State 1
Basin Wildrye/Cottonwood Plant Community

Community 1.1
Basin Wildrye/Cottonwood Plant Community

The interpretive plant community for this site is the Historic Climax Plant Community. This state evolved with grazing by large herbivores, periodic flooding, and fires. Potential vegetation is about 60% grasses or grass-like plants, 10% forbs and 30% woody plants. Cool season tall and midgrasses dominate this state. The major grasses include basin wildrye and slender wheatgrass. Other grasses occurring in this state include rhizomatous wheatgrasses, Canada wildrye, bottlebrush squirreltail and needleandthread. Cottonwood species of various age classes are the primary tree species, while basin big sagebrush and a variety of riparian shrubs comprise the main shrub species. A variety of forbs also occurs in this state and plant diversity is high (see Plant Composition Table). The total annual production (air-dry weight) of this state is about 1800 pounds per acre, but it can range from about 1400 lbs. /acre in unfavorable years to about 2400 lbs. /acre in above average years. This plant community is extremely stable and well adapted to the Northern Intermountain Desertic Basins climatic conditions. The diversity in plant species allows for high drought tolerance. This is a sustainable plant community (site/soil stability, watershed function, and biologic integrity). Transitions or pathways leading to other plant communities are as follows: • Moderate, continuous season-long grazing and drought will convert this plant community to the Mature cottonwoods/Cool-Season Mid-Grass Plant Community. Prolonged drought will exacerbate this transition, as fewer flooding events will occur. • Wildfires will convert this plant community to the Cottonwood Sapling/Riparian Shrub Regeneration Plant Community. Usually cottonwood sapling regeneration is relatively rapid unless the soils are sterilized. In this case, revegetation of the site is slow and may take many years. Low intensity or ground fires will result in thinning of the cottonwood stand and provide microsites, which can be quickly colonized by new saplings. These fires usually result in a mixed-aged stand of mature or younger trees with a sapling understory. Moderate or severe fires, however, usually will result in total stand mortality as cottonwoods are not very resistant to high temperatures. Under these scenarios, cottonwood seedlings can still quickly become established if the soils are not sterilized and an even aged stand will result. As with any wildfire, shrubs also play an important role as to what plants will emerge first and what will the species composition develop into after fire succession. The effects of fire in these plant communities have not been adequately studied and the understanding of fire succession is minimal.

State 2
Mature Cottonwoods/Cool-Season Mid-Grass Plant Community

Community 2.1
Mature Cottonwoods/Cool-Season Mid-Grass Plant Community

This plant community evolved under moderate grazing by domestic livestock, periodic flooding, and fire suppression. Cool-season grasses make up the majority of the understory with the balance made up of short warm-season grasses, annual cool-season grass, and miscellaneous forbs. Cottonwood, basin big sagebrush and riparian shrubs comprise up to one-third to one-half of the total annual production of this plant community. Dominant grasses include slender wheatgrass, rhizomatous wheatgrasses, needleandthread, and bottlebrush squirreltail. Grasses of secondary importance include Sandberg bluegrass, big bluegrass, and Canada wildrye. Big sagebrush and a variety of riparian species comprise most of the total annual shrub production. Cottonwood stands are still a prominent part of the plant community. When compared to the Historical Climax Plant Community, basin wildrye has decreased. Needleandthread and Sandberg bluegrass and other more upland grass species have increased. Big sagebrush, silver buffaloberry and wild rose have increased. The percentage of mature cottonwoods to younger aged trees has increased although young saplings and mid aged trees are still healthy and flourish in this site. Cottonwood saplings are not as extensive. The total annual production (air-dry weight) of this state is about 1500 pounds per acre, but it can range from about 1000 lbs. /acre in unfavorable years to about 2000 lbs. /acre in above average years. This state is stable and protected from excessive erosion. The biotic integrity of this plant community is in intact. However, a slight decline in the cottonwood reproduction is evident and may affect the vigor of the stand over a long period. 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. Transitional pathways leading to other plant communities are as follows: • Prescribed grazing and reoccurrence of periodic flooding will result in a plant community very similar to the Historic Climax Plant Community. • Wildfires will convert this plant community to the Cottonwood Sapling/Riparian Shrub Regeneration Plant Community. Usually cottonwood sapling regeneration is relatively rapid unless the soils are sterilized. In this case, revegetation of the site is slow and may take many years. Low intensive or ground fires will result in thinning of the cottonwood stand and provide microsites, which can be quickly colonized by new saplings. These fires usually result in a mixed-aged stand of mature or younger trees with a sapling understory. Moderate or severe fires, however, usually will result in total stand mortality as cottonwoods are not very resistant to high temperatures. Under these scenarios, cottonwood seedlings can still quickly become established, if the soils are not sterilized and an even aged stand will result. As a result of any wildfire, shrubs can also play an important role as to what plants will emerge first and what the species composition will develop into after fire succession. • Frequent and severe grazing and flooding with no fire will convert this plant community to a Kentucky Bluegrass Sod/ Riparian Shrub Plant Community. • Frequent and severe grazing plus channelization or infrequent flooding plus encroachment, will convert this plant community to the Russian Olive/Dense Shrub Plant Community. This transition to a more regulated hydrologic regime favors the proliferation of Russian olive and if a seed source is available, colonization will usually occur.

State 3
Cottonwood Sapling/Riparian Shrub Regeneration Plant Community

Community 3.1
Cottonwood Sapling/Riparian Shrub Regeneration Plant Community

Historically, this plant community is the result of a natural fire regime within a riparian community. These plant communities existed as part of the natural fire regime and were relatively short lived and were usually less intense. Currently, fire suppression management has resulted in more fuels and when fire does occur these fires are more intense. Subsequently, many areas today burn hotter and revegetation succession is prolonged. Cottonwoods are normally a relatively rapid regenerator as are many of the riparian shrubs, unless the soils are sterilized during severe and high intensive fires. Low intensive or ground fires will result in thinning of the cottonwood stand and provide microsites, which can be quickly colonized by new saplings. These fires usually result in a mixed-aged stand of mature or younger trees with a sapling understory. Moderate or severe fires, however, usually will result in total stand mortality as cottonwoods are not very resistant to high temperatures. Under these scenarios, cottonwood seedlings can still quickly become established, if the soils are not sterilized and an even aged stand will result. As a result of any wildfire, shrubs can also play an important role as to what plants will emerge first and what will the species composition develop into after fire succession. As this is a dynamic community, the plant composition will vary. The effects of fire in these plant communities have not been adequately studied and the understanding of fire succession is minimal. Dominant grasses may include streambank wheatgrass, rhizomatous wheatgrasses, needleandthread, and bottlebrush squirreltail. Grasses of secondary importance include Sandberg bluegrass and big bluegrass. A variety of riparian species will regenerate and may become dense during this regeneration process. Cottonwood stands will be variable depending on the intensity of the fire. Weeds such as cheatgrass or noxious weeds such as Russian knapweed, Canada thistle, and leafy spurge may become established and should be treated. The total annual production (air-dry weight) of this state varies depending on the stage of the succession but about 800 pounds per acre is normal. It can range from about 1800 lbs. /acre in unfavorable years to about 600 lbs. /acre in above average years. This state is not stable and is part of a transition. Erosion may be excessive until the site is revegetated. Erosion control may be necessary if soil loss is excessive, however, be aware that cottonwood regeneration depends on exposed bare soil. The biotic integrity of this plant community is in intact. The watershed is functioning. Transitional pathways leading to other plant communities are as follows: • No fire plus prescribed grazing will result in a plant community very similar to the Historic Climax Plant Community. Periodic flooding will hasten this transition. • No fire plus frequent and severe grazing and/or channelization or infrequent flooding will convert this plant community to a Dense Shrub/Warm Season Grass Plant Community. • Fire will keep this in the Cottonwood Sapling/Riparian Shrub Regeneration Plant Community.

State 4
Kentucky Bluegrass Sod/Over-Mature Cottonwood Stand Plant Community

Community 4.1
Kentucky Bluegrass Sod/Over-Mature Cottonwood Stand Plant Community

This plant community is the result of long-term improper grazing use. The hydrologic features of this site are relatively still functioning as flooding is occurring at similar frequency as in the past. This plant community is dominated by a dense short grass sod of Kentucky bluegrass and includes a mosaic of mature cottonwoods and riparian shrub overstory. Weedy forbs are prevalent and noxious weeds such as Russian knapweed, Canada thistle, and leafy spurge may invade the site if a seed source is available. Shrub species include big and silver sagebrushes, silver buffaloberry, willows, western snowberry, and wild rose. The cottonwood stands consists of old-growth trees which are in a state of decline. Standing dead, dying branches and downed trees are evident. When compared to the Historic Climax Plant Community, the tall and medium grasses are reduced or absent. Short warm season grasses are dominant and weedy annuals are common. Shrubs will have increased as a percentage of the total production, but will not dominate as the sod prevents a homogeneous shrub cover. Areas of bare ground may have increased in patches, and total production has decreased. Russian olive may begin invading this site if conditions are right and left uncontrolled will begin the process of displacing cottonwoods as the main tree species. Total production is only slightly reduced as Kentucky bluegrass offsets the loss of tall and mid perennial grasses. The total annual production (air-dry weight) of this state is about 1200 pounds per acre, but it can range from about 900 lbs. /acre in unfavorable years to about 1600 lbs. /acre in above average years. The sod component of this plant community is extremely resistant to change and continued frequent and severe grazing or the removal of grazing does not seem to affect the plant composition or structure of the plant community. The biotic integrity of this state is mostly not functional as plant diversity is poor, especially the amount of herbaceous species. The vegetative structure is not intact as the cottonwoods are not reproducing due to the sod. The shrub component may still be within a reasonable percentage of the total composition as the HCPC. This sod bound plant community is very resistant to water infiltration. While this sod protects the site itself, excessive runoff increases erosion on bare ground and can cause rill channels and gully erosion. Water flow patterns are obvious in the bare ground areas and shrubs and sod patches are pedestalled. Rill channels are noticeable in the interspaces and gullies may be establishing where rills have concentrated. The watershed may or may not be functioning, as runoff is excessive and erosional processes are accelerated. Transitional pathways leading to other plant communities are as follows • Grazing land mechanical treatment, plus prescribed grazing and/or brush management or wildfire will convert this plant community in to the Cottonwood Sapling/Riparian Shrub Regeneration Plant Community. This sod is extremely resistant to change and will require grazing land mechanical treatments, such as chiseling to revert to a more preferred state. Reseeding areas with native plant species is also recommended as well as implementing proper grazing management to accelerate recovery where few desirable plants remain. Fire may also be necessary to open up areas dominated by riparian shrubs so cottonwood seedling can again be established. • Frequent and severe grazing plus channelization or infrequent flooding plus no encroachment, will convert this plant community to the Dense Shrub/Warm-Season Grass Plant Community. • Frequent and severe grazing plus channelization or infrequent flooding plus encroachment, will convert this plant community to the Russian Olive/Dense Shrub Plant Community. This transition to a more regulated hydrologic regime favors the proliferation of Russian olive and if a seed source is available, colonization will usually occur.

State 5
Dense Shrub/Warm-Season Grass Plant Community

Community 5.1
Dense Shrub/Warm-Season Grass Plant Community

This plant community evolved under frequent and severe grazing and an interruption in the frequency of flooding or channelization and no encroachment of Russian olive. The disruption, either directly by humans, such as dams or dikes, or indirectly through accelerated erosion and down cutting of the hydrologic system, has caused channelization and an interruption in the natural flooding regime. Extended periods of drought will exacerbate this situation. Shrubs dominate but the composition depends on the characteristic of the site. Sites with coarser soils are usually dominated by both basin big sagebrush and silver sagebrush and heavier soils by both basin big sagebrush and rubber rabbitbrush. Tall and medium cool season grasses have been reduced or eliminated. Dense sod patches of blue grama occur amongst the shrubs and bare ground. The annual grasses and forbs, such as cheatgrass, kochia, halogeton, and Russian thistle, are prevalent along with noxious weeds such as Russian knapweed. Total annual production is mostly from shrubs and warm-season grasses. Shrubs make up more than 35% of the total annual production. When compared with the HCPC, the annual production is reduced but the dense shrub component makes up for some of this loss in total production. The total annual production (air-dry weight) of this state is about 800 pounds per acre, but it can range from about 500 lbs. /acre in unfavorable years to about 1200 lbs. /acre in above average years. This plant community is resistant to change as the stand becomes more decadent. These areas may actually be more resistant to fire as less fine fuels are available and the bare ground between the shrubs is increased. Continued frequent and severe grazing or the removal of grazing does not seem to affect the plant composition or structure of the plant community. Warm-season grasses, weedy species and bare ground compromise the biotic integrity. Plant diversity is poor and the potential for native grasses to reproduce is absent. The shift in the vegetative structure and function is extreme and the biotic integrity is lost. The soil of this state is somewhat protected where the sod patches are located but erosion has accelerated between these patches where bare ground is common. Water flow patterns and pedestalling are obvious. Infiltration is reduced and runoff is increased. Rill channels may be noticeable in the interspaces and gullies may be establishing where rills have concentrated. Transitional pathways leading to other plant communities are as follows: • Brush management plus prescribed grazing will convert this plant community to a Cool-Season Grass/Mixed Shrub Plant Community. • Recovery to near Historic Climax Plant Community condition is impractical as the hydrologic regime has been disturbed.

State 6
Cool-Season Grass/Mixed Shrub Plant Community

Community 6.1
Cool-Season Grass/Mixed Shrub Plant Community

This plant community can occur where the Dense Shrub/Warm-Season Grass Plant Community under goes brush management treatment and a prescribed grazing management practice is implemented. Preferred cool season grasses have reestablished and shrubs have been controlled but are still a part of the community. Upland plants now dominate as the hydrologic regime has been disrupted and only infrequent or no flooding occurs. This site is dominated by an overstory of a variety of shrubs, such as basin big sagebrush, rubber rabbitbrush, and silver sagebrush. Perennial cool season mid-grasses have once again reestablished such as rhizomatous wheatgrasses, needleandthread, and bottlebrush squirreltail. Other important grasses include Sandberg bluegrass and blue grama. Patches of annuals such as cheatgrass and other weedy annual forbs such as halogeton, Russian thistle, and kochia, will persist on this site. Noxious weeds such as Russian knapweed may also remain, if not treated. The interspaces between plants will have diminished in size. When compared with the HCPC, the annual production has been significantly reduced and the plant species are clearly unique. The total annual production (air-dry weight) of this state is about 1000 pounds per acre, but it can range from about 600 lbs./acre in unfavorable years to about 1400 lbs./acre in above average years. 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. Transitional pathways leading to other plant communities are as follows: • Frequent and severe grazing will convert this plant community to the Dense Shrub/Warm-Season Grass Plant Community. Prolonged drought will exacerbate this transition. • Recovery to near Historic Climax Plant Community condition is impractical as the hydrologic regime has been disturbed.

State 7
Russian Olive/Dense Shrub Plant Community

Community 7.1
Russian Olive/Dense Shrub Plant Community

This plant community is the result of a disruption in the hydrologic system of the watershed and usually improper grazing use. The disruption, either directly by humans, such as dams or dikes, or indirectly through accelerated erosion and down cutting of the hydrologic system, has caused channelization and an interruption in the natural flooding regime. Normal flooding patterns are no longer possible, which is a main feature of this ecological site and a must for cottonwood recruitment. Without normal flooding Russian olive proliferate and colonize the site. Shrubs can be common and dense, but the composition varies depending on the characteristic of the site. Sites with coarser soils are usually dominated by both basin big sagebrush and silver sagebrush and heavier soils by both basin big sagebrush and rubber rabbitbrush. Past cottonwood galleries now are comprised mostly of mature dying trees or standing dead. Russian olive comprise the main overstory tree-like species and basin big sagebrush, silver sagebrush, and rubber rabbitbrush comprise the main shrub species. The understory is made up of primarily short warm season grasses or cheatgrass. Noxious weeds have invaded the site such as Russian knapweed, Canada thistle, and leafy spurge. The interspaces between plants increases in size leaving mostly bare ground, which is exposed to erosion or further invasion by weedy plants. Plant diversity is poor. When compared with the HCPC, the annual production is reduced as the tall and mid-grasses have been replaced, but the Russian olive and shrub production compensates for some of the decline in the herbaceous production. The total annual production (air-dry weight) of this state is about 1000 pounds per acre, but it can range from about 750 lbs./acre in unfavorable years to about 1200 lbs./acre in above average years. This plant community is resistant to change as the Russian olive stand becomes more dominant. These areas may actually be more resistant to fire as less fine fuels are available and the bare ground between the shrubs is increased. Continued frequent and severe grazing or the removal of grazing does not seem to affect the plant composition or structure of the plant community. Russian olive, annual grasses, weedy species and bare ground compromise the biotic integrity. Plant diversity is poor and the potential for native tall and mid perennial grasses to reproduce is absent. The shift in the vegetative structure and function is extreme and the biotic integrity is lost. The watershed is not functioning correctly, as the normal flooding regime is eliminated. Infiltration is reduced and excessive runoff is common. The biotic integrity is lacking and invasive species are widespread. Transitional pathways leading to other plant communities are as follows • Brush management plus prescribed grazing and seeding if necessary will convert this plant community to a Perennial Grass/Russian Olive Plant Community. Russian olive plants will continue to be a main component of this community as suppression or containment of this plant is usually temporary and will not result in total eradication. • Recovery to near Historic Climax Plant Community condition is impractical as the return to a natural hydrologic regime is too expensive or not possible. Any methods of Russian olive control should be followed by revegetation to reduce regeneration of this plant and other weedy species.

State 8
Perennial Grass/Russian Olive Plant Community

Community 8.1
Perennial Grass/Russian Olive Plant Community

This plant community occurs where control of Russian olive and/or shrubs has been successful, but the natural hydrologic regime has not and will not return to pre-channelization or to a periodic flooding regime. Russian olives are confined to localized patches. Mid-grasses have returned but the tall grasses associated with riparian areas have been removed. Upland species are now the dominant plants. These plants make up the understory species in this plant community. Dominant grasses include rhizomatous wheatgrasses, needleandthread, and bottlebrush squirreltail. Other grasses include Sandberg bluegrass, blue grama and threadleaf sedge. Forbs commonly found in this plant community include smooth woodyaster, scarlet globemallow fringed sagewort, hairy goldaster and phlox. Willows have been replaced as have the other riparian shrubs. When compared to the Historical Climax Plant Community, the production of perennial grasses and total production have been greatly reduced. The total annual production (air-dry weight) of this state is about 1000 pounds per acre, but it can range from about 600 lbs./acre in unfavorable years to about 1600 lbs./acre in above average years. This plant community is mostly resistant to change, but species composition can be altered by encroachment and improper grazing. The herbaceous component is stable, but does not comprise the composition of HCPC. Plant vigor and replacement capabilities are sufficient. The biotic community is not intact because the tall grasses associated with the riparian areas are absent and Russian olive is still a part of the plant community. Plant diversity is moderate. Soils are mostly stable and recent soil loss is minimal. Water flow patterns and litter movement is stable. Incidence of pedestalling is improving. The watershed is not functioning due to disruption in the hydrologic regime. Transitional pathways leading to other plant communities are as follows: • Frequent and severe grazing plus encroachment will convert this plant community to the Russian Olive/Dense Shrub Plant Community. Drought will exacerbate this conversion. • Recovery to near Historic Climax Plant Community is impractical as the return to a natural hydrologic regime is too expensive or not possible.