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