Shallow Soils on Volcanic Uplands
Scenario model
Current ecosystem state
Select a state
Management practices/drivers
Select a transition or restoration pathway
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Restoration pathway R1A
The Reference State (1) can be restored to the Native Forest State (2) by fire protection, weed control, erosion control (vetivergrass (Vetiveria sp.) is useful), mulching, fertilizing, and replanting of native plant species.
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Transition T1B
The Reference State (1) transitions to the Tree-Invaded State (3) when fire is infrequent, allowing the growth of trees and shrubs.
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Restoration pathway R1B
The Reference State (1) can be restored to Grazed State (4) by fire protection, weed control, erosion control, and planting desired forage grass species.
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Transition T1A
The Reference State (1) transitions to the Badlands State (5) through destruction of vegetation cover and surface litter by fire, leading to loss of surface soil horizons by erosion and slumping (Amidon et al., 2019; Amidon et al., 2017; Fosberg, 1960; Stone, 1970; USDA-SCS, 1988; Wagner and Grether, 1948; Willsey et al., 2019).
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Transition T2A
The Native Forest State (2) transitions to the Reference State (1) by destruction of the forest by human-caused fire in adjacent stands of Pacific Island silvergrass or swordgrass.
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Restoration pathway R3A
The Tree-Invaded State (3) is restored to the Reference State (1) by fire.
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Restoration pathway R3C
The Tree-Invaded State (3) may be restored to the Native Forest State (2). The intensity of active restoration measures will be determined by the presence or lack of native trees already on the site as well as the density and species mix of grasses, vines, shrubs, and introduced trees present on the site, especially if many competitive introduced species are present.
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Transition R3B
The Tree-Invaded State (3) may be restored to the Grazed State (4) by clearing the forest, maintaining erosion control, weed control, and seeding desired forage grasses.
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Transition T3A
The Tree-Invaded State (3) transitions to the Badlands State (5) through destruction of tree cover and surface litter by fire, leading to loss of surface soil horizons by erosion and slumping. Soil slumping is considered rare in forested sites in the Marianas Islands.
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Transition T4A
The Grazed State (4) can transition to the Reference State (1) by reinvasion of weedy species, particularly Pacific Island silvergrass and forbs.
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Transition T4B
The Grazed State (4) can transition to the Tree-Invaded State (3) by abandonment or light grazing that allows establishment of trees and shrubs.
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Transition T4C
The Grazed State (4) can transition to the Badlands State (5) by overgrazing that reduces cover of vegetation and litter to a point at which soil erosion removes the upper soil horizons.
More details -
Restoration pathway R5A
The Badlands State (5) can be partially restored to the Reference State (1) by instituting erosion control measures that result in patches of soil accumulation. More information is needed about grasses and other plants that may establish with seeding and mulching on the Cr (weathered rock) horizon.
More details -
Restoration pathway R5B
The Badlands State (5) can be restored to the Tree-Invaded State (3) by instituting erosion control measures and excluding fire. Replanting trees, either native, introduced, or both, can then be successful with mulching, fertilization, and addition and maintenance of soil organic matter.
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) is medium to tall (to 6.5 feet or 2 meters) grassland. The consensus of most authors indicates that these grasslands did not exist in the southern Marianas Islands until humans arrived and started burning the ubiquitous forests of these islands (Athens and Ward, 2004). However, naturally occurring grassland is considered to occur on certain locations on the young stratovolcano islands of the northern end of the island chain (Amidon et al., 2019; Amidon et al., 2017; Fosberg, 1960; Stone, 1970; USDA-SCS, 1988; Wagner and Grether, 1948; Willsey et al., 2019).
The Reference State (1) is highly prone to fire; most fires appear to be set intentionally. The soils are vulnerable to erosion and slumping, especially when vegetation cover is low. This can lead to formation of badlands, especially on steeper slopes (Amidon et al., 2019; Amidon et al., 2017; Fosberg, 1960; Stone, 1970; USDA-SCS, 1988; Wagner and Grether, 1948; Willsey et al., 2019).
The grass and forb species in this state are sometimes used for grazing. However, the forage value is low (USDA-SCS, 1988).
Submodel
Description
The Native Forest State (2) has two community phases consisting of native forest species. No intact examples of the original native forest remain, so the species list is historical and based on remnant plants and species persisting in ravines. The consensus of authors suggests that fire was probably not an important disturbance in these forests before humans arrived. The main disturbance was storm damage due to typhoons. Due to the shallow soils, tree stature may be shorter than in other ecological sites of the volcanic landscapes of the Marianas, and tree throw is probably more frequent (Amidon et al., 2019; Amidon et al., 2017; Fosberg, 1960; Stone, 1970; USDA-SCS, 1988; Wagner and Grether, 1948; Willsey et al., 2019).
Submodel
Description
This state consists of one community phase dominated by a variable mixture of small trees, shrubs, vines, forbs, and grasses that thrive in the absence of fire.
Submodel
Description
The Grazed State (4) is grassland with one community phase.
Submodel
Description
The Badlands State (5) consists of one community phase. It is sparsely vegetated with much bare ground. Most of the upper soil horizons has been eroded away. However, the saprolite (soft, weathered rock beneath the soil) has neutral pH and may be usable by roots to some extent (Amidon et al., 2019; Amidon et al., 2017; Fosberg, 1960; Stone, 1970; USDA-SCS, 1988; Wagner and Grether, 1948; Willsey et al., 2019).
Submodel
Mechanism
The Reference State (1) can be restored to the Native Forest State (2) by fire protection, weed control, erosion control (vetivergrass (Vetiveria sp.) is useful), mulching, fertilizing, and replanting of native plant species.
Mechanism
The Reference State (1) transitions to the Tree-Invaded State (3) when fire is infrequent, allowing the growth of trees and shrubs.
Mechanism
The Reference State (1) can be restored to Grazed State (4) by fire protection, weed control, erosion control, and planting desired forage grass species.
Mechanism
The Reference State (1) transitions to the Badlands State (5) through destruction of vegetation cover and surface litter by fire, leading to loss of surface soil horizons by erosion and slumping (Amidon et al., 2019; Amidon et al., 2017; Fosberg, 1960; Stone, 1970; USDA-SCS, 1988; Wagner and Grether, 1948; Willsey et al., 2019).
Mechanism
The Native Forest State (2) transitions to the Reference State (1) by destruction of the forest by human-caused fire in adjacent stands of Pacific Island silvergrass or swordgrass.
Mechanism
The Tree-Invaded State (3) is restored to the Reference State (1) by fire.
Mechanism
The Tree-Invaded State (3) may be restored to the Native Forest State (2). The intensity of active restoration measures will be determined by the presence or lack of native trees already on the site as well as the density and species mix of grasses, vines, shrubs, and introduced trees present on the site, especially if many competitive introduced species are present.
Mechanism
The Tree-Invaded State (3) may be restored to the Grazed State (4) by clearing the forest, maintaining erosion control, weed control, and seeding desired forage grasses.
Mechanism
The Tree-Invaded State (3) transitions to the Badlands State (5) through destruction of tree cover and surface litter by fire, leading to loss of surface soil horizons by erosion and slumping. Soil slumping is considered rare in forested sites in the Marianas Islands.
Mechanism
The Grazed State (4) can transition to the Reference State (1) by reinvasion of weedy species, particularly Pacific Island silvergrass and forbs.
Mechanism
The Grazed State (4) can transition to the Tree-Invaded State (3) by abandonment or light grazing that allows establishment of trees and shrubs.
Mechanism
The Grazed State (4) can transition to the Badlands State (5) by overgrazing that reduces cover of vegetation and litter to a point at which soil erosion removes the upper soil horizons.
Mechanism
The Badlands State (5) can be partially restored to the Reference State (1) by instituting erosion control measures that result in patches of soil accumulation. More information is needed about grasses and other plants that may establish with seeding and mulching on the Cr (weathered rock) horizon.
Mechanism
The Badlands State (5) can be restored to the Tree-Invaded State (3) by instituting erosion control measures and excluding fire. Replanting trees, either native, introduced, or both, can then be successful with mulching, fertilization, and addition and maintenance of soil organic matter.
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.