Swale

Description

The reference state contains plant communities presumed to occur prior to the introduction of nonnative plants, livestock grazing, and other modern disturbances. Basin big sagebrush dominance depends on time since fire, insect outbreak or extended drought. In both communities the grasses are the dominant component.

It is a very diverse community with 10-20 or more species present throughout the site. This diversity adds to a site’s stability. Often, decreasing diversity can be one of the first indicators of site deterioration. Key species that indicate a pristine and functioning system include. Species that often act as increasers with disturbance and indicate a deteriorating site include: basin big sagebrush, white sagebrush, squirreltail, foxtail barley, broom snakeweed, and rabbitbrush. This site has less than 20% big sagebrush canopy cover. The percentage of shrubs in this state will fluctuate depending on frequency and intensity of disturbances such as fire, or grazing. Typically the sage brush increases until fire is introduced to the system. Following the fire, rabbitbrush and annual forbs will increase creating a rabbitbrush phase that will be phased out as perennial grasses and sagebrush reestablish themselves

Grazing distribution on adjacent sites may be a problem since grazing animals are attracted to this site due to early green-up. Such continuous, heavy grazing pressure, as well as trampling damage on wet soils, may lead to deterioration of the potential plant community. The result is a decrease in western wheatgrass, spike muhly, muttongrass, prairie junegrass, and fourwing saltbush. Plant species that increase include blue grama, mat muhly, basin big sagebrush, rubber rabbitbrush, and broom snakeweed. Serious deterioration is represented by a sodbound cover of blue grama or total dominance by basin big sagebrush, both in low in production.

Submodel

Description

The current potential state is similar to the reference state, however invasive species are present in all community phases. This state is generally dominated by big sagebrush, however depending on disturbance history, native grasses, forbs, or other shrubs may dominate the site. Primary disturbance mechanisms include fire, native herbivore grazing, insect outbreak, domestic livestock grazing and surface disturbances, (i.e. road and pipeline development and off road vehicle (OHV) use). Timing of these disturbances dictates the ecological dynamics that occur. The current potential state is self-sustaining; but is losing resistance to change due to lower resistance to disturbances and lower resilience following disturbances. When disturbances occur, the rate of recovery is variable depending on severity. The current potential state is similar in structure and function to the reference state, however invasive and non-natives species are present in all community phases. The current potential state is generally dominated by perennial grasses.

Submodel

Description

This is a degraded state and the hydrology of this site has been altered. The plant community and surface debris are no longer capable of slowing runoff and dissipating the water’s erosive energy. In flow events, fine organic materials are not present to stabilize soil, slow water and allow infiltration. Instead, water from the uplands builds energy as it collects in the bottom and begins to form a channel. As the water becomes more channelized, the bottom becomes even less capable of dissipating the energy and channelization increases moving down the system and a head-cut start moving up the system.

This state has two fluctuating phases. Both phases have an entrenched channel where water has no access to the bottom floodplain and although vegetation in the channel may return to a community similar to the current potential (if not a little wetter), the majority of the bottom remains in the degraded sagebrush dominated state producing only a fraction of its original potential. The first community is the least stable with high levels of erosion occurring with any flow event. There is no vegetation on the sidewalls or the bottom of the channel. It has a distinctly V shaped channel profile that widens and deepens with every flow event. The second community is where healing is occurring and he bottom of the channel has become re-vegetated. The vegetation is similar to that of the current potential community with some exception. Since there is the same amount of water consolidated to a smaller area, the soils have a greater potential to show gleying and redoximorphic features that indicate low oxygen environments that are associated with the presence of a water table. Thus, plants that often inhabit the channel are those that have a greater tolerance for flooding. This means that often the amount of obligate and facultative wetland species are increased beyond that of the reference plant community. The channel vegetation helps to hold the channel in minor to moderate flooding events and prevent further degradation. Often sites in this phase develop U shaped profiles.

Submodel

Description

This is a degraded state and the hydrology of this site has been altered. The plant community and surface debris are no longer capable of slowing runoff and dissipating the water’s erosive energy. In flow events, fine organic materials are not present to stabilize soil, slow water and allow infiltration. Instead, water from the uplands builds energy as it collects in the bottom and begins to form a channel. As the water becomes more channelized, the bottom becomes even less capable of dissipating the energy and channelization increases moving down the system and a head-cut start moving up the system.

This state has two fluctuating phases. Both phases have an entrenched channel where water has no access to the bottom floodplain and although vegetation in the channel may return to a community similar to the current potential (if not a little wetter), the majority of the bottom remains in the degraded sagebrush dominated state producing only a fraction of its original potential. The first community is the least stable with high levels of erosion occurring with any flow event. There is no vegetation on the sidewalls or the bottom of the channel. It has a distinctly V shaped channel profile that widens and deepens with every flow event. The second community is where healing is occurring and he bottom of the channel has become re-vegetated. The vegetation is similar to that of the current potential community with some exception. Since there is the same amount of water consolidated to a smaller area, the soils have a greater potential to show gleying and redoximorphic features that indicate low oxygen environments that are associated with the presence of a water table. Thus, plants that often inhabit the channel are those that have a greater tolerance for flooding. This means that often the amount of obligate and facultative wetland species are increased beyond that of the reference plant community. The channel vegetation helps to hold the channel in minor to moderate flooding events and prevent further degradation. Often sites in this phase develop U shaped profiles.

Submodel

Description

This community is a man-made community. To get to this state requires a lot of inputs and hard work, but it can be done. Time, energy and resources are needed to restore the water table to the floor of the bottom and not the bottom of the channel.

Submodel