Overflow (Ov) 10-14" p.z.
Scenario model
Current ecosystem state
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Management practices/drivers
Select a transition or restoration pathway
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Transition T1A
Non-prescribed grazing, no fire, prolonged drought (5-7 years)
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Transition T1B
Non-prescribed grazing, fire (natural interval 5-7 years), extended drought (>7 years)
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Restoration pathway R2A
Prescribed grazing, fire (natural interval 5-7 years), and extended period of favorable precipitation
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Transition T2A
Non-prescribed grazing, fire (natural interval 5-7 years), drought (3-5 years)
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Restoration pathway R3A
No fire, prescribed grazing, favorable precipitation
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No transition or restoration pathway between the selected states has been described
Target ecosystem state
Select a state
Mechanism
Prolonged drought, non-prescribed grazing, and the removal of fire in the system will result in retrogression to State 2. The effects of drought and poor grazing management are readily apparent with careful observation. However, the influence of fire is more difficult to verify. Because of the continual interaction of these environmental factors, regression from State 1 may culminate in two distinct communities (Community B or C). Community B is dominated by snowberry, fringed sagewort, and silver sagebrush.
Mechanism
Prolonged drought, non-prescribed grazing, and the removal of fire in the system will result in retrogression to State 3. The effects of drought and poor grazing management are readily apparent with careful observation. However, the influence of fire is more difficult to verify. Because of the continual interaction of these environmental factors, regression from State 1 may culminate in two distinct communities (Community B or C). Community C is comprised of mostly short grasses, Kentucky bluegrass and low successional forbs.
Mechanism
The implementation of prescribed grazing and a favorable precipitation pattern normally will not induce succession from State 2 to State 1. Succession normally requires significant economic inputs. However, the Overflow 10-14” p.z. ecological site is productive. It is theorized that succession from Community B to State #1 may occur with the combination of a natural fire regime, prescribed grazing, and an extended period of favorable precipitation. This potential is depicted as a dashed arrow in the state and transition model.
The Overflow 10-14” p.z. is a productive site with deep soils on landscapes with less than 2% slope. Although the potential of using mechanical treatments to promote plant succession is limited because this site often occurs as small and irregularly shaped tracts, mechanical treatments are feasible in some places (See NRCS Conservation Practice 548). Following mechanical treatment, it is critical that grazing is deferred one or two growing seasons. Length of grazing deferment varies with precipitation and response of vegetation. Furthermore, prescribed grazing must be implemented following the deferment. Failure to do will result in economic losses and potential ecological damage to the site. With prescribed grazing and plant succession, the effective life of treatment should be greater than 10 years.
Prescribed burning may be a useful tool for promoting succession in the State #2 Plant Communities. Fire would reduce the shrubs in Community B, and also adversely impact the shallow-rooted Kentucky and Canada bluegrasses in Community C. The opening of the community will favor the establishment of new plants, if seed (and/or rhizomes) of desired plants are available. If not, range seeding may be necessary following mechanical treatment or fire.
Mechanism
Plant communities B & C are not a precise assemblage of species that remain constant from place to place or from year to year. Variability is apparent in productivity and occurrence of individual species. However, dominant status is less variable. Changes in climate, fire patterns and frequency, and grazing all play a role in determining which of the plant communities will be expressed.
Plant Community B regresses to Community C with non-prescribed grazing and/or a wildfire that removes the dominant shrubs from the community.
Mechanism
Plant communities B & C are not a precise assemblage of species that remain constant from place to place or from year to year. Variability is apparent in productivity and occurrence of individual species. However, dominant status is less variable. Changes in climate, fire patterns and frequency, and grazing all play a role in determining which of the plant communities will be expressed.
The shift from Community C to Community B might occur with a combination of a natural fire regime, prescribed grazing and an extended period of favorable precipitation. The possibility of this succession is depicted with a dashed arrow in the state and transition diagram.
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.