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The simultaneous introduction of exotic species, both plants and animals, and possible extinctions of native flora and fauna, along with climate change |
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Reduction in lengths of time over which livestock grazing takes place |
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Diminishment of heavy growing-season utilization |
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Brush management and prescribed grazing |
State 1 submodel, plant communities
State 2 submodel, plant communities
State 3 submodel, plant communities
State 4 submodel, plant communities
State 5 submodel, plant communities
State 1
Reference
The Reference State is a description of this ecological site immediately prior to Euro-American settlement but long after the arrival of Native Americans. The description of the Reference State was determined by NRCS Soil Survey Type Site Location information and familiarity with rangeland relict areas where they exist. Prior to the coming of European livestock in the 1840s, an Indian ricegrass (Achnatherum hymenoides) and needle and thread (Hesperostipa comata) dominated community (1.1) probably occurred in southern Rich County where sands were blown in from adjacent pluvial plains of Ice Age streams flowing from the western Uinta Mountains. A more complete list of species by lifeform for the Reference State is available in the accompanying tables in the “Plant Community Composition by Weight and Percentage” section of this document.
Community 1.1
Indian ricegrass/ Needle and thread
Community Phase 1.1: Indian ricegrass/ Needle and thread
This plant community would have been characterized by primarily Indian ricegrass and needle and thread bunchgrasses.
State 2
Rubber Rabbitbrush/ Rhizomatous Grasses/ Introduced Non-natives
State 2 is a description of the ecological site shortly following Euro-American settlement, and is considered the current potential for this site. This was once a grassland where native perennial bunchgrasses were nearly grazed out due to the heavy sustained use from trail-connected livestock beginning in the early 1840s. Shrubs and grasses more tolerant of these impacts proliferated. Subsequently rubber rabbitbrush and slender wheatgrass grew to dominate the site, while what native perennial bunchgrasses remained were extremely scarce (2.1). A small component of non-native species, such as cheatgrass (Bromus tectorum) and bulbous bluegrass (Poa bulbosa), have now been introduced to these sites. Continued heavy livestock grazing reduces state resiliency. Alternatively, reducing livestock use will maintain state resiliency.
Community 2.1
Rubber Rabbitbrush/ Increasing Rhizomatous Wheatgrasses/ Native Perennial Bunchgrasses Nearly Absent
Community Phase 2.1: Rubber Rabbitbrush/ Increasing Rhizomatous Wheatgrasses/ Native Perennial Bunchgrasses Nearly Absent
This plant community is dominated rubber rabbitbrush with a slender wheatgrass understory. Indian ricegrass and needle and thread are only a minor component or absent, and a small component of non-native annual grasses may be present.
State 3
Wyoming Big Sagebrush/ Rhizomatous Grass
This is a brush dominated community with an understory of mostly grazing-tolerant rhizomatous grasses such as slender wheatgrass. Continued heavy livestock grazing will reduce state resiliency, while reduction of livestock grazing maintains state resiliency.
Community 3.1
Wyoming Big sagebrush/ Rhizomatous grass understory
Community Phase 3.1: Wyoming Big sagebrush/ Rhizomatous grass understory
This community is characterized by Wyoming big sagebrush with a rhizomatous grass understory, composed primarily of slender wheatgrass.
State 4
Wyoming Big Sagebrush/ Mixed Grass
This state is dominated by Wyoming big sagebrush with mix of caespitose and rhizomatous grasses (e.g. slender wheatgrass, Indian ricegrass, and needle and thread) and less palatable forbs deathcamas (Zigadenus spp.).
Community 4.1
Wyoming Big sagebrush/ Mixed bunch & rhizomatous grass understory
Community Phase 4.1: Wyoming Big sagebrush/ Mixed bunch & rhizomatous grass understory
Wyoming big sagebrush dominated with mix of caespitose and rhizomatous grasses and forbs.
State 5
Re-established Bunchgrass
This re-established bunchgrass-dominated state will have relatively lower species richness and productivity than the grasslands that existed previously on these sites. However, the primary species of Indian ricegrass, needleandthread, and bottlebrush squirreltail will likely be present provided the necessary seed source and no accelerated soil erosion has taken place. Additionally, the inevitable occurrence of a few exotic species and loss of the native perennial forbs will prevent a restoration to pre-settlement conditions. Continued high intensity, short duration grazing rotated between seasons maintains state resiliency of this state. A return to heavy growing season use every year will reduce state resiliency.
Community 5.1
Bunchgrass dominance
Community Phase 5.1: Bunchgrass dominance
This is a return to a proxy of the grassland of the reference state, although it will differ in its species composition, and productivity will be lower because of reduction in soil nutrient pools.
Transition T1A
State 1 to 2
Transition T1a: from State 1 to State 2 (Reference State to Rubber Rabbitbrush/ Rhizomatous Grasses/ Introduced Non-natives State)
The simultaneous introduction of exotic species, both plants and animals, and possible extinctions of native flora and fauna, along with climate change, causes State 1 to transition to State 2. Additionally, these sites were particularly favored by trail-connected livestock from the early 1840s onward. Thus, by the time of the GLO survey and through Stoddart’s (1940) evaluation, much of the native perennial bunchgrasses were lost. Sites were quickly invaded by rubber rabbitbrush (<a class="species-link" href="https://plants.usda.gov/core/profile?symbol=ERNA10" target="_blank" title="Open in plants.usda.gov"><i>Ericameria nauseosa</i></a>) and the more grazing tolerant rhizomatous grasses, such as slender wheatgrass (<a class="species-link" href="https://plants.usda.gov/core/profile?symbol=ELTR7" target="_blank" title="Open in plants.usda.gov"><i>Elymus trachycaulus</i></a>). Reversal of these historic changes (i.e. a return pathway) back to State 1 is not practical.
Transition T2A
State 2 to 3
Transition T2a: from State 2 to State 3 (Rubber Rabbitbrush/ Rhizomatous Grasses/ Introduced Non-natives State to Wyoming Big Sagebrush/ Rhizomatous Grass State)
With further diminishment of grazing pressure and a switch from season-long to high intensity short duration grazing from the 1970s onward, much of the rubber rabbitbrush has been replaced by Wyoming big sagebrush (<a class="species-link" href="https://plants.usda.gov/core/profile?symbol=ARTR2" target="_blank" title="Open in plants.usda.gov"><i>Artemisia tridentata</i></a> ssp. wyomingensis). A key indicator of the approach to this transition is the change in species composition. A reduction in lengths of time over which livestock grazing takes place will trigger the transition.
Transition T3A
State 3 to 4
Transition T3a: from State 3 to State 4 (Wyoming Big Sagebrush/ Rhizomatous Grass State to Wyoming Big Sagebrush/ Mixed Grass State)
With grazing use currently alternating between seasons, and high intensity/ short duration grazing patterns, we can expect some recovery of the bunchgrasses. However, decades of season-long sheep use greatly diminished the native perennial forbs that were previously present. A key indicator of the approach to transition is an increase in bunchgrass cover. A diminishment of heavy growing-season utilization will trigger the transition. Continued heavy growing-season livestock utilization of grasses will reduce state resiliency.
Reduction of growing-season utilization of bunchgrass will maintain state resiliency.
Transition T4A
State 4 to 5
Transition T4a: from State 4 to State 5 (Wyoming Big Sagebrush/ Mixed Grass State to Re-established Bunchgrass State)
With mechanical, chemical, or biological (e.g. sheep use in fall season) shrub control of the sagebrush, followed by grazing deferment during the spring growth period of the bunch grasses, and provided adequate seed source, it might be possible to bring back the bunchgrasses, such as Indian ricegrass and needle and thread, to eventually dominate again. A key indicator of the approach to this transition is a change in species composition. Changes in the intensity and seasons of livestock use will trigger this transition.
