Climax Forest Communities
Mixed conifer forests include western red cedar, Sitka spruce, western hemlock, Douglas fir, big-leaf maple and red alder. Epiphytes are common, and include mosses, lichens, ferns, liverworts, selaginella and occasional shrubs. Grand fir may be found. Understory vegetation is dense and multilayered. Dominant tree seedlings are restricted to western hemlock, which is very tolerant of low light levels. Other species appear as seedlings only in light gaps.

Western hemlock forest is the dominant forest type except in drier areas, where Douglas fir is more common. Western red cedar grows on moist sites at all elevations. Without disturbance, western hemlock will dominate all forest sites over time. Wind throw, fire, disease and other disturbances leads to the inclusion of other tree species.

Coastal forests of Sitka spruce grow in a narrow zone in the fog belt, along the coast and slightly inland up river valleys. Epiphytes are abundant. Other understory species include salal, oxalis, swordfern, with red alder as an understory tree in light gaps.

True fir forests, higher elevations, usually above 1,500 feet, contain Pacific silver fir with shrub to open understories. Noble fir may also be found.

White oak woodlands and savannahs barely grow into the Columbia Coast region, but are common on the east side of the Coast Range and in the interior, particularly east of the Cascades. These open woodlands often transition into high elevation grasslands or balds, with a high diversity of grasses and forbs in the understory.

Wetland Forest Communties
Floodplain forests are found in river valleys, may contain black cottonwood with a mix of other hardwoods, including Oregon ash, several willows, red alder, and bigleaf maple. Floodplain forests may also be considered wetlands, though they are often only wet during peak spring and intermittent winter floods.

Swamps are forested wetlands. Common swamp species include Sitka spruce, western hemlock, western red cedar, red alder, Oregon ash, Hooker's willow, Scouler's willow, Pacific willow, western crabapple, and black cottonwood. They are found in fens, dune swales, floodplains in river valleys, and on perched wet soils in upland areas.

Logging of swamps (timbered wetlands) may lead to colonization by marsh species (sedges, rushes and grasses), under wetter conditions post-logging with higher water tables. Tree species may be impossible to establish afterwards, resulting in a permanent to centuries-long loss of tree habitat. With high water tables, swamps are often difficult to log. Shallow root systems growing on the surface with buttressed trunks are distinctive features of swamps.

Successional Forest Communties
Shore pine forests grows in a short-lived transitional stage between grasslands and Sitka spruce / western hemlock forests along the coast. In other parts of the world, this pine tree is considered a noxoius weed. It is fire tolerant, produces seeds at a young age in serotinus cones, and can reenter areas from the seed bank, growing in dense "dog hair" stands after fire, clearing or other disturbance just as its interior sibling, lodgepole pine does. Prior to the changes in landscape management of the past 100 years, shore pine was probably kept out of many old dune prairies by frequent fire, which kept young trees from establishing. Now this aggressive tree grows over thousands of acres of newly-formed land, adding to fire loads in forest communities. Species that replace shore pine in succession include Sitka spruce, western red cedar and western hemlock.

Red alder forests are a short-lived transitional stage between coniferous stands on disturbed sites. Pastures left ungrazed or mown for a decade will revert to red alder, and thence to conifers. Timber stands, once cut, will revert to red alder whether they are planted or not, leading to a widespread practice of using aerial applications herbicide to check broad-leaved species such as alder, maple, elderberry, and salmonberry on industrial forest lands. Alder fixes nitrogen and adds leaves to the duff layer each year, rapidly conditioning bare soil for other species, such as soil fungi and conifer seedlings. Conifers may be slow to replace alder on wet sites. A characteristic coastal community of red alder and slough sedge is found in local fens. Upland sites may display a red alder/sword fern community.

Douglas fir forests are successional along the coast, being unable to reproduce in closed canopies of mature conifers. There are isolated examples of natural Douglas fir forest throughout the region on dry or disturbed locations, where thin soils, fire or other factors kept other conifers out. Understories are more open than other coniferous forests; Oregon grape, salal, sword fern are common, and several herbaceous perennials may also be seen.

Industrial forests are characterized by even-aged, monocultures of trees, usually composed of western hemlock or Douglas fir. Average stand age is usually less than sixty years at harvest, and often no more than forty. Understory species are reduced, as trees are grown in dense, ground-shading proximity. Pre-commercial thinning at 20-35 years may open up stands to the ground. Salal, mosses, sword fern and salmonberry are common understory species.

Selective harvesting can be used to recreate the character of old growth, by altering spacing, tree ages, creating light gaps, and otherwise shifting stands from monocultures to more diverse conditions.


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