Natural Resources
Conservation Service
Scenario model
Current ecosystem state
Select a state
Management practices/drivers
Select a transition or restoration pathway
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Transition T1A
Heavy continuous grazing, non-use, no fire, invasion
More details -
Transition T1B
Conifer invasion, no fire
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Transition T2A & T2B
Non-use, no fire, heavy continuous grazing
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Restoration pathway T3A
Long term prescribed grazing, prescribed burning
More details -
Transition T3B
Conifer invasion, no fire
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Restoration pathway T4A
Brush management, prescribed burning
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Restoration pathway T4B & T4D
Brush management, prescribed burning
More details -
Restoration pathway T4C
Brush management
More details -
No transition or restoration pathway between the selected states has been described
Target ecosystem state
Select a state
Description
The Reference State represents the natural range of variability that dominated the dynamics of this ecological site (ES). This state was dominated by warm-season grasses, with cool-season grasses being subdominant. Prior to 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. In some locations, this site likely received relatively heavy grazing pressure. Cool-season and Tall warm-season grasses would have declined and corresponding increase in short warm-season grasses would have occured. Today, a similar state, the Native/Invaded State (State 2) can be found on areas that are properly managed with grazing and/or prescribed burning, and sometimes on areas receiving occasional short periods of rest.
Submodel
Description
The Native/Invaded State represents the more common range of variability that exists with higher levels of grazing management, but in the absence of periodic fire due to fire suppression. This state is dominated by cool- and warm-season grasses. It can be found on areas that are properly managed with grazing and/or prescribed burning and sometimes on areas receiving occasional short periods of rest. Taller warm-season species can decline and a corresponding increase in short-statured grass will occur.
Submodel
Description
The Invaded State is a result of encroachment mainly by invasive introduced cool-season grasses. The ecological processes are not functioning, especially the biotic processes and the hydrologic functions. The introduced cool-season grasses cause reduced infiltration and increased runoff. Preliminary studies would tend to indicate this threshold may exist when Kentucky bluegrass exceeds 30 percent of the plant community and native grasses represent less than 40 percent of the plant community composition. The opportunity for high intensity spring burns is severely reduced by early green-up, and increased moisture and humidity at the soil surface and grazing pressure cannot cause a reduction in sod-grass dominance. Production is limited to the sod-forming species. Infiltration continues to decrease, runoff increases, and energy capture into the system is restricted to early season low producing species. Nutrient cycling is limited by root depth of the dominant species.
Submodel
Description
The Conifer/Invaded State is dominated (canopy exceeds 20 percent of total surface area) by areas where trees have become established or have encroached onto the site due to the absence of periodic fire. This state is dominated by eastern redcedar and/or Rocky Mountain juniper with cool-season grasses being subdominant. The plant community can develop into a closed canopy that impedes the reproductive capability of the major native perennial grass species. A single eastern redcedar tree with a 7 foot crown diameter eliminates the equivalent of 3 pounds of forage. Further, the forage potential of a pasture with 250 mature eastern redcedar trees per acre (or one tree every thirteen feet) is reduced by 50 percent. It is suggested that reducing stocking rates by 10 percent for every 50 trees per acre. The increase in tree canopy which is a result of a disruption of the natural, and human related fire regimes that occurred prior to European settlement in North America, which kept trees from encroaching much of the grasslands.
Submodel
Mechanism
Non-use, no surface fire for 10 or more years (causing litter levels to become high enough to reduce native grass vigor, diversity, and density), heavy, continuous grazing, or invasion of non-native plant species will likely lead this state over a threshold resulting in the Native/Invaded State (State 2).
Mechanism
No surface fire for extended periods of time (typically for 10 or more years) causing litter levels to become high enough to reduce native grass vigor, diversity, and density, and invasion of conifer will likely lead this state over a threshold leading to the 4.1 Eastern Redcedar-Rocky Mountain Juniper/Big Bluestem Plant Community Phase within the Conifer/Invaded State (State 4).
Mechanism
Non-use and/or no surface fire for extended periods of time (typically for 10 or more years) causing litter levels to become high enough to reduce native grass vigor, diversity, and density, will likely lead this state over a threshold leading to the 3.1 Kentucky Bluegrass-Smooth Bromegrass-Forbs/Shrubs Plant Community Phase within the Invaded State (State 3). 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), will likely lead this state over a threshold leading to the 3.2 Kentucky Bluegrass-Sideoats Grama Plant Community Phase within the Invaded State (State 3). Grazing repeatedly in the early growing season can expedite this shift by causing mechanical disturbance due to trampling.
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), prescribed burning occurring every 3 to 5 years, and a return to normal disturbance regime levels and frequencies may lead this Invaded State (State 3) over a threshold to the Native/Invaded State (State 2).
Mechanism
No surface fire for extended periods of time (typically for 10 or more years) causing litter levels to become high enough to reduce native grass vigor, diversity, and density, and invasion of conifer will likely lead this state over a threshold leading to the 4.2 Eastern Redcedar-Rocky Mountain Juniper/Kentucky Bluegrass Plant Community Phase within the Conifer/Invaded State (State 4).
Mechanism
Brush management (which would include the mechanical removal of the conifers), coupled with prescribed burning every 3 to 5 years, and a return to normal disturbance regime levels and frequencies may lead this 4.1 Eastern Redcedar-Rocky Mountain Juniper/Big Bluestem Plant Community Phase within the Conifer/Invaded State (State 4) over a threshold to the Reference State (State 1).
Mechanism
Brush management (which would include the mechanical removal of the conifers), coupled with prescribed burning every 3 to 5 years, and a return to normal disturbance regime levels and frequencies may lead this 4.2 Eastern Redcedar-Rocky Mountain Juniper/Kentucky Bluegrass Plant Community Phase within the Conifer/Invaded State (State 4) over a threshold to the Native/Invaded State (State 2). Brush management (which would include the mechanical removal of the conifers), coupled with prescribed burning every 3 to 5 years, and a return to normal disturbance regime levels and frequencies may lead this 4.3 Eastern Redcedar-Rocky Mountain Juniper Plant Community Phase within the Conifer/Invaded State (State 4) over a threshold to the Native/Invaded State (State 2).
Mechanism
Brush management, which would include the mechanical removal of the conifers, may lead this 4.2 Eastern Redcedar-Rocky Mountain Juniper/Kentucky Bluegrass Plant Community Phase within the Conifer/Invaded State (State 4) over a threshold to the Invaded State (State 3).
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.
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