Frigid, Udic, Unglaciated, Loamy, Hills, Mountains and Valleys, Mixed ash surface (western hemlock) Western hemlock/Brides bonnet-wild ginger

Description

This state results in an old growth western hemlock and western redcedar forest. Fire return intervals are far apart due to its moist environment. It is highly dynamic in its seral stages after major disturbance with many tree species capable of establishing and growing to mature age. Western white pine used to be a dominant tree in this state establishing after a severe fire and be a major overstory component in the mature to old growth phase, however, the white pine blister rust epidemic in the 1930s reduced it to a minor component in stand composition of current forests. White pine stabilized the site for long periods due to its disease and insect resistance. Currently Western Larch, Douglas-fir, Grand fir, cedar, and hemlock have taken its place in early stand establishment through the mature and old growth phases. This has led to more root rot in mature stands with Douglas-fir, Grand fir, cedar, and hemlock. Eventually, western hemlock and western redcedar dominate regeneration in mature stands and a hemlock-cedar forest develops without major disturbance. This state can be floristically rich with shrubs and herbs when canopy gaps are created. Major shrub species include big huckleberry, twinflower, pachistima, prince’s pine, pyrola, honeysuckle, and rose. Herbs include queencup beadlily, violet, western rattlesnake plantain, wild ginger, sword fern, Hooker fairybells, and twisted stalk. A key understory tree species in this ecological site is paper birch. It is usually more prominent early to middle seral stages and notable snags present in mature to old growth phases. Another key seral species descriptive of this ecological site is Sitka alder. It is present during the stand initiation phase located in moisture receiving areas. Redstem and snowbrush ceanothus species can be prominent in fire disturbed areas. Black cottonwood is also prominent seral species and usually died out by the mature forest phase.

Submodel

Description

Before the 1910 outbreak of western white pine blister rust N. Idaho and parts of NE WA were covered with white pine stands from pole to old growth stages. Severe fires over large acreages allowed white pine to establish and dominate the area. Mature to old growth stands of pine stabilized the area due to its root rot and insect resistance. A mixed understory of shrubs and forbs existed due to sufficient light coming through the white pine canopy. Cedar and hemlock regeneration would also have been present. Large fires again would allow the white pine to establish and the cycle would start again. The blister rust epidemic basically wiped out the white pine and eliminated this stable forest cycle. In its place Douglas-fir, grand fir, western larch, cedar, and hemlock increased in abundance through the growth stages. More root rot and insect mortality are now present in the stands. In addition, more cedar-hemlock stands reach old stages without a white pine component.
To address the white pine blister rust problem cooperative forestry organizations developed a blister rust resistant white pine that has been planted on hemlock and cedar sites. White pine can now be seen growing on these harvested areas.

Submodel

Description

Multiple severe fires keep site in a shrub field state.

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Description

With the increased abundance of Douglas-fir, grand fir, and hemlock in stand development since the white pine bister rust epidemic Armillaria root rot has increased creating pockets to large areas of shrub/small deciduous trees. These root rot areas can exist for long periods until resistant species establish. In areas with metasedimentary parent material this situation is amplified. Species resistant to Armillaria include western larch, white pine, and western redcedar (after seedling stage).

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