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Picea A. Dietrich 1824
Common NamesSpruce, 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 notesThe genus is related most closely to Pinus, but differs markedly even from that (10). It is a very uniform genus, clearly monophyletic with no aberrant species, so generic segregation has ever been suggested (10). There are about 35 species, though a careful re-evaluation of the poorly-studied East Asian taxa would probably reduce this number (10, 12). Classification within the genus is problematic, and no fully satisfactory phylogeny has yet been worked out despite numerous attempts (3, 4, 5, 6, 7, 8, 9, 10, 11, 12). Extensive hybrid introgression and gene exchange between a number of species complicates the research; few spruces have well-established barriers to hybridisation.DescriptionEvergreen 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 (2, 14).RangeRestricted 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 (13).Big TreeSee Picea sitchensis.OldestMaximum 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.DendrochronologyEthnobotanyThe genus is of major economic importance for timber, the most important species being P. sitchensis and P. abies. Several species commonly used for Christmas trees, most often P. abies but also P. omorika and P. mariana (surely one of the homeliest conifers).ObservationsRemarksName from the Roman pix, pitch (1); or from picis, the name of a pitchy pine (2).Citations(1) Weber 1987.(2) Ronald J. Taylor at the Flora of North America web site. (3) Wright, J.W. 1955. Species crossability in spruce in relation to distribution and taxonomy. Forest Science 1: 319-349. (4) Bobrov, E. G. 1970. Generis Picea historia et systematica. Nov. Syst. Pl. Vasc. 7: 7-39 (in Russian & Latin). (5) Liu, T. S. 1982. A new proposal for the classification of the genus Picea. Acta Phytotax. Geobot. 33: 227-244. (6) Page, C. N. & R. C. Hollands 1987. The taxonomic and biogeographic position of Sitka spruce. Proceedings Royal Society Edinburh 93B: 13-24. (7) Rushforth, K. D. 1987. Conifers. Helm, London. (8) Aldén, B. 1987. Taxonomy and geography of the genus Picea. International Dendrological Society Yearbook 1986: 85-96. (9) Schmidt, P. A. 1989. Beitrag zur Systematik und Evolution der Gattung Picea. Flora 182: 435-461. (10) Farjon 1990 . (11) Frankis, M. P. 1992. Picea. In: A. Huxley, M. Griffiths & M. Levy (eds.) The New RHS Dictionary of Gardening 3: 570-573. (12) Sigurgeirsson, A. & A. E. Szmidt 1993. Phylogenetic and biogeographic implications of chloroplast DNA variation in Picea. Nordic Journal of Botany 13: 233-246. (13) Taylor, R. J., T. F. Patterson & R. J. Harrod. 1994. Systematics of Mexican spruce - revisited. Systematic Botany 19: 47-59. (14) M.P. Frankis, editor for this page on 6-Jan-1999. (15) Vidakovik 1991. See also: | |
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