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 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, and kinds and times of timber 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.
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 relict areas where they exist. At the time of European colonization, what would have been observed on these sites would have primarily depended on the time since the last wildfire occurred. If fire had not occurred for about 100 years, a stand of mixed conifers including subalpine fir (Abies lasiocarpa), Douglas-fir (Pseudotsuga menziesii), and white fir (Abies concolor) would have been the dominant species occupying the site (1.1). The particular tree dominants would also sort out based on aspect exposure (Alexander 1985, 1988). The understory would have been relatively sparse under mature trees due to tree competition, overstory shading, and duff accumulation. Wildfire or insect outbreaks on particular tree species (1.1a) would have replaced these stands with a rich diversity of herb-dominated vegetation (1.2). In the absence of any major disturbance (1.2a, 1.3a, 1.4a, 1.5a), the vegetation would have progressed into more of a shrub-herb co-dominance (1.3), followed by the increasing presence of aspen (Populus tremuloides) first as seedlings and saplings (1.4), and later as mature aspen with mixed conifer seedlings (1.5). Ultimately the conifers would have outcompeted aspen, returning the climax vegetation (1.1). Wildfire (1.1a, 1.5b) would have been the primary disturbance factor prior to colonization, although periodic outbreaks of insects destroying particular tree species could reset the successional clock. 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 subalpine fir/ white fir/ Douglas-fir/ sparse understory
This plant community (1.1) would have been characterized by a stand of mature mixed conifers including subalpine fir, Douglas-fir, and white fir, with a sparse understory of Geyer’s sedge (Carex geyeri), slender wheatgrass (Elymus trachycaulus), and heartleaf arnica (Arnica cordifolia).
Community Pathway 1.1a:
Wildfire would have removed the trees, allowing shade-intolerant herbs to flourish briefly.
Community Phase 1.2: herb-dominated
This plant community would have developed within the first 5 years following fire.
Geyer’s sedge, slender wheatgrass, and heartleaf arnica would have been the dominant species, along with many other short-lived herbaceous shade-intolerant 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
Between 5 and 60 years after fire, shrubs and herbs would co-dominate the site. The increasing shrub component would have included mountain snowberry (Symphoricarpos oreophilus), creeping barberry (Mahonia repens), mallow ninebark (Physocarpus malvaceus), and gooseberry currant (Ribes montigenum), among others.
Community Pathway 1.3a:
About 60 years after fire, aspen would have become established in the site.
Community Phase 1.4: immature aspen
This plant community would have been dominated by a stand of immature aspen, a seral species, while the conifer species would have begun to establish themselves under other nurse plants. A stand of immature aspen would have existed approximately 60 to 80 years following the last fire.
Community Pathway 1.4a:
Aspen would have continued to mature while the various conifers would have become well established in the understory.
Community Phase 1.5: mature aspen/ mixed conifer
A stand of mature aspen intermixed with mixed conifers and various understory shrubs would have been encountered approximately 80 to 100 years post fire.
Community Pathway 1.5a:
After about 100 years following the last fire, the conifers would become mature, shading out aspen and the shade-intolerant shrub and herb species in the understory.
Community Pathway 1.5b:
Wildfire would have removed the trees, allowing shade-intolerant herbs to flourish briefly.
Transition T1a: from State 1 to State 2 (Reference State to Secondary Forest/ Introduced State)
The simultaneous introduction of exotic species, both plants and animals, and possible extinctions of native flora and fauna, along with climate change, has caused State 1 to transition to State 2. Europeans further altered this vegetation largely through logging, livestock grazing, trapping of beaver, 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 impractical.
a. Nature of Forest Community
The overstory tree canopy cover is about 40 percent. Common understory plants are Geyer sedge, slender wheatgrass, heartleaf arnica, mountain snowberry, and creeping Oregon grape. Understory composition by air-dry weight is about 45 percent perennial grasses and grasslike plants, 20 percent forbs, and 35 percent shrubs. Understory production ranges from 500 pounds per acre in favorable years to about 100 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 |
45 |
135 |
225 |
| Shrub/Vine |
35 |
105 |
175 |
| Forb |
20 |
60 |
100 |
| Total |
100 |
300 |
500 |
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 following Euro-American settlement. This state can be regarded as the current potential. With the least amount of disturbance or manipulation of the fire regime, a mature stand of subalpine fir, white fir, and Douglas fir 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 will be encountered on these sites. Wildfire, particularly crown fires, or complete harvesting of the forest (2.1b, 2.5b, 2.6a) will replace these stands with a rich diversity of herb-dominated vegetation. (2.2). In the absence of any major disturbance (2.2a, 2.3a, 2.4a, 2.5a), the vegetation will progress into more of a shrub-herb co-dominance (2.3), followed by the increasing presence of aspen, first as seedlings and saplings (2.4), and later as mature aspen with immature conifers (2.5). Ultimately the conifers will outcompete aspen, returning to a semblance of climax vegetation (2.1). In some areas where wildfire has been prevented, the conifers may become over-mature (2.6) and consequently are more susceptible to infestation by insects and pathogens (2.1a). The resiliency of this State can be maintained by moderating human uses of the forest for timber and/or grazing.
Community Phase 2.1: Mature Douglas-fir/ Sparse understory
This plant community (2.1) is characterized by a stand of mature subalpine fir, white fir, and Douglas-fir. A sparse understory of Geyer’s sedge, slender wheatgrass, and heartleaf arnica may be present.
Community Pathway 2.1a:
With fire exclusion, or well over 100 years since last fire, the conifer stand will ultimately deteriorate (become over-mature) and become increasingly susceptible to infestation by insects or other pathogens.
Community Pathway 2.1b:
A stand-replacing wildfire or intensive logging will set the vegetation back to an early seral herb-dominated phase. Logging opens up the forest canopy, allowing shade-intolerant understory herbs and shrubs to flourish for 20 to 30 years.
Community Pathway 2.1c:
The removal of only the mature Douglas-fir will leave only the less desirable true fir species in the overstory.
Community Phase 2.2: herb-dominated
This plant community will develop within the first 5 years following the last fire or complete tree removal. Geyer’s sedge, slender wheatgrass, and heartleaf arnica will be the dominant understory species. A small component of introduced species may be present.
Community Pathway 2.2a:
The combination of heavy season long livestock grazing and fire exclusion will accelerate woody plant (shrub) establishment and diminish the herbaceous 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 following fire or complete tree removal. A small component of introduced species may be present.
Community Pathway 2.3a:
The combination of heavy season long livestock grazing and fire exclusion will accelerate woody plant establishment and diminish the herbaceous understory.
Community Phase 2.4: immature aspen
Aspen will establish in the site 60 to 80 years after the last fire or complete tree removal.
Community Pathway 2.4a:
The combination of heavy season long livestock grazing and fire exclusion will accelerate woody plant establishment and diminish the understory.
Community Phase 2.5: mature aspen/ mixed conifer
A stand of mature aspen with an intermixed with subalpine fir, white fir, and Douglas-fir will develop approximately 80 to 100 years following fire or complete tree removal.
Community Pathway 2.5a:
The combination of heavy season long livestock grazing and fire exclusion will accelerate woody plant establishment and diminish the understory.
Community Pathway 2.5b:
A stand-replacing wildfire or intensive logging will set the vegetation back to an early seral herb-dominated phase. Logging opens up the forest canopy allowing grasses, herbs, and shrubs to flourish for 20 to 30 years.
Community Pathway 2.5c:
The removal of mature aspen will leave a stand of immature aspen, possibly with a few subalpine fir, white fir, and Douglas-fir in the understory.
Community Phase 2.6: over-mature, blighted mixed conifers/ understory absent
This plant community is the result of fire exclusion for well over 100 years. The Douglas-fir is over-mature and weakened, making it susceptible to infestation by insects or other pathogens.
Community Pathway 2.6a:
A stand-replacing wildfire will set the vegetation back to an early seral herb-dominated phase.
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 a stand replacing wildfire and further impacts from heavy continuous season-long grazing. Logging opens up the forest canopy allowing shade-intolerant species to flourish for 20 to 30 years. Secondary and tertiary disturbances can produce an array of vegetation from degraded temporary meadows to further simplified forests. The approach to this transition is indicated by a loss of species diversity, discontinuous litter and duff coverage, and evidence of accelerated soil erosion. This transition is triggered by excessive human utilization of the most economically desirable parts of the vegetation.
State 3
Tertiary Forest/ Degraded State
Community 3.1
Tertiary Forest/ Degraded State
State 3 is characterized by tertiary forests in which both the understory vegetation and tree condition have been degraded. Fire suppression accelerates the development of woody plant dominance.
Community Phase 3.1: mature subalpine fir/ white fir/ Douglas-fir/ sparse understory
This plant community (3.1) is characterized by a mixed stand of mature subalpine fir, white fir, and Douglas-fir. A sparse understory of Geyer’s sedge, and slender wheatgrass, heartleaf arnica, and other shade-tolerant plants may be present.
Community Pathway 3.1a:
With fire exclusion, or well over 100 years since last fire, subalpine fir, white fir, and Douglas-fir will ultimately age, lose vigor, and become increasingly susceptible to infestation by insects or other pathogens.
Community Pathway 3.1b:
A stand-replacing wildfire or intensive logging will set the vegetation back to an early seral herb-dominated phase. Logging opens up the forest canopy, allowing shade-intolerant grasses, forbs, and shrubs to flourish for 20 to 30 years.
Community Pathway 3.1c:
The removal of only the mature Douglas-fir will leave only the less desirable true fir species in the overstory.
Community Phase 3.2: herb-dominated
This plant community will develop within the first 5 years following the last fire or complete tree removal. Dominant grasses are Geyer’s sedge and slender wheatgrass. A small component of introduced species may be present.
Community Pathway 3.2a:
After about 5 years, shrubs will begin to establish in the site.
Community Phase 3.3: shrub-herb co-dominance
A plant community co-dominated by shrubs and herbs will develop approximately 5 to 60 years after fire or complete tree removal. A small component of introduced species may be present.
Community Pathway 3.3a:
Aspen will become established at the site after 60to 80 years following the last wildfire or complete tree removal.
Community Phase 3.4: immature aspen
Immature aspen dominate the stand 60 to 80 years following the last fire or complete tree removal.
Community Pathway 3.4a:
Aspen matures and immature conifers become well established in the understory 80 years after the last fire or complete tree removal.
Community Phase 3.5: mature aspen/ Douglas-fir
A stand of mature aspen intermixed with subalpine fir, white fir, and Douglas-fir will develop approximately 80 to 100 years following fire.
Community Pathway 3.5a:
After about 100 years following the last fire, subalpine fir, white fir, and Douglas-fir will become mature, shading out aspen and the shade-intolerant shrub and herb species in the understory.
Community Pathway 3.5b:
A stand-replacing wildfire or intensive logging will set the vegetation back to an early seral herb-dominated phase. Logging opens up the forest canopy allowing grasses, herbs, and shrubs to dominate for 20 to 30 years.
Community Pathway 3.5c:
The removal of mature aspen will leave a stand of immature aspen, possibly with a few subalpine fir, white fir, and Douglas-fir in the understory.
Community Phase 3.6: over-mature, blighted mixed conifers/ understory sparse
This plant community is the result of fire exclusion well over 100 years. The conifers are over-mature and weakened, making them more susceptible to infestation by insects or other pathogens.
Community Pathway 3.6a:
A stand-replacing wildfire will set the vegetation back to an early seral herb-dominated phase.
