Ecological dynamics
The Shallow Upland reference state consists of a pine forest, characterized by a shortleaf pine overstory with a herbaceous forest floor. Loblolly pine and hardwood tree species can also be found on upland sites (Edlredge, 1937). Native grass species such as big bluestem, switchgrass, little bluestem, and Indiangrass are found in the herbaceous layer. (Arkansas Geological Survey, 2005).
Fire has a significant influence on this ecological site. The historical average fire-return interval was likely between 3 and 25 years (Guyette and Spetich, 2003; Hallgren, DeSantic, and Burton, 2012). These wildfires would occur naturally through lightning strikes, but the majority were probably ignited by anthropogenic sources (DeSantis, Hallgren, and Stahle, 2010). Native species evolved with and responded well to fires (Spetich and Hong He, 2008; Engle and Bidwell, 2001). Fires on upland ecological sites are likely moderate to low severity, due to forested conditions and lower amounts of ground vegetation (Carey, 1992).
Climate related events, such as hail-storms, tornados, thunderstorms, and extreme precipitation, occur on these sites. Hail-storms can reduce canopy size, increase litter deposition, and increase tree bark removal. When paired with other disturbances, such as fire, the effects on tree species were much greater than in areas not affected by the hail-storm (Gower et al., 2015). Tornados have been shown to change plant community compositions in savanna ecosystems, favoring hardwoods and eliminating softwoods (Liu et al., 1997). Thunderstorms greatly effect ecosystem dynamics. Thunderstorms generally occur during summer months but can occur during every season. If a fire is started by a lightning strike, there will be different effects in the ecosystem depending on the season (Hiers, Wyatt, and Mitchell, 2000).
Livestock grazing can occur on this ecological site. Changes to the ecological dynamics are proportional to the intensity of livestock grazing and can be altered by grazing management practices (Angerer, Fox, and Wolfe, 2013; Kohl, 2016). For example, desirable grasses and forbs are relentlessly grazed by livestock. This will weaken and potentially remove or replace desirable species with less productive species (Smith, 1940).
A state and transition model has been created to explain this ecological site. However, sparse data availability only allowed basic principles to be explored and a small number of species to be recorded. More data will be collected to provide a greater understanding of the ecological dynamics, as well as the resources consumption and distribution.
State 1
Reference
The Reference State is representative of the natural range of variability without anthropogenic influences.
Drivers: Fire frequency between 3 and 25 years, climate (decadal scale), insect and disease presence or establishment, and wildlife grazing or browsing.
Feedbacks: Fire-tolerant species dominate the ecological site. Wildlife grazing or browsing decreases the amount of grass available, decreasing fire intensity and causing wildlife migration to a new grazing location. When wildlife migrate, grasses and small shrubs grow and become sufficient fuel to carry a low or medium intensity fire across the landscape within the fire return interval.
Characteristics and indicators. The reference state consists of a hardwood and pine forest, characterized by mixed hardwood and pine species. Gaps in the canopy allow sunlight to reach the herbaceous layer, allowing grass and forb species to grow.
Dominant plant species
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oak (Quercus), tree
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pine (Pinus), tree
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hybrid hickory (Carya), tree
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farkleberry (Vaccinium arboreum), shrub
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American beautyberry (Callicarpa americana), shrub
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bluestem (Andropogon), grass
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rosette grass (Dichanthelium), grass
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blueberry (Vaccinium), other herbaceous
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greenbrier (Smilax), other herbaceous
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eastern poison ivy (Toxicodendron radicans), other herbaceous
Community 1.1
Shortleaf Pine-White Oak/Bluestem
This community phase is dominated by mature pine and oak trees, along with warm-season, perennial tallgrasses.
Community 1.2
White Oak- Shortleaf Pine
This community phase has a moderately closed canopy with an understory of tallgrasses and midgrasses. This community phases occurs on drier locations than community phase 1.3.
Community 1.3
White Oak-Southern Red Oak- Shortleaf Pine
Tree species dominate this community phase. High foliar cover does not allow sunlight below the overstory. This community phase occurs on locations that receive and hold more moisture than community phase 1.2.
Community 1.4
Hickory- Elm- Red Maple
This community phase has fast growing trees and shrubs that cause a "crowded" appearance.
Pathway 1.1A
Community 1.1 to 1.2
Longer fire return intervals allow more trees to grow and become large. Large trees will remove resources from the herbaceous layer, reducing the amount of grasses and forbs.
Pathway 1.1B
Community 1.1 to 1.3
Longer fire return intervals allow more trees to grow and become large. Large trees will remove resources from the herbaceous layer, reducing the amount of grasses and forbs.
Pathway 1.1C
Community 1.1 to 1.4
Major disturbance removes overstory vegetation. Hickory and elm species cover empty space, and grow rapidly.
Pathway 1.2B
Community 1.2 to 1.4
Major disturbance removes overstory vegetation. Hickory and elm species cover empty space, and grow rapidly.
Pathway 1.3B
Community 1.3 to 1.4
Major disturbance removes overstory vegetation. Hickory and elm species cover empty space, and grow rapidly.
Pathway 1.4A
Community 1.4 to 1.1
Time passes and large trees eventually shade out and kill smaller trees in the understory.
Pathway 1.4B
Community 1.4 to 1.2
Time passes and large trees eventually shade out and kill smaller trees in the understory.
Pathway 1.4C
Community 1.4 to 1.3
Time passes and large trees eventually shade out and kill smaller trees in the understory.
State 2
Forest
The Forest State is representative of the natural range of variability with minor anthropogenic influences.
Drivers: Fire frequency between 3 and 25 years, climate (decadal scale), insect and disease presence or establishment, non-native vegetation establishment, and wildlife or livestock grazing or browsing.
Feedbacks: Fire-tolerant species dominate the ecological site. Grazing and browsing species decreases the amount of grass available, decreasing fire intensity. Grazing and browsing species are removed from the area allowing grasses and small shrubs grow and become sufficient fuel to carry a low or medium intensity fire across the landscape within the fire return interval. Prescribed fire is the most common cause of fire on the current landscape.
Characteristics and indicators. The forest state consists of a hardwood and pine forest, characterized by mixed hardwood and pine species. Gaps in the canopy allow sunlight to reach the herbaceous layer, allowing grass and forb species to grow. The forest state is different than the reference state because non-native vegetation is present.
Dominant plant species
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oak (Quercus), tree
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pine (Pinus), tree
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hybrid hickory (Carya), tree
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blueberry (Vaccinium), shrub
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greenbrier (Smilax), shrub
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muscadine (Vitis rotundifolia), shrub
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eastern poison ivy (Toxicodendron radicans), shrub
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farkleberry (Vaccinium arboreum), shrub
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blackberry (Rubus), shrub
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bluestem (Andropogon), grass
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rosette grass (Dichanthelium), grass
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longleaf woodoats (Chasmanthium sessiliflorum), grass
Community 2.1
Shortleaf Pine-White Oak/Bluestem
This community phase is dominated by mature pine and oak trees, along with warm-season, perennial tallgrasses.
Community 2.2
White Oak- Shortleaf Pine
This community phase has a moderately closed canopy with an understory of tallgrasses and midgrasses. This community phases occurs on drier locations than community phase 1.3.
Community 2.3
White Oak-Southern Red Oak- Shortleaf Pine
Tree species dominate this community phase. High foliar cover does not allow sunlight below the overstory. This community phase occurs on locations that receive and hold more moisture than community phase 1.2.
Community 2.4
Hickory- Elm- Red Maple
This community phase has fast growing trees and shrubs that cause a "crowded" appearance.
Pathway 1.1A
Community 2.1 to 2.2
Longer fire return intervals allow more trees to grow and become large. Large trees will remove resources from the herbaceous layer, reducing the amount of grasses and forbs.
Pathway 1.1B
Community 2.1 to 2.3
Longer fire return intervals allow more trees to grow and become large. Large trees will remove resources from the herbaceous layer, reducing the amount of grasses and forbs.
Pathway 1.1C
Community 2.1 to 2.4
Major disturbance removes overstory vegetation. Pioneer tree species cover empty space and grow rapidly.
Pathway 1.2B
Community 2.2 to 2.4
Major disturbance removes overstory vegetation. Pioneer tree species cover empty space and grow rapidly.
Pathway 1.3B
Community 2.3 to 2.4
Major disturbance removes overstory vegetation. Pioneer tree species cover empty space and grow rapidly.
Pathway 1.4A
Community 2.4 to 2.1
Time passes and large trees eventually shade out and kill smaller trees in the understory.
Pathway 1.4B
Community 2.4 to 2.2
Time passes and large trees eventually shade out and kill smaller trees in the understory.
Pathway 1.4C
Community 2.4 to 2.3
Time passes and large trees eventually shade out and kill smaller trees in the understory.
State 3
Pasture
The Pasture State is characterized by the dominance of improved forage species. The quality and quantity of forb, grass, and legume species within this state will depend on the level of management inputs including seeding, fertilization, herbicide application, livestock management, and land uses. Species of both warm-season and cool-season grasses are feasible for these sites.
Drivers: Mechanical soil disturbance and seed planting, climate (decadal scale), seed dispersal, and wildlife or livestock grazing or browsing.
Feedbacks: Land managers use mechanical and chemical equipment to increase forage. Inputs of fertilizer and brush management are required to maintain high productivity. Wildlife and livestock grazing and browsing decrease the amount of available forage.
Characteristics and indicators. The Pasture State consists of species that are grown for specific management goals, mainly livestock grazing. Common pasture species include bermudagrass, bahiagrass, dallas grass, little bluestem, broom sedge bluestem, annual ryegrass, and tall fescue. Quality and quantity of forb, grass, and legume species within this state depend on the level of management inputs (seeding, weed management, and land uses). Species of both warm-season and cool-season grasses are feasible for these sites.
Dominant resource concerns
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Sheet and rill erosion
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Wind erosion
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Ephemeral gully erosion
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Classic gully erosion
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Bank erosion from streams, shorelines, or water conveyance channels
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Compaction
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Organic matter depletion
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Nutrients transported to surface water
Community 3.1
Bermudagrass
Herbaceous species have been planted to maximize forage production for grazing livestock.
Community 3.2
Bermudagrass/ Elm- Eastern Redcedar
Herbaceous species have been planted to maximize forage production for grazing livestock. Management decisions allow the growth of woody species, such as elm and eastern redcedar.
Community 3.3
Eastern Redcedar- Elm/ Bermudagrass
Herbaceous species have been planted to maximize forage production for grazing livestock. Improper pasture management and time have allowed for the growth of woody species such as eastern redcedar, oaks, and American elm. Woody species encroach on the pasture and dominate resources that were previously utilized by forage species.
Pathway 3.1A
Community 3.1 to 3.2
This pathway consists of an absence of fire, intense grazing pressure, and natural regeneration.
Pathway 3.2A
Community 3.2 to 3.1
This pathway consists of the removal or reduction of woody species and the increase of desirable forage species.
Pathway 3.2B
Community 3.2 to 3.3
This pathway consists of an absence of fire, intense grazing pressure, and natural regeneration.
Pathway 3.3A
Community 3.3 to 3.1
This pathway consists of the removal or reduction of woody species.
Pathway 3.3B
Community 3.3 to 3.2
This pathway consists of the removal or reduction of woody species.
State 4
Timber Plantation
The timber plantation state is characterized by the planting of merchantable trees species. The most common species for plantations in the Ouachita Mountains is loblolly pine.
Drivers: Pest management, vegetation management, canopy density.
Feedbacks: Timber harvesting. Planted tree species dominate this ecological site, shading out other vegetation. Anthropogenic management decreases competition with other species and assists in growth.
Characteristics and indicators. The timber plantation state consists of tree species that are planted and managed to maximize the production of merchantable timber. The most common plantation species is loblolly pine, followed by hardwood trees. Timber management differs by tree type (softwood or hardwood), timber harvest method, and reforesting practices.
Dominant resource concerns
Community 4.1
Loblolly Pine
Loblolly pine is planted to maximize timber production.
Dominant plant species
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loblolly pine (Pinus taeda), tree
Transition T1B
State 1 to 3
Trigger: Mechanical and chemical woody vegetation suppression, tillage, seeding, and annual forage species introduction.
Slow Variables: Increase production and management of forage species.
Thresholds: Changes in soil properties, such as structure, organic matter, and nutrient cycling, as well as changes in type and frequency of disturbance.
| Brush Management |
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| Prescribed Burning |
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| Land Clearing |
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| Prescribed Grazing |
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Transition T1A
State 1 to 4
Trigger: Native tree removal, mechanical and chemical woody vegetation suppression, introduce plantation tree species.
Slow Variables: Increased production and management of plantation species.
Thresholds: Changes in soil properties such as structure, organic matter, and nutrient cycling as well as changes in type and frequency of disturbance.
Transition T2B
State 2 to 3
Trigger: Mechanical and chemical woody vegetation suppression, tillage, seeding, and annual forage species introduction.
Slow Variables: Increase production and management of forage species.
Thresholds: Changes in soil properties, such as structure, organic matter, and nutrient cycling, as well as changes in type and frequency of disturbance.
Transition T2A
State 2 to 4
Trigger: Native tree removal, mechanical and chemical woody vegetation suppression, introduce plantation tree species.
Slow Variables: Increased production and management of plantation species.
Thresholds: Changes in soil properties such as structure, organic matter, and nutrient cycling as well as changes in type and frequency of disturbance.
Transition T3B
State 3 to 2
Trigger: Forage species removal and suppression, mechanical and chemical woody vegetation suppression, introduce and manage native tree species.
Slow Variables: Increased production and management of native species.
Thresholds: Changes in soil properties such as structure, organic matter, and nutrient cycling as well as changes in kind and frequency of disturbance.
Transition T3A
State 3 to 4
Trigger: Forage species removal and suppression, mechanical and chemical woody vegetation suppression, introduce and manage plantation tree species.
Slow Variables: Increased production and management of plantation species.
Thresholds: Changes in soil properties such as structure, organic matter, and nutrient cycling as well as changes in kind and frequency of disturbance.
Transition T4A
State 4 to 2
Trigger: Timber species removal and suppression, mechanical and chemical woody vegetation suppression, introduce and manage native tree species.
Slow Variables: Increased production and management of native species.
Thresholds: Changes in soil properties such as structure, organic matter, and nutrient cycling as well as changes in kind and frequency of disturbance.
Transition T4B
State 4 to 3
Trigger: Tree removal, mechanical and chemical woody vegetation suppression, tillage, seeding, and introduce annual or perennial forage species.
Slow Variables: Increase production and management of forage species.
Thresholds: Changes in soil properties such as structure, organic matter, and nutrient cycling as well as changes in type and frequency of disturbance.