Ecological dynamics
It is impossible to determine in any quantitative detail the historic climax plant community (HCPC) 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 that illustrates 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, tree harvest, 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. At the time of European colonization, what would have been observed on these sites depended on the time since the last wildfire occurred. If the site had not seen fire for about 100 to 120 years, lodgepole pine (Pinus contorta) would have been the dominant species occupying the site with a sparse understory (1.1) due to tree competition, overstory shading, and duff accumulation. Wildfire (1.1a) would have replaced these stands with a rich herb-dominated vegetation. (1.2). In the absence of any major disturbance (1.2a, 1.3a, 1.4a), the vegetation would have progressed into more of a shrub-herb co-dominance (1.3), followed by the establishment of lodgepole pine (1.4), and ultimately to fully mature lodgepole pine forest (1.1). Wildfire (1.1a) would have been the primary disturbance factor prior to Euro-American settlement. Early successional stages were shorter in duration. 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
Reference State
Community Phase 1.1: mature lodgepole pine/ sparse understory
This plant community would have been characterized by a stand of mature lodgepole pine with a sparse understory of pinegrass (Calamagrostis rubescens), nodding bluegrass (Poa reflexa), and Letterman’s needlegrass (Achnatherum lettermanii).
Community Pathway 1.1a:
Wildfire would have removed the trees, allowing shade-intolerant herbs to flourish briefly.
Community Phase 1.2: herb-dominated
An herb-dominated plant community would have developed within the first 5 years following the last fire. Pinegrass, nodding bluegrass, Letterman’s needlegrass, and shade-intolerant forbs would have been the dominant grass species.
Community Pathway 1.2a:
After about 5 years, shrubs would begin to establish in the site.
Community Phase 1.3: shrub-herb co-dominance
Time since last fire would have been approximately 5 to 60 years. An increasing shrub component would have included Woods’ Rose (Rosa woodsii), gooseberry currant (Ribes montigenum), grouse whortleberry (Vaccinium scoparium), and Oregon boxleaf (Paxistima myrsinites), among others.
Community Pathway 1.3a:
About 60 years after fire, lodgepole pine would become established in the site.
Community Phase 1.4: immature lodgepole pine
This phase would have been characterized by a plant community of immature lodgepole pine along with a scattering of sulbapine fir and/or Engelmann spruce (Picea engelmannii). This plant community would occur approximately 60 to 80 years after the last fire.
Community Pathway 1.4a:
About 100 years after fire, lodgepole pine would have become mature and the understory would have become sparse.
Transition T1a: from State 1 to State 2 (Reference State to Secondary Forest/ Introduced State)
Historic change, including the simultaneous introduction of exotic species, both plants and animals, possible extinctions of native flora and fauna, and climate change, has caused State 1 to transition to State 2. Europeans further altered this vegetation largely through tree harvest, livestock grazing, and changing the fire regime. Continued impacts could prevent the recovery toward potential conifer dominance (State 2, various phases). The reversal of these changes (i.e. a return pathway) back to State 1 is not practical.
a. Nature of Forest Community
The overstory tree canopy cover is about 55 to 65 percent. Common understory plants are pinegrass, nodding brome, heartleaf arnica, grouseberry, woods rose, gooseberry current, mountain lover, common juniper, and creeping Oregon grape. Understory composition by air-dry weight is about 60 percent perennial grasses and grasslike plants, 5 percent forbs, and 35 percent shrubs. Understory production ranges from 800 pounds per acre in favorable years to about 400 pounds per acre in unfavorable years. Understory production includes the total annual production of all species within 4 ½ feet of the ground surface.
Table 5. Annual production by plant type
| Plant type |
Low
(lb/acre) |
Representative value
(lb/acre) |
High
(lb/acre) |
| Grass/Grasslike |
240 |
360 |
480 |
| Shrub/Vine |
140 |
210 |
280 |
| Forb |
20 |
30 |
40 |
| Total |
400 |
600 |
800 |
State 2
Secondary Forest/ Introduced State
Community 2.1
Secondary Forest/ Introduced State
State 2 is 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, a different climate, and a secondary stand of trees. State 2 is a description of the ecological site shortly following Euro-American settlement (Alexander 1985, 1988). This state can be regarded as the current potential. With the least amount of disturbance or manipulation of fire regime, a mature stand of lodgepole pine with a sparse understory component is expected at this site (2.1). As with the Reference State, time since last wildfire remains the key factor in determining what vegetation would be encountered here. Wildfire, particularly crown fires, or complete harvesting of the forest (2.1b, 2.5b) will replace these stands with a rich herb-dominated vegetation. (2.2). In the absence of any major disturbance (2.2a, 2.3a, 2.4a), the vegetation will progress into more of a shrub-herb co-dominance (2.3), followed by the establishment of lodgepole pine (1.4), and ultimately to fully mature lodgepole pine forest (1.1). In some areas where wildfire has been prevented, lodgepole pine trees may be over-mature (2.5) and consequently become more susceptible to infestation by insects and other pathogens (2.1a).
Community Phase 2.1: mature lodgepole pine/ sparse understory
This plant community (2.1) is characterized by a stand of mature lodgepole pine with a sparse understory of pinegrass, nodding bluegrass, Letterman’s needlegrass, and shade-tolerant forbs. This stand will develop approximately 100 to 120 years post fire.
Community Pathway 2.1a:
With fire exclusion, and well over 100 years since last fire, a lodgepole pine stand will ultimately deteriorate and will become increasingly susceptible to infestation of insects or other pathogens.
Community Pathway 2.1b:
A stand-replacing wildfire or intensive logging will return the vegetation to an early seral herb-dominated phase. Logging opens up the forest canopy allowing more understory for 20 to 30 years.
Community Pathway 2.1c:
The removal of only the mature lodgepole pine (a selective timer harvest) will allow the immature lodgepole pine to continue growing.
Community Phase 2.2: herb-dominated
This plant community will develop within the first 5 years since the last fire. Dominant grasses are pinegrass, nodding bluegrass, Letterman’s needlegrass, along with shade-intolerant forbs such as subalpine fleabane (Erigeron peregrinus). A small component of introduced species may be present.
Community Pathway 2.2a:
This pathway is characterized by natural succession. The combination of heavy season-long livestock grazing and fire exclusion will accelerate woody plant recovery and diminish the understory.
Community Phase 2.3: shrub-herb co-dominance
A plant community co-dominated by shrubs and herbs will develop approximately 5 to 60 years post-fire. A small component of introduced species may be present.
Community Pathway 2.3a:
This pathway is characterized by natural succession. The combination of heavy season-long livestock grazing and fire exclusion will accelerate woody plant recovery and diminish the understory.
Community Phase 2.4: immature lodgepole pine/ scattered Engelmann spruce
This plant community will develop approximately 60 to 80 years since the last fire.
Community Pathway 2.4a:
This pathway is characterized by natural succession. The combination of heavy season-long livestock grazing and fire exclusion will accelerate woody plant recovery and diminish the understory.
Community Phase 2.5: over-mature blighted lodgepole pine/ understory absent
This plant community is the result of fire exclusion for well over 120 years. The lodgepole pine is over-mature and weakened, making it susceptible to infestation by insects or other pathogens.
Community Pathway 2.5a:
A stand-replacing wildfire or intensive logging will return the vegetation to an early seral herb-dominated phase. Logging opens up the forest canopy allowing more understory for 20 to 30 years.
Transition T2a: from State 2 to State 3 (Secondary Forest/ Introduced State to Tertiary Forest/ Degraded State)
The Secondary Forest/ Introduced State will transition to the Tertiary Forest/ Degraded State following a second cycle of timber harvest or stand replacing wildfire and further impacts from heavy continuous season-long grazing. Logging opens up the forest canopy allowing more understory for 20 to 30 years. Secondary and tertiary disturbances will produce an array of vegetation. Key indicators of the approach to this transition are a reduction in species diversity, gaps in the litter and duff layer, and evidence of accelerated soil erosion. Excessive human utilization triggers this transition. A restoration pathway is possible through moderation of human use, and proactive management.
State 3
Tertiary Forest/ Degraded State
Community 3.1
Tertiary Forest/ Degraded State
State 3 is characterized by tertiary forests that are degraded in both understory and tree condition.
Fire suppression speeds up the dominance by woody plants.
Community Phase 3.1: mature lodgepole pine/ sparse understory
This plant community (3.1) is characterized by a stand of mature lodgepole pine. A sparse understory of pinegrass, nodding bluegrass, Letterman’s needlegrass and shade tolerant forbs may be present. This stand will develop approximately 100 to 120 years post-fire.
Community Pathway 3.1a:
With well over 120 years since the last fire, lodgepole pine will ultimately deteriorate, increasing its susceptibility to infestation by insects or other pathogens.
Community Pathway 3.1b:
A stand-replacing wildfire or intensive logging will return the vegetation to an early seral herb-dominated phase. Logging opens up the forest canopy allowing more understory for 20 to 30 years.
Community Pathway 3.1c:
The removal of only the mature lodgepole pine (a selective timber harvest) will allow the immature lodgepole pine to continue growing.
Community Phase 3.2: herb-dominated
This plant community will develop within the first 5 years since the last fire. Dominant species include pinegrass, nodding bluegrass, Letterman’s needlegrass, and shade intolerant forbs such as subalpine fleabane. A small component of introduced species may be present.
Community Pathway 3.2a:
This pathway is characterized by natural succession.
Community Phase 3.3: shrub-herb co-dominance
A plant community co-dominated by shrubs and herbs will develop approximately 5 to 60 years post-fire. A small component of introduced species may be present.
Community Pathway 3.3a:
This pathway is characterized by natural succession.
Community Phase 3.4: immature lodgepole pine/ scattered Engelmann Spruce
This plant community will develop approximately 60 to 80 years since the last fire, and is characterized by immature lodgepole pine with scattered Engelmann spruce.
Community Pathway 3.4a:
This pathway is characterized by natural succession.
Community Phase 3.5: over-mature blighted lodgepole pine/ understory absent
This plant community is the result of fire exclusion for well over 120 years. The lodgepole pine is over-mature and weakened, increasing its susceptibility to infestation by insects or other pathogens.
Community Pathway 3.5a:
A stand-replacing wildfire will return the vegetation to an early seral shade-intolerant herb-dominated phase.
