Isohyperthermic Udic Naturalized Grassland (Guineagrass / Desmodium)
Scenario model
Current ecosystem state
Select a state
Management practices/drivers
Select a transition or restoration pathway
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Transition T1A
State 1 Reference transitions to State 5 Weed Invaded Grassland by long-term continuous grazing and lack of weed control measures. Remnant desirable forages have been grazed out and replaced entirely by weedy grasses, forbs, shrubs, and small trees.
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Restoration pathway R2B
State 2 Invaded Understory can be restored to State 1 Reference by clearing the forest with heavy machinery. Seed or plant desired perennial grasses as needed. Once cleared it is likely that weed species released from the soil seed bank will require invasive plant species control measures.
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Transition T2A
State 2 Invaded Understory transitions to State 3 Invaded Over and Understory through the process of fast-growing weeds inhibiting reproduction of native plants and gradually replacing them. This process is accelerated by feral pigs and cattle directly damaging native plants and promoting the spread of weeds by disturbing the soil and spreading weed seeds.
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Restoration pathway R2A
State 2 Invaded Understory may be restored to a facsimile of State 4 Native Forest. Exclusion of all ungulates is required; in many cases construction of a suitable fence will be necessary. Intensive weed control must then be initiated and maintained in the long term. In some cases, large amounts of dead weed biomass must be dealt with by removal or decomposition. Reintroduction of missing native species will be necessary.
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Restoration pathway R3A
State 3 Invaded Over and Understory can be converted to State 1 Reference by clearing vegetation using heavy machinery, applying aggressive weed control measures, and planting desirable forage species as needed.
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Transition T4B
State 4 Native Forest can transition to State 1 Reference by clearing the forest with heavy machinery and planting desirable pasture species as needed. Native forest may be cleared gradually by allowing cattle access to the forest. Cattle eventually eat or destroy understory ferns, forbs, shrubs, and saplings, opening the forest so that introduced grasses will thrive.
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Transition T4A
State 4 Native Forest transitions to State 2 Invaded Understory by the very aggressive, introduced weed species present in this ecological site invading intact native forest and gradually replacing native species in the understory. This invasion is greatly facilitated by feral pigs and cattle that damage and consume native plants, disturb the soil, and spread weed seeds.
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Restoration pathway R5A
State 5 Weed Invaded Grassland can be restored to State 1 Reference by brush management, re-establishment of desirable forage species, persistent weed control, and prescribed grazing.
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Restoration pathway T5A
State 5 Weed Invaded Grassland transitions to State 3 Invaded Over and Understory due to the presence of fast-growing, introduced tree species; wildfire may prevent this from occurring.
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No transition or restoration pathway between the selected states has been described
Target ecosystem state
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State 1
Reference State
Description
This state consists of two community phases dominated by introduced grass species. This state is considered to be the Reference State because no intact examples of native forest remain, and the species compositions of the forests consisting of introduced species are extremely variable.
Continuous grazing results in increased abundance of less desirable forage species, as represented by the phase change from 1.1 Guineagrass /desmodium to 1.2 Hilograss – broomsedge bluestem/shameplant. Longer-term overgrazing and lack of weed control measures results in a transition to State 5 Weed-Invaded Grassland.
Submodel
Description
This state consists of one community phase. Native ohia lehua and pandanus trees may be present in some locations. However, introduced trees, shrubs, vines, and ferns produce a dense layer of low, competitive vegetation that severely inhibits reproduction of native species. Activity of feral pigs and cattle further reduces native plant abundance and produces bare, disturbed soil patches that promote weed invasion. Eventually, this state transitions to State 3 Invaded Overstory and Understory through growth of introduced tree species.
Submodel
Description
This state consists of one community phase dominated by introduced species in both the overstory and understory. Some individual native trees may persist for their lifetime. The diversity of weedy trees, shrubs, vines, ferns, and herbs is high, and the species mix is variable. Conversion to State 1 Reference is possible by using heavy machinery and applying aggressive weed control and ungulate-exclusion measures.
Submodel
Description
This state consists of one community phase. Because no intact examples of this state remain, the following description is hypothetical, based on observations of similar ecological sites and on the known ranges and environmental preferences of likely native plant species.
When cleared by machinery, fire, or long-term, heavy ungulate browsing, this state transitions to State 1 Reference. Gradual invasion by weedy, introduced plant species brings a transition to State 2 Invaded Understory.
Submodel
Description
This state consists of one community phase consisting primarily of weedy shrubs and small trees. Weedy grasses and forbs dominate between shrub patches. Introduced tree species are present and will attain dominance if fire does not set them back.
Submodel
Mechanism
State 1 Reference transitions to State 5 Weed Invaded Grassland by long-term continuous grazing and lack of weed control measures. Remnant desirable forages have been grazed out and replaced entirely by weedy grasses, forbs, shrubs, and small trees.
Mechanism
State 2 Invaded Understory can be restored to State 1 Reference by clearing the forest with heavy machinery. Seed or plant desired perennial grasses as needed. Once cleared it is likely that weed species released from the soil seed bank will require invasive plant species control measures.
Mechanism
State 2 Invaded Understory transitions to State 3 Invaded Over and Understory through the process of fast-growing weeds inhibiting reproduction of native plants and gradually replacing them. This process is accelerated by feral pigs and cattle directly damaging native plants and promoting the spread of weeds by disturbing the soil and spreading weed seeds.
Mechanism
State 2 Invaded Understory may be restored to a facsimile of State 4 Native Forest. Exclusion of all ungulates is required; in many cases construction of a suitable fence will be necessary. Intensive weed control must then be initiated and maintained in the long term. In some cases, large amounts of dead weed biomass must be dealt with by removal or decomposition. Reintroduction of missing native species will be necessary.
Context dependence
It should be stated, that the most desirable ecological conditions would be to return this site to a native forest, as it would provide the highest levels of biodiversity and ecological function. Doing so will require significant inputs of time, money, and historical information not currently available.
Mechanism
State 3 Invaded Over and Understory can be converted to State 1 Reference by clearing vegetation using heavy machinery, applying aggressive weed control measures, and planting desirable forage species as needed.
Mechanism
State 4 Native Forest can transition to State 1 Reference by clearing the forest with heavy machinery and planting desirable pasture species as needed. Native forest may be cleared gradually by allowing cattle access to the forest. Cattle eventually eat or destroy understory ferns, forbs, shrubs, and saplings, opening the forest so that introduced grasses will thrive.
Constraints to recovery
Converting State 4 Native Forest to State 1 Reference would result in an irreplaceable and irretrievable action. Restoration to the site's former Native state would be unlikely without significant inputs of time, money, and historical information not currently available.
Mechanism
State 4 Native Forest transitions to State 2 Invaded Understory by the very aggressive, introduced weed species present in this ecological site invading intact native forest and gradually replacing native species in the understory. This invasion is greatly facilitated by feral pigs and cattle that damage and consume native plants, disturb the soil, and spread weed seeds.
Constraints to recovery
Converting State 2 Invaded Understory back to State 4 Native Forest would require significant inputs of time, money, and historical information not currently available.
Mechanism
State 5 Weed Invaded Grassland can be restored to State 1 Reference by brush management, re-establishment of desirable forage species, persistent weed control, and prescribed grazing.
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.