Ecological dynamics
This site is based on the range site Foothill Swale - R048XY245CO/R034XY285CO) from August 1975. (SCS, 1975). This original site concept was written for the two MLRAs 48A (mountainous ares of Colorado) and 34A in the Piceance Basin. This ecological site is described and data was collected primarily in the Piceance basin with an Aridic Ustic soil moisture phase and frigid temperature regime. This ecological site is located in draws, small valley bottoms and drainage-ways in Piceance Basin. Herbivory and fire are the dominant disturbance factors in the sagebrush biome (Boyd et. al., 2014). Removal or repeatedly detrimental application of either of these disturbances on the system and/or the landscape can result in a shift of the ecological dynamics of this system. The ecological dynamics of the associated uplands are influential to the dynamics of this site. Excessive runoff and erosion from degraded uplands can increase concentrated flow and increased potential erosion towards gully formation. This site is located in the bottoms where fire occurred more frequently, removing brush and keeping it in a grassland state.
The plant community on this site is very productive and relatively resilient compared to its surrounding uplands. It has deep soils with good water holding capacity that receive a large amount of moisture from run-in and overflow water. Because of these factors many of these sites are now or once were cleared and converted to agricultural lands depending on their accessibility.
This site is dominated by perennial grasses but shrub species are present with Basin Big Sagebrush being the most abundant Although this site evolved with grazing and is relatively durable, it will be affected negatively with continuous heavy grazing pressure. Livestock are attracted to these sites because they are so productive and these sites lie in low areas with gentle slopes. Proper distribution of livestock is critical. Appropriate placement of fencing, water, and salt/supplement is necessary. Heavy grazing combined with drought and/or lack of fire, will cause this site to become shrub dominant. As shrubs increase and perennials are weakened due to heavy grazing and/or drought, undesirable annuals such as cheatgrass may invade the site.
As perennial grasses with fibrous root systems are replaced by weaker annuals, erosion may occur more rapidly. Runoff from the uplands can cause channels to form and incise dropping the water table. As soils dry out, greasewood may begin to invade into these sites. This seems to occur more frequently at lower elevations.
A Greasewood state occurs in the similar foothill swale ecological site in MLRA 34B where the temperature regime is mesic and not frigid. The 2 foothill swale sites have not been broken out in published soil survey and this will be need to be done in the future. Greasewood invades and can eventually dominate foothill swale sites when adjacent to salty ecological sites when dewatered. This typically occurs in the lower ends of the drainages, possibly because of salt accumulations from upstream or salt layers that are exposed through erosion and where the landscape has transitioned to mesic temperature regime.
Soils, topographic location, climate, periodic droughts and fire influenced the stabilization of the Reference State on this site as was the case on most high mountain valley ecological sites. The Reference State is presumed to be as found by European settlers in the early 1800's developed under the prevailing climate over time along with the soils in their topographic location. Grazing and/or browsing by wildlife influenced the plant community as well. The resulting plant community was a cool season bunchgrass/shrub community. Sagebrush below 8500 feet has been slower to recover from settlement of the west (Winward, 2004). This site has been found to have basin big sagebrush.
Natural fire played an important role in the function of most high mountain valley sites, especially the sagebrush communities. Grasses such as needlegrasses and blue grasses were dependent upon fire to stimulate them. Fire also kept sagebrush stands from getting too dense, while invigorating other sprouting shrubs. Fire helped to keep a balance between the grasses, forbs and shrubs. Plant community dynamics were improved by opening up canopies and stimulating forb growth creating a mosaic of different age classes and species composition. Other than Wyoming big sagebrush, the deep rooted species that grow on the site are not easily damaged by fire (BLM, 2002). Shrubs which re-sprout (yellow rabbitbrush, rubber rabbitbrush), are suppressed for a time allowing grasses to dominate. If periodic fire or some other method of brush control is not used, then sagebrush will slowly increase and can begin to dominate the site.
Fire size prior to 1850 were most likely a large number of small to medium size mosaic burns and since 1980 can be typified by a few very large fires due to human caused changes (Evers, et al, 2011). This change in fire return intervals and intensities was cause by fire suppression and reduced fine-fuels from livestock grazing practices around the late 1800’s and early 1900’s. Since fire is not always available to be applied, then other shrub management may necessary from time to time to help keep the community in balance. Treatment response will vary among sites due to differences in vegetation composition and abundance, soils, elevation, aspect, slope and climate (McIver, et al, 2010).
There has been shrub die-off in several sagebrush taxa in the past 10-15 years due to several factors. The two dominant factors are disease/pathogens and drought. Die-off due to disease/pathogens is believed to be tied to disease or stem/root pathogens occurring in dense over-mature sagebrush stands throughout the west. While in some areas, when the factors of drought and heavy browsing occurring in conjunction with disease/pathogens complete areas are dying.
Small wet areas can occur occasionally when the bottoms are very narrow and small, allowing for more water accumulation. This may support willows, sedges and rushes and may be a small inclusion of a mountain meadow or swale meadow ecological site. Narrowleaf cottonwoods can occasionally be found in these inclusion areas. Narrowleaf cottonwood are reported to be a facultative wetland species which are tolerant of frequent and prolonged flooding and are not drought resistant (Simonin, 2001). This site is typically too dry to sustain cottonwoods.
A weedy community that has not been depicted on the model can arise if domestic grazing is completely excluded or if there is repetitive, season-long, heavy domestic or wild ungulate use. With grazing exclusion, a thick thatch of residual litter build-up results in shading and a reduction of health, vigor and production of all plants. Improper domestic and wild ungulate grazing use results in preferred species being repeatedly clipped which decreases their health, vigor and production. Both make a site susceptible to invasion by noxious and/ unsuited species.
Variability in climate, soils and aspect and complex biological processes will cause the plant communities to differ. Fluctuations in species composition and relative production may change from year to year depending upon precipitation and other climatic factors. The species lists provided within this document are not a complete list of all occurring or potentially occurring species on this site. These species lists are not intended to cover the full range of conditions, species and responses of the site. The State & Transition model depicted for this site is based on available research, field observations and interpretations by experts and could change as knowledge increases. This is the interpretive plant community and is considered to be the Reference State. This plant community evolved with grazing, fire, and other disturbances such as drought. This site is well suited for grazing by domestic livestock and wildlife and can be found on areas that are properly managed prescribed grazing.
State 1
Reference State
This state consists of two major plant communities, 1) Basin Wildrye with low Basin big sagebrush shrub cover and 2) Wheatgrasses/Basin Wildrye with basin big sagebrush. In community 1.1, the grasses are the dominant component. In community 1.2, grasses may be dominant or co-dominant with basin big sagebrush.
Community 1.1
Basin Wildrye
Figure 7. Basin Wildrye Community
This plant community is dominated by cool season grasses with shrub species being a minor component. Probable vegetation for this state is estimated to be 70-75% grass and grasslike plants, 5-10% forbs, and 10-20% shrubs. The dominant grass found on this site is basin wildrye. The subdominant grasses are western and thickspike wheatgrass. Other common grasses found on this site are wheatgrass, needle and thread and sandberg bluegrass. Sand dropseed is the lone warm season grass that has been infrequently observed on this site (take out and mention when present have changes to 34B site). Principal forbs are yarrow, fleabane, globemallow, phlox, Louisiana sagewort, and wild buckwheat. The dominant shrub found on this site is basin big sagebrush with rabbitbrush species being subdominant.
A typical plant composition based on air-dry weight for this state consists of 40-55% basin wildrye, 15-45% rhizomatous wheatgrasses, 0-5% , Sandburg bluegrass, 0-5% needle and thread. 15-20% makeup the other grasses. Scarlet globemallow, and western yarrow make up around 0-3% of the annual forb production. Shrubs consist of 10-15% basin big sagebrush, 5-10% other woody species.
The total annual production (air-dry weight) of this state is around 2000 lbs. per acre but it can range from around 1000 lbs. on unfavorable years to over 3000 lbs. in years when there is high precipitation that falls during the growing season.
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/weedy state that will be phased out as perennial grasses and sagebrush reestablish themselves.
In a normal year, this site, is capable of producing 2000 to 3000 pounds per acre annually and is a very diverse community with 15-20 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, fleabane, herbaceous cinquefoil, bottlebrush squirreltail, foxtail barley, and rabbitbrush. This site has less than 15% big sagebrush canopy cover.
Table 5. Annual production by plant type
| Plant type |
Low
(kg/hectare) |
Representative value
(kg/hectare) |
High
(kg/hectare) |
| Grass/Grasslike |
785 |
1681 |
2578 |
| Shrub/Vine |
224 |
336 |
448 |
| Forb |
112 |
224 |
336 |
| Total |
1121 |
2241 |
3362 |
Table 6. Soil surface cover
| Tree basal cover |
0%
|
| Shrub/vine/liana basal cover |
5-8%
|
| Grass/grasslike basal cover |
55-65%
|
| Forb basal cover |
1-3%
|
| Non-vascular plants |
0%
|
| Biological crusts |
0%
|
| Litter |
60-70%
|
| Surface fragments >0.25" and <=3" |
0%
|
| Surface fragments >3" |
0%
|
| Bedrock |
0%
|
| Water |
0%
|
| Bare ground |
5-10%
|
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Community 1.2
Grasses/Sagebrush Co-dominated
Figure 10. Wheatgrass Plant Community
This state occurs when there are low frequencies of fire coupled with heavy grazing, and/or drought. The rabbitbrush increases due to the disturbance and decrease of competition from the grasses and then is phased out by basin big sage brush. The basin big sagebrush continues to increase as perennial grasses are weakened by drought or improper grazing. The grasses remain dominant, however their composition does change. Streambank wheatgrass increases to become dominant or co-dominant with basin wildrye. Streambank wheatgrass is more tolerant to grazing than basin wildrye which has elevated growing points. If grazed consistently heavy in the spring and early summer when basin wildrye is palatable, it will decline. Streambank wheatgrass can handle periodic flooding as well as drought conditions fairly well. This state is moderately stable, although susceptible to erosion due to the increase of bare ground under and around sagebrush canopy. If fire is not introduced to this system it may begin to cross a threshold to a sagebrush dominated state. During this phase Kentucky bluegrass and small amounts of cheatgrass and lambsquarters may begin to invade the site.
The plant community evolved under continuous grazing by domestic livestock. This community is a reflection of a disturbance. It is dominated by wheatgrasses, often western wheatgrass, which can be greater than 50% of this community phase’s herbaceous (grass and forb) production. The diversity of this phase is limited with the vast majority of the production coming from only 4 to 5 species.
The state is moderately stable and somewhat vulnerable to erosion due to more bareground between the plants. The biotic integrity of this plant community is usually intact. The watershed is usually functioning. However, it can become at risk when canopy cover of big sagebrush and/or bare ground increases.
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Pathway 1.1A
Community 1.1 to 1.2
Grasses/Sagebrush Co-dominated
Lack of disturbances, lack of fire, insect and pathogen outbreaks, and improper grazing use by both wildlife and domestic grazers can cause this community to shift to a less diverse community dominated by wheatgrasses and basin big sagebrush. Cool season bunchgrasses such as basin wildrye will decrease in frequency and production with improper grazing.
Pathway 1.2A
Community 1.2 to 1.1
Grasses/Sagebrush Co-dominated
Proper grazing use, fire, wet climatic cycles, insect or pathogen outbreaks, and/or vegetation treatments should allow this sagebrush dominated community to transition to the more diverse Basin Wildrye plant community. Brush management practices may be necessary if the sagebrush and bareground has increased. Care should be taken when planning brush management practices to consider wildlife habitat and edge values.
State 2
Basin Big Sagebrush Dominated Swale
This state occurs when there are low frequencies of fire coupled with heavy grazing, and/or drought. The rabbit brush increases due to the disturbance and decrease of competition from the grasses and then is phased out by basin big sagebrush. The basin big sagebrush continues to increase as perennial grasses are weakened by drought or improper grazing. The grasses remain dominant, however their composition does change. Streambank wheatgrass increases to become dominant or co-dominant with basin wildrye. Streambank wheatgrass is more tolerant to grazing than basin wildrye which has elevated growing points. If grazed consistently heavy in the spring and early summer when basin wildrye is palatable, it will decline. Streambank wheatgrass can handle periodic flooding as well as drought conditions fairly well. This state is moderately stable, although susceptible to erosion due to the increase of bare ground under and around sagebrush canopy.
The plant composition of this state is 50-65% perennial grasses, 5-10% forbs and 20-35% shrubs. The annual production drops to around 1500 pounds an acre in an average year. If fire is not introduced to this system it may begin to cross a threshold to a sagebrush dominated state. During this phase Kentucky bluegrass and small amounts of cheatgrass and lambsquarters may begin to invade the site.
This state arises when there has been prolonged fire suppression along with heavy grazing and/or drought. Basin big sagebrush is now the dominant species contributing over 35% of the production of the site. Streambank wheatgrass and western wheatgrass are the major grasses in this scenario, along with sandberg bluegrass, bottlebrush squirreltail, and Indian ricegrass. These are all grasses that are favored as soils are drying. There is little to no basin wildrye left in this community. Kentucky bluegrass and cheatgrass may invade as native grasses are weakened due to heavy grazing and increased competition by basin big sagebrush.
The hydrology of the site is beginning to be altered as the water table lowers due to the lack of grasses. This state’s annual production may be around 800-1200 pounds an acre in an average year. If heavy grazing continues to occur shrubs will continue to increase and perennial grasses will begin to be replaced by annuals such as cheatgrass.
This state may return to the reference state through Prescribed fire or brush management by chemical or mechanical means followed by reseeding. A prescribed grazing plan should be applied which should include a deferment period of 2 to 3 years or more depending on the site to allow.
Rush, big sagebrush, fleabane, herbaceous cinquefoil, bottlebrush squirreltail, foxtail barley, equisetum - horsetail, and rabbitbrush have increase and become dominant plants in this state. The hydrologic function of this community is still intact throughout the entirety of the swale. Meaning, there is no bench or entrenched channel. The water has access to the entirety of the swale for flooding and energy dissipation purposes. This state is a very unstable state at the edge of a very major threshold and this would be the latest time to treat the site, with the least amount of energy, and expect to restore it to the reference plant community. Without treatment there is high probability of a transition to a greatly degraded state with a high flow event that could permanently alter the hydrologic function of the site.
Upland site degradation is a huge influence in allowing the progression of the transition from a site with functioning hydrology and preferred plant communities to this highly unstable community. Uplands that develop dense, aged sagebrush stands with little understory dewater a swale by increasing overland flow and evaporative loss and decreasing a site’s ability to capture and store water. The removal of grasses and herbaceous litter from the soil surface decreases the site’s ability to slow water and allow for infiltration. Thus, water that once could have been safely transported, infiltrated, stored and moved to the swale at a later period is now added to the already erosive overland flow at the same time. Meaning, larger amounts of water and sediment are running onto the swale more rapidly in a shorter period of time. These minor changes in the microclimate, especially on the periphery of the swale, are enough to allow for the sagebrush to continue advancing into the swale along with other obligate upland species and further perpetuating the drying.
Community 2.1
Basin Big Sagebrush Dominated Swale
Figure 12. Sagebrush Dominated Community
The total annual production from big sagebrush is 15-20% of the community phase total. Big sagebrush canopy cover will have increased to 35% or greater of the plant community. This community, like the reference plant community, is diverse often with 15-20 species. However, unlike the reference plant community, a larger proportion of the diversity comes from upland plants invading the drying swale. Species like bottlebrush squirreltail, Letterman's/pine needlegrass, muttongrass and upland sedges often indicate that the system is transitioning into a site with altered hydrologic function. Rush, only a minor component in other communities begins to increase in the sagebrush understory as the dominate species to greater than 10% of the annual production. This is due to the fact that rush plants tend to grow mainly in early spring when moisture is available and does not need sustained moisture throughout the growing season. Rush production greater than 10% should be an indicator to managers that closer evaluation and treatment may be needed.
Production is 1200 to 1600 pounds per acre. The dominate plants have changed from grasses to big sagebrush. There is a reduction of fine organic material to protect soil from erosion leading to organic matter depletion. Moderate and large flow events can result in immense amounts of erosion. A swale that was once a depositional zone prior to sagebrush invasion can become at risk for developing deeply eroded channels and contribute to higher stream sediment loads.
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State 3
Degraded Swale
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 swale and begins to form a channel. As the water becomes more channelized, the swale becomes even less capable of dissipating the energy and channelization increases moving down the system and a head-cut start moving up the system. The channel also begins to drain subterranean water, further dewatering the system in a self-perpetuating feedback loop. Soils in these areas may see drastically reduced A horizons (7” or less).
Due to the dewatering trend that has occurred in the sagebrush dominated swale State 2, production of this altered community is drastically reduced to 500-700 pounds per acre. Diversity is severely restricted to three or four different species with rush being one of the major components. The bare ground is also increased to 10-15%, or higher. With the lower water availability this allows greasewood to possible invaded in this state. More research is needed into the greasewood plant community in this area.
This state has two fluctuating phases. Both phases have an entrenched channel where water has no access to the swale floodplain and although vegetation in the channel may return to a community similar to the original reference state (if not a little wetter), the majority of the swale 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 reference community with some exception. Since there is the same amount of water consolidated to a smaller are, 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.
Community 3.1
Basin Big Sagebrush Dominated eroding Channel
This community is the least stable community within this state. This state has actively eroding channel with active head-cuts at the top of the eroding channel. There are high levels of erosion occurring with any flow event due to the lack of vegetation on the sidewalls and the bottom of the channel. Often there is a distinctly V shaped channel that widens and deepens with every flow event. Bareground has increased and herbaceous production has been reduced to 500-700 pounds per acre. The rush production has increased proportionally to greater than 10% of the sites total production. There is very low species diversity and a majority of the forbs are gone from the community. The site is eroding to create a partially abandoned swale that will look like a drier sagebrush bench above a narrower channel (swale).
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Community 3.2
Basin Big Sagebrush Dominated incised channel
This phase is where healing is occurring and he bottom of the channel has become re-vegetated. The vegetation is similar to that of the reference community with some exception. Since there is the same amount of water consolidated to a smaller are, 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.
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Pathway 3.1A
Community 3.1 to 3.2
By stabilizing actively eroding areas with vegetation and ground cover the swale can begin to heal and further deterioration can be reduced. Any practice that promotes vegetation will aid in this transition. possible mechanisms of transition are lack of fire, time without disturbance, extended, improper grazing, extended drought, lack of insect or pathogen outbreaks
Pathway 3.2A
Community 3.2 to 3.1
Possible mechanisms of transition are fire, proper grazing, wet climatic cycles, vegetative treatments, and/or small scale insect/ pathogen outbreaks
State 4
Rabbitbrush Dominated Swale
A system dominated by rabbitbrush is a system in which the vegetation has been removed by chemical treatment, physical means (mowing) or fire often in attempted to remove invading sagebrush. Rabbitbrush is a re-sprouter and will increase after disturbance.
Community 4.1
Rabbitbrush Dominated Swale
Rabbitbrush production is 15-20% of the annual production. Rabbitbrush is a re-sprouter that often vigorously sprouts after removal of the aboveground biomass. Although this is not a preferred state, it is often better than sagebrush dominated swale because the rabbitbrush does not restrict grass and forb production. However it can be difficult to move this community back to the reference plant community often taking several years of chemical treatment.
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State 5
Reclaimed Swale
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 swale and not the bottom of the channel.
Community 5.1
Reclaimed Swale
Figure 17. Recalimed Plant Community
This is the community phase after the work is done to restore the water table to the floor of the swale. Often a large amount of dirt work, brush removal and the installation of check dams are required to reclaim the swale community. Even then, the community may never be that of the reference plant community. Areas directly behind the check structures often have a higher water table and promote facultative and obligate wetland species. Areas directly below the structures are not getting the subterranean flow that was present in the original swale and thus are drier and promote invasion by upland species that are not typical in the reference plant community. This site will need to be monitored to see if additional work will need to be done once original check dams fill up with sediment. This site could need to be seeded to help stabilize it.
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State 6
Basin Big Sagebrush - Cheatgrass Swale
With Basin big sagebrush increasing and sagebrush decadence increasing, cover changes in this communities can brought on by prolonged drought, lack of fire, surface disturbances, (i.e. road and pipeline development and off road vehicle (OHV) use), and improper grazing use can create alterations in the plant community that can leave the soils at risk for erosion and alter the hydrological function. Improper grazing of perennial grasses during growth has favored non-native invasive species, primarily cheatgrass and/or Russian thistle, to co-dominate the understory. Few remnant plants may still persist under shrubs, but re-establishment and dominance by perennial grasses will not occur following a fire, or with the removal of grazing animals in the natural time frame.
Community 6.1
Basin Big Sagebrush - Cheatgrass Swale
Figure 19. Sagebrush - Cheatgrass Community
This state will occur following the Big Sagebrush/Streambank Wheatgrass state if it is heavily grazed. As perennial grasses disappear due to improper grazing and competition from basin big sagebrush, annual plants such as cheatgrass fill the void. As this happens the hydrology of the site is altered. There is accelerated erosion that can lead to increased channelization in flow areas. If channels continue to erode and become incised, the water table will drop farther and the site may then move into the Greasewood/cheatgrass state.
This state will consist mainly of basin big sagebrush with annuals and bare ground in the understory. The production for this state drops significantly to around 500 to 800 pounds per acre. To restore the site to the Reference state extreme inputs are necessary. There would most likely be a reclamation state that would have to occur in between this state and the Reference state. This would include erosion control structures, brush removal, and reseeding.
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Transition T1A
State 1 to 2
Sagebrush encroachment with increasing sagebrush decadence and cover in adjacent upland communities brought on by prolonged drought, lack of fire, and improper grazing use can create alterations in the plant community that can leave the soils at risk for erosion and alter the hydrological function. The mean fire return interval (FRI) is 12 -25 years for mesic habitats (Boyd et. al., 2014) Also, lack of wet periods to drown out Big sagebrush can cause this shift from State 1 - Reference State to State 2 - Basin Big Sagebrush Dominated Swale.
Restoration pathway R2A
State 2 to 1
State 1 can be restored from the sagebrush dominated swale through fire or some kind of sagebrush removal and proper grazing use by both domestic animal and wildlife use. Management practices that restore upland community health and functioning are critical to restoring a sagebrush dominated swale to the reference state as well as those done in the swale itself. Such practices can include prescribed fire and/or shrub management. This needs to be used in conjunction with proper grazing management. Several wet years in a row can also decrease big sagebrush, as big sagebrush does not like to have it roots in water for extended periods of time.
Transition T2A
State 2 to 3
This is a very quick transition. Due to the lack of soil protection large flow events quickly destabilize the site and it transitions to the state with altered hydrological function (3). Anything that further reduces ground cover, like improper grazing use and continued drought, has potential to quicken this transition. Fire suppression and lack of shrub management in decadent sagebrush uplands continue to promote altered hydrologic function and also aid in destabilizing the swale.
This community becomes unstable, affects soil health and the hydrologic function as it is invaded by big sagebrush. The lack of adequate herbaceous cover to dissipate water velocity and encourage infiltration result in the formation of gullies and head-cuts.
Transition T2B
State 2 to 4
Repetitive burning of big sagebrush favors rabbitbrush and perennial grasses, especially Basin wildrye. Mechanical and chemical removal of sagebrush can often release rabbitbrush on this site. This may be a timing of treatment issue or one related to the weather patterns in years surrounding the treatment.
Transition T2C
State 2 to 6
The introduction of annual grasses (cheatgrass) and forbs to the site.
Transition T3A
State 3 to 5
Returning to the reference state from either of the two communities phase in State 3 would be time, resource, and energy intensive. The water table needs to be restored to the floor of the swale and not the bottom of the channel. Often a large amount of dirt work, brush removal and the installation of check dams are required to reclaim the swale community. Check dam structures are used in an attempt to stop head-cuts, slow water, and catch sediments all in hopes of raising both the channel and the water table to allow for flooding access to the entire swale and returning the hydrologic function. Reclaiming these swale sites, also, include fixing all the problems that initially contribute to the degradation, including management practices that improve the contributing upland communities. A swale cannot be restored by only changing problems within the site itself. The swale’s health and success in restoring the functioning is directly tied the health and function of the surrounding uplands.
Restoration pathway R4B
State 4 to 1
Often the only way to transition from this state to a preferred functioning community (reference community) that is not dominated by sagebrush is by means of chemical treatment of the rabbitbrush. Repetitive treatment is often needed.
Restoration pathway R4A
State 4 to 2
Continued sagebrush encroachment from untreated uplands and improper grazing use can contribute to the transitioning of this rabbitbrush state to that of one dominated by sagebrush.
Restoration pathway R5A
State 5 to 1
This restorative pathway from the State 5 to the State 1 is very intensive. Often successful on small scales over very long periods of time, large scale restoration projects are not often able to be fully restored. This pathway would require continued sedimentation, proper grazing use, and proper hydrologic contributions. This community may reestablish the same hydrological function as in the reference state if the contributing upland sites provide the hydrologic contributions.
Restoration pathway R5B
State 5 to 3
This community becomes unstable, affects soil health and the hydrologic function as it is invaded by big sagebrush. The lack of adequate herbaceous cover to dissipate water velocity and encourage infiltration result in the formation of gullies and head-cuts. This is a very quick transition. Due to the lack of soil protection large flow events quickly destabilize the site and it transitions to the state with altered hydrological function (3). Anything that further reduces ground cover, like improper grazing use and continued drought, has potential to quicken this transition. Fire suppression and lack of shrub management in decadent sagebrush uplands continue to promote altered hydrologic function and also aid in destabilizing the bottom.
Transition T5A
State 5 to 6
Sagebrush encroachment with increasing sagebrush decadence and cover in adjacent upland communities brought on by prolonged drought, lack of fire, and improper grazing use can create alterations in the plant community that can leave the soils at risk for erosion and alter the hydrological function.
Restoration pathway R6A
State 6 to 5
To restore the site to the current potential state extreme inputs are necessary. This transition is from a big sagebrush dominated state, to a state that has been seeded with introduced or native perennial grasses. High energy inputs are needed for this transition. Sagebrush will need to be removed with vegetation treatment techniques (I.e. chemical, mechanical, or fire) and introduced or native species that are adapted to the area and adapted to management needs have been seeded and become established. Proper grazing use by both domestic animal and wildlife needs to occur. Often successful on small scales over very long periods of time, large scale restoration projects are not often able to be fully restored. This pathway would require continued sedimentation, proper grazing use, and proper hydrologic contributions.
Management practices that restore upland community health and functioning are critical to restoring a sagebrush dominated bottom to the current potential state. Such practices can include shrub management, and reseeding. Erosion control structures may be necessary. This needs to be used in conjunction with proper grazing management. Several wet years in a row can also decrease big sagebrush, as big sagebrush does not like to have it roots in water for extended periods of time.
