State 1
Reference

State 1 is named the Bunchgrass/Sagebrush state, in response to the dominance of mid to tall stature cool-season bunchgrasses that are prominant in each community. Rhizomatous wheatgrasses and mid to short stature cool-season bunchgrasses are secondary in these communities. Sagebrush is present on the site, but is not the major cover class.

Characteristics and indicators. Bunchgrass/Sagebrush State (State 1 - Reference) is characterized by the key species including: 15% or less composition by cover of Wyoming big sagebrush, with Bluebunch wheatgrass (<30%), rhizomatous wheatgrasses (Western and Thickspike), Indian ricegrass, and Needleandthread. Minor component to the overall composition is made up of Cusick's bluegrass, Bottlebrush squirreltail, Sandberg bluegrass, Prairie junegrass, and Threadleaf sedge. Green needlegrass is found in small isolated pockets throughout the land resource unit (LRU), on loamy soils. It is unclear if this is an effect of water catch areas, road drift influence, or management practices. Although intensive inventory data indicates no green needlegrass, it has been identified in ocular estimations, field notes and historic monitoring data collected by the Bureau of Land Management, within this LRU.

Resilience management. This state occurs in areas that are grazed moderately with periods of rest by large ungulates include livestock (cattle and/or sheep) as well as antelope, deer, and elk.

Community 1.1
Green Needlegrass/Wheatgrasses/Sagebrush

Figure 10. Green Needlegrass is the key species for the Reference Community 1.1.

The reference community (1.1) is declining in occurrence on the landscape. Considering the widespread decline in green needlegrass, it helps to remove management as the major contributor to this shift. Change or shifts in timing of precipitation, temperature shifts (spring warm up/fall freeze) or lack of precipitation could be the dominant driving factors for this occurrence. This plant community is the interpretive plant community. This state evolved with grazing by large herbivores and periodic fires. This plant community can be found on areas that are properly managed with grazing and/or prescribed burning, and on areas receiving occasional short periods of rest. The potential vegetation is about 75% grasses or grass-like plants, 10% forbs, and 15% woody plants. This state is dominated by cool season mid-grasses.

The major grasses include Griffiths and bluebunch wheatgrasses, rhizomatous wheatgrasses, needleandthread, and Indian ricegrass. Other grasses occurring in this state include bottlebrush squirreltail, prairie junegrass, and Sandberg bluegrass. Big sagebrush is a conspicuous element of this state, occurs in a mosaic pattern, and makes up 5 to 15% of the annual production. Green needlegrass is the key indicator of this site, but occurs as 2-10% of the annual production, although not a major contributor, it is thought to be indicative of the historic use of the site. Winterfat is a common component found on this site. Spike fescue will occur in areas, especially in depressional microfeatures. 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 800 lbs./acre, but it can range from about 500 lbs./acre in unfavorable years to about 1100 lbs./acre in above average years. This production is based on the historic records used to write the initial 10-14” Foothills and Basins East ecological site description. Currently, very few communities have been identified with this community, and no inventory data has been collected. There are historic notes files with the Bureau of Land Management that show support for this community (no production data available.)

Resilience management. Species diversity creates a persistence and adaptability from year to year that allows for quick recovery and drought tolerance. The site is at-risk due to the vulnerability and general decline of green needlegrass.

Community 1.2
Bluebunch Wheatgrass/Sagebrush

Figure 13. Bluebunch wheatgrass and sagebrush are prominant species in Community 1.2.

This site is very similar to the Reference community (1.1), and is the potential of this site that is under the highest level of ecological health with natural disturbance regimes occurring most commonly across the Big Horn Basin foothills, considering the past use and management improvements that have occurred over the last 65 years. The community can be found on areas that are within the scope of historic disturbances such as the allowance for burning at a historic frequency and the cattle grazing impacts replicative of large herbivores such as elk and bison. Properly managed locations with grazing and/or prescribed burning, with periodic short intervals of rest support this plant community and production potential. The vegetation composition is 75% grasses or grass-like plants, 10% forbs, and 15% woody plants. This state is dominated by cool season mid-stature grasses.

The major grasses include bluebunch wheatgrass, western wheatgrass, needleandthread, and Indian ricegrass. Other grasses occurring in this state include thickspike wheatgrass, prairie junegrass, green needlegrass, Cusick's bluegrass, sandberg bluegrass, and bottlebrush squirreltail. A variety of forbs and half-shrubs also occur, as shown in the following table. Wyoming Big sagebrush is a conspicuous element of this state, occurring in a mosaic pattern, and comprising 5 to 15% of the annual production.

The total annual production (air-dry weight) of this community is about 600 lbs/acre, but it can range from about 350 lbs./acre in unfavorable years to about 1025 lbs./acre in above average years.

Resilience management. Diversity of the plant species found on this site allows for a high drought tolerance, allowing persistence in the limiting climatic conditions of the Big Horn Basin and surrounding foothills. The structural diversity of Wyoming big sagebrush in conjunction with the mid-bunchgrasses (green needlegrass, Needleandthread, bluebunch wheatgrass), mid-rhizomatous species (western wheatgrass, montana wheatgrass, thickspike wheatgrass) and the short-bunchgrasses (prairie junegrass, bluegrasses, bottlebrush squirreltail) helps to provide snow catch and shade to capture and hold onto moisture to maximize availability during the growing season. This assistance to the hydrologic factor as well as the ability of each of these species to adapt to shifts in timing of precipitation helps to provide cover, although varying in composition, through a variety of conditions. Needleandthread is dependent on early spring moisture to perform well; years with late spring early summer moisture will produce minimal to no Needleandthread but will have an excellent cover or prairie junegrass. Whereas a year with late fall moisture and a slow warm up with spring moisture will produce an excellent cover of sandberg bluegrass but minimal production for prairie junegrass and Needleandthread. The persistence and adaptability from year to year of these species allows for quick recovery once normal precipitation returns. This variability will shift between phase 1 and 2 with extended periods of drought, use changes, and other natural and human derived impacts; but is not at risk of transitioning into a different state unless a catastrophic impact occurs. This community, as reference, is indicative of rangeland health which is based on: site/soil stability, watershed function, and biologic integrity.

Community 1.3
Rhizomatous Wheatgrass/Sagebrush

Figure 16. Increasing Wyoming big sagebrush and a shift in perennial grasses mark the 1.3 Community.

This community is found under moderate, season-long grazing by livestock or under areas affected by extended periods of drought. Historically, the reference state evolved under a low fire frequency (estimated to be 195 to 235 years between burns on the same community patch, also stated was that sagebrush has a post fire recover time-frame of 50-120 years or more in arid systems – Baker 2006) and with grazing pressure by large ungulates (elk, bison, deer, and antelope). Changes in herbivory pressure by sheep and wildlife in the area have allowed Wyoming big sagebrush to become woody and decadent. This increased cover by woody stems and leaf/stem litter under the canopy reduces the grass and forb component within the community allowing for the canopy cover to increase in percent composition. This dense litter mat impedes water flow into and out of the system further hindering the native grasses reducing the canopy and removing water from the site. Although the community is still dominated by cool-season perennial grasses, a stronger presence of short grasses and miscellaneous forbs have begun to hold a higher composition of the understory because the short mat forming grasses are able to catch and utilize the water that makes it through the canopy and litter layer.

Dominant grasses include needleandthread and western wheatgrass. Grasses and grass-like species of secondary importance include Cusick's bluegrass, sandberg bluegrass and threadleaf sedge. Forbs commonly found in this plant community include scarlet globemallow, desert parsley, fleabanes, and phlox. Sagebrush can make up to 30% of the annual production. The overstory of sagebrush and understory of grass and forbs still provide a diverse plant community overall, but the loss of taller bunchgrasses and the increase in low mat forming grasses reduces the snow catch and water retention of the site affecting production potential.

When compared to the Reference plant community 1.1 and 1.2, Wyoming big sagebrush has become a significant part of the composition of the site, counting for 15-30% of the canopy. Wyoming big sagebrush is a noticeable part of the overall production and accounts for the majority of the overstory. In most instances, the sagebrush density (number of plants per area) has not increased, it is more accurate to state the overall canopy density has increased with a decrease in the understory production and cover because of the shift in species of dominance. The percent composition by production is skewed giving the appearance that sagebrush has increased when it has remained similar across the community transition. The increase of sagebrush density is occurring on the landscape, but is a slow shift that occurs over 50-100 years, and is related to areas that have been protected from herbivory and use impacts such as enclosures, isolated areas due to development or other deterrents of use by large ungulates.

Review of historical accounts with century landowners has showed that although there is some increase in density of sagebrush, the canopy cover and decadence of sagebrush has occurred with the removal of sheep use on the foots hills. As the number of large sheep bands decreased and the trailing zones to move sheep from the basin to high mountain pastures was reduced, areas that had experienced this pressure now have short, decadent woody stands of sagebrush with a declining understory. Few areas of new seedling recruitment is seen. However, across a fence where the land is under recreational management and no sheep or stock have crossed the area since before the early 1900’s, the sagebrush is taller, higher in density with some seedling recruitment, but similar to the trailing zone, the canopy has become decadent and tight, with a reduced understory. The area is small and is not grazed by elk or other large ungulates as frequently as surrounding areas due to fencing and general location. Another area in close proximity has sheep grazing actively occurring with a rotational system between trailing through in spring and then grazing in the fall. This area has lower sagebrush height, smaller canopy cover with higher plant density. This comparison provided insight that utilization by sheep and other browsers has managed the canopy cover allowing the understory to remain strong in grasses and forbs, and has provided a mechanism to spur vegetative growth of the shrub canopy rather than woody cover. Although shorter in overall height, canopy cover is similar on average as the no use sight. Loss of herbivory by sheep and other large ungulate use (elk and deer) has allowed the canopy to become crowded, woody and decadent and lost the understory. Grazing by cattle can open the canopy, but can create a decadent woody cover with impact to the exposed understory, but not reducing the overall footprint of sagebrush.

Threadleaf sedge and needleleaf sedge have increased in percent canopy on site, making up at least 5-10% of the understory, this has a significant impact on moving hydrology off of the site due to the dense shallow root systems. Plains prickly pear cactus will also have increased, but occurs only in small patches. Indian ricegrass has decreased and may occur in only trace amounts under the sagebrush canopy or within the patches of prickly pear. Bluebunch wheatgrass may decrease, or may become broken and dispersed, occurring as disconnected strings of plants rather than the true bunch-form grass. This reduces its ability to protect the growth point of the plant making it more susceptible to damage and generally reduces the productivity potential of the plant due to the loss of access to nutrients from the surrounding areas.

The total annual production (air-dry weight) of this community phase is about 450 pounds per acre, but it can range from about 250 lbs./acre in unfavorable years to about 1100 lbs./acre in above average years.

Resilience management. Rangeland Health Implications/Indicators: This plant community is resistant to change, but is the at-risk community for this state because of the loss of structure, shifting hydrology, and loss of soil stability. The overall canopy is similar but bare ground has increased from an average of 30 to 45%, woody coverage has increased from an average of 10 to an average of 20% cover. Litter overall appears to be similar, and the biological crust is not altered. The herbaceous species present are well adapted to grazing and are mostly intact. Plant vigor and replacement capabilities are sufficient, but have declined from the reference community. Water flow patterns and litter movement may be occurring but only on steeper slopes. Incidence of pedestalling is minimal but increasing. Soils are mostly stable and the surface shows minimum soil loss. The watershed is functioning and the biotic community is intact but has shifted in composition.

Pathway 1.1A
Community 1.1 to 1.2

Green Needlegrass/Wheatgrasses/Sagebrush

Bluebunch Wheatgrass/Sagebrush

Timing of grazing, Dought, Climatic shifts – Although the full understanding of the decline of green needlegrass in this system is not understood, inferences can be made on part of the drivers for this shift. Location of this LRU places this site where historically, the area was grazed in the spring as sheep or cattle were trailed to summer grazing allotments with the US Forest Service, and then again in mid to late fall as the animals were trailed back to the basin for the winter. The repetitive use of sensitive species, specifically green needlegrass, would have slowly removed this plant from the system. Long periods of drought and shifts in spring precipitation patterns have weakened and impacted the productivity and vigor of most species, leaving a hostile climate for sensitive species to establish. Although the species of herbivory and timing has changed with the installation of more grazing management, pressure from large ungulates, namely elk, have had an impact on the foothills as they follow the available feed sources.

Pathway 1.2A
Community 1.2 to 1.1

Bluebunch Wheatgrass/Sagebrush

Green Needlegrass/Wheatgrasses/Sagebrush

Prescribed grazing, Broadcast seeding, Wildlife management – The repetitive use of the foothills at the same stage of growth weakened and removed green needlegrass; however, as lands were sold, or grazing permits changed, much of the landscape is now managed much differently and the large movement up the mountain is not as common of an occurrence in this region. Much of the sheep industry declined in the 1950’s through the 1980’s. Remnant populations are still seen and are slowly recovering, but the seedbank is not present to assist in a faster recovery of this specific species. Introduction of green needlegrass in road right-of-ways, pipeline reclamation, and well site reclamation, has provided more opportunity to see a stronger recovery. As wildlife management programs are instigated to help with disease issues and landowner conflicts, areas of heavy grazing impact from elk have been alleviated or grazing programs have been implemented to help reduce cattle pressure to allow for the wildlife use. Although there is still much work to be done, improvement of rangeland health is being documented.

Pathway 1.2B
Community 1.2 to 1.3

Bluebunch Wheatgrass/Sagebrush

Rhizomatous Wheatgrass/Sagebrush

Drought, Moderate Continuous Season Long Grazing – Under intermittent periods of drought, or under moderate grazing throughout the growing season, the bunchgrasses (bluebunch wheatgrass, green needlegrass, needleandthread) will begin to decline and rhizomatous (western wheatgrass) or mat forming species (threadleaf sedge) will increase. If fire is suppressed and as the grasses decrease, sagebrush will increase in density/composition. Exposure to season long grazing with no rest, especially with extended drought cycles, begins to weaken the root structure with reduced nutrient cycling (loss of leafy matter, green material) and water stress. The weakening and resulting shrinking of the root structure leaves the bunchgrasses at a disadvantage for seeking water, so will decline in composition as the rhizomatous species can hold on, transitioning the reference plant community to a lower phase with fewer bunchgrasses. Increased intensity and shorter rest patterns will continue to encourage the rhizomatous wheatgrasses, but will also open the canopy and provide a niche for the shorter stature grasses to increase such as needleleaf sedge and sandberg bluegrass. Successional shifts between Community Phase 1.2 and 1.3 will happen with the natural climatic cycles and disturbance regimes, but will be expedited with mismanagement.

Pathway 1.3A
Community 1.3 to 1.2

Rhizomatous Wheatgrass/Sagebrush

Bluebunch Wheatgrass/Sagebrush

Long-term Prescribed Grazing, Brush Management - With integration of a rotational grazing system or rest-rotation, and with management to reduce shrub canopy, the native bunchgrasses will begin to reestablish in this community, but it may take 5 to 10 years before significant change is noticed. Prescribed grazing, especially following sagebrush canopy treatments helps to remove woody debris and exposes a seedbank to encourage the native species. Allowing rest during critical seedling establishment stages and reducing competition of more competitive native species will help recovery. Hoof action helps to break up duff layers and open the seedbed to allow the desired bunchgrasses, such as green needlegrass, bluebunch wheatgrass, and needleandthread to reestablish or to increase, driving the recovery to the reference community (1.2). This hoof action, and brush treatment can be a tool to break up mat forming species to aid in addressing the hydrologic cycle, holding the water on site rather than allowing it to move off. A long-term management strategy may be required before any trend towards reference is noticed. The overstory of Wyoming big sagebrush may be the one factor that could require further manipulation to reduce canopy and composition to the desired 15%.

State 2
Perennial Native Grasses

Historically within the Big Horn Basin and the surrounding foothills, large landscapes were aerial sprayed for sagebrush control in the 1950’s and 1960's. Multiple large scale wildfires have occurred on the upper fringes of foothills. And in the more recent management strategies, various small scale sagebrush treatment methods have been completed for grazing improvements, large ungulate winter forage improvement projects, and for sage grouse habitat improvement projects. The removal of sagebrush has proven to be long term, with little to no woody vegetation recovery on many locations. This creates State 2, the Perennial Native Grasses State.

Characteristics and indicators. The dominant characteristic for this site is the complete lack of Wyoming big sagebrush, and in some instances all woody shrub cover. Fringed sagewort may be present or in abundance on these sites. Needleandthread and western wheatgrass are dominant with bluebunch wheatgrass, sandberg bluegrass, and threadleaf sedge common.

Resilience management. The scale and variability of sagebrush removal and conditions prior to treatment has led to a variable mixture of communities with one characteristic in common: the lack of sagebrush or other woody shrub structure (1-3 ft in height). Fringed sagewort and other sub-shrubs persist after fire, but do little to maintain or help recover the altered hydrologic function. This state is at-risk of further degradation due to drought, use, and fire.

Community 2.1
Perennial Native Grasses

Figure 19. Native perennial mid-stature cool-season grass community in the Absaroka lower foothills.

This plant community is evolving with the hydrologic shift caused by the loss of the shrub component. Remnant sagebrush skeletons help to hold a minor amount of moisture; however, overall the site has a reduced potential and an increased vulnerability due to the loss of the woody structural component of the canopy. The plant community appears to respond with an exaggerated shift in production from wet, normal and dry seasons; thus the fire threat will vary drastically from one production cycle to the next. This plant community is still dominated by cool-season grasses, while short-stature cool season grasses and miscellaneous forbs account for the balance of the understory. Continued drought or intense grazing places this community at-risk of shifting to a sod-forming, short statured grass dominated community. With the loss of the woody structure that aids in snow catch, and the responding loss of the ability to catch and hold winter precipitation and allow for spring thaws to slowly add this moisture into the system, creates a “drought-effect”. Increased exposure to wind and sun increases evapotranspiration/evaporation from lack of shade by woody cover, as well as increased run off/reduce infiltration and percolation. This leaves the community dependent on only the spring moisture that is received and when it is received. The grasses and forbs that are dominant and the production potential on the location from one year to the next depends on the amount of precipitation received during optimal growing temperatures, and when those conditions occur. Years with early snow melt, and quick warm up tend to cater to the upland sedges, blue grama, and non-native species. Early rains with a slow warm up cater to wheatgrasses, and sandberg bluegrass. Mid spring rains and warm up tend to encourage Needleandthread, green needlegrass, and forbs, while later spring rains encourage prairie junegrass specifically. This creates a highly variable community that will vary year to year, making management decisions difficult.

Wyoming big sagebrush is relict in small depressions on the landscape, providing little to no production and is not included as a component of the overstory. Initially no shrub component will be visible, but in some areas, rabbitbrush and perennial grasses will become dominant on the landscape with an understory of fringed sagewort and broom snakeweed.

The most prominent grass is typically western wheatgrass, with a mixture of bluebunch wheatgrass and Needleandthread co-dominating on the site. Grasses and grass-like species of secondary importance include Cusick's bluegrass, prairie junegrass, Sandberg bluegrass, needleleaf sedge and Threadleaf sedge. Forbs commonly found in this plant community include scarlet globemallow, milkvetches, and Spiny phlox. This site can still provide a diverse plant community, but lacks the structure for cover and wildlife habitat.

When compared to the Reference Community 1.1, Wyoming big sagebrush is absent, while sandberg bluegrass, prairie junegrass, western wheatgrass, needleleaf and threadleaf sedge have increased. plains prickly pear cactus will also have invaded. Indian ricegrass has decreased and may occur in only trace amounts within the patches of Plains prickly pear. Season of use and treatment type may limit or remove Winterfat from this site.

The total annual production (air-dry weight) of this community phase is about 400 pounds per acre, but it can range from about 125 lbs./acre in unfavorable years to about 800 lbs./acre in above average years.

Resilience management. Rangeland Health Implications/Indicators: This plant community is resistant to change. The herbaceous species present are well adapted to grazing; however, species composition can be altered through repeated use patterns or over-use. The herbaceous component is mostly intact and plant vigor and replacement capabilities are sufficient. Water flow patterns and litter movement may be occurring but only on steeper slopes. Incidence of pedestalling is minimal. Soils are mostly stable and the surface shows minimum soil loss. The watershed is functioning, but has been altered or affected by the loss of snow catch and ability to slow water movement over the surface; however, the biotic community is intact. The shrub or woody component of this sight shifts to sub-shrubs such as fringed sagewort, or in some cases scattered rubber rabbitbrush can be found. Bare ground is variable, but ranges from 20-50%. Soil stability is similar to the reference state, however the surface tends to be more crusted and so many times appears more stable until disturbed by hoof action. Litter averages are slightly higher due to the increased herbaceous materials, but woody or substantial debris is not present, and the small duff layers that were present under sagebrush plants are now devoid of the site. This reduces the overall organic movement in the system and attributes to the inability to slow surface water movement across the site, reducing infiltration and loss of hydrology.

State 3
Sod Bound

This state, State 3 - Sod-formers, is driven by low-stature sod-forming grasses. Although remnant populations of other desirable native grasses, threadleaf sedge, needleleaf sedge, and small areas of blue grama are the majority of the community composition.

Characteristics and indicators. The dominant sod-forming grass that currently exists within this LRU is threadleaf sedge with a mixture of needleleaf sedge and isolated occurrences of blue grama. Needleleaf sedge will form dense communities, but would not necessarily form a sod like threadleaf sedge.

Resilience management. These species occur naturally (in reference communities) within the ecological site. The general tendency is for these species to increase with prolonged drought or under grazing pressure, becoming dominant. Together as the dominant species, they alter the hydrology of the site by increasing the surface runoff from the dense shallow root system that inhibits the movement of water through or will direct surface flow around the edge of the map concentrating flow into channel like patterns, creating a difficult or hostile environment for native grass species and forbs to persist.

Community 3.1
Sod/Sagebrush

Figure 21. Threadleaf and needleleaf sedge dominate in sagebrush interspaces.

This plant community is the result of continuous season long grazing, repeated overuse, or prolonged drought, which has adversely affected the perennial grasses and shrub component creating an open canopy to encourage the mat forming plants to expand. The natural effect of threadleaf and needleleaf sedge, with the short stature dense root structure, is a decrease of water infiltration increasing channelization of runoff between vegetation patches. This, with the lack of structure to hold moisture, compounded by drought can continue to reduce the shrub component.

A dense sod of threadleaf sedge with patches of needleleaf sedge is the major grass component of this community. Incidental occurrences of other perennial natives generally within the sagebrush canopy or the protective ring of the prickly pear cactus clumps. Overall, Wyoming big sagebrush has been reduced in vigor and abundance across this site, but it still persists on the landscape (average density of 3-5% canopy cover).

When compared to the Reference Plant Communities 1.1 and 1.2, threadleaf sedge and needleleaf sedge have increased significantly, making up 30 to 60% of the canopy. Prickly pear cactus has invaded the site, and other cool season mid-stature grasses, perennial forbs, and most shrubs have been greatly reduced. Production has significantly decreased and bare ground may not vary or will increase (longer extents of bare ground between dense areas with minimal bare ground).

The total annual production (air-dry weight) of this state is about 300 pounds per acre, but it can range from about 100 lbs./acre in unfavorable years to about 750 lbs./acre in above average years. The higher productivity is generally in response to sandberg bluegrass or sagebrush production on the site.

Resilience management. Rangeland Health Implications/Indicators: This community is at-risk of transitioning to a completely sod-bound community with no woody vegetation. The dense root mats are 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. The shrub component will be degraded and eventually removed from the plant community under either scenario. The biotic integrity of this state is not functional and plant diversity is extremely low. The plant vigor is significantly weakened and replacement capabilities are limited due to the reduced number of cool- season grasses. This sod-bound plant community is very resistant to water infiltration. While the sod protects the site itself, off-site areas are affected by excessive runoff that can cause rills and gully erosion. Water flow patterns are obvious in areas of bare ground and pedestalling is apparent along the sod edges. Rill channels are noticeable in the interspaces and down slope. The watershed may or may not be functioning, as runoff may affect adjoining sites. This community has the ability to recover with management and some mechanical manipulation, once the sagebrush component has been lost, recovery or transition is not as feasible. The potential to recovery comparatively to the potential to shift into a stable state of a sod bound community creates the at-risk label. The threshold crossed to enter this state, the composition of sod-forming grasses and the lack of significant cover by other perennial grass forms, leaves these two communities (3.1 and 3.2) as similar communities with minimal shift between them.

Community 3.2
Sod/Cactus

Figure 24. Threadleaf and needleleaf sedge community.

Transitioning from the Sod/Sagebrush community phase (3.1) to the Sod/Cactus community phase (3.2) occurs relatively easily after the initial transition into a sod-former state through drought or continued pressure on the remaining shrubs. A dense sod of Threadleaf sedge, with Needleleaf sedge intermixed, is dominant with increasing Prickly pear cactus in the community. Cactus density has the potential to increase to a level that inhibits the ability for livestock to move through or graze the available forage. Wyoming big sagebrush has been generally removed from the community with only isolated occurrences. Rubber rabbitbrush is significantly reduced, but may persist on the landscape.

When compared to the Reference State (1.1 and 1.2), threadleaf sedge and prickly pear cactus has increased. All cool-season mid-stature grasses, forbs, and most shrubs have been greatly reduced or removed. Production has been significantly decreased.

The ability for the sedges, as well as species such as Sandberg bluegrass that persist in the community, to respond to spring moisture allows for a significant range in production. Study plots have documented a range in production of less than 30 pounds one year and with no change in density/frequency, produce over 400 pounds the next year based only on timing and amount of precipitation. So production is provided as an average or medial number and is not intended to cover the full range of production potential for this community.

The total annual production (air-dry weight) average for this community is 200 pounds per acre, but it can range from 75 lbs./acre in unfavorable years to 350 lbs./acre in above average years.

Resilience management. Rangeland Health Implications/Indicators: This sod bound 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 not functional, plant diversity is extremely low, and vigor is significantly weakened and replacement capabilities are limited due to the reduced number of cool-season grasses. The dense root mat of this community is resistant to water infiltration. The dense root mat of threadleaf sedge protects the community itself from runoff impacts, off-site areas are affected by excessive runoff that can cause rills and gully erosion. Water flow patterns are obvious in the bare ground areas and pedestalling is apparent along the sod edges. Rill channels are noticeable in the interspaces and down slope. The watershed may or may not be functioning, as runoff may affect adjoining sites.

Pathway 3.1A
Community 3.1 to 3.2

Sod/Sagebrush

Sod/Cactus

Intensive Brush Management, Fire, Frequent or Severe Grazing, Drought – In a sod dominant community, the hydrology has been altered drying the soils and reducing the potential for seedling establishment by many native grasses and shrubs. Once sagebrush is removed from this community by intense grazing pressure, drought and insect damage or by fire (rare), wild or prescribed, the community will phase into a complete sod community. The Wyoming big sagebrush component of this community is the at risk species. Drought alone, or with grazing pressure through season or year-long patterns, will create a sagebrush canopy that is decadent and dying. The sod dominated community reduces the ability for sagebrush to propagate, also leading to a recession of sagebrush. Fire has little influence on this community due to the lack of fine fuels to carry it; but in rare circumstances, isolated areas may burn within the shrub canopy. In some cases, rubber rabbitbrush will persist or increase slightly on a site as sagebrush diminishes. It is also noted that with periods of drought there is a noted decrease in the health and vigor of threadleaf sedge and blue grama. The dense root structure of the sod-former is reduced allowing other species to establish.

State 4
Sagebrush and Bare Ground

Wyoming big sagebrush creates a niche for most herbaceous understory to persist and maintain some vigor in difficult conditions by utilizing the moisture and shelter provided by the canopy as well as protection from grazing. Persistence of drought and/or frequent over use by livestock and/or wildlife leads to a decline of the herbaceous species, creating the Wyoming Big Sagebrush and Bare Ground state. This state can be exacerbated by insects and other human disturbances.

Characteristics and indicators. There is a high level of variability of species in this State, that will shift in response to precipitation or that is in response to past management. Only one well defined community will be provided, with discussion of transitions or variances from this community. The total woody canopy cover does not necessarily always increase with this community, but the percent composition by cover and production is swayed by the decrease of herbaceous vegetation and the relative stability of production by the woody species, creating the appearance of increased canopy by sagebrush.

Resilience management. Risk of wildfire within this state is minimal due to the lack of fine fuels within the understory, but the canopy of the woody vegetation can easily carry a fire under certain climatic conditions. Depending on the prescription of use, trailing and other erosional patterns are highly visible in this state. Protection from wildfire and use, on a long-term perspective can aid in the transition of a reference community (1.1 or 1.2) to this state as sagebrush becomes dense and decadent reducing the ability for the herbaceous component to maintain vigor; leading to a high rate of bare ground and sagebrush cover. As the herbaceous cover declines and the site continues to weaken, the sagebrush cover is susceptible to attack by insects, disease, and general old age that can remove it from the system creating a system that is at risk of invasion or transition to a more degraded state.

Community 4.1
Wyoming Big Sagebrush/Bare Ground

Figure 27. Sagebrush dominated community with minimal herbaceous cover in interspaces.

This plant community is the result of frequent and severe grazing and/or protection from fire. Sagebrush dominates this plant community, as the annual production of sagebrush exceeds 30%. Wyoming big sagebrush is a significant component of the plant community and the preferred cool season grasses have been eliminated or greatly reduced.

The dominant grasses are Sandberg bluegrass and Western wheatgrass. Prickly pear cactus often increases. The interspaces between plants have expanded leaving the amount of bare ground more prevalent. As compared with the Reference Plant community 1.1, the annual production is reduced, but will be similar in drought years as the shrub production compensates for the decline in the herbaceous production. This community is vulnerable to invasive weeds such as Cheatgrass, Russian knapweed, leafy spurge, or Canada thistle if a seed source is available.

The total annual production (air-dry weight) of this state averages 450 pounds per acre, but it can range from 150 lbs./acre in unfavorable years to 700 lbs./acre in above average years.

Resilience management. Rangeland Health Implications/Indicators: This plant community is resistant to change as the stand becomes more decadent, but is at-risk due to the susceptibility to invasive species. This plant community may be more resistant to fire as less fine fuels are available and bare ground increases. Continued frequent and severe grazing or the removal of grazing does not seem to affect the composition or structure of the plant community. Plant diversity is moderate to poor. The plant vigor is diminished and replacement capabilities are limited due to the reduced number of cool-season grasses. Plant litter is noticeably less when compared to the Reference Plant Community. Soil erosion is 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 down slope.

State 5
Invaded Sagebrush

State 5, Invaded/Sagebrush State, is successional in nature in response to the introduction and increase of invasive/aggressive weeds. Primarily, cheatgrass is the identified threat to the Absaroka foothills at this time. This state has maintained the native species, but the presence and threat of invasive species has crossed a threshold, affecting the at-risk or management capabilities of the native species that remain.

Characteristics and indicators. This state is characterized by the presence of an invasive/non-native species. Extended periods of drought alone or in combination with misuse, insect damage or wildfire has weakened the native composition of the community opening the canopy for invasion. The competitive nature of annuals and other invasive species, creates a complex environment that inhibits control, and makes it implausible to attain complete eradication once an invasive species has established on the landscape. Although cheatgrass is the threat most prevalent to rangelands on a large scale, a variety of thistles, knapweeds (namely spotted and Russian), and whitetop (hoary cress) are increasing in density and frequency, producing their own set of challenging management issues. As more species are found within the foothills region or as other species become more prevalent on a large scale, the community dynamics in this state will shift in response to the concerns of the identified species.

Resilience management. Cheatgrass or Downy brome (<a class="species-link" href="https://plants.usda.gov/core/profile?symbol=BRTE" target="_blank" title="Open in plants.usda.gov"><i>Bromus tectorum</i></a>) is the invader that has the greatest concern for most land managers. This invader has an aggressive growth habit that creates a hostile environment for most native species, including sagebrush. Multiple growth cycles throughout a year leaves a thick litter (duff) layer and builds a significant seedbank; and the ability for this annual to persist through the winter under a blanket of snow and sprout early gives it the advantage of all early spring precipitation and snowmelt. Shifts in climatic patterns, changes in management, and exposure to human activity are a few of the explanations for the current flush and rapid expanse across the western United States.

Community 5.1
Native Grasses/Invasives/Sagebrush

Figure 30. Native perennial grasses with an new understory of cheatgrass.

The Perennial Grasses/Invasive Species/Wyoming big sagebrush community phase has maintained a representative sample of native perennial grasses and forbs that are key to this particular ecological site with the accompanying Wyoming big sagebrush component. Although this community phase is very vulnerable of becoming an invader driven system, if native grasses can maintain at least a 5% composition, there is still a chance that the community can be improved, extent of improvement and exuberant costs and labor required limit the economic feasibility.

This community phase is characterized by a significant presence of invasive species composition (5% or greater) on the landscape, and are prominent on the site (referring to a more wide scale composition, not one isolated patch in an isolated portion of the landscape).

The litter or duff layer created by many of the known invasive species, but specifically cheatgrass, is significantly higher than the native community. This duff layer creates a barrier that can impede water infiltration and increase runoff, accelerating erosion. This is aggravated with increased slope. The duff layer creates an extreme hot zone during wildfires that can sterilize the soil through volatilization of needed nutrients or by the formation of an ash cap that seals the soils, preventing water infiltration and seed penetration, reducing the ability for re-vegetation post-disturbance.

Production yields of the perennial grasses and forbs are reduced but the total production will maintain or may be slightly elevated due to the overall biomass and expanded growth potential of many of the annual or invasive species. A specific production range is not provided due to the variability of composition that will effect overall production.

Resilience management. Rangeland Health Implications/Indicators: This plant community is prone to fire as fine fuels increase with the added biomass and litter produced by the invaders. Plant diversity is moderate for this phase as the remnant perennials and the maintained composition of woody shrubs keeps a diverse community. The plant vigor is diminished and replacement capabilities are limited due to the reduced number of cool-season grasses and the limited moisture and nutrients available after cheatgrass has sprouted. Plant litter is noticeably more when compared to reference communities due to the potential biomass produced by the invasive species (species dependent). Soil erosion is variable depending on the species of invasion and the litter accumulation thus associated. This variability also applies to water flow patterns and pedestalling. Infiltration is unaltered or slightly reduced; however as the duff layer or litter builds infiltration and runoff will increase.

Community 5.2
Invasives/Sagebrush

As the native populations of perennial grasses and forbs are lost through excessive use or disturbance, the site becomes invader driven. Continued environmental or management derived impacts to the shrub component places this community at risk of crossing a threshold transitioning to State 6, Invaded/Annuals. At this point, hydrologically and biotically it will become irreversible without complete reclamation, which makes this community phase, the At-Risk community.

Wyoming big sagebrush is able to compete and maintain a strong community under a heavy infestation level of most invasive species, unless fire or similar disturbance removes the woody cover. The canopy of the sagebrush serves as a protective niche in the system for native grasses and forbs, allowing remnant populations to persist. But the system is low in resistance and even lower in resilience. The fine fuels or biomass produced by most invasive species, with the most obvious being cheatgrass, fire is a significant threat and frequent occurrence.

Strategies to control or manage for invasive species, namely cheatgrass, are being researched readily across the western United States. High intensity grazing with chemical control and the use of biological agents are techniques that have been trialed, with varying levels of success. The key management strategy needs to be to maintain the remnant populations of native grasses, and to reduce the risk of fire to allow the persistence of Wyoming big sagebrush. This will maintain the minimal biotic integrity (maintaining species richness providing structure and a range of growth traits allowing adaptability of the site to varying climatic swings) and help support the hydrologic function (providing snow catchment, and shade to allow a slow release of winter precipitation during spring melt providing a longer moist season for optimal growth of native species) of the location. Each location will need to be addressed individually to determine the best management strategies to utilize the native species present in the system and to determine the limitations of the resources.

Resilience management. Rangeland Health Implications/Indicators: This plant community is resistant to change in relation to returning to a native dominant system, but as the stand becomes more decadent it loses its resistance as it shifts to an invader only community. These areas may be more prone to fire as fine fuels are more available and the bare ground between the sagebrush plants is decreased with increased biomass and plant density of the annual invaders. Plant diversity is poor. The plant vigor is diminished and adaptibilityreplacement capabilities are limited due to the reduced number of cool-season grasses. Plant litter is noticeably more when compared to reference communities due to the potential biomass produced by the invasive species (species dependent). Soil erosion is variable depending on the species of invasion and the litter accumulation thus associated. The variability of the water flow and pedestalling as well as infiltration and runoff is determined again by the species that establishes on this site.

Pathway 5.1A
Community 5.1 to 5.2

Frequent or Severe Grazing, Wildfire, Drought – Drought, wildfire, or other climatic stresses on the system will continue to hinder the native species, reducing their ability to maintain their footprint in the plant community. This continued stress or the complication with frequent or severe grazing pressure from wildlife and livestock can reduce the native composition to an unviable or unsustainable population and allow the invasive species to be dominant. The fleshy growth of native species are generally preferred over the thin straw like growth of cheatgrass. During initial spring green up while natives are still dormant, wildlife and cattle will utilize the cheatgrass, but once the natives begin to green up, the animals will switch back to the preferred This is more typical in species such as knapweeds, Whitetop, and specifically cheatgrass (Downy brome).

Pathway 5.2A
Community 5.2 to 5.1

Integrated Pest Management/Weed Control and Long-term Prescribed Grazing - Control of invasive species and managing grazing to allow use of the invasive species with minimal impact to the native population, will allow the community to regain or maintain potential. But at this time it is not possible to eradicate the invasive species, and sustained control requires intensive inputs over the course of several years. To maintain the system with no further degradation requires a dual approach of both long-term prescribed grazing with an intensive weed management (integrated pest management) plan. No one single practice can sustain this phase, it requires intensive management to prevent the transition to State 6 - Invaders/Annuals.

State 6
Annual Invaded

The transition of an Invaded/Sagebrush community into the Invaded state, is typically a result of wildfire, a failed controlled burn or other event that removes the sagebrush from the site and allows a readily available seed bank or seed source of the undesirable species to flourish.

Characteristics and indicators. The most common community that is found in the foothills and through the Big Horn Basin and much of the surrounding regions is Cheatgrass. However, there are other threats present, such as knapweeds, thistles, and Whitetop, that can develop into near monoculture stands. The loss of diversity, changes to the potential of a site due to allelopathy or other deterrent characteristics of invasive species, and risks or land use capabilities associated with the various invasive species creates a hostile environment for both native species and grazers.

Resilience management. The resilience and resistance of the invaders create a management road block that is usually financially driven. Many times, once an invasion reaches this point, many land managers have no choice but to learn to utilize what they have rather than to try to treat or improve the site, specifically in relation to cheatgrass control.

Community 6.1
Invasives (Annual Grasses)

Downy Brome, better known as cheatgrass (Bromus tectorum), is able to green up and grow late into the fall and green up early spring before snowmelt. This early and late growth pattern allows cheatgrass to utilize fall and spring resources that are otherwise stored for the cool season perennial vegetation before the native species can begin to break dormancy. Seeds are able to persist for long periods of time until growing conditions are optimal, allowing growth before most native species.

The plant’s ability to grow quickly utilizing minimal available resources and the ability to produce large quantities of seed quickly, and to reproduce in poor conditions are what drives this plant above the natives and many improved varieties of grass. The morphology of the seed allows for easy dispersal and longevity creating a widespread and long-term seed bank. These traits create a management challenge that has not been successfully met at this time. Once this species has a niche on a landscape it is resistant and resilient to change.

In this community, with the absence of sagebrush, there may be native species that will persist in small scattered populations or sparsely under the canopy of the cheatgrass. Certain climatic conditions will allow natives to show their resiliency and respond to the available resources (typically mid spring moisture), but are generally unable to out-compete the annual invader, and remain secondary in the community. The ability for cheatgrass to emerge, bolt, produce seed and mature out two to three times within a year utilizes all available soil nutrients and moisture resources. Chemical control is difficult to attain and maintain success without lasting effects on the native grasses in the area. Chlorosis of wheatgrasses, stunted plants, and loss of certain forbs are a few of the residual chemical effects (Plateau is what has been observed in this region.) This generally comes from the chemical composition and its ability to bind to the chemistry or nutrients in the soil inhibiting the uptake by roots.

The extensive fine fuels/biomass load created by cheatgrass can increase the fire frequency interval to an annual to five year cycle, preventing sagebrush and other woody species from establishing on the site, and has negative impacts on many of the native herbaceous species in the understory, by increased evaporation and mineralization/vaporization of many of the nutrients rendering the soils nearly sterile.

The grazing potential is limited due to the unpalatable and harsh environment that the mature seeds create with their long awns and chaff. If grazed in early spring or late fall some of this can be avoided, but general use through the middle of the growing season is difficult, and defeats the purpose of intensively grazing the location. In smaller invaded sites or under certain conditions, grazing can be used as a tool within the integrated pest management toolbox, but it is not effective alone.

Resilience management. Rangeland Health Implications/Indicators: This plant community is resistant to change. Plant diversity is poor. The plant vigor is diminished and replacement capabilities are non-existent due to the loss of cool-season grasses. Plant litter is noticeably more when compared to reference communities in response to the dense duff layer created by Cheatgrass. Soil erosion is generally reduced in response to the litter accumulation; however, the annual nature of this plant accentuates the water flow patterns and pedestalling. Infiltration is reduced and runoff is increased with the loss of perennial vegetation and root depth and density. Overall biotic integrity is lost in this community.

State 7
Disturbed

The arid nature of this region has played a major role in the development and transitions in land use over time. Landscapes accessible by irrigation water and equipment were farmed and many were later abandoned and left to return to rangeland. Other landscapes were treated with a variety of prescriptions to manage or eradicate sagebrush. Tillage of the soil, change in hydrology caused by the loss of vegetative structure, constant climatic fluctuations, and advancements in seed sources have created this altered state.

Resilience management. Once a soil has been disturbed, whether it was mechanical, cultural, or natural the change in soil structure, hydrologic function, and possibly stability prevent a site from supporting the native vegetation or responding to management the same as an undisturbed site. Reclamation or restoration of an area will not replace the original function and factors that made the original location respond as it did. So these "altered" lands may, after significant inputs and time, look similar to the Reference communities (1.1 or 1.2), but they will not be able to respond/function the same as the Reference community. The Disturbed or degraded state could be drafted as a stand-alone box within the state and transition model diagram. No matter what state a location is classified, once the site has experience an event that has altered the soil properties (erosional, depositional, hydrological or chemical), the site potential is altered. To consider this as an alternate ecological site would not be unreasonable. In some cases (site by site consideration), a re-correlation of a location may be the best solution. But in many cases, the soils have not been altered out of the current site characteristics, but the potential has shifted enough that it is no longer truly comparable to the reference state. The loss of soil structure, degredation of soil biota, loss of argillics or clay illuviation, and minor chemistry changes, alter water and nutrient movement in the soil profile and reduces the water holding capacity. The time required to rebuild structure and have further soil formation, and recovery of biota and vegetation are highly variable depending on the climatic conditions following the event. The initial flush of vegetation is kochia and Russian thistle and mustards. Although they provide organic material, nutrient flow and erosional protection, they lack the structure and root system to fully stabilize the site. The site may become similar in composition to reference, but the integrity of the soil is altered, changing potential of the site. So a dynamic state was captured to detail the altered communities that exist on the landscape.

Community 7.1
Disturbed/Degraded Lands

Disturbed or degraded lands are characterized by alteration of the soils to a degree that the functionality (erosional, depositional, hydrological or chemical) and potential of the soils has been impacted. Site specific evaluations need to be completed to determine the level of effect. The method and severity of alternation, as well as the spatial extent of the disturbance will determine vegetation response and management needs. Linear disturbances, such as trails and roads, will hold a different risk than patchwork or polygonal disturbances, such as well-pads or parking areas. Small scale or isolated disturbances (spot fires, prairie dog town) can be just as significant of a risk as a large scale disturbance (mine lands).

The growth curve of this plant community will vary depending on the successional or seeded species that are able to establish in an area. On locations that were seeded with non-native species, the growth curve will vary from the native community. But in the case of an early successional community, the growth curve may be similar. For a more accurate growth curve, a site specific species inventory and documentation of the climatic tendencies should be collected.

Resilience management. Rangeland Health Implications/Indicators: The plant community is variable and depending on the age of the stand and the stage of successional tendencies that the location is in will determine how stable (resilient/resistant) the community is. Plant diversity of these successional communities is generally strong, but is usually lacking in the structural groups that are desired on the site. In areas of new or frequent disturbance, annual weedy species or early successional plants will be the dominant cover, providing a strong diversity, but has minimal structural cover for some wildlife. As the site matures or as the period between disturbances is lengthened, perennial or tall-stature, strong rooted species will increase providing protection and help to improve hydrologic process and general cover for grasses and shrubs to begin to establish. This flexibility within the community creates a variable level of biotic integrity. Soil erosion is dependent on the disturbance regime and the biotic integrity of the community. The variability of the community also affects the water flow, infiltration, runoff, and pedestalling risk. Other factors that are more prevalent or influential for these sites are surface roughness and brokenness (tire tracks, hoof action, smoothed, denuded surfaces, trails that may focus the water).

Community 7.2
Reclaimed Lands

Shifts in reclamation practices over the last several decades have altered the success and stability of reclaiming a site. Crested wheatgrass was a species used frequently for reclamation throughout Wyoming; and across the state, many of these communities persist today. These stands are stable and generally persist as a monoculture until a disturbance creates a niche for native species to establish. Crested wheatgrass is creeping out into native communities as readily as native species are moving into the Crested wheatgrass stands.

Russian wildrye and varieties of rhizomatous and bunch-wheatgrasses are used in mixes to help increase establishment on these sites. Although the success of vegetative seedings are low to moderate in this LRU, due to the variable amounts and timing of precipitation events, limited areas along pipeline corridors, well sites or pad sites, and along transportation corridors have succeeded.

Current interpretations of reclaimed or restored refers to the establishment of native species in a composition as close to a natural (pre-disturbance) plant community as possible. This excludes the use of non-native species and allows for a more similar ecological response than what is expected with non- native species. Although native species are used in reclamation, these plantings will not replicate the reference community in response to management due to the change in soil dynamics with mechanical disturbance (seedbed preparation and seeding), but they may be similar.

The growth curve of this plant community will vary depending on the species that are selected for the reclamation seed mix. For a more accurate growth curve the species used and the climatic tendencies of the region must be considered.

Resilience management. Rangeland Health Implications/Indicators: Seeding mixtures will determine the plant community's resistance to change and resilience against the threat of invasive species and to erosion. Many of the stands established during seeding are diversity poor, but are better than the mono-culture stands that were seeded historically. Many seeded sites may be prone to fire because of the increased production as they mature (more biomass and possibly more litter) providing abundant fine fuels to carry a fire. Soil erosion is variable depending on the establishment of the seeding, how it is seeded, and mechanical procedures put in place. The variability of the water flow and pedestalling as well as infiltration and runoff is determined again by the species that comprise the community and the method of seeding (site preparation and seeding practice).

Pathway 7.1A
Community 7.1 to 7.2

Seeding, Brush Management, Integrated Pest Management, Prescribed grazing management – With proper mechanical improvements and follow-up maintenance, a disturbed site can be improved and utilized for the intended purpose. However, climatic limitations limit the success of seedings. Depending on the location, seedings are slow to establish and invasive species are a risk to most locations within the foothills, creating a moderately low success potential for this process. Proper preparation of a location to be seeded or once a site is seeded, integrated pest management becomes crucial to allow seedling establishment and to prevent invasive species from invading the area. Brush management may be required to open areas that can readily be seeded.

Pathway 7.2A
Community 7.2 to 7.1

No use, Lack of Fire, Long-term Prescribed Grazing, Frequent or Severe Grazing - In general, if a site is not maintained with the conditions of which the species are adapted under, a decline in vigor and a corresponding shift in composition will occur. Since the soils are altered from reference state due to plowing, mining, or other similar disturbances, the plant community will not follow the same expected shifts as the native community. Monitoring and trend over time need to be recorded to determine if a location is degrading or adjusting with the climatic variables of the site. The initial establishment phase of a reclaimed site is crucial to determine success, but at any stage of a seeding, degradation or further disturbance can occur forcing the site to phase back to the disturbed community.

Transition T1A
State 1 to 2

Drought, Fire (Wild or Prescribed), Disease/Insect Damage - Damage leading to death of sagebrush occurs following prolonged drought that weakens the plants, allowing attacks by disease and/or insects. Across much of the Sagebrush Steppe, brush management was a common practice that historically resulted in complete eradication of sagebrush. Removal of sagebrush by fire, whether wild or prescribed, is most common, however chemical removal has occurred historically and is still a practice used today. Although new methods have improved and reduced the large scale approach, the scars remain on the landscape. Wildfire, insects, and disease damage have aided in the decline and removal of sagebrush from the system as well. Shrubs rely on their own structure to capture and hold moisture received through winter precipitation until the plant can utilize it for growth. The loss of structure alters the hydrology of the site, causing a perpetual drought cycle on the landscape reducing the ability for sagebrush to propagate. Unless methods of re-introducing sagebrush or other shrubs to provide the woody structure, very little to no re-establishment is possible. Slow recovery times of sagebrush allows for a grass dominated system to persist.

Constraints to recovery.Slow or the inability of sagebrush to recover is a response to the shift in the hydrologic processes within a location. This shift in hydrology is the constraint to recovery. Sagebrush provides a catchment for snow in the winter allowing for slower infiltration of spring melt. These small catchments help feed moisture or hold moisture on the site. The loss of sagebrush canopy also allows for higher solar radiation and greater wind stress on plants, creating drought conditions.

Transition T1B
State 1 to 3

Frequent Grazing (Yearlong), Brush Management or Fire with Drought – Severe and frequent grazing reduces vigor and presence of key species. As bluebunch wheatgrass, needleandthread, and the rhizomatous wheatgrass begin to decline, shorter statured grasses become dominant. Animal disturbance (hoof impact) caused with long duration, high intensity grazing reduces the bunchgrass component by allowing repeated defoliation of the desirable species, reducing recovery potential and ground cover for insulation and snow catch, as well as physical damage to the crown and growth points of the plants; weakening and over time removing select species. The open canopy and hoof impact encourages species that are tolerant to high traffic and that can utilize the small shots of spring moisture, these species are generally mat or sod-forming species such as threadleaf sedge and blue grama. Prolonged drought stresses the plants, and opens the canopy for these two quick responding plants to fill in the interspaces. The shallow, dense root mats will continue to spread over time. The added removal of sagebrush with animal impacts, fire or brush management may open the canopy more and aid in establishing this sod-form community. A combination of needleleaf and threadleaf sedge and isolated areas of blue grama persist as the wheatgrasses are reduced. When the sagebrush component of this community has been degraded or removed, by drought or heavy use, the transition has a high probability of occurrence on the landscape. Season of use and intensity of grazing (time and timing) is a trigger that can reduce the risk of transitioning, or if done poorly can force the transition to occur rapidly. This community is dominated by cool season species, providing good spring moisture, growth and maturity of these plants can happen quickly within the first two weeks of June, while blue grama is just beginning. By alternating when the community is grazed providing periods of rest during the critical initial green up and growth in the spring, and allowing recovery time before the community is grazed again within the year, allows the bunchgrasses and more solitary grasses to maintain vigor and production. This also allows for summer use when the warm season grasses are growing (blue grama) which will help to utilize this species and maintain a low cover.

Constraints to recovery.The altered hydrology that occurs with a transition to the dense, shallow root system of sod-formers coupled with the degraded or loss of sagebrush limits the ability of this community to recover. Sod-formers have proven difficult to reduce or remove from the system, which hinders the recovery or re-establishment of other perennial grasses.

Transition T1C
State 1 to 4

Frequent and Severe Grazing (Year-long) or Drought with Brush Management or Wildfire - Frequent or high intensity herbivory on a community weakens the ability for the grasses to persist, especially during prolonged drought. With the weakened grasses and with prevention or lack of fire, the composition will shift to mostly sagebrush, and with time sagebrush will increase in density preventing the recovery without intervention. The conversion to a Wyoming Big Sagebrush/<a class="species-link" href="https://plants.usda.gov/core/profile?symbol=2BARE" target="_blank" title="Open in plants.usda.gov"><i>Bare Ground</i></a> plant community is a response to extended periods of stress, both climate and/or human induced. Intensive grazing with minimal to no recovery period begins to transition the community. With added climatic stress, species diversity and productivity is lost, and the community crosses into the Sagebrush/Bare ground State. The illusion of crossing the threshold to State 4 is captured with fluctuating precipitation patterns affecting production of prominent plants within this system. The loss of species diversity and increased bare ground with lack of litter are the indicators that a true transition has occurred.

Constraints to recovery.The ability for the native perennial grasses to increase while reducing the canopy of sagebrush is the challenge for recovery for this community. With the reduction in sagebrush canopy, if precipitation and other climatic conditions are not favorable invasive species have an opportunity to establish preventing the native grasses from recovering.

Transition T2A
State 2 to 6

Frequent and severe Grazing, Drought, Wildfire, or Disturbances with a seed source present - Further disturbance of this community after the loss of sagebrush opens the potential for invasion by weedy species especially cheatgrass following a fire. The influence of fire and other disturbances in these communities opens the canopy allowing establishment of invasive non-native species such as cheatgrass (downy brome), thistles, knapweeds, and Whitetop. Drought alone, or in combination with fire, will create conditions prime for invasion. Photo and transect documentation shows that as the drought persists, Cheatgrass has increased exponentially each year, starting along roadways or disturbed areas and then radiating out from there. When compounded with or impacted solely by heavy grazing pressure or poor management, the risk of introducing invasive species in the system increases. Continued use or increased use post fire by large herbivores, elk specifically, with continued drought can weaken the native grasses opening the canopy to the threat of invasive species as well as be a seed source. Elk are carriers of many undesirable seeds into disturbed landscapes. Their ability to seek out the green patches of new growth, especially during drought, makes spring burns or summer burns with fall moisture susceptible as the moisture following the burn will create a green up of plants that entice the elk. This can have a positive impact by breaking up charred areas reducing hydrophobic tendencies, but it can also remove sensitive cover that could lead to erosion by wind and water, or could remove or hinder the native species that were trying to recover and allow an invasive species a niche to establish.

Constraints to recovery.The ability to control or eradicate cheatgrass and other major invasive species is the limiting factor of recovery for this transition.

Transition T3A
State 3 to 5

Restoration pathway R4A
State 4 to 1

Prescribed Grazing with Brush Management or Wildfire - Treatment to thin the canopy to allow the native vegetation to respond to improved moisture and sunlight followed by prescribed grazing to prevent overuse of the exposed grasses will help this community recover. Treatment will vary depending on the exact composition of grasses remaining and the potential threats to the location. Removal or thinning of the sagebrush within this community will help to reduce competition, encouraging grasses and forb recovery if the disturbance or over-use (recreational or grazing pressure) is reduced. Drought may prolong the time required for recovery. Mowing or mulching sagebrush trials have shown a strong response by grasses with little to no recovery time post treatment. The resulting community with these treatments is driven by the dominant species within the community pre-treatment or climatic and treatment conditions during and following the fire may sway the community. It is crucial to closely check the immediate and surrounding area around treatment site to ensure no invasive species (cheatgrass) is present.

Transition T4A
State 4 to 2

Drought and Disease/Insect Damage, Fire or Brush Management - Degraded communities with a perennial native grass component within the sagebrush that are exposed to fire or the drought stress and disease/insect damage will transition to a perennial grass dominant system, however, the composition and productivity is not the same as a reference community that transitions to this community. The community is highly variable, but with time and without weed infestation will become very similar with similar management.

Constraints to recovery.The length of time and difficulty to re-establish a strong population of sagebrush inhibits the recovery opportunities for this community.

Transition T4B
State 4 to 3

Brush Treatment or Fire, Frequent Use - Removal or thinning of the sagebrush by mechanical, chemical or fire with an understory of Blue grama/Threadleaf sedge will lead to a threadleaf sedge or blue grama sod community, especially with the stress on other perennial species during drought. Frequent use of this community during dormant season will work to reduce the sagebrush through trampling and grazing, but will encourage the lower stature sod-formers in many instances. Within the Sagebrush/<a class="species-link" href="https://plants.usda.gov/core/profile?symbol=2BARE" target="_blank" title="Open in plants.usda.gov"><i>Bare Ground</i></a> community, several native species can reside within the protective niche of the sagebrush canopy. Once that canopy is removed or opened, the management or level of disturbance will dictate which species will become dominant. If threadleaf or needleleaf sedge already have a strong presence, once the canopy is opened, they both can establish quickly in the right conditions driving the community into a sod dominant state (State 3).

Constraints to recovery.The time required and difficulty in recovering sagebrush with the difficulty in reducing sod-formers and encouraging mid to tall-stature cool-season grasses limits the ability for this community to recover.

Transition T4C
State 4 to 5

Fire (wild), Frequent or severe grazing, Drought with Insect Damage/Brush Management – Throughout most of this LRU there is a seed source present for cheatgrass, knapweed, and other invasive species. Stress to the native community from drought; events such as wildfire or prescribed burning and other forms of brush management; or ground/soil disturbance including impacts by grazing large herbivores or recreation that open the canopy and break the surface of the soil, creates a niche for invasion by undesirable weeds. Documentation has shown that many times the invasion starts with one or two isolated plants, that if caught can be treated and a full infestation avoided; however, when unseen or ignored, the population soon grows exponentially as further stress or disturbance occurs. In some cases the invasive species once established can create it’s own habitat, forcing the weaker native species out. The open canopy of the Sagebrush/<a class="species-link" href="https://plants.usda.gov/core/profile?symbol=2BARE" target="_blank" title="Open in plants.usda.gov"><i>Bare Ground</i></a> State is vulnerable to invasive species without further influence. With continued over-use, drought, insect damage or fire, the invasive species will establish and quickly dominate a location. The threshold species in this system is Wyoming big sagebrush, which protects the remnants of the perennial natives, allowing them to persist on the landscape.

Constraints to recovery.The lack of success in eradicating cheatgrass or other invasive species is the only constraint to recovery of this community.

Transition T4D
State 4 to 6

Wildfire, Drought, Disease/Insects - With catastrophic or intense wildfires, prolonged drought with over use by large herbivores or large scale land disturbance occurs in areas where invasive species are present, the exposed soil and lack of native vegetation from already stressed communities creates the environment for the invasive species to establish as a mono-culture with possibly only small isolated remnants of native species. The canopy of Wyoming big sagebrush is the stabilizer for this community. Once it is removed from a community, it is extremely difficult to re-establish. Wyoming big sagebrush may require 25 years or greater to establish naturally, and in many cases will require outside assistance. The open raw landscape with minimal native species provides the perfect opportunity for invasive species, primarily Cheatgrass, to establish and take over a community. Drought or insects and disease serve to exacerbate the situation. Once the sagebrush is affected by the altered (shortened) fire frequency of this state due to the invasive species (primarily Cheatgrass), this community can be transitioned to the Invaded/Annuals state suddenly by prescribed burns or wildfire.

Constraints to recovery.The slow recovery of sagebrush in perfect conditions, the increased risk of fire, and the inability to eradicate cheatgrass are the constraints to recovery.

Transition T5A
State 5 to 6

Fire, Drought, Ground Disturbance, Over Use - Once a community has been compromised by a notable composition of an invasive species, stress or ground disturbance of any means can cause the invasive species to take over and dominate the site. Wildfire, extreme drought and the accompanying disease and insect damage, as well as frequent and intense use by large herbivores are the impacts most commonly seen to insight a weed infestation. Any action that reduces or damages the existing sagebrush canopy exposing the sensitive native grass population will start the transition. Drought, further disturbance or ill-planned grazing (grazing when the natives are trying to break boot and grow), will remove the competition and finish the transition.

Constraints to recovery.The difficulty to remove or eradicate, the aggressive nature, and competitive edge of cheatgrass with the added fire risk do to increasing fuel load are the constraints to recovery.

Restoration pathway R6A
State 6 to 7

Integrated Pest Management, with Seeding - Integrated pest management plan and intense weed control after and possibly before seedbed preparation will be necessary to overcome a severe weed infestation. Working the soil and preparing a seedbed at a location and using either improved varieties, native seed, or in some cases an introduced species suited for the management use intended may be the only way to overcome some invasive species. Success of re-establishing a native or desired plant community on a large scale is not documented. Small scale attempts are rated to be low and highly variable for the rate of control of most species. It is a consensus that the site in theory could be brought to a community that looks similar to an at-risk community within the reference state, but that it is not possible to reach the reference community condition once annuals have established on a site. This is due to the need to work the soil or to do seedbed preparation to seed in the native species which reduces soil stability by breaking down soil structure, and alters the hydrologic cycle by changing the infiltration and percolation rates of the soil. The alteration of the soils, the change in the plant community and the risk of re-invasion of the site will never allow it to react the same to management and environmental changes the same as a truly native community and so remains in a reclaimed state.

Transition T7A
State 7 to 6

No Use, Fire (wild or prescribed), Frequent or severe Grazing, Drought with seed source present – In the reclamation or restoration process, or after a land disturbance occurs, if no management is put into place to prevent a re-occurrence or a new infestation of weeds, the community will revert back or transition to an invaded state. Wildfire, prescribed burning, drought, or frequent and severe miss-use by large herbivores can be a source of the disturbance that either opens the canopy and/or introduces the species to the location. Extended periods of non-use creates a decadent community with a large proportion of dead growth persisting around the crown of the plants, reducing vigor and production. As the plants begin to die-back, the community becomes vulnerable to weed invasions. Opposite of the non-use scenario, it has been found that frequent or severe grazing, drought, or fire can open the canopy to invasion as well. This invasion triggers the transition to an invaded state.

Constraints to recovery.The inability to eradicate or efficiently reduce the composition of cheatgrass and other aggressive invasive weed species.