LOAMY BOTTOM 10-14 P.Z.
Scenario model
Current ecosystem state
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Management practices/drivers
Select a transition or restoration pathway
- Transition A More details
- Transition A More details
- Restoration pathway A More details
- Restoration pathway B More details
- Transition A 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 1.0 is a representative of the natural range of variability under pristine conditions. The Reference State has three general community phases; a shrub-grass dominant phase, a perennial grass dominant phase and a shrub dominant phase. State dynamics are maintained by interactions between climatic patterns and disturbance regimes. Negative feedbacks enhance ecosystem resilience and contribute to the stability of the state. These include the presence of all structural and functional groups, low fine fuel loads, and retention of organic matter and nutrients. Plant community phase changes are primarily driven by fire, periodic drought and/or insect or disease attack. Management should focus on maintaining high species diversity to promote site resiliency and a healthy watershed.
Submodel
Description
This state is similar to the Reference State 1.0 with three similar community phases. Ecological function has not changed, however the resiliency of the state has been reduced by the presence of invasive weeds. Non-natives may increase in abundance but will not become dominant within this State. These non-natives can be highly flammable and can promote fire where historically fire had been infrequent. Negative feedbacks enhance ecosystem resilience and contribute to the stability of the state. These feedbacks include the presence of all structural and functional groups, low fine fuel loads, and retention of organic matter and nutrients. Positive feedbacks decrease ecosystem resilience and stability of the state. These include the non-natives’ high seed output, persistent seed bank, rapid growth rate, ability to cross pollinate, and adaptations for seed dispersal. Management would be to maintain high diversity of desired species to promote organic matter inputs and prevent the dispersal and seed production of the non-native invasive species.
Submodel
Description
This state has two community phases a decadent shrub phase and a sprouting shrub phase. This state is a product of many years of heavy grazing during time periods harmful to perennial bunchgrasses and/or hydrologic modification resulting in a lowered water table. Nevada bluegrass may become the dominant grass. Sagebrush dominates the overstory and rabbitbrush may be a significant component. Sagebrush cover exceeds site concept and may be decadent, reflecting stand maturity. The shrub overstory dominate site resources such that soil water, nutrient capture, nutrient cycling and soil organic matter are temporally and spatially redistributed.
Submodel
Description
This state has two community phases one that is characterized by the dominance of seeded introduced species and the other with shrubs dominating the overstory. Forage kochia and other desired seeded species including basin big sagebrush and native and non-native forbs may be present.
Submodel
Description
The Annual State is likely possible on this site, however it was not observed during field work. Johanson (2011) documented the presence of an Annual State within the Utah portion of MLRA 28A for the Loamy Bottom ecological site (R028AY006UT). Cheatgrass was found to be the dominant species along with a diverse selection of invasive forbs including Russian thistle, knapweed and various non-native thistles. State resiliency is maintained through increased fire frequency and efficient utilization of soil nitrogen (Johanson 2011). This state has two plant community phases one that is characterized by an overstory of big sagebrush and an understory dominated by cheatgrass and the other a post-fire community dominated by cheatgrass with a trace amount of shrubs. Targeted grazing could be used to reduce the annual grasses species. Range seeding may also be needed.
Submodel
Mechanism
Trigger: This transition is caused by the introduction of non-native annual and perennial plants, such as cheatgrass, mustards, and whitetop (Cardaria draba).
Slow variables: Over time the non-native species will increase within the community.
Threshold: Any amount of introduced non-native species causes an immediate decrease in the resilience of the site. Non-native species cannot be easily removed from the system and have the potential to significantly alter disturbance regimes from their historic range of variation.
Mechanism
Trigger: To Community Phase 3.1: Repeated, heavy, growing season grazing will decrease or eliminate deep rooted perennial bunchgrasses, increase Sandberg bluegrass and favor shrub growth and establishment. Alteration in the hydrology of the site may also cause an increase in sagebrush; with gullying of associated channel the water table is dropped and may cause a decrease in perennial bunchgrasses. To Community Phase 3.2: Severe fire will remove sagebrush overstory, decrease perennial bunchgrasses and enhance Sandberg bluegrass.
Slow variables: Long term decrease in deep-rooted perennial grass density.
Threshold: Loss of deep-rooted perennial bunchgrasses changes nutrient cycling, nutrient redistribution, and reduces soil organic matter.
Mechanism
Brush management such as mowing, coupled with seeding of basin wildrye. May be coupled with restoration of the water table where channel incision has occurred. Engineered structures are recommended. See USDA, NRCS National Engineering Handbook (2008).
Relevant conservation practices
| Practice | External resources |
|---|---|
|
Brush Management |
|
|
Range Planting |
Mechanism
Brush management such as mowing, coupled with seeding of deep rooted non-native bunchgrasses.
Mechanism
Trigger: To Community Phase 5.1: Repeated, heavy, growing season grazing will decrease or eliminate deep rooted perennial bunchgrasses, increase cheatgrass and non-native forbs and favor shrub growth and establishment. Alteration in the hydrology of the site may also cause an increase in sagebrush; with gullying of associated channel the water table is dropped and may cause a decrease in perennial bunchgrasses. To Community Phase 5.2: Severe fire will remove sagebrush overstory and cheatgrass will be the dominate plant species. Rabbitbrush may be present. Failed brush management and seeding will also result in Community Phase 5.2.
Slow variables: Long term decrease in deep-rooted perennial grass density and increase in shrub overstory. Channel incisement may be occurring.
Threshold: Loss of deep-rooted perennial bunchgrasses changes nutrient cycling, nutrient redistribution, and reduces soil organic matter.
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.