State 1
Reference

State 1 represents sagebrush steppe with no invasive or exotic weed species. Communities with heavy sagebrush or a dominance of annual grasses have never been seen on Shallow Stony. Reference community 1.1 is dominated by bluebunch wheatgrass and Wyoming sagebrush. Reference State Community Phases: 1.1 Reference Bluebunch wheatgrass-Wyoming sagebrush Dominate Reference State Species: Wyoming big sagebrush (overstory) and bluebunch wheatgrass At-risk Communities: • Any community in the reference state is at risk of moving to State 2. The seed source of cheatgrass is nearby and blowing onto most sites annually. • Reference community is quite stable as it receives limited grazing pressure and rarely burns • State 3 has not been seen on Shallow Stony sites in the sagebrush steppe region

Community 1.1
Bluebunch Wheatgrass, Wyoming Big Sagebrush, Sandberg Bluegrass, and Perennial Forbs

State 2
Sagebrush Steppe with Invasive Species

State 2 represents sagebrush steppe, similar to the Reference State, but with the inclusion of minor amounts of invasive annual grasses such as cheatgrass. Most Shallow Stony sites never cross the threshold into State 2. They stay at climax or near climax condition, as these sites generally receive limited grazing pressure and rarely burn. Community Phases for State 2: 2.1 Reference w/ Annual Grasses Bluebunch wheatgrass-Wyo. sagebrush Dominate Species in State 2: Bluebunch wheatgrass, Wyoming sagebrush

Community 2.1
Bluebunch Wheatgrass, Wyoming Big Sagebrush, Perennial Forbs, and Cheatgrass

State 3
Invasive Annual Grasses

State 3 represents sites that have invasive annual grasses and sagebrush as co-dominants, and have crossed a biological threshold. State 3 is rare for Shallow Stony sites. Cheatgrass is the major invasive species. Mustard, prickly lettuce or diffuse knapweed may also be present. Invasive annual grasses such as cheatgrass, are not as competitive as on adjoining deeper ecological sites. But a micro-burst of cheatgrass can occur. Cheatgrass seed blows onto Shallow Stony sites annually. In a year with heavy snowfall and early spring rain, such as 2017, the site has far more moisture than the plant community can utilize. This is the opportunity for cheatgrass seed to germinate and produce a huge flush of cheatgrass plants. In following years when moisture is normal or below normal cheatgrass seed will not germinate or make viable plants. So, these micro-bursts of cheatgrass are episodic and mostly a temporary condition in MLRA 8 Shallow Stony sites. Within a couple of years cheatgrass will be nonexistent to at most a very minor component. Community Phases for State 3: Shrub – Annual Grass Wyoming sagebrush – cheatgrass Dominate Species in State 3: Cheatgrass, Wyoming sagebrush State 3 is considered non-reversible. Due to shallow soil depth, surface rock and rock within the soil profile, and the equipment limitations thereof, seeding is not practical for the Shallow Stony ecological site. Restoration of bluebunch wheatgrass, sagebrush, native forbs and the soil biotic crust would be very problematic at best on Shallow Stony. Seeds must germinate. Seedlings and plugged plants need soil moisture and time to become established. In most years, seeds and plugs may not have a chance as site conditions on Shallow Stony can change quickly. Drying winds and bright sun can turn a snowy or muddy site into a hard crust before plants are established. So, the timing of all recovery efforts would have an extremely narrow window of opportunity on Shallow Stony. Perhaps the only avenue for recovery would be to plant plugs of native species which is a very costly and risky proposition.

Community 3.1
Cheatgrass and Shrubs

Transition T1A
State 1 to 2

Result: shift from State 1 (bunchgrass-shrub) to State 2 with minor additions of cheatgrass. Primary Triggers: A high moisture year causes a micro-burst of cheatgrass and is the principle means of colonization. Loss of soil biological crusts contributes to the invasion. Also, soil disturbances (rodents, badgers) create openings in the community and encourage weed germination. Ecological process: Most sites in the Reference State have cheatgrass seed as the seed blows onto the sites annually. Cheatgrass is a prolific seeder and the seed is waiting for enough moisture to germinate and to compete with the native species for space, light and moisture. When there is more moisture available than the plant community can utilize, even pristine communities in the Reference State are susceptible to colonization by cheatgrass. The addition of cheatgrass to the community is generally a temporary condition on Shallow Stony sites. Indicators: The occurrence of annual grasses on sites where they had been absent.

Transition T2A
State 2 to 1

Result: shift from State 2 community with minor amount of cheatgrass back to State 1 community with no cheatgrass. Primary Trigger: normal to below normal precipitation year. Ecological process: with normal to below normal precipitation the native species in the community utilize all available moisture and cheatgrass is unable to compete with the native species.

Transition T2B
State 2 to 3

Result: Shift from State 2 to State 3 which is dominated by annuals. State 3 is rare and has not been seen on Shallow Stony sites. This transition occurs once the cover of invasive species is co-dominate with sagebrush and the cover of bluebunch wheatgrass is minor. Primary Trigger: Chronic heavy grazing, season-long grazing, or late spring grazing causes poor vigor and bluebunch wheatgrass has a significant reduction in cover. Ecological Process: With consistent defoliation pressures bluebunch wheatgrass cover declines due to shrinking crowns and some mortality. More and more of the soil surface and upper soil rooting surface become open to opportunistic, exotic weeds that take advantage of the available niche space to colonize and expand. The invasive annual grasses in State 2 communities make a dramatic increase to dominate the community. Indicators: Decreasing cover of bluebunch wheatgrass and increasing cover of invasive annual species. Increasing distance between perennial bunchgrass plants. Decreasing soil organic matter, soil water retention, limited water infiltration and percolation in the soil profile.