Ecological dynamics

The potential native plant community is dominated by stiff sagebrush, Sandberg bluegrass and one-spike oatgrass. Idaho fescue is common. Bluebunch wheatgrass, bottlebrush squirreltail and a variety of forbs are present. Vegetative composition of the community is approximately 65 percent grasses, 10 percent forbs and 25 percent shrubs. Approximate ground cover is 40 to 60 percent (basal and crown). There is a strong diversified soil microbiotic crust on the interspaces between plant bases.

Range in Characteristics:
Plant composition and production is dependent on soil depth, precipitation and bedrock fracture. As soil depth decreases to 4 to 6 inches, Sandberg bluegrass increases. Onespike oatgrass increases at similar depths at higher precipitation and in areas receiving additional spring runoff. Idaho fescue and scabland (stiff) sagebrush will increase on deeper soils closer to 10 inches deep and over fractured bedrock. Bluebunch wheatgrass increases at lower elevations and on slight south and west exposures. Production increases with soil depth and precipitation. Natural fire frequency is low approximating 100 years being dependent on soil depth and production, fine fuel build-up and favorable fire conditions.

Response to Disturbance-States:
If the condition of the site deteriorates as a result of overgrazing, one-spike oatgrass and Idaho fescue initially decrease. Sandberg bluegrass and stiff sagebrush increase. Junipers invade on deeper soils with fire suppression and the lack of adequate fine fuels to carry a fire. With continued overgrazing scattered bluebunch wheatgrass and Thurber’s needlegrass decrease. Stiff sagebrush and Sandberg bluegrass subsequently decrease and bare soil increases. Annual invasion is limited except in seasonal moist drainage areas where ventenata and medusahead may invade. Soil microbiotic crusts are easily disturbed and broken up, particularly by early spring grazing on saturated soils. Accelerated soil erosion on the bare soil interspaces markedly increases, reduces potential site productivity and contributes to downstream sedimentation.

States: ARRI2/POSE-Bare Ground; JUOC/ARRI2/POSE-Bare Ground;

Treatment Response:
The repair pathways from State 2 back to State 1 indicates the need for brush management along with seeding. State 3 back to State 1 will require mechanical and/or chemical treatment of the annual grasses plus seeding. Due to the extremely shallow soils on this site, the potential for seeding failure is medium to high. Maintaining an adequate stand of perennial grasses through prescribed grazing and other management practices are the best approaches to optimizing the economic returns from this site.

Reference Plant Community
There are three phases in the reference state. Phase 1.1 is the perennial grass and forb phase dominated by perennial bunchgrasses with stiff sagebrush being common. Phase 1.2 the stiff sagebrush doiminant phase, results from reduced fire and improper grazing management. Phase 1.3 has an increase in stiff sagebrush and a reduction in the perennial bunchgrasses as a result of no fire and continued improper grazing management.

Phase 1.1 the perennial grass and forb phase, the reference plant community is dominated by one-spike oatgrass, Sandberg bluegrass, Idaho fescue and bluebunch wheatgrass in the understory and stiff sagebrush in the overstory. Vegetative composition of the plant community is approximately 65 percent grasses, 15 percent forbs and 20percent shrubs. The perennial grasses control the ecological processes in this phase.

Phase 1.2 the stiff sagebrush dominant phase results from reduced fire and improper grazing. With fire and prescribed grazing the plant community will move back towards Phase 1.1 (1.2A). With continued lack of fire and improper grazing management the community transitions to Phase 1.3 (1.2B). The perennial grasses and stiff sagebrush control the ecological processes in this phase.

Phase 1.3 the stiff sagebrush-fire prone phase happens as a result of no fire and improper grazing from phase 1.2 (1.2B). With no fire and prescribed grazing, the plant community will move back (1.3B) towards Phase 1.2. Fire and prescribed grazing will move the plant community back (1.3A). towards Phase 1.1. This phase is the “at risk” plant community in State 1. With lack of fire, continued improper grazing and/or drought the community will transition (IRT1A) to State 2. Frequent fire with or without prescribed grazing will move the plant community to State 3 which is the annual grass dominated state. Stiff sagebrush controls the ecological processes in this phase.

State 2 is dominated by stiff sagebrush and it controls the ecological processes on the site. Frequent fire will move the plant community (IRT2A) to State 3, the annual grass dominated state. The one repair pathway (RP2) back to State 1 involves brush management and seeding with native species. Due to the shallow soils this repair pathway would have a high risk of failure and is not economically feasible.

State 3 is the annual grass dominated state and these grasses control all of the ecological processes. A repair pathway (RP3) to State 1 requires chemical and/or mechanical control of the annual grasses and seeding of native species to move it back to State 1. Again, due to the shallow soils this practice has a high risk of failure and is not economically feasible.