Woody Draw (WD)
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 grass species, such as Kentucky bluegrass, smooth brome, etc.
More details -
Transition T2A
Stand-replacing fire in combination with prolonged improper grazing management
More details -
Transition T2B
Prolonged improper grazing management
More details -
Restoration pathway R3A
Proper grazing management, tree/shrub planting, intensive weed management (management intensive and costly)
More details -
Restoration pathway R4A
Proper grazing management, tree/shrub planting, intensive weed management (management intensive and costly)
More details -
No transition or restoration pathway between the selected states has been described
Target ecosystem state
Select a state
Description
The Historic Reference State (1) contained one community phase characterized by three primary vegetation layers: trees, shrubs, and herbaceous species. Primary species were green ash (Fraxinus pennsylvanica), chokecherry (Prunus virginiana), and native grasses. This state is considered extinct and is included here for historical reference purposes. It evolved under the combined influences of climate, grazing, and fire. Climatic variation generally had the greatest influence on cover and production. In general, this state was resilient to grazing, however, heavy grazing pressure could influence species composition in localized areas. This state was believed to be resilient to fire. Most tree and shrub species in this state are capable of re-sprouting from crowns or roots following fire (Coladonato, 1992; Fryer, 1997; Johnson, 2000; Gucker, 2005). Woody vegetation would likely recover from fire in 3 years or less.
Submodel
Description
The Contemporary Reference State (2) contains three community phases phase characterized by three primary vegetation layers: trees, shrubs, and herbaceous species. It evolved under the combined influences of climate, grazing, and fire, with climatic variation having the greatest influence on cover and production. This state differs from the historical reference state in that it is influenced by introduced plant species and has altered fire and grazing regimes. In general, this state is resilient to grazing, however, heavy grazing pressure could influence species composition in localized areas. This state is believed to be resilient to fire since most tree and shrub species in this state are capable of re-sprouting from crowns or roots following fire; however, further study of fire dynamics is needed. The herbaceous layer has been significantly altered and is predominantly non-native species such as smooth brome (Bromus inermis), quackgrass (Elymus repens), and Kentucky bluegrass (Poa pratensis).
Submodel
Description
The Herbaceous Understory State (2) consists of one community phase. The dynamics of this state are driven by fire and long-term improper grazing management practices. It is characterized by a shrub dominated community with little or no tree regeneration. Once the stand has transitioned to a shrub-dominated state, reestablishment of tree cover may be a very difficult and lengthy process.
Submodel
Description
The Herbaceous Understory State (4) occurs when the shrub understory has been removed due to long-term improper grazing practices. The overstory typically consists of a mature, open stand green ash and American elm. 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 stand has transitioned from a shrub-dominated understory to an herbaceous dominated understory, returning it to its former state is very difficult (Hansen et al., 1995).
Submodel
Mechanism
Introduction of non-native grass 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
A stand replacing fire in combination with improper grazing practices weaken the resilience of the Contemporary Reference State (2) and drive its transition to the Shrub Dominated State (3). The Contemporary Reference State (2) transitions to the Shrub Dominated State (3) when post-fire tree reproduction becomes rare and shrubs dominate the stand.
Mechanism
Prolonged improper grazing practices weaken the resilience of the Contemporary Reference State (2) and drive its transition to the Herbaceous Understory State (4). The Contemporary Reference State (2) transitions to the Herbaceous Understory State (2) when shrub reproduction becomes rare and the stand becomes open and decadent.
Mechanism
A change in management alone may not be sufficient to restore the Shrub Dominated State (3) to the Contemporary Reference State (2). Tree/shrub planting, normal or above-normal moisture, and proper grazing management can transition the Shrub Dominated State (3) back to the Contemporary Reference State (2). 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
A change in management alone may not be sufficient to restore the Herbaceous Understory State (4) to the Contemporary Reference State (2). Tree/shrub planting, normal or above-normal moisture, and proper grazing management can transition the Herbaceous Understory State (4) back to the Contemporary Reference State (2). These restoration methods are labor intensive and costly and may not be a practical in all situations.
Relevant conservation practices
| Practice | External resources |
|---|---|
|
Tree/Shrub Establishment |
|
|
Prescribed Grazing |
|
|
Herbaceous Weed Control |
Model keys
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