State 1
Tree/Cool-Season Grasses

The complexity of the Lowland ecological state, and the narrow or linear patterns of this ecological site, make it difficult to capture the full range of variability. The alterations and encroachment of non-native species has had a significant impact on these communities as well as the alteration of the hdyrologic patterns of flooding due to water control structures has further impacted this ecological site. This State is to capture the native component of the community with the major tree cover, and then the step of tree loss and transition to a dryer, more upland related community.

Characteristics and indicators. The native composition of trees, shrubs, and grasses is the indicator for this community. The presence or remnants of narrowleaf cottonwood and balsam poplar are key in this community. The understory of riparian and upland shrubs including wood's rose, gooseberry, mountain big sagebrush, and snowberry are prominent. A variety of forbs are present, and are highly variable. The grasses are cool-season grasses with tall-stature grasses dominant in Reference, moving to mid and short-stature grasses in the more at-risk communities in this state.

Resilience management. The Reference communities are fragile due to the dependence on spring flooding and infrequent fires to maintain a healthy community. The proximity to water creates a high impact to this ecological site, especially with livestock, putting these communities at risk. The Reference State is resilient to disturbances when the system is unimpaired by human interference (natural stream system). However, with water control structures, fire suppression and shifts in grazing patterns has weakened the resilience and resistance of this State.

Community 1.1
Basin Wildrye/Poplar

Figure 9. Reference Community Phase 1.1 following an intensive fall grazing period.

The interpretive plant community for this site is the Reference Community Phase. This state and community evolved with grazing by large herbivores, occasional overflows during flooding events, and periodic fires. Potential vegetation is about 60 percent grasses or grass-like plants, 15 percent forbs and 25 percent woody plants. Cool-season tall and mid-stature grasses dominate this state. The major grasses include basin wildrye, slender wheatgrass, Columbia needlegrass, and rhizomatous wheatgrasses. Other grasses occurring in this community include Canada wildrye, big bluegrass, and nodding brome. Narrowleaf cottonwood and balsam poplars of various age classes comprises the primary overstory species, while mountain big sagebrush and a variety of riparian shrub species are a component of the understory. A variety of forbs also occurs in this community and plant diversity is high (see Plant Composition Table).

The total annual production (air-dry weight) averages 2500 pounds per acre in a normal year, ranging from 2000 pounds per acre in unfavorable years to 3000 pounds per acre in above average years.

Resilience management. This plant community is extremely stable and well adapted to the climatic conditions of the Upper Foothills. The diversity in plant species allows for high drought tolerance. This is a sustainable plant community (site/soil stability, watershed function, and biologic integrity).

Community 1.2
Sapling/Riparian Shrub

Figure 12. Slender wheatgrass and cottonwood saplings are significant with a mixture of shrubs and a few mature trees.

Historically, this plant community was considered rare as the natural fire regime within a riparian community provided for more frequent and less severe fires. These low intensive or ground fires resulted in thinning of the poplar stand and provided micro-sites, which quickly were colonized by new saplings. These transitions were relatively short lived, because of the moist soil conditions, adaptability of the species, and mosaic nature of the fire. As such, these areas maintained the mixed age stands, which is synonymous with the Reference Community Phase. Today these low intensity fires can still occur and under this situation, the natural regeneration of vegetation is considered a transitional phase of this ecological site and not a separate plant community.

This plant community is now more common, as fire suppression has resulted in more fuels and when fires do occur these fires are normally more intense and can affect larger areas. Severe fires typically result in the total mortality of the stand, as poplar and cottonwoods are not very resistant to high temperatures. Subsequently, the regeneration of poplar trees to a multi-age mature stand can take decades. This is especially true if the soils are sterilized. This transition to a mature cottonwood plant community usually occurs only after the saplings become mature trees and shading by the expanding canopy helps to suppress the dominant shrub understory component. Given the extent of the burned areas and prolonged time to transition to a multi-age poplar stand, this site can become relatively stable. Under this situation, these sites should be considered separate plant communities.

Riparian shrubs such as willow, wild rose, snowberry, and gooseberry dominate this plant community. Poplar saplings regeneration will depend on availability of seeds and seed bed conditions. Shrubs, poplar and cottonwood saplings usually make at least 40 percent and can even reach to 80 percent of the total production. On sites where there was a healthy stand of perennial grasses prior to the fire, these grasses can quickly become reestablished and will diminish the total frequency and production of shrubs and saplings.

Dominant grasses may include rhizomatous wheatgrasses, green needlegrass, and slender wheatgrass. Grasses of secondary importance include Sandberg bluegrass and big bluegrass. Bare ground can also be pronounced and and litter diminished. When compared to the Reference Community Phase, the production is less but the re-growth after a fire and amount of shrubs offset some of the reduction in the total production.

The total annual production (air-dry weight) varies depending on the stage of the succession but averages about 1800 pounds per acre is normal years. It can range from about 1300 pounds per acre in unfavorable years to about 2300 pounds per acre in above average years.

Resilience management. This Community Phase (1.2) is relatively stable but grazing the site before the vegetation becomes stabilized is not recommended. Erosion may be excessive until the site is revegetated. Erosion control may be necessary if soil loss is excessive, however, cottonwood regeneration depends on exposed bare soil. The biotic integrity of this plant community is in intact. The watershed is functioning.

Community 1.3
Mature Poplar/Cool-season Mid-stature Grasses

Figure 15. The mature poplar stand in the background with a shrub and native grass understory.

This plant community evolved under moderate grazing by domestic livestock, periodic flooding, and fire suppression. Mid-stature cool-season grasses make up the majority of the understory with the balance made up of short cool-season grass, and miscellaneous forbs. Balsam poplars, cottonwood, sagebrush, and riparian shrubs comprise greater than 35 percent of the total annual production of this plant community.

Dominant grasses include slender wheatgrass, rhizomatous wheatgrasses, Idaho fescue, and mountain brome. Grasses of secondary importance include Sandberg bluegrass, big bluegrass, and Canada wildrye. Mountain big and silver sagebrush and a variety of riparian species comprise most of the total shrub production. Cottonwood stands are still a prominent part of the plant community.

When compared to the Reference Community, Phase, basin wildrye and Columbia needlegrass has decreased. Rhizomatous wheatgrasses, big bluegrass, and Sandberg bluegrass and other more upland grass species have increased. Willow, mountain big and silver sagebrush, snowberry, gooseberry, and wild rose have increased. The percentage of mature poplars to younger aged trees has increased although young saplings and mid-aged trees are still healthy and flourish in this site. Poplar saplings are not as extensive.

The total annual production (air-dry weight) of this state is about 2300 pounds per acre, but it can range from about 1600 lbs./acre in unfavorable years to about 3100 lbs./acre in above average years.

Resilience management. This state is stable and protected from excessive erosion once established. The biotic integrity of this plant community is intact. However, a slight decline in the cottonwood reproduction is evident and may affect the vigor of the stand over a long period. This is true especially if no low intensive or ground fires occur or if conditions are not right for seedling establishment. The watershed is functioning. Water flow patterns and litter movement may be occurring but in isolated areas. Incidence of pedestalling is minimal. Soils are mostly stable and the surface shows minimum soil loss.

Community 1.4
Cool-Season Upland Grasses

Figure 17. Rhizomatous wheatgrass and a few scattered shrubs maintain this community, where the cottonwood galleries are restricted to the wet channels.

This plant community can occur where the dominant tree species have been removed and suppressed. Preferred cool season grasses have been established and shrubs have been controlled, but the upland plants are now the dominant species. Poplar and Cottonwood trees are not a part of this community and will not be able to reestablish.

This site is dominated by an overstory of a variety of shrubs, such as mountain big sagebrush, silver sagebrush, gooseberry and wild rose. Small patches of riparian shrubs may remain where moisture can accumulate. Perennial cool-season mid-stature grasses have been established such as rhizomatous wheatgrasses, mountain brome, tufted hairgrass and slender wheatgrass. Basin wildrye and a variety of sedges may also be establishing in small pockets where additional moisture accumulates but will be infrequent. The interspaces between plants will have diminished in size. When compared with the Reference Community Phase, the annual production has been significantly reduced and the plant composition is clearly unique as upland plants now make up the balance of the species.

The total annual production (air-dry weight) of this state is not provided. Insufficient data exists to establish an accurate production value at this time.

Resilience management. This plant community is mostly resistant to change, but species composition can be altered through long-term overgrazing. The herbaceous component is stable, but does not include most climax species. Plant vigor and replacement capabilities are sufficient. The biotic community is not intact because of the predominant upland plants and lack of climax grass species. Plant diversity is moderate. Soils are mostly stable and recent soil loss is minimal. This should not be confused with evidence of remnant erosion. Water flow patterns and litter movement is stable but is still occurring on steeper slopes. Incidence of pedestalling is improving. The watershed is not functioning.

Pathway 1.1A
Community 1.1 to 1.2

Basin Wildrye/Poplar

Sapling/Riparian Shrub

Fire, especially when severe, will remove the mature tree stands and leave saplings and shrub mix to regenerate in the community. This transitional community phase is part of the natural rejuvenation process of the Poplar community.

Pathway 1.1B
Community 1.1 to 1.3

Basin Wildrye/Poplar

Mature Poplar/Cool-season Mid-stature Grasses

Moderate, continuous season-long grazing and Drought will convert this plant community to the Mature Stand/Cool-season Mid-stature Grasses Community Phase. Prolonged drought will exacerbate this transition, as periodic flooding of the site will not occur. The grazing pressure with drought stress removes the taller grass species and key forbs from the community aiding in the transition.

Pathway 1.2A
Community 1.2 to 1.1

Sapling/Riparian Shrub

Basin Wildrye/Poplar

No fire plus prescribed grazing will result in a plant community very similar to the Reference Community Phase (1.1). Allowing mature trees to stand with an undergrowth of younger saplings and a mixture of tall and mid-stature cool-season grasses. Periodic flooding will hasten this transition with rejuvenation of the tree stand.

Pathway 1.2B
Community 1.2 to 1.3

Sapling/Riparian Shrub

Mature Poplar/Cool-season Mid-stature Grasses

Lack of fire over time with grazing and browse will reduce saplings and leave a mature tree stand with a limited understory of mid-stature cool-season grasses. Drought will affect the understory vegetation, limiting the community to mid and short-stature cool-season grasses and a mixture of forbs.

Pathway 1.3A
Community 1.3 to 1.1

Mature Poplar/Cool-season Mid-stature Grasses

Basin Wildrye/Poplar

Prescribed grazing and re-occurrence of periodic flooding will result in a plant community very similar to the Reference Community Phase. Low intensive fires will hasten this transition.

Pathway 1.3B
Community 1.3 to 1.2

Mature Poplar/Cool-season Mid-stature Grasses

Sapling/Riparian Shrub

Prescribed grazing with rest will allow perennial grasses to recover, allowing the key tall-stature species to re-establish. With rest and possibly with plantings to assist, the shrub and tree component can improve in this system. Fire and drought may trigger a thinning of tree canopies to allow the light and precipitation to reach the lower canopy to encourage new growth.

Context dependence.The hydrologic processes of flooding with scouring and deposition of materials must still occur to have this process occur naturally.

Pathway 1.3C
Community 1.3 to 1.4

Mature Poplar/Cool-season Mid-stature Grasses

Cool-Season Upland Grasses

The change in flooding cycles with control of water ways with dams and irrigation systems have limited the rejuvenation of poplar and cottonwood galleries. The loss of this system function has created a droughty community within the Lowland ecological site that has lost the tree cover and the taller grass community.

State 2
Invaded

Increased activity on the landscapes provides more opportunity for disturbances as well as an increase of non-native species seed source. Disturbances to the soil surface and exiting canopy cover provides opportunity for non-native species to establish.

The most prevalent invader on Lowland ecological site is smooth brome and Kentucky bluegrass. The occurrence of these communities can be a process of time or of disturbance. Historic studies have documented the presence of non-native species such as Kentucky bluegrass and dandelions prior to the early 1950's. Different references list these two species as naturalized species.

Another concern is the threat of large scale weed invasions. Currently, most of the mountain has retained only small or isolated patches of invasive weeds. Areas of leafy spurge, toadflax (yellow or dalmation) and thistles have been identified. Although early detection/rapid response techniques are applied for land management, limited resources make it difficult to track all current and new infestation sites. Overall, the weed infestation level is not seen as a critical concern, but the threat is growing and being monitored closely.

Characteristics and indicators. Non-native or tame species and invasive species are a concern on the the Lowland soils. The frequent disturbance from spring flood water and fluctuating water table provide opportunity for establishment. The threshold that is crossed to indicate an invaded site is 5 percent composition by cover or by weight. The dominant non-native/invader species are Kentucky bluegrass, smooth brome, thistles, toadflax (Dalmatian, yellow), and swanson's pea. As new species are found, this list will be adapted to include these species.

Resilience management. Non-native and invasive species are resistant to change and resilient following disturbances. This makes a stable community that is difficult to change without significant inputs. The salt-laden soils limit the type of treatment, access, and species adapted to help recovery of the Invaded Community. Kentucky bluegrass, smooth brome, and other non-native species have a high resiliency once they have established in a community. The management of the native species is difficult, and is dependent on what specific species composition exists in the individual community. The removal or treatment of encroaching woody species is best tackled when they occur at a low intensity, before they may be seen as a concern.

Community 2.1
Non-Native (Tame) Invaded

Figure 18. Smooth brome community under a mature cottonwood gallery.

Figure 19. Kentucky bluegrass in a mature cottonwood gallery.

This plant community is the result of long-term improper grazing use and an interruption in the frequency of flooding or channelization. The disruption, either directly by humans, such as dams or dikes, or indirectly through accelerated erosion and channelization, has caused an interruption in the natural flooding regime. Extended periods of drought will exacerbate this situation. Usually fire has been removed from this plant community as bluegrass is a poor conductor of fire.

Non-Native (Tame) Community Phase has maintained a representative sample of the perennial grasses and forbs that are typical of the site with a mixed shrub community.
Non-native or tame species have established in the community and are a significant component (five percent or greater by foliar cover or weight), and are prominent (referring to a more wide scale composition, not one isolated patch in an isolated portion of the landscape). This plant community is dominated by a dense grass sod of bluegrass or smooth brome and includes a mosaic of mature balsam poplars, cottonwoods, sagebrush or riparian shrub overstory. In some instances shrubs may be limited in this community.

Production of the desired perennial species is generally reduced but the total production is maintained or elevated due to the production potential of the non-native species. The species most common are Kentucky bluegrass and smooth brome. Native species that are less desirable that are common to this community are American licorice and cudweed sagewort. Dandelion is a common non-native forb.

The total annual production (air-dry weight) of this state is not provided due to lack of sufficient data as well as the extreme variability between invader species.

Resilience management. This plant community is resistant to change. Plant diversity is moderate to poor. The plant vigor is variable, as both Kentucky bluegrass and smooth brome are sod-forming or tillering species that over time will lose vigor due to being root-bound. Plant litter is noticeably more when compared to reference communities due to the potential biomass produced by the non-native species (species dependent). Soil erosion is variable depending on the species of invasion and the litter accumulation thus associated, this variability also applies to water flow patterns and pedestalling. Infiltration is reduced and runoff is increased due to loss of perennial vegetation and root density.

Community 2.2
Invasive Invaded

Figure 20. Canada Thistle is an aggressive invader in the Lowland ecological site.

The Invasive Invaded Community Phase has maintained a fractured sample of the perennial grasses and forbs that are typical of the Lowland ecological site, however there is a significant establishment of invasive species. This plant community evolved under frequent and severe grazing as well as the disruption of the hydrologic cycle. The shrub component has been impacted and possibly removed by heavy browsing or human means. Weedy annuals and non-native species are the most dominant plants.

Invasive species, most commonly canada thistle, cockle bur, swainson's pea, and perennial pepperweed, hold a significant (5 percent or greater) composition on the landscape, and are prominent (referring to a more wide scale composition, not isolated patches on the landscape). Russian olive may be present, but is not as common as on lower elevations.

With the decrease or loss of most desirable grasses, Kentucky bluegrass, smooth brome, slender wheatgrass and rhizomatous wheatgrasses will persist on the site. Cudweed sagewort, western yarrow and other forbs will persist. Noxious weeds such as sow thistle may invade the site if a seed source is available. Production of the desired perennial species is generally reduced but the total production is maintained or elevated due to the production potential of the invasive species.

Resilience management. This plant community is resistant to continued herbivory. Annuals and invader species are effectively competing against the establishment of perennial cool-season grasses. Plant diversity is greatly altered and the herbaceous component is not intact. Recruitment of the major perennial grasses is not occurring and the replacement potential is low. The biotic integrity is missing. The state is unstable and is not protected from excessive erosion. Rill channels and gullies may be present on site and adjacent areas are impacted by excessive runoff. Water flow patterns and pedestalling are obvious. The watershed is not functioning.

Pathway 2.1A
Community 2.1 to 2.2

Non-Native (Tame) Invaded

Invasive Invaded

Seed sources are abundant for both non-native and for invasive invader species. Drought stress, ground/soil disturbance including impacts by grazing large herbivores or recreation create a niche for undesirable weeds to establish, even in the aggressive cover of tame invaders. Overland flow or irrigation practices can also serve as a seed source and means of establishing many invasive species in the community.

State 3
Disturbed

Although to a much smaller extent than in lower elevations, there are areas that have been accessed for irrigation convenience ditches or were part of a homestead. These areas have remnants of introduced species from haylands or have been left to recover and may be in varying stages of succession. There are areas that are heavily impacted by recreational vehicles, parking, trails, roadways, or other land disturbances that have reduced or removed most native perennial vegetation and left a highly disturbed land.

The Disturbed State could be drafted as a stand-alone box within the state and transition model diagram. No matter what state a site originally is ranked in, once the site is mechanically disturbed, or suffers a catastrophic or significant natural disaster that alters the soil properties (erosional, depositional, or chemical), the site potential is altered. The most prominent shift for this site tends to be a shift in the natural hydrology that is key to this site. This can include both the loss of or enhancement to the additional moisture to the site (seepage from irrigation ditches).

Mechanical disturbances and reclamation practices using non-native species could qualify some stages of this state to be considered as a land use shift. The result is the shift in potential and response in management so that it is no longer similar to the reference community. The potential shifts are highly variable, so a dynamic state was captured to highlight the altered communities that exist on the landscape.

Characteristics and indicators. The soil disturbance and mechanical or physical removal of the vegetative canopy is the key characteristic of the Disturbed State. The initial indicators are the primary successional species that establish following a disturbance including Russian thistle, kochia, and sunflowers. These initial colonizers will then be followed by any seeded species, or other species from within the locations seed bank.

Resilience management. The Disturbed State is highly variable and in a state of flux as the successional processes occur. Continued disturbance of these communities is a potential threat; and the communities are at high risk of transitioning to the Invaded State.

Community 3.1
Disturbed Lands

The title Disturbed Lands is encompassing two broad classifications of these land types. Go-back fields or tilled areas form Type one. The soils were once cultivated or were impacted by cultivation practices and have since been left to natural processes. Abandoned farming sites can be identified on the landscape (through photo-tone shifts in aerial photographs) and are generally a mix of natives and introduced herbaceous species as well as trees. These sites are generally isolated or small in nature and are difficult to reclaim due to the introduced species that persist on the landscape and the shift in hydrology. If reclaimed, they do not respond to the natural disturbance regimes in the same manner that a native, mechanically undisturbed site would respond. The Lowland ecological site is a prime location for homestead crop or hayfields, or irrigation processes. Homesteads or corral systems are common on these areas, due to being connected to water. The extent of this type is limited on the landscape due to the size of the drainages they are associated with.

A subset of Type one are those areas that were or currently are being impacted by recreation - camp sites, trails, parking areas, roadways. The varying stages of healing once abandoned, or the level and age of disturbance at each location leave a variable community.

In a similar process, lands affected by energy development including transmission and transportation corridors provide a host of successional processes. Many times, these locations are re-exposed to disturbance frequently by mechanical means leaving annual weeds and primary successional species as the dominate canopy. Older, established sites or abandoned locations, have established communities similar to those expected on go-back fields and may be stable in nature.

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

Resilience management. The plant community is variable and depending on the age of the stand and the stage of successional tendencies that the location is in will determine how stable (resilient/resistant) the community is. Plant diversity is generally strong, but is usually lacking in the structural and functional groups that are desired on the site. Soil erosion is variable depending on the disturbance regime that is occurring on the site and will vary with the specific community that has established on a specific location. Site-specific evaluation is needed to determine the water flow and pedestalling as well as infiltration and runoff potential and associated risks for each community.

Community 3.2
Restored

The Lowland ecological site has potential for successful establishment of a diverse vegetative cover. Many times these areas are seeded with improved varieties or used as pastures, especially in areas where the fluctuating water table and spring flooding provides significant water. However, many times, these areas have an existing cover of introduced species that limits the ability to move this back to the reference state. The soil disturbance that occurs in the seed bed preparation and seeding also alters the function of the soil so that it does not respond in the same manner as an undisturbed native community.

Resilience management. Encroachment of non-native species such as Kentucky bluegrass as well as smooth brome is a threat until this community is fully established. The resiliency and resistance of the community will be dependent on the seed mixture used, the success rate of the seeding, and the management pre- and post-treatment.

Pathway 3.1A
Community 3.1 to 3.2

Integrated pest management with seed bed preparation and seeding helps to established an improved vegetative cover. Stabilizing the location is key in maintaining the community. Bank stabilization, improved or limited access (recreational impacts), or shifts in grazing management may be needed to fully recover (establish) a community.

Pathway 3.2A
Community 3.2 to 3.1

The lack of management of the disturbances that led to the need to restore a community will quickly transition the community back to a disturbed condition. Climatic conditions can cause seeding failure which could also quickly transition the community. Drought, severe

Transition T1A
State 1 to 2

Frequent and Severe grazing plus encroachment will convert this plant community to an Invaded State. Grazing reduces the vigor and cover of native cover, allowing aggressive non-native species to creep into a community. Soil disturbance and increased activity (by livestock, wildlife, or human) provide a seed source for invaders to establish.

Constraints to recovery.The aggressive nature of invader species limits the ability for a community to overcome their establishment. In many cases, control or removal has not been completed successfully without complete manipulation.

Context dependence.The depth to the water table, frequency of flooding, and any alterations to the flooding cycle are factors affecting both the species of invasion and the ability to control these species.

Transition T1B
State 1 to 3

An abrupt or catastrophic disturbance will remove or significantly impact the native community and the soil structure, leaving a disturbed and barren site. With time, natural succession will begin the recovery process. However, the soil as well as hydrologic function has been altered in many cases, leaving a Disturbed State. Fire, intensive or continuous, season-long, grazing, recreational impacts as well as intensive flooding can be the driver of this transition.

Constraints to recovery.The inability to restore hydrology or to replace soil stability in function (in the scope of significant bank erosion, head cuts or gullying) limits the recovery potential after significant disturbance.

Context dependence.Reclamation or restoration of the reference community is a challenge due to limitations of seed sources. Seedbed or site preparation is limited by the wetness of the soil, depth to water table and the soil textures. Access to these sites with equipment is limited in areas due to channel form, and wetness of the site.

Restoration pathway R2A
State 2 to 3

Once a site has transitioned to the Invaded State, the composition of tame and invasive species limits the ability to restore the community without major inputs into the system. Site preparation and seeding with intensive weed and integrated pest management is required. Seeding of both herbaceous as well as woody species may be required depending on the extent of alteration the site has seen. The soil preparation for seeding will affect the response to management and natural disturbances due to the mixing and alteration of the soil profile. Once the community is established, grazing management to maintain this community as well as control of other disturbances is required.

Context dependence.The inability to effectively eradicate the undesirable species is the known limitation or constraint to this site recovering. Seed availability and establishment rates are also considerations needed when looking at the scope of this process.

Transition T3A
State 3 to 2

Once a site has transitioned to the Degraded State, the increased bare ground and weakened plant structure leaves the community at risk of encroachment by non-native species such as Kentucky bluegrass, smooth brome. Thistles, toadflax, and houndstounge are quickly becoming significant problems on areas within these weakened plant communities. A Disturbed Community has lost native cover and is exposed to those invader species that have a seed source present. Restoration attempts for these degraded communities are at risk of failing or being degraded with the lack of management changes. Increasing bare ground and weakening plant community structure leaves the community vulnerable to invader species such as toadflax and houndstongue.

Constraints to recovery.The inability to effectively eradicate the undesirable species is the known financially limiting constraint to this site recovering.