Ecological dynamics
It is impossible to determine in any quantitative detail the Reference Plant Community for this ecological site because of the lack of direct historical documentation preceding all human influence. In some areas, the earliest reports of dominant plants include the cadastral survey conducted by the General Land Office, which began in the late 19th century for this area (Galatowitsch 1990). However, up to the 1870s the Shoshone Indians, prevalent in northern Utah and neighboring states, grazed horses and set fires to alter the vegetation for their needs (Parson 1996). In the 1860s, Europeans brought cattle and horses to the area, grazing large numbers of them on unfenced parcels year-long (Parson 1996). Itinerant and local sheep flocks followed, largely replacing cattle as the browse component increased.
Below is a State and Transition Model diagram to illustrate the “phases” (common plant communities), and “states” (aggregations of those plant communities) that can occur on the site. Differences between phases and states depend primarily upon observations of a range of disturbance histories in areas where this ESD is represented. These situations include grazing gradients to water sources, fence-line contrasts, patches with differing dates of fire, herbicide treatment, tillage, etc. Reference State 1 illustrates the common plant communities that probably existed just prior to European settlement.
The major successional pathways within states, (“community pathways”) are indicated by arrows between phases. “Transitions” are indicated by arrows between states. The drivers of these changes are indicated in codes decipherable by referring to the legend at the bottom of the page and by reading the detailed narratives that follow the diagram. The transition between Reference State 1 and State 2 is considered irreversible because of the naturalization of exotic species of both flora and fauna, possible extinction of native species, and climate change. There may have also been accelerated soil erosion.
When available, monitoring data (of various types) were employed to validate more subjective inferences made in this diagram. See the complete files in the office of the State Range Conservationist for more details.
The plant communities shown in this State and Transition Model may not represent every possibility, but are probably the most prevalent and recurring plant communities. As more monitoring data are collected, some phases or states may be revised, removed, and/or new ones may be added. None of these plant communities should necessarily be thought of as “Desired Plant Communities.” According to the USDA NRCS National Range & Pasture Handbook (USDA-NRCS 2003), Desired Plant Communities (DPC’s) will be determined by the decision-makers and will meet minimum quality criteria established by the NRCS. The main purpose for including descriptions of a plant community is to capture the current knowledge at the time of this revision.
State 1
Reference
The Reference State is a description of this ecological site just 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. Before Euro-American settlement, the Reference plant community (1.1) would have been characterized by scattered black sagebrush (Artemisia nova) and abundant perennial herbs. The major grasses would have included Indian ricegrass (Achnatherum hymenoides), needle-and-thread (Hesperostipa comata), bluebunch wheatgrass (Pseudoroegneria spicata), and Western wheatgrass (Pascopyrum smithii). Primary forbs would have included cushion buckwheat (Eriogonum ovalifolium), scarlet globemallow (Sphaeralcea coccinea), longleaf phlox (Phlox longifolia), and several possible species of milkvetch or locoweed (Astraglus spp). 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. The productivity would have been relatively lower than the similar, but stonier loam sites (e.g. R034AY2qqUT Semi-desert Stony Loam Ecological Site) because of the Inverse Texture Principle (Noy-Meir, 1973). In deserts and semi-deserts, finer textured soils are effectively drier and thus typically have lower production potential than coarser textured soils. The phases of this State would have depended on the time since last fire, starting with a perennial herb-dominated phase (1.1) immediately following fire (1.3a, 1.2b), with yellow rabbitbrush (Chrysothamnus viscidiflorus) becoming temporarily dominant (1.2) approximately 5 to 15 years post-fire (1.1a), and finally the re-establishment of black sagebrush (1.3) approximately 20 to 30 years post-fire (1.2a).
Community 1.1
Abundant perennial herbs/ scattered black sagebrush
Community Phase 1.1: abundant perennial herbs/ scattered black sagebrush
This plant community would have been characterized by the temporary dominance of assorted native perennial bunchgrasses, primarily Indian ricegrass, but also including needle-and-thread, bluebunch wheatgrass, and Western wheatgrass, and a scattering of black sagebrush. Primary forbs would have included scarlet globemallow, longleaf phlox, and several species of milkvetch/locoweed. This community would have existed for approximately 1 to 5 years following the most recent fire event.
Community 1.2
Yellow rabbitbrush/ black sagebrush increasing
Community Phase 1.2: yellow rabbitbrush/ black sagebrush increasing
This plant community would have existed approximately 5 to 20 years post-wildfire, and would have had yellow rabbitbrush as the dominant species, and a slight increase in black sagebrush.
Community 1.3
Black sagebrush dominant/ native perennial herbs
Community Phase 1.3: black sagebrush dominant/ native perennial herbs
The balance between black sagebrush, native perennial forbs (primarily locoweeds/milkvetches and longleaf phlox), and grasses would have returned following at least a 40 year period since the last wildfire.
Pathway 1.1A
Community 1.1 to 1.2
Community Pathway 1.1a:
As time increased since the last wildfire, yellow rabbitbrush and black sagebrush would have increased.
Pathway 1.2B
Community 1.2 to 1.1
Community Pathway 1.2b:
Wildfire would have reset the successional clock back to a graminoid dominated site, temporarily removing most of the shrubs.
Pathway 1.2A
Community 1.2 to 1.3
Community Pathway 1.2a:
As length of time increased since the last wildfire, (i.e. greater than 30 years) the balance between black sagebrush and the native perennial understory would have slowly returned.
Pathway 1.3A
Community 1.3 to 1.1
Community Pathway 1.3a
Wildfire would have reset the successional clock back to a graminoid dominated site, removing the majority of the sagebrush and allowing the native perennial bunchgrasses to increase and be temporarily dominant.
State 2
Black Sagebrush/ Introduced Non-natives
State 2 is very similar to State 1 in form and function, with the exception of the presence of non-native plants and animals, possible extinctions of native species, and a different climate. State 2 is a description of the ecological site immediately following Euro-American settlement, and is considered the current potential for this site. The phases of this State vary between a native bunchgrass dominated phase (2.1), to a yellow rabbitbrush/ black sagebrush invaded phase (2.2), to a black sagebrush with native perennial understory phase (2.3), which develop according to the time since last wildfire (2.3a or 2.2b, 2.1a, 2.2a, respectively). The resiliency of this state is maintained by the availability of native seed sources for both the herbaceous species and for black sagebrush, and by wildfire. The resiliency of this State can be negatively impacted by heavy livestock and big game grazing.
Community 2.1
Black Sagebrush/ Introduced Non-natives State
Community Phase 2.1: abundant perennial herbs/ scattered black sagebrush
This plant community is characterized by the temporary dominance of assorted native perennial bunchgrasses, primarily Indian ricegrass, along with needle-and-thread, and a scattering of black sagebrush. Common forb species include locoweeds/milkvetches, longleaf phlox, and scarlet globemallow. A small component of introduced species will also be present. This community is typically found to occur within the first 1 to 5 years following wildfire.
Community 2.2
Yellow rabbitbrush/ black sagebrush increasing
Community Phase 2.2: yellow rabbitbrush/ black sagebrush increasing
This plant community is typical approximately 20 to 30 years post-wildfire, where yellow rabbitbrush will be the currant dominant species, and a slight increase in black sagebrush.
Community 2.3
Black sagebrush dominant/ native perennial herbs
Community Phase 2.3: black sagebrush dominant/ native perennial herbs
The balance between black sagebrush and the native perennial herbs will return following at least a 30 year period since the last wildfire. A small component of introduced species will also be present.
Pathway 2.1A
Community 2.1 to 2.2
Community Pathway 2.1a:
As time increases since the last wildfire, yellow rabbitbrush and black sagebrush will increase.
Pathway 2.2B
Community 2.2 to 2.1
Community Pathway 2.2b:
Wildfire will reset the successional clock back to a graminoid dominated site, temporarily removing most of shrubs.
Pathway 2.2A
Community 2.2 to 2.3
Community Pathway 2.2a:
After approximately 20 to 30 years since the last wildfire, a balance between black sagebrush and the native perennial herbs will return.
Pathway 2.3A
Community 2.3 to 2.1
Community Pathway 2.3a
Wildfire will reset the successional clock back to a graminoid dominated phase, removing the majority of the sagebrush and allowing the native perennial bunchgrass to increase and be temporarily dominant.
State 3
Moderately Grazed Remnants
A prolonged absence of fire and continuous heavy grazing during the growing season will moderately reduce the perennial herbaceous understory, allowing black sagebrush to increase (3.1). Employing more conservative grazing practices by avoiding the growing season of the herbaceous component (R3a), may help to restore this plant community back the Black Sagebrush/ Introduced Non-natives State. Increases in grazing, especially during the spring growth period, will reduce the resiliency of this State.
Community 3.1
Moderately Grazed Remnants State
Community Phase 3.1: increased black sagebrush/ sparse perennial herbs
This plant community will have a greater abundance of black sagebrush with a sparse understory of perennial herbs.
State 4
Dense Black Sagebrush/ Unpalatable Forbs
Black sagebrush and unpalatable forbs such as granite prickly phlox (Linanthus pungens) and/or poisonous locoweed/milkvetch species (4.1) will increase on sites where heavy continuous season-long grazing has taken place. The resiliency of this State can be maintained through a reduction in livestock grazing; increases in livestock grazing will reduce the resiliency of this State. Mechanical and chemical treatments are not recommended at these sites because the low responses by native perennial herbs after reseeding make them economically inadvisable. Additionally, these soils are too shallow for successful conversion to crested wheatgrass.
Community 4.1
Dense black sagebrush/ unpalatable perennial herbs
Community Phase 4.1: dense black sagebrush/ unpalatable perennial herbs
Black sagebrush and unpalatable forbs will increase following heavy continuous season-long grazing by cattle during the growing season.
Transition T1A
State 1 to 2
Transition T1a: from State 1 to State 2 (Reference State to Black Sagebrush/ 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, have caused State 1 to transition to State 2. Reversal of such 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 (Black Sagebrush/ Introduced Non-natives State to Moderately Grazed Remnants State)
The Black Sagebrush/ Introduced Non-natives State will transition to the Moderately Grazed Remnants State when fire return intervals are 3 to 4 decades long and/or when continuous spring grazing is allowed. This will result in black sagebrush beginning to dominate the site at the expense of the associated perennial herbs. The approach of this transition is indicated by an increase in black sagebrush and native perennial forbs.
Restoration pathway R3A
State 3 to 2
Restoration Pathway R3a: from State 3 to State 2 (Moderately Grazed Remnants State to Black Sagebrush/ Introduced Non-natives State)
Restoration back to the Black Sagebrush/ Introduced Non-natives State is possible when more conservative grazing practices are used such as by avoiding the growing season of the understory component.
Transition T3A
State 3 to 4
Transition T3a: from State 3 to State 4 (Moderately Grazed Remnants State to Dense Black Sagebrush/ Unpalatable Forbs State)
The Moderately Grazed Remnants State will transition to the Dense Black Sagebrush/ Unpalatable Forbs State following heavy continuous season-long grazing. This transition is indicated by increases in size, density, and cover of black sagebrush, and an increase in the proportion of unpalatable forbs. Heavy livestock grazing, especially during the spring growth period, will trigger this transition.
