State 1
Reference

The Reference state of this ecological site consists of two potential plant communities: the Rough Fescue community and the Mixed Bunchgrass community. These are described below but are generally characterized by a tall to midstatured cool-season grass community with limited shrub production. Community 1.1 is dominated by rough fescue and is considered the reference, while Community 1.2 has a codominance of bunchgrasses and shortgrasses. These communities may meld into each other due to the varying conditions and may often exist together in a relatively small area.

Community 1.1
Rough Fescue

The Rough Fescue community is considered the Reference plant community for this ecological site. This community contains a high diversity of grasses depending on how much precipitation the site receives on average, with the majority of the grass component being cool-season grasses. Rough fescue (Festuca campestris), bluebunch wheatgrass (Pseudoroegneria spicata), and green needlegrass (Nassella viridula) are dominant. Idaho fescue (Festuca idahoensis), Sandberg bluegrass (Poa secunda), and needle and thread (Hesperostipa comata) are subdominant grass species in the community. Warm-season grasses may be present, but they are often localized to small patches in the community.

The forb community is diverse and may contain a combination of up to two dozen species. Forbs will account for 10 to 15 percent of the total above-ground biomass on the Loamy ecological site. Species synonymous with the Reference state include purple prairie clover (Dalea purpurea), prairie thermopsis (Thermopsis rhombifolia), dotted blazing star (Liatris punctata), and American vetch (Vicia americana). As precipitation increases within the Climate Subset, species such as deathcamas (Zigadenus spp.), western stoneseed (Lithospermum ruderale), old man's whiskers (Geum triflorum), and northern bedstraw (Galium boreale) may also increase.

As discussed in the Ecological Dynamics section, the natural fire regime restricted shrubs to relatively small portions of this community. Shrubs will account for less than five percent of the overall site production. Frequent shrub species include silver sagebrush (Artemisia cana), big sagebrush, shrubby cinquefoil (Dasiphora fruticosa), common snowberry (Symphoricarpos albus), white sagebrush (Artemisia ludoviciana), and winterfat (Krascheninnikovia lanata). In areas of coarse soil texture, spineless horsebrush (Tetradymia canescens) may occupy a small niche.

This state exists in areas with conservative grazing management or in areas with highly managed, intense grazing. For this community, conservative grazing management is a complex issue as rough fescue and bluebunch wheatgrass lack resistance to grazing during the critical growing season (spring). This reduces plant vigor and production if grazed in the critical growing season for more than one year out of three (Wilson et al., 1966). Rough fescue-dominated communities are also susceptible to heavy grazing during the summer months. Rough fescue communities are best suited to late-summer or dormant-season grazing (Willms et al., 1985).

Resilience management. The Rough Fescue Community is moderately resilient and will return to dynamic equilibrium following a relatively short period of stress (such as short-term drought, heavy grazing, and/or wildfire), provided there is a return of favorable or normal growing conditions and properly managed grazing. In this plant community, proper grazing management is typically short-term, with light to moderate grazing events during the growing season or moderate grazing in the dormant season.

Community 1.2
Mixed Bunchgrass

Figure 10. Rough fescue site left undisturbed by grazing and/or fire. Large clumps of rough fescue dying. Excessive litter cover is suppressing seedling recruitment. Reference plants are present but struggling.

Rough fescue, bluebunch wheatgrass, green needlegrass, and Idaho fescue share dominance in the Mixed Bunchgrass community. The growing points for rough fescue and bluebunch wheatgrass are several inches above the ground, making them very susceptible to continued close grazing, while needle and thread growing points tend to be near the plant base (Smoliak et al., 2006). Idaho fescue and needle and thread increase in composition when more palatable or less grazing-tolerant plants decrease due to improper grazing management or extended drought conditions. Other grass species, which are more tolerant to grazing and are likely to increase compared to the Rough Fescue community, include Sandberg bluegrass (Poa secunda), purple threeawn (Aristida purpurea), prairie Junegrass, western wheatgrass (Pascopyrum smithii), thickspike wheatgrass (Elymus lanceolatus), and blue grama (Bouteloua gracilis). Some increaser forb species include western yarrow (Achillea millefolium), western stoneseed (Lithospermum ruderale), spiny phlox (Phlox hoodii), scarlet globemallow (Sphaeralcea coccinea), hairy false goldenaster (Heterotheca villosa), and pussytoes (Antennaria spp.). Prairie sagewort (Artemisia frigida) also increases under prolonged drought or heavy grazing and can respond to summer precipitation.

Heavy, continuous grazing will reduce plant cover, litter, and mulch. The timing of grazing is important on this site because of the moisture limitations beyond June, especially on the drier sites. Bare ground will increase, exposing the soil to erosion. Litter and mulch will be reduced as plant cover declines. As long as rough fescue is still a dominant species in total biomass production, the site can return to the Rough Fescue community using proper grazing management and favorable growing conditions.

Idaho fescue, needle and thread, and western wheatgrass may continue to increase until they make up the majority of the species composition. It may be difficult for the site to recover to the Rough Fescue community once the rough fescue has been reduced to less than 15 percent dry weight. The risk of soil erosion increases when canopy cover decreases. As soil conditions degrade, there will be a loss of organic matter, less litter, and reduced soil fertility. Degraded soil conditions can increase the difficulty of reestablishing bluebunch wheatgrass and returning to the Rough Fescue community.

The Mixed Bunchgrass community is the at-risk plant community for this ecological site. When overgrazing continues, increaser species such as Sandberg bluegrass and needle and thread, along with increaser native forb species, will become more dominant, and this triggers the change to the Altered State or the Degraded state. Until the Mixed Bunchgrass community crosses the threshold into the Idaho Fescue community or the Invaded community, this community can be managed toward the Rough Fescue community using prescribed grazing and strategic weed control. It may take several years to achieve this recovery, depending on growing conditions, the vigor of remnant rough fescue plants, and the aggressiveness of the weed treatments.

Resilience management. The Mixed Bunchgrass community is is moderately resilient and will return to dynamic equilibrium following a relatively short period of stress (such as short-term drought, heavy grazing, and/or wildfire), provided there is a return of favorable or normal growing conditions and properly managed grazing. In this plant community, proper grazing management is typically short-term, with light to moderate grazing events during the growing season or moderate grazing in the dormant season.

Pathway 1.1A
Community 1.1 to 1.2

Rough Fescue

Mixed Bunchgrass

Midstatured bunchgrasses lose vigor with improper grazing or extended drought. When vigor declines in response to disturbances such as these, bunchgrass basal areas will decrease in size, while species with higher grazing tolerance (primarily Idaho fescue on this site) will increase in vigor and production as they access the resources previously used by decreaser bunchgrasses. The reduction in mid-statured bunchgrass composition to less than 40 percent and an increase in forb and shrub canopy cover to 15 percent indicate that the plant community has shifted to the Mixed Bunchgrass community. The Reference state has evolved under a disturbance regime that has included frequent grazing by bison and regular burning by indigenous peoples. A lack of disturbance can result in a loss of health and vigor for the dominant rough fescue. This reduced vigor is noticeable in the dead or dying plant bases that typically start in the centers of plants. In the long term, the reduced basal area of rough fescue allows for infestation by increasers and nonnative herbaceous plants. The driver for community shift 1.1A is improper grazing management or prolonged drought. Improper grazing on this ecological site is defined as grazing utilization that exceeds moderate use (50 percent grazing use), particularly during the active growing season on rough fescue-dominated sites and/or multiple grazing events of a plant without rest in the same growing season. Associated with grazing intensity is the timing of grazing. The critical grazing period for this site is late spring to early summer, or approximately boot stage on grass. Rough fescue is particularly sensitive to summer grazing, which may drive the transition to the Mixed Bunchgrass community. This shift is triggered by the loss of vigor of rough fescue and bluebunch wheatgrass. Bare ground increases in associated with prolonged drought coupled with improper grazing.

Context dependence.Drought and warmer-than-normal temperatures are known to advance plant phenology by as much as one month (Blaisdell, 1958). During drought years, plants may be especially sensitive or reach a critical stage of development earlier than expected. The Rough Fescue community may slowly transition to the Mixed Bunchgrass community regardless of management.

Pathway 1.1B
Community 1.2 to 1.1

Mixed Bunchgrass

Rough Fescue

The Mixed Bunchgrass community will return to the Rough Fescue community with proper grazing management and appropriate grazing intensity. Favorable moisture conditions will facilitate or accelerate this transition. It may take several years of favorable conditions for the community to transition back to a decreaser bunchgrass-dominated state. The increased vigor of midstatured bunchgrasses, which now account for more than 40 percent of the species composition, is the driving force behind this community shift. The trigger for this shift is the change in grazing management, which favors decreaser bunchgrasses. These triggers are generally conservative grazing management styles such as deferred or rest rotations utilizing moderate grazing (less than 50 percent grazing use) combined with favorable growing conditions such as cool, wet springs. Late-season or dormant-season grazing tends to promote rough fescue's growth patterns, which may increase the success of a grazing regime. These systems tend to promote increases in soil organic matter, which in turn promotes microfauna and increases infiltration rates. Inversely, long periods of rest at a time when this state is considered stable may not result in an increase in rough fescue, bluebunch wheatgrass, and other decreaser bunchgrasses. Long periods of rest or underutilization may actually drive the system to a lower level of stability by creating large amounts of standing biomass, dead plant caudex centers, and gaps in the plant canopy (Noy-Meir, 1973).

Context dependence.Soil and precipitation variability across this ecological site will create conditions that sites may express less rough fescue than others. Drier sites and those with increased calcium carbonates in the soil profile will express less rough fescue. Those sites may never reach the Rough Fescue community regardless of management or favorable growing conditions.

State 2
Altered

This state is distinguished by having less than 10 percent midstatured bunchgrasses by weight. It is represented by two communities that differ in the percent composition of Idaho fescue and overall production. Some native plants tend to increase in quantity under prolonged drought and/or heavy grazing practices. A few of these species may include Idaho fescue, Sandberg bluegrass, Cusick's bluegrass (Poa cusickii), scarlet globemallow, hairy false goldenaster, and prairie sagewort. Poisonous plants such as lupine (Lupinus spp.) and deathcamas (Zigadenus spp.) may also increase under these conditions.

This state is a result of extended heavy grazing, which is often combined with extended drought. Heavy grazing is defined as grazing that exceeds 50 percent utilization in a grazing season and/or multiple grazing events during critical spring growth with inadequate time between grazing events.

Community 2.1
Idaho Fescue

This plant community is a result of repeated heavy grazing disturbances that are often paired with environmental stressors such as drought or fire. The community is dominated by increaser species such as Idaho fescue, thickspike wheatgrass, western wheatgrass, oatgrass (Danthonia sp.), prairie Junegrass, and needle and thread. As the decreaser bunchgrasses reduce, these increaser grasses will fill the basal gaps, and native forbs will tend to increase as well. A slight increase in shrubs may also be seen.

Midstatured bunchgrasses comprise up to 10 percent of species composition by dry weight. The remaining midstatured bunchgrass plants tend to be scattered and low in vigor. Remnant populations of rough fescue and bluebunch wheatgrass exist under taller shrubs or within creeping juniper (Juniperus horizontalis) patches, protected from grazing animals. Increaser and invader species will be more common. Hairy false goldenaster, deathcamas, goldenrod (Solidago spp.), stonecrop, lupine, and yarrow (Achillea millefolium) are examples of increaser forbs. It is not uncommon for a minor component of invader species such as dandelion and yellow salsify to be present. This creates more competition for the midstatured bunchgrasses, making it difficult for them to quickly respond to a change in grazing management alone. Therefore, an input of energy is required for the community to return to the Reference state. Wind and water erosion may be eroding soil from the plant interspaces. Soil fertility is reduced, and soil surface erosion resistance has declined compared to the Reference state.

Long-term grazing mismanagement with continuous growing-season pressure will reduce the total productivity of the site and lead to an increase in bare ground. Suppression of fire can also promote shrub growth, increasing plant interspaces. Once plant cover is reduced, the site is more susceptible to erosion and degradation of soil properties. Soil erosion, or reduced soil fertility, will result in reduced plant production. This soil erosion, or loss of soil fertility, indicates the transition to the Altered state because it creates a threshold requiring energy input to return to the Reference state. Extended drought conditions may exacerbate the transition to the Idaho Fescue community.

This community crossed a threshold from the Reference state due to the erosion of soil, altered vegetative composition, loss of soil fertility, or degradation of soil conditions. This results in a critical shift in the ecology of the site. The effects of soil erosion can alter the hydrology, soil chemistry, soil microorganisms, and soil structure to the point where intensive restoration is required to restore the site to another state or community. Changing grazing management alone may not create sufficient improvement to restore the site if decreaser species are greatly reduced. A study suggests that with decreased grazing pressure, a needle and thread plant community did not change species composition, but the content of the soil carbon increased (Dormaar et al., 1997). It will require a considerable amount of energy to move the site back to the Reference state. This state has lost soil or vegetation attributes to the point that recovery to the Reference state will require reclamation efforts, i.e., soil rebuilding, intensive mechanical treatments, and/or reseeding.

The transition to this state could result from overgrazing and fire suppression, especially repeated early-season grazing coupled with an extensive drought. If heavy grazing continues, plant cover, litter, and mulch will continue to decrease, while bare ground will increase, exposing the soil to accelerated erosion. Litter and mulch will move off-site as plant cover declines. The Idaho Fescue community will then shift to a Rhizomatous community. Continued overgrazing will drive the community to a Degraded state. The introduction or expansion of invasive species will further drive the plant community into the Invaded state.

Community 2.2
Rhizomatous Grass

With continued mismanagement of grazing, especially coupled with prolonged drought, Idaho fescue will decrease in vigor. The bunchgrasses will decline in production as plants die or become smaller, and species with higher grazing tolerance (such as western wheatgrass and Sandberg bluegrass) will increase in vigor and production as they respond to resources previously used by the bunchgrasses. These less desirable, shorter-rooted species will become dominant, with bunchgrasses only sparsely existing on the site. Midstatured grasses such as bluebunch wheatgrass, rough fescue, Columbia needlegrass, and green needlegrass will exist within shrub canopies where they are protected from grazing animals. However, few of these plants will exist outside of the shrub canopy.

This plant community is at risk of complete invasion by Kentucky bluegrass, dandelion, cheatgrass, and yellow salsify.

Pathway 2.1A
Community 2.1 to 2.2

The driver for community shift 2.1A is continuing to overgraze. On this site, overgrazing is defined as grazing utilization of more than 60 percent and/or season-long grazing where livestock can graze regrowth. This shift is triggered by the continued loss of bunchgrass vigor, especially in the remaining Idaho fescue and needlegrasses. The rhizomatous and shortgrasses will become more competitive and dominant over the bunchgrasses. Shrub species like broom snakeweed and rabbitbrush will increase.

Context dependence.Repeated negative grazing events are required to transition from the Idaho Fescue community to the Rhizomatous Grass community. This may occur in small patches near traditional water sites or small pastures.

Pathway 2.1B
Community 2.2 to 2.1

If grazing management is implemented, Idaho fescue may regain its vigor and move toward the Idaho Fescue community. This will give grasses an advantage over invading shrubs before too much competition takes place. Since the transition from community 2.1 to community 2.2 was likely caused by repeated heavy utilization, a conservative grazing plan where utilization is reduced to at or below moderate utilization with rest or deferment is incorporated. Forage production increased by an average of 35 percent on western ranges when converting from heavy utilization to moderate utilization that is less than 50 percent (Lacey and Van Poolen, 1979). Shrub removal and favorable growing conditions can accelerate this process. A low-intensity fire or mechanical treatment could reduce shrub competition and allow for increased vigor and the reestablishment of grass species (Wambolt and Payne, 1986).

Context dependence.Sites that Idaho fescue has been removed completely may not recover to this community regardless of management. Seeding practices will be required. Favorable precipitation patterns will also be necessary.

State 3
Degraded

Degraded state lacks midstatured bunchgrasses. Sandberg bluegrass and prairie Junegrass are the dominant grasses, increaser shrubs nearly replace larger shrub species. Larger shrub species that remain are heavily hedged. This state is likely terminal and restoration will likely be impossible, unsuccessful, or require major energy inputs.

Community 3.1
Shortgrass

This state is characterized by soil surface degradation and little plant soil surface cover. Soil loss continues, and subsequent loss of soil organic matter creates conditions where native perennial grasses are reduced. Grass and forb cover may be sparse, with obvious rill erosion between plant bases. Extensive, lesser spikemoss patches may also exist.

Needle and thread and Sandberg bluegrass exist in small patches. This could occur due to overgrazing, a long-term lack of fire, or the introduction of invasive species.

In the most severe stages of degradation, there is a significant amount of bare ground, and large gaps occur between plants. Soils have the potential to erode to the point where irreversible damage occurs. This is a critical shift in the ecology of the site. Soil erosion combined with a lack of organic matter deposition due to sparse vegetation creates negative changes to the hydrology, soil chemistry, soil microorganisms, and soil structure to the point where intensive restoration is required to restore the site to another state.

The forb component shifts to being dominated by spiny phlox, and the shrub canopy cover is typically greater than 15 percent. Broom snakeweed, rabbitbrushes, prairie sagewort, and plain prickly pear cactus are dominant shrubs.

This state has lost soil or vegetation attributes to the point that recovery to the Reference state will require extensive reclamation efforts, i.e., soil rebuilding, intensive mechanical treatments, and reseeding. Grazing management practices such as rest rotations will not return this community to the Reference state without reclamation efforts.

This plant community is likely a terminal state and will not return to the Reference state due to significant barriers to restoration from degraded soil conditions and the loss of higher successional native plant species.

State 4
Invaded

The Invaded state is identified as being in the exponential growth phase of invader abundance, where control is a priority. The dominance (or relative dominance) of noxious and other hard-to-control invasive species reduces species diversity, forage production, wildlife habitat, and site protection. Even with proper grazing management or favorable growing conditions, a level of 10 percent by weight of invasive species composition by dry weight indicates that a significant energy input, such as herbicide or mechanical removal, will be required to create a shift to the grassland state. Prescriptive grazing that specifically focuses on the grazing of invasive plants can be used to manage invasive species. In some instances, carefully targeted grazing (sometimes in combination with other treatments) can reduce or maintain the species composition of invasive species.

This state differs from the Naturalized Herbaceous Invaded state in the severity of the ecological impact of the species. The species in the Invaded State are often considered noxious or to be those that, once present, are difficult to control and almost impossible to eradicate, such as cheatgrass (Bromus tectorum) or North Africa grass (Ventenata dubia).

Community 4.1
Invaded

Communities in this state may be structurally indistinguishable from those in the reference state except that invasive or noxious species have reached 10 percent of species composition by dry weight. Although there is no research for this threshold, it is estimated to be the point in the invasion process following the lag phase (Masters and Sheley, 2001). For aggressive invasive species (such as spotted knapweed), the threshold could be as low much lower. Early in the invasion process, there is a lag phase where the invasive plant populations remain small and localized for long periods before expanding exponentially (Hobbs and Humphries, 1995).

Production in the invaded community may vary greatly based on the severity of the invasion and potential subsequent effects on species composition. A site dominated by Kentucky bluegrass or spotted knapweed, where soil fertility and chemistry remain near reference, may have production near that of the reference community. A site with degraded soils and a cheatgrass infestation may produce only 10 to 20 percent of the Reference state.

Once invasive species dominate the site, either in species composition by weight or in their impact on the community, the threshold has been crossed to the Invaded state. As invasive species such as spotted knapweed, cheatgrass, and leafy spurge become established, it becomes very difficult to eradicate them. Therefore, considerable effort should be placed into preventing plant communities from crossing the threshold into the Invaded state through early detection and proper management. Preventing new invasions is by far the most cost-effective control strategy and typically places an emphasis on education. Control measures used on the noxious plant species impacting this ecological site include chemical, biological, and cultural (burning, mowing, and cutting) control methods. The best success has been found with an integrated pest management (IPM) strategy that incorporates one or several of these options along with education and prevention efforts. (DiTomaso, 2000).

State 5
Naturalize Herbaceous Invaded

Figure 11. Rough fescue rangeland with yellow sweet clover in background.

This state is one that has been invaded by plants that are not generally considered to have the same extreme impact on this ecological site as those in the Invaded state, though they can pose a negative impact on this ecological site, particularly on the hydrologic functions. This list of species is often introduced by encroachment from neighboring cultivated pastures such as Kentucky bluegrass (Poa pratensis), Timothy (Phleum pratense), smooth brome (Bromus inermis), and crested wheatgrass (Agropyron cristatum). It is not uncommon for introduced forbs to invade via wind-blown seeds such as dandelion (Taraxacum spp.), sweetclover (Melilotus officinalis), and yellow salsify (Tragopogon dubius).

This state may resemble the Reference state in structure or could be completely invaded. These naturalized plants have a dry weight of more than 10 pounds per acre or a canopy cover of more than two percent.

Community 5.1
Naturalized Invaded

A common occurrence in this LRU is the invasion of herbaceous plants that are weeds, though they are considered, by many, to be more of a nuisance than an actual threat to rangeland conditions. Kentucky bluegrass, smooth brome, crested wheatgrass, Timothy, sweetclover, dandelions, and yellow salsify are common naturalized invasive species.

Common naturalized nonnative grasses often encroach into rangeland that isn't in the Reference state. They have taken root in an open area of bare ground or in between plants via rhizomes. Often, these grasses are palatable to all classes of livestock and many native mammals, so they are not actively controlled by many land managers. Common naturalized grasses are typically shallow-rooted, causing site stability issues in the long term. Naturalized grass such as crested wheatgrass dominated sites express reduced soil nitrogen and carbon (Christian and Wilson, 1999).

As with naturalized grasses, invasive weedy forbs pose the same threat to native rangelands. The prolific seed producers will occupy the tiniest bit of bare ground and produce thousands of seeds. In the case of the dandelion and yellow salsify, the plants are generally small in stature, but the large taproot and spreading leaves outcompete many native species for the limited resources available. Sweetclover can occupy thousands of acres of land, and as a biennial, it takes advantage of early season soil moisture and sunlight and grows to a large stature, effectively outcompeting native plants for space and sunlight.

While not species of immediate concern, these species pose a real danger to the overall health of the rangeland and do have major impacts on rangeland health, specifically by occupying space typically reserved for native plants (Vaness and Wilson, 2007). In the long term, this will mean fewer native plants on the landscape, causing issues with hydrology and site stability, which will affect the grazeability of a site and its suitability as a wildlife habitat.

These species can be controlled with simple methods. Naturalized grasses are susceptible to fire and repeated prescribed fire treatments have proven to be an effective control. Targeted grazing alone will not control for naturalized grasses. Naturalized forbs in this state can be controlled with broadleaf herbicides. It is important to note that these plants are often interspersed with native forbs, so this method would need to be reserved for a large invasion or applied with a wand sprayer for spot applications. Tall forbs such as sweetclover can be easily controlled via mowing or haying, particularly when done before seed production. Livestock will actively graze this tall forb, although the hay produced from sweetclover can be toxic.

State 6
Converted Cropland

The Loamy ecological site has been, extensively, converted to Annual Crop or Pasture with dominant species being introduced for grain or forage production. The conversion of native rangeland required intensive tillage for this state to exist.

Community 6.1
Annual Crop

The Annual Crop community is common on this ecological site as the soil pH, water holding capacity, and inherent soil organic matter tend to be favorable to annual cropping. Barley, oats, and wheat are the most common. If irrigation is available, this community is extremely productive. Besides small grains, the site is capable of producing a wide variety of crops, including corn silage, seed potatoes, pumpkins, sunflowers, and other specialty crops.

Long-term annual cropping can destroy soil aggregation, deplete organic matter, and alter pH, so a conservative crop management system will need to be applied to prevent degradation of the site.

The Rocky Mountain Front LRU is particularly susceptible to wind erosion due to the frequent Chinook winds that occur in winter when soil surface cover is lowest. Common cropping methods such as no-till, reduced-till, and cover cropping significantly reduce the potential for wind erosion.

Community 6.2
Forage Crop

The Forage Crop community is mechanically harvested and baled for feed for livestock. Nutrients are removed from the site, and long-term inputs are required to maintain productivity. This often requires a maintenance cycle of annual cropping for one to three years before the site is planted back to hay. In this LRU, the primary species is alfalfa with one or more species of introduced grasses such as pubescent or intermediate wheatgrass (Thinopyrum intermedium), smooth brome (Bromus inermis), meadow brome (Bromus biebersteinii), orchardgrass (Dactylis glomerata), or Timothy (Phleum pratense). The Loamy ecological site is capable of producing high amounts of quality hay, especially with the addition of irrigation.

Community 6.3
Pasture

The Pasture Community is very common within the Converted Cropland State. It consists primarily of long-term herbaceous crop planted for grazing animals. Management styles are extremely variable. Vegetation is considered permanent though stands may see brief periods of tillage/cropping as stands age or as management goals change. The Pasture Community differs from the Forage Crop Community by being managed for grazing animals. Their excrement remains on the site for nutrient cycling while the Forage Crop Community nutrients are removed from the site.

Pathway P6.1
Community 6.1 to 6.2

The Annual Crop community is planted to the Forage Crop community. Permanent herbaceous forage is harvested, mechanically, and removed from the field to be fed to livestock.

Context dependence.The site needs to have soil conditions conducive to farming practices prior to conversion to the permanent cover for grazing. Typically if the site has been used for the Annual Crop community, there are no major limitations for this transition.

Pathway P6.3
Community 6.1 to 6.3

The Annual Crop community is planted to permanent herbaceous cover for the intended purpose of grazing livestock. Introduced grasses and forbs dominate the site.

Context dependence.The site needs to have soil conditions conducive to farming practices prior to conversion to the permanent cover for grazing. Typically if the site has been used for the Annual Crop community, there are no major limitations for this transition.

Pathway P6.2
Community 6.2 to 6.1

The Forage Crop community is removed and planted to the Annual Crop community. Different methods may be used for the removal of the Forage Crop community; however, mechanical tillage is often required to reduce competition for the species that may be planted in the Annual Crop community. In the Rocky Mountain Foothills LRU, the most common species include barley, wheat, and oats but may include a variety of other annual crops.

Context dependence.The Forage Crop community conversion to the Annual Crop community typically has few site restrictions that prevent the transition. Favorable seasonal precipitation aids in the success of conversion.

Pathway P6.4
Community 6.3 to 6.1

The Pasture community is converted to the Crop community as a result of extensive tillage and seeding of a crop. Often this is a small grain such as barley, wheat, or oats.

Context dependence.The Pasture community conversion to the Annual Crop community typically has few site restrictions that prevent the transition. Favorable seasonal precipitation aids in the success of conversion.

Transition T1A
State 1 to 2

Reference

Altered

The Reference state transitions to the Altered state if mid-statured bunchgrasses decrease to less than 10 percent by dry weight or if bare ground cover increases beyond 10 percent. The driver for this transition is the loss of taller bunchgrasses, which creates open areas in the plant canopy with bare soil. Soil erosion results in decreased soil fertility, driving transitions to the Altered state. There are several other key factors signaling the approach of transition T1A, such as an increase in physical soil crusting, a decrease in the cover of biological crusts, a decrease in soil surface aggregate stability, and evidence of erosion, including water flow patterns, pedestals, and litter movement.

Constraints to recovery.The lack of deep-rooted bunchgrasses will prevent recovery to the Reference state without inputs such as seeding and mulching. Favorable growing conditions are necessary to facilitate restoration to the Reference state.

Context dependence.The transition to the Altered state is primarily driven by negative grazing events, however, prolonged drought may expedite this transition. If present, intense fire may also create conditions where the midstatured bunchgrasses are removed. Intense fire is often paired with hot, dry summer conditions which damage the caudex of these bunchgrasses.

Transition T1B
State 1 to 3

The Reference state transitions to the Degraded state when rough fescue and bluebunch wheatgrass are completely removed from the plant community. Idaho fescue is subdominant (or often absent) to needle and thread and short-statured bunchgrasses such as Sandberg bluegrass and Cusick's bluegrass. The trigger for this transition is the loss of most mid-statured bunchgrasses, which creates open spaces with bare soil. Soil erosion as a result of increased bare ground and shallow roots decreases soil fertility, driving transitions to the Degraded state. There are several other key factors signaling the approach of Transition T1B: an increase in soil physical crusting, a decrease in biological crusts, a decrease in soil surface aggregate stability, and/or evidence of erosion, including rills, water flow patterns, pedestals, and litter movement. The drivers for this transition are improper grazing management, intense or repeated fires, and/or heavy human disturbance. Rapid transition to the Degraded state is generally realized where livestock are confined to small pastures for long periods of time, such as feeding areas, horse pastures, and bull lots. Degradation may be so extreme that traditional restoration methods may not be successful and require extensive mechanical and financial inputs.

Constraints to recovery.The lack of deep-rooted bunchgrasses will prevent recovery to the Reference state without inputs such as seeding and mulching.

Context dependence.The transition to the Degraded state is primarily driven by negative grazing events, however prolonged drought may expedite this transition. If present, intense fire may also create conditions where the midstatured bunchgrasses are removed. Intense fire is often paired with hot, dry summer conditions which damage the caudex of these bunchgrasses.

Transition T1C
State 1 to 4

Reference

Invaded

Healthy plant communities are the most resistant to invasion. However, sometimes, regardless of grazing management, without some form of active weed management (chemical, mechanical, or biological control), the Reference state can transition to the Invaded state in the presence of aggressive invasive species such as spotted knapweed, leafy spurge, and cheatgrass. The Rocky Mountain Front Foothills LRU tends to resist invasion, though recent dry climate cycles, repeated heavy grazing, or intense human activities can open the interspaces of the Reference state and allow for encroachment. Long-term stress conditions for native species (e.g., overgrazing, drought, and fire) accelerate this transition. If populations of invasive species reach critical levels, the site transitions to an Invaded state. The trigger for this transition is the presence of aggressive invasive species, with the composition of invasive species by dry weight approaching 10 percent.

Constraints to recovery.The removal of invasive species requires significant inputs of time, weed management, and capital. Many invasive species such as cheatgrass, spotted knapweed, and leafy spurge are challenging to control and may always be present on a site, once established. The level of invasion needs to be minimal or the species must be easy to control to return to the Reference state

Context dependence.Invasive species vary in aggressiveness and ease of control. Some species such as yellow salsify may have minimal impact on an ecological site while an aggressive species such as cheatgrass may begin to affect the site at a very low composition. Drought, fire return interval, and grazing patterns may influence the speed at which a site will be invaded.

Transition T1D
State 1 to 5

Reference

Naturalize Herbaceous Invaded

Healthy plant communities are most resistant to invasion, but sometimes the Reference state can transition to the Naturalized Herbaceous Invaded state in the presence of herbaceous invasive species. Non-native plants take advantage of small gaps in the plant community and prolific seed producers. The list of species includes, but is not limited to, Kentucky bluegrass, Timothy, smooth brome, dandelion, yellow salsify, and yellow sweet clover. Rough fescue communities tend to resist invasion, though dry climate cycles, heavy grazing, or intense human activities can open the interspaces of the Reference state and allow for encroachment. Long-term stress conditions for native species (e.g., overgrazing, drought, and fire) accelerate this transition. If populations of invasive species reach critical levels, the site transitions to the Naturalized Herbaceous Invaded state. These naturalized plants are present in quantities greater than a trace amount by dry weight or greater than two percent canopy cover.

Constraints to recovery.Naturalized grasses are increasingly hard to control and may always be present in a low amount once established.

Context dependence.This site often exists land that has been planted to hay or pasture. Small gaps between native plants offer an opportunity for these competitive species to establish.

Transition T1E
State 1 to 6

Mechanical tillage converts rangeland to production cropland with intent of producing small grains (primarily wheat, barley, oats, and oilseed) or forage crops such as pasture or hay for livestock.

Context dependence.Some sites may not have been converted to production cropland due to rock fragments, slope, or other site conditions such as soil pH.

Restoration pathway R2A
State 2 to 1

Altered

Reference

The Altered state has lost soil or vegetation attributes to the point that recovery to the Reference state requires reclamation efforts such as soil rebuilding, intensive mechanical treatments, cultural treatments, and revegetation. Examples of mechanical treatment may be brush control, while cultural treatments may include prescribed grazing, targeted brush browsing, or prescribed burning. Grazing practices that promote rough fescue are primarily light to moderate grazing during the critical season (late June through July) or dormant season of moderate use. Heavy utilization may not have immediate negative impacts, though grazing should match the species composition of the site prior to exceeding moderate utilization (Dormaar and Willms, 1998). Low-intensity prescribed fires can be used to reduce competitive increaser plants such as Idaho fescue, needle and thread, and Sandberg bluegrass. A low-intensity fire will also reduce shrubby cinquefoil populations, if present. In areas with the potential for annual grass infestations, fire should be carefully planned or avoided. The drivers for this restoration pathway are reclamation efforts along with grazing management.

Context dependence.If midstatured bunchgrasses exist, a grazing management using light-intensity grazing along with time for recovery combined with favorable growing conditions may facilitate the restoration back to the Reference state.

Transition T2A
State 2 to 3

As improper grazing continues, the vigor of bunchgrasses will decrease. The shorter grasses and shrubs will increase towards the Degraded state. In this state, improper grazing management is defined as grazing events that exceed moderate grazing (40 to 50 percent grazing use), a grazing season that exceeds half of the growing season, and/or grazing events that consume plant regrowth in the same growing season. Highly managed grazing events that exceed moderate grazing levels for short timeframes are generally not included in this definition due to the increased rest periods between these grazing events. Additionally, prolonged drought will provide a competitive advantage to shrubs, allowing them to become co-dominant with grasses. Shrub canopies may increase, though they will express low growth forms as a result of browsing by livestock. Mat-forming forbs and lesser spikemoss will also increase. Key transition factors include an increase in native shrub canopy cover, a decrease in bunchgrass production, a decrease in total plant canopy cover and production, an increase in mean bare patch size, an increase in soil crusting, a decrease in cryptobiotic crust cover, a decrease in soil aggregate stability, and/or evidence of erosion, such as water flow patterns and litter movement.

Constraints to recovery.Removal of all midstatured grasses will require reseeding and soil rebuilding efforts to restore to the Altered state

Context dependence.Exceptionally dry conditions may expedite the transition from the Altered state. The loss of soil organic matter may increase the odds of invasion by annual grasses.

Transition T2B
State 2 to 4

Altered

Invaded

Invasive species can occupy the Altered state and drive it to the Invaded state. The Altered state is at risk if invasive seeds and/or other viable material are present. More than 10 percent of the dry weight of invasive species is the driving force behind this transition. The trigger is the presence of seeds and/or other viable material from invasive species.

Constraints to recovery.The addition of aggressive non-native plants could completely prevent restoration to the Altered state. Significant capital and time will be necessary.

Context dependence.The condition of the Invaded state must resemble that of the Altered state to be restored to the Altered state. The kind and amount of invasive species may also affect the ability of the site to be restored.

Transition T2C
State 2 to 5

Altered

Naturalize Herbaceous Invaded

Invasive species can occupy the Altered state and drive it to the Naturalized Herbaceous Invaded state. The Altered state is at risk of invasion due to increased bare ground and basal gaps, which allow for ease of establishment. This transition is being driven by a trace (10 pounds of per acre) or more than two percent canopy cover of herbaceous naturalized plants. The trigger is the presence of seeds and/or other viable material from invasive species.

Constraints to recovery.Naturalized grasses are increasingly hard to control and may always be present in a low amount once established.

Context dependence.This site often exists land that has been planted to hay or pasture. Small gaps between native plants offer an opportunity for these competitive species to establish.

Transition T2D
State 2 to 6

Mechanical tillage converts rangeland to production cropland with intent of producing small grains (primarily wheat, barley, oats, and oilseed) or forage crops such as pasture or hay for livestock.

Constraints to recovery.Removal of native vegetation and tilling of the soil will require reseeding of the site. In some cases, the Converted Cropland state is left unmanaged and pioneer species may slowly begin to revegetate the site.

Context dependence.Sites converted to the Converted Cropland state are often gentle sloping with minimal rock fragments within the soil. Newly converted sites are frequently located nearby other converted lands.

Restoration pathway R3A
State 3 to 1

The Degraded state has lost soil or vegetation attributes to the point that recovery to the Reference state will require reclamation efforts such as soil rebuilding, intensive mechanical treatments, and/or revegetation. Studies suggest that mulch with a high carbon-to-nitrogen ratio, such as wood chips or bark in low-moisture scenarios, can be beneficial for the slow mobilization of plant-available nitrogen (Whitford et al., 1989). Biochar may also be added to the system to improve soil organic carbon (SOC), which should improve cation exchange capacity (CEC), microbial activity, and hydrologic conductivity (Stavi, 2012). The drivers for the restoration pathway are the removal of increaser species, restoration of native bunchgrass species, persistent management of invasives and shrubs, and proper grazing management. Without continued control, invasive and shrub species are likely to return (probably rapidly) due to the presence of seeds and/or other viable material such as rhizomes or stolons in the soil and management-related increased soil disturbance.

Context dependence.The Degraded state lacks the midstatured bunchgrass of the Reference state and may be affected by soil loss. Restoration methods will vary based on soil conditions but will require significant inputs to add soil organic matter as well as seeding the site. This site may have lost so much soil that it will never return to the Reference state.

Restoration pathway R3B
State 3 to 2

Since the deep-rooted bunchgrass plant community has been removed, restoration to the Altered State is unlikely unless a seed source is available. If a sufficient amount of bunchgrass remains on the site, chemical application and/or biological control, in conjunction with proper grazing management, can reduce the number of shrubs and invasive species and restore the site to the Rhizomatous Grass community. Grazing management strategies that follow light grazing and allow for long periods of rest will allow for limited recovery of remaining bunchgrasses. However, grazing management alone may not directly result in restoration. Restoration methods, such as reseeding, will be necessary. Low-intensity fire can be utilized to reduce shrub competition and allow the reestablishment of grass species. Caution must be used when considering fire as a management tool on sites with fire-tolerant shrubs such as rubber rabbitbrush, as these shrubs will sprout after a burn. Some shrubs, like broom snakeweed and prairie sagewort, may or may not re-sprout depending on conditions (Tirmenstein, 1999).

Context dependence.The Degraded state lacks the midstatured bunchgrass of the Altered state and may be affected by soil loss. Restoration to the Altered state may require soil rebuilding practices as well as seeding of native species.

Transition T3A
State 3 to 4

The Degraded state is particularly susceptible to invasion by weeds, which drives it to the Invaded state. The Degraded state is at risk of this transition occurring if invasive seeds or viable material are present. The driver for this transition is the presence of critical population levels of invasive species. The trigger is the presence of seeds or viable material from invasive species. This state has sufficient bare ground that the transition could occur simply due to the presence or introduction of invasive seeds or viable material. This is particularly true of aggressive invasive species such as spotted knapweed and cheatgrass. This transition could be assisted by overgrazing (failure to adjust stocking rate to declining forage production), a long-term lack of fire, high-intensity fire, or an extensive drought.

Constraints to recovery.The Degraded state has shallow-rooted plants which affect its ability to utilize precipitation and often has reduced litter cover which also affects soil moisture. Reduced soil nutrients from erosion may affect the site's ability to recruit native plants.

Context dependence.Favorable moisture is necessary to facilitate restoration. The Degraded state has reduced soil organic matter as well as shallow-rooted plants which affects the site's infiltration rates and ability to store moisture. The reestablishment of native species is greatly reduced by these soil conditions.

Transition T3B
State 3 to 5

The Degraded state is particularly susceptible to invasion by weeds, which drives it to the Naturalized Herbaceous Invaded state. The Degraded state is at risk of invasion due to increased bare ground and basal gaps, which allow for ease of establishment. This transition is being driven by 10 pounds per acre or more than two percent of the canopy cover of herbaceous naturalized plants. The trigger is the presence of seeds and/or other viable material from invasive species.

Constraints to recovery.Naturalized grasses are increasingly hard to control and may always be present in a low amount once established.

Context dependence.This site often exists near land that has been planted to hay or pasture. Small gaps between native plants offer an opportunity for these competitive species to establish.

Transition T3C
State 3 to 6

Mechanical tillage converts rangeland to production cropland with intent of producing small grains (primarily wheat, barley, oats, and oilseed) or forage crops such as pasture or hay for livestock.

Constraints to recovery.Removal of native vegetation and tilling of the soil will require reseeding of the site. In some cases, the Converted Cropland state is left unmanaged and pioneer species may slowly begin to revegetate the site.

Context dependence.Sites converted to the Converted Cropland state are often gentle sloping with minimal rock fragments within the soil. Newly converted sites are frequently located nearby other converted lands.

Restoration pathway R4A
State 4 to 1

Invaded

Reference

Restoring the Invaded state to the Reference state requires a significant energy input. The drivers for the restoration pathway are the removal of invasive species, restoration of native bunchgrass species, persistent management of invasive species, and proper grazing management. Without continued control, invasive species are likely to return (probably rapidly) due to the presence of seeds and/or other viable material in the soil and management practices that increase soil disturbance. Sites that have transitioned from the Degraded state to the Invaded state may be severely lacking in soil and vegetative properties that will allow for restoration to the Reference state. Hydrologic function damage may be irreversible, especially with accelerated gully erosion.

Context dependence.The Invaded state must have a plant community similar to one of those in the Reference state. Without midstatured bunchgrasses present, significant inputs such as reseeding will be necessary to facilitate this restoration.

Restoration pathway R4B
State 4 to 2

Invaded

Altered

If invasive species are removed before remnant populations of bunchgrass have been drastically reduced, the Invaded state can return to the Altered state. The driver for the reclamation pathway is weed management with possible reseeding. Continued Integrated Pest Management (IPM) will be required as many of the invasive species that can occupy the Invaded State have extended dormant seed life. The trigger is invasive species control.

Context dependence.The Invaded state must have a plant community similar to one of those in the Altered state. Without those species present, significant inputs such as reseeding will be necessary to facilitate this restoration.

Restoration pathway R4C
State 4 to 3

If invasive species are removed, the site could return to the Degraded state. Without sufficient remnant populations of preferred plants, the Invaded state is not likely to return to any of the other states. The driver for the reclamation pathway is weed management without reseeding. The trigger is invasive species control. Invading species cause a significant increase in soil loss due to a lack of ground cover (Lacey et al., 1989).

Context dependence.The Invaded state must have a plant community similar to one of those in the Degraded state. Without those species present, significant inputs such as reseeding will be necessary to facilitate this restoration.

Transition T4D
State 4 to 5

Invaded

Naturalize Herbaceous Invaded

If noxious and aggressive invasive species are removed, the site could return to the Naturalized Herbaceous Invaded state. Without sufficient remnant populations of preferred plants, the Invaded state is not likely to return to any of the other states. The driver for the reclamation pathway is weed management without reseeding. The trigger is invasive species control. Invading species cause a significant increase in soil loss due to a lack of ground cover (Lacey et al., 1989). An Integrated Pest Management (IPM) Plan will be necessary to maintain and improve this state and any other state within this ecological site.

Context dependence.The Invaded state must have a plant community similar to one of those in the Naturalized Herbaceous Invasive state. Without those species present, significant inputs such as reseeding will be necessary to facilitate this restoration. Continued pest management such as herbicide application or targeted grazing will be necessary to maintain or remove invasive weeds.

Transition T4B
State 4 to 6

Mechanical tillage converts rangeland to production cropland with intent of producing small grains (primarily wheat, barley, oats, and oilseed) or forage crops such as pasture or hay for livestock.

Restoration pathway R5A
State 5 to 1

Naturalize Herbaceous Invaded

Reference

The conditional return to the Reference state requires that the plant population must resemble that of the Reference communities with only the addition of these trace amounts of naturalized plants. If the plant community closely resembles that of the Altered state or Degraded state, then other restoration pathways will be necessary to return to the Reference state. Restoration of the Naturalized Herbaceous Invaded state to the Reference state requires substantial energy input. The drivers for the restoration pathway are the removal of invasive species, restoration of native bunchgrass species, persistent management of invasive species, and proper grazing management. Without continued control, invasive species are likely to return (probably rapidly) due to the presence of seeds and/or other viable material in the soil and management practices that increase soil disturbance. The forb species present in this state tend to be susceptible to readily available conventional herbicide treatments. Application methods must be controlled so as not to affect the native forbs that are common in this state. Mowing herbaceous forbs such as sweet clover or sainfoin is a successful method of control. Caution should be taken to ensure this occurs before seed is set to reduce the risk of Naturalized grasses in this state can be hard to eradicate especially once established (Vaness and Wilson, 2007). They are often palatable to livestock and reproduce by rhizome. Repeated spring fires, specifically in the month of May, have proven to be an effective control method in conjunction with rest from grazing animals (Abrams and Hulbert, 1987).

Restoration pathway R5B
State 5 to 2

Naturalize Herbaceous Invaded

Altered

The conditional return to the Altered state is that the plant population must resemble that of the Altered state with only the addition of these trace amounts of naturalized plants. If the plant community closely resembles that of the other states within this ecological site, then other restoration pathways will be necessary to return to the Altered State. If restoration of this site to the Reference state is desired, additional restoration methods will be necessary, such as the implementation of grazing management as well as the possibility of requiring reseeding of native plants. Restoration of the Naturalized Herbaceous Invaded state to the Altered state requires substantial energy input. The drivers for the restoration pathway are the removal of invasive species, persistent management of invasive species, and proper grazing management. Without continued control, invasive species are likely to return (probably rapidly) due to the presence of seeds and/or other viable material in the soil and management practices that increase soil disturbance. The forb species present in this state tend to be susceptible to readily available conventional herbicide treatments. Application methods must be controlled so as not to affect the native forbs that are common in this state. Mowing herbaceous forbs such as sweet clover or sainfoin is a successful method of control. Caution should be taken to ensure this occurs before seed is set to reduce the risk of dispersing seed. Naturalized grasses in this state can be hard to eradicate especially once established (Vaness and Wilson, 2007). They are often palatable to livestock and reproduce by rhizome. Repeated spring fires, specifically in the month of May, have proven to be an effective control method in conjunction with rest from grazing animals (Abrams and Hulbert, 1987).

Transition T5A
State 5 to 6

Mechanical tillage converts rangeland to production cropland with intent of producing small grains (primarily wheat, barley, oats, and oilseed) or forage crops such as pasture or hay for livestock.

Constraints to recovery.Recovery to this state will require reseeding of native species with some naturalized herbaceous species present.

Context dependence.Restoration to the Naturalized Herbaceous Invaded state is uncommon. Typically the Converted Cropland state will remain in production until the site is restored to native vegetation.

Restoration pathway R6A
State 6 to 1

Restoration returns the Converted Cropland state to Reference state. Significant input may be necessary to remove competitive introduced species such as extensive tillage, nonselective herbicide application or a combination of the two. After competitive vegetation is removed or terminated, seeding of the site may occur. A successful restoration can be hard to distinguish from a truly native rangeland system though hydrologic and biotic functions of the system may not be fully restored due to soil modifications from tillage.

Context dependence.The Converted Cropland state will require seedbed preparation and seeding to recover the site to the Reference state. Time and favorable precipitation are required for success.