BOTANICAL AND ECOLOGICAL CHARACTERISTICS
SPECIES: Acer circinatum | Vine Maple 



GENERAL BOTANICAL CHARACTERISTICS : 
Vine maple is a long-lived, shade-tolerant, deciduous shrub or small
tree which shows a high degree of variation in growth form.  Stems may
be erect or vertical, leaning, arched or convex with branch tips
anchored by roots, or prostrate with the end of the stem turned upwards
[2].  When found in the open this maple often grows as a dense shrub or
small tree with numerous erect stems.  Under favorable conditions plants
in these open habitats occasionally grow up to 30 feet (9.1 m) tall with
8- to 12-inch diameter (20-30 cm) trunks [31,51,61].  Plants shaded by a
coniferous overstory, however, commonly have prostrate stems that root
where a stem touches the ground.  A study conducted on the west slope of
the Cascades in central Oregon found that vine maple growing in 7- to
22-year-old clearcuts averaged 34 76-inch (195 cm) erect stems per plant
[51].  Nearby plants growing under mature conifers were much less erect
and averaged only three stems per plant, which were only 60 percent
longer than stems of plants in clearcuts.

The bark of vine maple is thin, smooth, and bright reddish brown [20].
The leaves are round to cordate, palmately seven- to nine-lobed,
serrate, and 1.2 to 2.4 inches (3-6 cm) long [19].  The fruit is a
rose-colored double samara.  The 0.5- to 1-inch-long (1.2-2.5 cm) wings
are widely divergent in a nearly straight line.


RAUNKIAER LIFE FORM : 
   Undisturbed State:  Phanerophyte (microphanerophyte)
   Undisturbed State:  Phanerophyte (nanophanerophyte)
   Undisturbed State:  Hemicryptophyte
   Burned or Clipped State:  Hemicryptophyte


REGENERATION PROCESSES : 
Vine maple is a very poor seed producer and relies primarily on
vegetative means of reproduction [2].

Vegetative regeneration:  Plants sprout from the root crown following
top-kill from logging or burning.  Vine maple distribution in early
seral communities is therefore primarily dependent upon its
predistubance distribution [6].  In early seral stands, layering occurs
infrequently, but as plants mature some stems become too long and
massive to remain erect and thus lay prostrate and root where the stem
touches the ground [51].  Therefore layering probably increases with
stand age.  Studies in western Oregon indicate that vine maple
reproduces almost exclusively by layering when under stands of old
growth conifers [2,51].  In these studies, new plants originating from
seed were extremely rare or absent from both clearcuts and mature
stands.  Sprouts may also arise from shallow lateral roots that have
become exposed to light [2].

Seed production and dispersal:  Vine maple begins to produce seed at an
early age, probably before age 10 [49].  The flowers appear in the
spring when the leaves are about half grown [31].  Flowers occur in
loose drooping clusters that hang from the end of the branchlets.  Male
and female organs occur in the same flower; however, in each flower only
male or female organs are functional.  Thus only a few flowers from each
cluster develop into fruit [31].  The fruit consists of two fused
samaras which eventually separate on shedding.  Each samara contains a
single seed without endosperm.  Small quantities of seed are produced
annually.  The winged seeds are dispersed in the fall by wind; however,
dissemination of samaras in mature stands is probably restricted, since
strong winds normally do not prevail in coniferous understories [2].
Seeds average approximately 5,000 per pound (11,000/kg) [49,62].

Seed viability and germination:  Vine maple seeds have a dormant embryo
which requires approximately 6 months of chilling to germinate [11].
Under natural conditions the seeds are dispersed in the fall and
germinate in the spring.  Studies have shown that vine maple seedlings
are rare or absent from both clearcuts and mature stands [2,51].  This
lack of seedlings may possibly be attributed to: (1) the consumption of
a high proportion of samaras by squirrels, chipmunks, and insects, (2) a
thick moss layer or dense growth of other shrubs which often prevents
seeds from reaching mineral soil, and (3) poor germination [2].


SITE CHARACTERISTICS : 
Vine maple is typically found as an understory shrub or small tree that
grows in moist forestsc composed of Douglas-fir, western hemlock,
western redcedar, Sitka spruce, Port Orford-cedar, or Pacific silver fir
[1,3,4,18,24,67].  It is also common along streambanks and alluvial
terraces, in forest openings and clearcuts, and on talus slopes and the
lower portions of open slopes [18,22,31,52].

Soils:  Vine maple is an indicator of well-drained, moist soils.  Soils
are deep, often exceeding 40 inches (100 cm).  Textures vary from clay
loams to sandy or rocky [15,25,26].

Overstory relationship:  Although this maple grows under dense shade and
has been classified by some authors as shade tolerant [3,37,61], many
researchers have found that both cover and frequency of vine maple are
much lower under dense conifer overstories than under more open
overstories [5,24,51].  Vine maple is more abundant under Douglas-fir
than under western hemlock or western redcedar [2,61].  This may be
attributed to the greater amount of light which typically penetrates
through Douglas-fir canopies compared to hemlock [2] or possibly to
alleleopathic chemicals produced by western hemlock which inhibit the
growth of vine maple [12].

Associated species:  Associated shrubs include red elderberry (Sambucus
racemosa), Sitka alder, oceanspray (Holodiscus discolor), California
hazel (Corylus cornuta), Oregon-grape (Berberis nervosa), salal
(Gaultheria shallon), Pacific rhodendron (Rhododendron macrophyllum),
trailing blackberry (Rubus ursinus), twinflower (Linnaea borealis),
Alaska huckleberry (Vaccinium alaskaense), blue huckleberry (V.
membranaceum), and baldhip rose (Rosa gymnocarpa).  Associated herbs
include western swordfern, coolwort foamflower, beargrass (Xerophyllum
tenax), waterleaf (Hydrophyllum spp.), baneberry (Actaea rubra), and
common whipplea (Whipplea modesta) [1,2,4,15,24,25].

Elevation:  Vine maple is a low elevation species found mostly below
3,000 feet (914 m) in Washington and northwestern Oregon, and below
5,500 feet (1,676 m) in southwestern Oregon and California [3,67].


SUCCESSIONAL STATUS : 
Vine maple is found in both seral and climax stages of forest
succession, but cover and frequency are highest in early seral stages.
Since this maple is a root-sprouter, its distribution following
clearcutting or fire closely resembles its distribution in climax
forests [5,6].  Cover of vine maple through different seral stages
fluctuates with changes in the overstory.  Cover seems to be inversely
proportional to overstory density.  A western Oregon study found that
cover of vine maple under dense old-growth Douglas-fir was about 5
percent, but about 24 percent in light spots [5].

In western redcedar-western hemlock-Douglas-fir forests, vine maple
cover may be initially reduced following logging [13,14,54] but then
gradually increases for the next 25 to 30 years.  At this time vine
maple cover decreases, due to shading from a young conifer overstory,
but vine maple cover will again increase as succession proceeds if
conifer mortality creates light spots in the understory [5,30,51,54].

Successional studies of coniferous forests in the Pacific Northwest show
that following fire or logging, herbaceous cover usually dominates for
the first few years [18].  Within 4 or 5 years dense shrub communities
normally develop.  These are often composed of residual shrubs, such as
vine maple, trailing blackberry, salal, Pacific rhodendron, and
Oregon-grape [18].


SEASONAL DEVELOPMENT : 
Flowering normally occurs from April through June, when the leaves are
about half grown [25,49,52].  The fruits generally ripen in September or
October, after which seed is dispersed through November [49].  Before
the leaves are shed in autumn, they turn various shades of yellow or
red.  Observation of leaf fall in two western Oregon watersheds showed
that vine maple leaves began falling in early September and peaked the
third week in October [10].  On one watershed, 94 percent of leaves fell
within 3 weeks after the first frost [10].

Related categories for Species: Acer circinatum | Vine Maple