Sandy Hillslope
Scenario model
Current ecosystem state
Select a state
Management practices/drivers
Select a transition or restoration pathway
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Transition T1A
Fire suppression, overgrazing, increased precipitation, and shading.
More details -
Transition T1B
Tree removal, brush management, forage seed establishment and management.
More details -
Restoration pathway R2A
Tree thinning, brush management, prescribed fire, and grazing.
More details -
Transition T2A
Woody species removal, prescribed fire, and grazing.
More details -
Transition T3A
Abusive agricultural practices, drought.
More details -
Restoration pathway R4A
Establish ground cover.
More details -
No transition or restoration pathway between the selected states has been described
Target ecosystem state
Select a state
Description
The reference state is considered to be representative of the natural range of variability without major anthropogenic influences. This state is characterized by a warm-season, perennial, tallgrass savanna with scattered oak trees. Total overstory canopy cover is less than 25 percent.
Drivers- Fire frequency between 1 and 10 years (Hallgren, 2011), climate (decadal scale), insect and disease presence or establishment (oak wilt, beetles), and wildlife grazing or browsing.
Feedbacks- Fire tolerant grasses dominate the ecological site, fire intervals suppress woody vegetation growth. Wildlife grazing/browsing decreases the amount of grass available, decreasing fire intensity and causing wildlife migration to a new grazing location.
Characteristics and indicators
The reference state is characterized by a savanna, an open grassland with trees and shrubs present in low numbers. The trees species for this state are mainly post oak, blackjack oak, black hickory, bitternut hickory, chinquapin oak, cedar elm, and other oak species. Dominate grasses consist of little bluestem, switchgrass, indiangrass, and big bluestem (Landfire 2010; NatureServe 2009).
Submodel
Description
The encroached state is dominated by tree species. Canopy cover is greater than 25%.
Driver- Absence of wildfire, seed dispersal by wildlife, climate (decadal scale), and canopy density.
Feedbacks- Tree species dominate the ecological site, causing shading of grass species and shorter woody species. Less ground cover will decrease fire risk. Nutrient and water cycling will be controlled by tree species.
Characteristics and indicators
The encroached state consists of many tree species, especially eastern redcedar, where there is significant canopy closure. Depending on how long this state has been present on the ecological site, the plant community will vary from oak, to hickory, to eastern redcedar. As the woody canopy increases and an encroached state occurs, the hydrology of the site is altered. The increased canopy intercepts most of the precipitation and changes hydrological patterns to favor tree species over grass species. Understory species will generally have less available water for growth and will have to compete with an extensive redcedar root system (Zou, 2018).
Submodel
Description
The pasture state consists of introduced grass species that are planted to maximize livestock forage production.
Drivers- Mechanical soil disturbance and seed planting, climate (decadal scale), seed dispersal, and wildlife/livestock grazing or browsing.
Feedbacks- Land managers use mechanical or chemical equipment to manipulate the ecological site. Wildlife and livestock grazing/browsing decrease the amount of available forage. Inputs of fertilizer and brush management are required to maintain high productivity across this ecological state.
Characteristics and indicators
The pasture state will comprise species that are planted and grown for specific management goals, mainly livestock grazing. Common pasture species include buffalograss, western wheatgrass, little bluestem, sideoats grama, composite dropseed, silver beardgrass, winter bentgrass, purple lovegrass, kentucky bluegrass, tumblegrass, fall panicgrass, little barley, white sagebrush, slimflower scurfpea, and missouri goldenrod. Quality and quantity of forb, grass and legume species within this state will depend on the level of management inputs including seeding, weed management, and land uses. Species of both warm-season and cool-season grasses are feasible for these sites.
Submodel
Description
The eroded state consists of an area where the soil and plant communities are not stable due to wind and water erosion.
Drivers- Loss of soil and site stability, active soil erosion, climate (decadal scale), and wildlife/livestock grazing or browsing.
Feedbacks- Reduced basal cover and increased bare ground resulting in increased overland flow leading to rills and gullies.
Characteristics and indicators
The eroded state consists of an area where the soil and plant communities are not stable due to wind and water erosion. In addition to destroying the original plant community, over plowing (degrading soil through cultivation) has resulted in major soil condition changes. Reductions in organic matter, mineral levels, soil structure, oxygen levels, water holding capacity, and populations of soil dwelling organisms are common in this state. The extent of these changes depend upon duration of over plowing, as well as the species of crops grown and other management practices. Where vegetation is able to grow, this states plant community is predominately prairie threeawn interspersed in remnants of perennial grasses such as alkali sacaton, blue grama, sideoats grama and buffalograss. Numerous annuals are usually found on this state.
Submodel
Mechanism
Trigger- Fire suppression, overgrazing (when the consumption of vegetation biomass by livestock and other grazers exceeds the vegetations ability to recover in a timely fashion, thus exposing the soil and reducing the vegetations productive capacity (Angerer, 2013)), shading, and increased woody species seedling success.
Slow Variables: Increasing amounts of shade (reducing ground cover species), decreasing amounts of native grass species (both annual and perennial) changing nutrient cycles from grass dominated to leaf dominated, and increased woody vegetation changes hydrology and precipitation through percolation and transpiration.
Thresholds: Canopy cover becoming greater than 25%.
Mechanism
Trigger- Mechanical tree removal, mechanical and chemical woody vegetation suppression (removing brush by use of mechanical cutter, chopper, or other equipment followed by an application of chemicals in order to reduce fuel loading and improve ecological site condition, (NRCS 314)), introducing annual/ perennial grass and forb species, prescribed fire (applying controlled fire to a predetermined area of land, (NRCS 338)), and prescribed grazing ( managing the harvest of vegetation with grazing and-or browsing animals, (NRCS 528)).
Slow Variables: Increased production and management of introduced species.
Thresholds: Native seed sources are removed and suppressed from the ecological site.
Relevant conservation practices
| Practice | External resources |
|---|---|
|
Brush Management |
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Prescribed Burning |
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Land Clearing |
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Prescribed Grazing |
Mechanism
Trigger- Mechanical tree removal, mechanical and chemical woody vegetation suppression (removing brush by use of mechanical cutter, chopper, or other equipment followed by an application of chemicals to reduce fuel loading and improve ecological site condition, (NRCS 314)), and prescribed fire that will kill trees and suppress woody vegetative growth (applying controlled fire to a predetermined area of land, (NRCS 338)).
Slow Variables: Removal of tree species decreases the amount of shade, allowing grass species to receive nutrients. Nutrient and water cycles shift from complete tree domination to a combination of tree and grass dominated.
Thresholds: Canopy cover becomes less than 25%.
Relevant conservation practices
| Practice | External resources |
|---|---|
|
Brush Management |
|
|
Prescribed Burning |
Mechanism
Trigger- Mechanical tree removal, mechanical and chemical woody vegetation suppression (removing brush by use of mechanical cutter, chopper, or other equipment followed by an application of chemicals to reduce fuel loading and improve ecological site condition, (NRCS 314)), prescribed fire that will suppress woody vegetative growth (applying controlled fire to a predetermined area of land, (NRCS 338)), prescribed grazing ( managing the harvest of vegetation with grazing and-or browsing animals, (NRCS 528)), and introduced species planting/establishment.
Slow Variables: Removal of tree species decreases the amount of shade, allowing grass species to receive nutrients. Nutrient and water cycles shift from complete tree domination to a combination of tree and grass dominated. Introduced species are established.
Thresholds: Introduced species become a significant environmental factor at the ecological site.
Relevant conservation practices
| Practice | External resources |
|---|---|
|
Brush Management |
|
|
Prescribed Burning |
|
|
Land Clearing |
|
|
Prescribed Grazing |
Mechanism
Trigger- Drought, over-plowing (degrading soil through cultivation), and overgrazing (when the consumption of vegetation biomass by livestock and other grazers exceeds the vegetations ability to recover in a timely fashion, thus exposing the soil and reducing the vegetations productive capacity (Angerer, 2013)).
Slow Variables: Vegetation quantity and quality will decrease over time. Ground cover will decrease, increasing water and wind erosion. New vegetation will quickly be consumed by livestock/wildlife when it becomes available.
Thresholds: Significantly reduced ground cover, increasing water and wind erosion.
Feedbacks- Any vegetation that is grown will quickly be consumed by livestock, destabilizing the soil and continuing erosion.
Mechanism
Stop practices that are causing harm such as overgrazing (when the consumption of vegetation biomass by livestock and other grazers exceeds the vegetations ability to recover in a timely fashion, thus exposing the soil and reducing the vegetations productive capacity (Angerer, 2013)), over-plowing (degrading soil through cultivation), and other unsustainable agricultural practices. Establish ground cover, preferably using non-invasive species. Following ground cover establishment, plant species that will increase site stabilization. Manage for desirable site conditions.
Model keys
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Ecological sites
Major Land Resource Areas
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.