Gravelly Slopes
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 T2B More details
- Transition T2A More details
- Restoration pathway R3A More details
- Transition T3B More details
- Transition T3A More details
- Transition T4A 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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Description
The reference state represents the plant communities and ecological dynamics of the Gravelly Slopes site. This state includes the biotic communities that become established on the ecological site under the natural disturbance regime prior to pre-European settlement. The main pathways on this site are fire and drought. This site is a mixed grassland-shrubs complex. Grasses are dominant and cover is fairly uniform with few large bare areas present are needle-and-thread, New Mexico Feathergrass, Indian ricegrass and western wheatgrass are the dominant grass species. Sagebrush, four-wing saltbush and winterfat are the dominant shrubs. Annual forbs occur in high abundance in spring and summer month during years of above-average precipitation. In some areas, especially in the southern portion of HV-2, pinyon pine and juniper also occur on this site. When part of the potential plant community, pinyon pine and juniper are more abundant on north and east slopes with a canopy ranging from 3 to 10 percent.
Reference state is self-sustaining and resistant to change due to high resistance to natural disturbances and high resilience following natural disturbances. When natural disturbances occur, the rate of recovery is variable due to disturbance intensity. Once invasive plants establish, return to the reference state may not be possible. Continuous grazing, which allows repetitive grazing of the desirable species, eventually leads to a decrease in these species from the plant community. Such deterioration is indicated by a decrease in needlegrasses, Indian ricegrass, sideoats grama, four-wing saltbush, and winterfat. Species that increase include galleta, blue grama, dropseed spp., threeawn spp., and undesirable woody species. A planned grazing system with periodic deferment is best to maintain the desirable balance between plant species and to maintain high productivity.
Submodel
Description
This state is characterized by a loss of grass cover and an increase in pinyon and juniper. Shrub species such as rubber rabbitbrush, big sagebrush, and Wyoming big sagebrush may also increase in representation. It is thought that pinyon and juniper, with an understory of mostly perennial grasses, may dominate the site in the longtime absence of fire, but lightning fires following warm dry early summer weather are a natural feature of the region. This could have maintained much of the site in a grassland cover, as reported by many early settlers except for occasional trees and isolated patches. Such vegetation is the basis for the potential described here. Without fire, simulated clearing methods may be necessary to maintain it (Miller and Tausch 2002). This state typically occurs when there is a long time span between fires. The transition to this state also has a reduction in fine fuels plays a part in increasing the fire return intervals once the site has transition to this pinyon-juniper state. Thus, state can persist for long time periods until the conditions needed for a fire occur or vegetation treatments are done to move the community to a different state.
Submodel
Description
This state results from seeding introduced perennial grasses (i.e. crested wheatgrass and Russian wildrye). Native perennial grasses, forbs and shrubs may be included in the seed mix. This state behave similar community dynamics to the current potential state community. Other vegetation treatments may be necessary to get to this state, they include chaining, mowing, disking, prescribed burning and other techniques which manipulate the plant community. Applying vegetation treatments to plant communities to either the invasive annuals or pinyon-juniper encroachment states to create a seeded state is often the first step in assisted restoration to plant communities an intermediate step to get to the Reference State. The seeded state could persist for long periods of time with proper management. Native grasses and forbs may reestablish over time from nearby seed sources.
Submodel
Description
This state is dominated by invasive annual species. Invasive annual species can including cheatgrass, Russian thistle, kochia, halogeton, storksbill geranium, and annual mustards. Generally as ecological conditions deteriorate and perennial vegetation decreases due to disturbance (fire, over grazing, drought, off road vehicle overuse, erosion, etc.) annual forbs and grasses will invade the site. The presence of these species will depend on soil properties and moisture availability; however, these invaders are highly adaptive and can flourish in many locations. Once established, complete removal is difficult but suppression may be possible.
Submodel
Mechanism
This transition is from the native shrub and perennial warm and cool season grass state, to a state that is dominated by two-needle pinyon and one-seed juniper. Events include time without disturbance, insect herbivory, continuous season long grazing of perennial grasses, drought, and tree invasion. As canopy density increase, bare ground will increase in size and frequency further increasing the fire return interval, accelerating erosion, increasing run-off and further affecting the watershed functionality. Loss of herbaceous cover can also reduce fuel levels beyond the point capable of carrying fire. This transition also favors the establishment of invasive annual species such as cheatgrass.
Mechanism
This transition is from a shrub dominated state, to a state that has been seeded with introduced perennial grasses. High energy inputs are needed for this transition. Shrubs and/or trees will need to be removed with vegetation treatment techniques (I.e. chemical, mechanical, or fire) and introduced species that are adapted to the area and adapted to management needs have been seeded and become established.
Mechanism
Pathways can be one or more of the following: brush treatments, seeding, insect herbivory/pathogen, proper grazing, drought, and/or fire. This pathway requires lots of energy input into the system. Prescribed grazing will help ensure adequate deferment period or rest following brush control and/or seeding, and will assist in the establishment and maintenance of grass cover. Erosion control would be necessary to prevent further nutrient and soil loss. The addition of organic matter or other soil amendments may be needed to restore soil fertility and facilitate grass recovery.
Mechanism
Seeding of introduced/native species (grasses and forbs) is the pathway to state 3. Also, trees are usually removed by mechanical or chemical treatments. This transition requires energy input into the system.
Mechanism
This transition is from a two needle pinyon and one-seed juniper state, to a state that is dominated by invasive species. Events would include establishment of invasive species, fire, and other methods of tree removal with an understory that is dominated by invasive annual species (i.e. cheatgrass).
Mechanism
This return path could possible occur as a result of long time frames without disturbance. Native plants from adjacent site would slow establish in the seeded state. Proper grazing from livestock and wildlife which would favor the establishment of native plants. Removal of the one-seed juniper and pinyon as they encroach would also be necessary
Mechanism
This transition is from the shrub-seeded grass state to a state that is dominated by two-needle pinyon and one-seed juniper. Events include, fire suppression, time without disturbance, insect herbivory, continuous season long grazing of perennial grasses, and tree invasion. As canopy density increase, bare ground will increase further increasing the fire return interval, accelerating erosion, increasing run-off and further affecting the watershed functionality. This transition also favors the establishment of invasive annual species such as cheatgrass.
Mechanism
This transition is from a seeded state, to a state that is dominated by invasive species. Events include increased of invasive species, shortened fire return interval, and long term drought. Improper continuous season long grazing of perennial grasses can reduce the time needed for this pathway.
Mechanism
This transition requires fire return intervals to length and fire suppression may be necessary to interrupted the shorten fire return intervals that occur when cheatgrass and other annuals invade. Juniper will encroach onto the site with time and lack of fire. Seeding may be necessary to establish perennial plants. This could require significant energy inputs to make this transition happen.
Mechanism
Invasive annuals will need to be treated and dominance suppress enough to allow desired seeded species the ability to complete so that they can become established. Seeding of introduced species is the pathway to state 3. This transition will be difficult and require substantial inputs and management of the site. It may not be practical on a large scale. Research is needed for species adapted to compete with annual invasive plants, and seeding techniques to add with successful transition from the invasive annual state.
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.