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 State
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) and needle-and-thread (Hesperostipa comata). Primary forbs would have included various buckwheat species (Eriogonum caespitosum, E. microthecum, E. ovalifolium, E. umbellatum), globemallow (Sphaeralcea spp.), and spiny phlox (Phlox hoodii). 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 higher than the similar, but shallow loamy sites (e.g. 034AY2ppUT Semi-desert Shallow 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 and needle-and-thread, and a scattering of black sagebrush. Primary forbs would have included buckwheats and globemallow. This community would have existed for up to15 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 20 to 30 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 the native perennial forbs and grasses would have returned following at least a 40 year period since the last wildfire.
Pathway CP 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 CP 1.1B
Community 1.1 to 1.3
Community Pathway 1.1B:
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 CP 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 CP 1.2A
Community 1.2 to 1.3
Community Pathway 1.2a
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
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 and needle-and-thread, and a scattering of black sagebrush. Common forb species include buckwheats, globemallow, and prickly phlox. A small component of introduced species will also be present. This community is typically found to occur within the first 15 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 15 to 30 years post wildfire, where yellow rabbitbrush is the currant dominant species, and with 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 CP 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 CP 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 CP 2.2A
Community 2.2 to 2.3
Community Pathway 2.2a:
After approximately 30 years since the last wildfire, a balance between black sagebrush and the native perennial herbs will return.
Pathway CP 2.3A
Community 2.3 to 2.1
Community Pathway 2.3a
Wildfire will 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 3
Dense Black Sagebrush/ Diminished Palatable Understory State
A denser stand of black sagebrush and an understory diminished in palatable herbaceous species (3.1) will be found on sites where continuous season-long grazing by either cattle or big game has taken place. A similar outcome will develop if fire is suppressed. At the higher/moister range of this ESD, juniper (Juniperus osteosperma) and/or pinyon pine (Pinus monophylla in Rich County, Pinus edulis in other parts of this MLRA) may begin to invade the site with continued fire suppression. A return to the Black Sagebrush/ Introduced Non-natives State is possible if the site is grazed during the non-growing season for desirable herbs. Continued heavy livestock and big game use with reduce the resiliency of this State.
Community 3.1
Dense Black Sagebrush/ Diminished Palatable Understory State
Community Phase 3.1: Increased black sagebrush/ Sparse palatable perennial herbs
This plant community is dominated by black sagebrush with few palatable perennial herbs.
State 4
Eroded Black Sagebrush State
Very dense black sagebrush and unpalatable forbs are found on sites where heavy continuous season-long grazing and accelerated soil erosion has occurred. Self-armoring of soils will occur when enough rocks are exposed at the soil surface. This self-armored soil surface helps to maintain this State. Continued heavy grazing will reduce the resiliency of this state. At the higher/moister range of this ESD, juniper and/or pinyon pine may invade the site. Mechanical and chemical treatments are not recommended at these sites because the low responses by native perennial herbs after reseeding make them economically inadvisable.
Community 4.1
Eroded Black Sagebrush State
Community Phase 4.1: dense black sagebrush/ unpalatable perennial herbs
Black sagebrush and unpalatable forbs and grasses will increase following heavy continuous season-long grazing by cattle during the growing season and accelerated soil erosion will occur.
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 Dense Black Sagebrush/ Diminished Palatable Understory State)
Moderate grazing by livestock and/or big game during the growing season of the herbaceous component will cause the herbs to diminish, but not irreversibly if pressure is light and accelerated soil erosion does not take place. Subsequent use by sheep results in further loss of the native forb component. A similar outcome will develop if fire is suppressed.
The approach to this transition is indicated by an increase in black sagebrush and a decrease in the proportion of palatable understory species.
Restoration pathway R3A
State 3 to 2
Restoration Pathway R3a: from State 3 to State 2 (Dense Black Sagebrush/ Diminished Palatable Understory State to Black Sagebrush/ Introduced Non-natives State)
Restoration back to the Black Sagebrush/ Introduced Non-natives State is possible if the site is grazed during the non-growing season for desirable herbs.
Transition T3A
State 3 to 4
Transition T3a: from State 3 to State 4 (Dense Black Sagebrush/ Diminished Palatable Understory State to Eroded Black Sagebrush State)
The Dense Black Sagebrush/ Diminished Palatable Understory State will transition to an Eroded Black Sagebrush State following heavy continuous season-long grazing and accelerated soil erosion. At the higher/moister range of this ESD, juniper and/or pinyon pine may invade the site. The approach to this transition is indicated by evidence of accelerated soil erosion, a decrease in plant cover, and an increase in bare ground and exposed rock. This transition is triggered by accelerated soil erosion.
