Natural Resources
Conservation Service
Scenario model
Current ecosystem state
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Management practices/drivers
Select a transition or restoration pathway
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Transition T1A & T1B
Heavy continuous grazing, invasion,
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Restoration pathway T2A
Long term prescribed grazing
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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 natural range of variability that dominated the dynamics of this ecological site (ES). This state was dominated by cool-season grasses, with warm-season grasses being subdominant. Before European settlement in North America, the primary disturbance mechanisms for this site in the Reference condition included periods of below and above average precipitation, periodic fire, and herbivory by insects and large ungulates. Timing of fires and herbivory coupled with weather events dictated the dynamics that occurred within the natural range of variability. Wheatgrass species can decline and a corresponding increase in foxtail barley (Hordeum jubatum), short, warm-season grasses and forbs would will occur. Under extended periods of disturbance, the main change is a reduction in vigor and production and an increase in bare ground and forb composition.
Interpretations are based primarily on the 1.1 Reference Plant Community Phase, which are also considered to be climax. This plant community evolved with grazing by large herbivores and occasional fire, as well as, periodic flooding and drying, and can be maintained with prescribed grazing, prescribed burning, or areas receiving occasional short periods of rest or deferment. This plant community phase has two sub-phases, just referred to as plant communities here. These sub-phases are mainly driven by precipitation and flooding and drying sequences.
Submodel
Description
This state represents the range of variability that exists with reduced vigor and production of the dominant species as a result of grazing-induced disturbance and the introduction of non-native species. This state is dominated by cool-season grasses. It can be found on areas that are impacted by extended periods of heavy, continuous grazing. Grazing tolerant species become dominant, and non-native species are present.
Submodel
Mechanism
Heavy, continuous grazing (stocking levels well above carrying capacity for extended portions of the growing season, and often at the same time of year each year, typically beginning early in the season) and invasion of non-native plant species will convert the 1.1 Common Spikerush-Pale Dock Plant Communtity Subphase within the Reference State (State 1) to the 2.2 Curly Dock-Foxtail Barley Plant Community Phase within the Native/Invaded State (State 2). Heavy, continuous grazing (stocking levels well above carrying capacity for extended portions of the growing season, and often at the same time of year each year, typically beginning early in the season) and invasion of non-native plant species will convert the 1.2 Western Wheatgrass-Inland Saltgrass Plant Community Phase within the Reference State (State 1) to the 2.1 Foxtail Barley-Inland Saltgrass Plant Community Phase within the Native/Invaded State (State 2).
Mechanism
Long-term prescribed grazing (moderate stocking levels coupled with adequate recovery periods, or other grazing systems such as high-density, low-frequency intended to treat specific species dominance, or periodic light to moderate stocking levels possibly including periodic rest) may lead the Native/Invaded State (State 2) over a threshold to the Reference State (State 1).
Model keys
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Ecological sites
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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.
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