BOTANICAL AND ECOLOGICAL CHARACTERISTICS
SPECIES: Arctostaphylos uva-ursi | Bearberry 



GENERAL BOTANICAL CHARACTERISTICS : 
Bearberry is a prostrate, evergreen shrub that produces extensive
trailing stems [92].  The bark is thin and exfoliates in largish flakes
[142].  The leathery, dark green leaves are about 0.5 to 1 inch
(1.27-2.54 cm) long.  The flowers are borne in terminal racemes [59] and
are followed by bright red berrylike drupes, 0.25 to 0.4 inch (6-10 mm)
broad. Each drupe contains five (sometimes four) single-seeded nutlets
[50,59].

In western Montana, bearberry roots were found to extend to a depth of
36 inches (91 cm) on one site and 72 inches (183 cm) on a drier site
with the same soil type [100].  In two jack pine stands in central
Alberta, bearberry roots extended from 43.3 to 53.1 inches deep (110-135
cm) [135].

The forms (sometimes classed as varieties) of bearberry are primarily
distinguished by the types of pubescence.  These have been described in
detail [15,117,142].


RAUNKIAER LIFE FORM : 
   Chamaephyte


REGENERATION PROCESSES : 
Vegetative:  Regeneration is primarily asexual [129].  After the second
year, the stems (stolons) produce adventitious, feeding roots at the
nodes which seldom grow deeper than the duff layer [92].  If a stem is
severed from the original plant, roots develop which penetrate into
mineral soil [92].  When plants are growing in sandy soil or loose duff,
the creeping stems often grow under the surface [14,111,129].  After 7
or 8 years, small nodules may appear at intervals along buried stems.
These nodules resemble nitrogen-fixing root nodules but examination has
shown these nodules to be composed of latent buds that have no ability
to fix nitrogen [38,136].  In eastern North America and Scotland, plants
subjected to physical damage or fire appear to have more of these
structures [136].  On 10-year-old or older stems, there may be as many
as 100 buds surrounding the lignotuber [111].  Bearberry's clonal
pattern is generally compact.  Recruitment of new seedlings into
established clones has been reported [36].  A growth model based on a
detailed study of the morphology and growth of bearberry is available
[111,112].

Seed:  The berrylike drupes persist on the plants through winter and are
dispersed by animals and gravity [114,134].  Seeds have hard seedcoats
and dormant embryos, and may be stored in the soil [11,81].  Soil-stored
seed has been found near the surface [87].  Study results indicate that
removing the surface litter increases seedling establishment, although
the total number of germinants in this study was very small [87].  In a
natural environment, seedling growth is slow for the first 3 years, then
increases.  During the first year, root growth exceeds shoot growth
[111].  Bearberry plants which originated naturally as seedlings appear
to be rare [111].


SITE CHARACTERISTICS : 
Habitat:  Bearberry is most often a dominant understory species in open
pine forests under jack pine (Pinus banksiana), lodgepole pine (P.
contorta), limber pine (P. flexilis), ponderosa pine (P. ponderosa) or
pitch pine (P. rigida) [47,96,113,138,148].  It is also found in the
understories of Douglas-fir (Pseudotsuga menziesii), subalpine fir
(Abies lasiocarpa), white spruce (Picea glauca), black spruce (P.
mariana), paper birch (Betula papyrifera), aspen, and some eastern
deciduous forests [6,30,96,134].  In the Pacific Northwest and Rocky
Mountains, it grows on steep, sunny, dry slopes [41,131].  In the
southern boreal forests of Saskatchewan and Manitoba, bearberry is
characteristic of dry and very dry forests [113].  It is common in
heathland communities but grows in a variety of boreal forest sites,
including eroded banks and peat bogs.  It also grows in sand-dune areas
of subboreal regions [111].  Bearberry is fairly abundant in the alpine
zone of the Northwest and northern Rocky Mountains and may be dominant
on stable, well drained, south-facing sites [10,27,31,32,33].  It grows
under Oregon white oak (Quercus garryana) in Washington woodlands [42].
Bearberry is conspicuous in the Badlands of eastern Alberta [96].  In
the foothills of the northern Great Plains, it grows in the rough fescue
(Festuca scabrella) prairie [21,80].  In the Alaskan taiga, bearberry
occupies warmer sites [140].

In Michigan and Wisconsin, bearberry is found on dry sand plains, and in
Wisconsin it grows in bracken fern (Pteridium aquilinum)-grasslands
[18,25].  In Ohio it grows on the beaches and dunes along Lake Erie
[15].  In Ontario, it frequently grows on the shores of lakes and rivers
and in semiopen coniferous woods [127].  In New England it grows in dry
sandy open woods [125].  Bearberry is one of the most abundant low
understory species in the fire-prone, pygmy pine forests of the New
Jersey Pine Barrens [91].

Habitat variation by form:  Collections of North American bearberry
plants exhibit form differences between sites.  In the Rocky Mountains
these ecological differences between forms are less pronounced
[116,117].  Forma coactilis grows best on the driest sites and is
generally more common on acidic and drier substrates.  It is the only
form found along the Coasts (pH of most sites <6.6) and on the
relatively moist substrates of the Appalachian Mountains (pH of most
sites 3.7-5.5).  Forma coactilis grows most frequently in full sunlight
and is relatively uncommon on shaded sites [116,117].  Forma adenotricha
is most common on basic substrates and seldom occurs on very acidic
soils.  It seems to grow better on relatively moist sites.  In the Great
Lakes area, it is the most shade-tolerant form [116,117].  Forma
stipitata is more frequent on relatively basic sites; forma longpilosa
grows well on acidic soils.  Both grow well on sites with intermediate
moisture status.  Forma stipitata is most common on open sites in the
Rocky Mountains; forma longipilosa grows in intermediate light
conditions [116,117].

Soils:  Bearberry grows on a wide range of soil textures, although it is
commonly found on well-drained soils that have relatively low amounts of
clay and silt [8,76,142,147,148].  It frequently occurs on sandy soils,
shallow soils, soils on rock outcrops, and rapidly drained
coarse-skeletal soils [70,127].  Along both Coasts and in conifer
forests, bearberry occurs on dry, acidic substrates [117].  In the
Appalachian Mountains, it usually grows on moist, acidic soils.  The
sandy to rocky soils on which bearberry grows in the Great Lakes region
are neutral to basic [117].  In Colorado, Montana, North Dakota, Utah,
and Wyoming, bearberry growth is fair to good on acidic soils; poor to
fair on organic soils and poor on saline, sodic and sodic-saline soils.
Optimum soil depth in this area is 10 to 20 inches (25.4-50.8 cm) [30].

In the subalpine zone of western Montana, bearberry grows on soils
derived from granite and quartzite parent materials but not on soils
developed on limestone [48].  However, it grows on soils formed from
calcareous parent materials in the alpine zone [10].  It is found on
basaltic lava flows, mudflow deposits, serpentine outcrops, and coarse
glacial outwash in the Pacific Northwest [42].

Bearberry is common on dry, nutrient-poor soils [8,76,148].  Information
relating bearberry growth habits to specific soil nutrient levels is
available for British Columbia [147].  Results of one study indicate
that leaves are retained longer on plants growing on a sandy,
nutrient-poor substrate than on plants growing on a site with better
nutrient availability [111].

Elevation:  Elevational ranges in some western regions are
[20,30,142,150]:

                     Minimum                   Maximum
                   feet      meters         feet      meters

Alberta             500       150            2000      610
Colorado           6000      1829           11700     3566
Montana            2900       884            7700     2347
New Mexico         5000      1524           10000     3048
Utah               7021      2140           11516     3510
Wyoming            4000      1219            9700     2957


SUCCESSIONAL STATUS : 
Bearberry is a seral, shade-intolerant species often found in seral,
open pine forests [47,69,96,113,114,148].  It grows best in high light
situations and becomes very rare when shade becomes intense [8,41,123].
In the open, bearberry forms a compact and intricate mat; under a
canopy, long, thin trailing stems creep along the forest floor. Shoots
are more upright under partial shade than in the open [111].  Pubescence
of cuttings from the same plant may vary with light intensity and
substrate [117].  Results of a Rocky Mountain study of postdisturbance
vegetation cover indicate that the primary variables governing early
seral bearberry cover are overtopping cover of other shrubs and site
variables such as elevation [78].

Bearberry pioneers on dry rock outcrops in the Pacific Northwest [42].
It is an integral part of succession on dry, stable, sand dunes in the
Great Lakes and along both the Atlantic and Pacific coasts [34,42].  On
Lake Michigan sand dunes, it invades bunchgrass communities and thrives
under slow burial by drifting sand that covers part of the plant [103].
On drier sites in Yukon Territory and the Alaskan taiga, bearberry is
part of secondary succession in communities with aspen and willows
(Salix spp.)  [56,140].  Bearberry enters seral communities on glacial
outwash in the pioneer stage, reaches its highest cover early in the
meadow stage, and continues declining in the early shrub stage [139].
Bearberry succeeds lichens in northern Manitoba when the lichens are
damaged by caribou use [93].


SEASONAL DEVELOPMENT : 
Fruit dispersal in eastern deciduous forests occurs between August and
March [134].  In California, flowering primarily occurs between March
and May, fruit ripening between June and August, and seed dispersal from
August to March [11].  In Ontario, bloom is in May and June, and fruit
is ripe by August or September [127].  In the northern Great Plains,
flowering is in June, and fruit develops by September [132].  In New
England, flowering is from May 1 to June 10 [125].  Virginia and
disjunct Georgia populations bloom in May and June [152].  In the Black
Hills of South Dakota, growth begins in May and ends in September, but
over half the season's total growth occurs during June [123].
Phenological observations of bearberry made over an 8-year period east
of the Continental Divide in Montana and in Yellowstone National Park
are summarized below [121]:

                            Earliest        Average          Latest
                              Date            Date            Date
Leaf buds burst                May 27          June  6         June 22
Leaves full grown             July 21        August  2       August 15
Flowers start                  May 15           May 30         June 20
Flowers end                    May 31          June 11         June 30
Fruits ripe                    May 25        August 23    September 25
Seed fall starts (2 
  observations)                October 16       October 16      October 16

Related categories for Species: Arctostaphylos uva-ursi | Bearberry