State 1
Reference

Community 1.1
Western Hemlock, Douglas-fir, Salal, Oval-leaf Huckleberry, Western Swordfern, and Western Cordilleran Bunchberry

Western hemlock – Douglas-fir / salal – oval-leaf huckleberry / western swordfern – western Cordilleran bunchberry

Structure: mosaic of mature overstory and regenerating openings

Western hemlock and Douglas-fir are the most common overstory species in the Reference Community which lacks major disturbance for at least 100 years. Western hemlock is the most shade tolerant species in this forest and regenerates successfully in the understory. Douglas-fir and western redcedar (Thuja plicata) may be codominant in the overstory, but regeneration is limited to gaps in the canopy. Gaps in the mid-canopy and overstory allow sunlight to reach the ground and are where the majority of the understory plants establish. In addition, these gaps provide opportunities for deciduous tree species such as red alder to regenerate throughout this reference community. Common understory shrub species include salal, red huckleberry (Vaccinium parvifolium), oval-leaf huckleberry, vine maple (Acer circinatum), twinflower (Linnaea borealis), Cascade oregongrape (Mahonia nervosa), deerfoot vanillaleaf (Achlys triphylla), deerfern (Blechnum spicant), western swordfern, and western cordilleran bunchberry.

Community 1.2
Red Alder, Douglas-fir, Trailing Blackberry, and Western Swordfern

Red alder – Douglas-fir / trailing blackberry / western swordfern

Structure: open forest with abundant regeneration and snags

Community phase 1.2 is an early seral plant community that has been impacted by a stand-replacing disturbance such as a wildfire, large scale wind event, mass movement, or major insect pest or disease. Nearly all trees are absent, but some fire-resistant trees may survive in the overstory. Snags are prevalent and remain standing and decaying. Large woody debris may be present on the surface and serve as nurse sites. The understory is predominately early seral tree, shrub, and forb species such as red alder, red huckleberry, trailing blackberry (Rubus ursinus), and western swordfern. Red alder has several competitive advantages and can establish quickly, relative to conifers. Red alder can sprout and establish in full sunlight and fixes nitrogen providing an early competitive advantage (Villarin, 2009). In addition, the seeds of deciduous species are light and can be transported long distances by wind and water, allowing for rapid recolonization. Red alder seedlings and saplings will typically establish 3 to10 years following disturbance, depending on severity.
Douglas-fir is relatively fire resistant and can survive moderately intense fires, due to its thick corky bark. Depending on fire severity and cambium damage, a mature Douglas-fir component may remain as a dominant overstory species, while western red cedar and western hemlock may be at full stand replacement post fire.
When resulting from a moderate to severe fire event, there is a good probability for shrubs to out-compete tree seedlings. Vine maple, red huckleberry, salal, and Cascade Oregongrape (which may have been only moderately abundant previously) all have the capacity to rapidly recover and spread when top-killed, slowing successful overstory regeneration. Seed sources for tree species would be from the surrounding, undisturbed forest and any of the survivors of the disturbance and would result in a mixed stand which could include Douglas-fir, western hemlock, red alder (Alnus rubra), bigleaf maple (Acer macrophyllum), and western redcedar.

Community 1.3
Douglas-fir, Red Alder, Cascade Oregongrape, Salal, and Western Swordfern

Douglas-fir – red alder / Cascade Oregongrape – salal / western swordfern

Structure: dense single story

Community phase 1.3 is an early seral forest in regeneration, possibly with scattered remnant mature trees. Species composition depends on the natural seed sources present and the intensity of disturbance. When resulting from a moderate to severe fire event, it is probable that shrubs will out-compete tree seedlings. Red alder, red huckleberry, western swordfern, and Cascade Oregongrape may be abundant in the understory depending on sunlight availability.
Red alder will begin to die between 40 to 70 years following disturbance and allow more light to penetrate the newly nitrogen rich soil (Naiman, 2009). As a result, conifer regeneration becomes more prevalent in this community phase. Douglas-fir will begin to regenerate rapidly and increase in dominance, creating thick patches of regenerating saplings. Species composition depends on the natural seed sources present and the intensity of disturbance.

Community 1.4
Douglas-fir, Western Hemlock, Salal, Oval-leaf Huckleberry, Western Swordfern, and Western Cordilleran Bunchberry

Douglas-fir - western hemlock / salal – oval-leaf huckleberry / western swordfern – western cordilleran bunchberry

Structure: dense single story with diminished understory

Community phase 1.4 is a forest in the competitive exclusion stage, possibly with scattered remnant mature trees. There is increasing competition among individual trees for available water and nutrients. Douglas-fir and western redcedar, will dominate the overstory canopy, however red alder may be present in pockets of canopy openings. In addition, western hemlock is very shade tolerant and will begin to establish in the shade of mature Douglas-fir and western redcedar. Canopy closure is almost 100 percent leading to diminished shrub and forb layers. Some understory species better adapted to at least partial shade will begin to increase. Over time, the forest will begin to self-thin due to the elevated competition.

Pathway 1.1A
Community 1.1 to 1.2

This pathway represents a major stand-replacing disturbance such as a high-intensity fire, large scale wind event, major insect pest infestation, timber management, or large mass movement event leading to the stand initiation phase of forest development.

Pathway 1.2A
Community 1.2 to 1.3

This pathway represents growth over time with no further significant disturbance.

Pathway 1.3A
Community 1.3 to 1.2

This pathway represents a major stand-replacing disturbance such as a high-intensity fire, large scale wind event, major insect pest or disease infestation, timber management, or large mass movement leading to the stand initiation phase of forest development.

Pathway 1.3B
Community 1.3 to 1.4

This pathway represents growth over time with no further major disturbance.

Pathway 1.4B
Community 1.4 to 1.1

This pathway represents growth over time with no further major disturbance.

Pathway 1.4A
Community 1.4 to 1.2

This pathway represents a major stand-replacing disturbance such as a high-intensity fire, timber management, large scale wind event, major insect pest or disease infestation, or large mass movement leading to the stand initiation phase of forest development.

State 2
Disturbed

Community 2.1
Red Alder, Himalayan Blackberry, and Common Gorse

Red alder/Himalayan blackberry-common gorse

Structure: Open forest with regeneration and large woody debris

Community Phase 2.1 represents a recently disturbed forest that is naturally regenerating. Large woody debris is often prolific following large-scale disturbances which inhibits vegetation to establish under natural conditions. Areas that are not replanted immediately (1 to 3 years) following a timber harvest or large-scale disturbance may become vulnerable to invasive species infestation.
Typically, commercially managed forests will be replanted following disturbance and species preference depends on site conditions and long-term economic market decisions. Overall, species biodiversity in forests managed for short rotation timber is diminished.
Natural reforestation depends on available seed sources following disturbance. Early seral species such as red alder tend to regenerate quickly with abundant sunlight. Plant community composition is typically homogenous and even-aged. Following disturbance, these sites are often dominated by common gorse (Ulex europaeus), Himalayan blackberry (Rubus armeniacus), and Scotch broom (Cytisus scoparius) which tend to outcompete native species establishment. Invasive species management is most critical during this phase.

Community 2.2
Douglas-fir, Red Alder, Salal, and Himalayan Blackberry

Douglas-fir-red alder/salal-Himalayan blackberry

Structure: Single story

Community phase 2.2 represents an even-aged, regenerating forest. Douglas-fir can regenerate quickly on nurse logs or in recently disturbed soils. Shade-intolerant red alder remains a large component in the overstory until it reaches maturity (Fonda, 1974).
The vegetation in areas that have been replanted commonly is dense and even aged, and the understory species are sparse in areas that have a high percentage of canopy cover. Salal is a common understory species, but invasive species increase in prominence. Scotch broom, common gorse, and Himalayan blackberry can greatly impact the shrubby understory and outcompete native species. Scotch broom and common gorse are shade-intolerant and will diminish as the canopy cover increases. Management techniques such as pre-commercial thinning and mitigation of invasive species will accelerate the maturation and improve the health of the forest.

Community 2.3
Douglas-fir, Western Hemlock, Salal, and Himalayan Blackberry

Douglas-fir-western hemlock/salal-Himalayan blackberry

Structure: Dense single story with diminished understory

Community phase 2.3 represents a maturing forest that has increased plant diversity. Western hemlock can regenerate under dense, shrubby canopies. It will begin to establish in the overstory canopy along with Douglas-fir. Invasive species will inhibit the overall health and structure of the forest, creating an ecosystem which is susceptible to devastation from insects and disease. The dense, shrubby understory is susceptible to wildfires.
Commercial logging operations commonly take place during this phase as trees reach economical maturity in size and volume. It is presumed that without timber management during this phase, an old-growth western hemlock stand will develop.

Pathway 2.1A
Community 2.1 to 2.2

This pathway represents growth over time with no further major disturbance or active forest management.

Pathway 2.2B
Community 2.2 to 2.1

This pathway represents a major stand-replacing disturbance such as a high-intensity fire, a large-scale wind event, a major insect or disease infestation, large mass movement, or timber harvest activities that lead to the stand initiation phase of forest development.

Pathway 2.2A
Community 2.2 to 2.3

This pathway represents growth over time with no further major disturbance or active forest management.

Pathway 2.3A
Community 2.3 to 2.1

This pathway represents a major stand-replacing disturbance such as a high-intensity fire, a large-scale wind event, a major insect or disease infestation, large mass movement, or timber harvest activities that lead to the stand initiation phase of forest development.

Transition T1A
State 1 to 2

This pathway represents an area of major disturbance that removes most of the overstory. Large-scale disturbances such as this, have the potential to increase the vulnerability of invasive species infestation when the seed source is either nearby or introduced to the site. This type of disturbance will impact the ecological site and the natural feedbacks that maintained the reference state.

Transition T2A
State 2 to 1

This pathway represents intensive management to restore the historic plant community.