Riparian Woodland (RW)
Scenario model
Current ecosystem state
Select a state
Management practices/drivers
Select a transition or restoration pathway
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Transition T1A
Lack of flooding disturbance, lowered water table, prolonged improper grazing, or a combination of these factors
More details -
Transition T1C
Establishment of invasive tree species (primarily Russian olive)
More details -
Transition T1B
Clear cutting, tillage or herbicide application, and seeding of cultivated crops (frequently combined with irrigation practices)
More details -
Restoration pathway R2C
Proper grazing management, tree/shrub planting, intensive weed management (management intensive and costly)
More details -
Transition T2A
Establishment of invasive tree species (primarily Russian olive)
More details -
Transition T2B
Clear cutting, tillage or herbicide application, and seeding of cultivated crops (frequently combined with irrigation practices)
More details -
Restoration pathway R3A
Removal of invasive tree species, sometimes combined with tree/shrub planting (management intensive and costly)
More details -
Transition T3B
Clear cutting, tillage or herbicide application, and seeding of cultivated crops (frequently combined with irrigation practices)
More details -
No transition or restoration pathway between the selected states has been described
Target ecosystem state
Select a state
Description
The Contemporary Reference State contains five community phases. This state is not considered to be the historic natural state but instead is an evaluation of contemporary conditions given the extreme alterations to the abiotic and biotic components of the ecosystem. Flooding disturbance is a key dynamic on this site, but it has been severely altered by manmade structures, most notably the Fort Peck dam. Frequent flooding created open alluvial bars where native cottonwood and willow species could colonize. Flood control measures typically limit such disturbances to the lowest-elevation terraces and major flooding only occurs in the most extreme of circumstances. In general, this state is resilient to grazing and fire, although these factors can influence species composition in localized areas. Woody vegetation consists of a tree overstory and a shrub understory. The principle tree species is plains cottonwood (Populus deltoides), but green ash (Fraxinus pennsylvanica) and juniper (Juniperus scopulorum) may also occur in later stages of development. Shrubs are characterized by redosier dogwood (Cornus sericea), chokecherry (Prunus virginiana), and willow species. Following disturbance, this state will exhibit an increase in seedling cottonwoods and sandbar willow (Hansen et al., 1995). Herbaceous understory has been significantly altered and is predominantly non-native species such as smooth brome (Bromus inermis) and Kentucky bluegrass (Poa pratensis). Noxious weeds are a common concern for all phases.
Submodel
States 1 and 5 (additional transitions)
1.1. Seedling Cottonwood – Sandbar Willow Community
1.5. Mature Cottonwood – Snowberry Community
Description
The Herbaceous Understory State (2) occurs when the shrub understory has been removed due to long-term improper grazing practices. The overstory typically consists of a mature, open cottonwood stand but may include other trees in some cases. The tree canopy is about 40 percent or less with tree diameters of 12 inches or more DBH. The understory consists primarily of non-native grasses, particularly smooth brome. Noxious weeds such as leafy spurge (Euphorbia esula) and Canada thistle (Cirsium arvense) may be prominent in some cases. Once the site has converted from a shrub-dominated understory to one dominated by introduced herbaceous species, returning it to its former state is very difficult. A drastic change in management is needed, and it most likely will be labor intensive and costly (Hansen et al., 1995).
Submodel
Description
The Invasive Tree State (3) occurs when invasive tree species, particularly Russian olive, establish and dominate the site. Russian olive is a highly competitive tree native to southern Europe and western Asia. It is widely established and commonly forms dense thickets at the exclusion of native species (Hansen et al., 1995). In more open stands, Russian olive may occur in conjunction with widely scattered cottonwood stands and native shrubs, such as snowberry and Woods’ rose. As the cottonwood stand dies out, Russian olive will replace it at the exclusion of the typical native tree species.
Submodel
Description
The Cropland State (4) occurs when land is put into cultivation. Deep, fertile soils and favorable moisture conditions make the Riparian Woodland ecological site prime farmland. Additionally, its proximity to perennial streams makes it ideal for irrigation. Because of this, many acres of the Riparian Woodland ecological site have been cleared and converted to farmland. It is commonly planted to non-native perennial species and irrigated for production of hay. Common species include alfalfa, orchardgrass, and grass/alfalfa mixes. Annual crops, such as wheat and barley, are commonly planted in rotation with perennial species. Silage corn is grown is some cases, but this crop is of limited extent. Flood irrigation is most common, but center pivot sprinklers are used in some areas. Cropping, irrigation projects, and the Fort Peck dam have vastly altered vegetation and hydrology on much of the Riparian Woodland ecological site. Once the site is converted to production agriculture, land values increase significantly, and it is unlikely that the site will be converted back to natural vegetation.
Submodel
Mechanism
Prolonged improper grazing management in combination with the absence of flooding disturbance transitions the Contemporary Reference State (1) to the Herbaceous Understory State (2). Prolonged improper grazing will eventually completely remove the shrub understory layer, leaving an understory of herbaceous vegetation. Long periods of low disturbance have built up banks and lowered the water table.
Mechanism
Establishment of invasive tree species, particularly Russian olive, transitions the Contemporary Reference State (1) to the Invasive Tree State (3).
Mechanism
Clearcutting, tillage or application of herbicide, and seeding of cultivated crops (such as wheat, barley or introduced hay) transitions the Contemporary Reference State (1) to the Cropland State (4).
Mechanism
Proper grazing management, tree/shrub planting, and intensive weed management can transition the Herbaceous Understory State (2) back to the Contemporary Reference State (1). A change in management alone may not be sufficient. Replanting of desirable species and intensive weed management practices are generally needed in conjunction with proper grazing management. These restoration methods are labor intensive and costly and may not be a practical in all situations.
Relevant conservation practices
| Practice | External resources |
|---|---|
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Prescribed Grazing |
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Tree/Shrub Establishment |
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Herbaceous Weed Control |
Mechanism
Establishment of invasive tree species, particularly Russian olive, transitions the Herbaceous Understory State (2) to the Invasive Tree State (3).
Mechanism
Clear cutting, tillage or application of herbicide, and seeding of cultivated crops (such as wheat, barley, or introduced hay) transitions the Herbaceous Understory State (2) to the Cropland State (4).
Mechanism
Removal of invasive tree species transitions the Invasive Tree State (3) to the Herbaceous Understory State (2). Typically, tree/shrub planting is required to reestablish native woody species. When clearing the Russian Olive/Noxious Weed Phase (4.2), intensive weed management is critical. Removal of the overstory will release understory growth and cause noxious weed populations to increase exponentially. This transition is very costly and labor intensive and may not be practical in all situations.
Relevant conservation practices
| Practice | External resources |
|---|---|
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Brush Management |
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Tree/Shrub Establishment |
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Herbaceous Weed Control |
Model keys
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