Thin Upland
Scenario model
Current ecosystem state
Select a state
Management practices/drivers
Select a transition or restoration pathway
- Transition T1a More details
- Transition T1b More details
- Transition T2a More details
- Transition T2b More details
- Restoration pathway R3 a/b More details
- Transition T3a 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
Select a state
Description
This state represents the natural range of variability that dominated the dynamics of this ecological site. Historically, this state was dominated by mid statured warm and cool season bunch grasses. The primary disturbance mechanisms for this site in the reference condition included frequent fire and grazing by large herding ungulates. Timing of fires and grazing coupled with weather events dictated the dynamics that occurred within the natural range of variability. Dominance would have shifted between the warm/cool season mid statured bunchgrass phase and the short statured warm season/grass-like phase due to changes in precipitation patterns, fire frequency, and grazing frequency/intensity Individual species would have varied greatly in production depending on growing conditions (timing and amount of precipitation and temperature).
Slight shifts would have occurred in the timing of energy capture, hydrologic function and nutrient cycling between plant community phases within State 1. High basal density, minimal bare ground, and deep root systems resulted in low runoff rates and high infiltration. Overall, the ecological processes were functioning near optimum levels.
Submodel
Description
This state is similar to the reference state. The invasion of introduced cool-season sodgrasses has altered the natural range of variability for this ecological site. This state still has a strong component of warm and cool season bunch grass species, but invasive introduced cool-season sodgrasses are now present in all community phases of this state. The primary disturbance mechanisms for this state include grazing by domestic livestock and infrequent fires. Timing of fires and grazing coupled with weather events dictate the dynamics that occur within this state. The warm-season native grass can decline and an increase in introduced sod grasses will occur. Many times, this state appears as a mosaic of community phases caused primarily by continuous season-long grazing.
Submodel
Description
This state is the result of invasion and dominance of Kentucky bluegrass and/or smooth bromegrass. This state is characterized by these two species and an increasing litter layer that effectively blocks introduction of other plants into the system and/or prevents existing native plants from effectively competing for resources. Once this state is well established, even drastic events such as high intensity fires driven by high fine fuel loads of litter will not result in more than a very short term reduction of these two species. These events may reduce the dominance of the sodgrasses, but due to the large amount of rhizomes in the soil there is no opportunity for the native species to establish and dominate before the sodgrasses rebound and again dominate the system.
Submodel
Mechanism
This is the transition from the native warm-season grass dominated reference state to a state that has been invaded by introduced cool-season grass species. When propagules of Kentucky bluegrass are present, this transition occurs as natural and/or management actions favor a decline in the composition of warm and cool season bunch grasses and an increase in cool-season sodgrasses. This transition is compounded by a change in the historic grazing and fire regime where native herbivores would follow periodic fires with grazing. This historic grazing/fire sequence has largely been replaced by chronic season-long or heavy late season grazing. Complete rest from grazing and suppression of fire can also lead to this transition. The threshold between states is crossed when Kentucky bluegrass, smooth brome, and other introduced species become established on the site. These species typically are part of functional/structural groups that were not present in the Reference State.
Mechanism
Removal of vegetative cover and tilling for agricultural crop production.
Mechanism
Non-use and no fire. Lack of disturbances shifts the competitive advantage to the non-native species.
Mechanism
Removal of vegetative cover and tilling for agricultural crop production.
Mechanism
R3a - This restoration pathway may be initiated with the combination of prescribed burning followed by high levels of prescribed grazing management. The success of this restoration pathway depends on the presence of a remnant population of native grasses in community phase 3.1. This remnant population may not be readily apparent without close inspection. The application of prescribed burning may be needed at relatively short intervals in the early phases of this restoration process. Some previous efforts have shown promise with early season prescribed burning; however, fall burning may also be effective under certain circumstances. Both prescribed grazing and prescribed burning are necessary to successfully initiate this restoration pathway. Caution with the first series of burns is needed so as not to damage crowns of remnant native grasses.
R3b - This pathway requires the use of range seeding using native species adapted to this site. It may be possible using selected plant materials and agronomic practices to approach something very near the functioning of the Native/Invaded State (State 2). Application of chemical herbicides, possibly in conjunction with prescribed burning and the use of mechanical seeding methods using adapted varieties of the dominant native grasses are possible and can be successful. After establishment of the native grasses, management objectives must include the maintenance of those species, the associated reference state functions, and continued treatment of the introduced sodgrasses or the seeding will revert to 3.1.
Mechanism
Removal of vegetative cover and tilling for agricultural crop production.
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.