Semidesert Gravelly Loam (Wyoming Big Sagebrush) North

Description

The Reference State includes plant communities dominated by a diverse mixture of perennial grasses, Wyoming big sagebrush, and yellow rabbitbrush. These community phases occur depending on length time since a disturbance (fire, insects, drought, or over browsing) that removes Wyoming big sagebrush from the community. Adequate duration, timing, and intensity of grazing is required to maintain plant vigor and health of the plant community. Plant communities in the Reference State will consist of only native species.

Submodel

Description

The Current Potential State includes plant communities dominated by a diverse mixture of perennial grasses, a mixture of Wyoming big sagebrush, and perennial grasses, and a community dominated by Wyoming big sagebrush. These community phases occur depending on the time since a disturbance that kills Wyoming big sagebrush has occurred, such as fire, insects, or drought, and grazing that provides adequate duration, timing, and intensity that maintain plant vigor and health of the plant community.

Plant communities in this state can include native, acclimatized, naturalized, and invasive non-native species. The Current Potential State is irreversibly changed from the Reference State because the non-native species remain a permanent part of the community.

This plant community has the composition, structure and cover present that facilitates infiltration, nutrients are being cycled through deep rooted perennial grasses, forbs, and evergreen shrubs, and cool season energy capture throughout the entire growing season (March to October, when soil moisture is available) such that this plant community and site resiliency is maintained. With a lengthened fire return interval (greater than 60 years), an increase in sagebrush canopy occurs until sagebrush dominates resource use. This results in a decrease in vigor, cover and reproduction of perennial grasses, and may result in an increase of invasive annuals such as cheatgrass. This leads into transition T2b. With increased sagebrush cover, bare ground increases, infiltration decreases, and a reduction in the amount of nutrient cycling and energy capture.

Submodel

Description

Native shrubs such as Wyoming big sagebrush or rabbitbrush dominate the site. The dominance depends on time since fire. Wyoming big sagebrush is non-sprouting and will be killed by fire. Rabbitbrush can sprout after a fire and can become the dominant shrub. The Native Shrub/Invasive Annual State typically has invasive grasses and/or forbs as the dominant understory species. There may be a few native species remaining, but they do not dominate the plant community. Utah junipers may increase to occupy a significant portion of the over story, if a seed source is present. Wyoming big sagebrush dominates the shrub layer and may be decadent due to age. Bluebunch wheatgrass and other native bunchgrasses are significantly reduced due to increased shrub competition and/or heavy grazing pressure. Invasive annuals such as cheatgrass, annual mustards, and redstem storksbill dominate the understory. The occurrence of fire extends well beyond the normal period for the site.

Submodel

Description

Invasive grasses and forbs dominate the Invasive Annual State. This may occur under a shortened fire return interval which excludes native shrubs by frequent burning or this may occur with repeated improper grazing, or a combination of the two. Bluebunch wheatgrass and other native bunchgrasses are significantly reduced due to increased shrub competition and/or heavy grazing pressure. Only remnant perennial species remain. Highly combustible fine fuels from invasive annuals to dominate the community. Fire is common. Fire frequency is 10 to 30 years.

Submodel

Description

The Seeded Range State is seeded to rangeland species that are composed of mostly introduced species. Unwanted trees and/or shrubs are reduced but they may occupy a portion of the site through natural regeneration. Invasive annual grasses and weedy forb species primarily, cheatgrass and various annual mustards, may be present in the seeding, but do not dominate.

Submodel

Description

The Novel Grassland State is co-dominated by perennial natives Aristida purpurea and Sporobolus cryptandrus, and the non-native annual Bromus tectorum. Aristida purpurea and Sporobolus cryptandrus are warm season bunch grasses that occupy very small components of the historic plant community, but for reasons not yet know, are the dominant perennial grasses in this state.

Submodel