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Range of Picea (Vidakovic 1991).

 

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Picea

A. Dietrich 1824

Common names

Spruce, épicéa (French), épinette (Canadian French), abete or abies (Italian), fichte (German), gran (Swedish, Norwegian & Danish), jel (Russian), swierk (Polish), smarch (Bulgarian), smrche or omorike (Serbo-croat), yunshan (Chinese), momi (Japanese).

Taxonomic notes

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The genus is related most closely to Pinus, but differs markedly even from that. It is a very uniform genus, clearly monophyletic with no aberrant species, so generic segregation has never been suggested (Farjon 1990). There are 33 species treated here, though a careful re-evaluation of the poorly-studied East Asian taxa would probably reduce this number (Farjon 1990, Sigurgeirsson and Szmidt 1993). Classification within the genus has been problematic, and no satisfactory phylogeny was worked out despite numerous historical attempts (Wright 1955, Bobrov 1970, Liu 1982, Aldén 1987, Page and Hollands 1987, Rushforth 1987, Schmidt 1989, Farjon 1990, Frankis 1992, Sigurgeirsson and Szmidt 1993). The nut may have finally cracked in 2006, though, with the application of molecular technologies.

Ran et al. (2006) analyzed both paternal and maternal molecular markers (chloroplast and mitochondrial DNA) of all living species of Picea. Their results indicate that Picea breweriana and P. sitchensis are basal to Picea, with the other species in the genus divisible into three clades. They further infer two episodes of dispersal to Eurasia via the Beringian land bridge.

Although subdivisions within each of the three clades are not necessarily well-supported, the existence of the three clades appears conclusive in the data presented by Ran et al. (2006). They describe Clade I as including the two North American species P. engelmannii and P. glauca. Clade II includes 14 species, i.e., eight species (P. brachytyla, P. farreri, P. likiangensis, P. neoveitchii, P. purpurea, P. smithiana, P. spinulosa and P. wilsonii) from the Himalayan-Hengduan Mountains and its vicinities, P. schrenkiana from the Tianshan Mountains (Middle Asia), P. morrisonicola from Taiwan, P. orientalis from West Asia, two Japanese species P. maximowiczii and P. torano, and the North American P. chihuahuana. Within the clade, five species (P. farreri, P. likiangensis, P. schrenkiana, P. smithiana and P. spinulosa) form a sub-clade sister to another sub-clade comprising the remaining nine species. In Clade III, all northeastern Asian species sampled (except P. maximowiczii and P. torano), P. retroflexa and the European species P. abies clustered into a monophyletic group sister to two North American species P. mariana and P. rubens, and P. omorika from the Balkan Peninsula, with the North American P. pungens at the basal position.

Ran et al. (2006) note also that the earliest (Paleocene) known fossil of Picea is a pollen grain from Montana (Wilson and Webster 1946) and that the genus is well represented in Eocene sediments of western North America, but not common in Asia until the Oligocene and in Europe not until the Pliocene (LePage 2001). Thus the fossil evidence supports a North American origin for the genus. In a nicely reasoned analysis based mostly on an extensive literature review, Ran et al. (2006) argue that the species likely originated in northwestern North America and dispersed through Beringia to Asia and thence south and west, ultimately to Europe. They note that though the position of P. chihuahuana in Clade II suggests a reverse dispersal from Asia to Mexico, it is more likely that a progenitor of Clade II evolved in North America and then dispersed to Asia, subsequently becoming extinct in North America except for the Mexican relict P. chihuahuana. Similarly, the three North American species in Clade III are all basal to the clade and likely indicate that the clade originated in North America prior to its Beringian dispersal to Asia.

Description

Evergreen trees; crown broadly conic to spirelike, 20-60 (-90) m tall; leading shoot erect. Bark gray to reddish brown, thin and scaly (with thin plates), sometimes with resin blisters, becoming relatively thick and furrowed with age. Branches whorled with strong nodal pseudowhorls and additional scattered weaker internodal branches; short (spur) shoots absent; twigs roughened by persistent leaf bases (pulvini). Buds ovoid, apex rounded to acute, sometimes resinous. Leaves borne singly, spreading radially from twigs, usually somewhat forward-pointing and often upswept, persisting to 10 years, mostly 4-angled and square in cross section (to triangular or ± flattened), mostly rigid, sessile on peglike base; base decurrent, persistent after leaves shed, sheath absent; apex usually sharp-pointed, sometimes bluntly acute; resin canals 1-2. Cones borne on year-old twigs. Pollen cones single or grouped, axillary, oblong, yellow to purple; pollen shed in spring. Seed cones green to purple, maturing pale to dark brown in autumn, 4-8 months from pollination, usually shed at maturity, borne mostly on upper branches, pendent, ovoid to cylindric, sessile or terminal on leafy branchlets and thus appearing ± stalked; scales persistent, elliptic to fan-shaped, thin, lacking apophysis and umbo; bracts included. Seeds winged; cotyledons 5-10 (- l5). x =12 (Taylor 1993, M.P. Frankis e-mail 4-Jan-2002).

Distribution and Ecology

Restricted to subtropical high altitude , temperate, and boreal regions of the northern hemisphere. Confined to mountains in the south, its principal realm is the boreal forest, where it provides the dominant species across vast tracts of Scandinavia, Russia, Alaska, and Canada. It has its high est species diversity in the mountains of south and west China and Japan. The southernmost extension of the genus (P. morrisonicola) is on Taiwan, just south of the Tropic of Cancer at 23°N; in the New World Picea extends (via P. chihuahuana and P. martinezii) almost as far, but does not quite reach the Tropic (Taylor et al. 1994).

Big tree

See Picea sitchensis.

Oldest

Maximum attainable ages are known for relatively few species. Working by analogy from other members of the Pinaceae, the greatest ages are normally found on sites that provide extreme physiological stress due to drought, cold, or darkness (i.e. deep shade). Picea avoids arid climates, but it encounters cold stress and some drought stress at alpine timberline sites. An age of 852 years recorded for P. engelmannii on such a site is evidently the current record for the genus.

Dendrochronology

Ethnobotany

The genus is of major economic importance for timber, the most important species being P. sitchensis and P. abies. Several species are commonly used for Christmas trees, most often P. abies but also P. omorika and P. mariana (surely one of the homeliest conifers).

Observations

Remarks

Name from the Roman pix, pitch (Weber 1987); or from picis, the name of a pitchy pine (Taylor 1993).

Citations

LePage, B.A. 2001. New species of Picea A. Dietrich (Pinaceae) from the middle Eocene of Axel Heiberg Island, Arctic Canada. Biol. J. Linn. Soc. 135:137-167.

Wilson, L.R., and R.M. Webster. 1946. Plant microfossils from a Fort Union Coal of Montana. American Journal of Botany 33:271-278.

See also

Roche, L. 1969. A genecological study of the genus Picea and seedlings grown in a nursery. New Phytologist 68: 505-554.

Taylor, R.J. and T.F. Patterson. 1980. Biosystematics of Mexican spruce species and populations. Taxon 29: 421-469.

Last Modified 2012-11-23