Slough (Sl)
Scenario model
Current ecosystem state
Select a state
Management practices/drivers
Select a transition or restoration pathway
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Transition T1A
Introduction of non-native species (creeping bentgrass, Kentucky bluegrass, etc.)
More details -
Transition T2A
Displacement of reference species by invasive species (reed canarygrass, noxious weeds, etc.)
More details -
Transition T2B
Alteration of hydrology by dams, dikes, irrigation, etc.
More details -
Restoration pathway R4A
Restoration of natural hydrology and species diversity (labor intensive and costly, may be unfeasible in some cases)
More details -
Transition T4B
Displacement of reference species by invasive species (reed canarygrass, noxious weeds, etc.)
More details -
No transition or restoration pathway between the selected states has been described
Target ecosystem state
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Description
The Historic Reference State (1) contained three community phases characterized by varying degrees of seasonal ponding. This state is considered extinct and is included here for historical reference purposes. Seasonal ponding was a key dynamic on this site and varied depending on annual precipitation patterns and groundwater inputs. Vegetation was typically characterized by zones within the site that corresponded to the hydroperiod of that particular zone. Phases usually exhibit two or more zones with the most hydrophytic vegetation in the center of the site and subsequent, drier plant communities toward the edges. Cyclical periods of drought and wet were a crucial ecological process on this site that promoted regeneration of key species such as hardstem bulrush (Schoenoplectus acutus) and broadleaf cattail (Typha latifolia). This cyclical pattern occurred, on average, every 10 to 20 years and increased stand longevity and species diversity (Luna et. al., 2010).
Submodel
Description
The Contemporary Reference State (2) contains three community phases. Seasonal ponding is a key dynamic on this site and varies depending on annual precipitation patterns and groundwater inputs. This state differs from the historical reference state in that it is influenced by nonnative plant species and has altered fire and grazing regimes. Vegetation is typically characterized by zones that correspond to the hydroperiod of that particular zone. Phases usually exhibit two or more zones with the most hydrophytic vegetation in the center of the site and subsequent, drier plant communities toward the edges. Cyclical periods of drought and wet are a crucial ecological process on this site that promotes regeneration of key species such as hardstem bulrush and broadleaf cattail. This cyclical pattern occurs, on average, every 10 to 20 years and improves stand longevity and species diversity (Luna et. al., 2010).
Submodel
Description
The Invaded State (3) occurs when invasive plant species invade adjacent plant communities and displace the native species. Data suggest that native species diversity declines significantly when invasive species exceed 30 percent of the plant community. The most common concern is reed canarygrass (Phalaris arundinacea), which is a vigorous, productive, long-lived, perennial, sod-forming grass. Although native to North America, it may become weedy or invasive in some habitats and may displace desirable vegetation if not properly managed (USDA-NRCS, 2002). Introduced bluegrasses, such as Kentucky bluegrass (Poa pratensis) may also be a concern, primarily around the fringes of this ecological site. Kentucky bluegrass is widespread throughout the Northern Great Plains (Toledo et al., 2014). It is very competitive and displaces native species by forming dense root mats, altering nitrogen cycling, and having allelopathic effects on germination (DeKeyser et al., 2013). It may also alter soil surface hydrology and modify soil surface structure (Toledo et al., 2014). Other non-native species such as creeping bentgrass (Agrostis stolonifera) may also be common in this state.
Noxious weeds are rare on the Slough ecological site, however, weeds such as purple loosestrife (Lythrum salicaria) and Eurasian watermilfoil (Myriophyllum spicatum) could become a major concern if established on this site. These species are very aggressive perennials that typically displace native species and dominate ecological function when they invade a site. Sometimes, these species can be suppressed through intensive management (herbicide, biological control, or intensive grazing management). Control efforts are unlikely to eliminate noxious weeds, but their density can be sufficiently suppressed so that species composition and structural complexity are similar to that of the Contemporary Reference State (2). However, cessation of control methods will most likely result in recolonization of the site by the noxious species.
Submodel
Description
The Hydrologically Altered State (4) occurs when hydrology is altered by damming, irrigation projects, or water impoundment. Natural drought/wet cycles are reduced or eliminated and the associated variations in hydroperiod are diminished. The result is a perpetual Aquatic Phase (2.3) and a reduction in biodiversity and emergent vegetation regeneration. This state is particularly common in the river valleys where large storage reservoirs have regulated stream flows and flood irrigation has raised water tables across much of the floodplain.
Submodel
Mechanism
Introduction of non-native grass and forb species occurred in the early 20th century. The naturalization of these species in relatively undisturbed grasslands, coupled with changes in fire and grazing regimes, transitions the Reference State (1) to the Contemporary Reference State (2).
Mechanism
The Contemporary Reference State (2) transitions to the Invaded State (3) when aggressive perennial grasses or noxious weeds displace native species. The precise triggers of this transition are not clear, but data suggest that exclusion of grazing and fire may be a contributing factor in some cases (DeKeyser et al., 2013). In addition, other rangeland health attributes, such as reproductive capacity of native grasses and soil quality, have been substantially altered.
Mechanism
Hydrologic alteration due to dams, irrigation, impoundment, or a combination of factors will transition the Contemporary Reference State (2) to the Hydrologically Altered State (4).
Mechanism
Restoration of natural hydrology and species diversity transitions the Hydrologically Altered State (4) to the Contemporary Reference State (2). Restoration of natural hydrology may require removal of dams or diversions, and alteration of irrigation practices. Depending on site conditions, revegetation may be required to restore species diversity. Specialized seeding techniques may be necessary as well as intensive weed control to prevent invasion of exotic species and noxious weeds. These restoration methods are labor intensive, very costly, and may be impractical, perhaps even detrimental, in some situations.
Relevant conservation practices
| Practice | External resources |
|---|---|
|
Wetland Restoration |
|
|
Herbaceous Weed Control |
Mechanism
The Hydrologically Altered State (4) transitions to the Invaded State (3) when aggressive perennial grasses or noxious weeds displace native species. The precise triggers of this transition are not clear, but rangeland health attributes, such as reproductive capacity of native grasses and soil quality, have been substantially altered.
Model keys
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