Ustic Isomesic Forest
Scenario model
Current ecosystem state
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Management practices/drivers
Select a transition or restoration pathway
- Transition T1A More details
- Restoration pathway R2A More details
- Transition T2A More details
- Restoration pathway R2B More details
- Restoration pathway R3A More details
- Restoration pathway R4A More details
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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
The Reference State consists of one community phase. There is a distinctive subtype of this phase present on Puuwaawaa and Puuanahulu that, although much disturbed, contains additional plant species similar to those found in ecological site F160XY500 Deep Volcanic Ash Kipuka Forest. Throughout this ecological site, much of the original forest has been cleared or otherwise disturbed. Description of this state is based on extensive observations of remnant forest stands and fenced restoration areas, scattered examples of the various plant species, and historical descriptions.
Submodel
State 2
Naturalized Grassland with >25% Tree Cover State
Description
This state is comprised of three grassland community phases that have an open canopy of remnant native trees. Trees provide shade and protection from the elements to livestock. Where shade is denser, cool season (C3), introduced meadow ricegrass or weeping grass (Microlaena stipoides) to become dominant over warm season (C4) forage grasses in some areas. Very little tree regeneration occurs, so the trees eventually die out over many years.
Community phase 2.1 typically consists of kikuyugrass (Pennisetum clandestinum) with an admixture of legumes. Meadow ricegrass may dominate in shady areas. Continuous grazing that does not allow favored forage species time to recover from defoliation results in community phase 2.2, which is dominated by lower value forage species but contains enough remnant kikuyugrass to allow for a transition back to phase 2.1 with prescribed grazing. Removal of livestock leads to community phase 2.3, which consists of dense cover of native and/or introduced shrubs, remnant grasses, and seedlings and saplings of native and/or introduced trees.
Submodel
State 3
Naturalized Grassland with <25% Tree Cover State
Description
This state consists of three community phases that are grassland with either a sparse canopy of native trees or no trees at all. The lack of shade prevents the cool season (C3) introduced grass meadow ricegrass or weeping grass (Microlaena stipoides) from becoming abundant.
Community phase 3.1 typically consists of kikuyugrass (Pennisetum clandestinum) with an admixture of legumes. Continuous grazing that does not allow favored forage species time to recover from defoliation results in community phase 3.2, which is dominated by lower value forage species but contains enough remnant kikuyugrass to allow for a transition back to phase 2.1 with prescribed grazing. Removal of livestock leads to community phase 3.3, which consists of native and/or introduced shrubs, remnant grasses, and invasive vines.
Submodel
State 4
Restored Koa State
Description
This state consists of one community phase. Koa seeds may remain viable in the soil for decades and can be induced to germinate by scarifying, or scraping, the soil surface with a bulldozer. If mature koa trees are present, suckers from their roots can quickly grow into spaces with sufficient sunlight. Thinning is necessary once the koa reach sufficient stature.
Submodel
Mechanism
This state will transition to State 2 Naturalized Grassland with >25% Tree Cover by removing the native understory, either by heavy equipment or, more gradually, by continuous cattle grazing. Preferred forage grasses are then established by sprigging or seeding.
Restoration pathway R2A
Mechanism
This state may be restored to a facsimile of State 1 Reference. Herbicidal weed control must be applied to forage species and the many opportunistic weed species that invade the site. Weed control would be a perpetual process to maintain the site. All ungulates must be excluded from the restoration site by a suitable fence. Domestic ungulates would be useful to manage vegetation outside the restoration site perimeter. Extensive planting of native species would follow. In some areas there may be a residual koa seed bank that could be encouraged to sprout by herbicide treatment of grasses followed by soil scarification by heavy machinery. Increased shade from trees growing on the site will cause a shift from warm season (C4) introduced grasses to cool season (C3), shade-tolerant meadow ricegrass (Microlaena stipoides). Meadow ricegrass can be almost as detrimental as kikuyugrass to establishment of native plants, so it must be controlled by herbicide.
Transition T2A
Mechanism
This state will transition to State 3 Native Grassland with <25% Tree Cover by intense wildfire. Alternatively, long term grazing will greatly reduce reproductive success of native trees, leading to gradual loss of the trees through natural mortality.
Restoration pathway R2B
Mechanism
Koa trees can rapidly form a dense stand on these sites from seed bank germination stimulated by mechanical soil scarification, root suckering from remnant koa, and/or replanting. Herbicidal control of weeds, including forage grasses, facilitates this process.
Restoration pathway R3A
Mechanism
Koa trees can rapidly form a dense stand on these sites from seed bank germination stimulated by mechanical soil scarification, root suckering from remnant koa, and/or replanting. Control of weeds, including forage grasses, facilitates this process.
Mechanism
This state may be restored to a facsimile of State 1 Reference either by gradual reinvasion of the site from nearby native seed sources or by replanting. Koa may be restored by scarifying any remaining soil seed bank. Weed control will be necessary to eliminate weeds that are present or invade the site, as well as to reduce grass cover. Ungulates must be excluded from the site by a suitable fence.
Model keys
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Ecological sites
Major Land Resource Areas
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.