Land use 1
Rangeland

Site is native rangeland that has not been been modified by mechanical manipulations.

State 1.1
Bunchgrass State

The Bunchgrass State is considered the Reference State of this ecological site. The state consists of two known potential plant communities, the Bluebunch Community and the Mixed Bluebunch Community. These are described below but are generally characterized by a mid-statured, cool-season grass community with limited shrub production. Community 1.1 is dominated by bluebunch wheatgrass and is considered the reference, while Community 1.2 has a codominance of bluebunch and needle and thread with an increase in green rabbitbrush and Wyoming big sagebrush. These communities may meld into each other due to the varying conditions that occur in Southwest Montana, particularly during dry cycles where the needle and thread growth cycle takes better advantage of the limited moisture.

Community 1.1.1
Bluebunch Community

In this Reference Plant Community, bluebunch wheatgrass (Pseudoroegneria spicata), green needlegrass (Nassella viridula), and needle and thread (Hesperostipa comata) are typically dominant. Basin wildrye and rough fescue may also be present. Shrub species (big sagebrush, fringed sagewort, and broom snakeweed) remain a minor part of the community. In areas where the soil texture is coarser, spineless horsebrush (Tetradymia canescens) may occupy a small niche. Sandberg bluegrass (Poa secunda) and dryland sedges are also common. This state occurs on this Loamy site in areas with proper livestock grazing or in areas with little or no grazing pressure. Bluebunch wheatgrass lacks resistance to grazing during the critical growing season (spring) and will decline in vigor and production if grazed in the critical growing season more than one year in three (Wilson et al. 1960). The Bunchgrass State is moderately resilient and will return to dynamic equilibrium following a relatively short period of stress (such as drought or short-term improper grazing), provided a return of favorable or normal growing conditions and properly managed grazing. As discussed in the Ecological Dynamics section, the natural fire regime restricted shrubs to relatively small portions of Reference Plant Community 1.1. Shrub species present may include basin big sagebrush (Artemisia tridentata ssp. tridentata), Wyoming big sagebrush, winterfat, tarragon (Artemisia drucunculus), and fringed sagewort. Infrequent fire probably maintained big sagebrush communities as open, seral stands of productive herbaceous species with patches of big sagebrush.

Resilience management. Prescribed Grazing, Prescribed Burning, Brush Management, Pest Management

Community 1.1.2
Mixed Bunchgrass Community

Needle and thread, western wheatgrass (Pascopyrum smithii), and thickspike wheatgrass (Elymus lanceolatus) tolerate grazing pressure better than bluebunch wheatgrass, rough fescue, and green needlegrass. The growing point of these grasses is several inches above the ground, making them very susceptible to close grazing (Smoliack et al., 2006), while needle and thread and rhizomatous wheatgrass growing points tend to be near the plant base. When more palatable and less grazing-tolerant plants decline due to poor grazing management, the species composition of rhizomatous wheatgrasses and needle and thread increases. The grazing tolerant grasses and bluebunch wheatgrass share dominance in the Mixed Bunchgrass Community (1.2). Other grass species, which are more tolerant to grazing and are likely to increase in number compared to the Reference Plant Community, include Sandberg bluegrass (Poa secunda), prairie Junegrass, and blue grama (Bouteloua gracilis).  Increaser forbs include western yarrow, Hood's phlox (Phlox hoodii), scarlet globemallow (Sphaeralcea coccinea), hairy goldenaster (Heterotheca villosa), and pussytoes (Antennaria spp.). Fringed sagewort (Artemisia frigida) is a shrub that also increases under prolonged drought or heavy grazing and can respond to precipitation that falls in July and August. Heavy, continuous grazing will reduce plant cover and litter. 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 bluebunch wheatgrass is still a dominant species in total biomass production, the site can be returned to the Bluebunch Wheatgrass Community (Pathway 1.2A) under proper grazing management and favorable growing conditions. Needle and thread and western wheatgrass will continue to increase until they make up the majority of the species composition. Once bluebunch wheatgrass has been reduced to less than 20 percent of the community, it may be difficult for the site to recover to the Reference Plant Community (1.1). The risk of soil erosion increases when canopy cover decreases. As soil conditions degrade, there will be a loss of organic matter, reduced litter, and reduced soil fertility. Degraded soil conditions increase the difficulty of reestablishing bluebunch wheatgrass and returning to the Reference Community (1.1). The Mixed Bunchgrass Community (1.2) is the at-risk plant community for this ecological site. When overgrazing continues, increaser species such as needle-and-thread and native forb species will become more dominant, and this triggers the change to the Altered State (2) or the Degraded State (3). Until the Mixed Bunchgrass Community (1.2) crosses the threshold into the Needle and Thread Community (2.1) or the Invaded Community (4.1), this community can be managed toward the Bluebunch Wheatgrass Community (1.1) using prescribed grazing and strategic weed control. It may take several years to achieve this recovery, depending on growing conditions, the vigor of remnant bluebunch wheatgrass plants, and the aggressiveness of the weed treatments.

Resilience management. prescribed grazing, brush management, pest management, prescribed fire

Pathway 1.1a
Community 1.1.1 to 1.1.2

Bluebunch wheatgrass loses vigor with improper grazing or extended drought. When vigor declines enough for plants to die or become smaller, species with higher grazing tolerance (in this ecological site, that would be needle and thread) increase in vigor and production as they access the resources previously used by bluebunch wheatgrass. The reduction in bluebunch wheatgrass species composition by weight to less than 50 percent indicates that the plant community has shifted to the Mixed Bunchgrass Community (1.2). The driver for community shift 1.1A is improper grazing management or prolonged drought. This shift is triggered by the loss of vigor of bluebunch wheatgrass, soil erosion, or prolonged drought coupled with improper grazing. Blaisdell (1958) stated that drought and warmer-than-normal temperatures are known to advance plant phenology by as much as one month. During drought years, plants may be especially sensitive or reach a critical stage of development earlier than expected. Since needle and thread normally seeds out in June and bluebunch wheatgrass in July, this should be taken into consideration when planning grazing management.

Pathway 1.2b
Community 1.1.2 to 1.1.1

The Mixed Bunchgrass Community (1.2) will return to the Bluebunch Wheatgrass Community (1.1) 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 bluebunch dominated state. The driver for this community shift (1.2A) is the increased vigor of bluebunch wheatgrass, to the point that it represents more than 50 percent of species composition. The trigger for this shift is the change in grazing management favoring bluebunch wheatgrass. These triggers are generally conservative grazing management styles such as deferred or rest rotations utilizing moderate grazing (less than 50 percent use) combined with favorable growing conditions such as cool, wet springs. These systems tend to promote increases in soil organic matter, which promotes microfauna and can increase infiltration rates. Inversely, long periods of rest at a time when this state is considered stable may not result in an increase in bluebunch wheatgrass, and it has been suggested (Noy-Meir 1975) that these 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.

State 1.2
Altered State

This state is characterized by having less than 15 percent bluebunch wheatgrass by dry weight. It is represented by two (2) communities that differ in the percent composition of needle and thread, production, and soil degradation. Production in this state can be similar to that in the Bunchgrass State (1). Some native plants tend to increase under prolonged drought and heavy grazing practices. A few of these species may include needle and thread, Sandberg bluegrass, scarlet globemallow, hairy goldenaster, and fringed sagewort.

Characteristics and indicators. Less than 15% bluebunch wheatgrass Increase in short stature grasses Increase in bare ground (near 35%)

Resilience management. Conservative grazing management, Integrated Pest Management, time

Community 1.2.1
Mixed Grass/Sagebrush Community

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 (2) because it creates a threshold requiring energy input to return to the Bunchgrass State (1). Transition to the Mixed Grass/Sagebrush Community (2.1) may be exacerbated by extended drought conditions. Needle and thread dominates the Mixed Grass/Sagebrush Community (2.1). Bluebunch wheatgrass makes up less than 15 percent of the species composition by dry weight, and the remaining bluebunch wheatgrass plants tend to be scattered and low in vigor. Invasive species will become more common. Hairy goldenaster, Missouri goldenrod, stonecrop, and yarrow are examples of increaser forbs. It is not uncommon for a minor component of invader species such as dandelion and yellow salsify (Tragapogon dubius) to be present. This creates more competition for bluebunch wheatgrass and makes it difficult for bluebunch wheatgrass to quickly respond to a change in grazing management alone. Therefore, an input of energy is required for the community to return to the Bunchgrass State (1).  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 Bunchgrass State (1). Wyoming big sagebrush steppe communities historically had low fuel loadings and were characterized by 10- to 70-year interval fires that produced a mosaic of burned and unburned lands (Bunting et al.,  1987). Following the fire on the fine-textured soils, the perennial bunchgrasses recovered in a few years and were present to fuel a subsequent fire. Conversely, extensive wildfires burning under hot, dry conditions would have resulted in the nearly complete destruction of scattered sagebrush (Arno and Gruell 1983). Winterfat is tolerant of low-intensity fire but will kill with a hot fire (Pellant 1984). This community crossed a threshold compared to the Mixed Bunchgrass Community (1.2) due to the erosion of soil, vegetation 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 cannot create sufficient improvement to restore the site within a reasonable time frame. Dormaar (1997) stated that with decreased grazing pressure, a needle and thread/blue grama plant community did not change species composition, but the content of the soil carbon increased. It will require a considerable input of energy to move the site back to Bunchgrass State (1). This state has lost soil or vegetation attributes to the point that recovery to the Bunchgrass State (1) 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 extensive drought. If heavy grazing continues, plant cover, litter, and mulch will continue to decrease, and bare ground will increase, exposing the soil to accelerated erosion. Litter and mulch will move off-site as plant cover declines. The Mixed Grass/Sagebrush Community will then shift to a Shortgrass/Shrub Community (2.2). Continued improper grazing will drive the community to a Degraded Shrub/Shortgrass State (3). Introduction or expansion of invasive species will further drive the plant community into the Invaded State (4).

Community 1.2.2
Needle and Thread/Shortgrass Community

With continued mismanagement of grazing, especially coupled with prolonged drought, needle and thread 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) will increase in vigor and production as they respond to resources previously used by the bunchgrasses. These less desirable, shallow-rooted species will become co-dominant with the bunchgrasses. Shrubs will become more competitive for limited moisture as bare ground and soil erosion increase. This state may exhibit conditions where livestock are consuming shrubs.

Pathway 2.1a
Community 1.2.1 to 1.2.2

The driver for community shift 2.1A is continued improper grazing management. This shift is triggered by continued loss of bunchgrass vigor, especially Needle-and-thread. The short-statured grasses will become more competitive and become co-dominant with the bunchgrasses. Shrubs will increase in canopy cover however may be browsed resulting in spreading formations.

Pathway 2.2a
Community 1.2.2 to 1.2.1

If proper grazing management is implemented needle-and-thread may regain its vigor and move towards the needle-and-thread community (2.1). This will give grasses an advantage over invading shrubs before too much competition takes place. The advantage to grasses comes from following a conservative grazing plan where utilization is reduced and rest or deferment is incorporated since the transition from Plant community 2.1 to Plant community 2.2 is likely caused by repeated heavy utilization. Van Poolen and Lacey (1979) found that forage production increased by an average of 35% on western ranges when converting heavy to moderate utilization (less than 50%). Shrub removal and favorable growing conditions can accelerate this process. If the site contains Wyoming big sagebrush (Artemisia tridentata spp. Wyomingensis), low intensity fire or mechanical treatment (Wambolt 1986) could reduce shrub competition and allow for increased vigor and the reestablishment of grass species.

State 1.3
Degraded State

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

Characteristics and indicators. 25-50% bare ground annual grasses common complete removal of bluebunch wheatgrass and replaced with sandberg bluegrass, western wheatgrass, and blue grama sagebrush nearly gone and replaced with rabbitbrush and broom snakeweed

Resilience management. Prescribed grazing, Range seeding, Brush Management, Integrated Pest Management

Community 1.3.1
Degraded Shortgrass/Shrub Community

Soil loss continues or increases to the point that native perennial grasses make up less than 350 pounds of annual dry weight production. Grass and forb cover may be very sparse or clumped (canopy cover <30%). Weeds, annual species or shrubs dominate the plant community. Mid-stature perennial bunchgrass species (e.g., needle-and-thread) may exist, but only in small patches. This could occur due to overgrazing (failure to adjust stocking rate to declining forage production due to increased invasive dominance), long-term lack of fire (if Wyoming Big Sagebrush occurs), or introduction of invasive species. Production values may be as low as 200 lbs per acre with up to 70-90% basal bare ground (foliar canopy is disregarded as a measurement) and plant basal area shrinks. In the most severe stages of degradation, there is a significant amount of bare ground, and large gaps occur between plants. Potential exists for soils to erode to the point that irreversible damage may occur. This is a critical shift in the ecology of the site. Soil erosion combined with lack of organic matter deposition due to sparse vegetation create 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 or community. Changing management (i.e., improving grazing management) cannot create sufficient change to restore the site within a reasonable time frame. This state is characterized by soil surface degradation and little plant soil surface cover. The forb component changes to be dominated by spiny phlox (Phlox hoodii) and shrub canopy cover is usually greater than 20%. Big sagebrush is replaced with a dominant community of broom snakeweed, rubber rabbitbrush, fringed sagewort, and plains pricklypear cactus. This state has lost soil or vegetation attributes to the point that recovery to the Bunchgrass Grassland State will require reclamation efforts, i.e. soil rebuilding, intensive mechanical treatments, and/or reseeding. This plant community may be in a terminal state that will not return to the reference state because of degraded soil conditions and loss of higher successional native plant species. Key factors of approach to transition: Decrease in grass canopy cover and production, increase of shrub canopy cover, increases in mean bare patch size, increases in soil crusting, decreases in cover of cryptobiotic crusts, decreases in soil aggregate stability, and/or evidence of erosion including water flow patterns and litter movement.

State 1.4
Invaded State

The Invaded State is identified as being in the exponential growth phase of invader abundance where control is a priority. Dominance (or relative dominance) of noxious or invasive species reduces species diversity, forage production, wildlife habitat, and site protection. A level of 20 percent invasive species composition by dry weight indicates that a substantial energy input will be required to create a shift to the grassland state (herbicide, mechanical treatment), even with a return to proper grazing management or favorable growing conditions. Prescriptive grazing 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.

Characteristics and indicators. High amounts of invading species (both native and introduced).

Resilience management. Integrated Pest Management Prescribed Grazing Brush Management Prescribed Fire Range Seeding

Community 1.4.1
Invaded Community

Communities in this state may be structurally indistinguishable from the bunchgrass state except that invasive/noxious species exceed 20% of species composition by dry weight. This state may also include a community similar to the Degraded Shortgrass State (3) except that invasive/noxious species exceed 20% of species composition by dry weight. Although there is no research to document the level of 20%, this is estimated to be the point in the invasion process following the lag phase based on interpretation of Masters and Sheley 2001. For aggressive invasive species (i.e., spotted knapweed) a 20% threshold could be less than 10 percent. 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. 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 an infestation of cheatgrass may produce only 10 to 20 percent of the reference community. Dense clubmoss has been included in this community until more information has been collected on its relationship with the Loamy Ecological Site. Since dense clubmoss is a portion of the reference plant community, it will only be considered as part of the invaded community when it significantly impacts plant production. The exact percent cover clubmoss at which it affects overall production has not been fully studied in this MLRA. 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 (4). As invasive species such as spotted knapweed, cheatgrass, and leafy spurge become established, they become very difficult to eradicate. Therefore considerable effort should be placed in preventing plant communities from crossing a threshold to the Invaded State (4) 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 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).

Community 1.4.2
Conifer Encroached Community

Rocky Mountain juniper (Juniperus scopulorum), Douglas fir (Pseudotsuga menziesii), and/or Ponderosa pine (Pinus ponderosa) encroachment is limited on this ecological site and is generally focused in in areas where the mountains of MLRA 44B transition quickly to MLRA 43B. Under the Reference State, no conifers should exist on this site. Conifer encroachment likely occurs in the late stages of the Altered State (see State-and-transition model) where there is an increase of bare ground due to a combination of factors. Fire suppression and improper grazing management are the two most common triggers. The exact conditions in which juniper begins to encroach vary however the trend points to a combination of 1 or more of the following: moderately heavy to heavy grazing, reduced (non-existent) fire frequency, increased atmospheric carbon, and generally warmer climate (compared to that of pre-settlement). When heavy grazing occurs areas in the plant canopy open allowing for seed dispersal by bird or overland flow via rills on neighboring sites. The effects of juniper encroachment are not immediately noticed however over time as juniper canopy increases; light and water interception increase which reduce opportunities for herbaceous plants. One paper (Barrett, 2007) suggests that for precipitation to penetrate the juniper canopy, events must be greater than 0.30 inches. Increase juniper canopy creates perching sites for predators which reduces site suitability for greater sage grouse. More information is needed on the full extent and impact of conifer encroachment on this plant communities for an approved Ecological Site Description. Studies (Miller et al 2000) based in a similar community to the Rocky Mountain Juniper community of Montana suggest following a phased approach to characterize the juniper stand. Not unlike the Western Juniper community discussed in Miller et al, the Rocky Mountain juniper communities of Montana exhibit 3 or 4 different phases based, at this time, on unquantified information. Phase I (Early) is defined by actively expanding juniper cover with generally <10% canopy cover and the trees’ limbs generally touch the ground. This early stage generally has not lost its hydrologic functions however herbaceous plant communities may show signs of reduced production and species richness. Control methods include mechanical removal and prescribed fire. Prescribed fire is still effective in this phase as it still contains the necessary native plants for recovery. The tree canopy is also low enough that risk of a dangerously hot fire is reduced. Phase II (Mid Stage) is still actively expanding however canopy cover may reach up to 25% and due to the more mature trees seed production is very high. This Mid Phase begins to highly restrict herbaceous and shrubby plant and junipers tend to be codominant. Hydrology is departing from reference with rills becoming longer and in isolated areas erosional gullies may exist. Control methods of the Mid Stage should focus on mechanical treatment as there is a high risk of catastrophic and potentially sterilizing fire. Phase III (Late stage) is where juniper cover exceed 25% and has slowed as a forest condition. Lower limbs of trees begin to die and the shrub cover is nearly lost. Traveling through this community is increasingly difficult. Junipers become the dominant plant with herbaceous plant production greatly decreased. Bare ground increases and hydrologic function is nearly lost compared to a grass/shrub community. Late Stage Phase should focus more on restoration than control as the necessary plants will likely not be present to cross the threshold back to a rangeland situation. The soil stability and hydrologic function are lacking in this phase so mechanical removal of juniper will be necessary. Phase IV (Closed) is the steady state forest where the system is nearly absent of rangeland plants. The trees stop producing seed and begin to close in on each other. This phase is impassible and nearly all light and precipitation are intercepted. Bare ground is high and soil chemistry slowly changes due to acidification from juniper. Within this LRU, the closed phase is extremely rare due to 2 reasons: 1) this phase takes upwards of 100 years to occur 2) management often occurs before trees are allowed to reach this phase. The presence of sagebrush stumps indicates the historical plant community as rangeland which will prevent misclassification of historic Juniper Forests (often >100 years of age).

Transition T1A
State 1.1 to 1.2

The Bunchgrass State (1) transitions to the Altered Bunchgrass State (2) if bluebunch wheatgrass, by dry weight, decreases to below 10% or if bare ground cover is increased beyond 20%. The driver for this transition is 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 Bunchgrass State. There are several other key factors signaling the approach of transition T1A: increases in soil physical crusting, decreases in cover of cryptogamic crusts, decreases in soil surface aggregate stability and/or evidence of erosion including water flow patterns, development of plant pedestals, and litter movement. The trigger for this transition is improper grazing management and/or long-term drought leading to a decrease in bluebunch wheatgrass composition to <15% and reduction in total plant canopy cover.

Transition T1C
State 1.1 to 1.3

The Bunchgrass State (1) transitions to the Degraded Shrub/Shortgrass State (3) when Bluebunch wheatgrass is removed from the plant community and Needle-and-thread is subdominant to short statured bunchgrasses such as Sandberg bluegrass. The trigger for this transition is loss of taller bunchgrasses, which creates open spaces with bare soil. Soil erosion results in decreased soil fertility, driving transitions to the Degraded Shrub/Shortgrass State. There are several other key factors signaling the approach of transition T1C: increases in soil physical crusting, decreases in cover of cryptogamic crusts, decreases in soil surface aggregate stability and/or evidence of erosion including water flow patterns, development of plant pedestals, and litter movement. The driver for this transition is improper grazing management, intense or repeated fires, and/or heavy human disturbance. Rapid transition is generally realized where livestock are confined to small pastures for long periods of time.

Transition T1B
State 1.1 to 1.4

Healthy plant communities are most resistant to invasion however, regardless of grazing management, without some form of active weed management (chemical, mechanical, or biological control) and without prevention the Bunchgrass State (1) can transition to the Invaded State (4) in the presence of aggressive invasive species such as spotted knapweed, leafy spurge, and cheatgrass. The Central Rocky Mountain Valleys tend to resists invasion of cheatgrass however repeated heavy grazing or intense human activities can open the interspaces of the bunchgrass community 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 Invaded State. The trigger for this transition is the presence of aggressive invasive species. Species composition by dry weight of invasive species approaches 10%.

Restoration pathway R2A
State 1.2 to 1.1

The Altered Bunchgrass State (2) has lost soil or vegetation attributes to the point that recovery to the Bunchgrass State (1) will require reclamation efforts such as soil rebuilding, intensive mechanical and cultural treatments, and/or revegetation. Examples of mechanical treatment may be brush control while cultural treatments may include prescribed grazing, targeted brush browsing, or prescribed burning. Low intensity prescribed fires to reduce competitive increaser plants such as needle-and-thread and Sandberg bluegrass. A low intensity fire will also reduce Wyoming big sagebrush densities. In areas with potential of annual grass infestation, fire should be carefully planned or avoided. The drivers for this restoration pathway are reclamation efforts along with proper grazing management.

Transition T2A
State 1.2 to 1.3

As improper grazing management continues vigor of bunch grasses will decrease, and the shorter grasses and shrubs will increase towards the Degraded Shortgrass State (3). Prolonged drought will provide a competitive advantage to shrubs allowing them to become co-dominant with grasses. Shrub canopy will increase. Key transition factors: increase of native shrub canopy cover; reduction in bunchgrass production; decrease in total plant canopy cover and production; increases in mean bare patch size; increases in soil crusting; decreases in cover of cryptobiotic crusts; decreases in soil aggregate stability; and/or evidence of erosion including water flow patterns and litter movement.

Transition T2B
State 1.2 to 1.4

Invasive species can occupy the Altered State (2) and drive it to the Invaded State (4). The Altered State is at risk if invasive seeds and/or other viable material are present. The driver for this transition is more than 20% dry weight of invasive species. The trigger is the presence of seeds and/or other viable material of invasive species.

Restoration pathway R3B
State 1.3 to 1.1

The Degraded Shortgrass State (3) has lost soil or vegetation attributes to the point that recovery to the Bunchgrass State (1) will require reclamation efforts, such as soil rebuilding, intensive mechanical treatments, and/or revegetation. Studies suggest (Whitford et al 1989) a mulch with high carbon to nitrogen ratio such as wood chips or bark in low moisture scenarios can be beneficial for slow mobilization of plant available nitrogen. 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 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 presence of seeds and/or other viable material in the soil and management related increases soil disturbance.

Restoration pathway R3A
State 1.3 to 1.2

Since the bunchgrass plant community has been significantly reduced, restoration to the Altered State (2) is unlikely unless a seed source is available. If a sufficient amount of grass remains on the site, chemical application and/or biological control in conjunction with proper grazing management, can reduce the amount of shrubs and invasive species and restore the site to the Shortgrass Community (2.2). Low intensity fire can be utilized to reduce Wyoming big sagebrush 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 re-sprout after a burn. Broom snakeweed and fringed sagewort may or may not re-sprout depending on conditions (USDA Forest Service 2011).

Transition T3A
State 1.3 to 1.4

Invasive species can occupy the Degraded Shortgrass State (3) and drive it to the Invaded State (4). The Degraded Shortgrass State is at risk of this transition occurring if invasive seeds or viable material are present. The driver for this transition is presence of critical population levels of invasive species. The trigger is the presence of seeds or viable material of invasive species. This state has sufficient bare ground that the transition could occur simply due to 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), long-term lack of fire, or extensive drought.

Restoration pathway R4C
State 1.4 to 1.1

Restoration of the Invaded State (4) to the Bunchgrass State (1) 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-related practices that increase soil disturbance. If invaded by conifer encroachment, treatment depends on the condition of the rangeland. See Plant community 4.1 for alternative measures of restoration. Sites that have transitioned from the Degraded State (3) to the Invaded State (4) 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.

Restoration pathway R4B
State 1.4 to 1.2

If invasive species are removed before remnant populations of bunchgrasses have been drastically reduced the Invaded State (4) can return to the Altered State. The driver for the reclamation pathway is weed management without 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.

Restoration pathway R4A
State 1.4 to 1.3

If invasive species are removed the site could return to the Degraded Shortgrass State (3). Without sufficient remnant populations of preferred plants the Invaded State (4) 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. The invading species cause a significant increased soil loss due to lack of ground cover (Lacey et al. 1989).

State 2
Cropland

Native rangeland is converted to a Cultivated system dominated by introduced species for forage or grain production. This system often receives multiple inputs including fertilizer, herbicides, and irrigation.

Characteristics and indicators. Site is sodbusted and converted to forage or grain production

State 2.1
Cultivated Forage Community

The Cultivated Forage Community is the most common within the Cultivated State. It consists primarily of long-term grass or forb crop planted for grazing or hay. If irrigation water is available, species will be highly variable based on the goals and objectives of the land manager; however. alfalfa is likely included. Production of an irrigated site in this community is typically high If irrigation is not available, the dry climate limits species options and will likely include Crested wheatgrass or Russian wildrye. Alfalfa is rarely a lone species under dryland conditions.

State 2.2
Abandoned Cultivated Field

The Abandoned Cultivated Field Community is a relatively rare occurrence due to the productive nature of this ecological site. However, as traditional land use transitions from agriculture to recreation, abandonment of cultivation may occur. If the site was in the Actively Cultivated State at the time of abandonment, the resulting plant community will likely transition into an herbaceous annual weed community. Over time, the weeds will typically yield to a naturalized community of perennial grasses and forbs sourced from the surrounding plant community. Needle and thread, blue grama, Sandberg bluegrass, rabbitbrush, and fringed sagewort are the common native species that can be considered colonizing species. Active Cultivated States are rarely abandoned without some attempt of being planted to a Cultivated Forage Community first. If the site was managed as a Cultivated Forage Community at the time of abandonment, the plant community tends to transition into a community that resembles a Degraded State over time. With enough time, native colonizing species will slowly fill the interspaces between the forage crops. Once the Abandoned Cultivated Field Community has reached maturity, it will have similar ecological processes as the Degraded State (3.1)

State 2.3
Active Cultivated Community

Active Cultivated 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. If irrigation is available this community is capable of producing a wide variety of crops including corn silage, seed potatoes, pumpkins, sunflower, and other specialty crops. The relatively short growing season tends to be the restriction if irrigated. Long-term annual cropping can destroy soil aggregation, create soil erosion (both wind and water), deplete organic matter, and alter pH so a conservative crop management system will need to be applied to prevent degradation of the site.

Transition T1A
State 2.1 to 2.2

Cultivated Forage Community is abandoned. This pathway rarely occurs in present time however has occurred frequently in the past which is how Community 5.2 may be observed. In this process, a reason for abandonment occurs and the field sits idle from management. Over time the surrounding native vegetation fills the interspaces between plants.

Transition T1B
State 2.1 to 2.3

Cultivated Forage Community is converted from permanent cover to an annually cropped system. Change takes place when cultivation or plowing occurs. This community pathway is a frequent occurrence on this ecological site particularly when the Cultivated Forage Community’s production begins to drop. This is often on a 10-20year cycle in this MLRA.

Transition T2A
State 2.2 to 2.1

Abandoned Cultivated Field is planted to a forage or hay crop of the manager’s preference. Often this pathway will require tillage or herbicide to terminate the existing plant community and seeding to initiate change.

Transition T2B
State 2.2 to 2.3

An abandoned cultivated field is converted to an annually cropped system. Change takes place when cultivation or plowing occurs. This community pathway is often necessary to convert a lower producing or undesirable community into an annually cropped system.

Transition T3A
State 2.3 to 2.1

Active Cultivation Community is planted to a forage or hay crop of the manager’s preference. This is a common pathway in this MLRA.

Transition T3B
State 2.3 to 2.2

Active Community is abandoned. This pathway rarely occurs in present time however has occurred frequently in the past which is how Community 5.2 may be observed. In this process, a reason for abandonment occurs and the field sits idle from management. Over time the surrounding native vegetation fills the interspaces between weedy, herbaceous plants

Conversion C1
Land use 1 to 2

Native rangeland is converted via tillage for production of forage crop or grains.