BOTANICAL AND ECOLOGICAL CHARACTERISTICS
SPECIES: Alnus rugosa | Speckled Alder 



GENERAL BOTANICAL CHARACTERISTICS : 
Speckled alder, alternately described as a small tree and a large shrub
[23,27], is a locally common, deciduous, thicket-forming, woody plant.
It can grow as tall as 20 to 30 feet (6.1-9.2 m) with a 6-inch (15 cm)
diameter stem, although most specimens are not this large [56].
 
Speckled alder bark is thin and smooth and conspicuously marked with
orange lenticils, hence the name [27,38].  Leaves are 2 to 4 inches long
(5-10 cm).

Speckled alders are monoecious.  The inflorescence is cymose and open.
Staminate catkins are 1.6 to 3.5 inches (4-9 cm) long.  Pistillate
catkins are sessile, cylindric, and 0.16 inch (5-6 mm) long [27,52].

The fruit of the speckled alder is an oval, 0.63 by 0.31 inch (16 by 8
mm), winged nutlet borne in egg-shaped conelets [25,27,52].  Twigs are
moderately slender.  Buds contain two or three bud scales.



RAUNKIAER LIFE FORM : 
   Undisturbed State:  Phanerophyte (Microphanerophyte)
   Burned or Clipped state:  Chamaephyte
   Burned or Clipped state:  Hemicryptophyte


REGENERATION PROCESSES : 
Sexual reproduction:  Speckled alders are wind pollinated.  The winged
seeds ripen during late August and September and are dispersed by the
wind through April.  Little is known about seed-bearing age, seeds
produced per plant, or seed dispersal distances [25].  Germination
usually requires exposed mineral soil [30,62], which may need to be
saturated [15].

Vegetative reproduction:  Vegetative reproduction, rather than seedling
recruitment, provides most of the new stems in established alder stands
[29].  Vegetative reproduction occurs primarily via sprouting; but also
through layers, suckers, and underground stems [16,25].  Sprouting is
independent of stem damage.  Burgason [9] noted an equal number of
sprouts from the underground stems of burned and unburned speckled
alder.  Speckled alder is clonal and may form impenetrable thickets.
With conifer competition, local distribution is more diffuse.  Release
after removal of overstory competition is immediate [58].  Isolated
clumps expand radially and coalesce [29].

Scarification and mild intensity burning encourage speckled alder
regeneration [2,61]. 



SITE CHARACTERISTICS : 
Speckled alder is a species of moist lowlands.  It frequently borders
streams and lakes.  It is common in swamps and the older zones of bogs
[15,60].  Throughout its range, speckled alder often dominates black
spruce, jack pine, tamarack, northern white-cedar, and birch-aspen
understories on nutient-rich, mesic sites [15,24,27,33,34,56,60].  Where
speckled alder's range overlaps that of its close relative, American
green alder (Alnus crispa), it tends to be found on lowland sites and
American green alder tends to be found on upland sites [3].

Soils:  Speckled alder adapts to a variety of soils provided they are
moist and nutient-rich.  In Wisconsin, speckled alder grows in mucky
soils, which are relatively shallow over glacial till or deep over
lacustrine peat [15].  It also grows in sandy loams, grey forest soils,
minerotropic peatlands, alluvial soils, and ericaceous bogs
[6,15,19,26,60].  Speckled alder has been described growing on both
poorly drained [15,25] and well-drained [15,27,56] sites.  Soil pH
varies between 4.8 and 7.7 [6,15].

Shade tolerance:  Although prevalent as an understory shrub, speckled
alder grows more vigorously in the full sunlight of forest openings and
sparsely stocked stands.  It shows rapid release upon removal of the
overstory and is decribed as shade intolerant to intermediately shade
intolerant [17,25,27,56,58].




SUCCESSIONAL STATUS : 
Speckled alder is an early seral species that quickly invades forest
openings created by fire and/or logging.  It is an early colonizer of
gaps in wetland forests [28].  Exposure of the mineral soil creates
optimal seedbeds and speeds speckled alder's invasion of a site
[21,25,57,62].  Historically, speckled alder may have been an early
colonizer of recently deglaciated areas in North America [15].

Although present at low densities in some stands, overstory removal can
trigger a rapid increase in speckled alder.  After logging black spruce
from nutrient-rich peatland, speckled alder may form nearly pure
thickets, outcompeting black spruce seedlings and effectively arresting
succession [7,31].  Speckled alder eventually gives way to conifers on
most sites [21].



SEASONAL DEVELOPMENT : 
Speckled alder is deciduous.  Flowers appear late in summer and become
functional the following May or April [25,42,49,52].  Fruit ripens from
late August through September [42,49].  The seeds are dispersed by wind
through the following April [42].

Related categories for Species: Alnus rugosa | Speckled Alder