Loamy
Scenario model
Current ecosystem state
Select a state
Management practices/drivers
Select a transition or restoration pathway
- Transition T1b More details
- Transition T1a More details
- Transition T2a/b More details
- Transition T2c More details
- Restoration pathway R3a/b More details
- Transition T4 More details
- Transition T6 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 dominates the dynamics of this ecological site. This state is dominated by cool season grasses. The primary disturbance mechanisms for this site in the reference condition include frequent fire and grazing by large herding ungulates. Timing of fires and grazing coupled with weather events dictate the dynamics that occur within the natural range of variability. Cool season species can decline and a corresponding increase in warm season grasses will occur.
Submodel
Description
This state is very 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 is still dominated by native cool season grass, 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 and duration of grazing coupled with weather events dictate the dynamics that occur within this state. The cool season native grasses 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 brome. This state is characterized by these two species and an increasing thatch layer that effectively blocks introduction of other plants into the system. Once the state is well established, even drastic events such as high intensity fires driven by high fuel loads of litter and thatch, 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
Description
A wooded state may occupy this site when it occurs in association with river drainages and within close proximity to wooded loamy floodplain sites which serve as seed sources for the tree and shrub species. Elimination of fire as a disturbance factor and alteration of the historic grazing regimes resulted in the scattered shrub patches forming almost continuous woody dominated plant communities across the site. This state is characterized by an overstory of tall trees such as bur oak and green ash an understory of small trees and shrubs such as ironwood and chokecherry. Depending upon the amount of canopy cover, an herbaceous shade tolerant understory of sedges, smooth bromegrass, wildrye and/or Kentucky bluegrass may also be present.
Submodel
Description
The introduction of non-native species and elimination of the fire as a disturbance mechanism results in a tree and shrub dominated plant community with an understory of native and non-native shade tolerant herbaceous species.
Submodel
Mechanism
This is the transition from the native cool 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 cool season bunchgrasses and an increase in cool season sodgrasses. Chronic season long or heavy late season grazing facilitate this transition. Complete rest from grazing and no fire events can also lead to this transition. The threshold between states is crossed when Kentucky bluegrass becomes established on the site.
Mechanism
This is the transition from the native herbaceous or herbaceous/shrub dominated Reference State to a state that is dominated by mature trees and shrubs. This transition occurs on those Loamy sites located along major river systems and in close proximity to frequently flooded Loamy Overflow ecological sites. These flooded sites served as a source of seed for trees and shrubs which, coupled with an alteration of the fire frequency following settlement, permitted this transition from an herbaceous dominated plant community to a woody dominated community. Increasing tree size and canopy cover altered the micro-climate and reduced fine fuel amounts, reducing fire frequency and intensity.
Mechanism
T2a - Several combinations of events can occur to initiate this pathway. Severe repeated late season grazing or burning will favor the shift to sod forming grasses and sedges. Chronic heavy season-long grazing will also favor this shift. Along this pathway, the timing of energy capture shifts from spring and early summer to early spring and mid-summer. The change in plant functional and structural groups and the composition and distribution of the vegetation cause a decrease in production and an increase in runoff with a corresponding decrease in infiltration. Nutrient cycling is restricted as the rooting depth of the vegetation decreases with the change in functional and structural groups. Plant community diversity is reduced with a loss of leguminous forbs and minor grass components.
T2b - This pathway is initiated with any action that allows the introduced Kentucky bluegrass to increase. Heavy late season or chronic season-long grazing will favor this change. Total rest from grazing and no fire events will also initiate this pathway. The change in plant functional and structural groups and the composition and distribution of the vegetation causes a decrease in production and an increase in runoff with a corresponding decrease in infiltration. Nutrient cycling is restricted as the rooting depth of the vegetation decreases with the change in functional and structural groups. Available nitrogen increases due to invasive legumes (black medic and sweetclover) which alters the carbon to nitrogen ratio, favoring non-native, nitrogen dependent species such as Kentucky bluegrass.
Mechanism
Removal of all disturbance from Loamy sites which are located adjacent to Loamy Overflow sites with existing trees to serve as seed sources.
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.
R3b - 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 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 plant species, management objectives must include the maintenance of those species, the associated reference state functions, and the continued treatment of the introduced sodgrasses.
Mechanism
This transition occurs when non-native species and/or invasive native species invade the site. This may include such species as Kentucky bluegrass, smooth bromegrass, buckthorn and Eastern redcedar.
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.