100
UNITED STATES AND CANADA
Society of American Foresters
F.H. Fyre, Editor
1980
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North Pacific Red Alder
221
Definition and composition. -:Red alder either
occurs in pure stands or comprises a majority of the
stocking. The type is usually pure near water, in
moist coves, and in early stages of succession after
soil disturbance. In other situations it is mixed with
other short-lived hardwoods or with longer-lived
conifers. Major hardwood associates include bigleaf
maple, black cottonwood, Pacific willow, and bit­
ter cherry; coniferous associates are Douglas-fir,
Sitka spruce, western hemlock, western redcedar,
and grand fir. Minor tree associates are. western
paper birch in the northern part of the type range;
cascara buckthorn, vine maple, and Oregon ash in
the central part; and redwood, Port Orford-cedar,
and Oregon ash in the southern section (Worthing- .
ton 1957). Stands are typically even aged.
Geographic distribution. -Generally the type is
confined to the Pacific Coast region from Yakutat
Bay in southeastern Alaska to Santa Barbara in
southern California. Except for a disjunct popula­
tion in northern Idaho Gohnson 1968), red alder
seldom occurs further inland than 160 km (100 mi.)
or at an elevation higher than 750 m (2,300 ft.).
The type is common in bottomlands of the Pacific
Coast. In southeastern Alaska, it occurs on stream
banks and beaches, and in western Washington and
Oregon, also in sheltered coves and on moist slopes
of the Coast and Cascade ranges (Franklin and Dyr­
ness 1973). The area suitable for growing alder is
gradually being reduced by land clearing and in­
dustrial development in the lower river valleys.
Ecological relationships. -The type is always
seral. Increasingly it replaces the Pacific Douglas­
fir and western hemlock-Sitka spruce typeS" after
disturbance by logging, landslides, or fire. Because
it demands light, red alder must be dominant or co­
dominant to survive (Worthington 1957). The spe­
cies' early seed-bearing age, abundant annual seed
crops, and effective seed dispersal give it an advan- .
tage over competing species, particularly conifers
(Trappe et al. 1968). Red alder has no serious in­
sects or diseases.
Common successors to red alder on wet sites are
·
salmonberry, vine maple, and California hazel·
they can form semipermanent brushfields (Trap
et al, 1968). Alder can also succeed itself on wet
sites (Worthington et al. 1962). On mesic and drier
sites in Oregon, western hemlock: or Sitka spruce
may eventually succeed red alder, but Douglas-fir is
virtually absent except where it develops in open­
ings within the alder type (Trappe et al. 1968). Red
alder improves soil fertility through nitrogen fixa­
tion and production of large amounts of litter (Za­
vitkovski and Stevens 1972, Gessel and Turner
·
1974).
Variants and associated vegetation. -The distri­
bution of red alder overlaps slightly that of three
other alder species: white, mountain, and Sitka. Of
'the four, only red and white alder reach.large size,
In the Sierra Nevada, white alder is a common
streamside tree and forms a type imilar to red
'alder. Red alder, a minor component in the Sitka
spruce and western hemlock-Sitka spruce types,
occurs in_ patches in most Pacific Coast conifer
types.
Shrubby species often form dense layers in alder
stands.. Common shrubs associated with red alder
are Pacific red elder, blueberry elder, salmonberry,
thimbleberry, devilsclub, and osoberry (Indian
plum) (Worthington 1957).
RicHARD E Mn.LER
USDA Forest Service
Pacific Northv;-est Forest and
Range Experiment Station
..
Black Cottonwood-Willow
222
. Definition and c
position. -Black cottonwood
generally comprises the
ro£ the stocking and
jo
sometimes is pure, but
rescent willows often
are present in :rpixture
d 'max_ predominate lo­
cally. Major willow SP,ebies include PaCific, north­
west, river, and sqd"Uier willow (Franklin and
Dyrness 1973). Redfoder may be present. Minor as­
sociates in the type include bigleaf and vine maples,
Oregon ash, black hawthorn, and other bottomland
·
_,
',