Isothermic Ustic Naturalized Grassland
Scenario model
Current ecosystem state
Select a state
Management practices/drivers
Select a transition or restoration pathway
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Restoration pathway R1A
It may be possible to restore the Reference State (1) to a plant community resembling the Native Forest State (3). Weed control must be applied to forage species and the many opportunistic plant species that would invade the site. Weed control would be a perpetual process to maintain the site. Fire and domestic and feral ungulates must be excluded. Extensive planting of native species would follow. If severe soil erosion has occurred, more intensive restoration measures are needed.
More details -
Transition T1A
The Reference State (1) transitions to the Shrub Invaded Grassland State (4) after abandonment and, if wildfires do not occur, gradual invasion of weedy shrubs and small trees. If the site contained abundant white leadtree (koa haole) before abandonment, these small trees would overtop the grasses and greatly increase in abundance unless heavily browsed.
More details -
Transition T2A
The Invaded Understory State (2) transitions to the Reference State (1) by land clearing with heavy machinery or fire followed by weed control. Land clearing would probably promote germination of the weed seed bank in the soil, requiring herbicidal control. After clearing and weed control, the site would be planted to forage species.
More details -
Restoration pathway R2A
The Invaded Understory State (2) may be restored to the Native Forest State (3) by removal of the introduced understory through intensive weed control. Reintroduction of native understory species is required. The site must be fenced securely to exclude ungulates. If severe soil erosion has occurred, more intensive restoration measures are needed.
More details -
Transition T2B
The Invaded Understory State (2) transitions to the Exotic Tree Invaded State (5) by growth of introduced tree species through and above the native canopy. Lack of reproduction leads to gradual loss of most native tree species.
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Transition T3B
The Native Forest State (3) transitions to the Reference State (1) by clearing the forest and planting desirable forage species.
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Transition T3A
The Native Forest State (3) transitions to the Invaded Understory State (2) through grazing, browsing, rooting, and trampling by domestic or feral ungulates (cattle, sheep, deer, goats, and pigs). These activities destroy small native plant species and seedlings and saplings of large species. Regeneration of the native forest is prevented, leading to tree populations consisting almost entirely of mature plants. Lack of competition from native plants, introduction of weed seeds, and disturbance of the soil lead to an understory dominated by introduced plant species. Weeds can invade intact native forest even in the absence of ungulates and gradually bring about the transition. Invasive vines, shrubs, and small trees will grow under intact native canopies and begin to degrade the forest. Eventually, introduced grasses provide fine fuels that can carry fires that destroy the native tree canopy.
More details -
Restoration pathway R4A
The Shrub Invaded Grassland State (4) can be restored to the Reference State (1) by brush management with follow-up control of resprouting shrubs and emerging weedy forbs. Forage species may then be replanted and maintained by prescribed grazing. If severe soil erosion has occurred, more intensive restoration measures are needed.
More details -
Transition T4A
The Shrub Invaded Grassland State (4) transitions to the Exotic Tree Invaded State (5) with lack of fire. Fast-growing introduced tree species invade Shrub Invaded Grassland and quickly overtop shrubs.
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Restoration pathway R5B
The Exotic Tree Invaded State (5) may be restored the Reference State (1). Total clearing of the site would be necessary. If clearing is done by heavy machinery, soil disturbance would occur. This would probably induce germination of the weed seed bank and increase the potential for soil erosion. Weed control and brush management must then be applied multiple times to control new weed germination and resprouting. After clearing and weed control, the site would be planted to forage species. Ungulates must be excluded until forages are well established; prescribed grazing must then be applied.
More details -
Restoration pathway R5A
It may be possible to restore the Tree Invaded State (5) to a community resembling the Native Forest State (3). Total clearing of the site would be necessary. Alternatively, it may be worthwhile to kill taller weed species in place to provide some shelter from the sun. If clearing is done by heavy machinery, soil disturbance would occur. This could induce germination of the weed seed bank and increase the potential for soil erosion. Weed control and brush management would be long-term. Fire and ungulates must be excluded. If severe soil erosion has occurred, more intensive restoration measures are needed.
More details -
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. It is naturalized grassland with introduced grasses, forbs, and scattered shrubs and trees. With continuous heavy grazing, preferred forage grasses decrease. Less preferred grass, forb, and shrub species increase under such circumstances. With severe deterioration, shrubby species can increase to eventually dominate, causing a transition to the Shrub Invaded Grassland State (4).
Submodel
Description
The Invaded Understory State (2) consists of one community phase having an open canopy of common native trees with an understory of introduced grasses, ferns, vines, small trees, and shrubs. Foraging by feral or domestic ungulates removes native understory plants and prevents regeneration of overstory species, resulting in a mature and diminishing canopy of native trees. This may occur more gradually by weed invasion into intact native forest. The understory of this plant community contains fine fuels that are susceptible to fire.
Submodel
Description
The Native Forest State (3) consists of one community phase. Very little native vegetation remains in this ecological site. The following description is historical, based on literature and historical accounts of the islands before human influences disturbed these native plant communities and on similar ecological sites on the Island of Hawaii. The general appearance of this ecological site is an open to nearly closed canopy up to 40 feet (12 meters) tall, an understory of shrubs and small trees, and a sparse ground layer of vines, forbs, and grasses. The canopy becomes shorter and sparser where the forest grades into drier or windier areas.
Submodel
Description
The Shrub Invaded Grassland State (4) consists of one community phase. It may have developed on abandoned grazing land, land cleared by fire, or abandoned farmland. Shrubs are dominant in canopy cover and stature. Typically, an array of introduced grass species is present. There is a moderate but increasing cover of small trees, some which potentially can grow to large stature. This tree cover creates the potential for a transition to the Exotic Tree Invaded State (5).
Submodel
Description
The Exotic Tree Invaded State (5) is comprised of one community phase dominated by introduced trees. Density and composition of understory shrubs, forbs, and grasses varies greatly with overstory closure and height, which affects the susceptibility of this plant community to fire. The density, vigor, and biomass of introduced vegetation can be very high, making restoration to other states expensive and difficult.
Submodel
Mechanism
It may be possible to restore the Reference State (1) to a plant community resembling the Native Forest State (3). Weed control must be applied to forage species and the many opportunistic plant species that would invade the site. Weed control would be a perpetual process to maintain the site. Fire and domestic and feral ungulates must be excluded. Extensive planting of native species would follow. If severe soil erosion has occurred, more intensive restoration measures are needed.
Mechanism
The Reference State (1) transitions to the Shrub Invaded Grassland State (4) after abandonment and, if wildfires do not occur, gradual invasion of weedy shrubs and small trees. If the site contained abundant white leadtree (koa haole) before abandonment, these small trees would overtop the grasses and greatly increase in abundance unless heavily browsed.
Mechanism
The Invaded Understory State (2) transitions to the Reference State (1) by land clearing with heavy machinery or fire followed by weed control. Land clearing would probably promote germination of the weed seed bank in the soil, requiring herbicidal control. After clearing and weed control, the site would be planted to forage species.
Mechanism
The Invaded Understory State (2) may be restored to the Native Forest State (3) by removal of the introduced understory through intensive weed control. Reintroduction of native understory species is required. The site must be fenced securely to exclude ungulates. If severe soil erosion has occurred, more intensive restoration measures are needed.
Mechanism
The Invaded Understory State (2) transitions to the Exotic Tree Invaded State (5) by growth of introduced tree species through and above the native canopy. Lack of reproduction leads to gradual loss of most native tree species.
Mechanism
The Native Forest State (3) transitions to the Reference State (1) by clearing the forest and planting desirable forage species.
Mechanism
The Native Forest State (3) transitions to the Invaded Understory State (2) through grazing, browsing, rooting, and trampling by domestic or feral ungulates (cattle, sheep, deer, goats, and pigs). These activities destroy small native plant species and seedlings and saplings of large species. Regeneration of the native forest is prevented, leading to tree populations consisting almost entirely of mature plants. Lack of competition from native plants, introduction of weed seeds, and disturbance of the soil lead to an understory dominated by introduced plant species. Weeds can invade intact native forest even in the absence of ungulates and gradually bring about the transition. Invasive vines, shrubs, and small trees will grow under intact native canopies and begin to degrade the forest. Eventually, introduced grasses provide fine fuels that can carry fires that destroy the native tree canopy.
Mechanism
The Shrub Invaded Grassland State (4) can be restored to the Reference State (1) by brush management with follow-up control of resprouting shrubs and emerging weedy forbs. Forage species may then be replanted and maintained by prescribed grazing. If severe soil erosion has occurred, more intensive restoration measures are needed.
Mechanism
The Shrub Invaded Grassland State (4) transitions to the Exotic Tree Invaded State (5) with lack of fire. Fast-growing introduced tree species invade Shrub Invaded Grassland and quickly overtop shrubs.
Mechanism
The Exotic Tree Invaded State (5) may be restored the Reference State (1). Total clearing of the site would be necessary. If clearing is done by heavy machinery, soil disturbance would occur. This would probably induce germination of the weed seed bank and increase the potential for soil erosion. Weed control and brush management must then be applied multiple times to control new weed germination and resprouting. After clearing and weed control, the site would be planted to forage species. Ungulates must be excluded until forages are well established; prescribed grazing must then be applied.
Mechanism
It may be possible to restore the Tree Invaded State (5) to a community resembling the Native Forest State (3). Total clearing of the site would be necessary. Alternatively, it may be worthwhile to kill taller weed species in place to provide some shelter from the sun. If clearing is done by heavy machinery, soil disturbance would occur. This could induce germination of the weed seed bank and increase the potential for soil erosion. Weed control and brush management would be long-term. Fire and ungulates must be excluded. If severe soil erosion has occurred, more intensive restoration measures are needed.
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.