SR Shrubby Mountain Loam 16-20 PZ

Description

The Reference State 1.0 is a representation of the natural range of variability under pristine conditions. The reference state has three general community phases; a shrub-grass dominant phase, a perennial grass dominant phase and a shrub dominant phase. 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. Negative feedbacks enhance ecosystem resilience and contribute to the stability of the state. These feedbacks include the presence of all structural and functional groups, low fine fuel loads, and retention of organic matter and nutrients.

Dominant plant species

1. antelope bitterbrush (Purshia tridentata), shrub

2. mountain big sagebrush (Artemisia tridentata ssp. vaseyana), shrub

3. Idaho fescue (Festuca idahoensis), grass

Submodel

Description

This state is similar to the Reference State 1.0 with three similar community phases. Ecological function has not changed, however the resiliency of the state has been reduced by the presence of invasive weeds. Non-natives may increase in abundance but will not become dominant within this State. 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 feedbacks 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, residual dry matter accumulation, and adaptations for seed dispersal.

Dominant plant species

1. antelope bitterbrush (Purshia tridentata), shrub

2. mountain big sagebrush (Artemisia tridentata ssp. vaseyana), shrub

3. Idaho fescue (Festuca idahoensis), grass

Submodel

Description

This state is a product of many years of heavy grazing during time periods harmful to perennial bunchgrasses, changes in the historic fire regime or long-term drought favoring shrub establishment. Grazing tolerant Sandberg bluegrass will increase with a reduction in deep rooted perennial bunchgrass competition and become the dominant grass. Sprouting shrubs begin to dominate the shrub component. Shrub cover exceeds site concept and may be decadent, reflecting stand maturity and lack of seedling establishment due to competition with mature plants. The shrub overstory and Sandberg bluegrass understory dominate site resources such that soil water, nutrient capture, nutrient cycling and soil organic matter are temporally and spatially redistributed (3.1). In both community phases, bare ground may be significant with soil redistribution occurring between interspace and shrub locations. Western juniper increases and may begin to influence the understory vegetation.

Dominant plant species

1. mountain big sagebrush (Artemisia tridentata ssp. vaseyana), shrub

2. antelope bitterbrush (Purshia tridentata), shrub

3. Sandberg bluegrass (Poa secunda), grass

Submodel

Description

This community is characterized by the dominance of annual non-native species such as cheatgrass, north-africa grass, medusahead, and tansy mustard in the understory. Sprouting shrubs may dominate the overstory.

Dominant plant species

1. cheatgrass (Bromus tectorum), grass

2. North Africa grass (Ventenata dubia), grass

3. medusahead (Taeniatherum caput-medusae), grass

Submodel

Description

This state is characterized by a dominance of western juniper in the overstory. Bitterbrush and perennial bunchgrasses may still be present, but they are no longer controlling site resources. Soil moisture, soil nutrients and soil organic matter distribution and cycling have been spatially and temporally altered.

Dominant plant species

1. western juniper (Juniperus occidentalis), tree

Submodel