State 1
Reference

Community 1.1
Old-growth forest

This community phase represents the most successionally advanced community for this ecological site and is characterized by an open forest of Jeffrey pine. White fir and incense cedar are common associates, with a moderate cover of shrubs and forbs in the understory. The forest canopy cover is less than 60 percent and shrubs cover is approximately 30 percent. The most common shrubs are greenleaf manzanita, prostrate ceanothus, and antelope bitterbrush. Common grasses and forbs likely included lupine (Lupinus spp.), buckwheat (Eriogonum spp.) and phlox (Beardsley et al. 1999). This community phase is maintained by low and moderate intensity fires that remove fire intolerant seedlings and saplings from the understory. Moderate intensity fires kill some of the overstory trees, leaving canopy openings that are favorable for Jeffrey pine regeneration. Moderate intensity fires break the uniformity of older forest stands with pockets of intermixed younger forests. Because the reference phase was largely either clear-cut during the Comstock era or impacted by fire suppression, plot data representing this phase are not available.

Community 1.2
Stand initiation

This shrubland community phase thrives in openings created by large high-severity fire that burns the forest canopy and kills the majority of overstory trees, or when canopy trees are removed by clear-cutting. Remnant overstory trees that escaped fire or logging may be present in limited numbers. Fire dependent shrubs such as greenleaf manzanita, huckleberry oak, mountain whitethorn, and prostrate ceanothus resprout and germinate from seed vigorously after a fire. Greenleaf manzanita vigorously resprouts from underground lignotubers, and regenerates from heat scarified seeds that may survive in the soil for more than 400 years (Nagal and Taylor 2005, Hauser 2007). Huckleberry oak is a fire-adapted species that is highly flammable and vigorously resprouts from the root crown after fire (Howard 1992, Nagal and Taylor 2005, Odion et al. 2009). Mountain whitethorn is an obligate resprouter after low to medium intensity fire, and seeds require heat for germination (Reeves 2006). Prostrate ceanothus recruits from long-lived seed that is stimulated by fire, and forms large mats that stabilize soils and fix nitrogen, enhancing soils for colonization by other species (Skau et al. 1970, Brown et al. 1971). With rapid regeneration of fire-adapted shrubs, shrubs may dominate in 7 to 9 years (Risser and Fry 1988). Scattered Jeffrey pine and white fir seedlings sprout but may take 50 to 60 years to dominate over the shrubland community phase (Smith 1994, Azuma et al. 2004). Perennial bunchgrasses and some forbs cover small portions of the area.

The size and the intensity of a burn may influence the shrub expression. Shrubs have been associated with large burn size, whereas trees were not able to establish across the landscape (Royce and Barbour 2001). The intensity of burn may affect the scarification of seeds. Shrubs can prevail in areas prone to frequent fire, such as ridges and wind tunnels. Greenleaf manzanita is a strong competitor for water. It continues to deplete water after conifer species have gone dormant for the drought season. This competition for water and sunlight between the shrubs and conifer seedlings can delay the establishment of a forest (Royce and Barbour 2001).

Surviving overstory trees are a valuable source of seed for tree regeneration. Seeds are dispersed downwind at approximately twice the height of the source tree, possibly farther under windy conditions. Jeffrey pine seed is also cached by squirrels and chipmunks, which aid in dispersing the seed. Studies have shown that Jeffrey pine seed germination and seedling survival is greater for cached seeds that have been buried in soil rather than for wind blown seeds deposited on the surface. Jeffrey pine seedlings prefer open sunlight and bare soil for germination and development. While white fir may be present at this time, however it is more likely to come in later under the shade of Jeffrey pine. Jeffery pine and white fir seedlings may take 50 to 60 years to dominate over the shrubland community (Azuma et al. 2004, Smith 1994). The shrub community can be perpetuated by frequent fire or other disturbances such as grazing, human intervention, or heavy foot traffic.

Forest overstory.Scattered remnants of overstory Jeffrey pine and white fir may be present.

Forest understory. Greenleaf manzanita (Arctostaphylos patula), mountain whitethorn (Ceanothus cordulatus) and huckleberry oak (Quercus vacciniifolia) have high cover after a fire or manual treatment projects.

Community 1.3
Young forest

Figure 7. Community Phase 1.3

This community phase is currently the most common expression of this ecological site. It is a heavily managed forest with manual thinning and prescribed burns helping to remove the white fir component and maintain the dominance of Jeffrey pine. The removal of the understory creates a more open forest with less competition between trees. The manual thinning and prescribed burns can replace and emulate the natural fire regime.

Forest overstory.Jeffrey pine is dominant in the overstory with a range in cover from 35 to 80 percent, with an average of 65 percent. White fir is often found in small percentages in the understory and mid-canopy. White fir does not seem to prefer this zone; the soils may be too droughty. Lodgepole pine (Pinus contorta ssp. murrayana) is also found in positions of greater available soil moisture (duration, frequency or amount of soil moisture).

Forest understory. The understory cover and diversity increases as the overstory canopy decreases. Mountain whitethorn, prostrate ceanothus, and greenleaf manzanita are common shrubs that average 10 percent combined cover. Herbaceous cover is low, averaging 3 percent. Pinewoods lousewort (Pedicularis semibarbata), milk kelloggia (Kelloggia galioides), and lettuce wirelettuce (Stephanomeria lactucina) are often present. Squirreltail (Elymus elymoides) and western needlegrass (Achnatherum occidentale) are common graminoids but of limited extent.

Community 1.4
Young forest infilling

This community phase is defined by a dense multiple-layer canopy and high basal area of predominantly white fir. Canopy cover ranges from 60 to 90 percent. The trees are often overcrowded and stressed due to the competition for water and nutrients, which makes them more susceptible to death from pests and drought. Fire hazard is high in this community due to the deep accumulation of litter, the standing dead and down trees, and dense multi-layered structure of the forest (which creates ladder-fuels).

Forest overstory.White fir dominates this forest with a dense canopy and multiple tree layers. Jeffrey pine is a common associate, while Sierra lodgepole pine and incense cedar are occasionally present with low cover.

Forest understory. The understory is barren under the dense canopy of white fir. However, shade-tolerant white fir and incense cedar are present as regeneration.

Community 1.5
Old-growth forest infilling

Figure 8. Community Phase 1.5

This community phase is defined by a dense multiple-layer canopy and high basal area of older white fir. Canopy cover ranges from 60 to 90 percent. The trees are overcrowded and often diseased and stressed due to the competition for water and nutrients. Fire hazard is high in this community due to the deep accumulation of litter, the standing dead and down trees, and dense multi-layered structure of the forest.

Forest overstory.White fir dominates this forest with a dense canopy and multiple tree layers. Jeffrey pine is a common associate, while lodgepole pine and incense cedar are occasionally present with low cover.

Forest understory. The understory is sparse under the dense canopy of white fir. However, shade-tolerant white fir and incense cedar seedlings and saplings are present.

Pathway 1.1a
Community 1.1 to 1.2

In the event of a severe canopy fire, or a clear-cut and a prescribed burn this community phase would move to the stand initiation phase,1.2.

Pathway 1.1b
Community 1.1 to 1.5

If fire is excluded from the old growth community phase, tree density will continue to increase, shifting this community towards the closed white fir-mixed conifer community phase 1.5.

Pathway 1.2a
Community 1.2 to 1.3

The natural pathway is to community phase 1.3. This pathway is maintained with a natural fire regime. Reports vary on the natural fire return interval, but this pathway assumes that surface fires were relatively frequent from 5 to 18 years. Manual thinning with prescribed burns can emulate the natural cycle and lead to the same open community phase.

Pathway 1.2b
Community 1.2 to 1.4

An alternate pathway is created when fire is excluded from the system, and leads to forest infilling, community phase 1.4.

Pathway 1.3a
Community 1.3 to 1.1

This is the natural pathway for this community phase, which evolved with a historic fire regime of relatively frequent surface and moderate severity fires, and partial tree mortality from pest outbreaks. Manual thinning or prescribed burning can be implemented to replace the natural disturbances that keep this forest open. This pathway leads to community phase 1.1.

Pathway 1.3b
Community 1.3 to 1.2

In the event of a canopy fire this community would move quickly to community phase 1.2.

Pathway 1.3c
Community 1.3 to 1.4

If fire does not occur, the density of the forest increases, favoring infill of white fir and incense cedar. The increased density shifts this community phase to the young forest infilling community phase, 1.4.

Pathway 1.4a
Community 1.4 to 1.2

Fire hazard is high and a severe crown fire would quickly shift the community phase to community phase 1.2.

Pathway 1.4b
Community 1.4 to 1.3

The natural event of a moderate or surface fire in this forest is unlikely due to the high fuels. Considerable management efforts would be needed to create the open forest conditions that should exist in this forest if it had developed with fire over time. Manual treatment to thin out the understory trees and fuels or prescribed burns could be implemented to shift this forest to community phase 1.3. A partial mortality pest infestation could also create a shift towards phase 1.3.

Pathway 1.4c
Community 1.4 to 1.5

Continued absence of fire would progress the community phase to older and older ages (community phase 1.5) with some additional infill of white fir and some incense cedar.

Pathway 1.5b
Community 1.5 to 1.1

The natural event of a moderate or surface fire in this forest is unlikely due to the high fuels. Considerable and repeated management efforts would be needed to create the open forest conditions that should exist in this forest if it had developed with fire over time. Manual treatment to thin out the understory trees and fuels and/or prescribed burns could be implemented to shift this forest toward community phase 1.1 provided enough Jeffrey pine was present in the overstory. A partial mortality disease or pest infestation could also create a shift towards community phase 1.1 provided enough overstory Jeffrey pine was present.

Pathway 1.5a
Community 1.5 to 1.2

Fire hazard is high and a severe crown fire would quickly shift this community phase to community phase 1.2.