Clayey Overflow
Scenario model
Current ecosystem state
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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 R3A More details
- Transition T3A More details
- Transition T4A More details
- Transition T4B More details
- Restoration pathway T5A More details
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No transition or restoration pathway between the selected states has been described
Target ecosystem state
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Description
The Reference State represents the best estimate of the natural range of variability that dominated the dynamics in this ecological site prior to European settlement. This state may exist but is unlikely to function within the natural range of variability due to the spread of Kentucky bluegrass and smooth brome onto this site. In the Reference State, this site is dominated by cool-season grasses and by various shrubs and trees that are scattered across the site. Grazing or the lack of grazing, flooding or lack of flooding, fire, excessive haying, and invasion of non-native cool-season grasses are the major drivers of this state. Flooding and no fire can cause a transition to the Woody Overstory State (4.0).
Submodel
Description
The Native/Invaded State (2.0) is very similar to the Reference State (1.0). The Native/Invaded State is dominated by native cool-season grasses, but invasive non-native cool-season grasses are present in all community phases. These non-native cool-season grasses can comprise up to 30 percent of total annual air-dry production. The primary disturbance mechanisms for this state include grazing by domestic livestock, infrequent fires, and flooding. Timing and intensity of grazing events coupled with weather dictate the dynamics within this state. The cool-season native grass can decrease, and a corresponding increase in non-native cool-season grasses occurs. Many times, the Native/Invaded State appears as a mosaic of community phases caused primarily by continuous season-long grazing.
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 followed by short-term intensive grazing. This state is dominated by cool-season grasses. It can be found in areas that are properly managed with grazing and prescribed burning and sometimes in areas that receive occasional short periods of rest. Warm-season species can decrease, and a corresponding increase in cool-season grasses occurs.
Submodel
Description
The Invaded State (3.0) is the result of invasion and dominance by introduced species. This state is characterized by the dominance of Kentucky bluegrass and smooth brome and by an increasing thatch layer that effectively blocks introduction of other plants into the system. Plant litter accumulation tends to favor the more shade-tolerant, introduced grass species. The nutrient cycle is also impaired, and the result is typically a higher level of nitrogen, which also favors the introduced species. Increasing plant litter decreases the amount of sunlight reaching plant crowns, thereby shifting competitive advantage to shade-tolerant introduced grass species. Studies indicate that biological activity is altered in the soil, and this shift apparently exploits the soil microclimate and encourages growth of the introduced grass species. Once the threshold is crossed, a change in grazing management alone cannot reduce the dominance of the invasive grasses. Preliminary studies indicate this threshold may exist when Kentucky bluegrass exceeds 30 percent of the plant community and native grasses represent less than 40 percent. Plant communities dominated by Kentucky bluegrass have significantly less cover and diversity of native grasses and forb species (Toledo et al., 2014).
Submodel
Description
The Wooded Overstory State (4.0) is the result of the establishment of a tree overstory and shrub mid-story canopy. This state is more common on the lower reaches of the site. The dynamics of the Wooded Overstory State are largely due to flooding and successional changes that start with establishment of cottonwood and shrubs and eventually results in the development of a green ash and boxelder plant community. The successional process can restart following another flooding event. Water control structures that limit flooding; livestock grazing; heavy wildlife browse; fire; the introduction of non-native, cool-season grasses; and encroachment by juniper can alter the dynamics of this site, resulting in old remnant stands of trees and little, if any regeneration.
Submodel
Description
The Woody Invaded State (5.0) develops as a result of continuous season-long grazing or as a result of continuous seasonal grazing and no fire combined with the invasion and establishment of Russian olive, saltcedar, or juniper trees. Over time, the cottonwood, boxelder, and ash trees that survive become mature and have little or no regeneration. This lack of regeneration is due mainly to grazing of seedlings and saplings. Wildlife browse can also contribute to the loss of native tree and shrub regeneration. Grazing that limits regeneration also results in a reduction of the desirable native herbaceous species, often resulting in a dominance of such species as bluegrass and smooth brome and such forbs as western ragweed, Canada thistle, burdock, and houndstongue.
Submodel
Mechanism
Continuous season-long grazing, excessive haying, or non-use and no fire, in combination with invasion of non-native cool-season grasses, results in the Reference Plant Community (1.1) transitioning to the Native/Invaded State (2.0).
Mechanism
Flooding, followed by long-term prescribed grazing, and no fire are necessary to shift plant community 1.1 to the Cottonwood/Prunus-Snowberry/Forbs/Grasses Plant Community (4.1). Flooding reduces herbaceous competition by scouring the soil surface and thereby provides a site for woody regeneration. Once a flooding event occurs during the proper time, a long-term period of prescribed grazing is necessary to establish and maintain a woody plant community. Grazing during the mid-summer growing season typically has an adverse effect on woody regeneration and establishment. The Woody Overstory State (4.0) is more likely to develop and persist on the mid- to lower-reaches of a drainage.
Relevant conservation practices
| Practice | External resources |
|---|---|
|
Prescribed Grazing |
Mechanism
Heavy, continuous grazing, excessive haying, or long-term light grazing cause a transition to the Invaded State (3.0). Extended periods of non-use and no fire also result in the expansion of non-native cool-season grasses on this site. The ecological threshold can be identified by the percentage of non-native cool-season species in the plant community. Preliminary studies indicate this threshold may exist when Kentucky bluegrass exceeds 30 percent of the plant community composition and native grasses represent less than 40 percent (Toledo et al., 2014). Smooth brome is assumed to follow a similar ecological threshold, but this is not documented scientifically.
Mechanism
Flooding and no fire, followed by prescribed grazing that includes proper stocking, change in season of use, and adequate time for recovery, typically transition this site to the Woody Overstory State (4.0). Timed grazing is very important and must be followed for many years for saplings to attain a height at which livestock do not damage or kill the trees. Wildlife browse can also be a concern if the management objective is to improve the overstory canopy. The Wooded Overstory State (4.0) is more common in the mid to lower-reaches of a drainageway.
Relevant conservation practices
| Practice | External resources |
|---|---|
|
Prescribed Grazing |
Mechanism
Long-term prescribed grazing (moderate stocking levels coupled with adequate recovery periods, or other grazing systems, such as high density, low-frequency grazing intended to treat specific species dominance or periodic light to moderate stocking levels, possibly including periodic rest) may lead this plant community phase over a threshold to the Native/Invaded State (2.0). Prescribed burning may also be needed to suppress cool-season invasive grasses. This restoration is likely to take a long period of time, possibly 10 years or more, and recovery may not be attainable. Success depends upon whether native propagules remain intact on the site.
Relevant conservation practices
| Practice | External resources |
|---|---|
|
Prescribed Burning |
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|
Prescribed Grazing |
Mechanism
Encroachment of juniper trees from upland sites, invasion of non-native trees, no fire for extended periods of time, continuous season-long grazing, or continuous seasonal grazing and time cause a transition to the Wooded Invaded State (5.0). Canopy cover increases as trees increase in size, which alters the microclimate and reduces fine-fuel amounts. As a result, fire intensity and frequency are reduced.
Mechanism
Fire; invasion of non-native, cool-season grasses; excessive haying; continuous season-long grazing; or continuous seasonal grazing that results in little woody regeneration and time result in the Wooded Overstory State (4.0) transitioning to the Native/Invaded State (2.0).
Mechanism
Encroachment of juniper from upland sites, invasion of non-native trees, or both, coupled with no fire and continuous season-long grazing or continuous seasonal grazing, result in the Woody Overstory State (4.0) transitioning to the Wooded Invaded State (5.0).
Mechanism
Fire, brush management that removes Russian olive and saltcedar, continuous season-long grazing, or continuous seasonal grazing transition Plant Community 5.1 to the Invaded State (3.0).
Relevant conservation practices
| Practice | External resources |
|---|---|
|
Brush Management |
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Prescribed Burning |
Model keys
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