BOTANICAL AND ECOLOGICAL CHARACTERISTICS
SPECIES: Picea abies | Norway Spruce 



GENERAL BOTANICAL CHARACTERISTICS : 
Norway spruce is an introduced evergreen tree.  In central Europe,
heights of up to 203 feet (61 m) have been reported [42]; the range is
usually between 100 and 200 feet (30-61 m) [87].  The bole is usually
straight and symmetrical, with no tendency to fork [42].  The bark of
young trees has pale fine shreds [50].  The bark of older trees is
usually heavy with algae and has shallow rounded scales that are easily
shed [17,50].  The crown of young trees is narrowly conic, that of older
trees becoming broadly columnar [50].  Secondary branchlets are
characteristically drooping or pendulous [2].  Norway spruce cones are
conspicuously large (4 to 7 inches [10-18 cm] long) [17].  The root
system is typically shallow, with several lateral roots and no taproot.
On rocky sites the roots spread widely, twining over the rocks.  On bog
soils, Norway spruce tends to form plate-like roots [42].  In Finland, a
140-year-old Norway spruce forest in a Vaccinium-Myrtillus vegetation
type had a root zone extending only 12 inches (30 cm) into mineral soil [43].

Early growth of Norway spruce is slow, increasing to maximal rates from
20 to 60 years of age [42,50].  Within its native range, Norway spruce
remains healthy up to 200 years, and lives up to 300 to 400 years at the
northern limits of its range [42].  Senescence occurs at less than 200
years of age in the British Isles and North America [50].


RAUNKIAER LIFE FORM : 
   Phanerophyte


REGENERATION PROCESSES : 
Sexual reproduction:  Norway spruce usually first reproduces at 30 to 40
years of age.  Good seed crops are produced every 3 to 4 years in
Britain, 8 to 10 years in Norway, and 12 to 13 years in Finland [42,87].
Most of the seeds are produced in the crowns of dominant stems; seed
yield is lower in smaller stems in stands of the same age.  Norway
spruce seeds are wind dispersed, but do not usually travel much farther
than the height of the parent tree [42].  Movement after dispersal,
however, can be considerable when seeds are dispersed onto crusted snow
and are pushed along on the surface by wind [34,74].  Seeds of Norway
spruce germinate promptly and do not require pretreatment or exacting
light regimes.  Moist chilling of some spruce (Picea spp.) seeds removes
the requirement for light [87].  Optimum germination temperature for
Norway spruce seeds is around 73 degrees Fahrenheit (23 deg C) but
germination will occur up to about 91 degrees Fahrenheit (33 deg C)
[42].  Seedling growth is best at constant low temperature (48 degrees
Fahrenheit [9 deg C]), rather than with fluctuating temperatures or
steady high temperatures [36].  The seedlings are sensitive to drought
and/or overheating, particularly when the soil surface is exposed to
direct insolation [42].  In Utah, nursery-grown seedlings inclined to
the south (to shade the soil directly under the seedling and keep the
roots cooler and wetter) averaged 6 percent mortality from heat damage,
whereas seedlings inclined to the north averaged 30 percent mortality
from the same cause [41].  Other studies support the hypothesis that
shading improves early seedling survival [33,77].  Thin humus (as
opposed to thick humus) hinders Norway spruce establishment since it
dries out more quickly and contributes to drought stress of the
seedlings [70].

Vegetative reproduction:  Under natural conditions, particularly in
areas of high humidity and high soil moisture, Norway spruce reproduces
by layering [42].  It does not sprout from stumps or roots [65].

Norway spruce can be propagated by cuttings and micropropagation
techniques [30].


SITE CHARACTERISTICS : 
Norway spruce grows best in cool, humid climates on rich soils [2,17].
Preferred soils include well-drained sandy loams [2,17,42].  It also
grows well on almost all other types of soils.  Permanently waterlogged
soils inhibit Norway spruce growth, but Norway spruce does occur on
poorly drained soils and in bogs [42].  Growth rates increase with
increased soil organic material and are positively correlated to the
nitrogen content of the soil.  In southern Finland, soil pH under 34- to
38-year-old plantations of Norway spruce ranged from 3.7 to 4.4.  Norway
spruce is also found on podzolized soils [45].

Norway spruce occurs at elevations up to 6,560 feet (2,000 m) in the
Bavarian Alps, to 4,920 feet (1,500 m) in the Black Forest, and to 3,450
feet (1,051 m) in the Fichtel Mountains [42].  In Switzerland, the
'hilly zone' up to 1,800 feet (550 m) is occupied by mixed hardwoods
with scattered conifers (European silver fir, Norway spruce and Scot's
pine); the 'mountain zone' from 1,800 feet to 3,800 feet (550-1,160 m)
is cooler and more humid and is dominated by European beech, European
silver fir and increasing amounts of Norway spruce; the subalpine zone
from 3,800 feet to 6,600 feet (1,160-2,000 m) is divided into two
subzones:  'subalpine spruce' up to 5,500 feet (1,670 m) consisting of
pure Norway spruce and mixed Norway spruce and European silver fir; and
the 'Arolla pine (Swiss stone pine [Pinus cembra])- (European) larch
(Larix decidua) zone' from 5,500 feet (1,670 m) to timberline [24].
This distribution is generally applicable to most of central Europe [42].


SUCCESSIONAL STATUS : 
Obligate Climax Species

Norway spruce is tolerant of shade.  Norway spruce stands form the
climax forest of Scandinavia but stagnate with age [79].  Seeds of
Norway spruce are probably not long lived in the soil, although under
good storage conditions remain viable for up to 7 years [87].  The soil
seedbank under a 100-year-old Norway spruce forest in Russia contained a
large number of viable seeds of mostly early successional species.  It
was not representative of the aboveground flora and apparently did not
contain many Norway spruce seeds [38].

Disturbance events such as windfalls, snow damage, disease and insect
attack create small-scale gaps in the mature canopy.  Norway spruce
depends largely on advance regeneration (seedling banks) to capture such
canopy gaps [56].  Norway spruce is the most common gapmaker and it is
also the most common seedling in gaps.  Seedlings survive in an
extremely stunted condition for many years.  This reservoir of seedlings
functions in a way analogous to soil seedbanks [29].  Suppressed Norway
spruce saplings can persist for several decades, retaining the ability
to respond to canopy gaps with increased growth [35].  In Sweden,
suppressed Norway spruce trees less than 8.2 feet (2.5 m) tall and 100
to 220 years old exhibited new growth during gap-phase replacement [70].
In Bavarian Norway spruce stands, storm-caused windfall disturbances
were followed by new Norway spruce stands that were older than than the
windfall event (indicating advance regeneration).  Sites that had been
cleaned (removal of dead trees and broken stems) had a birch-dominated
regeneration layer that originated after the windfall event.  Spruce
seedlings were probably damaged by the cleaning operation [23].  In
northern Sweden, Norway spruce-hairy birch forests consist of all-aged
(up to 330 years) Norway spruce (largely as a result of gap-capture
replacement) [35].
  
Norway spruce first occurred in Scandinavia approximately 2,500 years
ago; its immigration from Europe is attributed to colder Scandinavian
winters coupled with increased precipitation and storm events which
allowed Norway spruce to colonize areas that were formerly too dry [7].
It survived in Scandinavia in low densities due to frequent disturbances
until climatic changes coupled with a decrease in human-caused
disturbances (mainly fire) allowed natural succession to proceed,
resulting in the current widespread distribution of dense Norway
spruce-dominated forests [8].


SEASONAL DEVELOPMENT : 
Norway spruce cones open from May to June.  Seeds ripen in late autumn
the same year.  They are released on warm days in late autumn and
winter, but are sometimes retained until spring [42].

Related categories for Species: Picea abies | Norway Spruce