Picea mariana

Picea mariana, the black spruce, is a North American species of spruce tree in the pine family. It is widespread across Canada, found in all 10 provinces and all 3 Arctic territories. Its range extends into northern parts of the United States: in Alaska, the Great Lakes region, and the upper Northeast. It is a frequent part of the biome known as taiga or boreal forest.[3][4][5][6][7]

Picea mariana
Stand of black spruce near Inuvik, Northwest Territories, Canada
Scientific classification
Kingdom: Plantae
Clade: Tracheophytes
Division: Pinophyta
Class: Pinopsida
Order: Pinales
Family: Pinaceae
Genus: Picea
Species:
P. mariana
Binomial name
Picea mariana
(Mill.) Britton, Sterns & Poggenburg
Synonyms[2]

The Latin specific epithet mariana means “of the Virgin Mary”.[8]

Description
Needles and cones

P. mariana is a slow-growing, small upright evergreen coniferous tree (rarely a shrub), having a straight trunk with little taper, a scruffy habit, and a narrow, pointed crown of short, compact, drooping branches with upturned tips. Through much of its range it averages 5–15 m (15–50 ft) tall with a trunk 15–50 cm (6–20 in) diameter at maturity, though occasional specimens can reach 30 m (98 ft) tall and 60 cm (24 in) diameter. The bark is thin, scaly, and grayish brown. The leaves are needle-like, 6–15 mm (1⁄4–9⁄16 in) long, stiff, four-sided, dark bluish green on the upper sides, paler glaucous green below. The cones are the smallest of all of the spruces, 1.5–4 cm (1⁄2–1 1⁄2 in) long and 1–2 cm (1⁄2–3⁄4 in) broad, spindle-shaped to nearly round, dark purple ripening red-brown, produced in dense clusters in the upper crown, opening at maturity but persisting for several years.[3][4]

Natural hybridization occurs regularly with the closely related P. rubens (red spruce), and very rarely with P. glauca (white spruce).[3]

It differs from P. glauca in having a dense cover of small hairs on the bark of young branch tips, an often darker reddish-brown bark, shorter needles, smaller and rounder cones, and a preference for wetter lowland areas. Numerous differences in details of its needle and pollen morphology also exist but require careful microscopic examination to detect. From true firs, such as Abies balsamea (balsam fir), it differs in having pendulous cones, persistent woody leaf-bases, and four-angled needles, arranged all round the shoots.

Due to the large difference between heartwood and sapwood moisture content, it is easy to distinguish these two wood characteristics in ultrasound images,[9] which are widely used as a nondestructive technique to assess the internal condition of the tree and avoid useless log breakdown.

Older taxonomic synonyms include A. mariana, P. brevifolia, or P. nigra.

Ecology

Growth varies with site quality. In swamp and muskeg it shows progressively slower growth rates from the edges toward the centre. The roots are shallow and wide spreading, resulting in susceptibility to windthrow. In the northern part of its range, ice pruned asymmetric black spruce are often seen with diminished foliage on the windward side.[10] Tilted trees colloquially called "drunken trees" are associated with thawing of permafrost.[3][11]

In the southern portion of its range it is found primarily on wet organic soils, but farther north its abundance on uplands increases. In the Great Lakes region it is most abundant in peat bogs and swamps, also on transitional sites between peatlands and uplands. In these areas it is rare on uplands, except in isolated areas of northern Minnesota and the Upper Peninsula of Michigan.

Black spruce taiga, Copper River, Alaska

Most stands are even-aged due to frequent fire intervals in black spruce forests. It commonly grows in pure stands on organic soils and in mixed stands on mineral soils. It is tolerant of nutrient-poor soils, and is commonly found on poorly drained acidic peatlands. It is considered a climax species over most of its range; however, some ecologists question whether black spruce forests truly attain climax because fires usually occur at 50 to 150 year intervals, while "stable" conditions may not be attained for several hundred years.[3]

The frequent fire return interval, a natural fire ecology, perpetuates numerous successional communities. Throughout boreal North America, Betula papyrifera (paper birch) and Populus tremuloides (quaking aspen) are successional hardwoods that frequently invade burns in black spruce. Black spruce typically seeds in promptly after fire, and with the continued absence of fire, eventually dominates the hardwoods.

Black spruce is a pioneer that invades the sphagnum mat in filled-lake bogs, though often preceded slightly by Larix laricina (tamarack). Black spruce frequently out-competes shade-intolerant tamarack in the course of bog succession. [12] However, as the peat soil is gradually elevated by the accumulation of organic matter, and the fertility of the site improves, balsam fir and northern white cedar (Thuja occidentalis) eventually replace black spruce and tamarack. On drier sites following fires, black spruce can take over stands of faster growing jack pine (Pinus banksiana) by virtue of its ability to grow in partially shaded conditions which inhibit pine seedlings.[13] But black spruce seedlings are themselves intolerant to the low light and low moisture conditions under mature spruce stands. Balsam fir and northern white cedar, both more understory-tolerant species with deeper taproots, survive and eventually succeed the spruce in the absence of fire. [14]

The spruce budworm, a moth larva, causes defoliation, which kills trees if it occurs several years in a row, though black spruce is less susceptible than white spruce or balsam fir. Trees most at risk are those growing with balsam fir and white spruce.[15]

Cultivation

Numerous cultivars have been selected for use in parks and gardens. The cultivar P. mariana 'Nana' is a dwarf form which has gained the Royal Horticultural Society's Award of Garden Merit.[16][17]

Uses and symbolism

Black spruce is the provincial tree of Newfoundland and Labrador.

The timber is of low value due to the small size of the trees, but it is an important source of pulpwood and the primary source of it in Canada.[18] Fast-food chopsticks are often made from black spruce.[5]

However, it is increasingly being used for making cross laminated timber by companies such as Nordic Structures, which allows the high strength due to the tight growth rings to be assembled into larger timbers.[19]

Along with red spruce, it has also been used to make spruce gum and beer.[20]

References
  1. "Picea mariana". IUCN Red List of Threatened Species. Retrieved 26 April 2018.
  2. "Picea mariana". World Checklist of Selected Plant Families (WCSP). Royal Botanic Gardens, Kew – via The Plant List.
  3. Farjon, A. (1990). Pinaceae. Drawings and Descriptions of the Genera. Koeltz Scientific Books. ISBN 3-87429-298-3..
  4. Rushforth, K. (1987). Conifers. Helm. ISBN 0-7470-2801-X.
  5. Earle, Christopher J., ed. (2018). "Picea mariana". The Gymnosperm Database.
  6. Taylor, Ronald J. (1993). "Picea mariana". In Flora of North America Editorial Committee (ed.). Flora of North America North of Mexico (FNA). 2. New York and Oxford – via eFloras.org, Missouri Botanical Garden, St. Louis, MO & Harvard University Herbaria, Cambridge, MA.
  7. "Picea mariana". County-level distribution map from the North American Plant Atlas (NAPA). Biota of North America Program (BONAP). 2014.
  8. Harrison, Lorraine (2012). RHS Latin for Gardeners. United Kingdom: Mitchell Beazley. ISBN 978-1845337315.
  9. Wei, Q.; Chui, Y. H.; Leblon, B.; Zhang, S. Y. (2009). "Identification of selected internal wood characteristics in computed tomography images of black spruce: A comparison study". Journal of Wood Science. 55 (3): 175. doi:10.1007/s10086-008-1013-1. S2CID 135727845.
  10. Hogan, C. Michael (2008). Stromberg, Nicklas (ed.). "Black Spruce: Picea mariana". GlobalTwitcher.com. Archived from the original on 2011-10-05.
  11. Kokelj, S.V.; Burn, C.R. (2003). "'Drunken forest' and near-surface ground ice in Mackenzie Delta, Northwest Territories, Canada". In Marcia Phillips; Sarah Springman; Lukas Arenson (eds.). Proceedings of the 8th Int'l Conf. on Permafrost (PDF). Rotterdam: A.A. Balkema. ISBN 9058095827. Retrieved 2 April 2013.
  12. Conway, V.M (1949). "The bogs of central Minnesota". Ecological Monographs. 19 (2): 173–206. doi:10.2307/1948637. JSTOR 1948637.
  13. Kozlowski, T.T.; Ahlgren, C.E. (1974). Fire and Ecosystems. Cambridge Massachusetts: Academic Press. p. 542. ISBN 9780124242555.
  14. Bloomberg, W.J. (1950). "Fire and spruce". Forestry Chronicle. 26 (2): 157. doi:10.5558/tfc26157-2.
  15. "Forest Pest Fact Sheet" (PDF). Saskatchewan Ministry of Environment. Retrieved 11 November 2017.
  16. "Picea mariana 'Nana' AGM". Royal Horticultural Society. Retrieved 2020-04-17.
  17. "AGM Plants - Ornamental" (PDF). Royal Horticultural Society. July 2017. p. 78. Retrieved 25 April 2018.
  18. Powers, R.F.; Adams, M.B.; Joslin, J.D.; Fisk, J.N. (2005). "Non-Boreal Coniferous Forests of North America". In Andersson, F. (ed.). Coniferous Forests (1st ed.). Amsterdam [u.a].: Elsevier. p. 271. ISBN 978-0-444-81627-6.
  19. "BLACK SPRUCE'S UNIQUE FIBER". Chantiers Chibougamou. Retrieved 31 October 2015.
  20. Little, Elbert L. (1980). The Audubon Society Field Guide to North American Trees: Eastern Region. New York: Knopf. p. 284. ISBN 0-394-50760-6.

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