BOTANICAL AND ECOLOGICAL CHARACTERISTICS
SPECIES: Berberis nervosa | Dwarf Oregon-Grape 



GENERAL BOTANICAL CHARACTERISTICS : 
Dwarf Oregon-grape is a low-growing rhizomatous evergreen shrub which
typically reaches 4 to 24 inches in height [28,69].  On exceptional
sites, plants may grow to 7 feet (2.1 m) [81].  The simple stems are
ascending to erect and generally occur in loose colonies of several
stems [69,46,71].  Compound leaves are borne in terminal tufts [66,69].
Coarsely serrate to spinose, ovate to lance-ovate or acute leaflets
occur in groups of 7 to 21 [46,69,95].  Leaflets are dark green, thick,
and leathery [71,95].  Yellow flowers are borne in erect clusters or
racemes up to 8 inches (21 cm) in length [66,69,71].  The fruit is a
large, dark blue, globose berry with grayish or whitish bloom
[28,69,71,95].  Berries are 0.3 to 0.4 inch (8-10 mm) in diameter, occur
in clusters [35], and contain a number of black seeds [95].


RAUNKIAER LIFE FORM : 
   Phanerophyte


REGENERATION PROCESSES : 
Dwarf Oregon-grape can reproduce from seed or by vegetative means.

Seed:  Seed of most Oregon-grapes exhibit internal dormancy and require
cold stratification for germination.  However, in certain laboratory
tests, dwarf Oregon-grape seed did not germinate after 90 days of cold
stratification [75].  Results of other studies indicate that seed will
germinate if sown immediately or if stratified and planted in the spring
[15].  Maximum germination capacity in laboratory tests was estimated at
77 percent [75].  Under natural conditions, seeds of most species within
the genus germinate during the spring [15].  The role of sexual
reproduction on disturbed sites is poorly known [32].

Vegetative regeneration:  Dwarf Oregon-grape is rhizomatous [47] and
gradually expands laterally in the absence of disturbance.  Layering has
also been reported [15].  Plants generally sprout from rhizomes or
"creeping rootstocks" after aboveground portions of the plant are
destroyed [47,74,87,91].  Vegetative regeneration appears to be the
dominant mode of regeneration after fire or other disturbances [32].


SITE CHARACTERISTICS : 
Dwarf Oregon-grape occurs across a wide range of habitats in submontane
to montane forests of the Pacific Northwest [35,54].  It is a
characteristic shrub of spruce-fir forests [14] but also occurs in
northern coastal coniferous forests and in redwood, mixed evergreen, and
bottomland forests [30,69,78].  In Pacific silver fir communities, dwarf
Oregon-grape is generally restricted to warm, dry sites.  In old-growth
Douglas-fir stands of northwestern Oregon, it reaches greatest abundance
on relatively dry sites [82].  This shrub occurs on dry to fairly moist
sites in western hemlock types but reaches greatest abundance on warmer
sites [42,85].  Dwarf Oregon-grape is also common in the warmer
Port-Orford-cedar communities [3].

Dwarf Oregon-grape commonly grows as scattered, or abundant, individuals
but can dominate the understory of semiopen forests [54].  It frequently
forms "lush carpets" in open meadows bordering coniferous stands [71]
and commonly persists in coastal brushfields created by timber harvest
[33,43,51].  Dwarf Oregon-grape grows well in sun or shade [54,87].

Plant associates:  Common overstory associates in addition to those
mentioned above include Pacific yew (Taxus brevifolia), Sitka spruce
(Picea sitchensis), and tanoak (Lithocarpus densiflora)
[2,31,42,74,84,89].  In spruce-fir forests, dwarf Oregon grape grows
with understory species such as twinflower, rhododendron (Rhododendron
spp.), and queencup beadlily (Clintonia uniflora).  Beargrass
(Xerophyllum tenax) occurs on drier sites [23].  Common associates in
Douglas-fir or western hemlock forests include oceanspray, trailing
blackberry (Rubus ursinus), red huckleberry (Vaccinium parvifolium),
Alaska huckleberry, salal, Pacific rhododendron, vine maple, broadleaf
starflower (Trientalis latifolia), and mosses such as Kindbergia oregana
[21,32,44,54,67].  Old-growth stands are often characterized by a
depauperate understory [48].  In redwood (Sequoia sempervirens)
communities, western swordfern, salal, Oregon oxalis, and redwood violet
(Viola sempervirens) are common associates [60].

Soils:  Dwarf Oregon-grape grows well on a variety of soil types [70]
including coarse, shallow rocky soils, coarse alluvium, or glacial
outwash [39].  Soils are well drained to poorly drained, and dry to
fresh [28,54,70].  Soils are derived from a wide range of parent
material including basalt and metavolcanics, sandstone, siltstone,
diorite, and gabbro [3,7,44,90].  Good growth has been reported on
acidic to moderately alkaline or even somewhat saline soils [70].

Climate:  Dwarf Oregon-grape grows in maritime to submaritime climates.
Growing seasons are fairly long [35].  Some sites experience summer
drought [43].

Elevation:  Dwarf Oregon-grape grows at low to middle elevations
[35,90].  In California, it is restricted to sites below 6,000 feet
(1,829 m) [69].


SUCCESSIONAL STATUS : 
Facultative Seral Species

Dwarf Oregon-grape is an important component of both seral and climax
communities of the Pacific Northwest.  It occurs in recent clearcuts as
well as in stands 300 to 600 years or older [20,82].  It is a woody
survivor or residual colonizer, generally increasing dramatically after
low intensity disturbances such as light fires [32,91].  It commonly
persists on cutover [54] or lightly burned sites.  Residual survivors
sprouted soon after the eruption of Mount St. Helens [34] and were
particularly evident in protected microsites such as near the bases or
rootwads of trees.  The intensity of disturbance, and of fires in
particular, exerts a great influence on dwarf Oregon-grape [33,58].  In
many areas, it codominates a site soon after light-severity disturbance
but may decline in early seral stages when it is overtopped by rapidly
growing conifer seedlings [33,49].

Annuals and weedy invaders commonly dominate early seral stages where
disturbance has been intense [58].  Fireweed and wood groundsel (Senecio
sylvaticus) assume dominance during the first 1 to 3 years on many
intensely disturbed sites [71].  Perennials such as dwarf Oregon-grape
may not become prominent on intensely burned sites until midsuccessional
stages.  In some areas, 30 to 40 years or more may be required before
maximum abundance of dwarf Oregon-grape is reached [79].  It does not
attain maximum cover until later seral stages in many western
redcedar-western hemlock-Douglas-fir forests of thge Cascade Ranges of
Oregon and Washington [18,49]. 

Dwarf Oregon-grape can assume importance in shrub-dominated stages which
develop 4 to 5 years after disturbance in western hemlock forests of the
Pacific Northwest [24], and can achieve peak abundance within 5 to 10
years after fire in many parts of this region [32].  In the central
Oregon Coast Ranges, is exhibits rapid regrowth and shares understory
dominance in 7- to 50-year-old forests [7].

Dwarf Oregon-grape is tolerant of shade and can complete its life cycle
even in dense forests of the Pacific Northwest [73].  In the Coast
Ranges of central Oregon, it dominates many old-growth western
hemlock-western redcedar forest understories [7].  It is also an
important component of many climatic or topoedaphic climax western
hemlock communities [4,38,39].  Many seral Douglas-fir/dwarf
Oregon-grape communities ultimately give rise to climax western hemlock
types [38,39] as Douglas-fir declines late in succession [7].  Late
seral Douglas-fir/vine maple-dwarf Oregon-grape communities become
climax western hemlock-Pacific rhododendron-dwarf Oregon-grape
communities [24].


SEASONAL DEVELOPMENT : 
Plants flower in early to late spring.  Fruit ripens during July and
August [87].  Generalized flowering and fruiting dates are as follows
[35,46,69,75,95]:

            location                 flowering         fruit ripe

            Northwest                March-June            --
            CA                       April-June            --
            OR (300 ft [91 m])       early April       mid-August
            OR (3,250 ft [991 m])    mid-May           late August
            w OR, sw WA              March-June            --
            WA                       May                September
     

Related categories for Species: Berberis nervosa | Dwarf Oregon-Grape