Organic Surface Forest
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, can transition to State 2 Invaded Understory, by gradual replacement of the native understory by introduced shrubs, vines, and small trees that outcompete the native understory species. This process is accelerated by ungulate foraging that disturbs the soil surface and directly destroys native plants and prevents their regeneration.
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Transition T1B
State 1 Reference will transition to State 4 Naturalized Grassland by clearing the forest with heavy machinery. Desired forages such as Californiagrass (Urochloa mutica) or guineagrass (Urochloa maxima) may then be established, or less desirable grass and sedge species will establish on their own.
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Restoration pathway R2A
It is possible to restore a facsimile of State 1 Reference State from State 2 Invaded Understory. Before restoration of native plants, introduced understory plants must be eliminated by weed control measures, and ungulates must be excluded from the restoration site by a suitable fence. Native species that have been eliminated or greatly reduced in numbers must be restored by replanting. Long-term control of weeds will be necessary.
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Transition T2A
The large native ohia lehua and other tree species that form the overstory of State 2 Invaded Understory are unable to successfully regenerate due to the dense, shady understory of introduced species. Eventually the large native trees die and are replaced by introduced tree species.
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Transition T2B
State 2 Invaded Understory State will transition to State 4 Naturalized Grassland by mechanical clearing. Introduced forage grasses may then be seeded or sprigged into the site. Weed control measures will be necessary before and during pasture establishment to control reemerging weed species.
More details -
Restoration pathway R3A
State 3 Invaded Over and Understory State may be restored to State 4 Naturalized Grassland by mechanical clearing of overstory and understory vegetation. Introduced forage grasses may then be seeded or sprigged into the site. Weed control measures will be necessary before and during forage establishment to control reemerging weed species.
More details -
Restoration pathway R4A
Restoration to State 1 Reference is possible by erecting an ungulate-proof fence, removing all domestic and feral ungulates, and intensive and long-term weed and brush control accompanying replanting of common native species. Restoration will be much more difficult if the site is in Community Phase 4.3, in which many fast-growing and competitive species such as strawberry guava and black bamboo are already strongly-established.
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Transition T4A
State 4 Naturalized Grassland State will transition to State 3 Invaded Overstory and Understory by abandonment of cleared land, including removal of domestic cattle. However, if large numbers of feral cattle are present, the site may remain in State 4, Community Phase 4.3.
More details -
No transition or restoration pathway between the selected states has been described
Target ecosystem state
Select a state
Description
The Reference State consists of one community phase consisting of medium-stature rainforest.
This state transitions into State 2 Invaded Understory by weed invasion; the transition is accelerated by disturbance from domestic and feral ungulates. It transitions to State 4 Naturalized Grassland by mechanical clearing or gradual clearing by uncontrolled grazing and browsing by ungulates, followed by establishment of forage grasses or invasion by weedy introduced grasses.
Submodel
Description
This state consists of one community phase. It arises by invasion by introduced species of intact native forest (the Reference State) or, in some cases, of native overstory stands from which the original understory has been cleared. Native species are unable to regenerate in the highly competitive understory of introduced plants and eventually die out. With time, large, introduced tree species will emerge to replace the native overstory trees and form a new overstory. When this last step has occurred, the site will have transitioned to State 3 Invaded Overstory and Understory.
Disturbance of the soil and direct damage to native understory plants by introduced ungulates, particularly pigs and cattle, will speed the transition to this state by killing native plants and by creating better germination sites for introduced species.
Restoration to the Reference State or a facsimile of it is possible by fencing the site, removing all ungulates, applying weed control measures, and replanting native species when needed. Restoration efforts will be affected depending on the degree of invasion by introduced species and by the species that have invaded the site. Long term weed management and fence maintenance will be necessary.
Submodel
Description
This state is comprised of one plant community dominated by introduced species in both the overstory and understory. Understory vegetation usually is very sparse to nonexistent. Remnant individuals of a few native species may persist. This state might be considered a dead end as far as further succession. Mechanical clearing followed by establishment of introduced forage species would bring a transition to State 4 Naturalized Grassland.
Submodel
Description
This state consists of three grassland community phases with little or no tree overstory. These phases are maintained by grazing, which keeps preferred species from becoming too tall, and adequate recovery periods, which ensure vigor and cover of preferred species. High production of preferred grass species and extensive cover allow for increased soil moisture retention, vegetative production, and overall soil quality. These factors are degraded by grazing practices that result in loss of preferred grass species leading to increase in less desirable grasses, weed invasion, and an increase in the extent of bare soil.
Community phase 4.1, when subjected to continuous grazing that does not allow the preferred forage species to recover from defoliation, shifts to Community phase 4.2, which is dominated by lower value grass species but contains enough cover of preferred forages to allow for a shift back to Phase 4.1 with prescribed grazing. Longer-term continuous grazing leads to Community Phase 4.3, which consists of low value grass species and increasing cover of weedy shrubs and tree saplings. Improvement of this phase requires weed control followed by prescribed grazing.
This state occurs mostly at lower elevations of the ecological site.
Submodel
Mechanism
State 1, Reference, can transition to State 2 Invaded Understory, by gradual replacement of the native understory by introduced shrubs, vines, and small trees that outcompete the native understory species. This process is accelerated by ungulate foraging that disturbs the soil surface and directly destroys native plants and prevents their regeneration.
Mechanism
State 1 Reference will transition to State 4 Naturalized Grassland by clearing the forest with heavy machinery. Desired forages such as Californiagrass (Urochloa mutica) or guineagrass (Urochloa maxima) may then be established, or less desirable grass and sedge species will establish on their own.
Mechanism
It is possible to restore a facsimile of State 1 Reference State from State 2 Invaded Understory. Before restoration of native plants, introduced understory plants must be eliminated by weed control measures, and ungulates must be excluded from the restoration site by a suitable fence. Native species that have been eliminated or greatly reduced in numbers must be restored by replanting. Long-term control of weeds will be necessary.
Mechanism
The large native ohia lehua and other tree species that form the overstory of State 2 Invaded Understory are unable to successfully regenerate due to the dense, shady understory of introduced species. Eventually the large native trees die and are replaced by introduced tree species.
Mechanism
State 2 Invaded Understory State will transition to State 4 Naturalized Grassland by mechanical clearing. Introduced forage grasses may then be seeded or sprigged into the site. Weed control measures will be necessary before and during pasture establishment to control reemerging weed species.
Mechanism
State 3 Invaded Over and Understory State may be restored to State 4 Naturalized Grassland by mechanical clearing of overstory and understory vegetation. Introduced forage grasses may then be seeded or sprigged into the site. Weed control measures will be necessary before and during forage establishment to control reemerging weed species.
Mechanism
Restoration to State 1 Reference is possible by erecting an ungulate-proof fence, removing all domestic and feral ungulates, and intensive and long-term weed and brush control accompanying replanting of common native species. Restoration will be much more difficult if the site is in Community Phase 4.3, in which many fast-growing and competitive species such as strawberry guava and black bamboo are already strongly-established.
Mechanism
State 4 Naturalized Grassland State will transition to State 3 Invaded Overstory and Understory by abandonment of cleared land, including removal of domestic cattle. However, if large numbers of feral cattle are present, the site may remain in State 4, Community Phase 4.3.
Model keys
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