BOTANICAL AND ECOLOGICAL CHARACTERISTICS
SPECIES: Picea rubens | Red Spruce 



GENERAL BOTANICAL CHARACTERISTICS : 
Red spruce is a native, evergreen conifer.  It is a medium-sized tree,
attaining a maximum height of 115 feet (35 m); the average mature height
is 60 to 75 feet (18-23 m).  The ovulate cones are 1.3 to 1.5 inches
(3-4 cm) long, with rigid rounded scales that are often slightly toothed
on the edges.  Red spruce is very shallow rooted; most of the feeding
roots occur in the duff and top few centimeters of soil.  In Maine, the
average depth of roots was 13 inches (33 cm), with a maximum depth of 22
inches (56 cm) [9].  Red spruce is long-lived, often achieving ages
greater than 350 years [1].


RAUNKIAER LIFE FORM : 
   Phanerophyte


REGENERATION PROCESSES : 
Red spruce reproduces exclusively by seed.  The first cone crop is
usually produced when the crown first reaches direct light [27,39].
Therefore, red spruce can bear cones as early as 15 to 20 years of age;
cone production peaks about 15 years later.  In dense, even-aged stands,
full cone crops are rare until the trees are 40 to 50 years old [39].
Good seed crops are produced every 3 to 8 years, with light crops in
intervening years.  Cones are dropped shortly after they are mature [9].
The seeds are wind or rain disseminated.  The maximuim distance for
dispersal by wind is approximately 201 feet (61 m) [27].  Seeds do not
exhibit dormancy.  Most germinate the spring following dispersal;
occasionally germination will occur in the fall soon after seeds drop
from the tree.  Seeds are usually not viable after 1 year.  Germination
is largely controlled by moisture availability.  Seeds will germinate in
almost any medium except sod.  Seeds that germinate in thick duff are
subject to overheating and/or drought mortality.  Drought and
frost-heave are the major causes of seedling mortality the first year
[9].

Successful reproduction appears to depend more on seedling survival than
on germination requirements [9].  Seedling establishment is usually best
on shallow, less fertile soils that discourage competitive hardwoods
[87].  The primary roots of red spruce seedlings do not penetrate litter
and forest duff to any depth [38].  Red spruce seedlings have a root
system of finely branched rootlets and no strong laterals; they depend
entirely on the humus for nutrients and water [57].


SITE CHARACTERISTICS : 
Red spruce grows in climates with cool, moist summers and cold winters
[74].  In the northeastern United States, the mean annual precipitation
ranges from 36 to 52 inches (910-1,320 mm) and is often higher in the
mountainous terrain where red spruce occurs, due to fog drip.  Snow
cover averages 80 to 160 inches (203-406 cm), with 100 to 140 days of
snow cover per year [9].

Most of the soils on which red spruce occurs are developed from glacial
deposits.  The most productive soils are derived from parent materials
of unsorted glacial drift and till deposited on the midslopes of hills
and mountains.  Soils on red spruce sites are usually acid Spodosols,
Inceptisols, and sometimes Histosols with thick mor humus and a
well-defined A2 horizon.  Soil pH ranges from 4.0 to 5.5.  Red spruce is
often found on sites that are unfavorable for other species, such as
organic soils overlying rocks in mountainous locales, on steep rocky
slopes with thin soils, and in wet bottomlands [9].

In the northern part of its range, red spruce occurs at elevations
ranging from sea level to 4,500 feet (0-1,370 m), above which it is
usually replaced by balsam fir (Abies balsamea).  The elevational
zonation of species is defined as follows [67]:

  up to  1,485 feet         (450 m)    northern hardwoods (hemlock phase)
1,486 to 2,508 feet   (451-  760 m)    northern hardwoods (spruce phase)
2,508 to 4,026 feet   (761-1,220 m)    subalpine  (spruce-fir phase)
4,027 to 4,785 feet (1,221-1,450 m)    subalpine  (fir phase)

In the southern Appalachian Mountains, red spruce occurs at elevations
from about 3,200 feet to 6,200 feet (980-1,890 m); above 6,200 feet
(1,890 m), red spruce tends is usually replaced by Fraser fir (Abies
fraseri) [59].


SUCCESSIONAL STATUS : 
Facultative Seral Species

On shallow, acidic, glacial till soils, red spruce is considered climax.
It is usually subclimax on fertile, well-drained slopes and on abandoned
fields and pastures where is is replaced by shade-tolerant hardwoods
such as sugar maple and beech.  Other types, such as red spruce-balsam
fir and red spruce-yellow birch are usually climax [20].

Red spruce is tolerant of shade.  Seedlings of red spruce can establish
in as little as 10 percent of full sunlight, but for optimum growth, at
least 50 percent of full sunlight is needed [9,75,81].  Growth tends to
be suppressed in shade, but such suppression can persist for many years
without killing the tree.  For example, suppressed understory
individuals may be 4 to 5 feet (1.2-1.5 m) tall, and be more than 50
years old.  In comparison, open-grown red spruce can reach sawtimber
size at 50 years [9,29].

Red spruce responds to canopy removal even after many years of
suppression.  The taller and older a seedling or sapling is, the greater
is its response to release, up to about 55 years of age after which
response to release starts to decline.  However, the amount of response
does not revert to seedling levels until the tree is around 100 years of
age.  Umbrella-shaped saplings 40 to 80 years old that have been
suppressed will respond to release after a delay of several years, and
in fact have an advantage because they are taller than smaller,
healthier saplings which respond more quickly to canopy opening.  More
than half of mature red spruce second growth arises from larger but
suppressed advance growth, as opposed to having arisen from small
advance growth or new seedlings [16].  Upon release, 60-year-old red
spruce growth exceeds that of same-age balsam fir and therefore tends to
dominate the canopy [56].

Leak [44] defined red spruce in New Hampshire as a dominating climax
species on shallow, dry, wet, or poorly areated soils; it is a minor
component in young stands but increases markedly over time until it is a
canopy dominant.  He estimated that, if undisturbed, red spruce can
reach densities of 70 to 80 percent in a minimum of 250 years.  Red
spruce is a long-lived species and, once established, persists as a
dominant for a long time.

Davis [16] observed young spruce-fir stands in coastal Maine originating
in open sites and as the understory to early seral hardwoods such as
paper birch.  The young, open-grown stands may be dominated by white
spruce, red spruce, or balsam fir in any proportions.  A spruce-fir
stand originating as understory tends to be dominated by red spruce
and/or balsam fir, though white spruce is often present.  Moore [58]
found red spruce forests to be even-aged in groups, indicating that
establishment and/or canopy achievement tends to occur in openings.

Red spruce and red spruce-fir cover types are self-maintaining.  Stand
composition may vary with stand age.  Both red spruce and its two fir
associates (balsam and Fraser) are shade tolerant, and both spruce and
fir reproduction are found under spruce-fir canopies [6,16].  In the
Catskill Mountains of New York, balsam fir reproduction predominated
under both spruce and balsam fir stands.  Both red spruce and balsam fir
reproduction occurred at low densities under hardwood stands (mostly
yellow birch) [55].  McIntosh and Hurley [55] do not believe that red
spruce forests form a self-perpetuating climax in this area.  Their
conclusion may be biased, however, since balsam fir outcompetes red
spruce in early stages, but is usually overtopped or outcompeted by red
spruce in more mature forests [16].  Flieger [21] described 350-year-old
stands of red spruce which were characterized by irregular stocking and
variable crown heights and widths, with at least two age classes
apparent.  Most virgin red spruce forests are uneven-aged, indicating
that the forests did no originate following stand-destroying
disturbances, and that red spruce is able to reproduce under its own
canopy [52].


SEASONAL DEVELOPMENT : 
Red spruce vegetative buds begin growth from May 26 to June 3 [8].
Needles are shed early in summer [12].  Reproductive cones open in late
April to early May [29,72].  Red spruce cones mature the first autumn
from mid-September to mid-October [29,39].  Dissemination of seeds
begins soon after cones are ripe and continues until March [29].

Related categories for Species: Picea rubens | Red Spruce