Shallow Loamy - South
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
- Restoration pathway R3A More details
- Transition T3A 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 represents the natural range of variability that dominates the dynamics in this ecological site. This site is dominated by warm-season grasses, with cool-season grasses being subdominant. In pre-European times the primary disturbances included fire, insects and grazing by large ungulates and small mammals. Favorable growing conditions during the spring as well as the warm months of June and July along with routine or occasional fires, reduces tree cover and contributes to the ecological processes that maintain the reference plant community. Today a similar state can be found in areas where proper livestock use has occurred and where the encroachment of trees, especially ponderosa pine, has been limited.
Submodel
Description
This state is dominated by short-grass species and is the result of repeated season-long overgrazing. Desirable plants (i.e. the species most desirable to grazing animals), which were repeatedly grazed over long periods of time, weakened and declined in size and amounts. In the early phases of this plant community transition, some mid-grasses may remain in sufficient quantities to support the recovery to the Reference State if proper grazing management is done along with the occurrence of good growing conditions. If grazing pressures continue over long time or extended drought, recovery will become less likely due to increased runoff and reduced infiltration.
Submodel
Description
This state is dominated by conifer and shrubs and most likely resulted from heavy continuous grazing and lack of frequent fire. Native warm-season grasses such as bluestems, grama grasses and associated cool-season grasses such as wheatgrasses and needlegrasses declined as overstory canopy cover increased, relinquishing space to shade tolerant grasses such as poverty oatgrass, bluegrasses, and rough-leaved ricegrass. Forbs such as cudweed sagewort and shrubs such as wood rose increased under intermediate canopy closure (< 25 percent). In the absence of fire, this plant community phase will be resistant to change. Ponderosa pine canopy will continue to increase over time, reducing the amount of precipitation that reaches the forest floor (according to Wrage (1994), ponderosa pine canopy can reduce precipitation reaching the forest floor by an average of 30 percent), and ultimately reducing the herbaceous layer. The resulting plant community is less productive for grazing animals than the other states. As ponderosa pine cover increases, herbaceous plant production decreases and bare ground increases. This results in lower water infiltration rates and increased runoff, with some soil erosion possible.
Submodel
Mechanism
Continuous season-long grazing or heavy continuous grazing with stocking rates well above the carrying capacity for the entire growing season will lead toward the dominance of short grasses, State 2.
Mechanism
Heavy continuous season-long grazing with stocking rates well above the carrying capacity for the entire growing season combined with the absence of fire to control shrub and conifer seedling establishment, or no use, no fire and encroachment will lead toward a conifer dominated state, State 3.
Mechanism
Long-term prescribed grazing which provides growing season grazing deferment along with stocking rates not exceeding carrying capacities and periodic fire or prescribed burning will restore this plant community to the Reference State.
Mechanism
Continuous season-long grazing or heavy continuous grazing with stocking rates well above the carrying capacity for the entire growing season combined with the absence of fire to control shrub and conifer seedling establishment, or no use, no fire and encroachment will lead toward a conifer dominated state, State 3.
Mechanism
Long-term prescribed grazing and prescribed fire to kill shrubs and conifers along with mechanical brush management of large trees (if needed) is projected to lead back to the reference state. Seeding of warm-season tall grass species may be needed following the removal of trees. This restoration pathway may take an extended period of time and may not be achievable; favorable growing conditions will accelerate the recovery.
Mechanism
Depending on the existing herbaceous plant species in the understory, prescribed fire and or mechanical brush management to remove conifers and long-term prescribed grazing may transition the Conifer State to the Shortgrass State. Grazing deferments and favorable growing conditions will, in time, help reestablish the plant community however management goals may not be achieved.
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.