass/Tallgrass Savanna Community begin to occur. As they begin to disappear, tallgrasses are replaced by a significant increase in warm-season perennial midgrasses, forbs, and annual grasses. Sideoats grama, vine mesquite, Texas wintergrass, and little bluestem begin to dominate the plant community. The diverse perennial forb community is replaced by a dramatic increase in ragweed and an invasion of sumpweed, broomweed, and other annual forbs. Woody species canopy of midstory shrubs and vines gradually begins to increase. Invasion of unwanted brush species such as mesquite from adjacent sites may begin to occur at this stage. As the woody canopy increases slightly, cool-season grasses and forbs and shade tolerant plants increase noticeably.
Submodel
State 2
Grassland/Woodland State
Description
The Midgrass/Tree-Shrub Community has crossed a threshold because there is no longer a sufficient seed source of the tallgrasses, and woody encroachment has reached a point that natural recovery to the reference plant community is no longer possible. Only remnant tallgrasses remain in isolated and protected areas. Midgrasses including Texas wintergrass, silver bluestem, and dropseeds dominate the site. Common bermudagrass may invade the site in open areas. Trees, shrubs, and vines increase in density and canopy. Mesquite, pricklypear, tasajillo, buttonbush, and a number of other shrubs invade the area from adjacent sites. In this phase, woody canopy is greater than 25% but less than 50%, allowing herbaceous plants to continue to produce fairly well and provide good ground cover.
Submodel
State 3
Woodland State
Description
The Tree-Shrub/Shade Tolerant Grass Community dominated by an overstory of hardwood trees including many species of elms, oaks, hackberry, and western soapberry. Vines such as greenbriar, grape, Virginia creeper, and ivy treebine increase significantly. Midstory shrubs including lotebush, bumelia, and sumacs begin to form dense thickets. Mesquite, juniper, pricklypear, and tasajillo become well established. Woody canopy is from 50% to 80% and warm-season perennial grasses begin to disappear from the site. Shade tolerant and cool season grasses and forbs become a major part of the plant community.
When the overstory and midstory canopy become greater than 80%, warm-season grasses and forbs exist only as remnants, generally consisting of widely scattered individual plants in low vigor. Shade tolerant forbs, grasses, and grass-like plants dominate the sparse understory vegetation. Some areas may have a dense mat of leaves and decomposing vegetation covering the soil surface.
Submodel
Description
In the past, thousands of acres of Loamy Bottomland were cleared, plowed and planted to annual crops such as cotton and corn. Row crops are still being planted on many of these cultivated acres. Some of the acres converted to cropland are planted to wheat and oats for grazing today.
In the more recent past, many acres that were once cultivated have been seeded or planted to introduced grasses. Additionally, thousands of bottomland acres have been cleared and converted from native rangeland to intensively managed pasturelands and haylands planted to monocultures of introduced species, primarily bermudagrass.
Abandoned croplands and reseeded areas tend to revert back to a more natural state through the process of secondary succession. This is a very slow process that takes decades or centuries dependent on the status of the area at the time it is abandoned. If managed properly, some of these abandoned areas may eventually begin to approximate the diversity and complexity of the native Loamy Bottomland ecosystem. However, it is highly unlikely that abandoned lands can ever return to reference vegetation within a reasonable period of time.
Submodel
Mechanism
Overstocking and heavy grazing pressure for an extended period of time in combination with lack of fire and lack of brush management will eventually result in a drastic change in the plant community on this site. The effect of these uncontrolled grazing practices and absence of needed treatments is that tallgrasses are almost completely eliminated from the site, except for a few widely scattered remnant plants in remote or protected areas. Tallgrasses become a minor component of the plant community and are no longer a viable population. Midgrasses become dominant as forbs, annuals, and shrub species begin to increase on the site. Woody canopy may increase to as much as 50% in this state. Cool-season and shade tolerant grasses, especially Texas wintergrass, increase as the woody canopy increases. Periodic flooding events can abruptly and drastically alter the plant community on this site as the natural vegetation is washed away or covered with silt, debris, or standing water for extended periods of time.
Mechanism
Conversion of this site from the reference plant community to cropland, introduced pasture, or seeded monoculture of native or introduced grasses will require seedbed preparation to destroy the existing herbaceous vegetation, followed by seeding or planting the desired crop or grass species.
Mechanism
A significant amount of energy and money are required in order for this plant community to be converted back to a more natural state. Brush management is needed in order to remove excessive midstory shrub growth and reduce the overhead canopy. The targeted species should be the invasive woody species as well as the overly aggressive and competitive native species that are not desired for wildlife habitat. Range planting is needed to re-establish a viable population of tallgrasses. These expensive treatments must be followed by establishment of a sound grazing management system to control the timing, frequency, and duration of livestock grazing to prevent the site from regressing back to a lower state. A strategically planned and implemented prescribed burning program is essential to maintaining the re-established plant community.
Relevant conservation practices
| Practice | External resources |
|---|---|
|
Brush Management |
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Prescribed Burning |
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Prescribed Grazing |
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Range Planting |
Mechanism
Abusive grazing is a result of severe overstocking and continuous heavy grazing pressure for several years. When grazing practices are abusive, periodic fire is eliminated from the site, and brush management is not carried out, the ultimate result will be a site that is dominated by trees and shrubs with extensive areas of bare ground. The combined overstory and midstory canopy of trees and shrubs may range from 50-80%. Higher successional warm-season midgrasses are replaced by lower successional midgrasses, shortgrasses, forbs, and shade tolerant grasses. Periodic flooding events can abruptly and drastically alter the plant community on this site as the natural vegetation is washed away or covered with silt, debris, or standing water.
Mechanism
Conversion of this site from the grassland/woodland state to cropland, introduced pasture, or seeded monoculture of native or introduced grasses will require brush management, seedbed preparation to destroy the existing herbaceous vegetation, followed by seeding or planting the desired crop or grass species.
Mechanism
Once the site has reached this phase, it is very difficult and expensive to try to convert this plant community back to the original tallgrass savanna plant community. Brush management treatments are needed to remove unwanted shrubs and trees, and reduce overhead canopy. These practices are difficult and expensive. Opening up the canopy will encourage re-establishment of higher successional warm-season midgrasses and tallgrasses if a viable seed source is still present. If livestock grazing is the objective, it will probably be necessary to follow the brush management treatments with range planting to re-establish a more diverse and productive herbaceous plant community. A sound grazing management system must then be implemented to control the timing, frequency, and duration of livestock grazing to prevent the site from regressing back to a lower state. A strategically planned and implemented prescribed burning program will be essential to maintaining the re-established plant community for wildlife or livestock objectives.
Relevant conservation practices
| Practice | External resources |
|---|---|
|
Brush Management |
|
|
Prescribed Burning |
|
|
Range Planting |
|
|
Prescribed Grazing |
Mechanism
Conversion of this site from the tree-shrub/cool-season grass state to cropland, introduced pasture, or seeded monoculture of native or introduced grasses, will require land clearing, seedbed preparation to destroy the existing herbaceous vegetation, followed by seeding or planting the desired crop or grass species.
Model keys
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The Ecosystem Dynamics Interpretive Tool is an information system framework developed by the USDA-ARS Jornada Experimental Range, USDA Natural Resources Conservation Service, and New Mexico State University.