Overview

Brief Summary

Picea abies, Norway or European spruce, is a large evergreen coniferous tree in the Pinaceae (pine family) native to montane and boreal European forests, ranging from the European Alps to the Balkan and Carpathian Mountains, and extending north into Scandinavia and northern Russia. It is the most important timber species in Central Europe. It was introduced into the British Isles in the 1500s and is naturalized throughout. It is the most widely cultivated spruce species in North America, often planted as an ornamental and landscape tree in parks and cemeteries for its graceful, drooping form; dozens of cultivars have been developed, including dwarf, shrub, and creeping forms. Norway spruce has escaped cultivation and naturalized throughout the northeastern U.S. and Canada, from Maine to Minnesota, from northern Quebec to southern Virginia and North Carolina, as well as in the Rocky Mountain and Pacific Northwest states.

Norway spruce grows to 35-55 m (115-180 ft) tall and with a trunk diameter of up to 1-1.5 m; it is fast-growing when young, and can grow up to 1 meter per year for 25 years. Leaves are needle-like, 1.2-2.4 cm (1/2 to 1 inch) long, quadrangular in cross-section (not flattened), and dark green on all four sides with inconspicuous white stomatal lines. Cones are 9-17 cm long (the longest of any spruce), and have bluntly to sharply triangular-pointed scale tips. There is extensive variation in characters across the range, with some botanists recognizing subspecies, along with hybridization with closely related species (see details below, in full entry).

Norway spruce is one of the most economically important coniferous species in Europe, where it is used in forestry for timber and timber products (such as glued laminated timber), and paper production, and is esteemed as a source of tonewood for musical instruments. It is also widely planted for use as a Christmas tree. A clonal clump (vegetative resprouts from a trunk of an initial stem that grew from seed but has since died back) of Norway spruce in the mountains in western Sweden is estimated to 9,550 years old—one of the world's oldest known living clones (as described in this Scientific American podcast).

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Comprehensive Description

Comments

The wood of Norway Spruce is used to make furniture, musical instruments (pianos & violins), pulp, and in general construction. It is light-colored, light-weight, rather soft, and reasonably strong. Norway Spruce has the longest seed cones of any spruce (Picea sp.) in Illinois; they exceed 4" in length, while the seed cones of other spruces within the state (which are largely cultivated) are less than 4" in length. Spruces resemble firs (Abies spp.), but their mature seed cones hang downward from their branches. In contrast, the mature seed cones of firs are erect. Spruces produce their leaves individually along their twigs and branches, while pines (Pinus spp.) produce their leaves in clusters (typically 2-5 leaves per cluster). Thus, spruces are fairly easy to distinguish from firs and pines. Like Norway Spruce, other spruces in Illinois are rarely observed in the wild. The coniferous trees in this group are more typical of boreal regions or mountainous areas where the climate is more cool and damp.

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Description

This coniferous tree is 50-120' tall, forming an unbranched straight bole and a crown that is conical to oblongoid in shape. Toward the base of a mature tree, the trunk is 1½-3' across. The trunk bark is gray and rough-textured, becoming scaly with age. Both crustose lichens and algae often colonize its bark. Numerous lateral branches originate along the entire length of the bole. These lateral branches are slightly incurved and ascending. Along the length of each lateral branch, there are several drooping branchlets that divide into divergently branched twigs. The bark of these branches and branchlets is slightly rough and gray, while the twigs are pale yellow to reddish brown. Along the smaller branches, branchlets, and twigs are short needle-like leaves about ½-1" long. These needle-like leaves are medium to dark green, 4-angular, and slightly flattened with blunt tips; they are stiff-textured and curve slightly toward the tips of each branch or twig. Along the sides of each leaf, there are pairs of faint white lines that are formed by rows of stomata (air pores). At the base of each leaf, there is a short peg-like extension of the twig from which the leaf breaks off when it turns brown from age. Individual leaves are evergreen, persisting on a tree for 3-7 years. They have a pine-like fragrance. Norway Spruce is monoecious, forming separate male and female cones on the same tree during mid- to late spring. Male pollen cones are produced from the axils of the needle-like leaves; they are ½-1" in length, oblongoid-ovoid in shape, and purplish red to whitish pink. Female seed cones are produced from the tips of twigs; they are initially pink to reddish pink and oblongoid-ovoid in shape, but change color and become longer after the blooming period. At this stage, both male and female cones are more or less erect. Afterwards, fertile seed cones become green and hang downward; they are covered with overlapping appressed scales. At maturity, these seed cones become brown to gray-brown and slightly woody from their thin scales; they are 4-7" in length and cylindrical in shape. Individual scales are about ¾-1" in length and ½-¾" across; they are obovate-rhombic in shape, glabrous, and irregularly toothed to toothless along their outer margins. Hidden behind each scale, is a pair of winged seeds (not always fully developed). Each seed body is 3-5 mm. in length, while its membranous wing is 10-15 mm. in length. The winged seeds are distributed by the wind. The root system consists of shallow lateral roots. This tree can reproduce vegetatively by "layering" when its lower branches become inserted in moist soil.

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Distribution

Range and Habitat in Illinois

The non-native Norway Spruce has naturalized only in the NW corner of Illinois in Jo Daviess County, where it is rare. It was introduced into North America from Europe, where it is native. In Illinois, this tree has naturalized in a woods (Mohlenbrock, 2002), where it is apparently successfully reproducing. Norway Spruce is far more common in cultivation, where it used as a landscape tree, a windbreak tree, and a plantation tree (for Christmas trees and other commercial markets).

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Norway spruce is native to the European Alps, the Balkan mountains, andthe Carpathians, its range extending north to Scandinavia and mergingwith Siberian spruce (Picea obovata) in northern Russia [50]. It wasintroduced to the British Isles as early as 1500 AD, and is widelyplanted in North America, particularly in the northeastern UnitedStates, southeastern Canada, the Pacific Coast states, and the RockyMountain states [47,50]. Naturalized populations are known fromConnecticut to Michigan and probably occur elsewhere [47].

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Physical Description

Morphology

Description

Norway spruce is an introduced evergreen tree. In central Europe,heights of up to 203 feet (61 m) have been reported [42]; the range isusually between 100 and 200 feet (30-61 m) [87]. The bole is usuallystraight and symmetrical, with no tendency to fork [42]. The bark ofyoung trees has pale fine shreds [50]. The bark of older trees isusually heavy with algae and has shallow rounded scales that are easilyshed [17,50]. The crown of young trees is narrowly conic, that of oldertrees becoming broadly columnar [50]. Secondary branchlets arecharacteristically drooping or pendulous [2]. Norway spruce cones areconspicuously large (4 to 7 inches [10-18 cm] long) [17]. The rootsystem is typically shallow, with several lateral roots and no taproot.On rocky sites the roots spread widely, twining over the rocks. On bogsoils, Norway spruce tends to form plate-like roots [42]. In Finland, a140-year-old Norway spruce forest in a Vaccinium-Myrtillus vegetationtype 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 from20 to 60 years of age [42,50]. Within its native range, Norway spruceremains healthy up to 200 years, and lives up to 300 to 400 years at thenorthern limits of its range [42]. Senescence occurs at less than 200years of age in the British Isles and North America [50].

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Ecology

Habitat

Habitat and Ecology

Picea abies is widespread and dominant in Boreal conifer forests of N and NE Europe, where it replaces Pinus sylvestris on wetter sites because Picea abies can avoid the water table with a very shallow root system. Ocurs from sea level up to 2,000 m. The natural distribution shows continental tendencies but in the western mountains of Central Europe an ecotype has evolved that is adapted to sub-Atlantic weather conditions with heavy 'wet' snowfall in early winter. Its inability to compete with more shade tolerant Abies alba and Fagus sylvatica as well as historical factors have limited its natural expansion into W Europe. In the Alps Picea abies occupies the montane to subalpine zones (dependent on local climate) especially on moist sites and in cold air pockets. Although it can occur on most substrates, acidic soils are most common and widespread as is testified by the undergrowth, if present, of ericaceous shrubs and sub-shrubs. Commonly growing with Picea abies in the Boreal forests are Betula sp. and Populus tremula, with willows (Salix) alongside streams and lakes. In the Alps Picea abies occurs with Larix decidua, Pinus cembra, and P. sylvestris or P. nigra, if not in pure stands. In E Europe, Picea abies is a constituent of mixed conifer-broad-leaved woodland from the Bialowiecza Forest in the north to the valleys of the eastern Alps and the Carpatians.

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Range and Habitat in Illinois

The non-native Norway Spruce has naturalized only in the NW corner of Illinois in Jo Daviess County, where it is rare. It was introduced into North America from Europe, where it is native. In Illinois, this tree has naturalized in a woods (Mohlenbrock, 2002), where it is apparently successfully reproducing. Norway Spruce is far more common in cultivation, where it used as a landscape tree, a windbreak tree, and a plantation tree (for Christmas trees and other commercial markets).

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Habitat 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 alsogrows well on almost all other types of soils. Permanently waterloggedsoils inhibit Norway spruce growth, but Norway spruce does occur onpoorly drained soils and in bogs [42]. Growth rates increase withincreased soil organic material and are positively correlated to thenitrogen content of the soil. In southern Finland, soil pH under 34- to38-year-old plantations of Norway spruce ranged from 3.7 to 4.4. Norwayspruce is also found on podzolized soils [45].

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Associations

Faunal Associations

A number of insects feed on the foliage, bore through bark, or suck plant juices from Norway Spruce and other spruce trees (Picea spp.). These insects include the caterpillars of such moths as Choristoneura fumiferana (Spruce Budworm), Elaphria versicolor (Variegated Midget), Endothenia albolineana (Spruce Needle Miner), and Feralia comstocki (Comstock's Sallow); see the Moth Table for a more complete listing of these species. Another group of insect feeders include the wood-boring larvae of such long-horned beetles as Monochamus marmorator (Balsam Fir Sawyer), Monochamus titillator (Southern Pine Sawyer), and Semanotus litigiosus (Fir Tree Borer); see the Long-Horned Beetle Table for a more complete listing of these species. Other miscellaneous insect feeders include Adelges abietis (Eastern Spruce Gall Adelgid), Chionaspis pinifoliae (Pine Needle Scale), Physokermes piceae (Spruce Bud Scale), the aphids Cinara pinicola and Cinara pruinosa, the plant bug Psallovius piceicola, the weevils Hylobius pales (Pales Weevil) and Pissodes approximatus (Northern Pine Weevil), and the root-feeding larvae of Strigoderma arboricola (False Japanese Beetle). An arachnid invertebrate species, Oligonychus ununguis (Spruce Spider Mite), also feeds on these trees. Among vertebrate animals, the seeds of spruces are eaten by such birds as the Red Crossbill, White-Winged Crossbill, Red-Breasted Nuthatch, Slate-Colored Junco, and Pine Siskin; the Red Squirrel also consumes the seeds. Norway Spruce is one one of the least preferred sources of food of White-Tailed Deer, although Cottontail Rabbits occasionally browse on seedlings of this tree during the winter. Because of their dense branching structure and evergreen foliage, spruce trees are used as nesting habitat by such birds as the Golden-Crowned Kinglet, Blackburnian Warbler, and Blackpoll Warbler; this generally occurs in boreal areas to the north or northeast of Illinois. Some birds like to roost in spruces, particularly during the winter, because of the protective cover that they provide.

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General Ecology

Fire Management Considerations

Prescribed fire has been used as a tool for forest regeneration inNorway, primarily to prepare the ground for natural regeneration fromseed trees, usually Scotch pine. Management of Norway spruce in Norwayis often based on information from other countries where Norway spruceand Scot's pine are the dominant conifers. After World War II, prescribedfires were used to prepare sites for artificial regeneration, either forsowing Scot's pine seeds or for planting Norway spruce nursery stock.It is often difficult to conduct prescribed fires in Norway; the weatheris changeable and conditions are often too moist for burning. Thesefacts, coupled with increasing costs of burning, have led to apreference for site scarification by mechanical means instead of fire[6]. Prescribed fires are not used much in Finland today either, due tohigh costs and variable weather [78]. The average size of individualwildfires is usually greatest in mixed stands of Scot's pine and Norwayspruce [61].

Norway spruce is known as a nutrient-demanding species; this has led toconcern that prescribed fire for site preparation burns too much of thehumus and results in soils that are not favorable for good Norway sprucegrowth. In Norway, Norway spruce seedlings showed good 12-year survivalon both burned (83 percent survival) and unburned (78 percent survival)sites. Overall height growth on unburned sites was slightly better at12 years than on burned sites, although early growth on burned sites wasbetter [6]. In Sweden, sites that were clearcut and burned, then seededwith Norway spruce were compared with similar sites that had not beenburned. The unburned sites had thicker humus layers after 43 years ofgrowth. The authors estimate that it takes 70 to 80 years from the timeof the fire for burned humus layers to be rebuilt to prefire levels [37].

Prescribing fire for site preparation in Scandinavia depends on thevegetation type. Types that are characterized by thick, raw humuslayers benefit from fire, which releases nutrients and activates thehumus [6,74]. After fire passes over humus, ashes and carbonized plantsform a thin cover over the otherwise undamaged humus layers [74].Prescribed fires used for site preparation must be conducted with careto prevent destruction of humus and excessive heating of upper mineralsoil. Fires temperatures of 662 degrees Fahrenheit (350 deg C) or lessat the soil surface will release nutrients stored in litter and allowthem to condense in the humus and upper mineral soils [28]. Fires thatburn quickly enough to leave humus may be acceptable. Decompositionrates in northern Norway spruce forests are very slow. In Finland, 56years after logging, even very thin branches are left intact in slashand litter [54]. Prescribed fires can release some of this organicmatter, and increase the pH of the soil. Some nutrients are lost to theatmosphere [78]. Types with thin humus layers are better unburned,since the humus would be destroyed by fire [66,79]. Norway spruce isunsuited for such sites, since its shallow roots render it less able toexploit the mineral soil for nutrients than Scotch pine [37].Prescribed burning is usually not necessary on most fertile soils, butmay be useful on sites that have experienced swale cultivation [79].

Fire suppression in Sweden since the nineteenth century has resulted inan over-representation of aging Norway spruce forests, and it has beenrecommended that prescribed fires for stand rejuvenation are necessaryin Swedish National Parks and nature reserves to improve stand health byreestablishing a mosaic of seral stands [84].

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Immediate Effect of Fire

Norway spruce is easily damaged or killed by fire [74]. The crowncanopy of Norway spruce is often totally destroyed by even minor surfacefires [64,76]. However, there are almost always scattered survivorseven following crown fires; in most cases survival is due to localtopography which prevents fire spread [82]. In Finland, forest firedamage is greatest in Norway spruce forests (compared with mixed or pureScotch pine stands) [61]. In the United States, grass fires arereported to cause severe damage to Norway spruce plantations [17].

In a laboratory study in which heated air was applied to stem sectionsand to whole tops of dormant 3- and 4-year-old Norway spruce seedlings,Norway spruce was found to be more tolerant of heat than European larchor Japanese larch (Larix leptolepis). Active Norway spruce seedlingswere more heat tolerant than European and Japanese larch, eastern whitepine (Pinus strobus), Scotch pine, or American beech (Fagusgrandifolia), but none were very tolerant. In this experiment, noseedlings were killed by the heat treatment, but dormant Norway spruceseedlings were almost completely defoliated [39].

Fire Ecology

Norway spruce is not well adapted to survive fire. Fire in maturestands of Norway spruce is usually of high intensity and destroys allstanding trees [15]. Fire severity usually depends on a number offactors, primarily soil moisture [74]. In taiga forests overpermafrost, low-severity fires leaving standing live trees mayeventually result in complete stand destruction since windfall of theremaining trees may occur when increased insolation on blackened soilthaws the permafrost. There is little regeneration in stagnant standsof Norway spruce; the next generation of trees is only produced after afire [15]. Norway spruce is easily killed by fire and is not an earlycolonizer in postfire succession; stand-destroying fires usually resultin replacement by Scot's pine. Norway spruce develops as the understoryin Scot's pine stands on suitable sites, and will eventually replaceScot's pine to complete the successional cycle [7,15,70].

Fire history in Norway: Fire was used extensively for agriculturalclearing in southeastern Norway 300 to 400 years ago. After a shortperiod of cultivation, depleted soils were left to naturalreforestation, forming mixtures of conifers and broadleaf trees, mostlybirch (Betula pubescens or B. verrucosa) [6]. In the pollen record,Norway spruce pollen increased during periods of lower disturbance andfewer fires. In the last 200 years, since agricultural burning hasvirtually ceased, Norway spruce stands have formed closed canopies withvery little groundlayer vegetation [7].

Fire history in Finland: Fire frequencies have been estimated to rangefrom 31 to 81 years for different historical periods. Human activityhas played a large role in fire history; a large amount of burningoccurred during the Iron Age and medieval periods, mostly due to slashand burn agriculture, from about 1 AD to 1750 AD [72]. Prior to theappearance of cereal pollens, charcoal analysis of bog soils indicatesthat, an average of one fire every 84 years occurred between 3000 and2000 BP. There is an inverse relationship between the amount of Piceapollen and the amount and frequency of charcoal particles; when firefrequency is high, Norway spruce densities are low [73].

Fire history in Sweden: In northern Sweden, the mean fire rotation (theamount of time equivalent to the area studied divided by the area ofsample plot burned annually) was approximately 100 years for mixedstands of Norway spruce and Scotch pine from the end of the medievalperiod up to the end of the nineteenth century. Since fire suppression,the estimated fire rotation is on the order of 3,500 years. Thepresuppression fire rotation created a mosaic of even-aged stands atdifferent successional stages. Norway spruce often forms theundergrowth in Scotch pine stands that survive or are regenerated afterfire; Scotch pine often survives as an overstory tree and can reach veryold ages. In Norway spruce forests on wet sites fires have been rare;fire-free intervals of up to 500 years have been reported for such sites[21,84,85]. The mean number of years between fires and the amount oftime since the last fire were positively correlated to basal area ofNorway spruce; Norway spruce density increases when fires occur at longintervals and shorter intervals favor Scotch pine [21].

Fire history in northern European Russia: Estimates from fire scar dataindicate fire frequencies on the order of 130 to 200 years in spruceforests (including Siberian spruce and Norway spruce) [76].

Successional Status

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

Disturbance events such as windfalls, snow damage, disease and insectattack create small-scale gaps in the mature canopy. Norway sprucedepends largely on advance regeneration (seedling banks) to capture suchcanopy gaps [56]. Norway spruce is the most common gapmaker and it isalso the most common seedling in gaps. Seedlings survive in anextremely stunted condition for many years. This reservoir of seedlingsfunctions in a way analogous to soil seedbanks [29]. Suppressed Norwayspruce saplings can persist for several decades, retaining the abilityto respond to canopy gaps with increased growth [35]. In Sweden,suppressed Norway spruce trees less than 8.2 feet (2.5 m) tall and 100to 220 years old exhibited new growth during gap-phase replacement [70].In Bavarian Norway spruce stands, storm-caused windfall disturbanceswere followed by new Norway spruce stands that were older than than thewindfall event (indicating advance regeneration). Sites that had beencleaned (removal of dead trees and broken stems) had a birch-dominatedregeneration layer that originated after the windfall event. Spruceseedlings were probably damaged by the cleaning operation [23]. Innorthern Sweden, Norway spruce-hairy birch forests consist of all-aged(up to 330 years) Norway spruce (largely as a result of gap-capturereplacement) [35].

Norway spruce first occurred in Scandinavia approximately 2,500 yearsago; its immigration from Europe is attributed to colder Scandinavianwinters coupled with increased precipitation and storm events whichallowed Norway spruce to colonize areas that were formerly too dry [7].It survived in Scandinavia in low densities due to frequent disturbancesuntil climatic changes coupled with a decrease in human-causeddisturbances (mainly fire) allowed natural succession to proceed,resulting in the current widespread distribution of dense Norwayspruce-dominated forests [8].

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Regeneration Processes

Sexual reproduction: Norway spruce usually first reproduces at 30 to 40years of age. Good seed crops are produced every 3 to 4 years inBritain, 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; seedyield is lower in smaller stems in stands of the same age. Norwayspruce seeds are wind dispersed, but do not usually travel much fartherthan the height of the parent tree [42]. Movement after dispersal,however, can be considerable when seeds are dispersed onto crusted snowand are pushed along on the surface by wind [34,74]. Seeds of Norwayspruce germinate promptly and do not require pretreatment or exactinglight regimes. Moist chilling of some spruce (Picea spp.) seeds removesthe requirement for light [87]. Optimum germination temperature forNorway spruce seeds is around 73 degrees Fahrenheit (23 deg C) butgermination will occur up to about 91 degrees Fahrenheit (33 deg C)[42]. Seedling growth is best at constant low temperature (48 degreesFahrenheit [9 deg C]), rather than with fluctuating temperatures orsteady high temperatures [36]. The seedlings are sensitive to droughtand/or overheating, particularly when the soil surface is exposed todirect insolation [42]. In Utah, nursery-grown seedlings inclined tothe south (to shade the soil directly under the seedling and keep theroots cooler and wetter) averaged 6 percent mortality from heat damage,whereas seedlings inclined to the north averaged 30 percent mortalityfrom the same cause [41]. Other studies support the hypothesis thatshading improves early seedling survival [33,77]. Thin humus (asopposed to thick humus) hinders Norway spruce establishment since itdries out more quickly and contributes to drought stress of theseedlings [70].

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

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

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Management considerations

Norway spruce is the most intensively studied spruce in the world. Anumber of geographic races have been identified, and numerous geneticimprovement programs are underway, mostly in Europe and Scandinavia[87]. In Europe, Norway spruce is the focus of increasing concern aboutforest decline. It is exhibiting a specific set of symptoms("Waldsterben") which are also showing up in forest trees in the UnitedStates (including red spruce [Picea rubens] and Norway spruce)[40,46,55,66]. These symptoms include needle chlorosis combined withmagnesium deficiency and thinning of the crown [46]. Explanationsusually center on air pollution (ozone, acid deposition, or toxic metalscontamination) coupled with acidified, depleted soils that cause, amongother problems, foliar magnesium deficiency [12,46,55,58,66].

Soils under Norway spruce stands are often more acidic than soils underother species. Soil acidity appears to increase with stand age as soilbuffering capacity decreases with age [4].

Artificial Reforestation: Norway spruce has been widely planted inreforestation programs in the eastern United States [2]. In Ontario,expected rotation of Norway spruce ranges from 60 to 70 years. Sitesare prepared by plowing, and Norway spruce seedlings are planted with 5 x5 foot spacing (1.5 x 1.5 m) [19].

Silviculture: In Europe, Norway spruce is usually managed withselection systems in mixtures with European beech and European silverfir, particularly on private holdings. Such mixtures require frequentthinning to maintain European silver fir, which would otherwise beeliminated by the beech and Norway spruce [67]. Norway spruce is alsomanaged with even-aged systems such as patch clearcutting andstrip-cutting [49]. In Sweden, single-tree selection has been oflimited use, but a recent report suggests that it is possible to obtainabundant regeneration and high ingrowth rates in selection stands withhigh levels of standing volume [48]. Scotch pine can be planted as anurse tree for Norway spruce; such mixtures result in a net gain inproduction over monocultures of either species [10]. During drysummers, spruce litter buildup can create manganese concentrations thatprevent regeneration of Norway spruce. As a consequence, land managersin France alternate rotations of Norway spruce and hardwoods, or destroythe toxic manganese in litter by scarification [20].

Norway spruce is resistant to mistblown glyphosate used to killcompeting hardwoods [81].

Fertilization of Norway spruce can promote frost damage by prolongingthe growing season, and delaying cuticularization of the epidermis [68].

In Belgium, Norway spruce was excluded from heathlands (Callunavulgaris) created by burn-beating cultivation (cutting, piling andburning humus layers to fertilize fields), mowing, and sheep grazing.Norway spruce has been planted on these former heathlands, andburn-beating agriculture is no longer practiced. Since burn-beatingremoves the humus layer these Norway spruce plantations are growing onseverely depleted soils. Depleted soils may be contributing toWaldsterben in these plantations, and may also present problems forfuture rotations [25].

In Finland, 15- to 20-year-old natural stands of Norway spruce werefrost hardy (defined as the temperature at which 50 percent mortality ofbud occurs) to 24.8 degrees Fahrenheit (-4 deg C) in mid-summer, andfrost hardy to -54.4 degrees Fahrenheit (-48 deg C) in January.Hardening occurs over a short period in September, and is lost over ashort period in early May [59].

Insect Pests: In North America, Norway spruce is host to western sprucebudworm [13] and mountain pine beetle [32].

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Relevance to Humans and Ecosystems

Benefits

Cultivation

The preference is partial to full sun, well-drained moist conditions, and an acidic fertile soil consisting of sandy loam or other soil types. A cool, moist, and humid climate is also preferred, although this tree can tolerate a temperate climate that is more warm and dry. Growth is relatively fast for a conifer during the early stages of development.. Under favorable conditions in North America, this tree will live 100-200 years, if not longer. Where the soil has a low pH, it is vulnerable to acid rain.

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Other uses and values

Norway spruce has been planted for windbreaks and shelterbelts inwestern prairies, although it grows better in more humid environments[17]. It is recommended for shelterbelt plantings in humid,severe-winter regions [2]. Norway spruce is widely planted forChristmas trees and as an ornamental [17].

Norway spruce roots can be used as grafting stock for white spruce(Picea glauca) [52].

Norway spruce resin has been used to make Burgundy pitch, and the twigsused to make Swiss turpentine. The twigs and needles were used to makeantiscorbutic and diuretic beverages [87].

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Importance to Livestock and Wildlife

Norway spruce seedlings are highly preferred winter browse for snowshoehares in Quebec. Browsing of seedlings and saplings in plantations canbe intense, as young plantations form ideal winter habitat for snowshoehares [3]. Norway spruce is not a preferred browse for moose inScandinavia; young and middle-aged stands of Scotch pine form habitatpreferred by moose over mature Scotch pine-Norway spruce forests andbogs [14]. In Europe, red deer strip the bark of Norway spruce [60].Other animals browse spruce foliage but it is not a highly preferredfood source for either wildlife or domestic animals [87]. Norway spruceprovides important winter cover for a number of species of wildlife[80]. Grouse eat spruce leaves and the seeds are consumed by a numberof birds and small mammals [86,87].

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Wood Products Value

Norway spruce wood is strong, soft, straight- and fine-grained, andeasily worked [17,87]. It is not durable in contact with soil. It iswidely used for construction, pulp, furniture, and musical instruments[17,80]. Norway spruce is one of the most common and economicallyimportant coniferous species in Europe and Scandinavia [46]. In Maine,thinned material and standing dead Norway spruce produced pulp of goodstrength as reported in a study of the pulp potential of seven softwoods [16].

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Wikipedia

Picea abies

Picea abies, the Norway spruce,[2] is a species of spruce native to Central and Eastern Europe. It grows up to 55 m (180 ft) tall, and bears needles 12–24 mm (0.47–0.94 in) long and cones 9–17 cm (3.5–6.7 in) long. It is very closely related to the Siberian spruce, Picea obovata, which replaces it east of the Ural Mountains, and with which it hybridises freely. Picea abies is widely planted for its wood, and is the species used as the main Christmas tree in several cities around the world. It was the first gymnosperm to have its genome sequenced, and one clone has been measured as 9,550 years old.

Picea abies is a large, fast-growing evergreenconiferoustree growing 35–55 m (115–180 ft) tall and with a trunk diameter of 1 to 1.5m. It can grow fast when young, up to 1 m (3 ft) per year for the first 25 years under good conditions, but becomes slower once over 20 m (66 ft) tall.[3] The shoots are orange-brown and glabrous (hairless). The leaves are needle-like, 12–24 mm long, quadrangular in cross-section (not flattened), and dark green on all four sides with inconspicuous stomatal lines. The cones are 9–17 cm long (the longest of any spruce), and have bluntly to sharply triangular-pointed scale tips. They are green or reddish, maturing brown 5–7 months after pollination. The seeds are black, 4–5 mm long, with a pale brown 15 mm wing.[4][5][6][1][7]

Picea abies grows throughout Europe from Norway in the northwest and Poland eastward, and also in the mountains of central Europe, southwest to the western end of the Alps, and southeast in the Carpathians and Balkans to the extreme north of Greece. The northern limit is in the arctic, just north of 70° N in Norway. Its eastern limit in Russia is hard to define, due to extensive hybridisation and intergradation with the Siberian spruce, but is usually given as the Ural Mountains. However, trees showing some Siberian spruce characters extend as far west as much of northern Finland, with a few records in northeast Norway. The hybrid is known as Picea × fennica (or P. abies subsp. fennica, if the two taxa are considered subspecies), and can be distinguished by a tendency towards having hairy shoots and cones with smoothly rounded scales.[4][5][6]

The Norway spruce is one of the most widely planted spruces, both in and outside of its native range, and one of the most economically important coniferous species in Europe.[8] It is used as an ornamental tree in parks and gardens. It is also widely planted for use as a Christmas tree. Every Christmas, the Norwegian capital city, Oslo, provides the cities of New York, London (the Trafalgar Square Christmas tree), Edinburgh and Washington D.C. with a Norway spruce, which is placed at the most central square of each city. This is mainly a sign of gratitude for the aid these countries gave during the Second World War.[citation needed]

In North America, Norway spruce is widely planted, specifically in the northeastern, Pacific Coast, and Rocky Mountain states, as well as in southeastern Canada. It is naturalised in some parts of North America. There are naturalised populations occurring from Connecticut to Michigan, and it is probable that they occur elsewhere.[8] Norway spruces are more tolerant of hot, humid weather than many conifers which do not thrive except in cool-summer areas and they will grow up to USDA Growing Zone 8.

In the northern US and Canada, Norway spruce is reported as invasive in some locations, however it does not pose a problem in Zones 6 and up as the seeds have a significantly reduced germination rate in areas with hot, humid summers.

The Norway spruce tolerates acidic soils well, but does not do well on dry or deficient soils. From 1928 until the 1960s it was planted on surface mine spoils in Indiana.[8]

The tree is the source of spruce beer, which was once used to prevent and even cure scurvy.[9]

It is esteemed as a source of tonewood by stringed-instrument makers.[10]

Picea abies shoot tips have been used in the traditional Austrian medicine internally (as syrup or tea) and externally (as baths, for inhalation, as ointments, as resin application or as tea) for treatment of disorders of the respiratory tract, skin, locomotor system, gastrointestinal tract and infections.[11]

The stress is on the difference between the singular "oldest tree" and the multiple "oldest trees", and between "oldest clone" and "oldest non-clone". The oldest known individual tree (that has not taken advantage of vegetative cloning) is a Great Basin bristlecone pine over 5,000 years old (germination in 3051 BC).[16]

The Norway spruce genome was sequenced in 2013, the first gymnosperm genome to be completely sequenced.[17] The genome contains approximately 20 billion base pairs and is about six times the size of the human genome, despite possessing a similar number of genes. A large proportion of the spruce genome consists of repetitive DNA sequences, including long terminal repeat transposable elements. Despite recent advances in massively parallel DNA sequencing, the assembly of such a large and repetitive genome is a particularly challenging task, mainly from a computational perspective.[18]

Populations in southeast Europe tend to have on average longer cones with more pointed scales; these are sometimes distinguished as Picea abies var. acuminata (Beck) Dallim. & A.B. Jacks., but there is extensive overlap in variation with trees from other parts of the range.[4][5][6]

Some botanists treat Siberian spruce as a subspecies of Norway spruce, though in their typical forms, they are very distinct, the Siberian spruce having cones only 5–10 cm long, with smoothly rounded scales, and pubescent (hairy) shoots.[4][5][6]Genetically Norway and Siberian spruces have turned out to be extremely similar and may be considered as two closely related subspecies of P. abies.[22]

Another spruce with smoothly rounded cone scales and hairy shoots occurs rarely in the Central Alps in eastern Switzerland. It is also distinct in having thicker, blue-green leaves. Many texts treat this as a variant of Norway spruce, but it is as distinct as many other spruces, and appears to be more closely related to Siberian spruce (Picea obovata), Schrenk's spruce (Picea schrenkiana) from central Asia and Morinda spruce (Picea smithiana) in the Himalaya. Treated as a distinct species, it takes the name Alpine spruce (Picea alpestris (Brügger) Stein). As with Siberian spruce, it hybridises extensively with Norway spruce; pure specimens are rare. Hybrids are commonly known as Norwegian spruce, which should not be confused with the pure species Norway spruce.[4][5][6]

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Norway spruce, native to Europe, has become locally naturalized, at least in north central United States (and adjacent Canada). The species is the most widely cultivated spruce in North America; many cultivars exist, including dwarf shrubs.