State 1
Reference

Community 1.1
Mature forest

Figure 7. Community Phase 1.1

The historic most successionally advanced community phase was presumed to be open old-growth stands of predominantly Sierra lodgepole pine occasional scattered white fir, Jeffrey pine and incense cedar, with establishment of secondary conifers limited by frost and high water table levels. The age for this community is estimated to have ranged from 100 to more than 200 years between disturbances. Stand-replacing fires would have initially established an even-aged forest. However, minor disturbances, such as windfall and insect infestation would have eventually led to openings, tree regeneration, and a mosaic of developing small stands forming an overall multi-aged forest. The understory cover was probably moderate in the openings with Lemmon’s willow, grasses, and sedges making up the majority of species.

Forest overstory.The overstory in this multi-aged forest is open, rarely exceeding 65 percent canopy cover. Mature Sierra lodgepole pine dominates with a cover ranging from 35 to 65 percent, with an average of 45 percent. White fir, Jeffrey pine, and incense cedar are occasionally present with low cover.

Forest understory. The understory of these sites consists of primarily grasses and willows and species composition is variable. The open canopy allows a high diversity of herbaceous species and graminoids.

Community 1.2
Stand initiation

This community may be dominated for a short time by Lemmon’s willow, grasses and forbs. Lemmon’s willow can resprout from the rootcrown or stembase after a fire. Several species of grasses and forbs, including bentgrasses and bromes, may regenerate from seed. Willow and grasses can have a potentially high cover. Remnant overstory lodgepole pines may be present in limited numbers.

Sierra lodgepole pine will regenerate from wind dispersed seed. The seeds will readily germinate in the spring in the mineral soil exposed by fire or scarification but require moist soil and full sun to establish in the first season. The seedlings develop into pole sized trees, with up to 40 percent canopy cover.

Forest overstory.If there is ample moisture and sunlight, Sierra lodgepole pine seedlings will germinate in thick patches in the spring following a fire or clear-cut.

Forest understory. Native grases and lemmon's willow can have high cover in this area.

Community 1.3
Young forest

This phase is dominated by an overstory of young Sierra lodgepole pine forest. White fir may germinate during this time in the shade of the young lodgepole pine and small shrubs. The estimated duration for this phase is up to approximately 60 years. Canopy increases with age and growth slows near the upper age of the phase.

Community 1.4
Dense young forest

The dense phase of the young forest develops in the absence of canopy disturbance. Periods without fire, windthrow, or pest ourbreaks maintain a closed overstory canopy. White fir and incense cedar seedlings are more shade tolerant than lodgepole pine seedlings, which allows them to continue to reproduce in the understory of the lodgepole pine canopy. The density of white fir increases over time and creates competition with lodgepole pine for sunlight and water. This stress makes the forest more susceptible to death from pests and drought, which in turn increases the fuel loads and potential for severe fires.

It appears that this site is not a conducive environment for the optimal growth of white fir. This is primarily due to the properties of the soil, the high water table, and the high frequency of frost. However, in some areas within this site, white fir is present and reproducing well.

Community 1.5
Dense mature forest

The mature dense forest will develop with the continued exclusion of fire, allowing white fir to reach the upper canopy and gain dominance over lodgepole pine. Competition for water and sunlight will cause the health and vigor of Sierra lodgepole pine to decline. An estimated age for this community phase ranges from 60 to more than 200 years. However, drought, pest attacks and water table fluctuations are disturbances likely to decimate this phase.

Community 1.6
Mountain pine beetle epidemic

Standing dead Sierra lodgepole pine forests can result following disease or pest outbreaks, sometimes in combination with prolonged drought or flooding. Large patches of forest remain standing dead for many years until fire or manual treatment remove the dead trees and surface fuels. If surface fuels are not too high, grasses and forbs may grow in the understory and in openings.

Pathway 1.1a
Community 1.1 to 1.2

In the event of a severe canopy fire, or a clear-cut with or without a prescribed burn, phase 1.1 would quickly develop into phase 1.2, the stand initiation phase. Sierra lodgepole pine is susceptible to death from fire at any age because of their thin bark and shallow root systems (Kocher, 2005).

Pathway 1.1c
Community 1.1 to 1.4

This pathway occurs with fire suppression.

Pathway 1.1b
Community 1.1 to 1.5

Plant community phase 1.1 may develop into phase 1.6 with the infestation of pests. The primary threat to Sierra lodgepole pines from pest invasion is from the mountain pine beetle (Dendroctonus ponderosae). Infestations can lead to a high mortality rate, sometimes leaving a stand of dead trees, and causing high fuel loads. Natural outbreaks of variable severity tend to occur every 20 to 40 years (Cope, 1993).

Pathway 1.2a
Community 1.2 to 1.3

Phase 1.2 will naturally move to phase 1.3 if given time without major disturbances. This pathway is facilitated with a natural fire regime and small scale canopy disturbances. An open multi-age forest develops (Community Phase 1.3). Reports vary on the natural fire return interval, but this pathway assumes that surface fires are relatively frequent with 20 to 40-year cycles (Cope 1993). Manual thinning with prescribed burns can imitate the natural cycle and lead to the same relatively open community.

Pathway 1.2b
Community 1.2 to 1.4

This pathway occurs with fire suppression that prevents thinning necessary for the natural patchy structure of this ecological site. Lack of ground fire allows white fir and incense cedar to establish and gain maturity in the understory.

Pathway 1.3a
Community 1.3 to 1.1

The natural shift for this phase is to grow and develop into community phase 1.1. This pathway evolved with a historic fire regime of occasional surface and moderately severe fires, with occasional pest outbreaks that can lead to partial tree death. Manual thinning or prescribed burning can be implemented to replace the natural disturbances that kept this forest relatively open.

Pathway 1.3b
Community 1.3 to 1.2

In the event of a canopy fire, this phase would quickly return to phase 1.2

Pathway 1.3c
Community 1.3 to 1.4

This pathway occurs with fire suppression that prevents thinning necessary for the natural patchy structure of this ecological site. Lack of ground fire allows white fir and incense cedar to continue to establish and gain maturity in the understory.

Pathway 1.3d
Community 1.3 to 1.6

This phase can transition to phase 1.6 with the infestation of pests. The primary threat to Sierra lodgepole pines from pest invasion is from the mountain pine beetle (Dendroctonus ponderosae). Infestations can lead to a high mortality rate, leaving a forest of standing dead trees, and causing high fuel loads. Natural outbreaks of variable severity tend to occur every 20 to 40 years (Cope, 1993).

Pathway 1.4c
Community 1.4 to 1.2

In the event of a severe canopy fire or clear-cut/scarification, phase 1.2 would develop.

Pathway 1.4a
Community 1.4 to 1.5

With continued fire suppression, this phase will transition to a dense mature forest.

Pathway 1.4b
Community 1.4 to 1.6

This phase can transition to phase 1.6 with the infestation of pests. The primary threat to Sierra lodgepole pines from pest invasion is from the mountain pine beetle (Dendroctonus ponderosae). Infestations can lead to a high mortality rate; leaving a forest of standing dead trees, and causing high fuel loads. Natural outbreaks of variable severity tend to occur every 20 to 40 years (Cope, 1993).

Pathway 1.5c
Community 1.5 to 1.1

A naturally occurring moderate or surface fire in this forest is unlikely due to the high fuel load. Considerable management effort would be needed to create the open forest conditions that should exist in this forest with a natural fire regime. Manual treatment or prescribed burns could thin out dense Sierra lodgepole pine, white fir and incense cedar. This would shift this forest back to its natural state of open, patchily distributed Sierra lodgepole pine forest (Community phase 1.1).

Pathway 1.5a
Community 1.5 to 1.2

Ladder fuels and the density of fuels formed from the dead and dying white fir in the mid and lower canopies create conditions suitable for a high intensity canopy fire, which would initiate regeneration similar to that seen in phase 1.2. Because of the likely proximity of a white fir seed source, further treatments would be needed to promote the predominance and reestablishment of Sierra lodgepole pines.

Pathway 1.5b
Community 1.5 to 1.6

A high mortality pest attack on white fir and lodgepole pine, drought or above normal water tables could create a dead and dying forest with conditions and fuel loadings similar or heavier than phase 1.6.

Pathway 1.6a
Community 1.6 to 1.2

After a prolonged period, this phase will progress to phase 1.2. Severe fire will accelerate this succession. Fire is the natural disturbance at this point in the Sierra lodgepole pine cycle and will allow for the regeneration of the open lodgepole pine forest seen in phase 1.3. Mechanical removal of the dead trees with partial scarification of the surface or a prescribed burn in the understory can also induce stand regeneration.