Isohyperthermic Forest
Scenario model
Current ecosystem state
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Management practices/drivers
Select a transition or restoration pathway
- Transition T1A More details
- Transition T1B More details
- Restoration pathway R2A More details
- Transition T2A More details
- Transition T2B More details
- Transition R3A More details
- Transition T4A More details
- Transition T5A More details
- Restoration pathway R5A 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
This state consists of one community phase. The general aspect is a forest with a tall (to about 80 feet or 25 meters), closed to open overstory, a secondary canopy of diverse trees species 25 to 40 feet (8 to 12 meters) tall, an open tree fern canopy 10 to 15 feet (3 to 4.5 meters) tall, and a diverse understory of shrubs, vines, and ferns.
When cleared by machinery or long-term, heavy ungulate browsing, this state transitions to State 4 Naturalized Grassland. Gradual invasion by weedy, introduced plant species brings a transition to State 2 Invaded Understory.
Submodel
State 2
Invaded Understory State
Description
This state consists of one community phase. Native ohia lehua trees still dominate the overstory. However, introduced trees, shrubs, vines, and ferns produce a dense layer of low, competitive vegetation that severely inhibits reproduction of native species. Many native species are still present in this plant community but their abundance is much reduced. Activity of feral pigs and cattle further reduces native plant abundance and produces bare, disturbed soil patches that promote weed invasion. Eventually, this state transitions to State 3 Invaded Overstory and Understory through growth of introduced tree species.
Submodel
Description
This state consists of one community phase dominated by introduced species in both the overstory and understory. Some tall native trees may persist for a long time, and a few native species appear able to reproduce and maintain low populations. The diversity of weedy trees, shrubs, vines, ferns, and herbs is high. Conversion to State 4 Naturalized Grassland is possible by using heavy machinery and applying aggressive weed control measures.
Submodel
State 4
Naturalized Grassland State
Description
This state consists of two community phases dominated by introduced grass species. Continuous grazing results in increased abundance of less desirable forage species and presence of weedy shrubs, as represented by the phase change from 4.1 Californiagrass to 4.2 Hilograss – broomsedge bluestem/sourbush. Longer-term overgrazing and lack of weed control measures results in a transition to State 5 Weed-Invaded Grassland.
Submodel
Description
This state consists of one community phase consisting primarily of weedy shrubs. Weedy grasses and forbs dominate between shrub patches. Introduced tree species are present and will attain dominance if fire does not set them back. Average annual rainfall is relatively high, producing large amounts of fine fuels that present a fire danger in dry periods.
Submodel
Mechanism
This state transitions to State 2 Invaded Understory by the very aggressive, introduced weed species present in this ecological site invading intact native forest and gradually replacing native species in the understory. This invasion is greatly facilitated by feral pigs and cattle that damage and consume native plants, disturb the soil, and spread weed seeds.
Mechanism
This state may be restored to a facsimile of State 1 Reference. Pig-proof fence and removal of all ungulates are necessary. Intensive weed control must then be initiated and maintained in the long term. In some cases, large amounts of dead weed biomass must be dealt with by removal or decomposition. Reintroduction of missing native species is likely to be necessary.
Mechanism
This state transitions to State 3 Invaded Over and Understory through the process of fast-growing weeds inhibiting reproduction of native plants and gradually replacing them. This process is accelerated by feral pigs and cattle directly damaging native plants and promoting the spread of weeds by disturbing the soil and spreading weed seeds.
Mechanism
This state can transition to State 4 Naturalized Grassland by clearing the forest with heavy machinery and planting desirable forage species. Native forest may be cleared gradually by allowing cattle access to the forest. Cattle eventually eat or destroy understory ferns, forbs, shrubs, and saplings, opening up the forest so that introduced forage species will thrive. On shallow soils over lava substrates, underlying lava rock may be ripped and crushed by heavy machinery. Ripping and crushing produces fine mineral particles and small, abundant gaps between the rock fragments. When this is done on organic soils, about 50% of the soil organic matter may be lost in the process due to exposure to air and higher temperatures.
Mechanism
This state can be converted to State 4 Naturalized Grassland by clearing vegetation using heavy machinery, applying aggressive weed control measures, and planting desirable forage species. On shallow soils over lava substrates, underlying lava rock may be ripped and crushed by heavy machinery. Ripping and crushing produces some fine mineral particles and small, abundant gaps between the rock fragments. When this is done on organic soils, about 50% of the soil organic matter may be lost in the process due to exposure to air and higher temperatures.
Mechanism
This state transitions to State 5 Weed Invaded Grassland by long-term continuous grazing and lack of weed control measures. Remnant desirable forages have been grazed out and replaced entirely by weedy grasses, forbs, shrubs, and small trees.
Mechanism
This state transitions to State 3 Invaded Over and Understory due to the presence of fast-growing, introduced tree species; wildfire may prevent this from occurring.
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.