BOTANICAL AND ECOLOGICAL CHARACTERISTICS
SPECIES: Rubus spectabilis | Salmonberry 



GENERAL BOTANICAL CHARACTERISTICS : 
Salmonberry is a branching, glandless, large to small, deciduous shrub
which grows 7 to 13 feet (2-4 m) in height [48,66].  This rhizomatous
clonal species frequently forms large, dense thickets [29,61,66].  Stems
of most species within the genus Rubus are biennial.  Young twigs are
light brown and glabrous to pilose [48,66].  As twigs age, bark becomes
light brown to yellowish, hairless, and shreddy [48,66].  Leaves are
three foliate to simple [48].
 
The perfect flowers of salmonberry occur singly or in groups of two to
four on slender lateral stalks [48,66].  The showy, mildly
sweet-smelling flowers are pink to reddish purple [48,66].  The
salmon-colored or yellowish fruit, commonly referred to as a "berry", is
made up of many small glabrous drupelets [34,58,66].  Fruit is round to
ovoid or conic and 0.6 to 0.8 inch (1.5-2 cm) in length [48].


RAUNKIAER LIFE FORM : 
   Phanerophyte


REGENERATION PROCESSES : 
Salmonberry can reproduce sexually or vegetatively.  Reproductive
versatility is common in the Rubus genus; sexual reproduction,
parthenogenesis (development of the egg without fertilization),
pseudogamy (a form of apomixis in which pollination is required), and
parthenocarpy (production of fruit without fertilization) occur widely
[12].  The following types of reproduction have been documented within
the genus:  (1) sexual reproduction, (2) nonreduction at meiosis on the
female, male, or both sides, (3) apomixis with segregation, (4) apomixis
without segregation, and (5) haploid parthenogenesis [12].  The various
modes of asexual reproduction contribute to the vigorous, aggressive
spread of species within the Rubus genus.
 
Vegetative regeneration:  The mostly biennial stems typically develop
from perennial root stocks or aboveground creeping stems [26].
Salmonberry is known for its prolific sprouting ability.  It can sprout
vigorously from the stump, root crown, stem base or root stock, and from a
dense network of rhizomes [5,61,70].  Regeneration through rooting
aerial stem tips has also been reported [5].  Salmonberry exhibits
vigorous vegetative response to fire, mechanical removal, and other
types of disturbance but spreads vegetatively even in the absence of
disturbance.  Vegetative regeneration is largely responsible for the
clonal spread of this species and is particularly important in
perpetuating colonies in shaded understory habitats [5].  Stand dynamics
are primarily related to mortality and the rate at which new individual
ramets develop [61].  As older ramets die they are replaced by new
ramets, and the population tends to remain relatively stable [61].
Under ordinary circumstances, recruitment of new genets through seedling
establishment is relatively rare [61]..

Stump-sprouting:  Once aboveground foliage has been damaged or removed,
buds present on the stump exhibit the greatest immediate potential for
regrowth [70].  These sprouts soon establish apical dominance and
inhibit other less active buds located at or below the ground surface
[70].  The number of these buds which are capable of sprouting is
largely determined by the height of the remaining stump [70].

Stem base, root stock, or root crown:  The second portion of the
salmonberry bud bank, which is activated after removal of the stump,
is the stem base or root crown.  These buds, located at or below the soil
surface, are afforded greater protection than those on the stump.
However, these buds tend to develop more slowly than stump buds because
of the cooler environment in which they occur [70].  In general, the
deeper the bud, the slower the sprouting response [70].  Buds located on
the stem base or root crown can ordinarily be eliminated only through
extreme soil disturbance [7].
 
Rhizomes:  Rhizomes represent the most complex and largest segment of
the salmonberry bud bank [70].  These structures are capable of
relatively rapid production of aerial stems [61] and are responsible for
local increases in stem density [5].  Ramets are connected by a
complicated network of rhizomes which average 0.2 to 2.0 inches (5-50
mm) in diameter and generally lie 1 to 2 inches (2-5 cm) below mineral
soil [61].  Rhizomes often extend to depths of 3.9 to 7.9 inches (10-20
cm) and although usually restricted to the top foot (31 cm) of soil, can
extend to depths of 6 feet (1.8 m) or more [70].  Rhizome development is
often extensive.  In some clearcuts, total rhizome length averages up to
42 miles (68 km) per stand [70].  Averages of 20 to 30 miles (32-48 km)
per stand are common in areas which have been logged [70].
 
Rhizome growth and development is related to basal area of the stand,
age of the parent plant, and site characteristics.  Greater basal areas
are generally correlated with more extensive rhizome growth [70].
However, large, old rhizomes generally possess fewer buds and exhibit
somewhat reduced sprouting abilities compared with young rhizomes [70].
Young rhizomes are generally capable of rapid and active growth.  Oneto
two-year-old rhizomes typically exhibit high bud densities (1 to 2 per
inch (2-5 cm)) [70].  Rhizome growth has been found to vary by site as
shown below [61]:
 
                     annual growth          site 
                     (m) 
 
                     1.9                    clearcuts 
                     0.7                    red alder  
                     0.4                    conifer 
                     0.1                    riparian 
 
On extremely rocky sites, rhizomes may be uncommon or even absent [61].
 
Layering:  Salmonberry can spread as downward arching aerial canes which
become buried by litter, subsequently root, and produce new aerial
shoots [5].  Aboveground portions of the cane can also root and produce
new clones when damaged mechanically [5].
 
Seed:  Species within the genus Rubus grow from perennial root stocks or
creeping aboveground stems during their first year of development and
produce sterile vegetative shoots known as primocanes [26].  Lateral
branches, or floricanes, develop in the axils of the primocanes during
the second year and produce both leaves and flowers [26].  The showy
flowers of salmonberry are pollinated by insects and hummingbirds
[5,49].  Salmonberry generally produces large numbers of seed annually
[5].  Immature fruit is pink and hard [8].  Ripe "berries" are red,
yellow, or orange and are made up of an aggregate of many small
drupelets [5,8,66].  "Berries" average 30 per shrub [45].
 
Germination:  Salmonberry seeds have a hard, impermeable coat and a
dormant embryo [5,8].  Consequently, germination is often slow, and
generally requires some form of mechanical or chemical scarification
[5].  Most Rubus seeds require, as a minimum, warm stratification at 68
to 86 degrees F (20 to 30 degrees C) for 90 days, followed by cold
stratification at 36 to 41 degrees F (2 to 5 degrees C) for an
additional 90 days [8].  Stratification occurs naturally as seeds mature
in summer and remain in the soil throughout the cold winter months.
Laboratory tests indicate that exposure to sulfuric acid solutions or
sodium hyperchlorite prior to cold stratification can enhance
germination [8].  Light is not required for germination; germination can
proceed despite relatively low temperatures [5].  Most germination
occurs during the first growing season after disturbance.  Ruth [53]
observed that second season germination represented only 6 percent of
that which occurred during the first growing season.

Seed banking:  Salmonberry seed is typically long-lived when buried in
the soil or duff [5].  Large numbers of seed are present in the topsoil
of many coastal forest stands [36].
 
Seed dispersal:  Salmonberry seed is readily dispersed by many birds and
mammals [5,8].  After they mature, the highly sought-after fruits rarely
remain on the plant for long [8].  Evidence suggests that the action of
avian gizzards and exposure to mammalian digestive acids provide
beneficial scarification which enhances germination [5].  A relatively
long period of fruiting in salmonberry (2 months) increases the
probability of seed dispersal as flocks of migrating birds move through
an area [5].
 
Seedling establishment:  Salmonberry seedlings require mineral soil for
good early development, and establishment is generally poor unless the
soil has been disturbed [5].  Scarification following timber harvest
generally creates an excellent seedbed for salmonberry.  Large numbers
of seedlings can readily establish on sites which have been logged and
then scarified [53].  Researchers have observed up to 500,000 seedlings
per acre (1,234,568/ha) in some scarified cutting units [53].  The
presence of a thick leaf mat can inhibit seedling establishment [5].


SITE CHARACTERISTICS : 
Salmonberry grows on a wide range of sites.  It is particularly
prevalent on mesic sites in forest openings, along waterways, on river
terraces, gravel bars and avalanche chutes, or in seeps and swamps
[10,17,29,34,66].  Salmonberry is abundant along roadsides, fencerows,
and on many types of disturbed sites [5].
 
Soils:  Species within the Rubus genus typically grow well on a variety
of barren, infertile soils [8].  Salmonberry tolerates a wide range of
soil types and grows well on rich loam, loamy clays, pure peat, and
excessively drained gravel [5].  Soils tend to be acidic and of
relatively low fertility [5].  Soils supporting salmonberry are often
saturated for much of the year [29].  Good growth has been reported on
rocky alluvium with a high percentage of fines and a well-developed
humus layer [10].  In the Siskiyou Mountains of southern Oregon and
northern California, soils are frequently derived from diorite or gabbro
[68].
 
Elevation:  Salmonberry typically grows at low to middle elevations
[34].  In western Washington, it is particularly abundant under forest
canopies at lower elevations but is largely restricted to stream and
lake margins at higher elevation [5].  Generalized elevational ranges in
California and Washington are as follows [5,48]:
 
               < 1,000 feet (305 m) in CA 
               from 0 to 4,500 feet (0-1,400 m) in WA 


SUCCESSIONAL STATUS : 
Salmonberry is a pioneer or early seral species noted for its ability to
spread aggressively on disturbed sites [5].  A certain amount of soil
disturbance is essential for good seedling establishment.  Seedlings
generally appear in abundance after fire, timber harvest, or other types
of disturbance [1,2,5,53,69].  Rhizomes enable salmonberry to spread
vigorously and form dense patches where it was prevalent in
predisturbance communities [5,61].  In many areas dense stands may form
within 2 to 3 years after disturbance [61].  Salmonberry communities
commonly develop early in succession in Sitka spruce and Pacific silver
fir zones of Oregon and Washington [20], in Sitka spruce-western hemlock
forests of Alaska, and in many Douglas-fir forests of the Pacific
Northwest [18].  In northern California, salmonberry was abundant during
the first 5 to 10 years after disturbance in grand fir-Douglas-fir-Sitka
spruce communities and in early seral redwood-grand fir communities
where it persisted, although in reduced abundance, for 30 years or more
[71].  In many areas, the cover of salmonberry, a nitrogen-demanding
species, begins to decline 2 to 5 years after clearcutting as available
nutrients decline [39].
 
Salmonberry has been described as shade tolerant [5,53] and relatively
intolerant of shade [22,27].  In some locations this shrub persists in
climax forest communities; elsewhere it is gradually eliminated as the
canopy closes.  Although most common in early seral stages, salmonberry
has also been reported in early immature, second growth, mature, and old
growth forests in British Columbia [39,45].  Alaback [2] noted that
salmonberry is gradually eliminated in Sitka spruce-western hemlock
forests of Alaska as the forest overstory develops.  However, other
researchers have reported salmonberry in climax western hemlock or
western hemlock-Douglas-fir forests of British Columbia [27,39,45] and
in climax coastal forests to the south [53].
 
Salmonberry commonly persists within the understory of various hardwood
communities [5].  It can reportedly persist almost indefinitely in the
understory of alder or mixed hardwood-conifer stands [5].  Salmonberry
is more likely to be eliminated in coniferous forests where light levels
are lower.  However, in many coniferous stands, parts of salmonberry
clones senesce, die, and decay as the overstory canopy closes, but then
the clone slowly expands as self-thinning of the conifers occurs [61].
Tappeiner and others [61] noted that "the natural success of salmonberry
communities may result in relatively permanent pure shrub communities."
 
Salmonberry is present in red alder communities of the Northwest, which
on certain upland sites appear to be early seral stages of western
hemlock forests [32].  However, where these communities occur along
streambanks, periodic flooding can maintain species such as salmonberry,
red alder, and stink currant in long-lived disclimax situations [10,32].


SEASONAL DEVELOPMENT : 
The leaves of salmonberry begin to appear early in the spring, often
when the ground is still covered with snow [5].  Researchers in western
Washington have observed the first leaves by March 21, at which time
initial annual rhizome growth was also noted [5].

Flowering dates depend on geographic and climatic factors, but flowering
usually occurs from early to late spring.  In many areas along the
Pacific Coast, the time of flowering appears to be correlated with the
arrival of the migrating rufous hummingbird, which may serve as an
important pollinator [49].  Generalized flowering and fruiting dates by
location are as follows [5,8,45,66]:
 
     location         flowering           fruit-ripening
 
        AK            May-June            June-August 
        AK            April-June          early July (Aug. at higher elev.)
        CA            March-June              ----- 
      w WA            April               May 16-July 26 
        BC            --------            May-July                            
 
Seed dispersal coincides with the time of fruit availability.  In many
areas, seed is dispersed from June through August [8].

The tips of the terminal buds remain active and continue elongating
until August, when dormancy generally begins [5].  Leaves typically fall
by late October or November [10,33].  Campbell and Franklin [10]
observed maximum leaf drop in the western Cascades during the fourth
week of October; 56 percent of the leaves dropped during the first 3
weeks after frost.

Related categories for Species: Rubus spectabilis | Salmonberry