LOAMY 11-13

Description

The Reference State is a representative of the natural range of variability under pristine conditions. State dynamics are maintained by interactions between climatic patterns and disturbance regimes. Negative feedbacks enhance ecosystem resilience and contribute to the stability of the state. These include the presence of all structural and functional groups, low fine fuel loads, and retention of organic matter and nutrients. Plant community phase changes are primarily driven by fire, periodic drought and/or insect or disease attack.

Characteristics and indicators

This state is dominated by basin big sagebrush and bluebunch wheatgrass.

Submodel

Description

This state is similar to the Reference State 1.0. Ecological function has not changed, however the resiliency of the state has been reduced by the presence of invasive weeds. These non-natives can be highly flammable, and can promote fire where historically fire had been infrequent. Negative feedbacks enhance ecosystem resilience and contribute to the stability of the state. These include the presence of all structural and functional groups, low fine fuel loads and retention of organic matter and nutrients. Positive feedbacks decrease ecosystem resilience and stability of the state. These include the non-natives’ high seed output, persistent seed bank, rapid growth rate, ability to cross pollinate and adaptations for seed dispersal.

Resilience management

Best management will maintain high diversity of desired species to promote organic matter inputs and prevent the dispersal and seed production of the non-native invasive species.

Description

This state is characterized by the dominance of shallow rooted perennial bunchgrass, which have replaced the deep-rooted perennial bunch grass typical of the site. Big sagebrush and rabbitbrush dominate the overstory. Bluegrass species dominate understory with non-native species present.

Characteristics and indicators

Sandberg bluegrass has been found to increase following fire likely due to its low stature and productivity (Daubenmire 1975). Sandberg bluegrass may retard reestablishment of deeper rooted bunchgrass. Reduced bunchgrass vigor or density provides an opportunity for Sandberg bluegrass expansion and/or cheatgrass and other invasive species to occupy interspaces.

Description

Annual non-natives dominated site productivity and site resources. The dominance of non-native annuals control the spatial and temporal distribution of soil moisture, soil nutrients and energy resources. Remaining patches of sagebrush and/or perennial bunchgrass suffer from increased competition and narrowed fire return intervals.

Characteristics and indicators

This state experiences frequent fire due to increased cover and continuity of fine fuels. Fire is frequent enough to prevent the recovery of long-lived native perennials like big sagebrush. Disturbance tolerant shrubs may be present or increasing depending on time since disturbance. As cheatgrass increases, fire frequencies also increase. As cheatgrass increases, fire frequencies also increase to frequencies between 0.23 and 0.43 times a year; then even sprouting shrubs such as rabbitbrush will not survive (Whisenant 1990).

Description

This state is characterized by the dominance of non-native perennial wheatgrass species, like crested wheatgrass (Agropyron cristatum) or desert wheatgrass (Agropyron desertorum). Non-native perennial wheatgrass are frequently seeded following disturbance for erosion control and forage. These seed species are long-lived and persistent in the plant community and are able compete with native perennial bunchgrass spatial and limited soil moisture resource. Native species, grass and forbs, may still be present in small amounts.

Submodel