Rocky Alluvium Naturalized Grassland (Koa haole/guineagrass/glycine)
Scenario model
Current ecosystem state
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Management practices/drivers
Select a transition or restoration pathway
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Restoration pathway R1A
It may be possible to restore State 1 to a plant community resembling State 3 Native Forest. Weed control would 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. A firebreak must be created and maintained, and domestic and feral ungulates must be excluded by a suitable fence. Extensive planting of native species would follow.
More details -
Transition T1A
State 1 transitions to State 4 Shrub Invaded Grassland after abandonment and, if wildfires do not occur, gradual invasion of weedy shrubs and small trees. If the site contained abundant koa haole before abandonment, these small trees will overtop the guineagrass and greatly increase their cover.
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Transition T2A
State 2 transitions to State 1 Reference by land clearing with heavy machinery followed up 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
State 2 Invaded Understory may be restored to a facsimile of State 3 Native Forest, by removal of the introduced understory through application of herbicides and/or hand weeding. Reintroduction of native understory species is required. The site must be fenced securely to exclude ungulates, and a firebreak is needed to protect against wildfire.
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Transition T2B
State 2 transitions to State 5 Exotic Tree Invaded 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
State 3 Native Forest transitions to State 1 Reference (Naturalized Grassland) by clearing the forest with heavy machinery and planting desirable forage species.
More details - Restoration pathway T3A More details
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Restoration pathway R4A
State 4 Shrub Invaded Grassland can be restored to State 1 Reference 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. For large, densely weedy sites or if fast results are not required, it is possible to eliminate invasive small trees, shrubs, and undergrowth by planting glycine (Neonotonia wightii) to overtop and shade out weeds; this is done in conjunction with foraging by sheep and goats to consume smaller weeds. Eventually, the dead trees and shrubs collapse under the weight of the glycine; the glycine is then eaten by the livestock. This process takes about eight years (Gordon Cran, Kapapala Ranch, personal communication, 2006).
More details -
Transition T4A
State 4 Shrub Invaded Grassland transitions to State 5 Exotic Tree Invaded in the absence of disturbance such as fire. Fast-growing introduced tree species invade Shrub Invaded Grassland and quickly overtop shrubs.
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Restoration pathway R5B
State 5 Exotic Tree Invaded may be restored to State 1 Reference. Total clearing of the site would be necessary. If clearing is done by heavy machinery, soil disturbance would occur. This would 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 would have to be excluded until forages are well established; prescribed grazing must then be applied.
More details -
Restoration pathway R5A
It may be possible to restore State 5 Exotic Tree Invaded to a community resembling State 3 Native Forest . Total clearing of the site would be necessary. Alternatively, it may be worthwhile to kill taller weed species in place by herbicide applications in order to provide some shelter from the sun. If clearing is done by heavy machinery, soil disturbance would occur. This would induce germination of the weed seed bank and increase the potential for soil erosion. Weed control and brush management would be long-term. A firebreak must be created and maintained, and ungulates would have to be excluded by a suitable fence.
More details -
No transition or restoration pathway between the selected states has been described
Target ecosystem state
Select a state
Description
This state consists of two community phases. It is naturalized grassland with introduced grasses, forbs, and trees. Scattered, large trees are often present.
Submodel
Description
This state 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 wildfire.
Submodel
Description
This state consists of one community phase. This description is partly hypothetical, because little native vegetation remains in this ecological site. The following description is based on similar ecological sites on the Island of Hawaii. The general appearance of this ecological site is an open to nearly closed canopy of lama (Diospyros sandwicensis), an understory of shrubs and small trees, and a ground layer of vines, forbs, and grasses. The canopy becomes shorter and sparser where the forest grades into drier and/or windier areas near the coast.
Submodel
Description
This state consists of one community phase. It may have developed from abandoned grazing land, land cleared by wildfire, 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 State 5 Exotic Tree Invaded.
Submodel
Description
This state 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 State 1 to a plant community resembling State 3 Native Forest. Weed control would 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. A firebreak must be created and maintained, and domestic and feral ungulates must be excluded by a suitable fence. Extensive planting of native species would follow.
Mechanism
State 1 transitions to State 4 Shrub Invaded Grassland after abandonment and, if wildfires do not occur, gradual invasion of weedy shrubs and small trees. If the site contained abundant koa haole before abandonment, these small trees will overtop the guineagrass and greatly increase their cover.
Mechanism
State 2 transitions to State 1 Reference by land clearing with heavy machinery followed up 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
State 2 Invaded Understory may be restored to a facsimile of State 3 Native Forest, by removal of the introduced understory through application of herbicides and/or hand weeding. Reintroduction of native understory species is required. The site must be fenced securely to exclude ungulates, and a firebreak is needed to protect against wildfire.
Mechanism
State 2 transitions to State 5 Exotic Tree Invaded 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
State 3 Native Forest transitions to State 1 Reference (Naturalized Grassland) by clearing the forest with heavy machinery and planting desirable forage species.
Mechanism
State 3 Native Forest transitions to State 2 Invaded Understory through grazing, browsing, rooting, and trampling by domestic or feral ungulates (cows, 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 wildfires that destroy the native tree canopy. This transition may be avoided by excluding domestic livestock and feral ungulates from the site with fencing or animal control measures and by implementing invasive plant species control.
Mechanism
State 4 Shrub Invaded Grassland can be restored to State 1 Reference 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. For large, densely weedy sites or if fast results are not required, it is possible to eliminate invasive small trees, shrubs, and undergrowth by planting glycine (Neonotonia wightii) to overtop and shade out weeds; this is done in conjunction with foraging by sheep and goats to consume smaller weeds. Eventually, the dead trees and shrubs collapse under the weight of the glycine; the glycine is then eaten by the livestock. This process takes about eight years (Gordon Cran, Kapapala Ranch, personal communication, 2006).
Mechanism
State 4 Shrub Invaded Grassland transitions to State 5 Exotic Tree Invaded in the absence of disturbance such as fire. Fast-growing introduced tree species invade Shrub Invaded Grassland and quickly overtop shrubs.
Mechanism
State 5 Exotic Tree Invaded may be restored to State 1 Reference. Total clearing of the site would be necessary. If clearing is done by heavy machinery, soil disturbance would occur. This would 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 would have to be excluded until forages are well established; prescribed grazing must then be applied.
Mechanism
It may be possible to restore State 5 Exotic Tree Invaded to a community resembling State 3 Native Forest . Total clearing of the site would be necessary. Alternatively, it may be worthwhile to kill taller weed species in place by herbicide applications in order to provide some shelter from the sun. If clearing is done by heavy machinery, soil disturbance would occur. This would induce germination of the weed seed bank and increase the potential for soil erosion. Weed control and brush management would be long-term. A firebreak must be created and maintained, and ungulates would have to be excluded by a suitable fence.
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