Loamy (Ly) Absaroka Lower Foothills

Description

State 1 is named the Bunchgrass/Sagebrush state, in response to the dominance of mid to tall stature cool-season bunchgrasses that are prominant in each community. Rhizomatous wheatgrasses and mid to short stature cool-season bunchgrasses are secondary in these communities. Sagebrush is present on the site, but is not the major cover class.

Characteristics and indicators

Bunchgrass/Sagebrush State (State 1 - Reference) is characterized by the key species including: 15% or less composition by cover of Wyoming big sagebrush, with Bluebunch wheatgrass (<30%), rhizomatous wheatgrasses (Western and Thickspike), Indian ricegrass, and Needleandthread. Minor component to the overall composition is made up of Cusick's bluegrass, Bottlebrush squirreltail, Sandberg bluegrass, Prairie junegrass, and Threadleaf sedge.

Green needlegrass is found in small isolated pockets throughout the land resource unit (LRU), on loamy soils. It is unclear if this is an effect of water catch areas, road drift influence, or management practices. Although intensive inventory data indicates no green needlegrass, it has been identified in ocular estimations, field notes and historic monitoring data collected by the Bureau of Land Management, within this LRU.

Resilience management

This state occurs in areas that are grazed moderately with periods of rest by large ungulates include livestock (cattle and/or sheep) as well as antelope, deer, and elk.

Submodel

Description

Historically within the Big Horn Basin and the surrounding foothills, large landscapes were aerial sprayed for sagebrush control in the 1950’s and 1960's. Multiple large scale wildfires have occurred on the upper fringes of foothills. And in the more recent management strategies, various small scale sagebrush treatment methods have been completed for grazing improvements, large ungulate winter forage improvement projects, and for sage grouse habitat improvement projects. The removal of sagebrush has proven to be long term, with little to no woody vegetation recovery on many locations. This creates State 2, the Perennial Native Grasses State.

Characteristics and indicators

The dominant characteristic for this site is the complete lack of Wyoming big sagebrush, and in some instances all woody shrub cover. Fringed sagewort may be present or in abundance on these sites. Needleandthread and western wheatgrass are dominant with bluebunch wheatgrass, sandberg bluegrass, and threadleaf sedge common.

Resilience management

The scale and variability of sagebrush removal and conditions prior to treatment has led to a variable mixture of communities with one characteristic in common: the lack of sagebrush or other woody shrub structure (1-3 ft in height). Fringed sagewort and other sub-shrubs persist after fire, but do little to maintain or help recover the altered hydrologic function. This state is at-risk of further degradation due to drought, use, and fire.

Submodel

Description

This state, State 3 - Sod-formers, is driven by low-stature sod-forming grasses. Although remnant populations of other desirable native grasses, threadleaf sedge, needleleaf sedge, and small areas of blue grama are the majority of the community composition.

Characteristics and indicators

The dominant sod-forming grass that currently exists within this LRU is threadleaf sedge with a mixture of needleleaf sedge and isolated occurrences of blue grama. Needleleaf sedge will form dense communities, but would not necessarily form a sod like threadleaf sedge.

Resilience management

These species occur naturally (in reference communities) within the ecological site. The general tendency is for these species to increase with prolonged drought or under grazing pressure, becoming dominant. Together as the dominant species, they alter the hydrology of the site by increasing the surface runoff from the dense shallow root system that inhibits the movement of water through or will direct surface flow around the edge of the map concentrating flow into channel like patterns, creating a difficult or hostile environment for native grass species and forbs to persist.

Submodel

Description

Wyoming big sagebrush creates a niche for most herbaceous understory to persist and maintain some vigor in difficult conditions by utilizing the moisture and shelter provided by the canopy as well as protection from grazing. Persistence of drought and/or frequent over use by livestock and/or wildlife leads to a decline of the herbaceous species, creating the Wyoming Big Sagebrush and Bare Ground state. This state can be exacerbated by insects and other human disturbances.

Characteristics and indicators

There is a high level of variability of species in this State, that will shift in response to precipitation or that is in response to past management. Only one well defined community will be provided, with discussion of transitions or variances from this community. The total woody canopy cover does not necessarily always increase with this community, but the percent composition by cover and production is swayed by the decrease of herbaceous vegetation and the relative stability of production by the woody species, creating the appearance of increased canopy by sagebrush.

Resilience management

Risk of wildfire within this state is minimal due to the lack of fine fuels within the understory, but the canopy of the woody vegetation can easily carry a fire under certain climatic conditions. Depending on the prescription of use, trailing and other erosional patterns are highly visible in this state.

Protection from wildfire and use, on a long-term perspective can aid in the transition of a reference community (1.1 or 1.2) to this state as sagebrush becomes dense and decadent reducing the ability for the herbaceous component to maintain vigor; leading to a high rate of bare ground and sagebrush cover. As the herbaceous cover declines and the site continues to weaken, the sagebrush cover is susceptible to attack by insects, disease, and general old age that can remove it from the system creating a system that is at risk of invasion or transition to a more degraded state.

Submodel

Description

State 5, Invaded/Sagebrush State, is successional in nature in response to the introduction and increase of invasive/aggressive weeds. Primarily, cheatgrass is the identified threat to the Absaroka foothills at this time. This state has maintained the native species, but the presence and threat of invasive species has crossed a threshold, affecting the at-risk or management capabilities of the native species that remain.

Characteristics and indicators

This state is characterized by the presence of an invasive/non-native species. Extended periods of drought alone or in combination with misuse, insect damage or wildfire has weakened the native composition of the community opening the canopy for invasion. The competitive nature of annuals and other invasive species, creates a complex environment that inhibits control, and makes it implausible to attain complete eradication once an invasive species has established on the landscape.

Although cheatgrass is the threat most prevalent to rangelands on a large scale, a variety of thistles, knapweeds (namely spotted and Russian), and whitetop (hoary cress) are increasing in density and frequency, producing their own set of challenging management issues. As more species are found within the foothills region or as other species become more prevalent on a large scale, the community dynamics in this state will shift in response to the concerns of the identified species.

Resilience management

Cheatgrass or Downy brome (Bromus tectorum) is the invader that has the greatest concern for most land managers. This invader has an aggressive growth habit that creates a hostile environment for most native species, including sagebrush. Multiple growth cycles throughout a year leaves a thick litter (duff) layer and builds a significant seedbank; and the ability for this annual to persist through the winter under a blanket of snow and sprout early gives it the advantage of all early spring precipitation and snowmelt. Shifts in climatic patterns, changes in management, and exposure to human activity are a few of the explanations for the current flush and rapid expanse across the western United States.

Submodel

Description

The transition of an Invaded/Sagebrush community into the Invaded state, is typically a result of wildfire, a failed controlled burn or other event that removes the sagebrush from the site and allows a readily available seed bank or seed source of the undesirable species to flourish.

Characteristics and indicators

The most common community that is found in the foothills and through the Big Horn Basin and much of the surrounding regions is Cheatgrass. However, there are other threats present, such as knapweeds, thistles, and Whitetop, that can develop into near monoculture stands. The loss of diversity, changes to the potential of a site due to allelopathy or other deterrent characteristics of invasive species, and risks or land use capabilities associated with the various invasive species creates a hostile environment for both native species and grazers.

Resilience management

The resilience and resistance of the invaders create a management road block that is usually financially driven. Many times, once an invasion reaches this point, many land managers have no choice but to learn to utilize what they have rather than to try to treat or improve the site, specifically in relation to cheatgrass control.

Submodel

Description

The arid nature of this region has played a major role in the development and transitions in land use over time. Landscapes accessible by irrigation water and equipment were farmed and many were later abandoned and left to return to rangeland. Other landscapes were treated with a variety of prescriptions to manage or eradicate sagebrush. Tillage of the soil, change in hydrology caused by the loss of vegetative structure, constant climatic fluctuations, and advancements in seed sources have created this altered state.

Resilience management

Once a soil has been disturbed, whether it was mechanical, cultural, or natural the change in soil structure, hydrologic function, and possibly stability prevent a site from supporting the native vegetation or responding to management the same as an undisturbed site. Reclamation or restoration of an area will not replace the original function and factors that made the original location respond as it did. So these "altered" lands may, after significant inputs and time, look similar to the Reference communities (1.1 or 1.2), but they will not be able to respond/function the same as the Reference community.

The Disturbed or degraded state could be drafted as a stand-alone box within the state and transition model diagram. No matter what state a location is classified, once the site has experience an event that has altered the soil properties (erosional, depositional, hydrological or chemical), the site potential is altered. To consider this as an alternate ecological site would not be unreasonable. In some cases (site by site consideration), a re-correlation of a location may be the best solution. But in many cases, the soils have not been altered out of the current site characteristics, but the potential has shifted enough that it is no longer truly comparable to the reference state. The loss of soil structure, degredation of soil biota, loss of argillics or clay illuviation, and minor chemistry changes, alter water and nutrient movement in the soil profile and reduces the water holding capacity. The time required to rebuild structure and have further soil formation, and recovery of biota and vegetation are highly variable depending on the climatic conditions following the event. The initial flush of vegetation is kochia and Russian thistle and mustards. Although they provide organic material, nutrient flow and erosional protection, they lack the structure and root system to fully stabilize the site. The site may become similar in composition to reference, but the integrity of the soil is altered, changing potential of the site. So a dynamic state was captured to detail the altered communities that exist on the landscape.

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