Ecological dynamics

The dominant visual aspect of this site has a grass and forb aspect. Idaho fescue and bluebunch wheatgrass are dominant. The site has a variety of forbs. The bluebunch wheatgrass on the site is usually rhizomatous. Composition by weight is approximately 65-75 percent grass, 20-30 percent forbs, and 0-10 percent shrubs.

During the last few thousand years, this site has evolved in a semi-arid climate characterized by dry summers and cold, moist winters. Herbivory has historically occurred on this site at low levels of utilization. Herbivores include mule deer, Rocky Mountain elk, lagomorphs, and small rodents.

Fire has historically occurred on the site at intervals of 20-40 years.

The Reference State (State 1), moves through many phases depending on the natural and man-made forces that impact the community over time. State 1, described later, indicates some of these phases. The Reference Plant Community Phase is Phase A. This plant community is dominated by Idaho fescue and bluebunch wheatgrass. Common snowberry occurs as scattered patches on the site. Subdominant species include arrowleaf balsamroot, yarrow, geranium, cinquefoil, lupine, and oldmans whiskers. The plant species composition of Phase A is listed later under “Reference Plant community Phase Plant Species Composition”.

Total annual production is 1300 pounds per acre (1440 kilograms per hectare) in a normal year. Production in a favorable year is 1500 pounds per acre (1670 kilograms per hectare). Production in an unfavorable year is 1100 pounds per acre (1220 kilograms per hectare). Structurally, cool season deep rooted perennial bunchgrasses are very dominant, followed by perennial forbs being much more dominant than tall shrubs.




This site is suited for grazing by domestic livestock in late spring, summer, and fall. This site is important spring, summer, and fall range for big game. During the spring and summer it is important habitat for chukars and Hungarian partridge. Mourning doves, bald eagles, and Merriam’s turkey also frequent the site. This site has high value for chukar, Hungarian partridge, quail, and big game hunting. Aesthetic values are good. A large variety of flora is present which have flowers that bloom in spring and early summer. The site position offers an excellent view of the surrounding countryside. The site is popular as a hiking area because of the variety of views and activities offered.

The site is fairly resistant to disturbances that can potentially degrade it as long as a good herbaceous cover is retained.


Impacts on the Plant Community.

Influence of fire:

In the absence of fire and/or grazing, bluebunch wheatgrass and Idaho fescue can become decadent due to build-up of old residues in the crown.

In the absence of normal fire frequency, snowberry and Woods’ rose, if present, can increase to the point of being co-dominant with bluebunch wheatgrass and Idaho fescue on the site. When present, rose and snowberry also will develop into patches on the site.

When fires become more frequent than historic levels (20-40 years), Idaho fescue and bluebunch wheatgrass are reduced significantly. With continued short fire frequency, some of the strong root-sprouting shrubs will form dense thickets and will further reduce the grass component.

Influence of improper grazing management:

Season-long grazing and/or excessive utilization can be very detrimental to this site. This type of management leads to reduced vigor of the bunchgrasses. With reduced vigor, recruitment of these species declines. As these species decline, the plant community becomes susceptible to an increase in root-sprouting shrubs and noxious and invasive plants.

Continued improper grazing management influences fire frequency by increasing fine fuels.

Proper grazing management that addresses frequency, duration, and intensity of grazing can also keep fine fuels from developing, thereby reducing fire frequency. This can lead to gradual increases in the shrub component. A planned grazing system can be developed to intentionally accumulate fine fuels in preparation for a prescribed burn. Prescribed burns need careful planning. Areas without a suitable understory of perennial grasses are low priority areas for prescribed burns, especially if reseeding is not a possibility.


Weather influences:

Above normal precipitation in April, May, and June can dramatically increase total annual production of the plant community. These weather patterns can also increase viable seed production of desirable species to provide for recruitment. Likewise, below normal precipitation during these spring months can significantly reduce total annual production and be detrimental to viable seed production. Overall plant composition is normally not affected when perennials have good vigor.

Below normal temperatures in the spring can have an adverse impact on total production regardless of the precipitation. An early, hard freeze can occasionally kill some plants.

Prolonged drought adversely affects this plant community in several ways. Vigor, recruitment, and production are usually reduced. Mortality can occur. Prolonged drought can lead to a reduction in fire frequency.

Influence of insects and disease:

Grasshopper outbreaks occur periodically. Outbreaks seldom cause plant mortality since defoliation of the plant occurs only once during the year of the outbreak.


Influence of noxious and invasive plants:

Many of these species add to the fine-fuel component and lead to increased fire frequency.
Annual and perennial invasive species compete with desirable plants for moisture and nutrients. The result is reduced production and change in composition of the understory. Kentucky bluegrass is very competitive on this site. Because of its shallow root system it prevents establishment of desirable, more productive bunchgrasses such as Idaho fescue and bluebunch wheatgrass.

Influence of wildlife:

Big game animals use this site in the spring, summer, and fall. Their numbers are seldom high enough to adversely affect the plant community.


Watershed:

Decreased infiltration and increased runoff occur with the loss of the perennial grasses and the shrub component. This is most likely caused by an abnormally short fire frequency brought on by the replacement of perennial grasses with annual grasses. The long-term effect is a transition to a different state.


Plant Community and Sequence:

Transition pathways between common vegetation states and phases:

State 1.
Phase A to B. Develops with improper grazing management and no fire.
Phase A to C. Develops with fire.
Phase B to A. Develops with prescribed grazing.
Phase C to A. Develops with prescribed grazing and no fire.
State 1 Phase B to State 2. Develops through frequent fire and continued improper grazing management. The site has crossed the threshold. It is not economically feasible to move this state back towards State 1 with accelerating practices.

State 1 Phase C to State 2. Develops through frequent fire or continued improper grazing management. The site has crossed the threshold. It is not economically feasible to move this state back towards State 1 with accelerating practices.

State 1 Phase B to State 3. Develops through continued improper grazing management. The site has crossed the threshold. It is not economically feasible to move this state back towards State 1 with accelerating practices.

State 2 to unknown site. Excessive soil loss and changes in the hydrologic cycle caused by continued improper grazing management and/or frequent fire cause this state to cross a threshold and retrogress to a new site with reduced potential. It is not economically feasible to move this state back towards State 1 with accelerating practices.


Practice Limitations.

Severe limitations exist on this site for seeding and brush control using conventional ground moving equipment due to steep slopes greater than 30 percent.