Oxidic Dissected Lowland
Scenario model
Current ecosystem state
Select a state
Management practices/drivers
Select a transition or restoration pathway
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Transition T1A
The Reference State (1) transitions to the Weed Invaded Grassland State (5) 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
The Invaded Understory State (2) can be restored to the Reference State (1) by clearing the forest with heavy machinery and planting desirable forage species.
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Transition T2A
The Invaded Understory State (2) transitions to the Invaded Overstory and Understory State (3) 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.
More details -
Restoration pathway R2A
The Invaded Understory State (2) may be restored to a facsimile of the Native Forest State (4). Construction of a suitable fence and removal of all ungulates are 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
The Invaded Overstory and Understory State (3) can be converted to the Reference State (1) by clearing vegetation using heavy machinery, applying aggressive weed control measures, and planting desirable forage species.
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Transition T4B
The Native Forest State (4) can transition to the Reference State (1) by clearing the forest with heavy machinery and planting desirable pasture species. 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
The Native Forest State (4) transitions to the Invaded Understory State (2) 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
The Weed Invaded Grassland State (5) can be restored to the Reference State (1) by brush management, re-establishment of desirable forage species, persistent weed control, and prescribed grazing.
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Transition T5A
The Weed Invaded Grassland State (5) transitions to the Invaded Overstory and Understory State (3) due to the presence of fast-growing, introduced tree species; fire may prevent this from occurring.
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No transition or restoration pathway between the selected states has been described
Target ecosystem state
Select a state
Description
The Reference State (1) 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 species compositions of the forests consisting of introduced species are variable.
Continuous grazing results in increased abundance of less desirable forage species, as represented by the phase change from 1.1 Guineagrass/Ticktrefoil (Desmodium) to 1.2 Hilograss – Common Carpetgrass/Spiny Amaranth. Longer-term overgrazing and lack of weed control measures results in a transition to the Weed-Invaded Grassland State (5).
Submodel
Description
The Invaded Understory State (2) consists of one community phase. Native ‘ohi’a lehua and Tahitian screwpine or hala 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, the Invaded Understory State (2) transitions to the Invaded Overstory and Understory State (3) through growth of introduced tree species.
Submodel
Description
The Invaded Overstory and Understory State (3) 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 Reference State (1) is possible by using heavy machinery and applying aggressive weed control and ungulate-exclusion measures.
Submodel
Description
The Native Forest State (4) consists of one community phase. Because no examples of this state remain, the following description is historical, based on literature and historical accounts of the islands before human influences disturbed these native plant communities.
When cleared by machinery or long-term, heavy ungulate browsing, this state transitions to the Reference State (1). Gradual invasion by weedy, introduced plant species brings a transition to the Invaded Understory State (2).
Submodel
Description
The Weed Invaded Grassland State (5) 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
The Reference State (1) transitions to the Weed Invaded Grassland State (5) 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
The Invaded Understory State (2) can be restored to the Reference State (1) by clearing the forest with heavy machinery and planting desirable forage species.
Mechanism
The Invaded Understory State (2) transitions to the Invaded Overstory and Understory State (3) 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
The Invaded Understory State (2) may be restored to a facsimile of the Native Forest State (4). Construction of a suitable fence and removal of all ungulates are 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.
Mechanism
The Invaded Overstory and Understory State (3) can be converted to the Reference State (1) by clearing vegetation using heavy machinery, applying aggressive weed control measures, and planting desirable forage species.
Mechanism
The Native Forest State (4) can transition to the Reference State (1) by clearing the forest with heavy machinery and planting desirable pasture species. 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.
Mechanism
The Native Forest State (4) transitions to the Invaded Understory State (2) 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.
Mechanism
The Weed Invaded Grassland State (5) can be restored to the Reference State (1) 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.