Spruce Production Division Soldiers

A spruce is a tree of the genus ''Picea'' ( ), a genus of about 40 species of coniferous evergreen trees in the family Pinaceae, found in the northern temperate and boreal (taiga) regions of the Northern hemisphere. ''Picea'' is the sole genus in the subfamily Piceoideae. Spruces are large trees, from about 20 to 60 m (about 60–200 ft) tall when mature, and have whorled branches and conical form.

Spruces can be distinguished from other genera of the family Pinaceae by their needles (leaves), which are four-sided and attached singly to small persistent peg-like structures ( pulvini or sterigmata) on the branches, and by their cones (without any protruding bracts), which hang downwards after they are pollinated. The needles are shed when 4–10 years old, leaving the branches rough with the retained pegs. In other similar genera, the branches are fairly smooth.

Spruce are used as food plants by the larvae of some Lepidoptera (moth and butterfly) species, such as the eastern spruce budworm. They are also used by the larvae of gall adelgids (''Adelges'' species).

In the mountains of Dalarna, Sweden, scientists have found a Norway spruce, nicknamed Old Tjikko, which by reproducing through layering, has reached an age of 9,550 years and is claimed to be the world's oldest known living tree.

Description

Morphology

Determining that a tree is a spruce is not difficult; evergreen needles that are more or less quadrangled, and especially the pulvinus, give it away. Beyond that, determination can become more difficult. Intensive sampling in the Smithers/Hazelton/Houston area of British Columbia showed Douglas (1975),Douglas, G.W. (1975). Spruce (''Picea'') hybridization in west-central British Columbia. B.C. Min. For., Forest Science, Smithers BC, unpublished report, cited by Coates et al. 1994. (Cited by Coates et al. 1994, orig. not seen) according to Coates et al. (1994),Coates, K.D.; Haeussler, S.; Lindeburgh, S.; Pojar, R.; Stock, A.J. (1994). Ecology and silviculture of interior spruce in British Columbia. Canada/British Columbia Partnership Agreement For. Resour. Devel., Victoria BC, FRDA Rep. 220. 182 p. that cone scale morphology was the feature most useful in differentiating species of spruce; the length, width, length: width ratio, the length of free scale (the distance from the imprint of the seed wing to the tip of the scale), and the percentage free scale (length of free scale as a percentage of the total length of the scale) were most useful in this regard. Daubenmire (1974), after range-wide sampling, had already recognized the importance of the two latter characters. Taylor (1959) (Cited in Coates et al. 1994). had noted that the most obvious morphological difference between typical ''Picea glauca'' and typical ''P. engelmannii'' was the cone scale, and Horton (1956,1959)Horton, K.W. (1956). A taxonomic and ecological study of ''Picea glauca'' and ''Picea engelmannii'' in North America. Diploma thesis, Oxford Univ., U.K. 103 p.Horton, K.W. (1959). Characteristics of subalpine spruce in Alberta. Can. Dep. Northern Affairs National Resour., For. Branch, For. Res. Div., Ottawa ON, Tech. Note 76. 20 p. found that the most useful diagnostic features of the two spruces are in the cone; differences occur in the flower, shoot and needle, "but those in the cone are most easily assessed" (Horton 1959). Coupé et al. (1982)Coupé, R.; Ray, C.A.; Comeau, A.; Ketcheson, M.V.; Annas, R.M. (1982). A guide to some common plants of the Skeena area, British Columbia. B.C. Min. For., Res. Branch, Victoria BC. recommended that cone scale characters be based on samples taken from the midsection of each of ten cones from each of five trees in the population of interest.

Without cones, morphological differentiation among spruce species and their hybrids is more difficult. Species classification for seeds collected from spruce stands in which introgressive hybridization between white and Sitka spruces (''P. sitchensis'') may have occurred is important for determining appropriate cultural regimens in the nursery. If, for instance, white spruce grown at container nurseries in southwestern British Columbia are not given an extended photoperiod, leader growth ceases early in the first growing season, and seedlings do not reach the minimum height specifications.Arnott, J.T. (1974). "Germination and seedling establishment". pp. 55–66 in Cayford, J.H. (Ed.). ''Direct Seeding Symposium'', Timmins ON, Sept. 1973, Can. Dep. Environ., Can. For. Serv., Ottawa ON, Proc., Publ. 1339. But, if an extended photoperiod is provided for Sitka spruce, seedlings become unacceptably tall by the end of the first growing season. Species classification of seedlots collected in areas where hybridization of white and Sitka spruces has been reported has depended on (i) easily measured cone scale characters of seed trees, especially free scale length, (ii) visual judgements of morphological characters, e.g., growth rhythm, shoot and root weight, and needle serration, or (iii) some combination of (i) and (ii) (Yeh and Arnott 1986). Useful to a degree, these classification procedures have important limitations; genetic composition of the seeds produced by a stand is determined by both the seed trees and the pollen parents, and species classification of hybrid seedlots and estimates of their level of introgression on the basis of seed-tree characteristics can be unreliable when hybrid seedlots vary in their introgressiveness in consequence of spatial and temporal variations in contributions from the pollen parent (Yeh and Arnott 1986). Secondly, morphological characters are markedly influenced by ontogenetic and environmental influences, so that to discern spruce hybrid seedlot composition with accuracy, hybrid seedlots must differ substantially in morphology from both parent species. Yeh and Arnott (1986) pointed out the difficulties of estimating accurately the degree of introgression between white and Sitka spruces; introgression may have occurred at low levels, and/or hybrid seed lots may vary in their degree of introgression in consequence of repeated backcrossing with parental species.

Growth

Spruce seedlings are most susceptible immediately following germination, and remain highly susceptible through to the following spring. More than half of spruce seedling mortality probably occurs during the first growing season and is also very high during the first winter,Alexander, R.R. (1987). Ecology, silviculture, and management of the Engelmann spruce–subalpine fir type in the central and southern Rocky Mountains. USDA, For. Serv., Washington DC, Agric. Handb. 659. 144 p. when seedlings are subjected to freezing damage, frost heaving and erosion, as well as smothering by litter and snow-pressed vegetation. Seedlings that germinate late in the growing season are particularly vulnerable because they are tiny and have not had time to harden off fully.

Mortality rates generally decrease sharply thereafter, but losses often remain high for some years. "Establishment" is a subjective concept based on the idea that once a seedling has successfully reached a certain size, not much is likely to prevent its further development. Criteria vary, of course, but Noble and Ronco (1978),Noble, D.L.; Ronco, F. (1978). Seedfall and establishment of Engelmann spruce and subalpine fir in clearcut openings in Colorado. USDA, For. Serv., Rocky Mountain For. Range Exp. Sta., Res. Pap. RM-200. 12 p. for instance, considered that seedlings four to five years old, or 8 cm to 10 cm tall, warranted the designation "established", since only unusual factors such as snow mold, fire, trampling, or predation would then impair regeneration success. Eis (1967) suggested that in dry habitats on either mineral soil or litter seedbeds a 3-year-old seedling may be considered established; in moist habitats, seedlings may need 4 or 5 years to become established on mineral soil, possibly longer on litter seedbeds.

Growth remains very slow for several to many years. Three years after shelterwood felling in subalpine Alberta, dominant regeneration averaged 5.5 cm in height in scarified blocks, and 7.3 cm in non-scarified blocks (Day 1970),Day, M.W.; Rudolph, V.J. (1970). Development of a white spruce plantation. Michigan State Univ., Agric. Exp. Sta., East Lansing MI, Res. Pap. 111. 4 p. possibly reflecting diminished fertility with the removal of the A horizon.

Taxonomy

Classification

DNA analyses have shown that traditional classifications based on the morphology of needle and cone are artificial. A 2006 study found that '' P. breweriana'' had a basal position, followed by '' P. sitchensis'', and the other species were further divided into three clades, suggesting that ''Picea'' originated in North America. The oldest record of spruce that has been found in the fossil record is from the Early Cretaceous (Valanginian) of western Canada, around 136 million years old.

Species

, Plants of the World Online accepted 37 species. The grouping is based on Ran et al. (2006).
*Basal species:
** '' Picea breweriana'' – Brewer's spruce, Klamath Mountains, North America; local endemic
** ''Picea sitchensis'' – Sitka spruce, Pacific coast of North America; the largest species, to 95 m tall; important in forestry
*Clade I (Northern and western North America, in boreal forests or high mountains)
** ''Picea engelmannii'' – Engelmann spruce, western North American mountains; important in forestry
** ''Picea glauca'', syn. ''Picea laxa'' – white spruce, northern North America; important in forestry
*Clade II (throughout Asia, mostly in mountainous areas, a few isolated populations in higher elevations of Mexico,)
** '' Picea brachytyla'' – Sargent's spruce, southwest China
** '' Picea chihuahuana'' – Chihuahua spruce, northwest Mexico (rare)
** '' Picea farreri'' – Burmese spruce, northeast Burma, southwest China (mountains)
** '' Picea likiangensis'' – Likiang spruce, southwest China
** '' Picea martinezii'' – Martinez spruce, northeast Mexico (very rare, endangered)
** '' Picea maximowiczii'' – Maximowicz spruce, Japan (rare, mountains)
** '' Picea morrisonicola'' – Taiwan spruce, Taiwan (high mountains)
** '' Picea neoveitchii'' – Veitch's spruce, northwest China (rare, endangered)
** '' Picea orientalis'' – Caucasian spruce or Oriental spruce, Caucasus, northeast Turkey
** '' Picea polita'', syn. ''Picea torano'' – tiger-tail spruce, Japan
** '' Picea purpurea'' – purple cone spruce, western China
** '' Picea schrenkiana'' – Schrenk's spruce, mountains of central Asia
** '' Picea smithiana'' – morinda spruce, western Himalaya, eastern Afghanistan, northern and northwest India
** '' Picea spinulosa'' – Sikkim spruce, northeast India (Sikkim), eastern Himalaya
** '' Picea wilsonii'' – Wilson's spruce, western China
*Clade III (Europe, Asia, and North America, mostly in boreal forests or mountainous areas)
** ''Picea abies'' – Norway spruce, Europe; important in forestry, the original Christmas tree
** '' Picea alcoquiana'' – ("''P. bicolor''") Alcock's spruce, central Japan (mountains)
** '' Picea asperata'' – dragon spruce, western China; several varieties
** '' Picea crassifolia'' – Qinghai spruce, China
** '' Picea glehnii'' – Glehn's spruce, northern Japan, Sakhalin
** '' Picea jezoensis'' – Jezo spruce, northeast Asia, Kamchatka south to Japan
** '' Picea koraiensis'' – Korean spruce, Korea, northeast China
** '' Picea koyamae'' – Koyama's spruce, Japan (mountains)
** ''Picea mariana'' – black spruce, northern North America
** '' Picea meyeri'' – Meyer's spruce, northern China (from Inner Mongolia to Gansu)
** '' Picea obovata'' – Siberian spruce, north Scandinavia, Siberia; often treated as a variant of ''P. abies'' (and hybridises with it), but has distinct cones
** '' Picea omorika'' – Serbian spruce, Serbia and Bosnia; local endemic; important in horticulture
** ''Picea pungens'' – blue spruce or Colorado spruce, Rocky Mountains, North America; important in horticulture
** '' Picea retroflexa'' – green dragon spruce, China
** ''Picea rubens'' – red spruce, northeastern North America; important in forestry, known as Adirondack in musical-instrument making
*Others
** '' Picea aurantiaca'' Mast.
** '' Picea austropanlanica'' Silba
** '' Picea linzhiensis'' (W.C.Cheng & L.K.Fu) Rushforth
*Hybrids
** ''Picea'' × ''albertiana'' S.Br.
** ''Picea'' × ''fennica'' (Regel) Kom.
** ''Picea'' × ''lutzii'' Little
** ''Picea'' × notha'' Rehder

Fossil species

There are also a number of extinct species identified from fossil evidence:

Cones

*†'' Picea anadyrensis''
*†'' Picea antiqua''
*†'' Picea beckii''
*†'' Picea bilibinii''
*†'' Picea burtonii''
*†'' Picea camtschatica''
*†'' Picea deweyensis''
*†'' Picea diettertiana''
*†'' Picea eichhornii''
*†'' Picea evenica''
*†'' Picea fimbriata''
*†'' Picea garoensis''
*†'' Picea harrimani''
*†'' Picea hondoensis''
*†'' Picea indigirensis''
*†'' Picea latibracteata''
*†'' Picea latisquamosa''
*†'' Picea metechensis''
*†'' Picea mioorientalis''
*†'' Picea mugodzharica''
*†'' Picea oligocaenica''
*†'' Picea pevekensis''
*†'' Picea praeajanensis''
*†'' Picea protopicea''
*†'' Picea sookensis''
*†'' Picea sugaii''
*†'' Picea suifunensis''
*†'' Picea vassiljevii''
*†'' Picea vitjasii''
*†'' Picea wolfei''
*†'' Picea wollosowiczii''
*†'' Picea yanensis''

Foliage

*†'' Picea cretacea''
*†'' Picea echinata''
*†'' Picea korfiensis''
*†'' Picea lahontensis''
*†'' Picea morosovae''
*†'' Picea nakauchii''
*†'' Picea palaeomorika''
*†'' Picea quilchensis''
*†'' Picea tranquillensis''

Pollen

*†'' Picea alata''
*†'' Picea bella''
*†'' Picea complanatiformis''
*†'' Picea depressa''
*†'' Picea distorta''
*†'' Picea distracta''
*†'' Picea exilioides''
*†'' Picea gigantissima''
*†'' Picea grandipollinia''
*†'' Picea grandis''
*†'' Picea grandivescipites''
*†'' Picea kryshtofovichii''
*†'' Picea longisaccata''
*†'' Picea media''
*†'' Picea mesophytica''
*†'' Picea minor''
*†'' Picea multigruma''
*†'' Picea omoriciformis''
*†'' Picea parvireticulata''
*†'' Picea pseudorotundiformis''
*†'' Picea rara''
*†'' Picea sacculifera''
*†'' Picea samoilovitchiana''
*†'' Picea schrenkianiformis''
*†'' Picea scotica''
*†'' Picea singularis''
*†'' Picea spirelliformis''
*†'' Picea sutschanensis''
*†'' Picea tasaranica''
*†'' Picea tobolica''
*†'' Picea valanjinica''

Seeds

*†'' Picea altaica''
*†'' Picea hiyamensis''
*†'' Picea kaneharae''
*†'' Picea kanoi''
*†'' Picea magna''
*†'' Picea pinifructus''
*†'' Picea sonomensis''

Wood

*†'' Picea palaeomaximowiczii''
*†'' Picea wakimizui''
*†'' Picea withamii''

Multiple organs

*†'' Picea columbiensis''
*†'' Picea critchfieldii'' - Late Quaternary North America.
*†'' Picea farjonii''
*†'' Picea heisseana''
*†'' Picea koribae''
*†'' Picea miocenica''
*†'' Picea rotundosquamosa''
*†'' Picea ugoana''

Unspecified

*†'' Picea alba''
*†'' Picea albertensis''
*†'' Picea snatolensis''

Fossil species formerly placed in ''Picea''

*†'' Picea cliffwoodensis'' moved to †'' Pityostrobus cliffwoodensis''
*†'' Picea succinifera'' moved to '' Pinus succinifera''

Cultivation

In the realm of spruce trees, the presence of Dendroctonus micans beetles significantly impacts their health and vitality. These beetles, particularly the males, display territorial behavior, diligently defending areas that are attractive to females for mating. By safeguarding these regions and providing suitable host trees, they create an environment conducive to egg-laying, thereby ensuring their reproductive success. This territoriality is closely tied to male reproductive prowess and plays a crucial role in understanding the dynamics of beetle populations and their impact on the overall health of spruce trees. Moreover, the home range of Dendroctonus micans varies based on the availability and density of host trees, with individual beetles dispersing across their habitat in search of optimal nesting sites.

Etymology

''Spruce'', ' (1412), and ' (1378) seem to have been generic terms for commodities brought to England by Hanseatic merchants (especially beer, boards, wooden chests and leather), and the tree thus was believed to be particular to Prussia, which for a time was figurative in England as a land of luxuries. It can be argued that the word is actually derived from the Old French

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