Ecological dynamics
Plants that can tolerate soils which are saline and/or alkaline and have a water table near the surface for most of the growing season dominate the potential vegetation on this site. The expected potential composition for this site is about 80% grasses, 10% forbs and 10% woody plants. The composition and production will vary naturally due to historical use, fluctuating precipitation and fire frequency.
As this site deteriorates, species such as inland saltgrass and greasewood increase and species such as Russian olive, saltcedar, foxtail barley, and a host of weedy forbs invade the site. Grasses such as alkali sacaton, Nuttall’s alkaligrass, and basin wildrye will decrease in frequency and production.
The Historic Climax Plant Community (description follows the plant community diagram) has been determined by study of rangeland relic areas, or areas protected from excessive disturbance. Trends in plant communities going from heavily grazed areas to lightly grazed areas, seasonal use pastures, and historical accounts have also been used.
The following is a State and Transition Model Diagram that illustrates the common plant communities (states) that can occur on the site and the transitions between these communities. The ecological processes will be discussed in more detail in the plant community narratives following the diagram.
State 1
Alkali Sacaton/Nuttall’s Alkaligrass Plant Community
Community 1.1
Alkali Sacaton/Nuttall’s Alkaligrass Plant Community
The interpretive plant community for this site is the Historic Climax Plant Community. This state evolved with grazing by large herbivores, periodic fires, supplemental moisture, and saline and/or alkali soils. Potential vegetation is about 80% grasses or grass-like plants, 10% forbs and 10% woody plants. The major grasses include alkali sacaton, Nuttall’s alkaligrass, and basin wildrye. Grasses/grasslikes of lesser importance are Baltic rush, alkali bluegrass, western wheatgrass, alkali cordgrass and inland saltgrass. Woody plants are primarily rubber rabbitbrush and greasewood. A variety of forbs also occurs in this state and plant diversity is high (see Plant Composition Table).
The total annual production (air-dry weight) of this state is about 2400 pounds per acre, but it can range from about 1800 lbs. /acre in unfavorable years to about 2600 lbs. /acre in above average years.
The state is stable and well adapted to the Northern Plains climatic conditions. The diversity in plant species and the reliable water table, allow for high drought resistance. This is a sustainable plant community (site/soil stability, watershed function, and biologic integrity).
Transitions or pathways leading to other plant communities are as follows:
• Moderate, continuous season-long grazing will convert this plant community to the Alkali Sacaton/Inland Saltgrass/Mixed Shrub Plant Community. Prolonged drought will exacerbate this transition.
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State 2
Alkali Sacaton/Inland Saltgrass/Mixed Shrub Plant Community
Community 2.1
Alkali Sacaton/Inland Saltgrass/Mixed Shrub Plant Community
Historically, this plant community evolved under moderate grazing by domestic livestock and low fire frequency. Currently, this site is normally found under a moderate, season-long grazing regime and in the absence of fire or brush control. Prolonged drought can also play an important role and will exacerbate these conditions. Saline and flood tolerant perennial plants make up the dominant species in this plant community.
Dominant grasses/grasslikes include alkali sacaton, inland saltgrass, western wheatgrass, alkali cordgrass, and Baltic rush. Forbs commonly found in this plant community include alkali seepweed, silverweed, American licorice, seaside arrowgrass, and smooth horsetail. Greasewood and rubber rabbitbrush comprises the majority of the woody species and make up less than 25% of the annual production.
When compared to the Historical Climax Plant Community, basin Wildrye and Nuttall’s alkaligrass have decreased. Inland saltgrass, forbs, greasewood, and rubber rabbitbrush have increased. Annual herbaceous weedy plants have increased, but occur in small patches. Invasion of saltcedar or Russian olive should be considered serious and should be controlled.
The total annual production (air-dry weight) of this state is about 2000 pounds per acre, but it can range from about 1500 lbs. /acre in unfavorable years to about 2500 lbs. /acre in above average years.
This state is stable and protected from excessive erosion. The herbaceous component is mostly intact and plant vigor and replacement capabilities are sufficient. Only minimal occurrences of water flow patterns and litter movement is evident. Incidence of pedestalling is minimal. Soils are mostly stable and the surface shows minimum soil loss. The watershed is functioning and the biotic community is intact.
Transitional pathways leading to other plant communities are as follows:
• Prescribed grazing and possible long-term prescribed grazing will result in a plant community very similar to the Historic Climax Plant Community, except that greasewood will persist without a return to a normal fire regime or some form of brush control.
• Frequent and severe grazing plus no encroachment plus no fire will convert this plant community to the Inland Saltgrass Sod/Mixed Shrub Plant Community.
• Encroachment and no fire will convert this plant community to the Alkali Sacaton/ Saltcedar and/or Russian Olive Plant Community.
• Frequent and Severe grazing plus encroachment will convert this plant community to a Dense Saltcedar and/or Russian Olive Stand Plant Community.
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State 3
Inland Saltgrass Sod/Mixed Shrub Plant Community
Community 3.1
Inland Saltgrass Sod/Mixed Shrub Plant Community
This plant community is the result of frequent and severe grazing with periodic overflows and no fire or brush control. This plant community is dominated by a dense short grass sod and includes a mosaic shrub overstory. Shrubs comprise less than 35% of the annual production, and are kept in check by the herbaceous sod understory.
The dominant grasses are inland saltgrass and mat muhly. Forbs such as seaside arrowgrass, licorice root, curly dock, and smooth horsetail are common. Greasewood and rubber rabbitbrush are the primary overstory species in this plant community. Noxious weeds such as saltcedar, Russian olive, Russian knapweed and Canada thistle invade the site, especially if a seed source is available. Plant diversity is moderate to poor.
When compared to the Historic Climax Plant Community, the tall and medium grasses are significantly reduced or absent. Short grasses are dominant and weedy annuals are common. Shrubs have increased as a percentage of the total production, but will not dominate since the sod prevents a homogeneous shrub cover. Areas of bare ground may have increased in patches and total production has decreased as the short grasses have replaced the tall and mid grasses.
The total annual production (air-dry weight) of this state is about 1200 pounds per acre, but it can range from about 800 lbs. /acre in unfavorable years to about 1600 lbs. /acre in above average years.
The sod component of this plant community is extremely resistant to change and continued frequent and severe grazing or the removal of grazing does not seem to affect the plant composition or structure of the plant community. The biotic integrity of this state is generally not functional as plant diversity is poor, especially the amount of herbaceous species. The vegetative structure has shifted as the shrubs and short grasses now occupy the majority of the site.
This sod bound plant community is very resistant to water infiltration. While this sod protects the site itself, excessive runoff increases erosion on bare ground and can cause rill channels and gully erosion. Water flow patterns are obvious in the bare ground areas and shrubs and sod patches are pedestalled. Rill channels are noticeable in the interspaces and gullies may be establishing where rills have concentrated. The watershed may not be functioning, as runoff is excessive and erosional processes are accelerated.
Transitional pathways leading to other plant communities are as follows:
• Grazing land mechanical treatment (chiseling, etc.) and brush management followed by prescribed grazing and, if necessary seeding will return this plant community to near Historic Climax Plant Community.
• Frequent and severe grazing plus encroachment will convert this plant community to the Dense Saltcedar and/or Russian Olive Stand Plant Community. Prolonged drought will exacerbate this transition. Invasion of saltcedar or Russian olive should be considered serious and should be controlled.
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State 4
Alkali Sacaton/Saltcedar and/or Russian Olive Plant Community
Community 4.1
Alkali Sacaton/Saltcedar and/or Russian Olive Plant Community
This plant community occurs where saltcedar and/or Russian olive encroaches into a saline subirrigated site and becomes established. This occurs with or without grazing and is the result of conditions conducive to the colonization of these plants. Increase in bare ground is likely to increase the potential for colonization. However, areas that have been deferred or removed from grazing and had a healthy stand of alkali sacaton can be infested. Saline and flood tolerant perennial plants make up the dominant understory species in this plant community.
Dominant grasses include alkali sacaton, inland saltgrass, western wheatgrass, alkali cordgrass, and Baltic rush. Forbs commonly found in this plant community include alkali seepweed, silverweed, American licorice, seaside arrowgrass, and smooth horsetail. Saltcedar and/or Russian olive comprise the majority of the woody species and make up less than 35% of the annual production. Invasion of saltcedar or Russian olive should be considered serious and should be controlled.
When compared to the Historical Climax Plant Community, alkali sacaton, basin wildrye and Nuttall’s alkaligrass have decreased. Inland saltgrass and forbs have increased. Saltcedar and Russian olive have invaded. Total production is similar to the Alkali Sacaton/Mixed Shrub plant community.
The total annual production (air-dry weight) of this state is about 1200 pounds per acre, but it can range from about 800 lbs. /acre in unfavorable years to about 1800 lbs. /acre in above average years.
This plant community is mostly resistant to change, but species composition can be altered through long-term overgrazing and further encroachment of saltcedar and Russian olive. The herbaceous component is stable and plant vigor and replacement capabilities are sufficient. The biotic community is not intact due to the encroachment of these invasive species. Plant diversity is moderate.
Soils are mostly stabilized. Only minimal occurrences of water flow patterns and litter movement is evident. Incidence of pedestalling is minimal. Soils are mostly stable and the surface shows minimum soil loss. The watershed may or may not be functional.
Transitions or pathways leading to other plant communities are as follows:
• Frequent and severe grazing plus Encroachment and no fire will convert the plant community to the Dense Saltcedar and/or Russian Olive Stand Plant Community.
• Recovery to near Historic Climax Plant Community condition is impractical and suppression or containment of these two species is optimal. Any methods of control should be followed by revegetation to reduce regeneration of these two species and other weedy plants.
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State 5
Dense Saltcedar and/or Russian Olive Stand Plant Community
Community 5.1
Dense Saltcedar and/or Russian Olive Stand Plant Community
This plant community evolved under frequent and severe grazing with the absence of fire and encroachment of saltcedar and/or Russian olive. Saltcedar and/or Russian olive dominate this plant community. Most of the tall and medium grasses are eliminated and an understory of weedy herbaceous plants is prevalent. The interspaces between woody plants have expanded leaving more soil surface exposed to erosive elements or invaders.
The weedy plants, such as foxtail barley, curly dock, kochia, halogeton, swainsonpea, Russian knapweed, and Russian thistle, make up the dominant understory. Total annual production is mostly from shrubs and these weedy plants. Saltcedar and/or Russian olive make up greater than 35% of the total annual production. When compared with the HCPC, the annual production is less due to the removal of the perennial grass and amount of bare ground. The increase in woody species, however, compensates for some of this loss.
The total annual production (air-dry weight) of this state is about 1200 pounds per acre, but it can range from about 800 lbs. /acre in unfavorable years to about 1600 lbs. /acre in above average years.
This plant community is resistant to change as the stand becomes denser. These areas may actually be more resistant to fire as less fine fuels are available and the bare ground between the shrubs has increased. Continued frequent and severe grazing or the removal of grazing does not seem to affect the plant composition or structure of the plant community. Saltcedar, Russian olive, annual grasses, weedy species and bare ground compromise the biotic integrity. Plant diversity is poor and the potential for native grasses to reproduce is absent. The shift in the vegetative structure and function is extreme and the biotic integrity is lost.
The soil of this state is not protected as erosion has accelerated because of increased bare ground. Water flow patterns and pedestalling are obvious. Infiltration is reduced and runoff is increased. Rill channels may be noticeable in the interspaces and gullies may be establishing where rills have concentrated. The watershed is not functional due to excessive runoff, erosion and bare ground.
Transitional pathways leading to other plant communities are as follows:
• Brush management and prescribed grazing will result in an Alkali Sacaton/ Saltcedar and/or Russian Olive Plant Community.
• Recovery to near Historic Climax Plant Community condition is impractical and suppression or containment of saltcedar and Russian olive is needed. Any methods of control should be followed by revegetation to reduce regeneration of these two species.
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