BOTANICAL AND ECOLOGICAL CHARACTERISTICS
SPECIES: Acer saccharinum | Silver Maple 



GENERAL BOTANICAL CHARACTERISTICS : 
Silver maple is a native, deciduous, medium-sized tree.  Mature height
ranges from 90 to 120 feet (27-36 m).  Silver maple is characterized as
a fast growing species [16].  The trunk is often separated into several
upright branches near the ground [50].  The crown is usually open and
rounded [20].  The bark of young stems is smooth; it becomes darker and
furrowed to flaky on older stems [10].  The root system is shallow and
fibrous [16].  The deepest roots of 35-year-old silver maples planted on
clay soil in North Dakota were 55 inches (139.7 cm).  The longest roots
extended horizontally 49 feet (14.9 m) [68].  The fruit is a winged
samara, 1.4 to 1.9 inch (3.5-5 cm) long and up to 0.48 inch (12 mm) wide
[10].

Silver maples can live to 130 years or longer [16].  The national
champion silver maple (1972) was found in Michigan.  It was 125 feet
(38.1 m) tall, 22.58 feet (82.6 m) in circumference, and had a crown
spread of 111 feet (33.8 m) [20].


RAUNKIAER LIFE FORM : 
   Phanerophyte


REGENERATION PROCESSES : 
The mimimum seed bearing age for silver maple is 11 years.  Large seed
crops are produced annually [46].  The fruits are primarily wind
dispersed, with a minor amount of water disperal [16].  Release of
fruits is dependent on relatively high wind speeds, ensuring long
distance dispersal [23].  The seeds germinate immediately upon dispersal
[10].  Natural regeneration is most successful on moist mineral soil
with considerable organic matter [16].  Silver maple seed also
germinates well on moist litter.  Seedling establishment requires full
sun, but subsequent growth is best with partial shade [44].  Seedlings
are often stunted in saturated soils, but can recover when soil moisture
drops [16].  In Wisconsin, silver maple seedlings were found with higher
frequency in the spring than in the fall [36].

Silver maple can be propagated from cuttings and bud grafts, and by
layering.  It sprouts prolifically from the stump or root crown.  The
best sprouting occurs from stumps less than 12 inches (30 cm) in
diameter.  Larger trees tend to lose the ability to sprout [16,74].


SITE CHARACTERISTICS : 
Silver maple is typical of wet bottomlands, riverbanks, and lake edges.
It is less common on upland sites [10].  In Illinois, silver maple was
reported only from bottonland wet-mesic sites; it did not occur on drier
sites of even slightly higher elevation [60].  In New York, silver maple
occurs on limestone, outwash, and alluvial soils [34].  Best growth is
on moist, well-drained, fine-textured alluvial soil [16,40,44].  Silver
maple is found from 100 feet (30.5 m) to 1,600 feet (488 m) elevation in
the Adirondacks [34], and is uncommon above 1,980 feet (600 m) elevation
in the Appalachians [14].  In drier areas silver maple is only found
along streams [10].

Silver maple is usually found on soils with pH above 4.0, but has been
reported from muck and shallow peat soils with a pH from 2.0 to 3.3
[16].  Recommended soil pH range is 4.5 to 7.0 [72].  Forest floor
biomass under silver maple plantations had an average pH of 3.7 after 27
years of growth; the underlying mineral soils averaged pH 6.3.  The
effect appeared to be due to a decrease in buffering capacity [15].

Silver maple is intermediate in tolerance to water-saturated soils, but
can tolerate prolonged periods of inundation [16].  It is a member of
some greentree reservoir systems that are flooded during the dormant
season to provide waterfowl habitat and drained before the onset of the
growing season.  These sites usually have saturated soils most of the
growing season [61].  Silver maple seedlings survived 60 days of
continuously saturated soils [25], but seedlings of low vigor died after
only 2 days of complete inundation [24].  In the upper Mississippi River
valley, silver maple trees died after 2 years of constant inundation
(due to reservoir formation) [22].

In the northeastern United States, silver maple is a dominant or
codominant species on the following types of sites: 1) undifferentiated
alluvial deposits of poorly drained silts high in organic matter and
nitrogen, 2) undifferentiated alluvium composed of well-drained silts
with a high base content and nearly neutral soils, and 3) rapidly
aggrading alluvial areas and point bars composed of mixtures of sand and
silt that are of intermediate fertility [43].

Silver maple was consistently dominant in a model of riparian forest
stands under conditions of 4,000 growing degree days, even when other
model parameters were varied.  This is consistent with the natural
distribution of silver maple; it decreases in dominance with decreasing
latitude and increasingly warmer conditions [38].


SUCCESSIONAL STATUS : 
Facultative Seral Species

The shade tolerance of silver maple is not well defined.  It ranges from
moderately tolerant to very intolerant of shade, depending on site
quality and location.  Silver maple tends to be more shade tolerant on
good sites and less tolerant on poor sites [16].

Silver maple is a dominant species in elm-ash-cottonwood forest types
which are pioneer to intermediate in succession.  These forests cannot
be maintained without management or natural disturbance [44].  The
silver maple-American elm type is usually a subclimax type, following
willows and eastern cottonwood.  The type is described as climax for
southern Ontario, where it regenerates in willow and red-osier dogwood
thickets [73].

Silver maple is one of a number of species that follow eastern
cottonwood to form a mixed hardwood bottomland community.  It is
described as an early, fast-growing species [32].  In a northern
Missouri floodplain community, in plots where silver maple was the most
important overstory species, there were many large silver maples in the
understory.  Silver maple will probably remain the canopy dominant for
some time since there are also large old eastern cottonwoods present,
which, when they die, will create openings large enough for silver maple
seedling establishment.  Similarly, the presence of American elms will
allow new silver maple establishment if they succumb to Dutch elm
disease (as is likely) [12].  Numerous silver maple seedlings and
saplings were present in a silver maple dominated forest on the Wabash
River in Illinois and Indiana, which should ensure the continued
dominance of silver maple on this site for some time [49].

Silver maple is typically found in riparian forests which are more or
less frequently disturbed by floods [20].  It is also found both on
sites that have been disturbed by stream channelization projects [29].
It forms stands at low elevations where new alluvium has been deposited
and will colonize bottomland clearings and adjacent slopes [4,20].
Silver maple was present on 28-year-old and 40-year-old abandoned
agricultural clearings in western Tennessee [57].  It invades sedge
(Carex spp.)  meadows in northern Wisconsin [52] and southern Quebec
[2].  Silver maple invades cutover areas when seed sources are present
[40].

Silver maple was a member of a plant community that established on a
small, frequently flooded island in Wisconsin.  On this island, silver
maple was quite common and there was a relatively large number of silver
maple seedlings.  Most of the large silver maple stems were of sprout
origin, and overall mortality rate for silver maple was lower than that
for most other species.  Apparently, flood damage breaks off aboveground
portions of silver maple.  The remaining stems sprout vigorously and may
therefore increase in number after such damage.  The largest stems of
all species were found on the downstream end of the island, where they
experienced less destructive disturbance [3].

A silver maple-green ash forest was reported to a National Park Service
survey as old growth.  This forest covers 7.5 to 10 acres (3-4 ha) on
Theodore Roosevelt Island in Washington D.C.  Approximate tree ages
range from 160 to 198 years [62].


SEASONAL DEVELOPMENT : 
Silver maple is one of the earliest flowering species within its range;
flowering occurs over a short period from late February to April or May,
depending on latitude [10,16].  All flowers on one individual are within
a day or so of each other in development; the period of pollen
receptivity lasts from a few days to a week [67].  The flowers often
fall before the leaves are fully grown [19].  The seeds ripen and are
released over a very short period, usually less than 2 weeks [23] from
April to June.  Germination usually occurs shortly after dispersal [10].

Related categories for Species: Acer saccharinum | Silver Maple