Ecological dynamics

The dominant visual aspect of this site is an herbaceous layer with a variety of grasses and forbs. Idaho fescue is the dominant grass. There are no shrubs. Composition by weight is approximately 50 to 60 percent grasses and 40 to 50 percent forbs.

During the last few thousand years, this site has evolved in a montane climate characterized by dry summers and cold, moist winters with long periods of high winds. Herbivory has historically occurred on this site at low levels of utilization. Herbivores include mule deer, Rocky Mountain elk, and lagomorphs.

Fire has historically occurred on the site at intervals of 20 - 50 years.

The Historical Climax Plant Community (HCPC), 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 with Raynolds’ sedge, elk sedge, ovalhead sedge, and prairiesmoke being prevalent. The plant community is very diverse and there are a large variety of other grasses and forbs in minor amounts. The plant species composition of Phase A is listed later under “Reference Plant Community Phase Plant Species Composition”.

Total annual production is 1100 pounds per acre (1232 kilograms per hectare) in a normal year. Production in a favorable year is 1700 pounds per acre (1904 kilograms per hectare). Production in an unfavorable year is 500 pounds per acre (560 kilograms per hectare). Structurally, cool season deep-rooted perennial bunchgrasses are more dominant than forbs.


FUNCTION:

Big game animals use the site in the spring because it is the one of the first sites to warm up and is clear of snow. This allows plant growth to start earlier. Livestock use is best suited for spring and fall. This site has little value for recreational value except for some hiking.

Due to ease of access, this site is susceptible to degradation from improper grazing management. The site has slight to moderate limitation for livestock grazing. Runoff, when it does occur can be erosive particularly during high intensity summer convection storms.

Impacts on the Plant Community.

Influence of fire:

In the absence of normal fire frequency and ungulate grazing, Idaho fescue can become decadent. This is apparent by dead centers in the crown.

When fires become more frequent than historic levels (20-50 years), Idaho fescue can be reduced in the plant community. With continued short fire frequency, this species can be completely eliminated along with some forbs. These species may be replaced by a variety of annual and perennial forbs including noxious and invasive species. These fine fuels will cause fires to become more frequent. Kentucky bluegrass may invade the site. Raynolds’ sedge, elk sedge, ovalhead sedge, and other rhizomatous species will usually increase.

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, an increase in many forbs will occur and noxious and invasive plants will invade. Kentucky bluegrass may invade the site.

Continued improper grazing management influences fire frequency by increasing fine fuels that carry fires. As annuals increase, fires become more frequent.

Proper grazing management that addresses frequency, duration, and intensity of grazing can also keep fine fuels from developing, thereby reducing fire frequency. A planned grazing system can be developed to intentionally accumulate fine fuels in preparation for a prescribed burn. A prescribed burn on this specific site would only occur under extremely rare circumstances.

Weather influences:

Above normal precipitation in 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.

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:

Outbreaks can affect vegetation health. 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.

Influence of wildlife:

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

Watershed:

Decreased infiltration and increased runoff occur with a decrease in perennial bunchgrasses. This composition change can affect nutrient and water cycles. Increased runoff also causes sheet and rill erosion. Abnormally short fire frequency also gives the same results, but to a lesser degree. The long-term effect is a transition to a different state.


Plant Community and Sequence:

Transition pathways between common vegetative 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 or C to State 2. Develops through frequent fire and/or continued improper grazing management. This site has crossed a vegetative threshold. It is economically impractical to return this plant community to 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 economically impractical to return this plant community to State 1 with accelerating practices.


Practice Limitations:

Moderate to severe limitations exist on this site for accelerated practices due to low available soil moisture due to the wind drying the surface soils. Slight limitations exist for facilitating and vegetative management practices.